Precipitation trend increases the contribution of dry reduced nitrogen deposition

Abstract

Abstract Given the leveling off in oxidized nitrogen emissions around the world, the atmospheric deposition of reduced nitrogen (NH x = NH 3 + NH 4 + ) has become progressively critical, especially dry deposition, which presents great threats to plant growth. A combination of historical deposition data of measured wet NH x and modeled dry NH x in China suggests that dry NH x deposition has been increasing substantially (4.50% yr −1 , p < 0.05) since 1980. Here, chemical transport model (WRF-EMEP) results indicate that variation in NH 3 emissions is not a dominant factor resulting in the continually increasing trends of dry NH x deposition, while climate change-induced trends in precipitation patterns with less frequent light rain and more frequent consecutive rain events (with ≥2 consecutive rainy days) contribute to the increase in dry NH x deposition. This will continue to shift NH x deposition from wet to dry form at a rate of 0.12 and 0.23% yr −1 ( p < 0.05) for the period of 2030–2100 in China under the RCP4.5 and RCP8.5 scenarios, respectively. Further analysis for North America and Europe demonstrates results similar to China, with a consistent increase in the contribution of dry NH x deposition driven by changing precipitation patterns from ~30% to ~35%. Our findings, therefore, uncover the change of precipitation patterns has an increasing influence on the shifting of NH x deposition from wet to dry form in the Northern Hemisphere and highlight the need to shift from total NH x deposition-based control strategies to more stringent NH 3 emission controls targeting dry NH x deposition in order to mitigate the potential negative ecological impacts.