土壤不同粒径有机无机复合体对丁草胺的吸附特性

为了解土壤不同粒径组分对农药吸附-解吸行为的影响和吸附贡献率,以及不同粒径组分中有机无机组分的结合方式和复合程度如何影响有机质对农药的吸附,选取我国6个省区的7种理化性质差别较大的土壤,并采用物理方法提取该7种土壤的三个粒径有机无机复合体(黏粒:0.002mm;粉粒:0.02~0.002 mm;砂粒:0.05~0.02 mm)为研究材料,采用批量平衡法研究丁草胺在不同土壤和不同粒径有机无机复合体固/液界面的分配规律。同时,定量计算土壤各粒径组分对丁草胺的吸附贡献率,并从有机无机复合体角度探讨不同粒径组分中总有机碳(TOC)对丁草胺的吸附特性。结果表明:土壤黏粒组分对丁草胺具有最大的吸附量和较小的解吸率,而砂粒组分对丁草胺则具有较小的吸附量和最大的解吸率。土壤黏粒、粉粒和砂粒组分对丁草胺的吸附贡献率分别为36.7%~72.4%、21.7%~50.5%和10%。TOC是影响各粒径组分对丁草胺吸附的主要原因,但其影响程度受各粒径组分中TOC的理化性质以及其与无机矿物的复合程度控制。

Effect of Soil Organo-Inorganic Compounds Different in Particle Size on Butachlor Sorption

Objective] The sorption of pesticides (including herbicides) by soil is an important factor affecting environmental behaviors of the substances.It is important to investigate effects of composition manner and complexation degree of the organic and inorganic components in particles different in size on pesticide sorption-desorption behaviors in the soil,and their contributions to pesticides sorption in the soil.Method] In the current study,soil samples of 7 different types of soils were collected from six different provinces or regions and processed physically and separately for extraction of three particle-size fractions,that is,clay (＜ 0.002 mm),silt (0.02 ～ 0.002 mm),and sand (0.05 ～ 0.02 mm),of organo-inorganic compounds.The batch equilibrium method was used to explore rule for allocation of butachlor in the interfaces between different particle-sized compounds and soil solution and at the same time quantitative calculation was done of contributions of the different particle size fractions of compounds to the total butachlor adsorption in the soil.In the end,analysis was performed of butachlor adsorption characteristics of total organic carbon (TOC) in different particle size fractions from the angle of organo-inorganic compounds.Result] Results show that the clay fraction was the highest in butachlor adsorption capacity but the lowest in desorption rate,while the sand fraction was the lowest in adsorption capacity but the highest in desorption rate.The contribution rate of the three fractions to butachlor adsorption ranged from 36.7 to 72.4％,from 21.7 to 50.5 ％ and ＜ 10 ％ for clay,silt and sand fractions,respectively.TOC was the key factor affecting butachlor sorption in the three fractions of the soil,but how much was the effect depends on physico-chemical properties of the TOC per se in each fraction and degree of the TOC compounding inorganic minerals.In the clay fraction,butachlor retention on TOC was affected significantly by inorganic minerals;in the silt fraction,it was not much affected;while in the sand fraction,it was almost not affected.Conclusion] In the current study,bioavailability of butachlor absorbed in different soil size fractions and migration of the substance in the environment was effectively predicted.The findings can be used to serve as theoretical basis for farmers to rationalize application of butachlor in the light of soil type so as to reduce environmental pollution.