Effect of Different Soil Organic Matter Fractions on the Fate and Behavior of Polycyclic Aromatic Hydrocarbons in Soil Environment
|School||Fujian Normal University|
|Keywords||Polycyclic aromatic hydrocarbons Sorption Soil organic matter groups particle-size groups Bioavailability Distribution characteristics|
Soil organic component is an important factor in the effects of PAHs in the soil environment. The article to choose three types of organic component in soils that are not contaminated by PAHs group experiments, analysis of different components of organic matter on adsorption characteristics of polycyclic aromatic hydrocarbon phenanthrene. While selecting higher levels of PAHs for phytoremediation of contaminated soils in the field experiments and plant organic component of the soil before and after experimental group experimental and particle-size separates grouping experiments, Study on bioavailability of PAHs in the different organic matter composition and distribution characteristics of PAHs in particle size fractions. The main results are as follows:(1) Three fractions of organic matter (heavy fraction (HF), heavy fraction without the loosely combined humus (WLH), and tightly combined humus (TH)) were separated from three soil types named yellow-red soil, paddy soil and meadow soil. Batch experiments were conducted to study the sorption of phenanthrene by HF, WLH, TH and bulk soils (BS). Results showed that all sorption isotherms of phenanthrene by the different organic matter fractions and bulk soils fitted Freundlich equation and were nonlinear in some degree. The values of Freundlich exponent coefficient (N) followed the order of BS> HF> WLH> TH. The sorption capacity (KF) and its organic carbon normalized parameter (KFoc) for phenanthrene were in the order of TH> WLH> HF> BS, except that KF of TH was less than that of WLH in yellow-red soil. The KF values of different soils were in the order of meadow soil>paddy soil>yellow-red soil. However, the KFoc values were in the order of paddy soil>meadow soil>yellow-red soil. The KF values had a significantly positive correlation (p<0.05) with the organic C content of sorbents, and the KFoc values had a very significantly negative correlation (p<0.001) with the N values. The structural characteristics and degree of polymerization of organic matter were related to the sorption of phenanthrene in soils.(2) Using pot exterimnet, effect of PAHs pollution in the field in black soils and paddy soil and plant Ipomoea aquatica Forsk, bioavailability of PAHs of different organic matter fractions.After180d of growth, the plants were harvested and the soils were freeze-dried for analysis. The percentage of total PAHs removal was in the range of11.4%～18.4%and15.8%～19.1%for black soils and paddy soils. The PAHs total quantity reduced37.3%and10.8%respectively in the light fraction(LF) and heavy fraction(HF)of paddy soils, the PAHs total quantity reduced39.0%、38.4%and24.1%respectively in the loosely combined humus(LH), the stably combined humus(ST), and the tightly combined humus(TH) of the HF of paddy soils. The PAHs total quantity reduced51.2%%and14.4%respectively in the LF and HF of black soils,the PAHs total quantity reduced75.4%、75.0%and17.9%respectively in the LH, ST, and TH of the HF of black soils. HF is lowest percentage drop in organic matter fractins of two soils. The LF is easier digestion than the HF at soils PAHs of PAHs the reorganization in two kinds of soils, the LH of the restructuring in the PAHs is easier digestion than the ST and the TH.(3) Using pot exterimnet, effect of distribution characteristics of PAHs pollution in the black soils and paddy soils before and after planted Ipomoea aquatica Forsk. PAHs are very uneven in two soil samples in the particle-size separates. The content of PAHs in particle-size separates in the plant before and after an experiment with different degrees of change. Planted before and after an experiment, PAHs is highest content of soil in fine sand fractions in paddy soils, with the increase or decrease of particle-size separates;PAHs in particle-size separates in black soils is different of the paddy soils on distribution characteristics of soil specimens, concentrations of PAHs to the particle-size the minimum levels gradually decrease.Planted before and after an experiment, Two types of organic matter in soil particle-size separates on PAHs accumulation capacity sizes order for coarse sand>fine sand>coarse silt> fine silt> clay, Enrichment of organic matter on PAHs in particle-size separates abilities decline as the particle size decreases.