Influence of Organic Acids with Low Molecular Weight on Phosphorus Sorption by Typical Soils in Subtropical Regions
In order to explore the influence of organic acids with low molecular weight on phosphorus sorption by typical soils in subtropical regions,the effects of citric acid and oxalic acid on phosphorus sorption by upland and paddy soils were studied by using batch experiments.The influence of different concentrations of organic acids and sodium citrate and the addition order of organic acids on phosphorus sorption by soil were discussed.The results show that citric acid and oxalic acid significantly reduce the fitting degree of the intraparticle diffusion model of phosphorus sorption kinetics of soil and weaken the phosphorus diffusion process in soil particles.The Langmuir and Freundlich equations have a good fitting effect on isothermal data of phosphorus sorption by soil in the presence of organic acids(R2=0.863-0.996).Organic acids reduce the maximum theoretical amount of phosphorus sorption by soil.The amount of phosphorus sorption by soil is exponentially related to the concentration of organic acids,and organic acids of 0.1-5 mmol/L have the greatest influence on phosphorus adsorption by soil.When the concentration of organic acids is less than 1 mmol/L,the inhibition degree of citric acid on phosphorus adsorption by soil is greater than that of oxalic acid.When the concentration is greater than 5 mmol/L,the inhibition degree of oxalic acid is greater.At the same concentration,adding sodium citrate of 0.1-5 mmol/L has greater inhibition on phosphorus adsorption by soil than citric acid,and the early addition of organic acids further reduces phosphorus sorption by soil,indicating that the competitive sorption of anions is the main reason for the reduction of phosphorus sorption by soil caused by citric acid at a low concentration.The complexation of organic acids with metal ions such as iron and aluminum in soil is dominant at a concentration of citric acid of 5-50 mmol/L.
phosphorus sorptionsoilcitric acidoxalic acidorganic acids with low molecular weight
NETL
NSTL
万方数据
