Location: Crop Systems & Global Change
2013 Annual Report
An additional topic was added to this cooperation during FY-2011, the risk assessment for beneficial use of FGD-Gypsum in agriculture. ARS and EPA have been conducting cooperative field tests of using FGD-gypsum and poultry litter on pastures, with simulated rainfall runoff to evaluate runoff risks. Large numbers of water, soil, amendment, and forage samples have been generated in these experiments which will be analyzed using required quality and detection limits in the analyses.
Revegetation of barren asbestos emitting superfund site using compost and gypsum was discussed. The Vermont Asbestos Group Superfund site is 300 acres of barren ground serpentinite rock which has remained barren for over 50 years due to severe infertility and poor soil properties. Methods to achieve persistent revegetation of such sites are being tested in cooperation with the US-EPA and the Vermont Department of Environmental Conservation. Based on previous success, using composts and biosolids in remediation of metal toxic soils, revegetation mixtures were designed and tested in greenhouse pots to alleviate both infertility and toxicity of the site soils with grasses and legumes. Mixtures of manure composts with flue gas desulfurization(FGD)-gypsum and nitrogen phosphorus potassium (NPK) gave immediate and strong revegetation in a greenhouse pot trial with potential cover crops. Two available commercial composts (180 t/ha) in northern Vermont were mixed with gypsum (25 t/ha), NPK and limestone for a field test of revegetation during August 2010; extensive vegetative cover was obtained and has remained persistent. Plots were sampled in July, 2011, and plants analyzed. With gypsum and compost amendment, all plants had adequate Ca. Roots penetrated about 45 cm into the ground rock layer of amended plots, but plants did not survive on the chemical-fertilizer control plots. Concentrations of trace element in the clover and grasses (analyzed separately) were not high enough to comprise risk to wildlife, and adequate for plant growth. By July 2012, vegetated plots with compost plus gypsum amendments continued to thrive with even higher biomass than 2011, while control plots remained barren. Vegetation held plots in place despite extreme rainfall events in VT in 2012 showing the ability of these treatments to hold the hazardous asbestos mine waste in place. Alternative treatment by leveling and cover with 24 inches of topsoil was estimated to cost $220 million, while use of surface applied compost mixtures should cost no more than $1.5 million and use locally available resources without removing topsoil from other locations. Soil samples from July 2012 were analyzed to evaluate leaching of surface applied Ca from compost and gypsum into the extremely Ca deficient soils. Analyses showed significant movement of Ca into and Mg from the surface 10 cm, and some Ca accumulation in the 10-20 cm depth. Rooting extended even deeper than apparent Ca changes suggesting that Ca leached down channels in the soil and roots followed the Ca.
During 2011, samples were collected from contaminated sites surrounding a smelter in East Helena, MT, where Pb remediation is sought to allow wider land use. Soils are contaminated with Pb, Zn, Cd, and As compared to background soils. Three bulk samples were collected for greenhouse pot testing of remediation methods to reduce soil Pb risk by reaction with composts or phosphate amendments. All materials and amendments (manure and biosolids composts available in East Helena) have been analyzed. Greenhouse pot tests of compost and limestone application to reduce soil Pb bioaccessibility and aid growth of appropriate revegetation species for East Helena were conducted. Phosphate and compost treatments decreased soil Pb bioaccessibility, but high phosphate treatment increased As uptake by crops and in a few cases induced As phytotoxicity. Evaluation of the experiment continues.
Soil samples at the New Idria Superfund Site in CA were collected by EPA cooperator and shipped to BARC. Samples were prepared for analysis. Mercury in mine and smelter disturbed soils and wastes have remained barren for decades allowing both erosion and volatilization of Hg from the mine wastes. Soils contain up to 10,000 times higher Hg than background U.S. soils, showing the extreme potential for Hg risks from these mine wastes. Some areas were rich in sulfides and have been extremely acidic and phytotoxic (pH <4.5), while others remain calcareous.
Participated in two Webinars held by US-EPA to communicate approaches for using soil amendments to achieve revitalization/remediation of metal contaminated soils at Superfund sites. This inexpensive alternative is increasingly favored at Superfund sites in several Regions.
In a related project, we are assisting EPA in conducting a risk assessment for beneficial use of FGD-Gypsum. Although previous gypsum products from exhaust desulfurization were contaminated by fly ash, in the last decade power plants have removed fly ash before desulfurization so that the new FGD-gypsum is very low in contaminants. Data were obtained from numerous FGD-gypsum and mined gypsum samples, and from soils and crops frm field tests in several states testing beneficial use. Samples of soils, amendments, forages, and runoff waters from simulated rainfall on the amended field plots at different periods post application are being analyzed as rapidly as possible considering the difficult processing needed to reach the needed detection limits. Separately, the methods to be used in the actual risk assessment (using collected data) are being developed and reviewed in cooperation with EPA and their contractors.
Project monitoring of the FGD-gypsum risk assessment is achieved thru regular conference calls of assessment participants, site visits to EPA in DC, and of EPA to BARC to observe facilities. A site visit was also made to the Auburn, AL ARS cooperator sites to present analyses and discuss findings.