Occurrence of trace organic contaminants in Bohai Bay and its adjacent Nanpaiwu River, North China

Concentrations of hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), pentachlorobenzene (penta-CB), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), coplanar polychlorinated biphenyls (co-PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDTs, including p,p′-DDT; o,p′-DDT; p,p′-DDD; o,p′-DDD; p,p′-DDE; o,p′-DDE; p,p′-DDMU), nonylphenol (NP), and nonylphenol polyethoxylates (NPEOs) were measured in sedimentary cores from Bohai Bay (one core) and its adjacent river, the Nanpaiwu River (two cores), North China. While α-, β-, and γ-HCHs were detected in similar abundance in the two cores from the Nanpaiwu River, only α-HCH was detected in the Bohai Bay core, suggesting that α-HCH might be more resistant to degradation than β- or γ-HCHs. The concentrations of HCHs and HCB in the core from Bohai Bay were in the range of 0.8-140 and 9.1-1300 ng/g dry wt, respectively, whereas in the cores from the Nanpaiwu River, the maximum concentrations of HCHs and HCB reached 84,200 and 141,400 ng/g dry wt, respectively. There was a similarity of sedimentary profiles between HCHs and HCB in the three cores. The concentration of PCDDs/DFs in Bohai Bay was 0.5-3.5 ng/g dry wt [1.6-6.4 toxic equivalents (TEQ) world health organization (WHO) pg/g], far lower than the concentrations in the core samples taken from the Nanpaiwu River (the maximum concentration: 9200 ng/g dry wt; 22,000 TEQ WHO pg/g). The congener profiles of PCDD/DFs and co-PCB in the cores were similar to those in PCP, and the concentration of co-PCBs was related to that of PCDDs/DFs. In addition, the concentrations of HCH, HCB, PCDD/Fs, and co-PCB all decreased linearly relative to total organic carbon content (TOC) in surface sediment from the river to Bohai Bay. The concentration of DDTs ranged from 1.6 to 12.3 ng/g dry wt in Bohai Bay, significantly different from the profiles from the Napaiwu River (29.3 ng/g dry wt). An abundance of the compounds o,p′-DDE and o,p′-DDD were detected in the cores. The sedimentary profiles of NP and NPEOs were similar, and two peak concentrations of NP/NPEOs were found at the subsurface and subbottom in the core from Bohai Bay, respectively. The concentration of NP and NPEOs in the cores from the Nanpaiwu River were about 15 times higher than those in the core from Bohai Bay, suggesting that the Nanpaiwu River was possibly one of the sources of NP and NPEOs in Bohai Bay.