Fraction spatial distributions and ecological risk assessment of heavy metals in the sediments of Baiyangdian Lake.

Baiyangdian Lake has been the ecological foundation of the Xiongan New Area, a newly developing economic zone in northern China since 2017, meaning that it is increasingly significant to recognize the contamination of the lake. In this work, the spatial distribution and ecological risk of heavy metals in the lake sediments were examined based on field investigation, multivariate statistical analyses and X-ray diffraction techniques (XRD). The results showed that the heavy metals in sediments pose moderate to high risks in most of the sample sites. The heavily contaminated sites presented more unstable chemical (exchangeable and reducible) fractions, and the ecological risk is highly sensitive to the exchangeable fraction in highly contaminative sites. The results of statistical analyses demonstrated that metal fractions were significantly correlated with physicochemical properties, and TP, TN and TOC exhibited a strong correlation with the exchangeable fraction of As, Cd, Pb and Zn. In contrast, Fe and Mn were weakly correlated with the fractions, which due to the high proportion of the nutrient elements in the sediment. Furthermore, the results from the XRD patterns demonstrated that the mineralogy phases of the various heavy metals contributed to the different chemical fractions. Those results demonstrated that further research on metal fraction distribution and influencing factors in the sediment should be implemented to ascertain the degree of toxicity to carry out effective strategies to remediate the lake sediment.