Spatial Variability and Influencing Factors of Cr, Ni, Cu, Zn and Pb in Five Mangroves Reserves of South China

Abstract

In order to study the spatial variability and influencing factors of heavy metals contents in five mangroves in South China, surface sediments and plant canopy new leaves of mangroves were sampled to determine Cr, Ni, Cu, Zn, Pb contents. Moreover, the corresponding pollution load index of sediments and bioconcentration factors of leaves were evaluated. Meanwhile, the physical and chemical properties, organic carbon and nitrogen of surface sediments and new leaves were measured. It was found that the average content of heavy metals in the surface sediments of Futian Reserve was the highest with a pollution load index of 2.61, classified as strongly polluted. The particle size distribution of the five sites was mainly silt-sand, and the pH was slightly acidic. Multivariate analysis of variance indicated that both sampling locations and vegetation types had significant influences on heavy metal contents in surface sediments and leaves as well as bioconcentration factors of leaves. In sum, natural factors such as plant species and organic matter contents significantly influence the metal contents and translocation in mangrove forests. However, in strongly polluted areas anthropogenic factors compromise the natural effects and play the major role in metal distribution.