03 March 2013
Posted in Center Information
Beneficial use of solid wastes generated from municipal cleaning activities such as street sweeping, ditch cleaning, stormwater pond maintenance, and catch basin sediment removal provide an alternative to landfill disposal, but the potential risk posed by the trace chemicals they contain must be assessed. Previous Hinkley Center research investigated trace chemical concentrations of these waste streams, include a class of chemical known as polycyclic aromatic hydrocarbons (PAHs). PAH compounds were detected on occasion at low concentrations, but the detection limit for several of these compounds was very close to the risk threshold, and some risk thresholds have been lowered over time. The current research was conducted to assess the total and leachable concentrations of PAHs in roadway and storm system residuals using laboratory methodologies with detection limits much lower than current regulatory thresholds
(high-performance liquid chromatography [HPLC] equipped with ultraviolet [UV] and fluorescence detectors).
Results of this study showed the presence of all the 16 US EPA priority PAHs in measurable quantities. The measured leachable PAH concentrations (mg/L) were lower than Florida’s Groundwater Cleanup Target Levels (GCTL), suggesting that risk from PAH leaching from these waste streams was minimal. For the most part, total concentrations (mg/kg) were less than Florida’s Soil Cleanup Target Levels (SCTL). Benzo(a)pyrene was elevated in some of the street sweepings samples, with a mean benzo(a)pyrene concentration in the ten samples analyzed above the residential SCTL, but lower than the industrial SCTL. When the location of the PAH compounds relative to sample particle size was assessed, they were generally found to occur in the lower fine and medium coarse fractions of the waste. Abraded asphalt particles from roadways were originally hypothesized to be the source of PAHs in the coarse fractions. Microscopic studies of the fractionated samples revealed the presence of asphalt particles in these fractions.