TITLE:
Chemical Composition and Sources of Rainwater Collected at a Semi-Rural Site in Ya’an, Southwestern China
AUTHORS:
Min Zhao, Li Li, Zhilin Liu, Bin Chen, Jianqiu Huang, Jinwang Cai, Shihuai Deng
KEYWORDS:
Acid Rain; Chemical Composition; Ammonia; Source Apportionment; Ya’an
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.3 No.4,
September
11,
2013
ABSTRACT:
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%. SO42- 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.