Distribution of organophosphate insecticides in a Thai biomass-water system

Sorption and leaching of the organophosphate (OP) pesticides chlorpyrifos, profenofos, methyl parathion and malathion were investigated with four different types of biomass: coconut husk, rice husk, peat moss and peanut shell. Organic carbon contents of the biomass were in the range of 35.4-45.4%. Sorption studies were carried out by the batch (equilibrium) method at 4 different OP spike concentrations and at pH 3-7. Sorption isotherms conformed to a linear Freundlich equation and the Freundlich constant or sorption coefficient (KD) confirmed that biomass organic carbon content was the principal sorbent factor affecting OP sorption. For a given sorbent, correlation of the extent of sorption with sorbate chemical properties was examined. Column leaching experiments involving different masses of coconut husk and peanut shell pre-spiked with OPs at the level equivalent to actual spraying concentrations in some Thai tangerine orchards were conducted. These experiments included repeated spikings and leaching. A water flow rate of 20 mL min(-1) was employed corresponding to the current average watering regime. Retardation and biodegradation with these sorbents were also examined.     

苯污染地下水系统反硝化菌分布及其净化过程

生物降解作用是地下水系统有机污染物自然衰减过程中最重要的破坏性衰减机制。在分析中,以我国某受苯污染水源地的地下水系统为对象,研究了该地下水中反硝化菌的分布,筛选出2株土著反硝化菌,通过生物降解实验证明其具有降解苯的能力,同时结合水源地历年的水质监测数据,首次从地球化学及生物学2个方面说明了该地下水中存在反硝化菌对苯的生物净化作用,为进一步研究该地下水中苯自然衰减规律奠定基础。     

Distribution pathways of hexachlorocyclohexane isomers in a soil-plant-air system. A case study with Cynara scolymus L. and Erica sp. plants grown in a contaminated site

This study focuses on the main routes of distribution and accumulation of different hexachlorocyclohexane (HCH) isomers (mainly α-, β-, γ- and δ-HCH) in a soil-plant-air system. A field assay was carried out with two plant species, Cynara scolymus L. and Erica sp., which were planted either: (i) directly in the HCH-contaminated soil; or (ii) in pots filled with uncontaminated soil, which were placed in the HCH-contaminated soil. Both plant species accumulated HCH in their tissues, with relatively higher accumulation in above-ground biomass than in roots. The β-HCH isomer was the main isomer in all plant tissues. Adsorption of HCH by the roots from contaminated soil (soil → root pathway) and adsorption through the aerial biomass from either the surrounding air, following volatilization of the contaminant (soil → air → shoot pathway), and/or contact with air-suspended particles contaminated with HCH (soil particles → shoot pathway) were the main mechanisms of accumulation. These results may have important implications for the use of plants for reducing the transfer of contaminants via the atmosphere.