Distribution and sources of nutrients and heavy metals in surface sediments during freezing periods in Ulansuhai lake,Inner Mongolia

CUI Zhimou; SHI Xiaohong; ZHAO Shengnan; LU Junping; GUO Xin; WANG Yanjun; ZHANG Hao

doi:10.13984/j.cnki.cn37-1141.2026.01.012

Abstract：To investigate the nutrient and heavy metal pollution in the surface sediments of Ulansuhai lake during the freezing period,this study analyzed the spatial distribution characteristics,ecological risks,and potential sources of typical pollutants in the surface sediments during the ice-sealed period.The results indicated that the average contents of total nitrogen(TN),total phosphorus(TP),and or-ganic matter(OM)in surface sediments were 1.78 g/kg,0.51 g/kg,and 30.90 g/kg,respectively.TN exhibited moderate variability,while OM showed high variability,both presenting distinct spatial heterogeneity.According to the nutrient pollution index,TN and OM in surface sediments during the ice-sealed period were severely polluted,with all sampling sites classified as heavily polluted.Heavy metals,cadmium(Cd)and mercury(Hg),in surface sediments exceeded the standard significantly.The heavy metal geo-accumulation index(Igeo)further verified that Cd and Hg posed severe ecological risks.The potential ecological risk index(RI)of heavy metals ranged from 63.67 to 755.43,with a mean value of 359.36,indicating a strong potential ecological risk.Among them,Cd and Hg contribu-ted more than 80％to the total RI value.Multivariate statistical analysis suggested that nutrients were mainly influenced by winter plant wilting,decomposition,and farmland runoff.Cd and Hg were pre-dominantly derived from industrial sources.Agricultural production activities affected the distribution of As,Cu,Pb,and Zn,whereas chromium(Cr)mainly originated from natural sources.This study fills the research gap regarding lake sediments in the cold and arid regions of northwest China during the freezing period,further clarifies the responses of heavy metals and nutrients to various environmen-tal factors in ice-sealed lakes,and provides a scientific basis for water environment management and re-lated research in the Hetao basin.