Dissolved Organic Matter as Carrier for Exogenous Organic Chemicals in Soils

Abstract

Dissolved organic matter (DOM) can act as sorbent for exogenous organic chemicals in soils, possibly leading to enhanced leaching of these compounds. The distribution of exogen ous organic chemicals in soils is considered here as an equilibrium of environmental chemicals in a three compartment system: dissolved, sorbed to dissolved macromolecules, and sorbed to the bulk soil matrix. In the present study the distribution of a new acidic herbicide in the three compartment system is investigated. Sorption isotherms are determined for the sorption of organic chemicals to bulk soil materials (Ap horizons) and to water-soluble soil organic matter. From these data an effective equilibrium sorption isotherm to bulk soil can be calculated which takes into account the sorption of organic chemicals to dissolved organic matter. A markable influence of DOM on sorption isotherms of the experimental herbicide is found only for high amounts of DOM (100 mg C L-1).