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Abstract The distribution of legacy heavy metals in industrial city soils is not well documented. Therefore, fundamental details such as the ‘background’ (i.e., non-road/non-dripline) concentration of trace metals in urban soils are uncertain. While there has been a strong focus on mapping lead contamination near roads and residences, these studies are generally not placed in the context of the urban background. In this study, ‘background’ distributions of urban relevant trace metals: arsenic, cadmium, copper, lead, and zinc were mapped based on soil samples collected throughout Pittsburgh. Distinct spatial patterns were revealed: contamination is elevated in the eastern portion of the study area, driven by dominant wind patterns and historical coking activities in low-lying areas (paleochannels), areas subject to atmospheric temperature inversions that focus air contamination. The mixing analysis revealed spatial structures in contributions of industrial activities to metal soil contamination. In particular, regions enriched in cadmium relative to zinc (i.e., Zn:Cd<317) were located near historical coking operations, and areas enriched in lead relative to zinc (Pb:Zn>1) were located in areas with historical secondary lead smelters. These results suggest a comprehensive accounting of the trace metals concentrations in background soils has important implications for the assessment of exposure risk in populations residing in historically industrial areas. Relatively sparse sampling of background conditions in urban systems can indicate patterns of legacy contamination and attribute this contamination to historical sources.
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Spring water discharge and metal enrichment in urban soils
Abstract Urban centers have inherited a unique mix of persistent contamination that impacts interactions among urban soil and groundwater systems. In particular, the potential for urban groundwater to transport contaminants from surface sources through the subsurface environment and ultimately to soils is not well understood. Studies have focused on specific ‘natural’ mechanisms driving distribution of metals in urban soils. However, very few studies have examined the accumulation of contamination in soils at groundwater discharge locations (springs) and the potential for groundwater to redistribute urban legacy contaminants far from the source. Soil transects straddling four groundwater springs in Pittsburgh, Pennsylvania were sampled to evaluate patterns resulting from contaminated groundwater discharge on urban soils. Metal concentrations were measured in pore water and compared with concentrations observed in total digestions and exchangeable extractions (acetic acid) of the soil. Across the springs Co, Cr, Ni, and V (metals often used in steel alloys) were elevated downslope, suggesting contaminated groundwater discharge enriches trace metals in these locations. These processes create unexpected biogeochemical patterns on the landscape and have the potential to create hotspots of soil metal contamination at predictable points across the urban landscape.
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- Award ID(s):
- 2012409
- PAR ID:
- 10550099
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Communications
- Volume:
- 6
- Issue:
- 10
- ISSN:
- 2515-7620
- Format(s):
- Medium: X Size: Article No. 105023
- Size(s):
- Article No. 105023
- Sponsoring Org:
- National Science Foundation
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