Nitrate pollution is a big problem, and figuring out where it comes from is key to solving it. Researchers looked at water samples from China's biggest freshwater lake, Poyang Lake, over two years. They used some fancy methods, like isotope models and statistical tools, to trace the sources of nitrates in both groundwater and surface water. Turns out, human activities, like using chemical fertilizers, soil nitrogen, and waste from farms and towns, play a big role. From 2022 to 2023, these sources contributed differently to groundwater and surface water nitrates. For example, in groundwater, fertilizers contributed 16. 6% to 32. 4%, soil nitrogen 26. 0% to 38. 1%, and waste 26. 5% to 48. 2%. In surface water, fertilizers were 38. 8% to 43. 9%, soil nitrogen 37. 6% to 40. 6%, and waste 12. 3% to 18. 6%. The sources and amounts of nitrates in groundwater and surface water were quite different. Things like time of year, how the land is used, population density, and what kind of plants are growing also affected nitrate sources. The study found there's some uncertainty in figuring out exactly where nitrates come from, but this research is a big step forward in understanding and tackling nitrate pollution in large freshwater lakes.

Understanding Nitrate Pollution in China's Largest Lake: A Seasonal Snapshot

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