TROPICAL GEOGRAPHY ›› 2019, Vol. 39 ›› Issue (3): 337-346.doi: 10.13284/j.cnki.rddl.003141

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Occurrence, Distribution and Source Analysis of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Waters of the Lianzhou Bay and Sanniang Bay, Guangxi

Wang Weiquan1,2, Zhang Ruijie2, Yu Kefu2, Wang Yinghui2, Pan Changgui2 and Zeng Weibin1,2   

  1. (1. College of Resources, Environment and Materials,Guangxi University, Nanning 530004, China; 2. Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Coral Reef Research Center, School of Marine Sciences, Nanning 530004, China)
  • Received:2019-02-22 Revised:2019-04-10 Online:2019-05-05 Published:2019-05-05

Abstract:

Concentrations of 16 PAHs in 14 surface seawater samples were analyzed with solid phase extraction and gas chromatography-mass spectrometry. These samples were collected from estuaries and coasts of the Lianzhou Bay and Sanniang Bay in summer and winter. The results show that the average concentrations of individual PAHs were positively correlated with their solubilities and polarities. Two- and three-ring PAHs were the predominant compounds, with higher detection rates and concentrations than PAHs with 4-6 rings. In summer, the mean of ∑16PAHs (total concentration of 16 PAHs) was significantly higher in the estuaries (72.71 ng/L) than at the coast (56.28 ng/L) (t-test, p<0.01). In winter, the means of ∑16PAHs between estuaries (106.67 ng/L) and the coastal zone (92.43 ng/L) were not significantly different (t-test, p>0.05). The average ∑16PAHs for both estuaries and coast were significantly higher in winter than in summer (t-test, p<0.05). The concentrations of the 2-ring and 3-ring PAHs exceeded 97% of the ∑16PAHs. The proportion of 2-ring PAHs was significantly higher in winter (85%-86%) than in summer (68%-69%), while the proportion of 3-ring PAHs was higher in summer (29%) than in winter (14%). In either season, the proportions of PAHs in the estuaries and coastal waters were similar, indicating that they have the same source, and that the rivers have a significant impact on coastal pollution. In summer, ∑16PAHs was higher in the Nanliu River (74.98 ng/L) than in the Dafeng River (58.92 ng/L); while in winter the ∑16PAHs in the Dafeng River (154.94 ng/L) were significantly higher than in the Nanliu River (90.58 ng/L). In summer, the ∑16PAHs was higher in Sanniang Bay (56.62 ng/L) than in Lianzhou Bay (55.93 ng/L). In winter, the ∑16PAHs in the Sanniang Bay and Lianzhou Bay were both about 90 ng/L, which were 1.5 and 1.7 times higher than their corresponding concentrations in the summer. Whether in summer or winter, the PAHs in Sanniang Bay and Lianzhou Bay mainly consisted of 2-ring and 3-ring PAHs, accounting for over 90% of the total. Five-ring PAHs were only detected in Sanniang Bay. The total flux of 16 PAHs in the two rivers was 525.3 kg/a. The rainy season contributed more than 85% of the total flux, reflecting the apparent impact of the rivers on the coast during the rainy season. The Nanliu River discharged more than 87% of the total flux of the 16 PAHs for the two rivers, because of its massive runoff. The results of source analysis using principal component analysis and isomer ratio analysis both showed that the PAHs in the surface waters of Sanniang Bay and Lianzhou Bay were from mixed sources of combustion and petroleum in summer, but mainly from combustion sources in winter. Compared with other countries or regions worldwide, the levels of PAHs in Lianzhou Bay and Sanniang Bay were moderate. The ecological risk assessment results showed that the ecological risk from the PAHs in this study was low.

Key words: PAHs, seawater, distribution and source, ecological risk, estuary, coast, the Lianzhou Bay, the Sanniang Bay