Chemical characteristics of precipitation at Nanping Mangdang Mountain in eastern China during spring

摘要

To study the characteristics of precipitation in eastern China, an automatic sampler was used to collect rainwater samples from 19 precipitation events at Mangdang Mountain, Nanping City, Fujiang Province, in the spring of 2009. We used ion chromatography to analyze the ionic components and concentrations, and inductively coupled plasma mass spectrometry (ICP-MS) to analyze element compositions and contents. The results demonstrated remarkable acidic characteristics: in more than 80% of precipitation events the pH was less than 5.6, with an average of 4.81. Mass concentration results showed SO_4~(2-) was the main anionic component (36.2% of the total anion mass), while NH_4~+ was the main cationic component (47.7% of the total cation mass) and main ion for acidity neutralization in the rainwater. Organic acid content accounted for 30.9% of total anion mass. The main trace metals were Ca, K, and Na. The SO_4~(2-)/NO_3~- ratio was 1.4, indicating that precipitation in this region was influenced by complex air pollution - the product of individual coal-burning combined with vehicle exhaust pollution. Correlation analysis of the chemical composition of the precipitation indicated that acidity in this region was determined by a combination of all acidic and neutralization ions rather than any single ion component. The results also showed that Na~+ and Cl~- contributions were mainly by seawater; Mg~(2+) by seawater and crustal materials; the NH_4~+, K~+, Ca~(2+), NO_3~- and SO_4~(2-) by anthropogenic sources; the trace metals were from the Earth's crust; and organic acids were potentially from combustion of biomass.