『Abstract
　Air, rain, pond water, bank soil, pond sediment, fish feed, and fish were sampled from four freshwater cultured fish ponds (FWXFPs) in rural areas within the Pearl River Delta (PRD) of South China. Compositional analyses indicated that historical residues were the main sources of DDXs (defined as the sum of dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD), and dichlorodiphenyldichloroethylene (DDE) and 1-chloro-2,2-bis (4-chlorophenyl) ethane (p,p'-DDMU)), and hexachlorocyclohexanes (HCHs) in the FWCFPs. The input fluxes to the FWCFPs were estimated at 4.0, 1.6, 15, and -0.92μg/m²・year for DDXs and 3.8, 0.92, 2.9, and -1.4μg/m²・year for HCHs for dry deposition, wet deposition, feeding, and net air-water exchange in Dongguan, and 3.8, 1.2, 137, and -1.2μg/m²・year for DDXs and 3.6, 0.66, 5.0, and -1.0μg/m²・year for HCHs in Shunde, respectively. These results indicated that fish feed was the dominant input source of DDXs to the FWCFPs. As for HCHs, fluxes via dry deposition and feeding were similar and slightly higher than those via wet deposition. Biological effects due to the occurrence of DDXs in the FWCFPs were minimal, and consumption of freshwater fish from the PRD appeared to pose insignificant risk to human health based on some existing regulations and guidelines.

Keywords: Organochlorine pesticides; Freshwater cultured fish pond; Input fluxes; Potential biological effect; South China』

Introduction
Materials and methods
　Sample collection
　Sample preparation and extraction
　Instrumental analysis
　Quality assurance/control
Results and discussion
　Levels of OCPs in the FWCFP ecosystem}
　Source assessment of DDX and JCH congeners
　Estimated fluxes of DDXs and HCHs to FWCFPs
　Potential biological effects of DDTs in FWCFPs
Conclusions
Supplemental data
References