Lead, cadmium, copper and zinc contents in streamwater and sediment from various watershed classes of Moei watershed, Changwat Tak
1993
Boonterm Saepung
Annual average of the total contents in streamwater of the four heavy metals among the 5 various watershed classes were different. The highest lead content was found in the third watershed class. Cadmium and zinc were highest in the fifth watershed class and copper was highest in the second watershed class. Lead content in sediment was highest in the second watershed but cadmium, copper and zinc contents in sediment were highest in the fifth watershed class. The average contents of lead and cadmium in streamwater were highest in winter season. Copper and zinc contents were highest in rainy and summer season respectively. The average contents of all heavy metals in sediment were highest in summer season. Cadmium, copper and zinc contents in non-forest area were greater than in forest area except the lead content only. However, the contents of four heavy metals were not exceed the maximum permissible standard level in surface water of NEB and WHO. Nevertheless the four heavy metals in sediment were not quite different from the other main streams of Thailand.
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