Isolation and Characterization of Different Organic Matter Fractions from a Same Soil Source and Their Phenanthrene Sorption

摘要

Four humic acids (HAs) including de-ashed HAs (D-HAs), twornhumins (HMs), nonhydrolyzable carbons, and demineralized fraction (DM)rnwere isolated separately from two soils and characterized detailedly; then theirrnsorption of phenanthrene (Phen) was examined. The sequence of removal ofrnHAs and minerals affected molecular composition of HMs. After de-ashing,rnthermal stability of HAs was improved; however, sorption (logK_∝) alsorndecreased due to removal of amorphous alkyl-C. Significant correlationsrnbetween CO_2 surface area of HAs with their sorption coefficients (n and K_∝)rnsuggested that pore filling could dominate Phen sorption. Alkyl-C couldrnfacilitate elevated thermal stability of OM and Phen sorption, supporting thatrnthermal stability of OM was correlated with Phen sorption. The OM fractionrncomposed of aromatic moieties (AMs) did not produce the highest logK_∝rnproviding strong evidence to dispute the dominant role of AMs in Phenrnsorption. No correlations between the K_∝ values of Phen by all tested sorbents and their bulk or surface polarity were observed,rnsuggesting that the role of bulk or surface polarity of OM fractions in regulating Phen sorption was dependent on soil sources.rnThis work shows the major influence of bulk and surface composition of OM and amorphous alkyl-C isolated from a soil samplernon hydrophobic organic compounds sorption.