2012 Annual Report
1a.Objectives (from AD-416):
The overall goal of the research project which is formulated as a real partnership between ARS and Western Kentucky University (WKU) is to conduct cost effective and problem solving research associated with animal waste management. The research will evaluate management practices and treatment strategies that protect water quality, reduce atmospheric emissions, and control pathogens at the animal production facilities, manure storage areas, and field application sites, particularly for the karst topography. This Project Plan is a unique situation in the sense that non-ARS scientists from WKU are included on an in-house project to conduct research under the NP 214. The objectives and related specific sub-objectives for the next 5 years are organized according to the Components (Nutrient, Emission, Pathogen, and Byproduct) of the NP 214, which mostly apply to this project as follows:.
1) develop improved best management practices, application technologies, and decision support systems for poultry and livestock manure used in crop production;.
2)develop methods to identify and quantify emissions, from poultry, dairy and swine rearing operations and manure applied lands;.
3)reduce ammonia, odors, microorganisms and particulate emissions from dairy, swine and poultry operations through the use of treatment systems (e.g. biofilters and scrubbers) and innovative management practices;.
4)perform runoff and leaching experiments on a variety of soils amended with dairy, swine, or poultry manures infected with Campylobacter jejuni (C. jejuni), Salmonella sp. or Mycobacterium avium subsp. paratuberculosis (MAP) and compare observed transport with that observed for common indicator organisms such as E. coli, enterococci, and Bacteriodes; and.
5)use molecular-based methodologies to quantify the occurrence of pathogens and evaluate new methods to inhibit their survival and transport in soil, water, and waste treatment systems.
1b.Approach (from AD-416):
This in-house project was conceived as a cooperative/partnership and comprehensive research program between USDA-ARS Animal Waste Management Research Unit (AWMRU) and Western Kentucky University (WKU). The project is designed to utilize the scientific expertise and facilities of both institutions to conduct problem-solving research related to animal waste management in Kentucky and the southeastern U.S. The research effort will be multi-disciplinary and multifaceted in support of decision making and systems development. Research focuses will be on all four components (Nutrient, Atmospheric Emission, Pathogens, and By-products) of the National Program 214. In lieu of repeatedly stating the equipment used for analysis, please note that the state-of-the-art laboratories and equipments exist at both AWMRU and WKU, which can be accessed by the scientists including land at the WKU research station. Main instruments include: ICP, GC-MS, 2 GCs, Latchet, 2 C/N Analyzers, IC, HPLC, Real-time PCR, etc.
Research related to this project plan under several objectives/sub-objectives investigates environmental problems related to the improper use of animal manure and agricultural waste including nutrients, pathogens, greenhouse gases (GHGs), odor-causing volatile organic compounds, dust and sediment associated with animal production facilities and manure application sites. Expansive research is going on to determine best management practices (BMPs) for crop production on land receiving agricultural waste with regard to nutrients and pathogens transport, runoff water, crop management, and soil types particularly in unique “karst topography”.
Research is being conducted to look at how the addition of biochar to soil affects the transport behavior of Escherichia coli (E. coli) through unsaturated soil. Research is also being conducted on how biochar addition to soils affects the transport behavior of important pathogens commonly found in animal manures – Salmonella and Listeria – through soils.
A study was initiated to evaluate the survival of naturally occurring pathogens (Campylobacter jejuni, Listeria monocytogenes and Salmonella enterica) and indicator organisms (E. coli, enterococci) in applied poultry litter or dairy manure. The first year of the study was completed. Concentrations of pathogens and indicators were monitored over the course of the study. Researchers also completed development of a high-throughput Deoxyribonucleic acid (DNA) extraction method for analysis of target organisms in broth and soil samples.
A back grounding cattle operation was used as a model site for characterization of soil nutrients, microbial pathogens, and veterinary pharmaceutical spatial distribution in a feedlot situation. Work in conjunction with Agricultural Research Service (ARS) scientists in Beltsville, MD, and in New Orleans, LA, continues.
A new study was initiated to evaluate swine manure composting. The study is being conducted in collaboration with a farmer in Davies County, KY, and with a University of Kentucky (UK) Extension specialist. Nutrient, bacteria and chemical analyses have been conducted on two composting runs. One additional study will be conducted to determine the effect of using corn refuse as a bulking agent on the compost process.
