Validation of an Analytical Workflow for the Analysis of Pesticide and Emerging Organic Contaminant Residues in Paddy Soil and Rice

Contamination of agricultural soil with organic contaminants is a global problem due to the risks associated with food security and ecological sustainability. Besides the use of agrochemicals, hundreds of emerging contaminants enter arable lands through polluted irrigation water. In this study, an analytical workflow based on QuEChERS extraction coupled with LC–MS/MS quantification was applied to measure 65 emerging contaminants (42 pesticides and 23 multiclass industrial chemicals) in soil and rice for the first time. The method was validated on paddy and yard soil and rice plants. A recovery efficiency ranging between 70 and 120% (RSD <20%) was achieved for more than 70% of the analytes. Then, the validated method was used to quantify target contaminants in 22 soil and 9 rice samples collected mainly from paddy fields close to the Ergene River (Turkey), which is a highly polluted river used for irrigation in the region. Pesticide residues were present in all soil samples up to 2.4 mg/kg. However, their concentrations were below their maximum residual limits in rice. Azoxystrobin, prochloraz, propiconazole, imidacloprid, and epoxiconazole were the most frequently detected pesticides. In addition, industrial pollutants such as benzyldimethyldodecylammonium and tris(2-butoxyethyl) phosphate were detected in paddy soil samples at concentrations between 0.1 and 691 μg/kg. Benzyldimethyldodecylammonium and 5-methyl-1H benzotriazole were also measured in rice at concentrations up to 0.26 and 2.13 μg/kg, respectively.