Lead, cadmium, copper and zinc contents in stream-waters and sediment from various watershed classes of Loei Watershed
1993
Apichart Posu
Heavy metal content in stream water and sediment among 5 various classes were different. In stream water, the highest contents of lead and zine were in the fourth class of watershed at the values of 9.43 and 18.42 microgram/litre respectively while the highest contents of cadmium and copper were in the fifth and first class of watershed, at the values of 9.26 and 26.63 microgram/litre. In sediment, lead and cadmium had the highest contents in the fourth class of watershed at the values of 52.29 and 4.20 microgram/gram. But copper and zinc had the highest contents in the fifth and first class of watershed at the values 9.26 and 26.63 microgram/gram. The contents of Cadmium, copper and zinc in water were highest in summer at the values of 1.58, 2.84 and 22.54 microgram/litre respectively. However, lead had highest content in winter, the value was 12.36 microgram/litre. The contents of lead, copper and zinc in sediment were highest in rainy season at the values of 56.05, 7.05 and 19.97 microgram/gram respectively while cadmium had highest content in winter, the value was 4.46 microgram/gram. The content of heavy metal were corresponded to the usage of land, the heavy metal content in forest area were lower than that in non-forest area. The major factors influencing the contents of heavy metal were geological, type of landuse and human activities. However, the contents of lead, cadmium, copper and zinc in various watershed classes of Loei watershed were lower than the standard surface water of NEB and were not significant different from their contents in the other watershed and the major river of Thailand.
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