Tag Archives: salt

Humanity is making everything saltier around us, and it’s hurting the environment (and our infrastructure)

Road salts, applied to sidewalks, streets, and highways to melt out snow and ice, represent a serious and growing global threat to freshwater supplies and public health, a new paper reports.

Image via Pixabay.

Cold winters make for dangerous roads, and salt has long been used as a tool to de-ice roads. Since it’s a natural product, it was assumed that such procedures wouldn’t cause harm to the environment. A new paper, however, says they do. Salt used for de-icing can negatively impact public health and freshwater sources, it explains, through the chemicals it leeches into the environment.

Salting the wound

“We used to think about adding salts as not much of a problem,” said Sujay Kaushal, a professor in UMD’s Department of Geology and Earth System Science Interdisciplinary Center and lead author of the study. “We thought we put it on the roads in winter and it gets washed away, but we realized that it stuck around and accumulated.”

“Now we’re looking into both the acute exposure risks and the long-term health, environmental, and infrastructure risks of all these chemical cocktails that result from adding salts to the environment, and we’re saying, ‘This is becoming one of the most serious threats to our freshwater supply.’ And it’s happening in many places we look in the United States and around the world.”

Weather-related car accidents claim thousands of lives globally every year, and the application of salt on roads is an important tool in our arsenal towards saving as many as possible. Salt is sometimes also used as a fertilizer on crop fields, and a host of other purposes.

But this salt eventually finds its way into the environment and accumulates, creating a growing global threat.

Previous work by Kaushal’s team found that salt in the wild can interact with soils and man-made infrastructure, drawing out a cocktail of chemicals including metal and radioactive compounds. They called this cascading process the Freshwater Salinization Syndrome (FSS), and found that it can lead to contaminated drinking water sources, impact public health, agriculture, infrastructure, wildlife health, and ecosystem stability.

The current paper explores how the Freshwater Salinization Syndrome impacts human health and the environment. The findings point to freshwater supplies facing serious threats from this syndrome on a local, regional, and global level. The team calls on officials to improve the management of salt usage, and to better regulate it, in order to protect these sources. The team explains that the effects of the FSS is a threat on par with acid rains or biodiversity loss.

For the study, they compared data from freshwater monitoring stations around the world and reviewed studies on the subject, finding a general increase in chloride levels all across the planet. Chloride is a main component in many types of salt like table salt (sodium chloride) or calcium chloride, which is commonly used for de-icing roads. Judging by data from specific regions of interest, the team says we’re seeing a 30-year trend of growing salinity levels; they note the Passaic River, New Jersey and a 100-mile-plus stretch of the Potomac River, which supplies drinking water to Washington, D.C., as areas affected by this trend.

Leeching out

The most important sources of human-related salt in the Northeastern U.S. is road salts, the team explains. Other important sources include sewage leaks and discharges, water softeners, agricultural fertilizers, and fracking brines. Indirect sources of salt in freshwater include road, bridge, and building weathering — salts leech out of limestone, concrete, or gypsum — and ammonium-based fertilizers used in urban or agricultural settings. Sea-level rise can also lead to saltwater intrusion.

Chemicals released from all these sources harm both anthropic and natural environments. For example, changes in environmental salt levels can allow invasive, salt-tolerant species to take over a stream. These compounds can change the microflora in soil and water, which can lead to even more changes, as bacterial communities underpin the health of whole ecosystems. For built environments, salts can lead to corrosion in roadways and broader infrastructure. This can lead to the leaching of heavy metals in drinking water, as was the case in Flint, Michigan.

“I am greatly surprised by the increasing scope and intensity of these problems as highlighted from our studies,” said study co-author Gene E. Likens, founding president emeritus of the Cary Institute of Ecosystem Studies and a distinguished research professor at the University of Connecticut.

“Increased salinization of surface waters is becoming a major environmental problem in many places in the world.”

For now, the team explains, there are still a lot of unknowns. Exactly how these higher salinity levels will impact the environment is still poorly understood. Furthermore, every body of water presents its own conditions and unique management issues in regards to salt. The best way to go about fixing these issues is to treat salt the same way we do nutrient loads: look at all the different sources on a watershed-ecosystem level and prioritize regulation accordingly, the team explains. Sadly, they also note that work has been done to create technological solutions to nutrient runoff, but similar methods do not exist for salt.

“Ultimately, we need regulation at the higher levels, and we’re still lacking adequate protection of local jurisdictions and water supplies,” Kaushal said. “We have made dramatic improvements to acid rain and air quality, and we’re trying to address climate change this way.”

“What we need here is a much better understanding of the complicated effects of added salts and regulations based on that. This can allow us to avert a really difficult future for freshwater supplies.”

The paper “Freshwater salinization syndrome: from emerging global problem to managing risks” has been published in the journal Biogeochemistry.

Ancient 2,500-year-old mural depicts exchange of salt as a commodity

At the ancient Maya site of Calakmul in Mexico’s Yucatan Peninsula, archaeologists have found a striking 2,500-year-old mural depicting an exchange of salt between a vendor and a buyer. It is the earliest record of salt as a commodity.

The mural was found at Calakmul, a UNESCO World Heritage site in the Yucatan Peninsula in Mexico. Credit: Rogelio Valencia, Proyecto Arqueológico Calakmul.

Salt has always been an important resource across the ancient world. As far back as 6050 BC, salt has occupied a central role for countless civilizations from China to Egypt.  It served as currency at various times and places, and it has been the cause of bitter warfare.

In addition to its very practical role, salt has also played a vital part in religious rituals in many cultures, symbolizing purity. It is one of the most effective and most widely used of all food preservatives, which is why salt — also referred to as “white gold” — has always had crucial importance economically.

Although we now see salt as a cheap food ingredient, its rich history still touches our daily lives in more ways than we realize. The word “salary”, for instance, is derived from the word “sal”, the Latin word for salt. That’s because in ancient times, salt was so valuable that soldiers in the Roman army were sometimes paid with salt instead of hard currency. This monthly allowance was called “salarium”.

It’s no wonder to learn that salt occupied a central economic role among the ancient Maya as well. Archaeologists headed by Heather McKillop from Louisiana State University recently documented an ancient mural from Calakmul in which a salt vendor is shown handing out a salt cake wrapped in leaves to another person. The latter is holding a large spoon over a basket.

The salt was transported by canoe up the river. Credit: Heather McKillop, LSU.

Since 2004, Mckillop has uncovered a wealth of archaeological evidence related to ancient Maya salt trade networks. These include the remnants of ‘salt kitchens’ — buildings made of pole and thatch that had been submerged and preserved in the saltwater lagoons of the mangrove forests in Belize. 

The Maya would use these spots to extract salt by boiling brine in pots over fires. So far, the researchers have mapped 70 sites that comprise an extensive network of rooms and buildings known as the Paynes Creek Salt Works.

This must have been an industrial-scale operation, as the archaeologists have identified 4,042 submerged architectural wooden posts, a canoe, an oar, a high-quality jadeite tool, stone tools used to salt fish and meat, and hundreds of pieces of pottery.

Fragment of pottery that was used thousands of years ago to boil brine and extract salt. Credit: Heather McKillop, LSU.

Alongside this recently described mural, this evidence suggests that salt cakes were transported in canoes along the coast and up rivers in southern Belize, the researchers wrote in the Journal of Anthropological Archaeology.

“I think the ancient Maya who worked here were producer-vendors and they would take the salt by canoe up the river. They were making large quantities of salt, much more than they needed for their immediate families. This was their living,” said McKillop in a statement.

Two of McKillop’s students even replicated some of the ancient Maya pottery using a 3d printer based on scans taken in Belize of some of the hundreds of pieces of pottery investigated at the site. This confirmed that the ceramic jars in which the Maya boiled the brine were standardized in volume.

“Produced as homogeneous units, salt may have been used as money in exchanges,” McKillop said.

