| Air pollution is an important environmental issue that affects the healthy development of human society and the natural functioning of ecosystems, which has the characteristics of long-term accumulated, long-distance transmission and global impacts. Due to human activity intensity is relatively small, remote mountain areas can truly reflect the migration process of atmospheric pollutants under natural background conditions. Mountains Taibai located in the central of Shaanxi Province, is the highest peak in the east of Qinghai-Tibet Plateau,which barriers the atmospheric circulation and heat water exchange between.north and south, and has become the climate north-south dividing line, the North Slope is affected more by the cold and dry continental northwest airstream,while the Southern slope is affected more by the southeast monsoon humid air mass. By analyzing the data of ions (SO42-、 NO3-、NO2-、Cl-、F-、NH4+、Ca2+、Mg2+、Na+、K+) in precipitation of the fixed sampling points at Mountain Taibai and the ions data of precipitation at different altitudes during December 2011 and September 2014, combined with correlation analysis, enrichment factor and the end source contribution method, studying the time variation and spatial distribution difference of the precipitation chemical characteristic at the Southern slope and he North slope of the Mountains Taibai, revealing the altitude effects of precipitation characteristic at Taibai mountain, inferring the basic characteristic and sources pollutants of the precipitation. The main conclusions of this study are:(1) The basic characteristics of Taibai Mountain precipitation ion concentration analysis results:In the study period, ions concentration fluctuation ranges of precipitation at Mountain Taibai are: 20.12μeq·L-1～1421.17μeq-L-1 and 209.02μeq·L-1-2344.78μeq·L-1, respectively mean:483.28μeq·L-1 and 638.15μeq·L-1. The fluctuation of ions concentration of precipitation at mountain Taibai are large and the precipitation pollution at north slope is higher than that of southern slope. Ions concentration of precipitation at south slope are in the order of Ca2+>SO42->NH4+>NO3>K+>Na+>Mg2+>Cl->F-, ions concentration of precipitation at south slope are in the order of NH4+>Ca2+>SO42->NO3->Na+> Mg2+>C1->K+>F-,described SO42-、NO3- and NH4+、Ca2+ are the main ions in precipitation. Ca2+ concentration accounts for the highest proportion in the precipitation at Huangbaiyuan sampling point, showing the characteristic that terrestrial dust has a large impact. NH4+ concentration accounts for the highest proportion in the precipitation at Tangyu sampling point, showing the characteristic that human activity has a large impact. NH4+and Ca2+ are the main neutralizing factors, and neutralizing capacity is highest in summer.(2) The results of altitude effects of precipitation characteristic at mountain Taibai are:The ion concentrations of precipitation at mountain Taibai decrease with increasing altitude, ion concentrations in non-monsoon period were significantly higher than that in monsoon period, with the rise of altitude, both concentrations tended to close. Lapse rates of ion concentrations in the non-monsoon period are greater than that in the monsoon period, it’s mainly because the leaching intensity of precipitation and sources contribution are different in different seasons. The tends of percentages of different ions concentrations with increasing altitude is different, showing the different source characteristics of sea salt, crust sources and anthropogenic sources. Na+/Cl- ratio shows that the vapor transmission height is lower in non-monsoon period than that of the monsoon.(3) Time variation of ions concentrations of precipitation at Mountain Taibai analysis results are: Ions concentrations of precipitation at Mountain Taibai are affected by precipitation, pollutant emission sources, atmospheric conditions, which are high in winter and spring while low in summer and autumn, the highest concentration occurs in December.(4) Results for sources of ions in precipitation at Mountain Taibai are:The enrichment factor and sea salt tracer analysis showed that the non-sea salt contribution rates of SO42- and NO3- in precipitation at Mountain Taibai are close to 100%, while relative to crustal source is also highly enriched, indecating that SO42- and NO3- mainly come from human activities. Non-sea salt source contribution of K+ was 99% while relative to the crust is highly enriched, so K+ mainly contributed by anthropogenic sources. There is a considerable part of the contribution of Na+ and Mg2+ come from salt source, Mg2+ sea salt source rate accounts for 11.89%, Na+ salt source rate accounts for 45.4%.(5) Results compared with other alpine sites:Alpine sites and other marine ion concentration data of precipitation at home and abroad, showing marine and terrestrial precipitations are significantly different, ion concentrations are high in ocean precipitation and Na+ and Cl- are the main component; our country is a developing country, anthropogenic interference is strong, NH4+, SO42- and NO3-concentrations in precipitation are significantly higher than that at the United States Wasatch Mountain and Rocky Mountain regions. Compared to other alpine station, ions concentrations of precipitation at Mountain Taibai are higher, showing a chararicter that is contiental and strongly affected by human activity. Na+/ Ca2+ and Cl-/Ca2+ values of Taibai Mountains and Qilian, Yulong Snow Mountain, Waliguan sites are generally less than Tarzan, Mangdangshan, Dinghu Mountain, Wuyishan and Fingers, showing the impact from coastal to inland sea salt source of Precipitation Vietnam smaller and smaller, while the impact of land-based sources is growing. |
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