Keywords: pentachlorophenol adsorption, PCP, root exudates, soil contamination, manganese oxides, iron oxides, organic matter, organic pollutants, environmental pollution, alfalfa, thermodynamics
Effect of root exudates on pentachlorophenol adsorption by soil and its main chemical components
The relationship between root exudates (REs) and the adsorption of organic pollutants has important impacts on phytoremediation of organic contaminated soil. The effect of REs collected from alfalfa (Medicago sativa Linn.) on pentachlorophenol (PCP) adsorption by soil and its main chemical components was investigated. The experimental results indicated that the data of PCP adsorption was fitted to Langmuir equation well. PCP was adsorbed mainly by organic matter and Fe oxides, but inhibited by Mn oxides in soil. The thermodynamic processes of PCP adsorption onto different soil samples were not changed in the presence of REs, but the adsorption amounts of PCP decreased. The effect of REs was functioned through affecting PCP adsorption by the main chemical components of soil, whose influencing degree was related to the adsorption capacities of the soil components for PCP. The decreases of PCP adsorption were induced mainly by the low–molecular–weight REs promoting the organic matter release from the soil samples, and the higher the content of organic matter was, the more its release amount was.