Abstract
Spatial variability and source apportionment of river pollution flowing into the Bohai Sea are of great significance to the pollution liability and development of control strategies to reduce the terrestrial discharge of pollution in the ocean. In this study, ten water quality variables from 14 monitoring sites in rivers flowing into Laizhou Bay were obtained to investigate the spatial variation and pollution sources in Dongying District from 2018–2019. The survey area was divided into a low pollution (LP) zone and a high pollution (HP) zone by cluster analysis based on ten indicators. Principle component analysis/factor analysis with a geographic information system was performed to identify the four main pollution sources in the survey area. Compared with the positive matrix factorization model, the absolute principal component score-multiple linear regression (APCS-MLR) model was more appropriate for the source apportionment of pollution in the surface water of Dongying District. The point source pollution of domestic sewage (23.6%) was the most crucial pollution source of water in the LP zone, followed by non-point pollution from agricultural activity (16.4%). The contribution rate in the HP zone analyzed by the APCS-MLR model followed a decreasing order: point source pollution from domestic sewage (28.5%) > non-point pollution source of overland runoff (14.8%) > point source pollution of hybrid wastewater (12.4%) > point source pollution from industries sewage (10.6%). Therefore, the spatial distribution and sources of pollution in the investigated area should be considered while developing control measures to reduce the discharge of pollution to Laizhou Bay.
Highlights
The Bohai Sea, a semi-enclosed sea, is surrounded by land on three sides with poor water exchange conditions
1.88 to 14.9 mg/L, and the concentration of petroleum hydrocarbon (PHC) varied between 0.005 and 0.49 mg/L. These results indicate that the surface water in Dongying District was polluted to some degree despite the fact that pH, permanganate index (PI), and PHC in all samples satisfied grade IV according to the GB3838-2002 standard [19]
Multivariate statistical methods, including cluster analysis (CA) and principal component analysis (PCA)/factor analysis (FA), were us APCS-multiple linear regression (MLR) models are displayed in Figures S4 and S5 for the low pollution (LP) and high pollution (HP) zone, respectively
Summary
The Bohai Sea, a semi-enclosed sea, is surrounded by land on three sides with poor water exchange conditions. Numerous water pollution events have been reported in Laizhou Bay [1,2,3]. Little information is available in the literature on spatial variability and source apportionment of pollution in rivers flowing into Laizhou Bay. The current method to determine pollution liability is through the inspection of sewage outlets in China. It is impossible to identify the source of pollution if the underground sewage outlets are relatively concealed.
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