成都经济区As等元素大气干湿沉降通量及来源研究

A study of elements flux and sources from atmospheric bulk deposition in the Chengdu Economic Region

2004年8月—2005年8月在四川省成都、德阳等6万km2的农田区进行了为期一年的大气样品采集,共采集干、湿沉降样品28件,分别测试干、湿沉降中B、Mo、Mn、Zn、As、Cd、Hg、Pb、K、Ca、Na和Mg元素含量,计算获得各元素的年沉降通量;其中4种有害元素年沉降通量平均值分别为As2.77mg.m-2.a-1、Cd1.77mg.m-2.a-1、Hg0.10mg.m-2.a-1、Pb45.95mg.m-2.a-1。应用主成分分析对大气干湿沉降中各元素进行区分,取得了相当好的结果。其中第一主成分为Hg、Pb、Zn、Cd、Mo和As;第二主成分为K、Mg、Na、Mn和B;第三主成分为Ca。主成分对原始变量解释度达到94.88%,第一主成分说明Hg、Pb、Zn、Cd、Mo和As是影响大气质量的主要因素。将各干湿沉降接收点元素沉降通量与相应点位土壤元素含量进行相关分析表明,Pb、Hg在两种介质中相关性显著,说明土壤中Pb、Hg积累与大气干湿沉降具有密切关系,其他元素来源则更为复杂。通过不同地区重金属元素沉降通量的比较发现,各地区元素沉降通量差异明显,其中成都和德阳两地As、Cd、Hg、Pb沉降量显著较高,说明沉降中污染元素来源与不同地区工矿企业类型和数量有关。

In this project, from 2004 to 2005, 28 samplers collected bulk atmospheric samples, both dry and wet, on the agricultural lands in the Chengdu Economic Region （CER） of Sichuan. The samples were filtered and divided into soluble and insoluble fractions; both were analyzed for B, Mo, Mn, Zn, As, Cd, Hg, Pb, K, Ca, Na and Mg. The annual deposition flux of these 12 elements was calculated. The flux of the 4 hazardous elements, As, Cd, Hg and Pb, are 2, 77 mg · m^-2 · a^-1 , 1.77 mg· m^-2 · a^-1, 0.10 mg · m^-2 · a^-1 and 45.95 mg · m^-2 · a^-1 , respectively. Principal component analysis （PCA） via SPSS was employed for the total depositions and it demonstrates that the main components are Hg, Pb, Zn, Cd, Mo and As, which explains the status quo of atmospheric pollution. PCA analysis on total depositions, explains 94. 88 % of the total vari- ance and three groups of variables are identified. Correlation between element deposition flux and element content in soil was processed, and it shows significant correlation coefficient for both Pb and Hg, which indicates that the soil Pb and Hg contamination are attributed to atmospheric bulk deposition, whereas for other elements more complicated sources need to be considered. Comparison of the deposition flux of elements was carried out and it shows relatively big differences between districts, especially for the significantly heavy loadings of As, Cd, Hg, Pb into Chengdu and Deyang, pointing out that the sources of atmospheric metal pollutants are related to the types and quantities of local enterprises.