Abstract：
Pesticide degradation in wetland systems intercepting agricultural runoff is often overlooked and mixed with other dissipation processes when assessing pesticide concentrations alone. This study focused on the potential of compound-specific isotope analysis (CSIA) to estimate pesticide degradation in a stormwater wetland receiving pesticide runoff from a vineyard catchment. The fungicide dimethomorph (DIM), with diastereoisomers E and Z, was the prevalent pesticide in the runoff entering the wetland from June to September 2020. DIM Z, the most commonly detected isomer, exhibited a significant change (Δ(13C) > 3 ‰) in its carbon isotopic composition in the wetland water compared to the runoff and commercial formulation, which indicated degradation. Laboratory DIM degradation assays, including photodegradation and biodegradation in oxic wetland water with and without aquatic plants and in anoxic sediments, indicated that DIM degradation mainly occurred in the wetland sediments. The rapid degradation of both DIM isomers (E:t1/2 = 1.2 ± 0.6, Z: t1/2 = 1.5 ± 0.8 days) in the wetland sediment led to significant carbon isotopic fractionation (εDIM-E = -3.0 ± 0.6 ‰, εDIM-Z = -2.0 ± 0.2 ‰). In contrast, no significant isotope fractionation occurred during DIM photodegradation, despite the rapid isomerization of the E isomer to the Z isomer and a half-life of 15.3 ± 2.2 days for both isomers. DIM degradation was slow (E: t1/2 = 56-62 days, Z: t1/2 = 82-103 days) in oxic water with plants, while DIM persisted (120 days) in water without plants. DIM CSIA was thus used to evaluate the in situ biodegradation of DIM Z in the wetland. The DIM Z degradation estimates based on a classical concentration mass balance (86-94 %) were slightly higher than estimates based on the isotopic mass balance (61-68 %). Altogether, this study shows the potential of CSIA to conservatively evaluate pesticide degradation in wetland systems, offering a reliable alternative to classical labor-intensive mass balance approaches.).
摘要：
在仅评估农药浓度时，通常会忽略拦截农业径流的湿地系统中的农药降解，并与其他耗散过程混合在一起。这项研究的重点是化合物特异性同位素分析（CSIA）在接收葡萄园流域农药径流的雨水湿地中估算农药降解的潜力。杀菌剂烯酰吗啉（DIM），与非对映异构体E和Z，是2020年6月至9月进入湿地的径流中普遍存在的农药。DIMZ,最常见的异构体，与径流和商业配方相比，湿地水中的碳同位素组成发生了显着变化（Δ（13C）>3‰），这表明退化。实验室DIM降解测定，包括在有和没有水生植物的有氧湿地水中和缺氧沉积物中的光降解和生物降解，表明DIM降解主要发生在湿地沉积物中。湿地沉积物中两种DIM异构体(E:t1/2=1.2±0.6,Z:t1/2=1.5±0.8天)的快速降解导致显著的碳同位素分馏(εDIM-E=-3.0±0.6‰,εDIM-Z=-2.0±0.2‰)。相比之下,在DIM光降解过程中没有发生明显的同位素分馏，尽管E异构体快速异构化为Z异构体，两种异构体的半衰期为15.3±2.2天。DIM降解缓慢（E：t1/2=56-62天，Z：t1/2=82-103天）在含植物的含氧水中，而DIM在没有植物的水中持续（120天）。因此，DIMCSIA用于评估DIMZ在湿地中的原位生物降解。基于经典浓度质量平衡的DIMZ降解估计值（86-94％）略高于基于同位素质量平衡的估计值（61-68％）。总之,这项研究显示了CSIA保守评估湿地系统中农药降解的潜力，为经典的劳动密集型质量平衡方法提供了可靠的替代方案。).
