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 = NH3 + NH4 +) 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 NHx 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 NH3 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 NHx 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 NH3 emission controls targeting dry NH x deposition in order to mitigate the potential negative ecological impacts.