Risk assessment and sequestered contamination evaluation for legacy heavy metal contaminants in Cleveland area brownfields

Brownfields are real estate properties for which the expansion, redevelopment, or reuse may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant. In old industrial cities such as Cleveland, brownfields can often be associated with legacy heavy metal contaminants. This dissertation presents the results of a series of brownfield surveys conducted in Greater Cleveland area. The heavy metal burdens (Cd, Cr, Cu, Ni, Pb and Zn) in soils are examined for fifty-three brownfields identified. Results demonstrate that most of these brownfield soils have heavy metal soil burdens well above background levels, seven of them contain lead concentrations in excess of Ohio's industrial remediation criteria. Risk assessment of the heavy metals is presented for these brownfields using state guidance values. Results demonstrate an unexpected degree of variability in guidance values for different states, and this often affects dramatically the cumulative hazard quotient posed by heavy metals for the same site using different states' criteria. The results of different soil extractions suggest that for lead the pH is perhaps the most important factor in its removal from soils, but chromium recovery is dependent on its speciation in the soil. Brownfield soils that have been contaminated for a long time often sequester contaminants deep within the soil particles. The sequestered contamination is difficult to remove. Heavy metal extractions are usually found to achieve improved results after soil pulverization, which exposes more of soil's internal bulk volume to extraction and provides shorter diffusion pathways for the sequestered contaminants to be released. The results of sequestering quantification using this pulverization technique are presented. Heavy metal sequestering has been found to be a common property in brownfield soils analyzed. The mass transport mechanisms of sequestered contamination are modeled, solid-state diffusion is one possible explanation for sequestering, but a micropore structure with sufficient internal acid neutralization capacity that resists pore acidification and solubization of sorbed metals on pore walls can also sequester heavy metals. Electrokinetically enhanced mass transport of sequestered heavy metals is modeled, and the results indicate a significantly accelerated mass transport after the use of direct electric field.