Heavy metals pollution and the associated ecological risks along the Luanhe River basin in North China

Luanhe River is one of the important parts in Northern China hydrographic nets, which has been seriously impacted by industrialization. However, the heavy metal pollution caused by the production activities across the basin remains poorly understood, which may pose health risks to local residents. The study aims to address this gap by focusing on heavy metal pollution in sediments from 41 sampling sites along the Luanhe River basin evaluating the potential ecological risks. The results showed that, due to varying local industries, geography, and human activities, different sections exhibited distinct contamination patterns. The upper reach showed predominant pollution by Mn (up to 4305.59 mg kg^-1) and As (59.92 mg kg^-1), the middle reach by Mn (4305.59 mg kg^-1), Cu (692.88 mg kg^-1), As, and Hg (3.48 mg kg^-1), and the lower reach by Mn and Hg. Thereinto, the particular concern was the moderate to serious ecological risk posed by Hg across most of the river basin, as indicated by the potential ecological risk indices. For most of the identified heavy metals along the Luanhe River basin, the ecological risk assessed by the geo-accumulation index and potential ecological risk index indicated a moderate to serious pollution level. Overall, this work systematically depicted the heavy metal pollution map across the Luanhe River basin, revealed and discussed the relationship between industrialization and heavy metal pollution in this district. This study highlights that practical policy and technical measures should be taken to cope with the heavy metal pollution and associated ecological risks in this area.