Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Departamento de Solos e Engenharia Agrícola, Setor de Ciências Agrárias, Universidade Federal do Paraná, Curitiba, Brazil.
J Environ Sci Health B. 2019;54(11):906-914. doi: 10.1080/03601234.2019.1644947. Epub 2019 Jul 25.
We investigated the adsorption of glyphosate onto five subtropical soils of Paraná and São Paulo states, Brazil, a region of intense agricultural activities, aiming at the determination of kinetic and isotherm adsorption parameters which enable the evaluation of the potential leaching of the herbicide. The adsorption was fast, being described by the pseudo-second order and intraparticle diffusion models, thus suggesting that mixed mechanisms are involved. The Oxisol containing the highest concentrations of metal oxides (209.5 g kg FeO and 160.2 g kg AlO) was the sample with the highest rate constant, indicating the adsorption sites are readily available. All the soils are rich in aluminum and iron oxides, explaining the Freundlich coefficients (K) between 642 and 1360 mg kg L, which are higher than most of the coefficients described for other soils around the world. The maximum desorption (15% of the adsorbed amount) was observed for the Oxisol. For the other soils, desorption ranged from 2 to 7%. These results suggest that the leaching of free glyphosate to nearby surface and groundwaters is unlikely unless excessive doses are used. The adsorption parameters are useful for managing the right doses applied to the crops, thus avoiding contamination of adjacent areas.
我们研究了巴西巴拉那州和圣保罗州的五种植被亚热带土壤对草甘膦的吸附作用，该地区农业活动十分活跃，旨在确定动力学和等温吸附参数，以评估除草剂的潜在淋溶风险。吸附速度很快，可用准二级和内扩散模型来描述，表明涉及混合机制。含有最高浓度金属氧化物（209.5 g kg FeO 和 160.2 g kg AlO）的土壤是速率常数最高的样本，表明吸附位易于获取。所有土壤都富含铝和铁氧化物，这解释了 Freundlich 系数（K）在 642 到 1360 mg kg L 之间，高于世界上大多数其他土壤的系数。最大解吸量（吸附量的 15%）发生在氧化土中。对于其他土壤，解吸量在 2%到 7%之间。这些结果表明，除非使用过量剂量，否则游离草甘膦向附近地表水和地下水的淋溶不太可能发生。吸附参数可用于管理施用于作物的正确剂量，从而避免对周边地区的污染。