Experiments were finished determining sorption coefficients for polar organic compounds in organic matter poor soil and in the same soil amended with animal waste-derived biochar. Continuing research was performed on determining the effect of wastewater recirculation through an aerated semi-permeable membrane on wastewater malodors and greenhouse gases.
An experiment has begun in utilizing biochar from fast pyrolysis of rice-hull poultry litter in biofiltration systems for ammonia removal. The experimental objective was to compare the abiotic and biotic effects of biochar in removing ammonia from air stream. Lab-scale columns were packed with poultry litter, combination of poultry litter and biochar, and biochar alone for filtration of synthetic ammonia.
Laboratory smog chamber studies of amines. An ambient ion monitor (AIM) and aerodynamic particle sizer (APS) were used to study the atmospheric reactions and aerosol forming potential of amines. Previous studies have shown that amines are capable of producing aerosol particles but it is unclear whether this is due to acid-base chemistry yielding salt formation in the atmosphere or whether it is due to photochemical reactions typical with urban sources of air pollution. ARS scientists from Animal Waste Management Research Unit in Bowling Green, Kentucky, took the AIM and APS instrumentation to Riverside, California, to perform laboratory studies of atmospheric chemistry in the University of California Riverside’s (UCR) state-of-the-art environmental smog chamber. This project was collaborative with researchers from UCR, Utah State University, and Claremont McKenna College. The data show that both the acid-base and photochemical pathways for amines to form aerosol are important under normal atmospheric conditions. The data also indicate that there are some pathway differences that are influenced by relative humidity in the atmosphere. This project benefits the scientific community in helping to elucidate critical atmospheric chemistry questions.
Using phosphorus models to evaluate the accuracy of phosphorus indices. The U.S. Department of Agriculture’s Natural Resource Conservation Service (USDA-NRCS) recently revised its 590 Nutrient Management Conservation Standard. As part of this revision, USDA-NRCS is requiring that states test the accuracy of their phosphorus index, a tool which is used to assess the vulnerability of phosphorous loss from agricultural fields, using either measured phosphorus loss data or data generated from a process-based phosphorus loss model. With this in mind, an ARS scientist at the Animal Waste Management Research Unit in Bowling Green, KY, used phosphorus loss data generated from a phosphorus transport model to evaluate the KY phosphorus index. Moreover, the general formulation of the KY phosphorus index was evaluated against current research on the processes controlling phosphorus transport in the environment. Results suggest that in some areas the KY phosphorus index does a good job in assigning phosphorus loss risk, however, this analysis also showed some important deficiencies in the index, primarily the neglect of important factors known to affect phosphorus loss (e.g., soil erosion and phosphorus application rates) and how the different factors in the index are weighted. This research has resulted in the ARS scientist giving invited talks at universities, watershed advocacy group meetings, and local scientific meetings in KY. The ARS scientist has also been asked by KY USDA-NRCS and the University of KY to lead an effort to revise the KY phosphorus index.
Use of biochar to increase Escherichia coli retention in soils. The incorporation of biochar into soils has been proposed as a means to sequester carbon from the atmosphere. Recent studies have shown added environmental benefits to biochar amendments to soil such as increased soil retention of nutrients, heavy metals, and pesticides, yet no studies have looked at the role biochar plays on microbial transport in soils. ARS scientists at the Animal Waste Management Research Unit in Bowling Green, KY, have conducted studies to evaluate whether biochar amendments can reduce the transport of E. coli through soils. Results from this research show that the addition of biochar to soil can indeed affect the retention and transport of E. coli – a commonly used indicator of fecal contamination in groundwater. Results indicate that the amount of E. coli retention in biochar-amended soils depends on biochar application rate, temperature that the biochar was produced, and surface characteristics of the bacteria. If biochar is to be widely used as a soil amendment, it is important that its impact on microbial transport through the soil be understood, especially for fields where animal manure is applied. This research is the first to investigate this important environmental topic and results from this research provide important information on the factors controlling bacterial transport through biochar-amended soils. Results suggest that biochar has the potential of being used as a management practice for protecting shallow groundwater supplies from contamination by pathogenic microorganisms.