Dwarf planet Ceres is an ocean world with liquid water beneath the surface

Astronomers have called Ceres many things: the largest object in the asteroid belt; a dwarf planet; a cold, barren rock. But ‘ocean world’ is not something they would have even considered — until very recently.

This animation shows dwarf planet Ceres as seen by NASA’s Dawn. The map overlaid at right gives scientists hints about Ceres’ internal structure from gravity measurements. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres lies within the asteroid belt between Mars and Jupiter. First considered to be a planet in the 19th century, it is now known to be an asteroid, and classed as a dwarf planet, like Pluto.

Now, a flurry of studies forces us to rethink Ceres once again, as astronomers report evidence indicative of a salty ocean beneath its surface.

“We can now say that Ceres is a sort of ocean world, as are some of Saturn’s and Jupiter’s moons,” Maria Cristina De Sanctis, from Rome’s Istituto Nazionale di Astrofisica and one of the study authors, told AFP.

De Sanctis and colleagues analyzed images sent from NASA’s robotic Dawn spacecraft, which entered orbit around Ceres in 2015. As Dawn approached Ceres, it offered an unprecedented glimpse into the planetoid, showing impact craters and signs of cryovolcanic activity (volcanism that erupts frozen water, ammonia, or methane, instead of molten rock). Now, researchers also analyzed infrared images, which showed the presence of a rock called hydrohalite.

A fracture system inside the rim of the Occator Crater, where the new studies found evidence of water. Image credits: NASA.

As the name implies (hydro=water, halite=rock salt), hydrohalite is a mineral that forms in salty waters and has until now only been observed on Earth. The deposit seems to have built up during the last two million years, which is extremely recent in geologic history, suggesting that the processes behind it are still very much active. In other words, it seems that brine is still ascending from the planet’s interior, a “smoking gun” for liquid water.

“That material is unstable on Ceres’ surface, and hence must have been emplaced very recently,” said co-authors Julie Castillo-Rogez, from the California Institute of Technology’s Jet Propulsion Laboratory.

Another published paper found evidence of cryovolcanism that started around 9 million years ago and lasted for several million years, also indicative of a deep brine source. Gravity data and thermal modeling also imply an extensive deep brine reservoir beneath the Ceresian surface.

A crater on Ceres in enhanced color. Image credits: NASA.

In a separate paper, researchers used remote sensing to analyze the crust of Ceres, finding evidence of density and rheological variations, which are also consistent with a liquid ocean under the surface. Whether or not this is still an active ocean or just a remnant of one is unclear.

This finding could have massive implication for the field of astrobiology. Not only does Ceres (a seemingly dull object in the asteroid belt) feature liquid water beneath its surface, shielded from radiation — but it also features salt.

According to De Sanctis, the ingredients of life seem to be lining up nicely on Ceres.

“The material found on Ceres is extremely important in terms of astrobiology,” she said.

“We know that these minerals are all essential for the emergence of life.”

Journal References:

  • C. A. Raymond et al. Impact-driven mobilization of deep crustal brines on dwarf planet Ceres, Nature Astronomy (2020). DOI: 10.1038/s41550-020-1168-2
  • A. Nathues et al. Recent cryovolcanic activity at Occator crater on Ceres, Nature Astronomy (2020). DOI: 10.1038/s41550-020-1146-8
  • R. S. Park et al. Evidence of non-uniform crust of Ceres from Dawn’s high-resolution gravity data, Nature Astronomy (2020). DOI: 10.1038/s41550-020-1019-1
  • M. C. De Sanctis et al. Fresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluids, Nature Astronomy (2020). DOI: 10.1038/s41550-020-1138-8
  • B. E. Schmidt et al. Post-impact cryo-hydrologic formation of small mounds and hills in Ceres’s Occator crater, Nature Geoscience (2020). DOI: 10.1038/s41561-020-0581-6

Why is the ocean salty?

Every time you bathe in the sea, you have geology to thank for the extra buoyancy that salty water provides. Large-scale geological processes bring salt into the oceans and then recycle it deep into the planet. The short answer to ‘why is the ocean salty’ sounds something like this:

Salts eroded from rocks and soil are carried by rivers into the oceans, where salt accumulates. Another source of salts comes from hydrothermal vents, deep down on the surface of the ocean floor. We say “salts” — because the oceans carry several types of salts, not just what we call table salt.

But the longer answer (that follows below) is so much more interesting.

Image credits: Olia Nayda.

In the beginning there was saltiness

As it is so often the case in geology, our story begins with rocks and dirt, and we have to go back in time — a lot. Billions of years ago, during a period called the Archean, our planet was a very different environment than it is today. The atmosphere was different, the landscape was different, but as far as ocean saltiness goes, there may have been more similarities than differences.

Geologists look at ancient rocks that preserved ancient water (and therefore, its ancient salinity); one such study found that Earth’s Archean oceans may have been ~1.2 times saltier than they are today.

At first glance, this sounds pretty weird. Since salt in the seas and oceans is brought in by river runoff and erosion, the salts hadn’t yet had time to accumulate in Earth’s earliest days. So what’s going on?

It is believed that while the very first primeval oceans were less salty than they are today, our oceans have had a significant salinity for billions of years. Although rivers hadn’t had sufficient time to dissolve salts and carry them to oceans, this salinity was driven by the oceanic melting of briny rocks called evaporites, and potentially volcanic activity. It is in this water that the first life forms on Earth emerged and started evolving.

“The ions that were put there long ago have managed to stick around,” says Galen McKinley, a UW-Madison professor of atmospheric and oceanic sciences. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”

The ancient salinity of oceans is still an area of active research with many unknowns. But while we don’t fully understand what’s going on with the ancient oceans, we have a much better understanding of what drives salinity today.

So how do the oceans get salty today?

Salinity map of the world’s oceans. Scale is in parts per thousand. Image credits: NASA.

Oceans today have an average of 3.5% salinity. In other words, 3.5% of the ocean’s weight is made of dissolved salts. Most, but not all of that is sodium chloride (what we call ‘salt‘ in day to day life). Around 10% of the salt ions come from different minerals.

At first glance, 3.5% may not seem that much, but we forget that around 70% of our planet is covered in oceans. If we took all the salt in the ocean and spread it evenly over the land surface, it would form a layer over 500 feet (166 meters) thick — a whopping 40-story building’s height of salt covering the entire planet’s landmass. That’s how much 3.5% means in this particular case.

All these salts come from rocks. Rocks are laden with ionic elements such as sodium, chlorine, and potassium. Much of this material was spewed as magma by massive volcanic eruptions and can form salts under the right conditions.

Because it is slightly acidic, rainwater can slowly dissolve, erode rocks. As it does so, it gathers ions that make up salts and transfers them to streams and rivers. We consider rivers to be “freshwater”, but that’s not technically true: all rivers have some salt dissolved in them, but because they flow, they don’t really accumulate it. Rivers are agents for carrying salts, but they don’t store salts themselves.

The main culprit for why oceans are salty: rivers. Image credits: Jon Flobrant.

Rivers constantly gather more salts, but they constantly push it downstream. Influx from precipitation also ensures that the salt concentration doesn’t increase over time.

Meanwhile, the oceans have no outlet, and while they also have currents and are still dynamic, they have nowhere to send the salts to, so they just accumulate more and more salt. Which leads us to an interesting question.

So, are the oceans getting saltier?

Bodies of water can be classified by their salt content.

No, not really. Although it’s hard to say whether oceans will get saltier in geologic time (ie millions of years), ocean salinity remains generally constant, despite the constant influx of salt.

“Ions aren’t being removed or supplied in an appreciable amount,” says McKinley. “The removal and sources that do exist are so small and the reservoir is so large that those ions just stay in the water.” For example, she says, “Each year, runoff from the land adds only 0.00005 percent of total ocean salts.”

A part of the minerals is used by animals and plants in the water and another part of salts becomes sediment on the ocean floor and is not dissolved. However, the main reason why oceans aren’t getting saltier is once more geological.

