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ANALYSIS OF HEAVY METALS IN STORMWATER
Citation:
Tuccillo**, M E. ANALYSIS OF HEAVY METALS IN STORMWATER. Presented at ASCE Urban Water Resources Res Council/Engineering Foundation Conf, Snowmass, CO, 8/19-24/2001.
Description:
Sampling has been undertaken to determine the concentrations of heavy metals, both particle-associated and dissolved, in stormwater from several storm sewer outfalls in Monmouth County, NJ. This project is ongoing in concert with coordinated studies of pathogen and nutrient inputs from the same outfalls in a nested hierarchical design. The outfalls drain stormwater from different locally-designated land uses: high and low density residential areas, a section of highway, and a parking lot for a performing arts center. None of the outfalls drain an area with industrial or havey commercial usage and none have cross-connections. For this project, a rain event is defined as producing 0.125 in. of surface runoff for sample collection and having a72-hr antecedent dry period. The outfalls are instrumented with automatic samplers programmed to collect flow-weighted samples. Attached sensors measure pH, dissolved, oxygen, temperature and conductivity. Upon retrieval from the field, the samples are sequentially filtered to produce the following subsamples: an unfiltered sample, a 5 um filtrate, 0.45 ug filtrate, and a 10K Nominal Molecular Weight Limits (NMWL) pore size filtrate. The final filtration step (10K NMWL pore size) is accomplished with a stirred cell ultrafiltration unit. Subsamples are analyzed for metals by inductively coupled plasma spectroscopy and total organic carbon (TOC) by wet persulfate oxidation. Preliminary results have revealed Cu and Zn in the stormwater from all outfalls; concentrations varied significantly between outfalls. Cu concentrations ranged from 3.4-50.0 ug/L and Zn concentratons ranged from 17.4-135.0 ug/L. Both metals are predominantly in the dissolved phase. Cd was not detected in any sample. Trace amounts of Cr and Ni were detected in one sample, and trace amounts of Pb were detected in two samples; these values were extremely close to the method detection limits. TOC values ranged from around 4 to over 100 mg/L. Decreases in organic carbon concentrations of only 10-30% resulted from the sequential fltration as compared with the unfiltered samples. The results of this study provide needed data on the characteristics of stormwater that will impact receiving waters and BMPs that will drain the above-described land-use types.