东亚地区降水离子成分时空分布及其特征分析

Analysis of the Spatial-Temporal Distribution and Ion Features of Components of Precipitation in East Asia

利用东亚酸沉降监测网(EANET)观测资料,对2001年东亚地区降水成分的时空分布特征进行了分析,通过与过去的观测进行对比,揭示东亚各地酸雨分布情况及降水化学特性差异,为东亚酸沉降长距离输送模式比较计划提供前期分析资料.分析结果表明:(1)东亚地区降水化学成分表现出明显的地域特征,滨海地区的日本降水含量中Na+、Cl-分别为219、208μmol·L-1居东亚地区之首,而中国西北地区Ca2+、NO-3、NH4+、SO24-、Mg2+、K+含量最高各为755、168、260、768、59.3、53.6 μmol·L-1;降水酸度主要受阳离子Ca2+、NH4+和阴离子SO24-、NO3-的影响.(2)东亚地区降水化学成分季节变化明显,除部分源自人为或工业排放源影响外(如北部地区冬季取暖),东亚地区气候呈季节变化也是影响的主要因子之一.春季沙尘源区沙尘、扬沙频繁,其上空存在较强的西风带,在天气系统冷锋影响下,沙尘粒子易随大风扬起而由锋前强烈抬升气流输送到对流层中层,在高空西风急流作用下输送到下游地区.(3)东亚地区酸雨区降水与以往主要以硫酸型酸雨为主的降水性质不同,除中国西南工业欠发达地区仍为硫酸型外,其他酸雨区均为硫酸和硝酸混合型.表征酸雨类型的特征参量[SO24-]/[NO3-]的比值在中国西南地区为3～5,东南和华南地区为0.5～3;其他各国均在0.5～3之间.

By means of the observational data (2001) from EANET, the analysis of the spatial-temporal distribution characteristic of components from precipitation over East Asia was performed. Compared with the historical data, the acids rain distribution and it chemical characteristic differences were revealed in East Asia. These provided the Model Inter-comparison Study of Lang-Range Transport and Acid Deposition in East Asia with the pre-analyzed data. The results show as follows:(1) There exist significant differences in regional characteristics of the chemical components from rainfall over East Asia. Such as Japan surrounded by sea, the concentrations of Na +and Cl -in rainfall are up to 219 and 208 μmol·L -1 respectively, which lie in the first albums in East Asia. Whereas the highest concentrations of Ca 2+, NO-_ 3,NH+_ 4,SO 2-_ 4, Mg 2+, K + in Northwest of China are up to 755, 168, 260, 768, 59.3 and 53.6 μmol·L -1 respectively, the main factors that impact on precipitation acidity derive from Ca 2+, NH4 + and SO 2-_ 4, NO_ 3. (2) There exist great variations with the seasonal changes in the chemical components from precipitation over East Asia. In addition to the influence of anthropogenic and industrial emissions (e.g.,winter heating in cold north regions), the seasonal change of climate over East Asia is also one of main influential factors. For example, blowing dust is frequent in source regions in spring. Over where exist a strong westerly belt, the dusts are easily blown by strong wind under the impacts of the cold front and transmitted to the middle of troposphere, and then transported to the down regions under the influence of westerly jet. (3) There exist obvious variations between precipitation containing the mixture of sulfate and nitrate today and that containing sulfate in East Asia. With the exception of southwest region in China, in which the industry is underdeveloped and the rainfall is still sulfate type. The ratio of SO 2-_ 4 to NO-_ 3 that stands for the type of acid rain ranges from 3 to 5 in southwest region, 0.5 to 3 in the southeast and south regions of China, the others range from 0.5 to 3.