Sorption Comparison between Pharmaceuticals and Hydrophobic Organic Chemicals in Soils and Sediments

Abstract

The risks of organic contaminants are controlled by their sorption behavior. Hydrophobic organic contaminants (HOCs) have been studied for decades for their sorption properties in soils/sediments, while the relevant study on pharmaceuticals was started very recently. A systematic comparison of the sorption properties between HOCs and pharmaceuticals may facilitate our understanding on the sorption mechanisms of both HOCs and pharmaceuticals in soils/sediments. The studies on correlation between HOC sorption and soil/sediment properties have achieved some important conclusions, but a general method to predict sorption characteristics through soil/sediment properties is not available yet. The concept of relating the operational fractions, chemical compositions, and physical conformations of soil organic matter to HOC sorption might be referential to pharmaceutical studies. However, because of the comparable contribution of organic and inorganic soil/sediment fractions to pharmaceutical sorption and the various chemical properties of pharmaceuticals, the attempt to establish a common model to predict their environmental behavior, or more specifically, their sorption characteristics, may not be of great significance. A proper classification of pharmaceuticals according to their properties and functional groups may be very useful for pharmaceutical environmental fate studies. A very good start to investigate organic chemical sorption in soils/sediments may be to separate soils/sediments into individual fractions. This line of study revealed unique roles of organo-mineral complexes in controlling organic contaminant sorption. Carbon fractions are always the center of discussion on organic contaminant sorption. This chapter also summarized and compared the roles of carbon nanomaterials, activated carbon, and biochar to the sorption of both HOCs and pharmaceuticals. HOC and pharmaceutical sorption characteristics as affected by environmental conditions were discussed for dissolved organic matter, pH, cations, as well as other organic contaminants. The most distinct difference between HOCs and pharmaceuticals is that pharmaceuticals may present as different species depending on environmental conditions, while HOCs not. Traditional sorption studies incorporating pharmaceutical species analysis may be of 35 great importance. Several promising research directions were also discussed.