Root uptake and its prediction model of PAHs from soils

Plant root uptake of phenanthrene and pyrene was evaluated using the data collected from a greenhouse study. Correlations of root uptake with soil contamination levels, physiochemical properties of organic contaminants, and plant compositions were investigated, and the results were used to evaluate a partition-limited model for plant uptake of organic chemicals from soils to plant. Results show that root concentrations of phenanthrene and pyrene dramatically increased with increasing contaminant concentrations in soils after 45-day treatment. However, root concentration factors (RCFs) decreased as the organic contaminant concentrations in soils increased. The initial concentration range examined in this study were 0～457mg/kg for phenanthrene and 0～489 mg/kg for pyrene, respectively. The measured root concentrations and RCFs of phenanthrene and pyrene were positively correlated with root lipid contents. The K ow of pyrene is much greater than that of phenanthrene resulting in that root concentrations and RCFs of pyrene were generally larger than those of phenanthrene across the plants tested in this study. It should be note that during the wide range of soil concentrations of phenanthrene (from less than 1 mg/kg to about 45 mg/kg) after 45-day treatment the partition-limited model always exhibited excellent predictions of root uptake from soils. The differences of predicted and observed concentrations of phenanthrene in roots of two representative plant species (i.e., ryegrass and flowering Chinese cabbage) were within 81%. Additionally, the quasi-equilibrium factor (α pt) in the partition-limit model significantly related with the root lipid content. Results of this study would provide useful information and a novel modeling approach for evaluating plant contamination based on the soil contamination levels, chemical properties and plant compositions, which would be of great importance to the food security, ecology and human health.