Reservoirs, ditches and rivers around the world are emitting increasing amounts of the powerful greenhouse gas N2O (also known as nitrous oxide). The emission of nitrous oxide is hundreds of times more powerful than carbon dioxide2, has tripled in the last century. Researchers from Utrecht University report this in the scientific journal Environmental science and technology.
The large increase, the researchers write, is mainly due to the increased use of fertilizers and the global growth in the number of dams. These emissions will increase further in the future because more dams are already planned.
Where does laughing gas come from?
laughing gas (n2O) is naturally present in small concentrations in the atmosphere and remains there, just like carbon dioxide2, heat. Because nitrous oxide has a very strong greenhouse effect, scientists say it accounts for about 10 percent of global warming caused by human activity. One gram of nitrous oxide contributes to atmospheric warming as much as 300 grams of carbon dioxide2.
The gas can be produced in different ways: when fossil fuels are burned, but also, for example, because bacteria create or break down nitrates. Nitrate is a nitrogen compound. If more nitrogen is provided, more nitrous oxide can also be produced in this way. The scientists wrote that nitrogen supplies in surface waters doubled in the 20th century.
Simply put, groundwater was not seen as a significant source of nitrous oxide.
The results show that since 1950, when the use of synthetic fertilizers in agriculture and horticulture increased rapidly, nitrous oxide emissions from the same freshwater sources have more than tripled. The increased emissions from groundwater and reservoirs are particularly striking, but ditches and rivers also emit more nitrous oxide. It has been underestimated for a long time.
Why didn’t scientists notice this before? “It is very difficult to correctly measure the production and emission of nitrous oxide from fresh water,” explains researcher Junjie Wang. Few measurements were made over a longer period of time or at the same location. Therefore groundwater was not simply seen as an important source of N2Hey.”
What is the role of cabinets in this story?
The study shows that in addition to fertilizers, reservoirs are also important sources of nitrous oxide emissions. The researchers show that emissions from water reservoirs have increased tenfold over the past 70 years.
The fact that reservoirs in particular contribute to greenhouse gas emissions creates an environmental dilemma. Dams are often built specifically to generate clean electricity using hydroelectric power plants. And unlike coal- or gas-fired power plants, no carbon dioxide is produced2 free. But if the reservoir becomes a source of nitrous oxide emissions, it will still cause climate damage. Based on this study, the researchers cannot determine how the advantages and disadvantages of hydroelectric power plants relate to each other.
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