10. Physical and Chemical Factors to Consider when Studying Historical Contamination and Pollution in Estuaries

Understanding the history of contamination at a site may provide useful information to interpret past conditions. While organic compounds, such as pesticides, may behave quite differently in the environment compared to inorganic substances, such as metals, one common feature is that for different reasons, sediments often act as a common sink. In this sense sites with a history of deposition and little reworking are of interest to both the palaeo-environmental scientists and pollution scientists. Estuaries are often areas of significant deposition and are attractive to the historical study of anthropogenic inputs, however, sediments are also subject to a wide range of physicochemical conditions (from fresh to marine water) that fluctuate both in space and time. Changing water and sediment geochemistry influences metal binding capacity and flocculation of fine particles and for these reasons estuaries are challenging for the pollution scientist. However, methods of sediment characterization, sample preparation, and analysis have been developed over time to help understand the geochemistry that influences sources and sinks of contaminants, and their pathways through the environment. This chapter provides an extensive review of sediment contaminant characterization, including the sources, pathways and fate of contaminants in estuaries. It details analytical procedures and explores considerations when interpreting results. It has a focus on Australian estuaries but is relevant to estuaries around the world. The main aims of this review were to provide multidisciplinary researchers with a tool to further their inquiry and to encourage further studies of pollution/contamination in estuaries.