Impact of growth conditions on transport behavior of Escherichia coli. E. coli is the most commonly identified fecal indicator bacteria originating from agricultural and urban runoff, and is used as an indicator of water quality. Hence, understanding the fate and transport of E. coli originating from agricultural waste is essential for assessing water quality and protecting drinking, recreational, and agricultural water sources from contamination. Most published research on E. coli fate and transport has utilized highly idealized conditions; in particular, nutrient-rich growth media is often used for the organisms to grow in. Such nutrient-rich conditions, however, are not representative of animal manures. Therefore, to understand the fate and transport of E. coli originating from agricultural waste it is essential that the organisms are grown in more representative media. To address this gap in the scientific literature, ARS scientists at the Animal Waste Management Research Unit in Bowling Green, KY, in collaboration with the University of California at Riverside conducted a study to compare the differences in the fate and transport of E. coli cells grown in dairy manure extract solution and a more traditional laboratory growth media. Following growth in one of the two growth media, the surface properties of eleven E. coli isolates were extensively characterized and the transport of each isolate through 10-cm columns packed with sand was measured. In general, cells grown in manure extract had different cell-surface properties and transport behavior than cells grown in standard nutrient-rich media. This study shows that when studying E. coli transport, consideration must be given to utilizing growth conditions that better mimic the conditions that bacteria are exposed to in the environment. Utilizing more appropriate growth solutions will likely lead to a better understanding of the behavior of manure-derived bacteria in aquatic and terrestrial environments.
Atmospheric emissions of greenhouse gases (GHG) from different nitrogen (N)fertilizers. Increasing demand for food and agricultural products directly relate to increased greenhouse gas (GHG) emissions, particularly the three primary gases associated with agriculture [Nitrous Oxide (N2O), Methane (CH4), and Carbon Dioxide (CO2)]. Commercial Nitrogen fertilizers and organic N sources such as animal manure stimulate N losses mainly through biochemical processes. ARS scientists at USDA-ARS in Bowling Green, Kentucky, have investigated the effects of N2O, CH4, and CO2 emissions from application of several inorganic N fertilizers, commercially available enhanced-efficiency N fertilizer, and poultry litter under no-till corn production. No significant differences were observed in N2O emissions among the enhanced-efficiency N fertilizers and other N fertilizer sources. The CH4 and CO2 emissions were impacted by the environmental factors more than the N source. Results demonstrated that N fertilizer source and climate conditions need consideration when selecting N fertilizer that reduces greenhouse gas emissions.
Amending poultry litter to reduce ammonia producing bacteria. As fertilizer costs increase, poultry litter has become an increasingly valuable commodity. Reducing ammonia volatilization from poultry litter is therefore important to not only reduce ventilation costs and improve bird performance but also to retain the fertilizer value of the litter. Ammonia is produced when bacteria in the poultry litter breakdown poultry urine (i.e., urea and uric acid) which makes up 80% of the nitrogen in poultry litter. ARS scientists in the USDA-ARS Animal Waste Management Research Unit Lab at Bowling Green, KY, and in the Richard B. Russell Research Center (RBRRC) in Athens, GA, found that poultry litter amendments reduce ammonia emissions by both chemical and microbiological means. These ARS researchers showed that acidifier amendments and a novel litter adsorber amendment, chitosan, reduced ammonia producing bacteria to the greatest extent. Chitosan is a derivative of chitin one of the most abundant sources of carbon on earth. This low cost, readily available, poly-cationic adsorbent used alone or in conjunction with an acidifier may delay onset of ammonia production thereby reducing organic nitrogen loss from litters. This research provides valuable new information for producers, integrators and researchers interested in reducing ammonia volatilization from poultry litter.
Inorganic fertilizers after broiler litter amendment reduce surplus nutrients in orchardgrass soils. Broiler litter is a good source of plant nutrients and as a soil amendment. It contains substantial amounts of nitrogen (N), phosphorus (P), potassium (K), and other nutrients, such as calcium, magnesium, sulfur, manganese, and zinc (Zn). Poultry producers usually dispose of broiler litter at high rates to forage crops, which allow excessive accumulation of soil nutrients. The ARS and Western Kentucky University scientists collaborated in a remediation study to examine if inorganic fertilizer application over the residual fertility of broiler litter would reduce surplus soil nutrients by orchardgrass from nutrient enriched soil and by removing the resulting biomass from the study area. Three remediation treatments; inorganic fertilizer on antecedent broiler litter at the N rate, P rate, P rate with inorganic N, and inorganic fertilizer were tested. Repeated broiler litter application at N rate led to elevate soil P, copper (Cu), and Zn contents >200% from the initial levels. Implementing an alternative inorganic fertilizer application cycle in such soils can reduce P, Cu, and Zn levels respectively by 32 mg P kg-1 yr-1, 1.9 mg Cu kg-1 yr-1, and 2.4 mg Zn kg-1 yr-1. Remediation by inorganic fertilizer application may take at least 5 yrs to reduce P, Cu, and Zn levels back to the normal range. In addition, inorganic fertilizer application over broiler litter at N rate can offer similar forage production as inorganic fertilizer and N rate broiler litter amendment. An alternative cycle of inorganic fertilizer application after broiler litter amendment can be recommended as a best management practice to remediate surplus soil nutrients in highly broiler litter impacted soils while assuring high forage production benefits.