The surface of our planet is in a constant state of movement — we call this plate tectonics. Essentially, the Earth’s crust is split into rigid plates that move around at a speed of a few centimeters per year. Some are buried through the process of subduction, taking with them the minerals and salts into the mantle, where they are recycled. The movement of tectonic plates constantly recirculates material from and into the mantle.

Schematic of subduction (and some other associated processes). Image credits: K. D. Schroeder.

With these processes, along with the flow of freshwater, precipitation, and a number of other processes, the salinity of the Earth’s oceans remains relatively stable — the oceans have a stable input and output of salts.

But isolated bodies of water, however, can become extra salty.

Why some lakes are freshwater, and some are *very* salty

Lakes are temporary storage areas for water, and most lakes tend to be freshwater. Rivers and streams bring water to lakes just like they do to oceans, so then why don’t lakes get salty?

Well, lakes are usually only wide depressions in a river channel — there is a water input and a water output, water flows in and it flows out. This is called an open lake, and open lakes are essentially a buffer for rivers, where water accumulates, but it still flows in and out, without salts accumulating. Many lakes are also the result of chaotic drainage patterns left over from the last Ice Age, which makes them very recent in geologic time and salts have not had the time to accumulate.

Beautiful glacial lakes such as this one are the remains of Ice Age melting. Image credits: K. D. Schroeder.

But when a lake has no water output and it has had enough time to accumulate salts, it can become very salty. This is called a closed lake, and closed lakes (and seas) can be very salty, much more so than the planetary oceans. They accumulate salts and lose water through evaporation, which increases the concentration of salts. Closed lakes are pretty much always saline.

We mentioned that world oceans are 3.5% salt on average. The Mediterranean Sea has a salinity of 3.8%. The Red Sea has some areas with salinity over 4%, and Mono Lake in California can have a salinity of 8.8%. But even that isn’t close to the saltiest lakes on Earth. Great Salt Lake in Utah has a whopping salinity of 31.7%, and the pink lake Retba in Senegal, where people have mined salt for centuries, has a salinity that reaches 40% in some points. The saltiest lake we know of is called Gaet’ale Pond — a small, hot pond with a salinity of 43% — a testament to just how saline these isolated bodies of water can get.

Worker digging the salt in Lake Retba. Image in public domain.

It’s important to note that lakes are not stable geologically, and many tend to not last in geologic time. Some of the world’s biggest lakes are drying up, both as a natural process and due to rising temperatures, drought, and agricultural irrigation.

Salt can also come from below

Hydrothermal vent. Image credits: NOAA.

We’ve mentioned that rock weathering and dissolving makes oceans salty, but there is another process: hydrothermal vents.

A part of the ocean water seeps deeper into the crust, becomes hotter, dissolves some minerals, and then flows back into the ocean through these vents. The hot water brings large amounts of minerals and salts. It’s not a one-way process — some of the salts react with the rocks and are removed from seawater, but this process also contributes to salinization.

Lastly, underwater volcanic eruptions can also bring salts from the deeper parts to the surface, affecting the salt content of oceans.

Is that bowl of ramen giving you a stroke? A study says ‘maybe’

Ramen could be bad for you, according to a new study.

Image via Pixabay.

Researchers at the Jichi Medical University report that the high level of sodium (salt) in ramen could increase your chances of having a stroke. The team tracked various types of restaurants and health data among different regions of Japan and found that areas with a high number of ramen shops record more deaths by stroke than other Japanese prefectures, but not more heart attacks. Do note that the study established a correlation between the two (i.e. there are more stroke victims in areas with more ramen shops), but not a causative one.

Noodles to die for

“The prevalence of ramen restaurants in Japanese prefectures has a significant correlation with the stroke mortality rate,” the study concluded.

Ramen is, in short, delicious. This broth-and-noodle mix served in a bowl is a Japanese take on a traditional Chinese dish, and is enjoyed by people around the world.

However, not all may be right amidst the flavors. The team aimed to examine the relationship between diet and certain health concerns, chiefly that of the risk of stroke, in Japan. They compared various types of cuisine and different regions of the country to health data and restaurant prevalence.

Four categories of restaurants were considered: ramen, fast food, French or Italian, and udon or soba (two other types of noodle dishes). For health data, the team obtained age- and sex-adjusted stroke and heart attack mortality rates for each Japanese prefecture from a 2017 national study.

All in all, prefectures with a high number of ramen shops tend to see more stroke deaths than other Japanese prefectures, but not more heart attacks. Tohoku (in the northern Kanto region) and the southern regions of the Kyushu island have higher stroke mortality than other areas in Japan, the team reports. The Kinki region and southern Kanto region have low stroke mortality rates, they add. This distribution correlates very well to the prevalence of ramen restaurants, the team explains. They believe the high sodium content of the dish helps promote stroke.

Take the findings with a pinch of salt (pun intended). The team couldn’t obtain detailed information on the diets of the stroke victims used in the study, so they can’t tell whether ramen is the culprit. What the team found here is a correlation, meaning they can tell that areas with more ramen shops experience more deaths by stroke, but not that they cause those deaths.

The authors highlight that ramen is a popular, traditional dish, and as such is enjoyed in homes, not just restaurants — which they could not factor into this study. Furthermore, instant ramen is a popular snack all over the world but was also not part of the study as it’s virtually impossible to track its sales. On the other hand, ramen has many components such as soy, tonkotsu (a broth made from simmered pork marrow or bone), miso, and salt; more research is needed to establish which of these components (if any) have a strong bearing on stroke risk. Side dishes usually served with ramen, such as dumplings and rice, further compound the issue.

“These side dishes may include confounding nutritional factors,” the scientists write.

The paper “Ramen restaurant prevalence is associated with stroke mortality in Japan: an ecological study” has been published in the Nutrition Journal.

European satellites track climate shifts using ocean salinity

New research from the European Space Agency (ESA) Climate Change Initiative is offering new insight into sea-surface salinity across the world. The data will help researchers better estimate the effects of climatic shifts on the world’s oceans.

Global sea-surface salinity maps from ESA’s Climate Change Initiative.
Image credits European Space Agency.

Ocean water is salty — but these salt levels aren’t the same everywhere. This saltiness is a key variable in the Earth’s climate systems, as it’s the product of multiple different factors (additions of freshwater from rivers, rain, glaciers or ice sheets, or on the removal of water by evaporation). Understanding how salinity changes over time and distance can help us better understand (and predict) man-made climate change. Now, thanks to the ESA’s efforts, we can monitor it from space.

Salt-o-meter

“The project aims to make a significant improvement to the quality and length of the datasets available for monitoring sea-surface salinity across the globe,” says Susanne Mecklenburg, head of ESA’s Climate Office.

“We are keen to see this new dataset used and tested in a variety of applications, particularly to improve our understanding of the fundamental role that oceans have in climate.”

The ongoing project from the ESA’s Climate Change Initiative (CCI) has produced the most complete dataset of sea-surface salinity around the world to date. The CCI aims to generate accurate and long-term datasets pertaining to 21 Essential Climate Variables set out under the United Nations Framework Convention on Climate Change and the Intergovernmental Panel on Climate Change.

Sea-surface salinity maps can be used to monitor natural water cycles, evaporation rates, and ocean circulation. These processes are central elements of the climate system of today as they help transport heat, nutrients and carbon around the planet. Unusual salinity levels can also indicate that extreme climate events, such as El Niño, are about to start.

Such measurements have been taken before — they indicate that ever since the 1950s, salty areas around the world are becoming saltier, while freshwater areas are becoming fresher. However, there has always been a measure of debate over these findings, as they relied on scientific ships trawling the oceans to read salinity, which provides relatively poor accuracy (as they’re quite slow to move around). Using satellites to capture a global snapshot would give us a much better idea of what’s happening.

The team behind the project, Jacqueline Boutin of LOCEAN (Laboratory of Oceanography and Climatology) and Nicolas Reul of IFREMER (French Research Institute for the Exploitation of the Sea) pooled together data from three satellite missions to create a dataset spanning nine years, with maps generated on a weekly and monthly basis.

