Influence of environmental factors on changes in the speciation of Pb and Cr in sediments of Wuliangsuhai Lake, during the ice-covered period

Abstract

Ecological pollution caused by heavy metals released by sediments is a worldwide concern. However, the effect of changes in sediment speciation on their release of heavy metals has not been adequately reported. This study analysed changes in the sediment speciation of Pb and Cr before and after a release experiment by varying the temperature, pH, and salinity of the water column. The results show that the release of Pb and Cr from sediments increases with increasing water temperature, mainly due to the conversion of the residual fraction of Pb to the Fe-Mn oxide fraction and Cr converting more residual fraction to the organic matter and sulfide fraction. The release of sediment Pb and Cr decreased with increasing pH, with Pb converting more acid extractable fraction to the residual fraction and Cr converting more organic matter and sulfide fraction to the residual fraction. In contrast, the release of Pb and Cr increased and then decreased with increasing salinity, with the acid extractable and residual fractions of Pb interconverting, and the organic matter and sulfide fraction and the residual fraction of Cr showing higher interconversion. For Pb, the acid extractable fraction was more susceptible to conversion to the residual fraction by environmental influences, whereas for Cr, the organic matter and sulfide fraction was susceptible to conversion to the residual fraction. This study highlights the influence of environmental factors on the sediment speciation of heavy metals, which can help reveal the transport and transformation of heavy metals in cold and arid lake sediments.