The Role of Humic Substances in Biogeochemical Processes

Environmental pollution is an important subject as it is one of the major problems of modern society. The chemical pollutants produced imply severe threats for the quality of air, water supplies and soils. The comprehension of the transport, fixation, accumulation and allotment of pollutants in the environment is of paramount significance for the assessment of soil contamination and for the appliance of protecting remediation techniques. The fate of pollutants in soils is determined by adsorption processes, which strongly influence solute transport, microbial degradation, plant uptake through roots and therefore, the transfer of pollutants into other segments of the ecosystem and even into the food chain. Soil organic matter (SOM) is the major pool of active carbon on earth, and humic materials constitute the leading fraction of SOM. Humic substances occur widely, being present in almost all terrestrial and aquatic systems having a potential influence in soil fertility, mineral weathering, and water acidity. It is the purpose of this project to develop comprehensive models for humic substances in the form of microscopic sub-scenarios (oligomer- and polymer structures, e.g. polyacrylic acid and modifications thereof, structural units of lignin and cellulose) in order to investigate theoretically and experimentally interactions of specific chemical groups or collections of groups representing the activity of SOM with organic compounds, mostly certain classes of pesticides. Cation bridges and cation trapping will constitute one of the most important research questions of this project. The theoretical investigations will use molecular dynamics and Monte Carlo simulations based on density functional theory followed by force field investigations. Experimental sorption results describing the interaction of organic molecules and selected humic moiety model compounds will be compared in detail with the outcome of theoretical simulations. This project should lead to a better conceptualization of the interaction of organic compounds with humic moieties in soil systems resulting in a classification scheme of different interaction types. The envisaged results should not only contribute to the better principle understanding of soil processes, but also lead to comprehensive descriptions of specific problems and soil scenarios.

Environmental pollution is an important subject as it is one of the major problems of modern society. The chemical pollutants produced imply severe threats for the quality of air, water supplies and soils. The comprehension of the transport, fixation, accumulation and allotment of pollutants in the environment is of paramount significance for the assessment of soil contamination and for the appliance of protecting remediation techniques. The fate of pollutants in soils is determined by adsorption processes, which strongly influence solute transport, microbial degradation, plant uptake through roots and therefore, the transfer of pollutants into other segments of the ecosystem and even into the food chain. Soil organic matter (SOM) is the major pool of active carbon on earth, and humic materials constitute the leading fraction of SOM. Humic substances occur widely, being present in almost all terrestrial and aquatic systems having a potential influence in soil fertility, mineral weathering, and water acidity. It is the purpose of this project to develop comprehensive models for humic substances in the form of microscopic sub-scenarios (oligomer- and polymer structures, e.g. polyacrylic acid and modifications thereof, structural units of lignin and cellulose) in order to investigate theoretically and experimentally interactions of specific chemical groups or collections of groups representing the activity of SOM with organic compounds, mostly certain classes of pesticides. Cation bridges and cation trapping will constitute one of the most important research questions of this project. The theoretical investigations will use molecular dynamics and Monte Carlo simulations based on density functional theory followed by force field investigations. Experimental sorption results describing the interaction of organic molecules and selected humic moiety model compounds will be compared in detail with the outcome of theoretical simulations. This project should lead to a better conceptualization of the interaction of organic compounds with humic moieties in soil systems resulting in a classification scheme of different interaction types. The envisaged results should not only contribute to the better principle understanding of soil processes, but also lead to comprehensive descriptions of specific problems and soil scenarios.