Polychlorinated biphenyls and organochlorine pesticides in surface sediments from river networks, South Korea: Spatial distribution, source identification, and ecological risks.

In this study, the nationwide monitoring of 65 polychlorinated biphenyls (PCBs) and 23 organochlorine pesticides (OCPs) in surface sediments was conducted at 77 sites in river networks in South Korea. The concentrations of ∑PCBs were relatively high in industrial sites (0.0297-138 ng/g dry weight (dw); mean 15.1 ng/g dw; median 5.44 ng/g dw), followed by industrial and agricultural (not detected (ND)-15.2 ng/g dw; mean 1.23 ng/g dw; median 0.513 ng/g dw), other sites (0.0369-0.209 ng/g dw; mean 0.116 ng/g dw; median 0.101 ng/g dw), and agricultural (0.0119-0.359 ng/g dw; mean 0.117 ng/g dw; median 0.0476 ng/g dw). The distribution and composition of PCBs in sediments are affected by past use of commercial products, atmospheric deposition, wastewater effluents, and manufacturing processes. The concentrations of ∑OCPs in industrial sites ranged from 0.0587 to 8.70 ng/g dw (mean 1.85 ng/g dw; median 0.989 ng/g dw), followed by industrial and agricultural (ND-8.54 ng/g dw; mean 0.739 ng/g dw; median 0.343 ng/g dw), other sites (0.0247-0.143 ng/g dw; mean 0.0939 ng/g dw; median 0.114 ng/g dw), and agricultural (0.00838-0.931 ng/g dw; mean 0.232 ng/g dw; median 0.0752 ng/g dw). Hexachlorobenzene and pentachlorobenzene are unintentionally generated in industries and combustion processes. Dichlorodiphenyltrichloroethanes and chlordane were dominantly distributed by historical use, whereas recent inputs (i.e., long-range transport and atmospheric deposition) were related to aldrin, heptachlor, and hexachlorocyclohexanes. The ecological risks determined by the sediment quality guidelines and mean probable effect level quotients were acceptable, except at two sites.

Simultaneous multi-residue analytical method for anesthetics and sedatives in seafood samples by LC-ESI/MSMS.

A simultaneous multi-residue analytical method for 27 regulated and unregulated anesthetics and sedatives in seafood using liquid chromatography/tandem mass spectrometry with electrospray ionization (LC-ESI/MSMS) was developed and tested on flatfish, eels, and shrimp. To optimize the efficiency of the method, extraction and clean-up procedures with various solvents and sorbents were tested. The most efficient pretreatment methods were extraction using acetonitrile (ACN) only (for flatfish and eel) and 0.1 % ammonium acetate in ACN (for shrimp). Validation was performed under the guidelines of CODEX Alimentarius (CAC/GL-71) and the Korean National Institute of Food and Drug Safety Evaluation (NIFDS). The limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision for all compounds ranged from 0.0002 to 0.002 mg/kg, 0.0005-0.005 mg/kg, 64.7-112.5 %, and 1.0-8.6 %, respectively. The coefficient of determination (linearity, R2) was over 0.98. Therefore, the method meets the requirements of both the domestic and international guidelines.

Residue Monitoring and Risk Assessment of Cyazofamid and Its Metabolite in Korean Cabbage Under Greenhouse Conditions.

The residual characteristics and risk assessment with respect to cyazofamid and its metabolite 4-chloro-5-p-tolylimidazole-2-carbonitrile were monitored in case of Korean cabbage at different preharvest intervals during a greenhouse trial. The 0.02 kg a.i/ha of cyazofamid was sprayed twice on seven-day intervals (i.e., on day 0, 7, 14, and 21 before harvest). The liquid chromatography-tandem mass spectrometry analysis was used to monitor the residual amount of fungicide. The matrix-matched calibration curves with respect to the cyazofamid in Korean cabbage exhibited good linearity (R2 ≥ 0.999) and acceptable recoveries of 84.1%-114.9%. The biological half-life of cyazofamid in Korean cabbage was 3.18 days. During the treatment, the preharvest residue of cyazofamid in Korean cabbage 14 days before harvest (0.80 mg/kg) was lower than that specified by the MFDS-MRL (Ministry of Food and Drug Safety-Maximum Residue Limit, 2.0 mg/kg) and should be recommended as the safe preharvest-interval application limit. The hazard quotient showed low toxicity (70.58%) during the risk assessment study of cyazofamid.