|Toxic Substances Hydrology Program|
Measuring Organic Wastewater Contaminants in Iowa's Streams
Very little is known about the presence of pharmaceuticals, hormones, and
other organic wastewater contaminants (OWCs) in Iowa's streams.
However, the effect these "emerging contaminants" might have human
and ecological heath is bringing on new concerns. Because of this, the
Iowa USGS, in cooperation with the IDNR Geological Survey Bureau, has begun to take a closer
look at contaminants associated with human, industrial, and agricultural
wastewaters. These OWCs can ultimately end up in our streams in a
variety of ways, such as:
For the initial nation stream reconnaissance of OWCs, 95 Target OWCs where targeted including prescription drugs, nonprescription drugs, steroids, reproductive hormones, personal care product, and other extensively used chemicals. These specific target OWCs were chosen because:
Since this study is the first of its kind in the U.S., five separate new analytical methods were developed. Each method was developed independently of each other, with different objectives, such as identifying hormones versus antibiotics. With these new methods, it is possible to detect the presence of a substance down to trace concentrations, generally less than one part-per-billion, and will be reported in micrograms per liter (mg/L).
The objective of the Iowa Stream Study is to determine the types and quantities of OWCs from urban areas. To accomplish this, 10 major urban centers were selected by the IDNR Geological Survey Bureau based on their city monitoring program. Samples were taken upstream and downstream of the selected urban centers to determine the potential contribution these cities have on OWC concentrations to streams. For some urban centers, such as Des Moines, two upstream sites were necessary because of the presence of multiple tributaries.
The sampling schedule consisted of three sampling rounds representing varying seasons and flow conditions: spring high flow, summer normal flow, and fall low flow. During the fall low flow sample only, four additional urban centers were studied: Milford, Storm Lake, Ankeny, and Newton.
To validate the credibility of the sampling and analytical techniques, quality assurance samples were collected during each sampling round. These typically involved running ultra pure water through the field and lab equipment, the exact same way the environmental samples were processed. (For more detailed information on the sampling procedures, click the methods tab on left).