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(66-03) The Interdependency of Toxicity and Binding Sorption Types of Paraquat in Soil-water System . Noegrohati, Sri*,1, Narsito, N, 1 Gadjah Mada University, Yogyakarta, Indonesia ABSTRACT- The sorption desorption study of paraquat (1,1-dimetil-4,4-bipyridinium dichloride) and its commercial formula, Gramoxone, showed that two adsorption sites are involved, resulting in two types of binding, i.e. tightly bound and loosely bound paraquat. In this work, the effect of those types of binding toward their toxicity to several biota, such as Chlorella sp., wheat and rice were studied.. Those biota were exposed to leachates of paraquat and Gramoxone prepared from several soil types, i.e. peat, acid sulfate, kaolinitic, and montmorillonitic. The end point used in toxicity studies for Chlorella sp. was population growth inhibition, while for wheat and rice were their root growth inhibition. The result showed that the sorption capacity of tightly bound paraquat depends to the clay mineral types present in the soil. It was found that monmorillonitic soil type have the highest tightly bound capacity, followed by kaolinitic soil type, and peat soil. There is a strong correlation between the tightly bound capacity of paraquat and the No Observed Effect Concentration (NOEC) of the biota studied. In order to be able to have observable toxicity effects of paraquat on the biota, the paraquat applied should be significantly higher than the tightly bound capacity of each soil, while the observed effect of paraquat correlated with the total sorption capacity, both tightly bound capacity and loosely bound capacity. Key words: Paraquat, , toxicity, soil types, adsorption binding types |