The team measured brightness temperature as a proxy for sea-surface salinity using microwave sensors onboard the SMOS, Aquarius, and Soil Moisture Active Passive satellite missions.

“Monitoring salinity from space helps to resolve spatial and temporal scales that are poorly sampled by in situ platforms that make direct observations, and fills gaps in the observing system,” says Dr. Boutin.

“By combining and comparing measurements between the different sensors, [we improved] the precision of maps of sea-surface salinity by roughly 30%.”

Ocean–atmosphere exchanges around the world are driven by winds and exchanges between surface and subsurface ocean water, the team explains. These later ones are powered by changes in water density, a product of both temperature and salinity (salty water is denser than freshwater). In the deep ocean, density variations are the main driver for the movement of water. Studying changes in salinity, the team explains, can thus help better model ocean-atmosphere exchanges, and the behavior of deeper ocean layers — both of which will allow us to better estimate climate shifts in the future.

The team is currently working with climate scientists to compare the new dataset with in situ observations and with the output from salinity models.

The dataset is freely available for download from the CCI Open Data Portal.

Scientists develop battery that taps into ‘blue energy’ formed when freshwater meets seawater

Deer Island wastewater treatment plant. Credit: Wikimedia Commons.

In coastal regions where freshwater mixes with seawater, a salt gradient is formed. Scientists at Stanford University have now found a way to tap into the energy of this gradient, which is sometimes called “blue energy”. The authors envision a future where their technology could be used to make waste-water treatment facilities energy independent.

Energy from moving salt

For every cubic meter of freshwater that mixes with seawater, about .65 kilowatt-hours of energy is produced — just about enough to power the average American home for 30 minutes. All around the world, coastal wastewater treatment plants have access to about 18 gigawatts of blue energy, or the equivalent of powering 1,700 U.S. homes for an entire year.

Other groups have previously succeeded in harnessing blue energy but the Stanford group is the first to employ an electrochemical battery rather than pressure or membranes.

“Blue energy is an immense and untapped source of renewable energy,” said study coauthor Kristian Dubrawski, a postdoctoral scholar in civil and environmental engineering at Stanford. “Our battery is a major step toward practically capturing that energy without membranes, moving parts or energy input.”

The group was led by Craig Criddle, a professor of civil and environmental engineering, who has a lifetime of experience developing technologies for wastewater treatment. The battery developed by Criddle and colleagues first releases sodium and chloride ions from the device’s electrodes into a solution, making a current flow between the electrodes. When wastewater effluent and seawater are combined, the electrodes reincorporate sodium and chloride ions, reversing the current flow. According to the researchers, energy is recovered during both freshwater and seawater flushes. There is no initial energy investment required, nor is there any need for charging. In other words, this is a passive energy system that doesn’t require any input of energy.

The power output is relatively low per electrode area, but the authors highlight the fact that their technology’s strong point lies in its simplicity. The blue energy capturing device doesn’t have any moving parts and passively generates energy without the need for any external instruments to control voltage or charge. The electrodes are manufactured from Prussian Blue, a material widely used in medicine, which costs less than a $1 per kilogram, as well as polypyrrole, which costs less than $3 a kilogram.

If the technology is scaled, it should prove robust enough to provide energy for any coastal treatment plant in the world. Any surplus production could then be diverted to other nearby applications, such as desalination plants. A scaled version that could someday be used in a municipal wastewater plant is currently being designed by the Stanford researchers.

“It is a scientifically elegant solution to a complex problem,” Dubrawski said. “It needs to be tested at scale, and it doesn’t address the challenge of tapping blue energy at the global scale – rivers running into the ocean – but it is a good starting point that could spur these advances.”

The findings appeared in the American Chemical Society’s ACS Omega.

Saltwater electrolysis.

New process can make hydrogen fuel out of seawater without destroying the devices

Researchers from Stanford University have developed a process to make hydrogen fuel using only electrodes, solar power, and saltwater from the San Francisco Bay.

Saltwater electrolysis.

A prototype device used solar energy to create hydrogen fuel from seawater.
Image credits Yun Kuang et al., (2019), PNAS.

Hydrogen fuel holds a lot of promise as the energy source of the future. It’s clean, doesn’t emit anything, it’s energy-dense, and it’s beyond abundant — if only we were able to develop a way of retrieving the element from its chemical constraints. A new paper describes a way to do just that, starting from saltwater.

Salt of the water

Why is this news? Well, it simply comes down to quantities — the Earth has a lot of saltwater, but not very much fresh water. Methods of producing hydrogen fuel from the latter have already been developed, but the fact of the matter is that fresh water is valuable. We need it to drink, we need it to wash, we need it to grow our crops and, as our planet’s population increases, we run a very real risk of not having enough water for everyone. So it doesn’t make sense to use it for energy — we need it elsewhere.

“You need so much hydrogen [to power our cities and economies that] it is not conceivable to use purified water,” said Hongjie Dai, J.G. Jackson and C.J. Wood professor in chemistry at Stanford and co-senior author on the paper. “We barely have enough water for our current needs in California.”

Salty water, in contrast, is plentiful — which also means cheap. There’s enough of it that we can turn it into hydrogen without upsetting the natural balance of Earth’s ecosystems too much. Hydrogen fuel also doesn’t emit carbon dioxide as it ‘burns’, only water. Given our current troubles with man-made climate change and habitat destruction, both are very appealing qualities.

Saltwater does, however, come with a major drawback. It’s not that hard to split water into hydrogen and oxygen, and we’ve known how to do it for a long time now. Just take a power source, connect two wires to and place their other end (or some electrodes if you want to be fancy about it) in water. Turn the power on, and you’ll get hydrogen bubbles at the negative end (cathode), and oxygen bubbles at the positive end (anode). This process is called electrolysis.

So far so good. But, if you try the same thing with saltwater, the chloride ions in salt (salt is a mix of chloride and sodium atoms) will corrode the anode and break down the system pretty quickly. Dai and his team wanted to find a way to stop those components from breaking down in the process.

Their approach was to coat the anode in several layers of negatively-charged material, which would repeal chloride, thus prolonging the useable life of the electrolysis rig. They layered nickel-iron hydroxide on top of nickel sulfide, over a nickel foam core. The nickel foam acts as a conductor, carrying electricity from the power source, while the nickel-iron hydroxide performs the electrolysis proper, separating water into oxygen and hydrogen.

As this happens, the nickel sulfide becomes negatively charged, protecting the anode. Just as the negative ends of two magnets push against one another, the negatively charged layer repels chloride and prevents it from reaching the core metal. Without the coating, the anode only works for around 12 hours in seawater, according to Michael Kenney, a graduate student in the Dai lab and co-lead author on the paper.

“The whole electrode falls apart into a crumble,” Kenney said. “But with this layer, it is able to go more than a thousand hours.”

Another bonus this coating brings to the table is that it allows for electrolysis to be performed at much higher currents. Previous efforts to split seawater had to use low current, as higher values promote corrosion. The team was able to conduct up to 10 times more electricity through their multi-layer device, which helps it generate hydrogen faster. Dai says they likely “set a record on the current to split seawater.” By eliminating the corrosive effect of salt, the team was able to use the same currents as those in devices that use purified water.

The team conducted most of their tests in controlled laboratory conditions, where they could regulate the amount of electricity entering the system. But, they also designed a solar-powered demonstration machine that produced hydrogen and oxygen gas from seawater collected from San Francisco Bay. Dai says the team pointed the way forward but will leave it up to manufacturers to scale and mass produce the design.

“One could just use these elements in existing electrolyzer systems and that could be pretty quick,” he adds. “It’s not like starting from zero — it’s more like starting from 80 or 90 percent.”

In the future, the technology could be used to generate breathable oxygen for divers or submarines while also providing power. And, perhaps, it could also be used in space exploration to limit the need for water purification systems — at least as far as power and oxygen are concerned.