High genotypic and phenotypic diversity of Escherichia (E.) coli in livestock manures and water sources. Many federal, state and local regulatory agencies use E. coli as an indicator for the presence of fecal pathogens, whether bacteria, viruses, or protozoa. Understanding the ecology of this important organism is needed so more accurate protocols for monitoring may be developed. ARS scientists in the Animal Waste Management Research Unit (AWMRU) Lab at Bowling Green, KY, determined the genetic profiles of 1,346 E. coli isolates and transport properties of representatives from poultry, swine and cattle manure, and from a polluted creek in rural Kentucky. Working in collaboration with Kentucky Division of Water and Western Kentucky University, ARS researchers found that there was a high degree of diversity in the environmental transport potential and in genetic factors present in E. coli strains both within an environment (i.e. dairy manure) and between different environments (i.e., dairy manure and swine manure). This diversity should be taken into consideration by any researcher or regulatory agency when using only a few E. coli isolates for purposes of modeling, source tracking and risk assessment.
Soil nutrients, veterinary pharmaceuticals, and bacterial populations on a cattle feedlot are concentrated in feeding and dirt areas. Beef cattle backgrounding operations that grow out weaned calves for feedlot finishing can become sources of environmental contaminants. Better understanding of these contaminants and their distribution will aid in development of effective contaminant management guidelines for sustainable livestock production. ARS scientists in the Animal Waste Management Research Unit (AWMRU) Lab at Bowling Green, KY, and the Environmental Management and By-Product Utilization (EMBU) Lab in Beltsville, MD, in collaboration with scientists from Western Kentucky University investigated the distribution of soil nutrients, bacteria, and veterinary pharmaceutical compounds across a small cattle operation in western KY. Researchers showed that all contaminants were highly concentrated in the feeder area and were low in grass strips leading to a retention basin and sink hole. Grazing pastures within small feedlots can offer effective hydrologic isolation for contaminants. Therefore, contaminant management plans for small feedlots should focus on feeder areas where nutrients, bacteria and pharmaceuticals are most concentrated.
Emission and plant uptake of trace elements and mercury (Hg) from application of flue gas desulfurization (FGD) materials as soil amendment. According to American Coal Ash Association, about 140 million metric tons of coal combustion by-products are produced annually, including FGD gypsum and waste byproducts from dry and wet scrubbers in the United States. When applied to soil as amendment, FGD gypsum is able to improve the yield of crops by providing plant nutrients, improve soil physical properties, increase water infiltration and storage, and reducing nutrient and sediment losses. ARS scientist in Bowling Green, KY, in collaboration with scientists from Western Kentucky University conducted field study to investigate the distribution of mercury (Hg) and other potentially hazardous elements emission to ambient air and uptake by surface vegetation following application of different FGD materials to soil. We found Hg released into the air and uptake in grass from all FGD material-treated soils was greater than the untreated soil. No Hg was detected in the leachate collected during the only 1-inch rainfall event that occurred throughout the 4-week testing period. In addition, this study demonstrates that considering only the amounts of trace elements uptake in surface vegetation may under estimate the overall release of the trace elements from FGD material-amended soils. It also shows, under the same soil conditions, the mobility of trace elements varies when FGD materials produced from different processes.
Heat fluxes and emission of malodorants from animal wastewater lagoons. Malodors from waste treatment lagoons are often a source of complaints. The concentrations of phenol-cresol and phenol-ethylphenol, two malodorants typical of animal manure were measured above a swine wastewater treatment lagoon. At the same time, measurement of air and water temperature, humidity, wind speed and solar radiation were also performed so that the environmental factors controlling release of malodors from waste treatment lagoons could be determined. The factors that best explained emission of these malodorants were evaporation from the lagoon surface and that portion of solar radiation available at the lagoon surface after subtracting that portion of the radiation used to heat the lagoon water. Emissions were found to be higher in the cool season than the warm season due to losses of malodorants that occurred early in the spring as the lagoon warmed. Results of this work are being used to determine appropriate models to estimate malodorant emissions from lagoons and devise techniques for the abatement of nuisance emissions.
