Black shale high geological background potential toxic elements(PTEs) in middle reaches of the Yangtze River tributary basin water environment, China: Distribution, pollution sources, and risk assessment

• Luyuan ChenHunan University of Science and Technology
• Bozhi RenHunan University of Science and Technology
• Xinping Deng
• Yin Wei
• Zhaoqi CaiHunan University of Science and Technology