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 2012, ARS scientists conducted laboratory, greenhouse and field experiments utilizing industrial, municipal and agricultural byproducts such as flue gas desulfurization-gypsum(FGD-gypsum), poultry litter ash, drinking water treatment residual, steel slag, biosolids, ground rubber, and bio char. These byproducts were effective when used as plant nutrients and for remediation of phosphorus, arsenic, cadmium, nickel, zinc, manganese, lead, asbestos and organic chemical contaminated soils. Application of these byproducts to metal contaminated barren soils reduces metal toxicity to seedling and increased vegetative cover which reduce the potential for phosphorus and metal runoff from these sites. Data collected from these studies are being used in developing risk assessment of these byproducts. Using these materials is an inexpensive ways to remediate several thousand acres of metal, asbestos and organic chemical contaminated soils in the U.S. It has been estimated that removal of 24 inches of contaminated top soil and replacing with clean soil would cost $1.3 million per acre. There is a growing interest in urban gardening. However, many urban vegetable gardens are planted on inner city lots or around homes with high lead levels from lead paint use. Inexpensive byproducts that urban home owners can have easy access, such as drinking water treatment residual, compost, steel slag and poultry litter ash were evaluated. Some of these byproducts were very effective in sequestering lead in lead contaminated soil and reduce the uptake by root and leafy vegetable crops. Data from this study will provide information to Maryland Agricultural Extension Service on home gardening on potential lead contaminated soils.
1. Utilizing new value added products from industrial byproducts (coal ash). As a result of farmer’s concerns of the pending legislation to regulate the buying and transporting of ammonium nitrate fertilizer, a research scientist at the Beltsville Agricultural Research Center (BARC) conducted a field study to evaluate the effectiveness of coal fly ash (FA) and FGD-gypsum encapsulated ammonium nitrate on corn, and rye yield. The coal byproduct encapsulated ammonium nitrate was as effective as the un-encapsulated ammonium nitrate for yield and nitrogen uptake by these crops. There was no significant difference in metal concentrations in these crops between the two nitrogen sources. Results from this study will provide farmers with an alternative option for ammonium nitrate fertilizer if buying and transporting of this fertilizer is prohibited.
2. Developed method to better determine phosphorus availability in poultry litter ash. Burning poultry litter to generate electricity is one alternative that is being implemented in order to comply with current regulation on poultry litter application on high phosphorus soils. The ash that is produced is high in phosphorus and is used as supplement phosphorus fertilizer for agronomic crops. Present extraction methods overestimates the plant’s available phosphorus. Scientists at BARC developed a method to better determine phosphorus availability based on ash solution ratio of Mehlich-1, Mehlich-3, Bray-1 and Olsen. Results from the newly develop method was validated by a BARC scientist using soybean as a test crop on a low phosphorus soil. The newly developed method will provide farmers better information on utilization of phosphorus in poultry litter ash.
3. Revegetation of barren asbestos emitting superfund site using compost and gypsum. 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 U.S.-Environmental Protection Agency 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 to alleviate both infertility and toxicity of the site soils with grasses and legumes. Mixtures of manure composts with 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 in northern Vermont were mixed with gypsum, NPK and limestone for a field test of revegetation during August 2010, and extensive vegetative cover was obtained and is persistent. Plots were sampled in July, 2011 and plants analyzed. With gypsum amendment, all plants had adequate calcium (Ca). Roots penetrated about 45 cm into the ground rock layer of amended plots, but plant did not survive on the fertilized 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 Vermont in 2012 showing the ability of these treatments to hold the hazardous asbestos mine waste in place.
4. 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. Where soil amendments were used, effective revegetation has persisted and become more diverse. However, where no remediation activities have taken place, extreme soil acidity has slowly become worse due to acidic rainfall. Investigations were undertaken to evaluate understory vegetation in remaining forest on the south side of Blue Mountain. Based on analysis of soils and plants, and measurement of seedlings present, it is clear that soil toxicity is preventing establishment of all plant species under existing remaining trees. Plant analysis shows that both zinc and manganese emitted by the smelter are contributing to toxicity and death of seedlings. First report of these findings was published, and other manuscripts have been prepared on greenhouse pot tests of both toxicity and ability of raising pH to remediate the soil toxicity. Continuing acidic rainfall will likely cause increase in the barren area due to metal toxicity if no actions are taken to alleviate Zn phytotoxicity of this site.
