Robert S. Dungan

Emissions of ammonia, methane, carbon dioxide, and nitrous oxide from dairy cattle housing and manure management systems.

Concentrated animal feeding operations emit trace gases such as ammonia (NH₃), methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. The objective of this study was to determine the emission rates of NH₃, CH₄, CO₂, and N₂O from three source areas (open lots, wastewater pond, compost) on a commercial dairy located in southern Idaho. Gas concentrations and wind statistics were measured each month and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open lots were 0.13 kg NH₃, 0.49 kg CH₄, 28.1 kg CO₂, and 0.01 kg N₂O. Average emissions from the wastewater pond (g m(-2) d(-1)) were 2.0 g NH₃, 103 g CH₄, 637 g CO₂, and 0.49 g N₂O. Average emissions from the compost facility (g m(-2) d(-1)) were 1.6 g NH₃, 13.5 g CH₄, 516 g CO₂, and 0.90 g N₂O. The combined emissions of NH₃, CH₄, CO₂, and N₂O from the lots, wastewater pond and compost averaged 0.15, 1.4, 30.0, and 0.02 kg cow(-1) d(-1), respectively. The open lot areas generated the greatest emissions of NH₃, CO₂, and N₂O, contributing 78, 80, and 57%, respectively, to total farm emissions. Methane emissions were greatest from the lots in the spring (74% of total), after which the wastewater pond became the largest source of emissions (55% of total) for the remainder of the year. Data from this study can be used to develop trace gas emissions factors from open-lot dairies in southern Idaho and potentially other open-lot production systems in similar climatic regions.

Effect of propargyl bromide and 1,3-dichloropropene on microbial communities in an organically amended soil

Abstract In this study we investigated the response of microbial communities in unamended and manure-amended soil treated with the fumigants propargyl bromide (PBr) and 1,3-dichloropropene (1,3-D). The soil fumigants were applied at a rate of 10, 100, and 500 mg kg(-1). After treatment of the soils, the metabolic activity was assessed by monitoring the dehydrogenase activity (DHA). PBr and 1,3-D initially inhibited the DHA when applied at 500 mg kg(-1); however, after 8 weeks, recovery of the DHA only occurred in amended soil. Bacterial community level changes were monitored over a 12-week period after fumigation using denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S rDNA fragments. Band numbers were drastically reduced upon application of the fumigants, but reestablished more rapidly in the amended soil. To determine changes in the community diversity, the Shannon-Weaver index of diversity, H, was calculated for all treatments. In unamended and amended soil, the community diversity decreased with increasing fumigant concentration. In the PBr-treated soils, the diversity was higher in amended soil at all concentrations throughout the study, while in the 1,3-D treatments, the results were mixed. At 1, 4, 8, and 12 weeks after fumigation, major bands were excised from the gels and the DNA was cloned for sequence analysis. The bacterial communities in the fumigated amended soils were dominated by Streptomyces spp., other genera of actinomycetales, including Frankia, Cytophagales, Actinomadura, and Geodermatophilus, and a number of unidentified bacteria. Our results suggest that it may be feasible to reduce the impact of fumigant pesticides on soil microbial populations by stimulating microbial community structure, diversity and activity through the addition of organic amendments.

Accelerated degradation of methyl isothiocyanate in soil

Methyl isothiocyanate (MITC, CH3NCS) is the primary breakdown product of metam-sodium, and a potential replacement fumigant pesticide for methyl bromide. Methyl isothiocyanate is toxic and has a high potential for volatilization, therefore, minimizing its atmospheric emission is of the utmost importance. One method to reduce fumigant emissions is to enhance their degradation by incorporating organic amendments into the soil surface. In this study we determined the combined effect of temperature and chicken manure application rate on the degradation of MITC. The degradation of MITC was significantly accelerated by both increasing temperature and amendment rate. Differences between sterile and nonsterile degradation kinetics in unamended and organically amended soil indicate that MITC degradation is equally controlled by chemical and biological processes. The amelioration of soil with organic amendments should be further considered when designing fumigation practices that allow for reduced emissions.

The characterization of total and leachable metals in foundry molding sands.

