DISTRIBUTION OF HEAVY METALS IN SURFACE SEDIMENTS FROM THE PEARL RIVER OUTLETS, SOUTH CHINA: FIVE-YEAR MONITORING PROGRAM

We determined the concentrations of 10 metals (Fe, Mn, Zn, Cu, Cd, Pb, Cr, Ni, V, and Tl in surface sediments collected from eight outlets of the Pearl River from 2012 to 2016, and then used radar charts, Pearson correlations, principal component analysis (PCA), the geo-accumulation index (I-geo) and enrichment factor (EF) to analyze the concentrations. The average concentrations of the elements decreased in the order Fe > Mn > Zn > V > Cu > Cr > Pb > Ni > Cd > Tl. Among them, copper concentrations have increased continuously in the Jitimen outlet over the last 5 years, newly forming a Cu hot spot. The I-geo and EF indexes showed that Cd caused most contamination, with sediments classed as moderately to extremely polluted, and that the other metals caused either no or moderate pollution. According to the sources and distribution patterns, the examined metals fell into four groups when the comprehensive analyses were combined; Group 1 (Zn, Cd, Pb, and Mn); group 2 (Cr, Ni, and Cu); group 3 (Fe and V); and group 4 (Tl). Local governments should pay attention on preventing Cd risk on local ecosystem and controlling of Cu discharges to Jitimen outlet.