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Oxygen Loss In Lakes | Earth Wise

January 13, 2023 By EarthWise Leave a Comment

Researchers from Cornell University and Rensselaer Polytechnic Institute have found that the continual warming in the world over the past 25 years has been reducing the amount of oxygen in many lakes.

Data from more than 400 lakes – mostly in the United States – shows that lakes with dissolved oxygen losses strongly outnumber those with gains. Overall, the researchers found that the amount of low oxygen water is increasing by 0.9% to 1.7% per decade on average and the volume of lake water lacking oxygen has increased by more than 50% from 25 years ago.

In the summer, lake surfaces may be about 70 degrees while the lake bottom may be about 40 degrees. The colder water is denser than the warmer water which causes resistance to the layers mixing. It is akin to having oil and vinegar in a cruet. This is known as stratification. The result is that oxygen from the atmosphere is prevented from replenishing dissolved oxygen in deep waters. This is a normal seasonal phenomenon.

However, with winter ending sooner than it used to, seasonal stratification is starting earlier and ending later. As warming continues, it is likely that there will be an increasing number of oxygen-depleted lakes in the future.

Oxygen deprivation in water can lead to hypoxia (low oxygen) and even anoxia (no oxygen), which have negative consequences for fish and other species. Reducing oxygen in lake water can lead to buildup of methane. Nutrients from agricultural runoff, released from unsettled lake sediment, increase the likelihood of harmful algal blooms.

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Warming climate prompts harmful oxygen loss in lakes

Photo, posted June 23, 2010, courtesy of Alexander Acker via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Membrane For Converting Carbon Dioxide | Earth Wise

March 24, 2020 By EarthWise Leave a Comment

Methanol is a valuable chemical used as fuel in the production of countless products. Carbon dioxide is a greenhouse gas that is produced by countless industrial processes. Carbon dioxide can be converted into methanol, which is one way all that CO2 can be put to good use instead of causing harm.

In research recently published in Science, chemical engineers from Rensselaer Polytechnic Institute have developed a process that converts CO2 to methanol in a more efficient way by using a highly effective separation membrane they produced.

The chemical reaction responsible for the transformation of CO2 into methanol also produces water, which severely restricts the continued reaction. The Rensselaer team has found a way to filter out the water as the reaction is happening, without losing other essential gas molecules.

They produced a membrane made up of sodium ions and zeolite crystals that was able to carefully and quickly permeate water through small pores — known as water-conduction nanochannels — without losing gas molecules. The sodium ions effectively only allow water to go through. When water was effectively removed from the process, the team found that the chemical reaction was able to happen very quickly. By removing the water, the equilibrium shifts, which means more CO2 will be converted and more methanol will be produced.

The team is now working to develop a scalable process and a startup company that would allow this membrane to be used commercially to produce high purity methanol. This membrane could also be used to improve a number of other reactions.

In industry there are many reactions limited by water and this RPI membrane could be an important enhancement for many of them.

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Water-Conducting Membrane Allows Carbon Dioxide To Transform into Fuel More Efficiently

Photo courtesy of RPI.

Earth Wise is a production of WAMC Northeast Public Radio.

Lake George Health Report

December 26, 2019 By EarthWise Leave a Comment

The Offshore Chemistry Program, run by the Darrin Fresh Water Institute at RPI, has been monitoring the deep waters of Lake George in New York for 40 years. Lake George, nicknamed the Queen of American Lakes, is famed for the transparency of its water and a new report on the health of the lake reveals that it is doing rather well.

According to the report, although concentrations of chemicals and pollutants like salt and nutrients have increased in the deep waters of Lake George, they are still too low to harm the ecosystem at those depths.

The Offshore Chemistry Program studies the lake as part of a collaboration between RPI, IBM Research, and the FUND for Lake George that is called the Jefferson Project. This long-term commitment provides a wealth of information over time matched by few lake studies in the world.

The recent results show that levels of salt, the nutrient orthophosphate, and chlorophyll have increased substantially over time, but none are yet at a level that will cause harm.

Orthophosphate occurs naturally, but most likely the higher levels are due to improperly functioning septic systems, failing wastewater treatment systems, and stormwater runoff. The orthophosphate most likely triggered the increase in chlorophyll, which probably is associated with increased density of chlorophyll in individual algal cells, rather than an increase in total algal mass in the lake.

Overall, the results demonstrate the continuing resilience of Lake George to a growing array of stressors. In nearly 40 years of human activities, the lake has changed in a number of ways, but the changes have so far been relatively small. With such careful monitoring, we can hope to keep them that way.

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Four Decades of Data Sounds Early Warning on Lake George

Photo, posted September 24, 2009, courtesy of GPA Photo Archive via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.