The paper ” Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels” has been published in the journal Proceedings of the National Academy of Sciences.

Chinese food is too salty and should have label warnings, study calls

An analysis of more than 150 Chinese dishes found that many of them contain disturbingly high amounts of salt — some being five times more salty than a Big Mac. Study authors call on policymakers to make health labeling mandatory.

Mapo Tofu is one of my favorites. Image credits: Guilhem Vellut.

Sweet sour pork, Kung Pao chicken, Mapo tofu — these staples of Chinese cuisine (and many others) have become increasingly popular in the Western World. With over 22 million takeaways eaten every week in the UK alone, understanding the health impacts of these foods is a significant concern. With this in mind, Action on Salt, a group concerned with salt and its effects on health, supported by 25 expert scientific members, analyzed 150 Chinese foods.

They found that both supermarket and takeaway Chinese food dishes were laden with salt, with the worst offenders having five times more salt than even the Big Mac. Out of the tested foods (all in the UK), 97% contained a hefty 2g of salt or more per dish. Over half (58%) contained more than 3g of salt per dish — half of the recommended daily intake in the UK, 6g of salt (the World Health Organization recommends no more than 5g of salt). The study reads:

“Chinese meals should carry a health warning on packaging and menus after a new survey based at the Wolfson Institute, Barts & The London, Queen Mary University of London has exposed the astonishing and harmful amounts of salt found in both Chinese takeaways and Chinese ready meals sold by some of the UK’s biggest supermarkets. The group of leading experts is now calling on Public Health England (PHE) to get tough on setting new salt targets, making front of pack labelling mandatory and put warning labels on menus for dishes high in salt.”

Image credits: Dubravko Sorić.

Main courses (such as beef in black bean sauce) topped the list, but accompanying dishes such as rice, spring rolls or prawn crackers can also add to the total salt quantity. Soy sauce, a staple of Chinese cuisine, is extremely salty, but sweet sauces and foods can also contain impressive amounts of salt (which is often used as a flavor enhancer).

According to the Center for Disease Control and Prevention (CDC) and the WHP (and really, any health organization), excess sodium (‘table salt’ is a sodium salt) can increase blood pressure and the risk of heart disease and stroke.

“Salt is the forgotten killer as it puts up our blood pressure, leading to tens of thousands of unnecessary strokes, heart failure and heart attacks every year,” said Graham MacGregor, the chairman of Action on Salt and a professor of cardiovascular medicine at Queen Mary University of London.

The findings are concerning, and Action on Salt says that the first step towards tackling this issue is labeling — having a visual warning could help to make people more aware of how much salt they are consuming.

Results have not been peer-reviewed.

Having a healthy diet doesn’t offset high salt consumption

A new study contradicts the belief that eating a healthy, but salty diet, is alright. Even if you eat a lot of fruits and vegetables, you may still suffer the negative effects of high salt consumption.

Processed foods are one of the main culprits for the extra salt in our meals.

It was previously thought that vitamins and minerals in fruits and vegetables affect blood vessels in a way that allows them to lower blood pressure, but this new research, which analyzed the diet and overall health of over 4,000 people, found that that’s not really the case.

An international team of researchers assessed concentrations of sodium and potassium in the urine samples of 4,680 people, aged 40-59, from the USA, UK, Japan, and China. The study participants were tracked over four days, during which they gave urine samples two times. Sodium is one of the two elements of salt and has been linked to increased blood pressure, while potassium, which is commonly found in legumes and vegetables, has been associated with lower blood pressure. Researchers also tracked the volunteers’ intake of over 80 nutrients that may be linked to low blood pressure, including vitamin C, fibers, and omega-3 fatty acids.

Researchers were expecting to find an inverse correlation between sodium and potassium, but they found that no matter how many fruits and veggies people ate, high salt intake was associated with high blood pressure; on average, an additional 7g (1.2 teaspoons) of salt above the average intake was associated with an increase in systolic blood pressure of 3.7 mmHg.

Dr. Queenie Chan, joint-lead author of the research from the School of Public Health at Imperial College London, said that this can be extremely important, especially as high blood pressure affects between 16 and 37% of the population globally. A 2010 study found that hypertension is a factor in 18% of all deaths (9.4 million globally), with processed foods being one of the main culprits.

“We currently have a global epidemic of high salt intake – and high blood pressure. This research shows there are no cheats when it comes to reducing blood pressure. Having a low salt diet is key – even if your diet is otherwise healthy and balanced.”

“As a large amount of the salt in our diet comes from processed food, we are urging food manufacturers to take steps to reduce salt in their products,” she added.

However, researchers emphasize that they only tracked volunteers for four days, so they only recorded a snapshot of their lives. In the future, they plan to expand a similar study on a longer period of time, and with more participants.

Lifestyle changes can be extremely effective in reducing high blood pressure. Eating a healthy diet and having an active lifestyle is extremely important in reducing sodium blood levels. Extra pounds and high blood pressure go hand in hand. Alcohol and cigarettes can also contribute to raising blood pressure.

The results have been published in the journal Hypertension.

Europa TectPun.

Europa’s tectonics might be powered by salt, could sustain life on the moon

New research suggests that Europa’s icy shell may exhibit tectonic systems similar to those on Earth. This would have major implications for live developing on the moon.

Europa TectPun.

Image credits Alex Micu / ZME Science; free to use with attribution.

A team of Brown University researchers used computer modeling to show that subduction — the “sinking” of tectonic plates — is physically possible on Jupiter’s freezing moon, Europa. The result support earlier work that identified regions on the moon’s ice shell which seem to be expanding in a fashion similar to what we see down here on Earth. Overall, the study fleshes our understanding of tectonic processes in general, those on Europa in particular, and raises some very exciting possibilities regarding life in its undersurface waters.

Tectonics on the rocks

“What we show is that under reasonable assumptions for conditions on Europa, subduction could be happening there as well, which is really exciting,” says Brandon Johnson, assistant professor in Brown’s Department of Earth, Environmental and Planetary Sciences and a lead author of the study.

We’ve found several different types of tectonic systems in the solar system, from Venus’ hickey-like coronae to Mercury’s contraction-powered tectonics. Back down on our own plastic-laden corner of the Universe, subduction is powered chiefly by differences in temperature. The crust, Earth’s outer layer, is formed of plates floating on top of the mantle (an ocean of fluid, molten rock). Being solid and cold, these plates are denser than the material in the mantle — this bulk provides the negative buoyancy that pulls crustal slabs into the mantle.

A few years ago, Europa was also shown to maintain its own tectonic processes. Despite having an icy, rather than rocky, crust, there was evidence that processes very similar to Earth’s subduction were going on. But we didn’t have any idea why. We have reason to believe that the moon’s interior is kept warm by the gravitational tug of its massive host, Jupiter. This means that Europa’s ice shell is made up of two layers, Johnson says — a thin outer cover of very cold ice sitting atop a slightly warmer, convecting layer. So the working hypothesis was that surface slabs would break off and sink through the mushy ice below.

Europa poster.

The layers of Europa.
Image credits Kelvinsong / Wikimedia.

There is one major hiccup with that hypothesis, however: as the slabs pushed down into the warmer ice below, they would quickly warm to match its temperature. When that happened, the slab would have the same density of the surrounding ice — so they wouldn’t sink.

Johnson and his team developed a subduction model that could be maintained across Europa regardless of these temperature differences. What they used is salt. A difference in salinity between the two ice layers would provide the density gap needed for a slab to subduct.

“Adding salt to an ice slab would be like adding little weights to it because salt is denser than ice,” he explains. “So rather than temperature, we show that differences in the salt content of the ice could enable subduction to happen on Europa.”

Evidence in support of a salinity difference in Europa’s layers come from the moon’s occasional water upwellings — a process similar to magma upwellings here on Earth. Such events leave behind salty traces on the crust.

Sink 4 life

Plumes Europa.

Composite image shows a suspected plume of material erupting two years apart from the same location on Europa.
Image credits NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center.

