1a. Objectives (from AD-416):
Evaluate the environmental risks and benefits from agricultural applications of agricultural and industrial byproducts (e.g., FGD-gypsum, compost/manure) including uses to remediate disturbed soils and to sequester and phytoremediate metal from metal contaminated soils.
1b. Approach (from AD-416):
Develop and/or modify existing analytical methods to evaluate physical and chemical properties of byproducts and the potential environmental risks and benefits from their use in agriculture. Characterize mercury (Hg) emissions from FGD-gypsum amended soils. Evaluate plant species recommended for phytoextraction of Cd from U.S. contaminated soils requiring remediation to protect food safety.
3. Progress Report:
In 2013, ARS scientists collected, compiled, evaluated and analyzed data from experiments in which industrial, municipal and agricultural byproducts such as flue gas desulfurization-gypsum (FGDG), poultry litter ash, drinking water treatment residual, steel slag, biochar and compost were used in remediating nutrient and metal contaminated soils to prevent metal uptake by vegetable and agronomic crops. Data showed that these byproducts were very effective when used as plant nutrients and for remediation of phosphorus and metals contaminated soils. Metals concentrations within the tissue of plant grown on the byproducts amended soils were below levels considered to be phytotoxic and should cause no problem to human and animals that consume these crops. Using these materials is an inexpensive way to remediate several thousand acres of excess plant nutrients and metal and organic chemical contaminated soils in the U.S. It has been estimated that removal of 24 inches of contaminated top soil and replacing it with clean soil would cost $1.3 million per acre. The use of these amendments will reduce reclamation cost and reduce the need for additional landfill. Data collected from these studies will be used in developing risk assessment for some of these byproducts. Data from these studies will also provide information to industries, researchers and extension service on risk/benefit of utilizing these materials in agriculture.
1. Remediation of Dichlorodiphenyltrichloroethane (DDT) and dichloro diphenyl dichloro ethylene (DDE) contaminated orchard soils. Old orchards and other land may contain excessive residues of DDT and DDE from historic pesticide sprays which threaten the health of earthworm consuming birds and small mammals. Some historical orchard soils at Beltsville Agricultural Research Center (BARC) contain sufficient DDE to require removal or other remediation at great expense, and testing of using soil amendments to reduce earthworm DDT and DDE bioaccumulation was undertaken. Microcosm testing of compost and biochar amendment to reduce DDT and DDE accumulation by Lumbricus terrestris earthworms were conducted in a growth chamber to maintain cool temperatures for full earthworm activity. All of the composts and biochar significantly reduced DDE bioaccumulation by the earthworms during a 45-day exposure period after the plants were well established. No unusual metal accumulation by the earthworms was observed, indicating the value of the overall remediation treatment. A full field test of this approach was initiated using fresh and aged manure composts from BARC. Complementary tests of degradation products (DDX) bioavailability using thin film methods showed the strong ability of these physical chemical tests to predict earthworm bioaccumulation of DDT and DDE. Present results indicate that compost amendment can reduce earthworm bioaccumulation of xenobiotic compounds enough to achieve substantial cost savings in remediation of DDT and DDE contaminated soils.
2. Cadmium (Cd) in some historically biosolids amended soils comprises risk to food safety. Remediation of Cd risks before alternative land use could aid owners of such land. ARS researchers tested phytoextraction of Cd from soils from the Metropolitan Water Reclamation of Greater Chicago amended with Cd-rich biosolids before present biosolids regulations were established. Swiss chard grown on the soils accumulated Cd levels which highly exceeded international standards for Cd in leafy vegetable crops when soils were acidified. Phytoextraction with Cd-accumulating rice cultivars was unsuccessful under aerobic soil management. A corn inbred, B37, was also tested in these soils; this plant grew well and accumulated useful amounts of Cd. Because useful phytoextraction requires harvestable plant biomass rich in Cd, corn appears to offer more effective annual Cd removals than the other species tested. Noccaea caerulescens, a Cd accumulator, accumulates 96 percent more Cd than the corn, but has low yields and is short making biomass harvest difficult. Even corn grown as double-crop when shoot biomass is maximum, would offer higher annual Cd removal than other plants tested, although breeding to improve Noccaea may offer more effective Cd phytoextraction technology. Both Cd accumulating corn inbreds and Noccaea caerulescens require field evaluation before application to remove Cd from such contaminated soils to prevent future risk to humans through food-chain transfer of soil Cd.
