Heterogeneity in Composition and Reactivity of Dissolved Organic Matter and Metal Partitioning in Soil

Samenvatting (Engelstalig)

Soil contamination with heavy metals is concerning due to their persistence, toxicity, and bioaccumulation in food chains, which poses risks to environmental and human health. Dissolved organic matter (DOM) in soil solution plays a key role in heavy metal bioavailability and mobility by helping release metals from soil and transporting them, much like a "taxi." This thesis studied the variations in the composition and reactivity of DOM and how these differences affect the distribution of heavy metals in soil. Using aboratory experiments, surface complexation modelling, and other advanced techniques, I investigated (1) the physical-chemical processes regulating DOM release in soil under varying pH and calcium (Ca) concentration, 2) the composition and metal binding ability of DOM as affected by pH and Ca, 3) the effects of mixing subsamples differing in metal loading, organic matter content, and pH on soluble metal concentrations, and 4) the solid-solution distribution of heavy metals in soils contaminated by mining activities. The findings can benefit the development of strategies to mitigate DOM-induced environmental impacts and help to enhance the accuracy of risk assessments for heavy metal contaminated sites.