Total nitrogen and pH-controlled chemical speciation, bioavailability and ecological risk from Cd, Cr, Cu, Pb and Zn in the water level-fluctuating zone sediments of the Three Gorg... oleh Li-ping He, Dan Liu, Jun-jie Lin, Zhi-guo Yu, Xiao-xia Yang, Chuan Fu, Zheng-xue Liu, Qiao-hua Zhao