The results help patch up our understanding of Europa’s tectonics and help us get a better understanding of how Earth’s tectonic processes work. It also bolsters the case for a habitable(-ish, at least) ocean on the moon by pointing to an undersurface ocean that’s dynamic enough to sustain tectonics.

Perhaps most excitedly, it teases with the possibility of organisms eeking out a living below the frozen surface.

“If indeed there’s life in that ocean, subduction offers a way to supply the nutrients it would need,” Johnson adds.

So what do tectonic processes have to do with life? Well, life (as we understand it) needs a lot of different building blocks including hydrogen, oxygen, nitrogen, phosphorous, and sulfur. These are usually found in ample supply in planets, but they’re not evenly spread around. Even worse, life consumes these basic nutrients wherever it happens to pop up.

Tectonics brings a lot of matter motility to the scene. By churning everything while sinking and moving about, tectonic plates make sure elements are recirculated vertically throughout a planetary system, ensuring there’s always something tasty for organisms to munch on when new plates form.

It’s by no means a “there’s life on Europa, you guys” find, but some important conditions are there. Which makes NASA’s upcoming mission to Europa just that much more exciting.

The paper “Porosity and salt content determine if subduction can occur in Europa’s ice shell” has been published in the Journal of Geophysical Research: Planets.

High salt intake doubles the risk of heart failure

If you thought salt isn’t so bad… well, it is.

Image credits: National Institute of Korean Language.

A new study studied the connection between salt consumption and heart failure risk. It was a follow-up study of 4,630 randomly selected men and women aged 25 to 64 from Finland. Participants filled in a self-evaluation questionnaire, and researchers measured their weight and height. They also took blood and urine samples and measured blood pressure, measuring the salt in the urine.

The study was followed up after 12 years, and salt intake was then compared with the risk of a heart accident. A clear correlation was observed between the two.

“High salt (sodium chloride) intake is one of the major causes of high blood pressure and an independent risk factor for coronary heart disease (CHD) and stroke,” said Prof Pekka Jousilahti, research professor at the National Institute for Health and Welfare, Helsinki, Finland. “In addition to CHD and stroke, heart failure is one of the major cardiovascular diseases in Europe and globally but the role of high salt intake in its development is unknown.”

This was a “correlation not causation” study, but this isn’t nearly the first time salt has been found to contribute to the overall risk of heart failure. In addition to other adverse effects, excessive salt consumption has long been associated with hypertension and cardiovascular disease. The heart just doesn’t seem to like salt all that much. Two times more salt, two times more heart risk failure.

“People who consumed more than 13.7 grams of salt daily had a two times higher risk of heart failure compared to those consuming less than 6.8 grams,” he continued. “The optimal daily salt intake is probably even lower than 6.8 grams. The World Health Organization recommends a maximum of 5 grams per day and the physiological need is 2 to 3 grams per day.”

In most populations, average consumption is significantly higher than the limit, largely due to processed foods, most of which contain a lot of salt.

Processed foods contain most of the salt we consume, researchers warn. Image via Wikipedia.

So it’s best to keep total salt consumption under 5 grams a day, which is less than one teaspoon. But it’s not just about adding less salt to our food — studies show that about 80% of salt intake is in processed foods, and that’s much harder to reduce. The most straightforward way would be to reduce processed foods altogether — as numerous studies have shown them to be largely detrimental to human health.

The results were presented at the European Society of Cardiology (ESC) 2017 Congress and have not yet been peer reviewed.

Does seeing this make you thirsty? Credit: Pixabay.

Almost everything we know about salt may be wrong. Eating salt actually makes you less thirsty but hungrier

Does seeing this make you thirsty? Credit: Pixabay.

Does seeing this make you thirsty? Credit: Pixabay.

Some people can’t enjoy a meal without salt. Indeed, ancient Romans thought it was indispensable and used it as a trading medium on par with coins. The warriors serving the empire were actually paid with a handful of salt per day. Roman historian Pliny the Elder, stated as an aside in his Natural History’s discussion of sea water, that “In Rome…the soldier’s pay was originally salt and the word salary derives from it.” Today salt is so cheap, you could literally stock tens of tons it with an average San Francisco monthly wage.

But despite all its appeal going back millennia and its ubiquitous nature, we sure got a lot of things wrong about salt. A salty meal, be it fries and chicken or tortilla chips will warrant a drink or two to wash off all that saltiness. According to American and German researchers, salt actually makes you less thirsty. Not immediately, but within 24 hours, the salt intake will cause our bodies to produce water, a process akin how the camel draws water from its hump!

Dr. Jens Titze, now a kidney specialist at Vanderbilt University, has been studying human physiology in extreme environments for more than a quarter century. In 1991, he was attending a European space program course when data from a simulated 28-day mission caught his eye. He saw how the urine volumes went up and down in a seven-day cycle, something which went against what he was taught in med school since such a cycle shouldn’t exist.

Sodium — which forms an irresistible pair with chlorine which we all know and love as salt — is an essential mineral in living things for a variety of functions. In the human body, sodium levels have to be maintained at a certain level otherwise all sort of health problems can happen. Drinking excessive amounts of water, for instance, can drastically lower blood sodium, leading to a condition called hyponatremia. Many athletes have died from it. 

The consensus among doctors is that when we eat salt, we get thirsty, and the excess water dilutes the sodium in the blood to acceptable levels. This thinking is intuitive and simple to grasp. It might also be very much wrong.

When Russia made a 135-day simulation of life on the Mir space station in 1994, Titze found himself in Moscow studying the crew members’ urine patterns and these were affected by salt consumption. Again, he came across something striking: an inexplicable 28-day rhythm in the amount of sodium the bodies of the crew retained that didn’t seem to be linked to the amount of urine they produced. What should have happened was a predictable rise and fall of the sodium level in line with the volume of urine. Instead, the sodium seemed to be retained in the body.

Crew members try out their spacesuits during a simulated mission to Mars at the Russian Academy of Sciences’ Institute of Biomedical Problems (IBMP) in Moscow. Their training included a controlled feeding study led by Vanderbilt University’s Jens Titze, M.D., to measure the long-term effects of a high-salt diet. (Photo courtesy of the IBMP and the German Aerospace Center)

Crew members try out their spacesuits during a simulated mission to Mars at the Russian Academy of Sciences’ Institute of Biomedical Problems (IBMP) in Moscow. Their training included a controlled feeding study led by Vanderbilt University’s Jens Titze, M.D., to measure the long-term effects of a high-salt diet. (Photo courtesy of the IBMP and the German Aerospace Center)

A decade later, between 2009 and 2011, his team studied four men during a 105-day pre-flight phase and six others during the first 205 days of a 520-day phase that simulated a full-length manned mission to Mars and back. In the 105-day simulation, the cosmonauts ate a diet consisting of 12 grams of salt daily, which was gradually cut down to nine grams daily, then six grams daily, each over a period of 28 days. In the 520-day simulation, the cosmonauts ate an additional cycle of 12 grams of salt daily. This time, the researchers were careful to measure every crumb of food the crew ate and measured daily urine to the last drop.

Again the seemingly erroneous pattern in urine volumes persisted but the other markers seem to follow the textbook: eating more salt led to more salt excretion; the amount of sodium in the blood stayed constant and the volume of urine increased.

But then, on a closer look at fluid intake, there was the real shocker: the more salt the crew consumed, the less water they drank. Additionally, the crew complained they were always hungry on the high-salt diet though the meals matched each crew members nutritious needs exactly. The ‘hunger games’ were gone on the low-salt diet.

When Titze’s team experimented with mice on salt diets, he found the animals drank less water the more salt was introduced into their diets.

The only sensible explanation is the body compensated by producing water when salt intake creased. The human body isn’t a fountain or spring but we do retain a lot of water in our tissue. Salt triggers the production of glucocorticoid hormones which influence metabolism and immune function. When the hormones were in high concentration, these break down fat and muscle in the body to free up water. Of course, this comes at a cost: energy, which explains why the mice on a high-salt diet ate 25 percent more food.

