The Role of Dissolved Organic Matter Composition In Sorption to Minerals and Interactions with Pharmaceuticals.

The demand for potable water can be decreased through the use of reclaimed wastewater for irrigation of agricultural fields. However, this wastewater may contain a variety of pharmaceuticals and personal care products which are not completely removed during wastewater treatment. These contaminants are subsequently introduced to the soil along with a large amount of dissolved organic matter (DOM) which is also present in recycled water. Compounds with high mobility can leach into groundwater whereas less mobile compounds remain in the top layer of soil and may be taken up by biota. DOM influences the transport of contaminants in soils either directly, through the formation of DOM-contaminant complexes, or indirectly, through DOM-mineral interactions. Thus it is important to understand how DOM interacts with soil minerals to predict the fate of contaminants. It has been shown that certain components of organic matter are selectively sorbed to different mineral surfaces. This project focuses on the interactions between DOM samples and two types of clay minerals: kaolinite and montmorillonite. The use of three different DOM samples: Peat, Leonardite and forest soil-derived DOM, allows for the assessment of how varying composition, specifically aromaticity, influences preferential sorption. Analysis of the DOM composition before and after sorption by ¹H NMR reveals trends in preferential DOM sorption. The clay-DOM complexes as analyzed by ¹H high resolution-magic angle spinning NMR show which DOM components are available at the solid-liquid interface and are bound to the mineral surface.  The interaction of the pharmaceuticals 17α-ethynylestradiol, sulfamethoxazole and carbamazepine with the soil organic matter of various soils will also be discussed. This study will improve our understanding of the impact of using wastewater for irrigation and assist in making informed decisions regarding the further use of reclaimed water for agriculture.