Environmental Health - Toxic Substances
Investigations - Contaminants of Emerging Concern in the Environment
Stream-water-quality samples were collected on May 19-20, 2000, at 30 sites in the Stillwater River watershed, Ohio, during a runoff-generating storm. The timing and locations of sampling were selected to maximize the likelihood of detecting target compounds. The samples were analyzed for major ions, nutrients, selected pesticides and pesticide breakdown products (degradates), nitrogen isotopes, antimicrobials, and bacteria. Data acquired during this runoff study were compared with data from index stations in Ohio and from a national USGS study of antimicrobials in streams.
Several pesticides that never or infrequently were detected in samples from index stations were detected in a subset of the samples during the runoff study. These preliminary data indicate the dependence of stream-water quality on the timing of fertilizer and pesticide application in relation to runoff-generating rainfall.
Two antimicrobials were detected in runoff samples from 7 sites. Most of the detections of antimicrobials were in samples from small subwatersheds in the northern part of the study area. All antimicrobials detected in the main stem Stillwater and Great Miami Rivers were in high-streamflow samples collected during the spring.
Among several pathogenic organisms analyzed, three bacteria species were isolated from runoff samples: Escherichia coli, Enterococcus faecium, and Enterococcus faecalis. Preliminary results indicate patterns of resistance of isolated bacteria to antimicrobials were generally consistent with current understanding of bacterial resistance; however exceptions are undergoing further scrutiny.
Additional, more in-depth investigation is needed to understand the sources of antimicrobials in streams and the processes whereby antimicrobials are transported to receiving streams. This study was conducted in collaboration with the Centers for Disease Control.
Manuscript is in progress.