The Speciation Of Organic Contaminants In Typical Soil And Its Influencial Factors

The total concentrations reflect the overall accumulation in soils but tend to be overly conservative for assessing the ecological risks.Therefore,the key to understanding the risks of organic pollutants in soil and plant is the chemical speciation of organic pollutants in soil.It is also an important foundation to develop the new technologies to mitigation and control organic pollution in soil,and for ensuring the quality and safety of crops.In this study,a modified sequential ultrasonic extraction procedure is used to make it suitable for most types of organic pollutants and soils.The relationship between the fraction of bioavailability and the nature of the soil and organic contaminants was established.The mechanism,interaction with typical nanoparticles and the speciation typical organic pollutants in paddy soil was also investigated.The partition-limited model was modified to predict uptake of organic contaminates and tried to predict the amount of accumulation of organic pollutants in plants accurately.(1)The water-soluble and acid-soluble fractions extracted by a sequential ultrasonic extraction procedure(SEUP)were the bioavailable fractions.The plant uptake amounts corrected with weight were highly correlated with the bioavailable fractions(R2>0.75).The amounts of the bioavailable fractions were negatively correlated with the log Kow values(R2 ranging from 0.71 to 0.77)of the organic pollutants and the contents of soil organic matter(R2 ranging from 0.68 to 0.96).(2)The contaminants in engineer nanomaterials spiked and control soils were separated into bioavailable,bound and residual fractions using SUEP to investigate the mechanism,interaction with typical nanoparticles and the speciation typical organic pollutants in paddy soil.The bioavailable fraction in spiked soils showed no significant difference(p>0.05)from that in the control,while the bound fraction increased in equal proportion(p>0.05)to the reduction in the residual fraction.These results implied that ENMs can competitively adsorbed the bound of organic contaminants from soil and co-transferred into crops,followed by a portion of the residual fraction transferred to the bound fraction to maintain the balance of different fractions in soils.(3)It was found that partition-limited model predictions of organic contaminants in plants were observed values with the differences between estimated and measured concentrations ranged from-76.4%to-99.9%.The impact of the bioavailable fraction of organic contaminants in soil and transmission factor was excluded,the accuracy of the concentrations of organic contaminants in plants would be greatly enhanced,with the mean prediction error reduced from-97.8%to 14.9%for paddy soil,-97.3%to 14.2%for laterite soil and-96.8%to 13.4%for black soil.