Tracing organic pollutants in overland flow to their sources.

Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in our water supplies is often the first step in taking effective remedial action. Organic chemicals can be used to trace the sources of contaminants such as sediments, agrochemicals and nutrients because living organisms, like their wastes and decomposition products, are chemically unique. Using chemical characteristics to trace organic compounds to broad classes (i.e. animal, higher plant or bacteria) is a relatively simple task. For example, detection of a sterol unique to animals would identify animals as being present. Other studies (Leeming et al., 1994) have used faecal sterols to distinguish human and animal faeces in receiving waters. Faecal sterols are source specific due to the intake of the species, metabolic production of sterols and the biota present in the gut. Tracing of organic compounds to species specific sources is more difficult. In this study the organic chemical profiles (‘fingerprints’) from animal and plant species present in grazing systems were investigated. These chemical profiles were used to identify the source of materials in overland flow from an irrigated dairy farm in the Macalister Irrigation District.