Forests in northeast China's Qingyuan County have shown a significant decrease in nitrogen deposition over the past decade, according to a study published in the journal Science of The Total Environment. 

Nitrogen deposition occurs when nitrogen compounds in the air settle on land or water. It can come from natural sources, but human activities such as burning fossil fuels and using fertilizers also contribute. While some level of nitrogen is essential for plant growth, too much can disrupt ecosystems. 

In this study, researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences monitored nitrogen levels in the Qingyuan forests between 2014 and 2022. They found a remarkable 55% decrease in total inorganic nitrogen deposition. This included a 60% decrease in ammonium nitrogen deposition, mainly due to reduced agricultural NH₃ emissions, and a 42% decrease in nitrate nitrogen deposition, mainly due to reduced nitrogen oxide emissions from agricultural soils and fossil fuel burning. 

To provide a broader perspective, the researchers examined data from East Asian acid deposition monitoring sites outside of China. These sites are at similar latitudes to Qingyuan county and showed decreases in nitrogen deposition of 14-34%. 

They suggest that this sharp decline in nitrogen deposition within Northeast China is due to several factors. In particular, China has implemented stricter policies to reduce coal consumption, improve vehicle emission controls, and promote more sustainable agricultural practices since 2010. These changes appear to be having a positive impact on atmospheric nitrogen levels. 

The study provides valuable insights for other developing countries and regions in struggling with high levels of nitrogen deposition. It also highlights the potential effectiveness of stricter environmental regulations in addressing air pollution.