Rapid industrial development and agricultural production emit large quantities of NO_x (NO + NO₂) and NH₃ to the atmosphere. After a series of chemical transformations and physical transport processes in the atmosphere, NH₃ and NO_x are removed through dry deposition and wet scavenging and deposited on the Earth’s surface.

These nitrogen (N) inputs to ecosystems can affect the structure and function of an ecosystem, such as plant growth, biological diversity, balance of greenhouse gases, etc. Therefore, understanding the spatiotemporal patterns of N deposition is essential for evaluating its ecological effects. However, uncertainty exists in the assessment of global N deposition, particularly in dry deposition.

Researchers from Institute of Geographic Sciences and Natural Resources Research, CAS developed a new method to evaluate global inorganic N dry deposition. They used NO₂ satellite measurement and ground measurements from 555 monitoring sites to establish empirical models.

Compared to previous methods, geostatistical methods and model simulation, this new method used in their study has two advantages. First, this method has a simpler structure and requires fewer parameters, which reduces computation time and decreases uncertainty associated with the multiple data sources. Second, this method can conveniently provide continuous results for trend analysis of dry deposition.

Based on this method, the researchers determined the global patterns and trends in dry deposition fluxes from 2005-2014 directly from ground- and space-based data.

The results show that the total annual amount of global inorganic N deposition was 34.26 Tg N. In the past decade, the western United States and Eurasia, particularly eastern China, experienced the largest increases in dry deposition, whereas the eastern United States, Western Europe, and Japan experienced clear decreases through control of NO_x and NH₃ emissions. These findings provide a scientific background for policy-makers and future research into global changes.