 BackShort Report ScienceAsia 23 (1997): 123-134 |doi: 10.2306/scienceasia1513-1874.1997.23.123 TRACE METALS IN THE MAE KHA CANAL AND THE MAE PING RIVER IN CHIANG MAl, NORTERN THAILANDZHENBO YANGABSTRACT: The study was conducted by collecting water and sediment samples form the Mae Kha Canal and the Mae Ping River at the ends of the rainy and dry seasons in 1994. The Cd, Cu, Pb and Zn contents in the samples were analyzed by atomic absorption spectrophotometry. Various sample pretreatment procedures were employed prior to the analysis depending on the samples concerned. Meted ions in the water samples were complexed with the mixture of pyrrolidinecarbodithioic acid ammonium salt (APDC) and dielhylammonium N,N-diethyldithiocarbimate (DDDC), and the complexes were then extracted with isobutyl-methylketone (MIBK) and the metal ions were back extracted into the aqueous solution. The sediment samples were digested by HNO3:HCl (1:3/v/v) solution. The results showed that Cd Cu, Pb and Zn contents in the Mae Kha Canal were much higher than those in the Mae Ping River even though the distribution of such metals was not uniform. The contents of the four elements in the sediment samples were also higher them the average abundance of them in the granite rock which is a geological characteristics of the Chiang Mai Basin. Metal contents in the water samples in both the Mae Kha Canal and the Mae Ping River were lower than the Thai national standard levels for a second class serface. water indicting that the water was still acceptable in terms of the Cd, Cu, Pb and Zn pollution. However, the water in the Mae Kha Canal can not be recommended as drinking water even after apropriate water treatment is applied. Institute of Environmental Health Monitoring Chinese Academy of Preventive Medicine. 7 Pan Jia Yuan Nan Li, Beijing 10002, P.R.China. Received September 7, 1996
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