Metolachlor Sorption and Degradation in Soil Amended with Fresh and Aged Biochars

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• 作者：Carmen Trigo ; Kurt A. Spokas ; Kathleen E. Hall ; Lucia Cox ; William C. Koskinen
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2016
• 出版时间：April 27, 2016
• 年：2016
• 卷：64
• 期：16
• 页码：3141-3149
• 全文大小：499K
• 年卷期：0
• ISSN：1520-5118

文摘

Addition of organic amendments such as biochar to soils can influence pesticide sorption–desorption processes and, in turn, the amount of pesticide readily availability for transport and biodegradation. Sorption–desorption processes are affected by both the physical and chemical properties of soils and pesticides, as well as soil–pesticide contact time, or aging. Changes in sorption–desorption of metolachlor with aging in soil amended with three macadamia nut shell biochars aged 0 (BC_mac-fr), 1 year (BC_mac-1yr), and 2 years (BC_mac-2yr) and two wood biochars aged 0 (BC_wood-fr) and 5 years (BC_wood-5yr) were determined. Apparent sorption coefficient (K_d-app) values increased with incubation time to a greater extent in amended soil as compared to unamended soils; K_d-app increased by 1.2-fold for the unamended soil, 2.0-fold for BC_wood-fr, 1.4-fold for BC_wood-5yr, 2.4-fold for BC_mac-fr, 2.5-fold for BC_mac-1yr, and 1.9-fold for BC_mac-4yr. The increase in calculated K_d-app value was the result of a 15% decrease in the metolachlor solution concentration extractable with CaCl₂ solution with incubation time in soil as compared to a 50% decrease in amended soil with very little change in the sorbed concentration. Differences could possibly be due to diffusion to less accessible or stronger binding sites with time, a faster rate of degradation (in solution and on labile sites) than desorption, or a combination of the two in the amended soils. These data show that transport models would overpredict the depth of movement of metolachlor in soil if effects of aging or biochar amendments are not considered.