Abstract：
The quantification of pesticide dissipation in agricultural soil is challenging. In this study, we investigated atrazine biodegradation in both liquid and soil experiments bioaugmented with distinct atrazine-degrading bacterial isolates. This was achieved by combining 14C-mineralisation assays and compound-specific isotope analysis of atrazine. In liquid experiments, the three bacterial isolates mineralised over 40% of atrazine, demonstrating their potential for extensive degradation. However, the kinetics of mineralisation and degradation varied among the isolates. Carbon stable isotope fractionation was similar for Pseudomonas isolates ADPT34 and ADP2T0, but slightly higher for Chelatobacter SR27. In soil experiments, atrazine primarily degraded into atrazine-desethyl, while atrazine-hydroxy was mainly observed in experiments with SR27. Atrazine mineralisation in soil by ADPT34 and SR27 exceeded 40%, whereas ADP2T0 exhibited a mineralisation rate of 10%. In experiments with ADPT34 and SR27, atrazine 14C-residues were predominantly found in the non-extractable fraction, whereas they accumulated in the extractable fraction in the experiment with ADP2T0. Compound-specific isotope analysis (CSIA) relies on changes of stable isotope ratios and holds potential to evaluate herbicide transformation in soil. CSIA of atrazine indicated atrazine biodegradation in water and solvent extractable soil fractions and varied between 29% and 52%, depending on the bacterial isolate. Despite atrazine degradation in both soil fractions, a significant portion of atrazine residues persisted, depending on the bacterial degrader, initial cell concentration, and mineralisation and degradation rates. Overall, our approach can aid in quantifying atrazine persistence and degradation in soil, and in optimizing bioaugmentation strategies for remediating soils contaminated with persistent herbicides.
摘要：
农业土壤中农药耗散的量化具有挑战性。在这项研究中,我们在液体和土壤实验中研究了用不同的降解阿特拉津的细菌分离株生物增强的阿特拉津生物降解。这是通过结合14C矿化测定和阿特拉津的化合物特异性同位素分析来实现的。在液体实验中,这三种细菌分离物矿化了40%以上的阿特拉津，展示了它们广泛退化的潜力。然而,矿化和降解的动力学在分离物中有所不同。假单胞菌分离株ADPT34和ADP2T0的碳稳定同位素分馏相似，但螯合杆菌SR27的碳稳定同位素分馏略高。在土壤实验中,阿特拉津主要降解为阿特拉津-去乙基，而在SR27实验中主要观察到阿特拉津-羟基。ADPT34和SR27在土壤中的阿特拉津矿化超过40％，而ADP2T0的矿化率为10%。在ADPT34和SR27的实验中，阿特拉津14C-残留物主要存在于不可萃取的部分中，而它们在ADP2T0实验中积累在可萃取部分中。化合物特异性同位素分析（CSIA）依赖于稳定同位素比率的变化，并具有评估土壤中除草剂转化的潜力。阿特拉津的CSIA表明阿特拉津在水和溶剂可提取的土壤部分中可生物降解，在29％至52％之间变化，取决于细菌分离。尽管阿特拉津在两个土壤部分都有降解，相当一部分阿特拉津残留物持续存在，取决于细菌降解剂，初始细胞浓度，以及矿化和降解率。总的来说,我们的方法可以帮助量化阿特拉津在土壤中的持久性和降解，以及优化修复被持久性除草剂污染的土壤的生物强化策略。