5. Phyto-ruminal bioremediation of soil explosives. Combining the ability of plants and rumen microbes to metabolize explosive compounds in contaminated soils was further evaluated during the FY. A plant uptake experiment was conducted with 14C-hexahydro-1, 3, 5-trinitro-1, 2, 5-triazine (RDX) added to Oregon soil. Samples are being analyzed. In another study, the ability of rumen microbes to tolerate and metabolize RDX was evaluated and one manuscript was published. With cessation of Congressional funding, this research project has ended.
6. Beneficial use of zinc (Zn) from ground rubber tires. Waste tires are a significant environmental problem; some tires are used to produce energy and others to produce ground rubber to mix with soil to reduce physical compaction in high traffic areas. Because tire rubber contains about 1.5% Zn and highly purified Zn (very low in cadmium and lead) is used in the vulcanization of rubber, we tested use of ground rubber as a Zn fertilizer and as a potting medium component. Additional field testing was undertaken by a cooperator in Iran where Zn deficient soils were amended with rates of ground rubber or Zn sulfate to increase crop yield and reduce grain cadmium (Cd); significant reduction in grain Cd was observed. In another test in Arizona, rates of Zn as Zn sulfate or ground rubber were applied to field plots of durum wheat cultivars to learn if high Zn fertilizer applications could reduce grain Cd levels; in this case where Zn was not deficient, little or no reduction in grain Cd was observed. This finding will provide the rubber industry additional uses for old rubber tires.
7. Chemical species of nickel (Ni) in xylem exudate of alyssum corsicum. Using the Ni hyperaccumulator Alyssum species to phytoextract Ni from mineralized or contaminated soils offers a commercial alternative to traditional mining, but using agricultural technologies. Improved understanding of how these plants achieve such remarkable accumulation and transport of Ni from soil to leaves is expected to aid in improving this technology or allow eventual transfer of all needed genes to higher yielding crop plants. 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 xylem exudate collected for 1 hour. Modern analytical methods allowed reliable detection of organic and amino acids under steady state hyperaccumulating conditions. Exudate Ni was commonly 3 millimolar, while histidine, citric acid, malic acid and nicotianamine, the amino and organic acids previously reported to possibly be the important chelator of Ni in these plants were typically no more than 0.10 millimolar, showing that Ni in xylem exudate is mostly not chelated but moves as a free cation. A manuscript on these findings was completed.
8. Effect of growth regulators on yield and nickel (Ni) hyperaccumulation by Alyssum species. An experiment was conducted to test whether application of growth regulator compounds would increase the biomass or Ni concentration in Alyssum Ni hyperaccumulator plants grown on serpentine soils. One paper reported a small but significant effect of applying one compound by increasing yield without affecting Ni concentration. In a second test (manuscript accepted), with longer growth periods and including more Alyssum species and rates of application, no significant increase was observed in Ni phytoextraction amount, either due to yield or Ni concentration in biomass. Additional trials are being undertaken to clarify the ability of commercially available growth regulator compounds on effectiveness of Ni phytomining.
9. Reducing bioavailability of soil dichloro diphenyl trichloroethane (DDT) to earthworms using compost and plants. Old orchards and other land may contain excessive residues of DDT and dichloro diphenyl dichloro ethylene (DDE) from historic pesticide sprays. Because earthworms bioaccumulate DDE from soils, and some birds and small mammals ingest large amounts of earthworms, the most limiting risk pathway for soil DDE is earthworm bioaccumulation to harm wildlife. Old orchard soils at Beltsville Agricultural Research Center 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 were undertaken. Soils rich in DDT and DDE were collected from the field for a growth chamber test using Lumbricus terrestris earthworms which require cool temperatures for full activity in soils. Several manure and biosolids composts and pine wood biochar were applied, and pots were planted with orchardgrass or not planted to see if plants could reduce DDE bioaccumulation as others have suggested. 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. Results were so successful that field tests to verify the pot experiments were funded. Complementary tests of DDX bioavailability tests showed the strong ability of these physical chemical tests to predict earthworm bioaccumulation of DDT and DDE and dieldrin. The newly developed test will provide information to industries and the U. S. Environmental Protection Agency on reclamation of these contaminated sites.
