Author(s)

Min Zhao, Li Li, Zhilin Liu, Bin Chen, Jianqiu Huang, Jinwang Cai, Shihuai Deng

Provincial Key Laboratory of Agricultural Environmental Engineering, College of Resources and Environment, Sichuan Agricultural University, Chengdu, China.

Rain and snow water samples were collected from Sep. 2010 to Jun. 2011 at a semi-rural site in Ya’an, a city located in the rain-belt along the Tibetan Plateau, to characterize the chemical composition and the sources of precipitation. The collected samples were severely acidified with an annual volume-weighted mean (VWM) pH of 4.03 and an annual acid rain frequency of 79%. SO₄^2- and NH₄⁺ were the most abundant ions, followed by Ca²⁺, H⁺, NO₃^-, Cl^-, K⁺, Na⁺, F^- and Mg²⁺. The acidity of samples was predominantly generated by H₂SO₄ and HNO₃, which were neutralized by NH₄⁺ and Ca²⁺ as much as 65%. NH₃ played a major role in neutralizing the acid rain. The average ambient concentration of NH₃ was 174.2 μg/m³ during sampling periods. Different source apportionment methods, including principle component analysis (PCA), enrichment factor (EF), correlation and back-trajectory analysis were used to track the sources of rainwater. The methods suggested that the pollutants in rainwater were from both local and long-distance transport (1:2.2), or they were from anthropogenic actions (86.4%), sea salts (8.1%) and crustal (5.5%) respectively.

Acid Rain; Chemical Composition; Ammonia; Source Apportionment; Ya’an

M. Zhao, L. Li, Z. Liu, B. Chen, J. Huang, J. Cai and S. Deng, "Chemical Composition and Sources of Rainwater Collected at a Semi-Rural Site in Ya’an, Southwestern China," Atmospheric and Climate Sciences, Vol. 3 No. 4, 2013, pp. 486-496. doi: 10.4236/acs.2013.34051.