Heavy metal pollution in the water and sediment of main estuaries into the sea in Changli County, Hebei Province

Heavy metals have been included as conventional indicators in various water quality tests and evaluations. In recent years, the coastal water quality in Changli County of Hebei Province has gradually deteriorated, increasing the risk of heavy metal pollution. The investigation on heavy metal pollution is of great significance for strengthening the environmental protection and management of the coastal water body in this region. In this study, the main estuaries in Changli County (Xinkai, Dapuhe, and Dongshahe estuaries) were considered as research objects. Water and surface sediment samples were collected in October 2019 during the normal water period, and the contents of eight heavy metals (Cd, Pb, Cu, Zn, As, Pb, Cr, and Ni) in the water and surface sediment samples were analyzed. The single-factor index method was used to evaluate the pollution status of heavy metals in water bodies. Geoaccumulation index and potential ecological pollution index methods were used to evaluate the status and risk of heavy metal pollution in surface sediments. The results show that the concentrations of the eight heavy metals in the water bodies of each estuary were different. The orders of heavy metal concentration was Ni>Cr>As>Pb>Zn>Cu>Hg>Cd in the Xinkai estuary, Ni>As>Cr>Pb>Zn>Cu>Hg>Cd in the Dapuhe estuary and Ni>Cr>As>Zn>Pb>Cd>Hg>Cu in the Dongshahe estuary. The concentrations of the eight heavy metals in the estuaries differed greatly, where Ni concentration was the highest. Compared with the limit of the second type of water quality standard in the Sea Water Quality Standard (GB 3097—1997), the Ni content in the three estuaries reached heavy pollution. Pb pollution in the Xinkai and Dapuhe estuaries was heavy and light, respectively, and Pb in the Dongshahe estuary did not exceed the standard. Cr pollution in the Xinkai estuary was mild, and no pollution was found for Cd, Hg, Cu, Zn, and As. Among the heavy metals detected in the sediments, Cd was at a moderate pollution level in the three estuaries with the highest potential ecological risk coefficients of 160.71, 171.43, and 150.00 for the Xinkai, Dapuhe, and Dongshahe estuaries, respectively, indicating a high risk. Cu and Ni pollution in the sediments of the Dapuhe estuary and Dongshahe estuary were low, and Pb pollution in the sediments of the Xinkai estuary was also low. The comprehensive index of potential ecological risk showed that the Xinkai, Dapuhe, and Dongshahe estuaries were at moderate risk. From the perspective of the contribution rate of heavy metals, the contribution rate of Cd was the highest and should be given sufficient attention. A comprehensive study showed that heavy metal pollution exists in the main estuary of Changli County, which is at a level of moderate potential ecological risk. In response to the heavy metal pollution situation at the main sea inlets of Changli County, we call on the local government to take multiple measures, combine prevention and control, protect the marine environment in the region, and achieve sustainable development of marine resources in the region.