Waste molding sands from the foundry industry have been successfully used as a component in manufactured soils, but concern over metal contamination must be addressed before many states will consider this beneficial use. Since there is little data available on this topic, the purpose of this study was to characterize total and leachable metals from waste molding sands. A total elemental analysis for Ag, Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, V, and Zn was conducted on 36 clay-bonded and seven chemically bonded molding sands. Total metal concentrations in the molding sands were similar to those found in agricultural soils. The leaching of metals (i.e. Ag, As, Ba, Be, Cd, Cr, Cu, Ni, Pb, Sb, and Zn) was assessed via the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and ASTM water leach test. Based on the TCLP data, none of the 43 molding sands would meet the Resource Conservation and Recovery Act (RCRA) characteristic for toxicity due to high Ag, As, Ba, Cd, Cr, and Pb. Compared to the TCLP results, the metal concentrations were generally lower in the SPLP and ASTM extracts, which is likely related to the buffering capacity of the extraction fluids.

Pyrolysis of Foundry Sand Resins: A Determination of Organic Products by Mass Spectrometry

Pyrolysis-gas chromatography-mass spectrometry (MS) was used to identify the major organic products produced by pyrolysis of three foundry sand resins: (i) Novolac and (ii) phenolic urethane (PU) (both phenol-formaldehyde based resins) and (iii) furan (furfuryl alcohol based resin). These resins are used in the metal casting industry as a “sand binder” for making cores (used to produce cavities in molds) and molds for nonferrous castings. During the casting process, the cores and molds are subjected to intense heat from the molten metal. As a result, the organic resins undergo thermal decomposition and produce a number of complex organic compounds. In this study, the organics were tentatively identified by MS after pyrolysis of the resins at 750°C. The major thermal decomposition products from the Novolac, PU, and furan resins were derivatives of phenol, benzene, and furan, respectively. Compounds identified that are of potential environmental concern were benzene, toluene, phenol, o- and p-xylene, o- and m-cresol, and polycyclic aromatic hydrocarbons. Pyrolysis of the Novolac resin resulted in the generation of the most compounds of environmental concern. Because there is interest in beneficially using foundry molding sands in manufactured soils and other agricultural products, it is necessary that organic thermal decomposition products be identified to ensure environmental protection.

Degradation of Fumigant Pesticides: 1,3-Dichloropropene, Methyl Isothiocyanate, Chloropicrin, and Methyl Bromide

Fumigant pesticides are frequently used in intensive agriculture to control nematodes, fungi, and weeds. Currently, four registered fumigants are available: 1,3-dichloropropene (1,3-D), methyl isothiocyanate (MITC), chloropicrin (CP), and methyl bromide (MeBr). The use of 1,3-D, MITC, and CP can be expected to increase after MeBr is completely phased out of production in the USA in 2005. In soil, the degradation of 1,3-D, MITC, CP, and MeBr occurs through both chemical and biological mechanisms. Repeated applications of the fumigants MITC and 1,3-D are known to enhance their biodegradation as a result of adapted microorganisms. Preliminary evidence suggests that the microorganisms responsible for enhanced degradation of MITC specifically target the isothiocyanate functional group. In the case of 1,3-D, a number of bacteria have been isolated that are capable of degrading 1,3-D and also using it as a sole C and energy source. Of the two isomers of 1,3-D, degradation of trans -1,3-D was found to be greater than that of cis -1,3-D in enhanced soil. Methyl bromide is mainly degraded chemically in soil by hydrolysis and methylation of nucleophilic sites on soil organic matter. Both degradation reactions occur via S 2 N nucleophilic substitution. Methanotrophic and ammonia-oxidizing bacteria can co-oxidize MeBr during the oxidation of methane and ammonia, respectively. The microbiological degradation of MeBr is apparently catalyzed by methane and ammonia monooxygenase. Chloropicrin can be dehalogenated by Pseudomonas spp., with the major metabolic pathway occurring through three successive reductive dehalogenations to nitromethane.

