Sources of Pollutants in Urban Areas (Part 2) - Recent Sheetflow Monitoring

Abstract

Two research projects that examined source area sheetflows that were conducted in the 1990s are high-lighted in this chapter. These are a comprehensive project conducted in Birmingham, AL, as part of a project developing a control strategy for critical source areas, and a series of related projects conducted in Wisconsin as part of the DNR's efforts in calibrating the Source Loading and Management Model (SLAMM). A bibliography of recent source area monitoring activities by other researchers is also included in this chapter. These recent projects conducted in Alabama and Wisconsin are more comprehensive than the earlier monitoring efforts described in the previous chapter. These large projects included a wide range of land uses, source sources, and pollutants, in coordinated monitoring efforts. This information complements the data presented previously. 24.1 Birmingham, Alabama, Sheetflow Monitoring Pitt, et al. (1995) studied stormwater runoff samples from a variety of source areas under different rain conditions in Birmingham, AL. All of the samples were analyzed in filtered (0.45 µm filter) and non-filtered forms to enable Sources of pollutants in urban areas Pitt, Bannerman, Clark and Williamson: Sources of pollutants in urban areas, Part 2. In: Effective Modeling of Urban Water Systems, Monograph 13. James, Irvine, McBean & Pitt, Eds. ISBN 0-9736716-0-2 ©CHI2004 www.computationalhydraulics.com 486 partitioning of the toxicants into " particulate " (non-filterable) and " dissolved " (filterable) forms. Samples were taken from shallow flows originating from homogeneous source areas by using several manual grab sampling procedures. For deep flows, samples were collected directly into the sample bottles. For shallow flows, a peristaltic hand operated vacuum pump created a small vacuum in the sample bottle, which then gently drew the sample directly into the container through a Teflon tube. About one liter of sample was needed, split into two containers: one 500 mL glass bottle with Teflon lined lid was used for the organic and toxicity analyses and another 500 mL polyethylene bottle was used for the metals and other analyses. All samples were handled, preserved, and analyzed according to accepted protocols (EPA 1982 and 1983b). The organic pollutants were analyzed using two gas chromatographs, one with a mass selective detector (GC/MSD) and another with an electron capture detector (GC/ECD). The pesticides were analyzed according to EPA method 505, while the base neutral compounds were analyzed according to EPA method 625 (but only using 100 mL samples). The pesticides were analyzed on a Perkin Elmer Sigma 300 GC/ECD using a J&W DB-1 capillary column (30m by 0.32 mm ID with a 1 μm film thickness). The base neutrals were analyzed on a Hewlett Packard 5890 GC with a 5970 MSD using a Supelco DB-5 capillary column (30 m by 0.25 mm ID with a 0.2 μm film thickness). Sample extraction was critical for these organic analyses. Liquid-liquid separation funnel extractions were necessary to provide acceptably high recoveries of the organic toxicants. Burton and Pitt (2002) describe the method development for the sample handling and analyses in detail. Metallic toxicants were analyzed using a graphite furnace equipped atomic absorption spectrophotometer (GFAA). EPA methods 202.2 (Al), 213.2 (Cd), 218.2 (Cr), 220.2 (Cu), 239.2 (Pb), 249.2 (Ni), and 289.2 (Zn) were followed in these analyses. A Perkin Elmer 3030B atomic absorption spectrophotometer was used after nitric acid digestion of the samples. Previous research (Pitt and McLean 1986; EPA 1983a) indicated that low detection limits were necessary in order to measure the filtered sample concentrations of the metals, which would not be achieved by use of a flame atomic absorption spectrophotometer, or ICP unit most commonly available in commercial laboratories. Low detection limits would enable partitioning of the metals between the solid and liquid phases to be investigated, an important factor in assessing the fates of the metals in receiving waters and in treatment processes.