Wet and dry nitrogen deposition in the central Sichuan Basin of China

Reactive nitrogen (Nr) plays a key role in the atmospheric environment and its deposition has induced large negative impacts on ecosystem health and services. Five-year continuous in-situ monitoring of N deposition, including wet (total nitrogen (wTN), total dissolved nitrogen (wTDN), dissolved organic nitrogen (wDON), ammonium nitrogen (wAN) and nitrate nitrogen (wNN)) and dry (DNH3, DHNO3, (D)pN(4)(+), (D)pNO(3)(-) and DNO2) deposition, had been conducted since August 2008 to December 2013 (wet) and May 2011 to December 2013 (dry) in Yan-ting, China, a typical agricultural area in the central Sichuan Basin. Mean annual total N deposition from 2011 to 2013 was 30.8 kg N ha(-1) yr(-1), and speculated that of 2009 and 2010 was averaged 28.2 kg N ha(-1) yr(-1), respectively. Wet and dry N deposition accounted for 76.3% and 23.7% of annual N deposition, respectively. Reduced N ((w)AN, DNH3 and (D)pNH(4)(+)) was 1.7 times of oxidized N (wNN, DHNO3, DNO2 and DPNO3-) which accounted for 50.9% and 30.3% of TN, respectively. Maximum loadings of all N forms of wet deposition, gaseous NH3, HNO3 and particulate NH4+ in dry deposition occurred in summer and minimum loadings in winter. Whether monthly, seasonal or annual averaged, dissolved N accounted for more than 70% of the total. N deposition in the central Sichuan Basin increased during the sampling period, especially that of ammonium compounds, and has become a serious threat to local aquatic ecosystems, the surrounding forest and other natural or semi-natural ecosystems in the upper reaches of the Yangtze River. (C) 2016 Elsevier Ltd. All rights reserved.