By Marco Tedesco
Many researchers have monitored the decline in air pollution in response to the restrictions imposed by the pandemic. However, the impact on rivers and seas is still unclear.
“The connection between atmosphere and surface water quality is very tight,” said Dennis Hallema, hydrology expert from North Carolina State University and author of a study recently published in Ecological Processes. “The global map shows a substantial reduction in [atmospheric] nitrogen dioxide concentrations in excess of 30 to 40 percent during the first two weeks of spring compared to the same period last year over large cities such as Paris, London and New York,” continued Hallema. Since air quality affects water quality, the researchers expect to see improvements in water quality.
However, water systems are complex and potential water improvements depend on the level of urbanization of an area, and on the physical characteristics of the soil that filters most of the pollution and where pollutants can be stored for months before pouring into the waterways. A flood or heavy rain can facilitate the sudden release of these substances. For this reason, many scientists believe that water improvements associated with COVID-19 will be localized and short-lived.
This is in accordance with the results recently published in the journal Science of the Total Environment, where the authors show, via satellite data, that the concentration of pollutants in Vembanad Lake, the longest lake in India, decreased by an average of 16 percent compared to the values of the previous year. Similarly, water pollution in San Francisco Bay, California has reduced significantly due to the reduction in traffic, according to experts. The toxic particles emitted by cars, in fact, fall into the surrounding waters, inlets and on the coast for miles.
NASA has also gotten involved by funding new research that aims to use its satellites to understand what the impact of COVID-19 is on the water quality of Long Island Sound, near New York City.
“The impact on atmospheric deposition nitrogen and the resulting changes in coastal aquatic ecology during the pandemic remain unknown,” said Maria Tzortziou, professor at the City College of New York who heads the NASA project. In general, an overabundance of nitrogen and other chemicals and nutrients in the water can cause excessive algae growth. Algae decomposition consumes oxygen, leaving water without oxygen to support life. “This project will help fill a gap in our fundamental understanding of the air-water exchange of nutrients and pollutants and how this affects and is influenced by environmental regulations, socioeconomic policy responses and decision making,” said Tzortziou.
A final aspect concerns plastic. Even if the data do not yet exist in this regard, it is reasonable to expect an increase in the concentrations of microplastics and other substances derived in the waters, due to the increase in the production and use of disposable objects and other plastic-based substances. We hope to be wrong.
After air pollution, the first studies on water quality point in the direction of an improvement resulting from the suspension of human activities. It would be nice to keep this quality of air and water when the pandemic is over. It is possible, but we will have to work hard for it.
Adapted and translated from a piece originally published in La Repubblica.
Marco Tedesco is a research professor at Columbia University’s Lamont-Doherty Earth Observatory.