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Phytoremediation, i.e., the use of plants to clean up contaminated soil, may serve as a feasible alternative if a high-biomass crop can be found that accumulates metals to a high.degree. Two plant species, corn (Zea mays) and Indian mustard (Brassica juncea), were grown in soil from a Superfund site contaminated with Pb and Cd (PbTota, = 65,200 mg/kg and CdTotI = 52 mglkg) over two croppings. Soil treatments consisted of composted sewage sludge (CSS), ethylenediaminetetraacetic acid (EDTA), and sodium citrate at two concentrations. In most cases, the EDTA and citrate treatments were superior in terms of extracting soil Pb into root tissue, and translocation of Pb into aboveground biomass. The CSS treatment typically resulted in the lowest Pb removal efficiencies. The high pH (7.4) and high exchange capacity of the CSS may have immobilized soil Pb. Soil Cd was generally more mobile than soil Pb. The EDTA2 treatment was most effective in removing soil Pb into roots, and translocation to shoots. Lead remaining in the soil after two croppings was mainly associated with the carbonate, organic, and residual fractions, which represent the less bioavailable form of this metal. / Department of Natural Resources and Environmental Management

There is an ever-increasing need to address problems associated with the creation and disposal of wastes which result from human activities. Pb and Cd contamination is a common problem at many abandoned and uncontrolled commercial and industrial sites. Phytoremediation is one technology that can be employed to remove metals such as Pb from the soil. This study investigated the effectiveness of several plant and soil treatments on the uptake and retention of Pb and Cd by vegetation from contaminated soil at a Superfund site. Field plots were established and plant treatments included a mixture of grasses including Festuca, Poa. and Phleum; red clover (Trifolium Pratense); and sunflower (Helianthus annuus). Soil treatments included a common NPK fertilizer, ethylenediaminetetraacetic acid (EDTA), dilute sulfuric acid (H2SO4), and a mixture of EDTA and H2SO4 (EDTA+H2SO4). Trifolium tissue contained a greater quantity of Pb (182 mg Pb/kg tissue) than that of Poa (65 mg Pb/kg tissue). Cadmium concentration was similar in Poa and Trifolium tissue. ranging from 7.2 to 10.6 mg/kg tissue. Different soil treatments affected Pb levels found in plant tissue in order of effectiveness: H2SO4>EDTA>NPK>EDTA+H2SO4 The effects of soil treatments on Cd levels were similar to those for Pb with a difference of 0.1 mg Cd/kg tissue between EDTA and NPK treatments. Soil amendments differentially influenced Pb bioavailability and uptake, with H2SO4 exhibiting the greatest positive influence on Pb and Cd concentration in tissue. There was no correlation between the quantity of Pb and Cd up taken by vegetation at the site. The current study demonstrated the capability of common native plant species to grow on toxic and infertile soils, and the ability to uptake Pb and Cd to a limited degree. Regardless of tissue concentrations of Pb or Cd, Poa coverage at the site was generally dense. demonstrating the ability of Poa to become established on toxic soils and prevent soil erosion. / Department of Natural Resources and Environmental Management

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Bibliography: leaves 202-223.

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Extractive processes can permanently and significantly reduce the volume, toxicity and mobility of contaminated materials at affected sites. Ethylenediaminetetraacetic acid (EDTA), N-2 (acetamido)iminodiacetic acid (ADA), pyridine2,6-dicarboxylic acid (PDA), and hydrochloric acid (HC1) were evaluated in batch studies for their ability to remove lead (Pb) and cadmium (Cd) from a Superfund soil. The extraction of Pb as a function of time was limited and the order of Pb removal was EDTA > ADA > PDA > HC1. Repeated extractions did not treat the soil below the Pb regulatory limit (1,000 mg/kg); however, the Pb remaining occurs in an immobile form. All extractants treated the soil below the proposed Cd regulatory limit (40 mg/kg) within 1 h. Lead recovery from solution was accomplished by hydroxide precipitation in the presence of excess calcium, and recovery at pH 11 was 70%, 98%, and 97% from the EDTA, ADA, and PDA complexes, respectively. / Department of Natural Resources and Environmental Management

Evaluation of heavy metal accumulation in soils and plants is of environmental importance due to their health effects on humans and other biota. Phytoremediation is an emerging technology that can stabilize or remove heavy metals in soil utilizing metal tolerant plant species (metallophytes). The objectives of this study were to: (1) assess a Superfund site, and a lead-acid battery dump for concentrations of soil lead (Pb) and cadmium (Cd); (2) assess the various chemical fractions of Pb and Cd at both sites; (3) identify native herbaceous vegetation surviving in the contaminated soils; and (4) evaluate plant uptake of Pb and Cd. Soil Pb and Cd concentrations at the Superfund site averaged 55,480 and 8.5 mg/kg, respectively. Soil Pb at the Superfund site occurred primarily in the carbonate, sulfide/residual, and organic chemical fractions (41.6, 28.6, and 26.7, respectively). Soil Pb and Cd concentrations at the dump site averaged 29,400 and 3.9 mg/kg, respectively. Soil Pb occurred mostly in the organic and carbonate fractions as 48.5 and 42.5% respectively. Plant uptake of Pb at both sites ranged from non-detectable (Agrostemma githago, Plantago rugeli, Alliaria officinalis shoots), to 1800 mg/kg (Agrostemma githago root). Cd uptake was maximal in Taraxacum officinale at 15.4 mg/kg (Superfund site). In the majority of plants studied, root Pb and Cd content was higher than for shoots (>_65%). Tissue and soil fractions yielded r2 of 0.61 and 0.57 for the soluble and carbonate-Pb fractions, respectively. The plants with the greatest tissue concentrations of Pb and Cd were predominantly herbaceous species, some of which produce sufficient biomass to be practical for phytoremediation technologies. / Department of Natural Resources and Environmental Management

Permeable reactive barriers are considered among the most promising technologies for contaminated soil and groundwater remediation. Zero-valent iron (ZVI), hydroxyapatite (HA), and organic compost, with (OM) and without (OMx) dextrose/sulfate were assessed in column studies for their ability to attenuate chromium (Cr) or cadmium (Cd). PVC columns were packed with the reactive media and Cr or Cd solutions were pumped through the columns at concentrations of 5, 50 and 200 mg/l. These media were also assessed for their abilities to attenuate Cr and Cd from a contaminated soil. The order of Cr removal was: ZVI > OMx > OM > HA. The ZVI treatment maintained a removal rate of > 95% throughout the study. All treatments used for Cd removal had a removal rate of 98% across all treatments. The ZVI was the only treatment capable of retaining any of the mobile soil Cr and Cd from the contaminated soil. / Department of Natural Resources and Environmental Management

No description available.