Contents, Enrichment, Toxicity and Baselines of trace elements in the estuarine and coastal sediments of the Daliao River System, China

The Daliao River System (DRS) estuary in the Liaodong Bay has a highly industrial, urbanized, and agricultural catchment. The objective of this study was to investigate the multi-elemental geochemistry in the estuarine and coastal sediments, including enrichment, sources, toxicity, and geochemical baselines. Thirty-five sediment samples were collected from the estuarine and coastal area and analyzed for As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Sc, V, Y, Zn, P, Mn, Ti, Al, Fe, Ca, Mg, Na, and K. The average content (mg/kg) was 11.4 for As, 0.34 for Cd, 10.2 for Co, 60.8 for Cr, 20.0 for Cu, 0.05 for Hg, 22.6 for Ni, 26.6 for Pb, 71.8 for Zn, and 0.68 for Sb. The enrichment factor (EF) values of the trace elements, relative to the upper continental crust (UCC), ranged from 7.06 for As to 1.04 for Co, using Fe as a reference element. In general, As, Cd, and Sb were significantly or moderately enriched, while the other trace elements were not or were minimally enriched. The As and Ni in the sediments may pose potential toxicity to biota, while the Cd, Cr, Cu, Hg, Pb, and Zn might rarely or not pose toxicity. All elements except Ca, K, and Na were significantly and positively correlated with one another, with correlation coefficients of 0.523 to 0.994. Principal component analysis (PCA) revealed three groups of elements in association with secondary clay minerals, primary minerals, and carbonate minerals. Generally, the Cr, Cu, Hg, Ni, Pb, and Zn in the sediments originated from natural sources and their regional geochemical baselines (RGBs) were developed using Fe as a reference element. These RGBs may help identify the origins of these metals in the sediments of the Liaodong Bay and document their change over time.