Enhanced Pesticide Sorption by Soils Containing Particulate Matter from Crop Residue Burns

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• 作者：Yaning Yang and Guangyao Sheng
• 刊名：Environmental Science & Technology
• 出版年：2003
• 出版时间：August 15, 2003
• 年：2003
• 卷：37
• 期：16
• 页码：3635 - 3639
• 全文大小：128K
• 年卷期：v.37,no.16(August 15, 2003)
• ISSN：1520-5851

文摘

Lack of proper techniques to isolate black carbon (BC)from soils has hindered the understanding of their roles inthe sorption and environmental fate of organic contaminantsin soils and sediments. The burning of crop residuesmay be the primary source of BC in agricultural soils. Inthis study, wheat (Triticum aestivum L.) and rice (Oryza sativaL.) residues were burned, and the resulting particulatematter (ashes) along with a soil were used to sorb diuronfrom water. Calculations indicated that the burning ofcrop residues may result in an appreciable level of ashesin soils. The diuron sorption isotherms on ashes werecurvilinear Langmuir type, suggestive of surface adsorptionand similar to that with activated carbon. Ashes were 400-2500 times more effective than soil in sorbing diuronover the concentration range of 0-6 mg/L. Sorption bywheat ash-amended soils and the degree of isothermnonlinearity increased with increasing ash content from0% to 1% (weight), indicating the significant contribution ofwheat ash to the sorption. Calculations show that wheatash and soil independently contributed to the sorption. Abovethe wheat ash content of 0.05%, the sorption was largelycontrolled by the ash. Density-based fractionation andrepeated HCl-HF washing of wheat ash yielded carbon-enriched fractions and enhanced diuron sorption by thesefractions. BC appeared primarily responsible for the highadsorptivity of ashes. Ashes arising from the burning of cropresidues may be an important determinant of pesticideimmobilization and environmental fate in soils.