Suspecting screening "known unknown" pesticides and transformation products in soil at pesticide manufacturing sites

The occurrence and risks of pesticides and their transformation products in soil at the manufacturing sites are "known unknowns." In this study, pesticides and their transformation products were screened in soil at 6 pesticide manufacturing sites across China using liquid and gas chromatography coupled with quadrupole time-of-flight mass spectrometry. The screening strategy can correctly identify 75% of 209 pesticides spiked at 50 ng g(-1). A total of 212 pesticides were identified; 23.1% of pesticides detected were above 200 ng g(-1) , and the maximum concentration was 1.5 x 10(5) ng g(-1). The risk quotients of 20% pesticides were greater than 1, and the maximum risk quotient of imidacloprid reached 6.3 x 10(4). The most recent site showed a larger number of pesticides with higher diversity, whereas older sites were dominated by organochlorine insecticides.The extended screen identified 163 transformation products with concentrations up to 6.6 x 10(4) ng g(-1). Half of the transformation products had higher concentrations than their parent compounds, and metabolic ratios up to 371 were observed. The results of this study validate the prevalence of pesticides and their transformation products in soil at pesticide manufacturing sites. The results also highlight the importance of comprehensive screening at industrial sites and call for improved management and regulation of pesticide manufacturing, particularly for in-service facilities.