Organochlorine compounds in European catfish (Silurus glanis) living in river areas under the influence of a chlor-alkali plant (Ebro River basin)

- Organochlorine compounds (OCs) were analysed in catfish from the Ebro River.
- The OC effluents from a chlor-alkali plant pollute the catfish of the last 100 km.
- The catfish from sites of lower water flows contain more lipid muscle content.
- OC concentrations are correlated to lipids in the catfish living in lower flow sites.
- Uniform PCB congener distributions were observed in the catfish from all Ebro sites.

European catfish, Silurus glanis, were used as sentinel organisms of the influence of recent and past discharges of organochlorine compounds (OCs) from a chlor-alkali plant located in the Ebro River. The fish concentrations of hexachlorobenzene (HCB), polychlorobiphenyls (PCBs) and DDTs were very high along the last 100 km of the river, including the irrigation channels, e.g. 1.2-27 ng/g wet weight of HCB, 6.3-100 ng/g ww of PCBs and 1-270 ng/g ww of total DDT compounds. These concentrations were much higher than those found upstream from the chlor-alkali discharge site, 0.2 ng/g ww for HCB, 5.6 ng/g ww for PCBs and 7.5 ng/g for DDT compounds. These concentrations were also standing out among those previously described in this fish species.The European catfish collected in sites under lower water flows, Ribarroja reservoir and irrigation channels, showed higher muscle lipid content, 1.09-7.2%, than those from sites of higher current intensities, river bed, 0.27%-0.67%. In these lower water current areas catfish exhibited OC ww concentrations that were correlated to % lipids. These differences suggest that normalization to lipid content is necessary for comparison of the OC accumulation in specimens from riverine systems living under different flow intensities. Accordingly, OC concentrations referred to lipid content showed more uniform downriver distribution which was consistent with a single focal point as main source of these compounds for the European catfish collected in the last 100 km of river stretch. This geographic distribution was also consistent with the uniform composition of PCB congeners in the studied European catfish.The distribution of DDT compounds was predominated by 4,4′-DDE which is common in most currently examined fish from aquatic environments. However, it included a high proportion of 4,4′-DDD and 2,4′-DDD which was consistent with the high contribution of benthic organisms from anoxic environments in the diet of these fish.