The Effects On Solubility Of Organic Pollutants PCP By Root Exudates

The pentachlorophenol (PCP) was once applied widely in the world as herbicide, antiseptic and pesticide. It was considered as one of the main persistent organic pollutants (POPs) in the environment because of its broad-spectrum toxicity and mutation for organism. Studying its phytoremediation in the environment can further understand the rule of migration and transformation for organic pollutants in the soil-plant-microorganism environment and the feasibility of phytoremediation and biological and ecology effect.At home and abroad, the studies on the phytoremediation of the organic pollutants had more,but less related to the solubility of organic pollutants by root exudates and its influence mechanism.Because of the more degradation of persistent organic pollutants were under the dissolving condition,the paper studied the effects on solubility of PCP by different root exudates,aimed to furthermore understand its mechanism,predominate its value in use and wide foreground, and indicated emphases study aspect.With pentachlorophenol as the targeted pollutants, the objectives of this paper were to find the best method for batch determination, to study the physical and chemical property of different root exudates,the effects of the apparent aqueous solubility and the n-octnol/water partition coefficient of PCP,the effects on solubility of the PCP by the root exudates received under differrent habitats, and pilot study solubilizing mechanism on PCP by root exudates.In this paper, the following results were obtained:(1) Using Lambda35 UV/VIS spectrophotometer to determine pentachlorophenol in root exudates, the determing wavelength was 215nm, the linear regressive equation was Y = 0.1269X+0.1193, the correlation coefficient r was 0.99968.The detection limit were 0.025mg/L and 0.024mg/L in the system of the root exudates of sunflower and alfalfa.According to results of the experiment,the method had good precision,the relative standard division(RSD) obtained was less than 3%(n=6),the recovery range are 61.01%-104.98% and 78.48% - 103.93% in the system of the root exudates of sunflower and alfalfa.The linear relationship was well.The method was convenient,fast and repeatable,good reproducibility, it's applicable for bath determination of pentachlorophenol in the course of study its phytoremediation.(2) The physical and chemical analysis and spectroscopy experiment indicated that the root exudates quantity of two kinds of plants was almost the same, but they makeup may had rather difference.The high molecular fraction content of root exudates of sunflower is high,but the hydrophilic fraction content was reverse,the apiece fraction content of root exudates of alfalfa was reverse compare with sunflower.The biodegradability of root exudates was related to molecule and polarity of root exudates.The higher the molecular weight of root exudates was,and the less the hydrophilic fraction content was,the more recalcitrantly root exucates degraded.Two kinds of root exucates all had strong absorption value,and with the wavelength increased , absorption value decreased,the absorption value of sunflower was higher than the root exudates of alfalfa.(3) Dissolution of PCP in the pure water and root exudates system might be denoted by simple first-order kinetics.Root exudates accelerated the solubilization of PCP, also evidently enhanced apparent aqueous solubility of PCP.There was a good positive correlation between root exudates concentration and the solubility of PCP, and the linear regressive equations had been established (rsunflower =0.8841**,ralfalfa =0.9550**).The solubility of PCP increased with root exudates concentration.The slope of the curve could measure the effectiveness of root exudates in solubilizing PCP.The solubilizing sequence among root exudates was sunflower > alfalfa.Besides,root exudates could decreased the n-octanol/water partition coefficient,the decrease sequence among root exudates was in contrast to that of solubilizing PCP.(4) Sunflower and alfalfa root exudates had the same change tendency of the solubility on PCP with the illumination time changed;when the illumination intension thansfered,the effects on solubility of PCP by sunflower and alfalfa root exudates were quite complex;with the temperature adding,the effects of alfalfa root exudates was gradually reduce,but the solubility on PCP by sunflower root exudates was earlier increase,and then decreased;with the increase concentration of KH2PO4,the solubility of PCP was earlier decrease, at the concentration of 0.005mmol/L,achieved the lowest value;under the different concentration of heavy metal Pb intimindating,the effects on solubility of PCP by sunflower and alfalfa root exucates had the conform change tendency.(5) The same as sunflower, when the medium was pure macromolecule fraction content of root exudates of alfalfa, unit TOC solubility of PCP was greater than original root exudates,and the effects on solubility by sunflower root exudates was more than alfalfa. The change tendency of the effects on solubility by hydrophilic fraction content was same as molecular weight, the effects by hydrophobic group was more than original root exudates,and the effects on solubility by hydrophobic group of sunflower root exudates was higher than alfalfa,therefore low molecule fraction content had high polarity,its solubility on PCP was low.