The flow-diverted Nechako River is the second largest tributary of the Fraser River which drains 25% of mainland British Columbia, Canada. The watershed provides critical reproductive habitats for anadromous chinook salmon (Oncorhynchus tshawytscha) and sockeye salmon (O. nerka) and year-round habitat for the endangered Nechako white sturgeon (Acipenser transmontanus) population. In this study, the chemical quality of sediment in the upper Nechako River and its major tributaries was examined for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), legacy organochlorine (OC) pesticides, polycyclic aromatic hydrocarbons (PAHs), organophosphorus and phenoxy acid herbicides, polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs), labile (exchangeable) metals/metalloids, and major nutrients (N and P). ΣPCB and ΣPBDE were detected in channel bottom sediments at all Nechako River and tributary sites; hexachlorobenzene (HCB) and 4,4′-DDE (dichlorodiphenyldichloroethylene) were also detected at most sites. Organophosphorus and phenoxy acid herbicides were not detected in any samples. While ΣPCB, ΣPBDE, HCB, and 4,4′-DDE concentrations in bottom sediments were always well below provincial and federal guidelines for the protection of aquatic life, concentrations of total labile As (As_T), Cr_T, Cu_T, Fe_T, Mn_T, Ni_T, and Zn_T in suspended and/or bottom sediments often exceeded provincial threshold effect levels (TEL) and, in some cases, approached or exceeded probable effect levels. Distinct Cu_T, Ni_T, Pb_T and Zn_T concentration maxima in suspended sediments were linked to road and urban densities. Historical PCDD, PCDF and PAH data show that concentrations in bottom sediment samples were highest at a site in the lower Nechako River between Miworth and the City of Prince George where PCDD and PCDF concentrations exceeded the interim federal TEL. Nitrogen and P concentrations in bottom sediments were negatively correlated with water velocity and sediment texture; the evidence suggests that reductions in velocity resulting from the 1952 diversion of the Nechako River have increased the nutrient content of bottom substrates.

分流的内恰科河是弗雷泽河的第二大支流，排泄了加拿大不列颠哥伦比亚省大陆的25％。该分水岭为过时的奇努克鲑（Oncorhynchus tshawytscha）和红鲑（O. nerka）提供了重要的繁殖栖息地，为濒危的Nechako白st（Acipenser transmontanus）种群提供了全年的栖息地。在这项研究中，检查了内查科河上游及其主要支流的沉积物的化学质量，包括多氯联苯（PCBs），多溴联苯醚（PBDEs），传统有机氯（OC）农药，多环芳烃（PAHs），有机磷和苯氧基羧酸类除草剂，多氯联苯二苯并p-二恶英（PCDDs）和呋喃（PCDFs），不稳定的（可交换的）金属/准金属和主要营养素（氮和磷）。在所有内恰科河和支流点的河道底部沉积物中都检测到了ΣPCB和ΣPBDE；在大多数地点还检测到六氯苯（HCB）和4,4'-DDE（二氯二苯基二氯乙烯）。在任何样品中均未检出有机磷和苯氧基除草剂。虽然底部沉积物中的ΣPCB，ΣPBDE，HCB和4,4'-DDE的浓度始终始终低于保护水生生物的省和联邦准则，但总不稳定As（As _T），Cr _T，Cu _T，Fe的总浓度_Ť，锰_Ť，镍_Ť和Zn _Ť悬浮和/或底部沉积物中的污染物通常超过省级阈值影响水平（TEL），在某些情况下接近或超过可能的影响水平。独特的Cu _T，Ni _T，Pb _T和Zn _T悬浮沉积物中的最大浓度与道路和城市密度有关。PCDD，PCDF和PAH的历史数据表明，在米沃斯和乔治王子市之间的内恰科河下游，PCDD和PCDF的浓度超过了联邦临时TEL，其底部沉积物样品的浓度最高。底部沉积物中氮和磷的含量与水流速度和沉积物质地呈负相关。有证据表明，1952年涅恰科河（Nechako River）改道导致流速降低，增加了底质的养分含量。