金华市大气降水的化学组成特征及来源解析

对2004年大气降水样品监测资料的综合分析和研究表明,金华市降水样品pH值的分布范围在3.64~6.76之间,降水的酸雨率为79.3%。SO24-和NO-3是降水中主要的阴离子,分别占降水中阴离子总量的66.1%和21.7%。NH 4和Ca2 是降水中含量最高的阳离子,分别占阴离子总量的56.6%和33.4%。降水中这些离子的浓度水平一般比世界上其它地方高,但大大低于国内的北方地区。由于降水中缺乏足够的中和物质,大约76%的降水酸度被NH 4、Ca2 和K 等碱性成分中和。陆源型离子Ca2 、Mg2 和K 以及海盐性离子Na 和Cl-之间存在明显的相关关系,另外Ca2 和SO24-、Mg2 和SO24-、Mg2 和NO-3以及Mg2 和Cl-之间也可以观察到比较好的相关关系。土壤和海水的富集系数表明,研究区域的Ca2 和K 主要来源于岩石/土壤风化,SO24-和NO-3主要归因于人为活动的影响。

Analysis on the Origin and Characteristics of Chemical Composition of Precipitation in Jinhua

A comprehensive study of the chemical composition of wet precipitation was carried out during 2004 in the central of Zhejiang Province,China.All samples were analyzed for pH,electrical conductivity and major ions(F~-,Cl~-,NO~-_3,SO~(2-)_4,K~ ,Na~ ,Ca~(2 ),Mg~(2 ) and NH~ _4).pH of individual precipitation events,ranged from 3.64 to 6.76.About 79.3% of the precipitation had a pH of less than 5.60.SO~(2-)_4 and NO~-_3 were the main anions,accounting for 66.1% and 21.7% of the total mass measured anions in precipitation,respectively.NH~ _4 and Ca~(2 ) were the main cations,they made up approximately 56.6% and 33.4% of the total mass measured cations,respectively.The concentrations of these main ions were generally high compared to those reported in many other areas around the world,but much lower than that in northern China.The alkaline cations,NH~ _4 and Ca~(2 ),acted as acid neutralizers and buffered the acidity of precipitation.The results indicated that about 76% acidity was neutralized by alkaline constituents due to the lack of neutralization in precipitation.Significant correlations were found soil-derived species among Ca~(2 ),Mg~(2 ) and K~ and sea-salt species between Na~ and Cl~-.Other relatively good correlations were observed between Ca~(2 ) and SO_2=4,Mg~(2 ) and SO~(2-)_4,Mg~(2 ) and NO~-_3,Mg~(2 ) and Cl~-.Enrichment factor of marine and soil indicated that Ca~(2 ) and K~ came mainly from the terrestrial source,and SO~(2-)_4 and NO~-_3 is mostly attributed to the anthropogenic activities in the studied region.