Natural Revegetation of an Aged Petroleum Landfarm Impacted With Polycyclic Aromatic Hydrocarbons (PAHs) and Heavy Metals (Cr, Pb, Zn, Ni, Cu): Ecological Restoration, Remediation, and Risk
Ecological restoration of hazardous waste sites is a potential remediation strategy that has not been well documented. Here, we assessed natural plant community development and soil remediation on an aged petroleum refinery land treatment unit (LTU) containing recalcitrant environmental pollutants. Preliminary assessment of phytotoxicity using bioassays (Lactuca sativa L. and Solidago canadensis L.) indicated that some tolerant phenotypes would grow on LTU soil. Fourteen permanent plots (37 m²) were then established onsite to assess actual plant succession and remediation: 11 for study of natural succession and 3 to act as a control by removal of vegetation. Two soil cores were removed annually from each plot, analyzed for edaphic factors and then sequentially extracted for metals and PAHs. Analysis of contaminants indicated a 50% reduction of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) in surface soil of vegetated and unvegetated plots after three years. There were no significant changes in total metal loadings. Metal content in plant root and shoot tissue was highly variable between species, but still low relative to soil levels, verifying the low bioavailability estimated from soil extracts. Plots were subsampled (1 m²) monthly for cover and abundance during the growing season, and for biomass at the end of the season. Monthly measurements of plant variables indicated that species richness increased from 28 to 57 species, cover increased from 33 to 79%, and biomass increased by a factor of four over three years. Plant growth was correlated to spatial and microclimatic factors, but contaminant loading showed no correlation. In fall of the following year, both LTU and a nearby unpolluted plant community of comparable size and successional stage were sampled as before: cover and abundance were measured in triplicate subplots (1 m²) within eleven plots. There were no significant differences in richness and percent cover between the sites. State-listed invasive species were less abundant onsite than offsite. Broader implications of these results suggest that other abandoned waste sites may be candidates for ecological restoration by natural succession. This study is unique in its field-scale demonstration of the potential of natural plant revegetation (passive ecological restoration) as a means of phytoremediation and phytostabilization of aged contaminated sites.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:phytoremediation heavy metals lead zinc copper chromium nickel polycyclic aromatic hydrocarbons pahs total petroleum ecological restoration invasive plant species bioavailability metal uptake
Date of Publication:01/01/2004