Spatial distribution characteristics and source analysis of heavy metals in river sediments in Western Hainan Island, China

Abstract

The spatial distribution and sources of heavy metals in river sediments can effectively reflect watershed geochemical processes. Hainan Island, the only tropical island province in China, is located in the country’s southern region, with eight major rivers in its western region chosen as the study area. A total of 67 surface sediment samples were collected to analyze six heavy metals (Cr, Cd, Pb, Zn, Cu, Ni). Contamination levels, ecological risks, and source contributions were assessed using the contamination factor (CF), geo-accumulation index (I_geo), potential ecological risk index (RI), and APCS-MLR model. The average metal concentrations followed the order: Zn (41.05 mg/kg) > Pb (30.93 mg/kg) > Cr (17.89 mg/kg) > Cu (8.23 mg/kg) > Ni (5.45 mg/kg) > Cd (0.08 mg/kg), with CV values ranging from 41.3% to 181.5%. The study area presented an overall low ecological risk. Pb (mean CF = 1.21) and Cd (mean CF = 1.08) exhibited moderate contamination. Cr, Zn, Cu, and Ni showed no contamination (CF < 1). The mean RI value was 39.70, indicating low overall ecological risk. APCS-MLR results identified three pollution sources: the dominant natural-agricultural-traffic composite source (64.0%), mainly controlling Cd, Pb, and Zn enrichment; the industrial source (13.3%), primarily affecting Cr, Ni, and Cu; and the mixed source (22.7%), representing multi-source superposition. This study clarifies the pollution characteristics and key sources of heavy metals in western Hainan Island river sediments, providing theoretical support for regional pollution management and watershed ecological restoration.