10. Phytoextraction of cadmium (Cd) from soils containing excessive biosolids applied Cd. Excessive Cd in some historically biosolids amended soils requires remediation before alternative land use may be permitted. We tested phytoextraction of Cd from soils from the Metropolitan Water Reclamation of Greater Chicago. Swiss chard grown on the soils accumulated Cd levels which highly exceeded international standards for Cd in leafy vegetable crops, especially if the soils were acidified. Phytoextraction with Cd-accumulating rice cultivars was unsuccessful under aerobic soil management needed for useful Cd phytoextraction. Three newly identified Chinese Cd hyperaccumulator herbaceous species were grown on the test soils, but either did not phytoextract useful levels of Cd, or suffered phytotoxicity from other metals in the soils than Cd and Zn for which these species were tolerant. A corn inbred, B37, shown to accumulate much more Cd than other corn inbreds was also tested in these soils and this plant grew well on the high metal soils. Because useful phytoextraction requires harvestable plant biomass rich in Cd, corn appears to offer more effective annual Cd removals than the other species tested. Thlaspi accumulated up to 900 mg Cd/kg shoots, but has low yields and is short making biomass harvest difficult. Even corn inbreds with 40 mg Cd/kg dry weight, grown as double-crop when shoot biomass is maximum, would offer higher annual Cd removal than other plants tested, although breeding to improve Thlaspi may offer more effective Cd phytoextraction technology. Growth of corn inbred B37 on acidified soils is being undertaken, including a treatment where normal subsoil is included below the high metal topsoil so that roots can obtain adequate Fe using roots below the metal rich depth. A report on the funded studies was submitted to the sponsor.
11. Using compost plus byproduct "Biomats" to remove contaminations from runoff. Previous laboratory tests showed that a mixture of manure compost plus steel mill slag and sand was a very effective filter to remove phosphorus, cadmium and zinc from runoff waters from an Animal Plant Health Inspection Service (APHIS) building with lead exterior walls and roof. Full scale field tests were conducted both for the Pb exterior building and a parking lot using Biomats. 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 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 planned to 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. A thesis on the studies in being prepared.
12. Risk assessment for glyphosate effects on manganese (Mn) and Fe uptake in genetically modified (GM) crops. After claims that glyphosate applications to Glyphosate-Resistant (GR) soybeans suffered Mn or Fe deficiency in the field, and suggestion that this treatment caused greater plant disease, a team prepared a critical review of availability scientific study of these possible effects. Obtained information clearly showed that claims of glyphosate induced Mn deficiency occurred only with the first cycle of GR soybeans when Mn- and Fe-deficiency susceptible genotypes were used to make GR cultivars. More recent GR-cultivars have not been observed to be more susceptible than standard cultivars to Mn or Fe. Tank mixes of Mn or Fe with glyphosate cause precipitation, so that neither the Mn or Fe fertilizers nor the glyphosate are properly absorbed by plants. Examination of the plant disease literature also showed no adverse effects of glyphosate use on GR cultivars ability to resist common plant disease in the U.S. Other claims cannot be addressed due to lack of published evidence of the claimed effects.
13. Risk assessment for beneficial use of flue gas desulfurization (FGD)-gypsum in agriculture. ARS researchers and others have been conducting research to evaluate the beneficial use of FGD-gypsum in agriculture. Ultimately, the adoption of FGD-gypsum use will depend on “Beneficial Use Designation” at the State level. ARS is cooperating with the U.S.-Environmental Protection Agency (EPA) in conducting a full risk evaluation of this use to provide information needed at the State level to make regulatory decisions about FGD-gypsum use as fertilizer and soil conditioner. The electrical generating industry which manufactures FGD-gypsum, while removing sulfur dioxide (SO2) from exhaust gases, now remove fly ash before removing SO2, allowing the production of FGD-gypsum with very low levels of trace elements compared to earlier products, confirmed by analysis. Field tests have been being conducted to assess the ability of FGD-gypsum to reduce the runoff of phosphate from soils including soils amended with poultry litter on the surface of hay fields. To date, research has shown that application of FGD-gypsum can significantly reduce runoff phosphorus (P) and arsenic (As). Other research has not found adverse effects of soils amended with FGD-gypsum compared to unamended soils. The Environmental Protection Agency and Agricultural Research Service cooperative field tests generated large numbers of water, soil and plant samples which are being analyzed using EPA required procedures which are highly time consuming. Several additional months are required to complete the analyses of samples from the completed field experiments. Simulated rainfall runoff water samples were analyzed for chromate and Hg shortly after generation to meet EPA requirements; no runoff water samples contained unallowable levels of Hg or chromate. These findings will provide U.S. EPA with additional information on the utilization of FGD-gypsum in agriculture.
Zia, M.H., Codling, E.E., Scheckel, K.G., Chaney, R.L. 2011. In-vitro and In-vivo approaches for the measurement of oral bioavailability of lead (Pb) in soil: A critical review. Environmental Pollution. 159:2320-2327.