Lead, cadmium, copper and zinc contents in stream-waters and sediment from various watershed classes of Pasak Watershed [Thailand]
1991
Sangad Akaravanich
Contents of four heavy metals in both water and sediment are different according to the classes of watershed, seasons and land usage. The average contents of lead, cadmium, copper and zinc in the water air are 9.27-26.54, 0.59-1.13, 18.43-32.72 and 58.91-105.49 micro g/l respectively while in the sediment are 3.75-12.07, 0.37-0.98, 5.16-17.04 and 28.51-105.29 micro g. The water has the highest lead, cadmium and zinc content in the forth class and copper in the fifth class whereas in the sediment lead cadmium and zinc are highest in the fifth and copper in the forth. The pattern of the content is different according to the local activities in the area rather than the classes of the watershed. The forest areas are less polluted. The highest contents of heavy metals in the water are found in rainy season while in the sediment are in summer. However, the contents of heavy metals found are lower than the standard set by WHO for the surface and drinking water. Nevertheless, proper management in the first class of watershed is still in great need because it is the primary source of water.
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