3. Utilization of industrial and agricultural byproducts mixture as fertilizer for peanut crop production. Over 22 million tons of high soluble calcium flue gas desulfurization gypsum is produced in the U.S., of which only 2 percent is used in agriculture in 2012. One alternative to reduce excess phosphorus in soils on poultry farms is burning the poultry litter to generate electricity. The broiler litter ash that is produced is disposed of in landfills. Broiler litter ash is high in phosphorus, calcium, magnesium and potassium. The peanut is an important oil seed crop that is grown as a principle source of edible oil and vegetable protein that requires large amounts of soluble calcium and phosphorus. Results from a greenhouse study demonstrated that broiler litter ash and flue gas desulfurization gypsum were as effective for peanut production as super phosphate fertilizer and FGD-gypsum. Peanut kernel arsenic, cadmium, copper, manganese and zinc concentrations were within the recommended levels for human and animal consumption. Utilization of these two byproducts for peanut production will reduce the need for commercial phosphorus fertilizer and mined gypsum, while protecting the environment by reducing the amount of these byproducts entering the landfill and reduces excess phosphorus entering the surface and ground water.
4. Revegetation of barren asbestos emitting superfund site using compost and gypsum. Wind and water erosion of asbestos comprises continuing human risk at a 300 Acre abandoned asbestos mining site in Vermont. The Vermont Asbestos Group contaminated site is barren ground serpentinite rock which has remained barren for over 50 years. A greenhouse experiment was conducted in which application of manure compost plus gypsum and fertilizers achieved effective vegetative cover of the “soil”. The results from a three year field test of revegetation of these contaminated soils are being tested in cooperation with the US-EPA and the Vermont Department of Environmental Conservation in order to limit asbestos migration from the site. Two commercial composts from northern Vermont were mixed with gypsum, nitrogen, phosphorus, potassium fertilizer, limestone and gypsum, produced extensive vegetative cover of clover and grasses. Plots were sampled each year and both soils with depth and plants were analyzed. With gypsum amendment, all plants had adequate calcium (Ca). Roots penetrated up to 45 cm into the ground rock layer of amended plots, but plants did not survive on the fertilized control plots. Trace element concentrations of the crops were not high enough to comprise risk to wildlife, and adequate for plant growth. Gypsum supplied Ca which leached to about 15 cm depth in the profile of Mg-silicate rich soil materials allowed root penetration and improved plant survival. Estimates for remediation of the site indicate that over 90% could be saved by mine waste “revitalization” using compost plus gypsum compared to covering the site with imported topsoil.
5. Using hyperaccumulator plants for phytoremediation of metal contaminated soils. Using nickel (Ni) hyperaccumulator plants for phytoremediation of contaminated soils and for phytomining of Ni will benefit from fuller understanding of how these plants achieve such high accumulation of Ni (reach over 2% Ni in dry leaves). Previous knowledge of the chemical species of Ni in xylem exudate of Alyssum nickel hyperaccumulator species was contradictory. Earlier published work suggested that Ni being translocated to plant shoots in the xylem fluid was predominantly chelated by histidine, but this was based on short term studies and only solution grown plants. Five Ni hyperaccumulator Alyssum species and one non-hyperaccumulator were grown in nutrient solutions or in serpentine soils for six weeks before the stem was cut and steady-state xylem exudate collected for 1 hour. Exudate Ni was commonly 30 times more than amino and organic acids. This demonstrates that Ni in xylem exudate is mostly not chelated but moves as a free cation. Modeling chelation of Ni in these xylem exudates shows that about half of the Ni was chelated by some organic ligand. Based on these findings, effort to increase chelation of Ni in xylem exudate of Ni hyperaccumulator species will not be needed to increase annual Ni phytoextraction potential.
