Researchers are integrating traditional geochemistry with artificial intelligence to forecast the impact of climate warming and population growth on the alkalinity and salt levels in rivers nationwide.
The chemistry of US rivers is changing—and will change further in complex ways in different regions of the country. Scientists are exploring ways to predict future changes in watershed chemistry, which could improve managing them for climate change and community health.
The researchers are combining traditional geochemistry with artificial intelligence to predict how alkalinity (a measure of a solution’s ability to neutralize acids) and salts in rivers around the country could be affected by further climate warming and population growth, according to the new study in Applied Geochemistry.
The research team was led by Tao Wen, an assistant professor in the earth and environmental sciences department (EES) at Syracuse University. Wen also directs the Hydrogeochemistry And eNvironmental Data Sciences (HANDS) and Noble Gases in Earth Systems Tracing (NEST) research laboratories.
An excess of salt can make water undrinkable, increase the cost of treating water, and harm freshwater fish and wildlife.
Past research shows that as salt levels in US rivers have gone up, these waters have also become more alkaline, which can damage water and wastewater treatment and aquatic life. Increased alkalinity is occurring because of rising temperatures and more rainfall. Human activities, such as more people living in certain areas, might also contribute to it.
Yet alkalinity is also beneficial. When river waters are more alkaline, they help draw carbon dioxide out of the atmosphere and limit climate warming over time. However, before rivers can be harnessed for this purpose, researchers must first understand the basic chemistry at play.
Using machine learning models, the Wen team projected how salinity—measured through sodium levels—and alkalinity will change in 226 US rivers between 2040 and 2100 under different climate and human population scenarios.
In northern states, rivers would become less salty because warmer winters mean less salt will be applied on icy roads. However, in the South and West, where people don’t use much road salt, river salinity will likely stay the same. But as these areas get hotter and drier, more salt from the soil might accumulate and wash into waterways.
The study also found that rising temperature can affect alkalinity. In watersheds rich in carbonate rocks, such as limestone, researchers found that alkalinity flux—the product of the natural breakdown of rock minerals—declines when temperatures surpass 10°C (50F). This finding suggests that warming past a certain temperature level could suppress alkalinity in rivers.
However, in watersheds dominated by silicate rocks or organic carbon, higher temperatures accelerate silicate weathering and the decomposition of organic material, leading to increased alkalinity levels. More rainfall can also increase the amount of these chemicals in rivers, but only up to a certain point.
In the future, some watersheds with lower alkalinity could be manipulated to take up additional alkaline from watersheds, allowing rivers to sequester more carbon from the atmosphere.
Here, Wen speaks about his work:
Can human activities affect carbon sequestration in US watersheds?
Yes, both directly and indirectly. The top influences are natural geological features such as carbonate sediment, temperature, and precipitation that affect rock weathering. But humans can modify these natural features to make a difference. When our activities cause more rock to be exposed to water and air, it causes a chemical reaction that allows more carbon dioxide to be sequestered from the air at a faster rate.
How could carbon sequestration be enhanced by human interventions?
There is a process called Enhanced Rock Weathering or ERW. In both the public and private sectors, many practitioners are already using ERW to leverage natural geochemical processes to enhance their ability to remove carbon dioxide from the atmosphere over the long term. To manually enhance that intensity and the rate of the rock weathering, you can grind the rock into smaller particles and spread them on farmland. You expose the rock to the air and water, allowing the rock to react with them and absorb more carbon dioxide from the air.
How can your study help guide this process?
Our study shows that some watersheds will have more room in the future for adding alkalinity to sequester more carbon. One motivation for this study is to build and train a model to make predictions about where such interventions could occur or should be prioritized.
What are your next steps?
Our ultimate goal is to make these predictions for smaller watersheds at a much finer spatial resolution. So, you could have predictions about future alkalinity or salinity for any watershed, even without geochemical data from that watershed.
Source: Syracuse University
