Air concentrations and wet deposition of major inorganic ions at five non-urban sites in China, 2001-2003

Air and precipitation measurements at five sites were undertaken from 2001 to 2003 in four different provinces in China, as part of the acid rain monitoring program IMPACTS. The sites were located in Tie Shan Ping (TSP) in Chongqing, Cai Jia Tang (CJT) in Hunan, Lei Gong Shan (LGS) and Liu Chong Guan (LCG) in Guizhou and Li Xi He (LXH) in Guangdong. The site characteristics are quite varied with TSP and LCG located relatively near big cites while the three others are situated in more regionally representative areas. The distances to urban centres are reflected in the air pollution concentrations, with annual average concentrations of SO, ranging from 0.5 to above 40 mu g S m(-3). The main components in the airborne particles are (NH4)(2)SO4 and CaSO4. Reduced nitrogen has a considerably higher concentration level than oxidised nitrogen, reflecting the high ammonia emissions from agriculture. The gas/particle ratio for the nitrogen compounds is about 1: 1 at all the three intensive measurement sites, while for sulphur it varies from 2.5 to 0.5 depending on the distance to the emission sources. As in air, the predominant ions in precipitation are sulphate, calcium and ammonium. The volume weighted annual concentration of sulphate ranges from about 70 mu eq l(-1) at the most rural site (LGS) to about 200 mu eq l(-1) at TSP and LCG. The calcium concentration ranges from 25 to 250 mu eq l(-1), while the total nitrogen concentration is between 30 and 150 mu eq l(-1); ammonium is generally twice as high as nitrate. China's acid rain research has traditionally been focused on urban sites, but these measurements show a significant influence of long range transported air pollutants to rural areas in China. The concentration levels are significantly higher than seen in most other parts of the world. (c) 2006 Elsevier Ltd. All rights reserved.