Of course, doctors have always known that a body deprived of water will source it from the body itself by breaking it down from the tissue. Much in the same way, a camel traveling through the desert that has no water will break down the fat in its hump. But the fact that this happens from salt intake alone is a huge revelation.

By this point, you might call this ‘fake news’ seeing how we all know chips or pretzels make us very thirsty. In reality,  Dr. Mark Zeidel, a nephrologist at Harvard Medical School who wrote an editorial accompanying the published paper, says we get thirsty because salt-detecting neurons in the mouth stimulate an urge to drink. This urge might have nothing to do with the body’s actual need for water.

In light of these recent findings, a high-salt diet might make people vulnerable to diabetes, obesity, osteoporosis, and cardiovascular disease, all conditions linked to high glucocorticoid levels.

“We have always focused on the role of salt in arterial hypertension. Our findings suggest that there is much more to know — a high salt intake may predispose to metabolic syndrome,” Titze said in a statement.

Whatever’s the case the findings published in The Journal of Clinical Investigation topple many established notions about how sodium interacts with the human body. The consequences could be far reaching and, as is always the case with controversial research, the results will have to be replicated before academics are ready to accept them.

The method could supply 40% of the world's electricity needs. Credit: Pixabay.

Innovative tech generates electricity from where rivers meet the ocean

Researchers at Penn State University used a hybrid technology to produce electrical power at the transition zone from seawater to freshwater on coasts. It relies on the difference in saline concentration between the two water mediums to generate power. The team estimates the locked energy potential in such a medium is enough to meet 40% of the world’s electricity demand.

The method could supply 40% of the world's electricity needs. Credit: Pixabay.

The method could supply 40% of the world’s electricity needs. Credit: Pixabay.

Making electricity from varying saline concentrations in water or a saline gradient isn’t exactly a new idea. In 1973, Prof. Sidney Loeb from Ben-Gurion University of the Negev, Israel, invented such a power generation method called pressure retarded osmosis (PRO). This technique selectively allows water to pass through a semi-permeable membrane littered with tiny holes but blocks salt. The resulting osmotic pressure is what generates power by driving a turbine.

Since Loeb introduced PRO, it has become the most common and best technology for generating energy from a saline energy gradient. The process can be run in reverse to desalinate saltwater too.

The problem with PRO, however, is that in time the transport membrane becomes unusable after bacteria congregate as biofilms on its surface or particles get stuck in the holes. Moreover, PRO isn’t very good when the water is super-salty.

Then there’s reverse electrodialysis (RED), which was invented by the same Prof. Loeb in 1977. RED uses an electrochemical gradient instead of a difference in the electric field to develop voltages across ion-exchange membranes. These membranes only allow either positively charged or negatively charged ions to pass through them. Essentially, the difference in ion concentration between either chloride or sodium ions is what drives power generation. Unlike PRO, the ion-exchange membranes in RED do not require water to flow through them so there’s no fouling risk. The downside is that RED isn’t capable of generating large amounts of power.

Finally, there’s a third method called capacitive mixing (CapMix). Relatively recently develop, CapMix involves capturing energy from the voltage that naturally unfolds when two identical electrodes are sequentially exposed to two different kinds of water of varying salinity — freshwater vs saltwater, for instance. Just like RED, CapMix doesn’t generate impressive amounts of voltage.

Two in one

Looking to revamp saline gradient energy power generation, a team at Penn State combined RED and CapMix to create a hybrid tech that generates unprecedented power in an electrochemical flow cell.

Inside the flow cell, there are two channels separated by an anion-exchange membrane. Inside each of the two channels, the researchers placed a copper hexacyanoferrate electrode with a graphite foil acting as a current collector. The cell is completely sealed by two end plates with nuts and bolts.

One of the channels is fed with synthetic seawater while the other is fed with synthetic freshwater. Periodically switching the water’s flow paths allowed the cell to recharge and further produce power.

“By combining the two methods, they end up giving you a lot more energy,” said Christopher Gorski, assistant professor in environmental engineering at Penn State.

“There are two things going on here that make it work,” said Gorski. “The first is you have the salt going to the electrodes. The second is you have the chloride transferring across the membrane. Since both of these processes generate a voltage, you end up developing a combined voltage at the electrodes and across the membrane.”

During experiments, the team varied the type of membrane used as well as the salinity difference and recorded the open-circuit cell voltages while two solutions were fed at a rate of 15 milliliters per minute. This is how they learned that:

  • stacking multiple cells influences electricity generation;
  • the method generates unprecedently high peak power densities of 12.6 watts/m^2 compared to 2.9 watts/m^2 for RED and 9.2 watts/m^2 for PRO. That’s 36% more power density than PRO and all without fouling problems.

“What we’ve shown is that we can bring that power density up to what people have reported for pressure retarded osmosis and to a value much higher than what has been reported if you use these two processes alone,” Gorski said.

In a time where solar and wind are growing rapidly to the point they’re becoming recognized as ‘mainstream’ as opposed to ‘alternative’, it’s refreshing to hear about other, novel means of generating renewable energy. In the face of climate change and growing demand for energy, there is never one solution to our problems but a mix.

“Pursuing renewable energy sources is important,” Gorski said. “If we can do carbon neutral energy, we should.”

This salty lake beneath the sea just kills everything inside it

They call it the “Jacuzzi of Despair” and rarely has a name been so fitting.

Image credits: EVNautilus/YouTube.

The ocean can be a very dangerous and surprising place, and sometimes, the water itself is the enemy. Deep beneath the Gulf of Mexico, at about 3,300 feet below the surface (1 km), there’s a lake. Yes, you read that right, there’s a lake in the ocean. But this isn’t just any lake — it has a crazy high salt content, as well as dissolved methane. This means that any critter unfortunate enough to fall into it is killed almost immediately.

Erik Cordes, associate professor of biology at Temple University, has discovered and studied the pool.

“It was one of the most amazing things in the deep sea. You go down into the bottom of the ocean and you are looking at a lake or a river flowing. It feels like you are not on this world”, Cordes told Seeker.

The lake measures 100 feet in circumference and is about 12 feet deep. It was likely formed when fissures in the seafloor allowed the water to seep in and mix with salt. Then, as it interacted with the methane, it started to flow again to the surface, maintaining its salt content. The brine, now four or five times saltier than the water around it, is so dense that it stays on the bottom forming the lake.

Cordes first identified the lake in 2014, when he and his colleagues were studying the area with a remotely operated underwater robot called Hercules. They were tipped by the numerous carcasses around the lake.

“We were able to see the first opening of a canyon,” Cordes says. “We kept up this steep slope and it opened up and we saw all these mud flows. We got closer and we saw the brine falling over this wall like a dam. It was this beautiful pool of red white and black colors.”

You might be asking what sea creatures are doing around the lake anyway – if anything, you’d expect them to keep as far away as possible. The thing is, some creatures do survive in the lake: specially adapted bacteria, shrimp and tube worms thrive in these hellish conditions. There’s a chance that these creatures might attract others, which then succumb to the Jacuzzi of Despair.

Another interesting point is that extraterrestrial life might survive in conditions similar to this. Places like Europa might very well host underwater life in places with high salinity and organic substances.

“There’s a lot of people looking at these extreme habitats on Earth as models for what we might discover when we go to other planets,” Cordes says. “The technology development in the deep sea is definitely going to be applied to the worlds beyond our own.”

This isn’t the world’s only underwater lake by any chance. There are several underwater lakes, especially in the Gulf of Mexico region; they’ve got their own shores and all. The brine water of these lakes actually hosts unique wildlife, creating an absolutely amazing environment.

New electric fork simulates a salty flavor by shocking your tongue

Adding extra-salt may make food tastier, but it can also has a negative effect on your health. With that in mind, Japanese researchers have invented a fork that creates a salty taste in your mouth at the press of a button, by releasing an electrical current which stimulates the tongue.

