Source discrimination of potential toxic elements in quaternary sediment bores from Pearl River Delta, China.

Abstract

Delta is a transitional and sensitive zone of ecological geological environment, as well as an area with extremely serious potential toxic elements (PTEs) pollutions. The influence of geological background and sedimentary environment of watershed on spatial distribution of PTEs in sediments of alluvial delta is of great significance for prevention and control of soil PTEs pollutions in river delta. Research on it should still to be emphasized. This study took Pearl River Delta (PRD) as study area, sediment bores samples were collected from 10 points in different sub-watershed provenance and river delta. Discriminant analysis, principal component analysis and Pearson correlation analysis were utilized to investigate influences of watershed characteristic and sediment depositional environment on PTEs concentrations in sediments. The results show that sediment of bores from different sub-watershed provenances exhibit distinct geochemical characteristics which could reflect geological background in upper reaches of different sub-watersheds. Sediments carried by different rivers were constrained to their own low stand valleys and provided little opportunity for mixing between sources. PTEs of sediment in bores from delta area are principally controlled by provenance factors. Carbonate rocks, black rock series and polymetallic deposits are primary sources of PTEs in sediment of bores from delta area. Sedimentary environment constrains horizonal distribution patterns of PTEs of sediments in different bores. PTEs are enriched in silty and mucky clay strata of sediments formed by land-sea interaction. Drastic changes in hydrodynamic and chemical conditions are the main reasons for PTEs enrichment in sediments in terrestrial sedimentary and offshore sedimentary environment.