Tuesday, 11 July 2006

Ecotoxicological Assessment of Heavy-Metal Contaminated Soils by Soil Enzymes and Luminescent Bacteria.

Jae E. Yang1, Sang-Phil Lee1, Yong-Sik Ok1, Kyung-Yoal Yoo1, and Ki-Cheol Eom2. (1) Kangwon National University, Division of Biological Environment, Chuncheon, South Korea, (2) National Institute of Agricultural Science and Technology, 249 Seodun-dong, Kwonsun-gu, Suwon, South Korea

Objective of this research was to evaluate a relevance of soil enzymes (dehydrogenase and urease) and luminescent bacteria (Photobacterium phosphoreum) for an ecotoxicological assessment of the metal contaminated soils. Enzymatic and microbial activities of the soils contaminated with each metal decreased consistently and proportionally as increasing metal concentration in the soils. The EC50 of dehydrogenase activity for the soils increased in the order of Hg < Pb < Cr < As < Cu. Whereas the EC50 of urease activity for the soils increased in the order of Hg < Cd < Cr < Cu < Pb. Mercury showed the most toxic effect on the soil enzymes among the six metals evaluated. Microtox test showed that microbial activities decreased as 12~15% by Hg, 3~13% by Pb, 8~15% by Cu, 5~15% by As, 8~13% by Cd and 3~12% by Cu, as compared to the control. There existed a discrepancy in rates of responses to metal toxicity between soil enzymes and luminescent bacteria showing the soil enzymes were more sensitive. The results showed that ecotoxicological tests using soil enzyme and luminescent bacteria were specific to each metal and need a further work to be used as a protocol, even though could be applicable as an index for the assessment of the toxic metal contaminated soils.

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