Distribution of heavy metals in coastal sediments under the influence of multiple factors: A case study from the south coast of an industrialized harbor city (Tangshan, China)

Abstract

This research investigated the spatial distribution of heavy metals, including mercury (Hg), cadmium (Cd), copper (Cu), arsenic (As), nickel (Ni), lead (Pb), chromium (Cr), and zinc (Zn), in surface sediments from a coastal area near to an industrial harbor (Tangshan Harbor, China) using 161 sediment samples. According to the geo-accumulation index (Igeo), 11 samples were classified as unpolluted (Igeo≤0). Notably, 41.0 % of the research samples were moderately or strongly polluted (2 < Igeo≤3) with Hg and 60.2 % of the samples were moderately polluted (1 < Igeo≤2) in Cd. The ecological effect evaluation showed that the metals Zn, Cd, and Pb were at the effect range low level, and 51.6 % of the samples for Cu, 60.9 % for Cr, 90.7 % for As, 41.0 % for Hg, and 64.0 % for Ni fell in the range between the effect range-low and the effect range-mean levels, respectively. The correlation analysis showed that the distribution patterns of Cr, Cu, Zn, Ni, and Pb were similar to each other, high in the northwest, southeast, and southwest regions of the study area and low in the northeast region, which corresponded well with sediment size components. Based on principal component analysis (PCA) and positive matrix factorization (PMF), four distinct sources of pollution were quantitatively attributed, including agricultural activities (22.08 %), fossil fuel consumption (24.14 %), steel production (29.78 %), and natural sources (24.00 %). Hg (80.29 %), Cd (82.31 %) and As (65.33 %) in the region's coastal sediments were predominantly contributed by fossil fuel, steel production and agricultural sources, respectively. Cr (40.00 %), Cu (43.63 %), Ni (47.54 %), and Zn (38.98 %) were primarily of natural lithogenic origin, while Pb mainly came from the mixed sources of agricultural activities (36.63 %), fossil fuel (36.86 %), and steel production (34.35 %). Multiple factors played important roles in the selective transportation of sedimentary heavy metals, particularly sediment properties, and hydrodynamic sorting processes in the study area.