|Title||Integrated Water-Quality Assessment using Conventional, Passive-Sampling, and Metabolic Assay Techniques: Approaching System-Level Understanding of Risk|
|Date Issued||2011-05-25 (iso8601)|
|Note||Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR.|
|Abstract||Conventional monitoring to assess water quality of drinking water sources in streams and rivers is typically focused on identifying primary sources and conditions that are associated with mobilization of contaminants. This approach is often organized as a series of discrete samples collected in such a way as to capture the influence of specific land use activities or climatic events. Often streamflow data are included to facilitate calculation of loads, which allows the relative contribution from different sources and events to be compared. This approach is limited by the episodic nature of contaminant transport, so that integrating the health risk presented by observed concentrations is challenging with the limited data that are usually available. This limitation is especially pronounced because it does not account for synergistic effects among individual compounds. Other critical limitations include cost, considering the large number of compounds that may be relevant, and the analytical challenge of quantifying the very low concentrations that are typically present.
An alternative approach is provided by the use of passive sampling techniques that specifically address the detection level challenge by concentrating contaminants into sorbent material over a long period of deployment, generally on the order of 30 days. These samplers provide an integrated view of contaminant exposure over time, and can better detect trace amounts of chemicals because of the increased mass of material. Additional information on the synergistic effects of chemicals on biota is provided by analysis of metabolic assays, such as the yeast estrogen screen bioassay.
A combination of these three approaches in monitoring for drinking water source protection provides a more system-level perspective on transport and behavior of contaminants. This combined approach facilitates more complex understanding of contaminant occurrence and behavior than the simple monitoring of individual chemicals during targeted conditions, without sacrificing that more specific and detailed view. These three alternative modes of sampling are being used to evaluate risks to drinking-water quality in the McKenzie River. Early results demonstrate that the data complement each other and provide different insights. This approach is proposed as a useful foundation for monitoring a range of systems in Oregon that could provide a valuable opportunity for cost-effective collaboration by a number of drinking water providers.