Sorption-Desorption Behavior of Imazethapyr and Imazapic on Six Brazilian Soils

ABSTRACT: The characterization of sorption-desorption for imazethapyr and imazapic in six agricultural soils was performed to assess the availability of these herbicides in pollution processes. In this pursuit, the batch equilibrium method and high-performance liquid chromatography were used. The magnitude of Kf values ranging from 0.38 to 2.52 mg1-n kg-1 Ln for imazethapyr and 0.43 to 2.72 mg1-n kg-1 Ln for imazapic indicate weak sorption in the evaluated soils. Soil pH (5.1 to 6.1) and iron oxalate affect sorption-desorption of both herbicides but the type and percentage of clay can be the main factor affecting these two processes. A high desorption percentage (>70%) was found in Regosol, Dystric Plinthosol, Ferralsol (for both herbicides), and Dystric Gleysol (only imazapic) soils, which implies in leaching risks of these imidazolinone herbicides into groundwater. Lower desorption (<50%) was found in Cambisol and Alisol (for both herbicides), and (~50%) in Dystric Gleysol (only imazethapyr) soils, indicating that these herbicides could potentially injure the sensitive crops grown in rotation.

摘要：本研究针对六种农业土壤中的咪唑乙烟酸（imazethapyr）与咪唑喹啉酸（imazapic）的吸附-解吸特性开展表征，以评估这两种除草剂在污染过程中的环境可利用性。研究采用批量平衡法与高效液相色谱法完成相关实验。弗罗因德利希吸附常数Kf值范围为：咪唑乙烟酸0.38~2.52 mg^(1-n)·kg⁻¹·Lⁿ，咪唑喹啉酸0.43~2.72 mg^(1-n)·kg⁻¹·Lⁿ，表明两种除草剂在所测试的土壤中均表现出弱吸附特性。土壤pH值（5.1~6.1）与草酸铁含量会对两种除草剂的吸附-解吸过程产生影响，而土壤黏粒的类型与占比或是调控该过程的核心因素。在新成土（Regosol）、不饱和铁质聚成土（Dystric Plinthosol）、铁铝土（Ferralsol，两种除草剂均适用）以及不饱和潜育土（Dystric Gleysol，仅咪唑喹啉酸适用）中，除草剂解吸率均高于70%，这意味着此类咪唑啉酮类（imidazolinone）除草剂存在向地下水淋溶的风险。在雏形土（Cambisol）与铝质土（Alisol）中，两种除草剂的解吸率均低于50%；而在不饱和潜育土中（仅咪唑乙烟酸适用），解吸率约为50%，表明此类除草剂可能对轮作种植的敏感作物产生药害。