森林降水酸度及电导率的时空变化

TEMPORAL AND SPATIAL CHANGES IN ACIDITY AND ELECTRICAL CONDUCTIVITY OF FOREST PRECIPITATION

在离大气污染源距离不同的两片杉木 (Cunninghamia lanceolata)人工林中建立监测场 ,对降水化学进行了为期 3年 (1994～ 1996 )的定位监测。降水通过林冠截留后 ,其酸度和电导率均明显增加 ,尤以树干径流为显著。在 FFC监测场 ,降雨、穿透雨和树干径流雨量加权平均 p H值分别为 6 .13、6 .0 6和 4.18,在 XQF监测场 ,其相应的数值分别为 5 .86、5 .6 7和 3.37;降雨和穿透雨的酸度表现出一定的季节变化动态 ,其最低月均 p H值出现在夏委 ,最高值在冬季。在 FFC监测场 ,降雨、穿透雨和树干径流雨量加权平均 EC值分别为 2 8.5 1μs· cm- 1、6 3.71μs·cm- 1 、2 40 .85μs· cm- 1 ,在 XQF监测场 ,其相应的数值分别为 36 .99μs· cm- 1 、6 6 .41μs· cm- 1 、5 0 1.85μs·cm- 1 ;降水电导率表现出显著一致的季节变化格局 ,其月均值均以夏季最低 ,冬季最高 ,春秋季居中 ,这种格局强烈受降雨量的影响。离污染源较近的 XQF监测场 ,降水酸度和电导率明显高于相对未受污染的

The chemistry of forest precipitatio n was monitored for three years at two sites in Chinese fir (Cunninghamia lanceolata ) plantations with different distances from a known atmospheric pollution sour ce. Precipitation acidity and electrical conductivity (EC) were significantl y el evated upon passage through forest canopies at both sites, and more so especiall y by stemflow. The average volume-weighted pH values for rainfall, throughfall and stemflow were 6.13,6.06 and 4.18, respectively, at the FFC forest site (furt her from emission source), and 5.86,5.67 and 3.37 at the XQF forest site. Acidi ty of rainfall and throughfall showed some seasonal trends,with minimal pH value s in summer and maximal in winter. The average volume-weighted EC values fo r rainfall, throughfall and stemflow were respectively 28.51, 63.71 and 240.85 a t FFC, and 36.99,66.41 and 501.85 at XQF. EC values of precipitation exhibit ed a strong seasonal pattern, with minimal values consistently found in summer m onths, intermediate in spring and fall, and maximal in winter, a pattern which a ppeared to be influenced greatly by the pattern of total precipitation. Acidity and electrical conductivity of precipitation at XQF near the emission source wer e significantly higher than that at FFC, which was relatively unaffected by air pollution.