Modeling emission of malodorants from waste treatment lagoons. Odors generated by large scale animal rearing operations are the foremost cause of complaints by people living in the vicinity. The wastes generated are largely stored and treated in facultative lagoons prior to land application. Using equations developed in a previous study, scientists with the Agricultural Research Service in Bowling Green, KY, and Western Kentucky University modeled emission of phenol-cresol, a typical manure malodorant, above a wastewater lagoon. The model, which relied on the variables of lagoon evaporation and radiation, predicted highest emissions of malodors during the months of March and April with steeply declining emissions thereafter. In this, the model agreed well with experimental data. During the study, there were no pronounced differences in microbial populations as determined by molecular quantification of bacterial genes. Results of this study suggest evaporative losses are largely responsible for determining malodorous emissions from wastewater lagoons.
Improvement in biogas quality by wastewater recirculation through a silicone membrane. Biogas is a mixture of methane, carbon dioxide and trace gases such as hydrogen sulfide produced by the anaerobic breakdown of organic matter. The methane in biogas represents a severely underutilized resource from animal manures. The principal reasons that biogas is not harvested from animal wastes has to do with its corrosive nature and the susceptibility of anaerobic digests to operational upsets due to poor acid-base buffering. Researchers with the Agricultural Research Service in Bowling Green, KY, recirculated wastewater through a silicone hose located in an external aeration tank to improve the quality of biogas produced by bacteria digesting swine manure. Carbon dioxide in biogas from treated swine wastewater was reduced by almost 80% compared to control wastewater digestions. This result was due to a decrease in acidity of the treated wastewater. This also resulted in increased capture of carbon dioxide in the form of bicarbonate anion in the treated wastewater, increasing wastewater buffering and rendering treated wastewater less susceptible to operational upsets due to poor buffering. This result demonstrates a simple means for improving biogas quality and increasing operational efficiency of anaerobic digesters.
Utilization of poultry litter for pesticide bioremediation. Researchers from ARS unit in Bowling Green, KY, along with scientists from university in Mexico conducted experiments to elucidate the stimulatory effect of poultry litter on the fungal growth. The goal of this study was to determine whether poultry litter could be utilized to support fungal and microbial growth in a mixture of pesticides. The results showed that poultry litter was able to enhance fungal growth better than vitamins in the presence of pesticide mixture. Therefore, poultry litter can serve as growth substrate for fungal growth and provide additional capable microflora for pesticide bioremediation. This can reduce cost quite substantially when replacing the required vitamins for growth with poultry litter at contaminated sites or treatment systems such as barrier walls. Based on these data, poultry litter can be used as nutrient source for bioremediation of pesticides in agricultural settings. As a result of this experimentation, application of this poultry amendment has been utilized on test plots and local crop lands with pesticide problems in Mexico.
Elucidating of the effect of different application methods on ammonia and Green House Gas (GHG) gas emissions. Researchers from ARS unit in Bowling Green, KY, along with scientists from the University of Kentucky conducted experiment to monitor the initial and subsequent ammonia and greenhouse gas emissions from three different liquid swine manure application methods at a farm in Kentucky which had been cropped in a no-till corn/soybean rotation, using flux chambers and a gas analyzer. Results showed that Surface spray method has the highest total greenhouse potency factor based on non-linear method of calculating flux follow by Aerway and Row injection methods during the first four hours after application. The Surface spray method emitted about four times more than the Aerway injection and about 31 times more than the row injection method in greenhouse potency factor. The Aerway injection method emitted greenhouse potency factor of about seven times more than the row injection. Based on these data, the types of swine effluent application can have a significant initial impact on the ammonia and greenhouse gas emissions. This is very critical in reducing ammonia and GHG emissions via different types of land application methods. The results from this experiment will serve as the guideline for delineating potential factors that may affect the emissions from these various land application methods of liquid livestock wastes.
