Fate factors and emission flux estimates for emerging contaminants in surface waters

Pharmaceuticals, personal care products, hormones, and wastewater products are emerging environmental concerns for manifold reasons, including the potential of some compounds found in these products for endocrine disruption at a very low chronic exposure level. The environmental occurrences and sources of these contaminants in the water, soil, sediment and biota in European nations and the United States are well documented. This work reports a screening-level emission and fate assessment of thirty compounds, listed in the National Reconnaissance of the United States Geological Survey (USGS, 1999-2000) as the most frequently detected organic wastewater contaminants in U.S. streams and rivers. Estimations of the surface water fate factors were based on Level II and Level III multimedia fugacity models for a 1000 km(2) model environment, the size of a typical county in the eastern United States. The compounds are categorized into three groups based upon the sensitivity of their predicted surface water fate factors to uncertainties in their physicochemical property values and the landscape parameters. The environmental fate factors, mass distributions, and loss pathways of all of the compounds are strongly affected by their assumed modes of entry into the environment. It is observed that for thirteen of the thirty organic wastewater contaminants most commonly detected in surface waters, conventional treatment strategies may be ineffective for their removal from wastewater effluents. The surface water fate factors predicted by the fugacity models were used in conjunction with the surface water concentrations measured in the USGS reconnaissance to obtain emission flux estimates for the compounds into U.S. streams and rivers. These include estimated fluxes of 6.8 x 10(-5) to 0.30 kg/h km(2) for the biomarker coprostanol; 1.7 x 10(-5) to 6.5 x 10(-5) kg/h km(2) for the insect repellent N, N-diethyltoluamide; and 4.3 x 10(-6) to 3.1 x 10(-5) kg/h km(2) for the steroid estriol.