Temporal and Spatial Changes in Acidity and Electrical Conductivity of Forest Precipitation
Chin J Plan Ecolo. 2000, 24 (4):
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The chemistry of forest precipitation was monitored for three years at two sites in Chinese fir (Cunninghamia lanceolata) plantations with different distances from a known atmospheric pollution source. Precipitation acidity and electrical conductivity (EC) were significantly elevated upon passage through forest canopies at both sites, and more so especially 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 (further from emission source), and 5.86,5.67 and 3.37 at the XQF forest site. Acidity of rainfall and throughfall showed some seasonal trends,with minimal pH values in summer and maximal in winter. The average volume-weighted EC values for rainfall, throughfall and stemflow were respectively 28.51, 63.71 and 240.85 at FFC, and 36.99,66.41 and 501.85 at XQF. EC values of precipitation exhibited a strong seasonal pattern, with minimal values consistently found in summer months, intermediate in spring and fall, and maximal in winter, a pattern which appeared to be influenced greatly by the pattern of total precipitation. Acidity and electrical conductivity of precipitation at XQF near the emission source were significantly higher than that at FFC, which was relatively unaffected by air pollution.