Background, baseline, normalization, and contamination of heavy metals in the Liao River Watershed sediments of China

The quantitative assessment of heavy metal contamination in the sediments is a challenge due to the lacking of geochemical background or baseline levels and sediment heterogeneity. In this study, a procedure is suggested to elucidate the average background levels and geochemical baseline levels (GBLs) of Cr, Cu, Ni, Pb, and Zn in the Liao River Water sediments and to develop their geochemical baseline functions (GBFs). The average background levels of Cr, Cu, Ni, Pb, and Zn were 32.6, 11.1, 13.1, 16.3, and 37.8 mg/kg, respectively; while their GBLs (the upper limit of background level) were 60, 21, 27, 23, and 96 mg/kg. The linear correlation of heavy metals (Cr, Cu, Ni, Pb, and Zn) with particle-size proxy elements (normalizers) Sc, Fe, and Al was statistically significant at p < 0.001 level. However, Sc and Fe are the better normalizers for Cr, Cu, Ni, and Zn, while Al is the better normalizer for Pb. The river sediments adjacent to big cities and mining areas were contaminated by these heavy metals. The procedure in the study can be used to estimate GBLs and construct GBFs of heavy metals in other watershed sediments on the world in order to manage sediment quality.