Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

Despite their crucial roles in transporting primary productions in marine food webs, the trophic dynamics of zooplankton throughout the seasons have rarely been studied. In this study, four dominant zooplankton taxa with phytoplankton size composition and productivity were collected over four seasons in the East Sea, which is known to change more rapidly than global trends. We then analyzed the δ¹³C and δ¹⁵N values and fatty acid composition of zooplankton. The heavy δ¹³C values in February and August 2021 were observed with high concentrations of total chlorophyll-a, and the δ¹³C differences among the four zooplankton taxa in the coastal region (site 105-05) were most pronounced in February 2021. The relative amounts of eicosapentaenoic acid (C20:5(n-3)) and docosahexaenoic acid (C22:6(n-3)), indicators of phytoplankton nutritional quality, were also highest in February 2021. Non-metric multivariate analyses showed dissimilarity among zooplankton taxa during the high productivity period based on chlorophyll-a concentrations (51.6%), which may be due to an increase in available foods during the highly productive season. In conclusion, the dietary intake of zooplankton can be reduced by the transition of phytoplankton, which has important implications for the impact of climate change on planktonic ecosystems in the East Sea.

To broaden the range of measurable pesticides for stable isotope analysis (SIA), we tested whether SIA of the anthranilic diamides cyantraniliprole (CYN) and chlorantraniliprole (CHL) can be achieved under elemental analyzer/isotope ratio mass spectrometry with compound purification in high-performance liquid chromatography (HPLC). Using this method, carbon isotope compositions were measured in pesticide residues extracted from plants (lettuce) grown indoors in potting soil that were treated with 500 mg/kg CHL and 250 mg/kg CYN and were followed up for 45 days. Our results show that the CYN and CHL standard materials did not have significant isotope differences before and after clean-up processing in HPLC. Further, when applied to the CYN product and CHL product in soil, stable isotope differences between the soil and plant were observed at <1.0‰ throughout the incubation period. There was a slight increase in the variability of pesticide isotope ratio detected with longer-term incubation (CHL, on average 1.5‰). Overall, we measured the carbon isotope ratio of target pesticides from HPLC fraction as the purification and pre-concentration step for environmental and biological samples. Such negligible isotopic differences in pesticide residues in soils and plants 45 days after application confirmed the potential of CSIA to quantify pesticide behavior in environments.