Atmospheric concentrations measured at a dairy lagoon. The ambient ion monitor (AIM) method was used to detect gas and particle phase amines at a dairy lagoon in California. Previously, detection of reactive amines in-situ to agricultural waste management was only performed by detection of gases or aerosol phase and not both simultaneously. ARS scientists from Animal Waste Management Research Unit in Bowling Green, Kentucky, successfully performed the first in-situ amine detection at a dairy using simultaneous gas- and aerosol- detection. Data comparisons are ongoing with collaborating scientist from ARS-Ames, Iowa, Cal State University-Fresno, and Claremont McKenna College. The study showed that some amines (e.g. trimethylamine) partition into the aerosol phase near source but others (e.g. butylamine) do not and are only observed in the gas-phase. This information benefits both the scientific community (e.g. atmospheric modelers) and potentially regulatory agencies to help determine which amines are potentially important to consider in atmospheric chemistry rather than focusing on all compounds.
Sistani, K.R., Jn-Baptiste, M., Lovanh, N.C., Cook, K.L. 2011. Atmospheric emissions of N2O, CH4, and CO2 from different nitrogen fertilizers. Journal of Environmental Quality. 40:1797–1805.
Bolster, C.H., Abit Jr, S.M. 2012. Biochar pyrolyzed at two temperatures impacts E. coli transport through a sandy soil. Journal of Environmental Quality. 41(1):124-133.
Marcus, I.M., Bolster, C.H., Cook, K.L., Opot, S.R., Walker, S.L. 2012. Impact of growth conditions on transport behavior of E. coli. Journal of Environmental Monitoring. 14:984-991.
Tewolde, H., Sistani, K.R., Rowe, D.E. 2005. Broiler litter as a micronutrient source for cotton: concentrations in plant parts. Journal of Environmental Quality. 34:1697-1706.
Bjerklie, D.M., Dingman, L., Bolster, C.H. 2005. River discharge and general flow resistance in the manning and chezy equation revisited. Water Resources Research. 41, W11502.
Cook, K.L., Garland, J.L., Layton, A.C., Dionisi, H.M., Levine, L.F., Sayler, G.S. 2007. Effect of microbial species richness on community stability and community function in a model plant-based wastewater processing system. Microbial Ecology. 52:725-737.
Loughrin, J.H., Szogi, A.A., Vanotti, M.B. 2006. Reduction of malodorous compounds from liquid swine manure by a multi-staged treatment system. Applied Engineering in Agriculture. 22(6):867-873
Tewolde, H., Shankle, M.W., Sistani, K.R., Adeli, A., Rowe, D.E. 2008. No-till and conventional-till cotton response to broiler litter fertilization in an upland soil: lint yield. Agronomy Journal. 100:502-509.
Quintanar, A., Mahmood, R., Loughrin, J.H., Lovanh, N.C. 2008. A coupled mm5-noah land surface model-based assessment of sensitivity of planetary boundary variables to anomalous soil moisture conditions. Physical Geography. 29(1):54-78
Tewolde, H., Shankle, M., Adeli, A., Sistani, K.R., Rowe, D.E. 2009. Macronutrient concentration in plant parts of cotton fertilized with broiler Litter in a marginal upland Soil. Soil & Tillage Research. 105(1):1-11.
Sistani, K.R., Adeli, A., Tewolde, H. 2010. Apparent use efficiency of nitrogen and phosphorus from broiler litter applied to bermudagrass. Communications in Soil Science and Plant Analysis. 41(15):1873-1884.
Doerner, K., Cook, K.L., Mason, B. 2009. 3-Methylindole production is regulated in Clostridium scatologenes ATCC 25775. Letters in Applied Microbiology. 48:125-132.
Quintanar, A., Mahmood, R., Motley, M., Yan, J., Loughrin, J.H., Lovanh, N.C. 2009. Simulation of boundary layer trajectory dispersion sensitivity to soil moisture conditions: MM5 and noah-based investigation. Atmospheric Environment. 43:3774-3785.
Loughrin, J.H., Vanotti, M.B., Szogi, A.A., Lovanh, N.C. 2009. Evaluation of second-generation multistage wastewater treatment system for the removal of malodorous compounds from liquid swine waste. Journal of Environmental Quality. 38:1739-1748.
Cheng, C., Chang, Y., Sistani, K.R., Wang, Y., Lu, W., Lin, C., Dong, J., Hu, C., Pan, W. 2012. Mercury Emission and Plant Uptake of Trace Elements during Early Stage of Soil Amendment Using Flue Gas Desulfurization Materials. Journal of Air and Waste Management Association. 62(2):139-150.