6. Zinc (Zn) toxicity to forest spreading near closed zinc smelter in Palmerton, Pennsylvania. Severe zinc phytotoxicity killed over 1000 acres of forest near a Zn smelter at Palmerton, PA, which closed in 1980. Inexpensive persistent methods to remediate this phytotoxicity are needed for this and similar acidic contaminated sites. Greenhouse investigations were undertaken to evaluate the effect of soil contamination on survival and growth of tree species and soybeans on mixtures of the contaminated and uncontaminated soils from this area. Based on growth of red oak, white pine, etc., it is clear that excessive soil Zn and Mn continues to cause phytotoxicity and kills germinating seedlings at the pH of the field soils. Soybean was included in the tests because the symptoms and metal concentrations associated with Zn, Mn and Cd phytotoxicity are established by previous research. It was clear that for most of the species, Mn was contributing significantly to the phytotoxicity observed, while Zn and possibly Cd contributed to the severe phytotoxicity observed. A test of raising soil pH to remediate the phytotoxicity was conducted with red oak with 6 levels of pH from background (4.5) to neutral. Raising pH alleviated phytotoxicity symptoms, and greatly improved growth and survival on the contaminated forest soil. Continuing acidic rainfall will likely cause increase in the barren area at Palmerton and similar smelter injured forest sites due to metal toxicity if no actions are taken to alleviate Zn phytotoxicity. The combination of compost plus limestone and other amendments has proven very effective in revitalization of dead soils at contaminated sites and provides an inexpensive alternative to imported topsoil for revegetation of such sites.
7. Using compost plus byproduct "Biomats" to remove contaminations from runoff. Leaching of metals such as lead (Pb), copper (Cu) and zinc (Zn) from urban buildings threatens stream quality. Lead (Pb) in runoff from a Pb sheathed building was 2000 times higher than surface water standards. Earlier laboratory column testing showed that mixtures of manure-yard debris compost plus steel slag was highly effective in removing Pb, Cu and Zn from runoff and full scale field tests were conducted both for the Pb exterior building and a parking lot using compost mixtures. The filters were designed based on the laboratory experiment results and physical circumstances at the building and parking lot where the tests were conducted. Water samples were collected before and after the Biomats were tested after 16 storms. Although highly effective in removing Pb, compost Biomats leaked phosphate above desired discharge levels, and additional tests with addition of water treatment residual (rich in iron (Fe) and Al hydroxides which can adsorb phosphate) are needed to test whether this will alleviate the excessive phosphorus (P) in treated runoff waters. For the parking lot, the capacity of the Biomats tested was not high enough to process all the runoff during storm events and a redesigned method will be proposed for study. Inexpensive water filters comprised of composts and byproducts, such as steel slag and drinking water treatment residue, could aid in prevention of runoff contamination from urban structures.
8. Risk assessment for beneficial use of flue gas desulfurization (FGD)-gypsum in agriculture. Millions of tons of fluidized bed desulfurization gypsum (FGDG) are produced annually by power generation companies which might provide benefit in agriculture (and cost savings to the generators) if environmental risk and benefit assessments were complete. ARS researchers and others have been conducting research to evaluate the beneficial use of FGD-gypsum in agriculture to improve infiltration, reduce erosion and reduce runoff of phosphate, arsenic and some other elements where poultry litter is used as amendment on pastures and hay fields. Cooperated with ARS scientists at Watkinsville, GA, and Auburn, AL, and with US-EPA, to measure elements in rainfall runoff samples from field tests. This was to show whether added FGDG could limit runoff of phosphate and other nutrients or contaminants where poultry litter was added on pastures. Concentrations of trace elements in FGDG, and in runoff, did not exceed water standards. Addition of FGDG with poultry litter was strongly effective in reducing runoff of phosphate, arsenate, copper and zinc added in the litter. FGDG application followed litter application by 30 days showing this was less effective in reducing phosphate or other element runoff. These findings indicate that FGDG should be applied with or shortly after poultry litter or other amendments if runoff control benefit is to be achieved. This research supports designation of FGDG as a beneficial use soil amendment to reduce runoff nutrients and trace elements from manure amended fields.
Codling, E.E. 2011. Environmental impact and remediation of residual lead and arsenic pesticides in soil. In: Stoytcheva, M., editor. Pesticide in the modern world-risks and benefits. www.intechopen.com: INTECH Open Access Publisher. p. 169-180.