Development and application of novel risk indices for assessing heavy metal pollution in aquatic sediments

This study presents the development of a new sediment individual risk index (SIRI) and sediment complex risk index (SCRI) to assess heavy metal pollution in Anzali Wetland sediments. SIRI incorporates total metal concentrations, bioavailability, and sediment quality guidelines. SCRI, derived through principal component analysis (PCA), integrates SIRI for a comprehensive risk assessment. The newly developed indices were systematically classified. Results showed varying risk levels with SIRI values of Zn, Cr, Cu, Pb, Ni, As, Cd, and Hg as 0.82, 1.32, 0.98, 0.71, 1.41, 1.37, 0.79, and 0.79, respectively. Pb, Cd, and Hg posed very low risk, Cu and Zn posed low risk, and Cr, Ni, and As posed moderate risk. SCRI yielded an index value of 1.02, indicating a moderate level of risk for the studied stations. Pearson correlation analysis validated SCRI with a highly significant and strong correlation coefficient (0.923) with metal bioavailability, serving as a risk indicator.