The “electric flavoring fork” generates a salty or sour taste. The metal part of the handle is held in the palm, and the button is pressed by the thumb. It can be used for about six hours per charge. The prototype is not water-proof, but presumably will be in the future.

Salt has long been associated with blood pressure, an increased risk of heart disease and even a risk of stomach cancer. It’s clear that many people are eating too much salt, but no one really likes bland food. There may be a middle way.

The prototype fork, which was built from just $24 worth of electronics, creates the sensation of both salty and sour, and can be adjusted for different intensities. The handle of the fork incorporates a rechargeable battery and electric circuit. When the user inserts the head of the fork into the mouth with food while pressing a button on the handle, a certain level of electric current is applied to the tongue. The fork was developed based on the “electric flavoring” technology being researched by Hiromi Nakamura at Rekimoto Lab, Interfaculty Initiative in Information Studies, the University of Tokyo. It’s based on a technology which stimulates the tongue to make it feel salty or sour, the same “electric test” being used to see if some parts of the tongue are fully functional or not.

At this moment, it’s not clear whether or not the fork will become widely available. For now, the prototype was prepared for “No Salt Restaurant,” a project to offer a salt-free full-course meal.

Study hints at a form of bacterial collective memory

We tend to believe that memory is a luxury reserved only for animals with brains, such as humans and other higher organisms. But even simple lifeforms such as bacteria can employ a form of memory, albeit relatively short in duration.

Image via wikimedia

Image via wikimedia

Memory doesn’t work in bacteria as it does in humans — shocking, I know. But while they can’t relive the days of their youth or their (probably) exciting first division, bacteria are able to learn from and increase resistance to past stressors. An example of this phenomena is the salinity-shock; bacteria exposed to moderate levels of salt are able to survive subsequent exposures to much higher, otherwise deadly concentrations of it.

On an individual scale this adaptation is short-lived — after thirty minutes, survival rates drop down to pre-exposure levels. Two ETH Zurich microbiologists, Roland Mathis and Martin Ackermann have now discovered that when entire populations are considered however, the longevity of this phenomena is dramatically increased. They experimented with Caulobacter crescentus, a bacterium pervasive in fresh and sea water.

They placed C. crescentus on little adhesive stalks to fix them on a glass substrate inside eight microfluidic chips; as they divided, the mother cell would remain inside the chip and the daughter would be washed out. Then they reconstructed cell-division cycles and survival probabilities using a technique known as time-lapse microscopy.

Experimental set-up with the bacterium C. crescentus in microfluidic chips: each chip comprises eight channels, with a bacterial population growing in each channel.
Image credits Stephanie Stutz/ETH Zurich

Compared to control cells, individually-exposed bacteria had better survival rates to salt that lasted up to about 30 minutes. But when whole populations were exposed this adaptation lasted for up to two hours, hinting to a kind of bacterial “collective memory.”

The team explains that when a population is exposed to salt, the resulting stress causes all cells to delay their division cycle, synchronizing it throughout the culture — and survival of any individual cell is dependent on what part of the cell cycle it is in at the time of the second exposure.

As a result, a previously exposed population’s sensitivity changes over time. They may become more tolerant to future stress events, but might also become more susceptible to the stressor — it all depends on the state they are in their cycle of division at the time.

“If we understand this collective effect, it may improve our ability to control bacterial populations,” Martin Ackermann comments.

The findings could go a long way in improving our medical knowledge, for example understanding how pathogens develop drug resistance. But it’s also relevant in other fields of science, such as improving bacterial performance in industrial processes and wastewater treatments.

The full paper titled “Response of single bacterial cells to stress gives rise to complex history dependence at the population level” has been published online in the journal Proceedings of the National Academy of Sciences and is available here.

GeoPicture of the Week: Cubic Salt Crystals at Salar de Uyuni, Bolivia

These are perfectly cubical salt crystals, spotted at Salar de Uyuni, the world’s largest salt flat, located in Bolivia.

Image via Imgur.

Each crystal belongs to a specific crystal system – for salt it’s the cubic system. This means that the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals, and this is why we see these extremely straight crystals.

Salar de Uyuni is the legacy of a prehistoric lake that went dry, leaving behind a desert-like, 11,000-sq.-km. landscape of bright-white salt, rock formations and cacti-studded islands. It is covered by a few meters of salt crust, which has an extraordinary flatness.

Scientists find the last vestiges of Martian surface water

Mars is now a cold and dry place, but it wasn’t always like this – the Red Planet used to have a lot of water on its surface. Now, researchers have discovered one of the very last places where (potentially habitable) liquid water existed.

This is a perspective rendering of the Martian chloride deposit.
Credit: LASP / Brian Hynek

Water on Mars exists today almost exclusively as ice, with a small amount present in the atmosphere as vapor. The only place where water ice is visible at the surface is at the north polar ice cap. But even today, we still see clear evidence that the planet was once a wet place. Researchers from the University of Colorado Boulder have identified and analyzed such a place – a salt flat which was once a lake.

Salt flats here on Earth are not especially uncommon. Natural salt pans or salt flats are flat expanses of ground covered with salt and other minerals which usually form when salty water pools evaporate. Based on the surface and apparent thickness of the salt, researchers estimate that the lake was about 8% as salty as Earth’s oceans – which means it was quite hospitable for microbial life.

“By salinity alone, it certainly seems as though this lake would have been habitable throughout much of its existence,” Brian Hynek, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU-Boulder and lead author of the study.

However, other relevant factors for habitability such as acidity were not the scope of the study and were not considered here – in fact, the potential habitability of the lake was not explored at all.

But what’s interesting about this formation is its age: digital terrain mapping and mineralogical analysis of the features surrounding the deposit indicate that the former lake bed is no older than 3.6 billion years ago – which means that it hosted water for a very long time, and was one of the last watery places on Mars.

“This was a long-lived lake, and we were able to put a very good time boundary on its maximum age,” said Hynek, who is also an associate professor in the Department of Geological Sciences at CU-Boulder and director of the CU Center for Astrobiology. “We can be pretty certain that this is one of the last instances of a sizeable lake on Mars.”

Journal Reference:

  1. Brian M. Hynek, Mikki K. Osterloo, Kathryn S. Kierein-Young. Late-stage formation of Martian chloride salts through ponding and evaporation. Geology, 2015; G36895.1 DOI: 10.1130/G36895.1

Revolutionary lamp works 8 hours on 1 glass of salt water

Artificial light is something we take for granted and simply don’t think about – but for some communities, light can be a luxury. In the 7,000 scattered islands of the Philippines, light can be very scarce, and saltwater is abundant. With that in mind, SALt engineers have designed a lamp that runs on salt water.

Image via SALt.

Lipa Aisa Mijena combined her skills as a De La Salle University with her motivation as a member of Greenpeace Philippines to get the lamps in the hands of the most underprivileged communities in the islands. Many rural inhabitants still use candles, paraffin, or battery-operated lamps in their home, which are not only inefficient and unreliable, but can also cause house fires.

[Also Read: Are molten salt reactors the future of renewable energy?]

The SALt lamp uses a solution of one glass of water mixed with two tablespoons of salt – even salt you take from the sea; yep,ocean water can power up the lamp for 8 hours! You can simply fill up some bottles with ocean water and refill the lamp whenever needed – clean light at your disposal. The SALt lamp can last up to a year, if it’s used just a few hours a day. Using SALt lamp 8 hours a day every day will give you an anode lifespan of 6 months.

Oh, and if necessary, you can also charge your smartphone or tablet from the lamp.

Image via SALt.

The product hasn’t been yet released on the market, as confirmed by the product’s Facebook page. It’s still in its testing phase, but should hit the shelves of people in Philippines (and why not, of the world) pretty soon:

“Good day everyone! We have been receiving a lot of emails asking where to buy the lamp. This is to inform you that the lamp is not out in the market yet. We are still in product development stage and will soon get into mass production. Rest assure we will announce here on our facebook page and website upon the launching of our product.”