Hardwood biochar influences calcareous soil physicochemical and microbiological status

The effects of biochar application to calcareous soils are not well documented. In a laboratory incubation study, a hardwood-based, fast pyrolysis biochar was applied (0, 1, 2, and 10% by weight) to a calcareous soil. Changes in soil chemistry, water content, microbial respiration, and microbial community structure were monitored over a 12-mo period. Increasing the biochar application rate increased the water-holding capacity of the soil-biochar blend, a trait that could be beneficial under water-limited situations. Biochar application also caused an increase in plant-available Fe and Mn, soil C content, soil respiration rates, and bacterial populations and a decrease in soil NO-N concentration. Biochar rates of 2 and 10% altered the relative proportions of bacterial and fungal fatty acids and shifted the microbial community toward greater relative amounts of bacteria and fewer fungi. The ratio of fatty acid 19:0 cy to its precursor, 18:1ω7c, was higher in the 10% biochar rate soil than in all other soils, potentially indicating an environmental stress response. The 10% application rate of this particular biochar was extreme, causing the greatest change in microbial community structure, a physiological response to stress in Gram-negative bacteria, and a drastic reduction in soil NO-N (85-97% reduction compared with the control), all of which were sustained over time.

Greenhouse Gas and Ammonia Emissions from an Open-Freestall Dairy in Southern Idaho

Concentrated dairy operations emit trace gases such as ammonia (NH), methane (CH), and nitrous oxide (NO) to the atmosphere. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. Our objective was to determine the emission rates of NH, CH, and NO from the open-freestall and wastewater pond source areas on a commercial dairy in southern Idaho using a flush system with anaerobic digestion. Gas concentrations and wind statistics were measured and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open-freestall source area were 0.08 kg NH, 0.41 kg CH, and 0.02 kg NO. Average emissions from the wastewater ponds (g m d) were 6.8 NH, 22 CH, and 0.2 NO. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.20 kg NH and 0.75 kg CH. Combined NO emissions were not calculated due to limited available data. The wastewater ponds were the greatest source of total farm NH emissions (67%) in spring and summer. The emissions of CH were approximately equal from the two source areas in spring and summer. During the late fall and winter months, the open-freestall area constituted the greatest source area of NH and CH emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and other open-freestall production systems in similar climatic regions.

Characterization of physical and chemical properties of spent foundry sands pertinent to beneficial use in manufactured soils

As of 2007, of the 2,000 United States foundries, 93% produce ferrous or aluminum castings, generating 9.4 million tons of non-hazardous spent foundry sand (SFS) annually. Only 28% of the SFS is beneficially used. The U.S. EPA Resource Conservation Challenge identifies SFS as a priority material for beneficial use, with soil blending as a potential reuse option. The objectives of this work were to measure: (1) select chemical and physical properties important to soil quality and function and (2) total and soluble elemental content of 39 SFSs, in order to evaluate SFS suitability as a component in manufactured soils. Total elemental concentration of the SFS was lower than natural background soil levels for most elements analyzed, suggesting limited to no contamination of the virgin sand during metal casting. Pore water elemental concentrations were generally below detection. However, both total and soluble elemental content indicate a potential contribution of plant nutrients. Lettuce (Lactuca sativa) planted in SFS mixtures had a median germination rate of 96.9% relative to the control. Blending SFS at varying ratios with other materials will allow “tailoring” of a manufactured soil’s chemical and physical properties to meet specific growing needs. The SFS organic carbon, clay, and plant nutrient content are benefits of SFS that may make them good candidates as manufactured soil components.

Airborne endotoxin concentrations at a large open-lot dairy in southern Idaho.

Endotoxins are derived from gram-negative bacteria and are a potential respiratory health risk for animals and humans. To determine the potential for endotoxin transport from a large open-lot dairy, total airborne endotoxin concentrations were determined at an upwind location (background) and five downwind locations on three separate days. The downwind locations were situated at of the edge of the lot, 200 and 1390 m downwind from the lot, and downwind from a manure composting area and wastewater holding pond. When the wind was predominantly from the west, the average endotoxin concentration at the upwind location was 24 endotoxin units (EU) m(-3), whereas at the edge of the lot on the downwind side it was 259 EU m(-3). At 200 and 1390 m downwind from the edge of the lot, the average endotoxin concentrations were 168 and 49 EU m(-3), respectively. Average airborne endotoxin concentrations downwind from the composting site (36 EU m(-3)) and wastewater holding pond (89 EU m(-3)) and 1390 m from the edge of the lot were not significantly different from the upwind location. There were no significant correlations between ambient weather data collected and endotoxin concentrations over the experimental period. The downwind data show that the airborne endotoxin concentrations decreased exponentially with distance from the lot edge. Decreasing an individuals proximity to the dairy should lower their risk of airborne endotoxin exposure and associated health effects.