Centre for Hydrogeology and Geothermics (CHYN), University of Neuchâtel, Rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland.
Neuchâtel Platform of Analytical Chemistry (NPAC), University of Neuchâtel, Avenue de Bellevaux 51, CH-2000 Neuchâtel, Switzerland.
J Chromatogr A. 2021 Oct 11;1655:462507. doi: 10.1016/j.chroma.2021.462507. Epub 2021 Aug 28.
Pesticide metabolites are frequently detected in groundwater at concentrations often exceeding those of their parent pesticides. A well-known example is the metabolites of chlorothalonil, a non-systematic, broad spectrum fungicide. Some of the chlorothalonil metabolites occur frequently and at elevated concentrations in groundwater, which is why the use of chlorothalonil was recently banned in the European Union. To estimate the long-term evolution of the concentration of the chlorothalonil metabolites in groundwater after this ban, it is important to know if metabolite residues in soil and unsaturated zone can affect the concentrations in groundwater. We developed and validated a method for the determination of 5 chlorothalonil metabolites in soil (R471811, R417888, SYN507900, SYN548580 and R611968), including those which are frequently detected in groundwater. The developed protocols, based on a solid phase extraction approach (for R471811, R417888, SYN507900, SYN548580) or a QuEChERS approach (for R611968) followed by UHPLC-MS/MS analysis, provided excellent sensitivity (LOQ of 0.5 µg/kg for all metabolites), precision (RSD<10 % at low, medium and high concentrations) and accuracy (84-115 %). In addition, we developed a simple but highly sensitive (LOQ of 5-10 ng/L) direct-injection method for the analysis of these 5 metabolites in water to compare their occurrence in soil and groundwater. The application of these methods to agricultural soil samples and groundwater samples showed that the detection frequency of the 5 chlorothalonil metabolites in soil and groundwater seems to be inversed and dependent on their sorption coefficient. The latter might control the amount of the chlorothalonil metabolites which is retained in the soil or which leaches towards groundwater. Our results provide insights to estimate the retention of the different chlorothalonil metabolites in soil and unsaturated zone and therefore, to assess the influence of the soil and unsaturated zone on the long-term concentration evolution of these metabolites in groundwater.
农药代谢物经常在地下水中被检测到，其浓度常常超过其母体农药。氯噻啉的代谢物就是一个众所周知的例子，它是一种非系统性、广谱杀菌剂。氯噻啉的一些代谢物经常在地下水中以较高的浓度出现，这也是为什么氯噻啉最近在欧盟被禁用的原因。为了估计在禁用氯噻啉后，地下水中氯噻啉代谢物浓度的长期演变情况，了解土壤和非饱和带中代谢物残留是否会影响地下水浓度非常重要。我们开发并验证了一种用于测定土壤中 5 种氯噻啉代谢物（R471811、R417888、SYN507900、SYN548580 和 R611968）的方法，包括那些经常在地下水中检测到的代谢物。该方法基于固相萃取法（用于 R471811、R417888、SYN507900、SYN548580）或 QuEChERS 法（用于 R611968），随后进行 UHPLC-MS/MS 分析，该方法提供了极好的灵敏度（所有代谢物的 LOQ 为 0.5 µg/kg）、精密度（低、中、高浓度下的 RSD<10%）和准确度（84-115%）。此外，我们还开发了一种简单但高度灵敏的（水中 5 种代谢物的 LOQ 为 5-10 ng/L）直接进样方法，用于分析土壤和地下水中这些代谢物的存在情况，以比较它们在土壤和地下水中的出现情况。将这些方法应用于农业土壤样品和地下水样品表明，土壤和地下水中 5 种氯噻啉代谢物的检测频率似乎相反，且取决于它们的吸附系数。后者可能控制了氯噻啉代谢物在土壤中保留或向地下水淋滤的量。我们的研究结果提供了关于估计不同氯噻啉代谢物在土壤和非饱和带中保留的见解，因此可以评估土壤和非饱和带对这些代谢物在地下水中长期浓度演变的影响。
