The impacts of anthropogenic emissions on the precipitation chemistry at an elevated site in North-eastern China

摘要

Ninety precipitation samples were collected from 2004 to 2006 at the summit of the Mt. Tai in order to detect the impacts of regional sources of pollution on precipitation chemistry in the highly polluted North China Plains. The annual volume-weighted pH of the precipitation was found to be 4.7, in contrast to the less-acidic nature (pH5.6) of precipitation in northern China reported in many past studies. Non-sea-salt (nss)-SO4 2- (131.5 μeq L-1), NH4 + (82.2 μeq L-1) and Ca2+ (61.4 μeq L-1) were the most abundant species in precipitation. The wide range of the Cl-/Na+ ratios (0.2-5.4) in precipitation implied the co-existence of Cl- enrichment and depletion. The nss-SO4 2-, NO3 -, NH4 +, Ca2+ and K+ concentrations peaked in spring, but with the lowest acidity. The very strong correlations of Ca2+ with nss-SO4 2- and NO3 - suggested a significant uptake of nss-SO4 2- and NO3 - on dust aerosol during spring. Samples with the lowest pH value (4.5) are associated with the stagnant air conditions. The nss-SO4 2- and NH4 + concentrations at Mt. Tai were the highest compared with those at the EANET, NADP and EMEP sites of similar elevations. With relatively high rainfall amount measured at our site, the high wet deposition of the major acidic/alkaline species exerted large loadings to the ecosystem. The associated impacts on agriculture, soil and aquatic systems should be investigated.