Conformational Distribution of Dissolved Organic Matter Released from Compost by Repeated Water Extractions

The dissolved organic matter (DOM) released from compost by repeated water extractions was quantified and DOM conformational changes by high performance size-exclusion chromatography (HPSEC) were followed. Three commercial composts were extracted consecutively 4 times with equal water: compost ratios. The total organic carbon content of each DOM sample was analyzed using the chemical oxygen demand method, and the conformational size-distribution assessed by means of HPSEC. Results showed that compost continues to release considerable amounts of DOM with repeated water extractions, and that subsequent DOM extractions resulted in organic matter with increasing molecular dimensions and presumably larger hydrophobicity. This may have important consequences on soil processes and functions such as organic matter dynamics and transport of pollutants.