施加牛粪有机肥对灰钙土吸附阿特拉津的影响机制

有机肥在改良土壤的同时也会改变农药的环境行为. 为明确施加牛粪有机肥对灰钙土吸附阿特拉津(ATZ)的影响作用及机制，采用批平衡试验，分析其吸附动力学、热力学以及牛粪施加量、pH、离子强度等因素对ATZ吸附的影响. 结果表明:①ATZ在灰钙土与施加牛粪灰钙土上的吸附均可分为快吸附、慢吸附直至平衡的过程，准二级动力学模型可较好地描述其吸附过程，施加有机肥增加了ATZ在灰钙土上的平衡时间，吸附速率受颗粒内扩散和外部液膜扩散共同控制. ②施加牛粪有机肥后，灰钙土对ATZ的吸附热力学更符合Freundlich模型，1/n在0.42~0.64之间，吸附属“L型”模式，低温和高温均会抑制ATZ在灰钙土上的吸附. ③pH和共存离子是影响ATZ在灰钙土上吸附的重要因素，随pH的升高，ATZ在灰钙土与施加牛粪灰钙土上的吸附量降低，这是由于碱性情况下，ATZ以阴离子存在，与带负电的灰钙土产生静电排斥作用；灰钙土施加牛粪有机肥后，共存阳离子对ATZ的吸附抑制作用明显，增加离子强度可能导致竞争吸附的存在，从而抑制有机离子在灰钙土上的吸附，且离子浓度越高，抑制越明显. 研究显示，土壤施加牛粪有机肥后，ATZ的吸附量增加，吸附由疏水性分配转变为多分子层化学吸附为主，表明施加牛粪有机肥会改变ATZ在灰钙土上的吸附行为和机制，降低ATZ在灰钙土中的迁移风险. 研究结果将为贫瘠黄土土壤改良风险和三嗪类农药的管控提供理论依据. 

Effect Mechanism of Organic Cattle Manure on Sorption of Atrazine on Sierozem

Organic fertilizers are rich in organic matter and nutrients, which can improve the soil quality and also modify the environmental behavior of pesticides in soil. However, their effect and mechanisms are still unclear and need further study. To clarify the effect and mechanisms of cattle manure application on atrazine (ATZ) sorption on sierozem, batch experiments were conducted to determine the sorption dynamics, sorption thermodynamics, pH, ion types and strengths, and other influencing factors. The results showed that the sorption of ATZ on sierozem and sierozem applied cattle manures can be divided into fast adsorption and slow adsorption. The pseudo-second-order kinetic model can better describe the adsorption process. The application of cattle manure fertilizer increases the adsorption equilibrium time of pollutants on sierozem, and the adsorption rate affected by intraparticle diffusion and external liquid membrane diffusion. After the application of cattle manure fertilizer, the adsorption thermodynamics of ATZ fitted well with the Freundlich model, and the 1/n ranged from 0.42 to 0.64, which belonged to the ‘L-type’ isothermal adsorption model. Both low and high temperature inhibited the adsorption of ATZ on sierozem. The pH and coexisting ions were key factors affecting the adsorption of ATZ on sierozem. With the increase of pH, the adsorption capacities of ATZ on sierozem decreased, which may be related to the ionization of ATZ. In the alkaline condition, ATZ is present as anion, producing an electrostatic repulsion with the negatively charged surface of sierozem. Different ions and ionic strengths can affect ATZ adsorption on sierozem with a strong buffer effect. However, after application of organic manure fertilizer into sierozem, the increase of the ions in soil solution may lead to the competitive adsorption of organic ions and cation on adsorption sites on sierozem surface, thus inhibiting the adsorption of organic ions on sierozem, and the higher the concentration of the same cation, the more obvious the inhibitory effect of ATZ adsorption on sierozem. The adsorption of ATZ on sierozem is mainly the result of ion exchange, electrostatic interaction, hydrogen bonding, van der Waals force and surface complexation. After the application of cattle manure fertilizer, the adsorption of ATZ on sierozem ncreased, and the adsorption mechanism changed from hydrophobic interaction to the chemical adsorption of multiple molecular layers, indicating that the application of natural organic fertilizer such as cattle manure may lead to changes in ATZ adsorption behavior and mechanism, and thus the migration risk of ATZ in sierozem is reduced. Our results will improve the understanding of the risk of applying natural organic fertilizer to barren loess soil, and provide theoretical basis and reference for the control of the triazine pesticides in soil.