Gao YZ Yang Y Ling WT et al.. Gradient Distribution of Root Exudates and Polycyclic Aromatic Hydrocarbons in Rhizosphere Soil. Soil Science Society of America Journal 2011 75(5): 1694-1703. (IF 1.866 农林科学，二区Top）
Abstract
The gradients of root exudates and of persistent organic pollutants including polycyclic aromatic hydrocarbons (PAHs) in rhizosphere soil in proximity to the root surface are still not well elucidated. In this work a greenhouse experiment was conducted to investigate the distribution gradients of root exudates and phenanthrene and pyrene as selected PAHs in rhizosphere soil close to (0–8 mm) the root surface of ryegrass (Lolium multiflorum Lam.) as the host plant. Rhizosphere soil from the root surface (0–8 mm) was divided into three layers: the rhizoplane and strongly and loosely adhering soil. Root exudates were characterized as soluble organic C organic acids and total soluble sugars. In PAH-spiked rhizosphere soils the concentration of root exudates decreased with distance from the roots. In a sterilized treatment the amounts of root exudates in the three rhizosphere layers were higher than when the soil was not sterilized indicating that microbial consumption contributed significantly to the loss of root exudates in the rhizosphere. The residual concentrations of phenanthrene and pyrene clearly increased in the order of rhizoplane to loosely adhering soil after 40 to 50 d which was significantly and negatively correlated with the amount of root exudates in the rhizosphere. In total 87 to 97% of phenanthrene and 69 to 79% of pyrene dissipated in all three layers of rhizosphere soil after 40 d and >99% of phenanthrene and 93% of pyrene dissipated after 50 d. The degradation ratio of PAHs decreased in rhizosphere soils with distance from the roots.
