皖南山区降水酸性特征与元素沉降通量

Acidity Characteristics and Element Flux of Rainwater in the Hilly Area of South Anhui,China

以位于北亚热带的安徽南部丘陵地区为研究区域,2007年4～11月间通过定期监测雨水以及对其pH和主要阴阳离子的测定,分析了该地区降水的酸性特征与H+和其他元素的沉降通量.结果表明,在皖南地区雨水pH的平均值为4.61,酸雨频率高达92%.Ca2+是含量最高的阳离子,平均浓度为68.82μeq/L,SO24-是含量较高的阴离子其浓度为39.69μeq/L.SO24-/NO3-的平均值是1.23,反映了大气污染特征是SO2与NOx并重的复合型污染.雨水中各离子含量和输入量的动态变化表明该地区大气NOx主要是近源的农业活动所引起,SO2主要来自远源工业污染,盐基离子的变化则有北方沙尘远源传输的影响.2007年4～11月降水输入的盐基离子总量为1289eq/hm2,NO3-和SO42-的总量为926eq/hm2,H+总量为360eq/hm2,表明酸沉降对区域生态环境的影响不容忽视.

The current study takes the hilly south Anhui province as the study area, which is located in the subtropical China and far from urban and industrial activities. The rainwater samples were collected from April to November in 2007 and were determined for pH, major cations and anions, to estimate acidity characteristics and the sum of hydrogen ion and other cation and anion input during the studied period. The results showed that the frequency of acid rain was over 92%, with an average pH of 4.61. The average concentrations of SO4^2-- and Ca^2＋ were 39.69 μeq/L and 68.82 μeq/L respectively, which were the most abundant cation and anion among the determined elements. The atmospheric pollution was characterized as SO2 and NOx with an average of SO4^2-/NO3^- 1.23 in the rainwater. The variation of the major chemical component in the rainwater with time implied that the atmospheric NOx mainly originated from the local agricultural activities, while SO2 was mainly affected by non-local source and the base cation was mainly affected by dust transportation during spring season. The total input of base cation and H ＋ was 1 289 eq/hm^2 and 360 eq/hm^2 respectively, while that of SO4^2- and NO3^- was 926 eq/hm^2 from April to November in 2007. The input of acid deposition may have a detrimental effect on the local ecosystem.