The interactive effects of petroleum-hydrocarbon spillage and plant rhizosphere on concentrations and distribution of heavy metals in sediments in the Yellow River Delta, China

In order to understand how petroleum-hydrocarbon spillage and plant rhizosphere interact to affect concentrations and distribution of heavy metals, nine metals were analyzed from four different types of sediments (i.e. petroleum-hydrocarbon spilled rhizosphere, pristine rhizosphere, petroleum-hydrocarbon spilled unvegetated, and pristine unvegetated) in the Yellow River Delta, China. Our results showed that petroleum-hydrocarbon spillage together with rhizosphere effects were responsible for the significantly higher levels of metals in these four types of sediments. Compared to unvegetated sediments, rhizosphere sediments were well grouped into petroleum-hydrocarbon spilled and pristine sites on the basis of the concentrations of heavy metals by the correspondence analysis (CA). Furthermore, analysis of the transfer factors indicated that the capacity of rhizosphere sediments to stabilize heavy metals increased with increasing petroleum-hydrocarbon spillage, which might be due to the changes of sediment profiles by plant rhizosphere. Our results suggested that interactive effects of petroleum-hydrocarbon spillage and plant rhizosphere played an important role in determining concentrations and spatial distribution pattern of heavy metals.