A comprehensive analysis on source-specific ecological risk of metal(loid)s in surface sediments of mangrove wetlands in Jiulong River Estuary, China

Metal(loid)s in mangrove sediments could pose noticeable ecological risks, but studies on source-specific ecological risks of metal(loid)s in sediments are limited. In this study, surface sediments collected from a typical mangrove wetland in the Jiulong River Estuary were used to perform a comprehensive analysis of the source-specific ecological risk assessment of metal(loid)s. Cd, Hg, Mn, and Cu were the metal(loid)s with large coefficient of variation (CV) values and were more likely to be affected by human activities. Principal component analysis (PCA) first identified four potential sources, namely, natural, coal combustion and industrial, aquacultural, and agricultural sources, of metal(loid)s in surface sediments. The absolute principal component scoremultiple linear regression (APCS-MLR) was then apportioned for its contributions to each metal(loid). The results showed that natural sources dominated the total metals, with a contribution of 62.7%, and coal combustion and industrial sources and aquaculture sources were the two major anthropogenic sources, with contributions of 19.26% and 17.50%, respectively. Three indices, the geoaccumulation index (I-geo), pollution index (PI), and potential ecological risk of individual factors (E-r(i)), clearly indicated that Hg and Cd showed much higher ecological risks than the other metals. Additionally, the integrated ecological risk could be more appropriately assessed by the Nemerow integrated risk index (NIRI), which showed no less than moderate ecological risks. More importantly, for the source-specific ecological risk assessment, the aquacultural source was identified to be a significant contributor to the ecological risk of Hg and Cd. In conclusion, the source-specific ecological risk rather than the sole source apportionment or ecological risk assessment could provide more information for the targeted environmental management of sediments contaminated by metal(loid)s.