Water-quality assessment of the largely urban Blue River Basin, Metropolitan Kansas City, USA, 1998 to 2007

摘要

From 1998 through 2007, over 750 surface-water or bed-sediment samples in the Blue River Basin – a largely urban basin in metropolitan Kansas City - were analyzed for more than 100 anthropogenic compounds. Compounds analyzed included nutrients, fecalindicator bacteria, suspended sediment, pharmaceuticals and personal care products. Non-point source runoff, hydrologic alterations, and numerous waste-water discharge points resulted in the routine detection of complex mixtures of anthropogenic compounds in samples from basin stream sites. Temporal and spatial variations in concentrations and loads of nutrients, pharmaceuticals, and organic wastewater compounds were observed, primarily related to a site's proximity to point-source discharges and stream-flow dynamics. Total nitrogen concentrations were frequently greater than 10 milligrams per liter in surface-water samples and total phosphorous concentrations were routinely greater than 1 milligram per liter. Non-point source runoff accounted for the majority of bacteria in basin streams. Pharmaceutical and personal-care compound concentrations in water samples typically were less than 1 microgram per liter but mixture concentrations were frequently 30 to 50 times greater. More than 75 percent of samples analyzed had detections of the antimicrobial compound triclosan, the insect repellent DEET (n, n-diethyl-meta-toluamide), metabolites of detergent surfactants, caffeine, and the nicotine metabolite cotinine. More than one-half of stream samples had detections of pharmaceutical compounds; however, over-the-counter drugs accounted for more than 90 percent of the total mass of pharmaceuticals measured. In effluent-dominated reaches, increased caffeine and cholesterol plus coprostanol contributions to streams occurred during the winter when colder temperatures may have reduced wastewater removal rates; constituent contribution declines coincided with increased summer temperatures. For stream reaches that received only combined sewer overflows, seasonal load patterns more closely followed seasonal precipitation patterns because overflows were controlled by rainfall events. One exception was DEET, for which June to August accounted for the largest percentage of seasonal contributions at all sites. Biogeochemical processes in bottom sediments reduced some constituent concentrations by approximately two-thirds during a 6 to 8-month period. Bioassessments, indicated substantial declines in macroinvertebrate communities along an urbanization gradient. Declines correlated with increased upstream urban land-use and increased concentrations of anthropogenic compounds at stream sites.