Evaluation of Heavy Metal Contamination in Indus Deltaic Creeks Sediments, Sindh, Pakistan: Ecological Risk...

This study investigates the concentration, spatial distribution, and ecological risks of six heavy metals - cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) - in sediments from four deltaic creeks (Dabbo/Ambro, Hajamro, Khobar, and Waddi Khuddi) in the Indus Delta, Sindh, Pakistan. Cd, Cu, and Zn frequently exceeded average crustal abundances (0.2, 55, and 70 μg/g), with Cd surpassing TEL (0.7 μg/g) at Waddi Khuddi. Cu exceeded TEL (18.7 μg/g) at most sites, peaking at Waddi Khuddi, while Zn exceeded TEL (124 μg/g) at multiple sites. Spatial interpolation (IDW) indicated enrichment in fine-grained, organic-rich sediments of lower creeks and mangrove zones. Pollution indices classified Cd and Zn as moderately polluted (I_geo: 0.71 and 0.21). Enrichment factor (EF) values indicated minimal enrichment (EF < 5), with maxima for Cd (Khobar: 4.67) and Zn (Dabbo/Ambro: 3.58). Contamination factor (CF) values for Cd reached 2.5, while Pollution Load Index (PLI: 1.2⁓1.4) exceeded the baseline of 1.0, confirming cumulative pollution. Potential Ecological Risk Index (PERI) revealed considerable risk at Waddi Khuddi (86.2) and Hajamro (77.1), mainly from Cd (Eⁱ_r: 73.5). Nemerow's integrated pollution index (P_n) categorized sites as slightly polluted (1.33⁓1.94), whereas Toxic Risk Index (TRI_i) values (≤5) indicated no toxicity. Cu showed the highest mHQ (WK St-1: 2.69). Multivariate analysis indicated intermetallic correlations primarily governed by natural geochemical and sedimentary controls. In conclusion, heavy metal distribution is mainly controlled by natural processes, but moderate Cd, Cu, and Zn pollution pose localized ecological risks in depositional zones, warranting continued monitoring and source-tracking.