Modeling Of The Origin Of DDTs In Maricultured Fish And Its Geochemical Process In Mariculture-Based Bays

Fish is one of the most important nutrition sources for humanity.Contaminant exposure risk in fish farming will eventually deliver to the crowd through diet.China is the largest fish producing as well as exporting country,where mariculture plays an important role in fish production,especially in South China.Previous investigations indicated that a variety of compartments in farming areas of South China Sea were polluted by persistent organic pollutants,including DDT(dichlorodiphenyltrichloroethane)and its derivatives,some of which is designated as DDTs.In the present study,Hailing Bay and Daya Bay of Guangdong Province,China,were selected as the study sites and DDTs as the target compounds.A fish enrichment model was developed to assess the relative contributions of various pathways to the mass loadings of DDTs in the fish.Average concentrations(and concentration ranges)of DDTs in various environmental compartments of Hailing Bay and Daya Bay were included in modeling and analysis.Antifouling paint applied to fishing vessels is the primary source of dichloro–diphenyl–trichloroethane(DDT)to the coastal marine environments of China.With the aim to provide science–based support of potential regulations on DDT use in antifouling paint,we utilized a fugacity–based model to evaluate the fate and impact of p,p'–DDT,the dominant component of DDT mixture,in Daya Bay and Hailing Bay,two typical estuarine bays in South China.The emissions of p,p'–DDT from fishing vessels to the aquatic environments of Hailing Bay and Daya Bay were estimated as 9.3 and 7.7 kg yr1,respectively.Uncertainty analysis indicated that the temporal variability of p,p'–DDT was well described by the model if fishing vessels were considered as the only direct source,i.e.,fishing vessels should be the dominant source of p,p'–DDT in coastal bay areas of China.Estimated hazard quotients indicated that sediment in Hailing Bay posed high risk to the aquatic system,and it would take at least 21 years to reduce the hazards to a safe level.Moreover,p,p'–DDT tends to migrate from water to sediment in the entire Hailing Bay and Daya Bay.On the other hand,our previous research indicated that p,p'–DDT was more likely to migrate from sediment to water in the maricultured zones located in shallow waters of these two bays,where fishing vessels frequently remain.These findings suggest that relocating mariculture zones to deeper waters would reduce the likelihood of farmed fish contamination by p,p'–DDT.Overall,we suggest to use environment–friendly antifouling paint and apply less polluted fish food in the fish reproduction process in order to protect people from consuming highly contaminated maricuture zone fish.