National Institute of Agricultural Technology (INTA), Balcarce Experimental Station, Ruta Nac, 226, Km 73,5, CP 7620 Balcarce, Buenos Aires, Argentina.
National Institute of Agricultural Technology (INTA), Balcarce Experimental Station, Ruta Nac, 226, Km 73,5, CP 7620 Balcarce, Buenos Aires, Argentina; National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina.
Sci Total Environ. 2018 Sep 1;634:974-982. doi: 10.1016/j.scitotenv.2018.03.393. Epub 2018 Apr 11.
This study evaluates the glyphosate dissipation under field conditions in three types of soil, and aims to determine the importance of the following factors in the environmental persistence of herbicide: i) soil bacterial communities, ii) soil physicochemical properties, iii) previous exposure to the herbicide. A soil without previous record of GP application (P0) and two agricultural soils, with 5 and >10years of GP exposure (A5 and A10) were subjected to the application of glyphosate at doses of 3mg·kg. The concentration of GP and AMPA was determined over time and the dynamics of soil bacterial communities was evaluated using 16S ARN ribosomal gene amplicon-sequencing. The GP exposure history affected the rate but not the extent of GP biodegradation. The herbicide was degraded rapidly, but P0 soil showed a dissipation rate significantly lower than soils with agricultural history. In P0 soil, a significant increase in the relative abundance of Bacteroidetes was observed in response to herbicide application. More generally, all soils displayed shifts in bacterial community structure, which nevertheless could not be clearly associated to glyphosate dissipation, suggesting the presence of redundant bacteria populations of potential degraders. Yet the application of the herbicide prompted a partial disruption of the bacterial association network of unexposed soil. On the other hand, higher values of linear (Kd) and nonlinear (Kf) sorption coefficient in P0 point to the relevance of cation exchange capacity (CEC), clay and organic matter to the capacity of soil to adsorb the herbicide, suggesting that bioavailability was a key factor for the persistence of GP and AMPA. These results contribute to understand the relationship between bacterial taxa exposed to the herbicide, and the importance of soil properties as predictors of the possible rate of degradation and persistence of glyphosate in soil.
本研究评估了草甘膦在三种土壤类型中的田间条件下的消解情况，旨在确定以下因素在除草剂环境持久性中的重要性：i）土壤细菌群落，ii）土壤理化性质，iii）先前暴露于除草剂。选择一块没有先前使用草甘膦记录的土壤（P0）和两块有 5 年和>10 年草甘膦暴露史的农业土壤（A5 和 A10），施加 3mg·kg 的草甘膦剂量。随着时间的推移测定草甘膦和 AMAP 的浓度，并使用 16S ARN 核糖体基因扩增子测序评估土壤细菌群落的动态。草甘膦暴露史影响了草甘膦生物降解的速率，但不影响其程度。该除草剂被迅速降解，但 P0 土壤的降解速率明显低于具有农业历史的土壤。在 P0 土壤中，在施加除草剂后观察到厚壁菌门的相对丰度显著增加。更一般地，所有土壤都显示出细菌群落结构的变化，但这些变化不能明确与草甘膦的消解相关，这表明存在潜在的冗余细菌种群。然而，除草剂的应用促使未暴露土壤的细菌关联网络部分中断。另一方面，P0 土壤中较高的线性（Kd）和非线性（Kf）吸附系数值表明阳离子交换容量（CEC）、粘土和有机质对土壤吸附除草剂能力的重要性，这表明生物利用度是草甘膦和 AMAP 在土壤中持久性的关键因素。这些结果有助于理解暴露于除草剂的细菌类群之间的关系，以及土壤特性作为预测草甘膦在土壤中可能降解和持久性的重要性。
