Sources and ecotoxicological risk indices of OCP and PCBs residues in Shalateen sediments, Red Sea, Egypt

Ninety-three sediments collected from Shalateen City (Red Sea, Egypt) were analyzed using a triple quadrupole mass spectrometer (MS/MS) in selective reaction monitoring (SRM) mode for extremely sensitive and selective detection and quantification of organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) after separating them using a gas chromatograph (GC). The residual average values of 10.91, 10.86, and 0.89 ng g^-1 dry wt. were recorded for hexachlorocyclohexane (HCHs), cyclodienes (Cs), and dichloro diphenyl trichloro ethane (DDTs), respectively. α-HCH, β-HCH, γ-HCH, and δ-HCH were averaged 1.37, 2.82, 3.25, and 3.47 ng g^-1, respectively. This indicates that the majority of α-HCH in the sediments of the studied area has transformed into δ-HCH. Furthermore, an average ratio of 0.40 was recorded for α-HCH/γ-HCH ratio, suggesting that the Shalateen environment does not receive any fresh HCH inputs. The degraded forms of p,p'-dichlorodiphenyldichloroethane and p,p'-dichlorodiphenyldichloroethylene, p,p'-DDD and p,p'-DDE were more prevalent with 0.31 and 0.49 ng g^-1, respectively, than their parent p,p'-DDT's with 0.09 ng g^-1. This reflects the weathered sources of DDT in Shalateen. The concentrations of eighteen PCB congeners varied from ND (below the limit of detection) to 6085.78, with an average of 407.23 ng g^-1 dry wt., far above the permissible level, indicating their toxic impacts via industrial activities. The present investigation found that, except for lindane (γ-HCH), which is widely used in the area, all organochlorine pesticide residues were safe at levels below the Sediment Quality Guidelines (SQG).