The influence of source on the sorption of dissolved organic carbon by soils

We examined the influence of dissolved organic carbon (DOC) source on the s orption of DOC by two clayey and two sandy soils using seven extracts From plant tissues and organic soil horizons. Sorption characteristics, such as null-point DOC concentration, partition coefficient and intercept, were det ermined over the initial solution concentration range of 0-50 mg DOC L-1. T he clayey soils had larger partition coefficients and higher null points th an the sandy soils. There was an average threefold variation in null-point DOC concentration and partition coefficient amongst the seven DOC extracts. Fractionation of the DOC samples into humic acid and hydrophobic and hydro philic acids, bases and neutrals revealed weak relationships between the so rption characteristics and DOC chemistry.