The Palmerton Superfund was contaminated from 70 years of zinc smelting, resulting in the loss of vegetation cover and soil. Site restoration at the Lehigh Gap Nature Center (LGNC) included the planting of warm season prairie grasses. This has stabilized the soil, but the grasses are now considered a fire hazard. However, the existing site contamination has raised questions on the content and transport of the smoke from a managed prescribed burn of this vegetation to the surrounding environment and safety to the fire managers that are exposed to the smoke. The objectives were to reduce fire hazard of the prairie grass fuels, eliminate invasives and heavy metal accumulators species, and monitor the prescribed burn for contaminates and particulate emissions. Twenty five 1m2 plots were sampled for fuel loading prior to the burn and subsamples were prepared for heavy metal chemical analysis. Post burn samples were collected for burn efficiency. Particulate monitoring was done with three monitoring systems. A set of reference PM2.5 monitors were placed downwind to capture the concentrations with transport. A set of laser back scatter particle counters were placed outside the fire line to count and size the smoke particles. The filter packs inside the burn were used to determine the size , mass, and content using a 5 stage impactor filter system.
Results/Conclusions
Chemical analysis for heavy metal on grass fuels collected prior to the burn, showed high levels of Zn, Pb, Cd and Al. Zn content average across all samples was 5500 mg/kg (ppm), which is considered very high compared to previous analysis of vegetation on site (Husic, unpublished data), which was typically 200 -1650 mg/kg for grass species, and up to 2000 mg/kg for known heavy metal accumulators such as gray birch. Analysis showed two nodes of heavy metal content in the samples, a lower sample average at 1950 mg/kg and a higher average ~7000 mg/kg. Re-runs of several of samples by the CNAL lab gave very similar results.Heavy metal correlations of Zn:Al and Cd:Al were indicators of soil contamination, not tissue processing or lab error.Effectiveness of burn on reducing heavy metal accumulators and invasive species showed 81% reduction of grey birch and near 100% elimination of butterfly brush. Heavy metal concentrations in the smoke had Zn concentrations 6.15 – 24 ug/ m3; Pb concentrations .76 – 2.2 ug / m3. Cadmium was found to be above OSHA levels for fire fighter safety.