Occurrence of 17 polycyclic aromatic hydrocarbons (PAHs) and 15 persistent organochlorine pesticides (OCPs) were analyzed by gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) during the spring and summer of 2015 in surface water at 14 sampling sites in the mainstream of the Luanhe River to elucidate their seasonal distribution, composition, and potential sources. Results showed that total PAH concentrations in the surface water of the Luanhe River ranged from 33.33 ng·L-1 to 90.65 ng·L-1(52.64 ng·L-1 in average) in spring and 147.68 ng·L-1 to 252.68 ng·L-1 (169.88 ng·L-1 in average) in summer, respectively, and total concentrations of OCPs ranged from <0.08 ng·L-1 to 3.48 ng·L-1 (1.19 ng·L-1 in average) in spring and <0.08 to 5.47 ng·L-1(1.02 ng·L-1 in average) in summer, respectively. Seasonal pollution characteristics of PAHs in surface water during two different seasons showed that total PAH concentrations were much higher in summer than in spring at each sampling site on the Luanhe River. While seasonal pollution characteristics of OCPs showed that total OCP concentrations were much lower in spring than in summer at six sites including Luanxian, Daheiting reservoir dam, Panjiakou Village, Guojiatun, Qujiawan, and Baichengzi, and were higher in spring than in summer at the remaining eight sites. From the perspective of spatial and temporal variations in the composition patterns of PAHs and OCPs in surface water of the Luanhe River, the low and middle ring species of PAHs were dominant in spring and summer and the proportion of PAHs with different rings showed significant differences. Three-ring PAHs dominated the samples with 51.18% and 67.55% (61.39% on average) of total PAHs in spring, and four-ring and two-ring PAHs accounted for 11.78%-33.94% (20.97% on average) and 13.31%-27.12% (16.94% on average), respectively. In the summer, In the summer, naphthalene(Nap) was the main component of total PAHs at each sampling site and PAHs were predominated by two-ring compounds with 77.08% and 90.62% (83.34% on average) of the total, and by three-ring and four-ring compounds with 7.09%-15.22% (12.40% on average) and 2.23%-7.49% (3.97% on average), respectively. Only the residues of hexachlorocyclohexanes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs) were detected in surface water of the Luanhe River at different degrees and HCHs were the dominant compounds. β-HCH was the main pollutant at most sampling sites with 43.78% and 70.09% (56.25% on average) of total HCHs in the spring and with 53.63% and 64.31% (58.37% on average) in the summer. α-HCH and γ-HCH were abundant at other sampling sites. Source analysis based on the isomer ratios indicated that PAHs in the Luanhe River mainly originated from combustion sources and also likely from petroleum processes. Ratios of OCPs confirmed that historical residues and long-range atmospheric transport were the major sources of HCHs in the study area, and new sources of lindane or γ-HCH existed at Wulongji and Sandaohezi in the spring and Daheting reservoir dam in the summer. Fresh inputs at the Panjiakou reservoir dam, Sandaohezi, Waigoumenzi, Baichengzi, Zhenglanqi, and the Shandianhe reservoir, and environmental residues at Jianggezhuang and Guojiatun were the major sources of DDTs. Concentrations of single PAHs in surface water of the Luanhe River did not exceed the water quality standards of China and other countries except that chrysene(Chr) exceeded the United States national water quality standard. Individual PAHs did not exceed any safety guidelines for aquatic organisms that are exposed to PAHs in water but total concentrations of PAHs exceeded the threshold limits set by the United States Environmental Protection Agency (EPA) and the European Union. This result indicated that consuming fish and other aquatic animals might pose a potential threat to human health due to the bioaccumulation of PAHs in aquatic organisms. The concentrations of OCPs in surface water of the Luanhe River did not exceed any water quality standards or the aquatic life threshold limits for freshwater developed by the EPA. However, the concentrations of α-HCH at Jianggezhuang, Wulongji, Qujiawan, and Baichengziand sites in the spring and at the Panjiakou reservoir dam, Panjiakou village, Qujiawan, and Baichengzi sites in the summer, and concentrations of p,p'-DDD at the Shandianhe reservoir and p,p'-DDE at Jianggezhuang, Sandaohezi, Guojiatun, and Shandianhe reservoir in the spring exceeded the human health ambient water quality criteria limit developed by the EPA. This result suggests that α-HCH, p,p'-DDE, and p,p'-DDD pose a potential health risk to the residents who live near the sampling sites on the Luanhe River.
Keywords: Luanhe River; composition; distribution; organochlorine pesticides; polycyclic aromatic hydrocarbons; source apportionment.