INVENTORY OF HEAVY METALS: GREENLAWN CEMETERY ARBORETUM IN SALEM, MA

Salem, Massachusetts’ industrial history has resulted in legacy contamination, potentially impacting trees in Salem’s Greenlawn Cemetery Arboretum, including recently planted saplings. Soil cores (n=2) were taken near each sapling (n=20 trees), and the A horizon was sampled and analyzed for comparison to the Massachusetts Department of Environmental Protection’s (MassDEP) reportable concentrations thresholds (RCS-1). Of the samples analyzed, 60% were above the RCS-1 for arsenic and 18% above the RCS-1 for lead. All other HMs analyzed were below RCS-1 thresholds.

Two cores per sapling were taken: one proximal (~40cm from the tree), assumed to be “clean” fill from planting, and one distal (~2m from the tree), representative of in-situ undisturbed soil. T-tests were performed on the concentrations of the HMs from the proximal and distal samples, and lead was the only HM for which the concentrations were significantly different (proximal x̄=103.7±44.4ppm, distal 172.6±75.1ppm, p=0.001). This indicates the soil was likely backfilled instead of replaced with “clean” offsite fill.

The significant difference in Pb may be due to its higher partition coefficient, limiting its ability to be eluted out of the A horizon. Pb was above the RCS-1 in 35% of the distal samples but none of the proximal samples (n=20 for each group). As was above the RCS-1 in 70% of the distal samples and 50% of the proximal samples.

The locations of the saplings were also binned spatially (East, n=6; Center, n=3; South, n=11). ANOVA and Tukey’s pairwise tests showed that the only spatial difference was in zinc concentrations, which were significantly (p=0.048) higher in the eastern samples (x̄=106.2 ± 25.6 ppm) than in the southern samples (x̄=77.5 ± 30.6 ppm). Arsenic concentrations were above the RCS-1 in 67% of the eastern samples, 67% of the central samples, and 55% of the southern samples. Lead concentrations were above the RCS-1 in 8% of the eastern samples, 33% of the central samples, and 18% of the southern samples.

Further research into the provenance of the contamination is ongoing, with emphasis on lead arsenate and other historical pesticide applications. Ongoing sampling utilizing a hexagonal geogrid over the entirety of the arboretum will be used to increase the spatial extent and resolution of the dataset.