Progress 07/01/10 to 09/30/14
Outputs
Target Audience: The primary target audience for this reporting period is scientists, policy makers, and agricultural stakeholders involved in the use of pharmaceuticals in animal agriculture. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research project has provided training and professional development for two graduate students, one postdoc, and one visiting scholar. All four individual were involved in conducting this research in order to provide field and laboratory training in soil chemistry. In addition presentations at International Conferences (SSSA, graduate students) and our own lab meetings (all students) serves to assist in professional development for these young scientists. How have the results been disseminated to communities of interest? The results have been disseminated through peer-reviewed publications and presentations at conferences. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
A. Pharmaceutical transport from soil to groundwater Research continued to examine the potential transport of monensin in a field soil irrigated with lagoon water at a typical California dairy. This project was conducting near Fresno, CA using groundwater monitoring wells installed around a dairy and adjacent to an irrigation field which allowed for the investigation of monensin transport to groundwater as a direct result of irrigation with lagoon water. Analysis of our collected data demonstrate that there is low risk for monensin to reach groundwater following a single irrigation event. This is despite the fact that the ground water elevation is altered with irrigation and salts and dissolved organic matter are transported. Groundwater modeling with Hydrus is not being conducted to provide complimentary data for this study. B. Sorption of pesticides to soils and biochar Two separate studies were conducted to examine the sorption of pesticides under laboratory conditions. The first study investigated the sorption of phenylurea pesticides to various biochars. The second examines the abiotic partitioning of clothianidin under simulated rice field conditions. The sorption behavior of three phenylurea herbicides (monuron, diuron, linuron) on five biochars (Enhanced Biochar, Hog Waste, Turkey Litter, Walnut Shell and Wood Feedstock) and an agricultural soil (Yolo silt loam) was investigated using a batch equilibration method. Sorption isotherms of herbicides to biochars were well described by the Freundlich model (R2 = 0.93 -- 0.97). The adsorption KF values ranged from 6.94 to 1306.95 mg kg-1 and indicated the sorption of herbicides in the biochars and Yolo soil was in the sequence of linuron > diuron > monuron and Walnut Shell biochar > Wood Feedstock biochar > Turkey Litter biochar > Enhanced Biochar > Hog Waste biochar > Yolo soil. These data show that sorption of herbicides to biochar can have both positive (reduced off-site transport) and negative (reduced herbicide efficacy) implications and specific biochar properties, such as H/C ratio and surface area, should be considered together with soil type, agriculture chemical and climate condition in biochar application to agricultural soil to optimize the system for both agricultural and environmental benefits. Clothianidin is used in rice production to control the rice seed midge, Crictopus sylvestris, and the rice water weevil, Lissorhoptrus oryzophilus. Soils were collected from the Sacramento Valley and sorption affinity was measured. Results suggest sorption primarily occurs to the organic matter and has potential to be mobile in the environment.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Parikh, S.J., A.J. Margenot, F.N.D. Mukome, F. Calder�n, and K.W. Goyne. 2014. Soil Chemical Insights Provided through Vibrational Spectroscopy. Adv. Agron. 129:1-148.
- Type:
Journal Articles
Status:
Other
Year Published:
2014
Citation:
Mukome, F.N.D., A.L.D. Kilcoyne, and S.J. Parikh. 2014. Alteration of biochar carbon chemistry during soil incubations: SR-FTIR and NEXAFS investigation. Soil Sci. Soc. Amer. J.�78:1632-1640.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Mulligan, R.A., S.J. Parikh, R.S. Tjeerdema. 2014. Abiotic Partitioning of Clothianidin Under Simulated Rice Field Conditions. Pest Manag. Sci. Available online.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Hafner, S.C., T., Harter, and S.J. Parikh. Transport of Monensin to a California Dairy. 2014. Soil Science Society of America International Meetings. November 2-5, Long Beach, CA.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: The primary target audience for this reporting period is scientists, policy makers, and agricultural stakeholders involved in the use of pharmaceuticals in animal agriculture. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research project has provided training and professional development for two graduate students and two undergraduate students. All four individual were involved in conducting this research in order to provide field and laboratory training in soil chemistry. In addition presentations at International Conferences (SSSA, graduate students) and our own lab meetings (all students) serves to assist in professional development for these young scientists. How have the results been disseminated to communities of interest? The results have been disseminated through peer-reviewed publications and presentations at conferences. What do you plan to do during the next reporting period to accomplish the goals? Proposed project activities include: 1. Laboratory research to investigate binding of pharmaceuticals to soil and various mineral phases; 2. Field research to examine the fate of pharmaceuticals land applied under conditions simulating irrigation of pasture; 3. Prepare manuscripts for publication in order to disseminate research to communities of interest.
Impacts
What was accomplished under these goals?
A. Pharmaceutical transport from soil to groundwater The purpose of this project component was to investigate the potential transport of monensin in a field soil irrigated with lagoon water at a typical California dairy. This project was conducting near Fresno, CA using groundwater monitoring wells installed around a dairy and adjacent to an irrigation field which allowed for the investigation of monensin transport to groundwater as a direct result of irrigation with lagoon water. Monitoring wells were sampled periodically over six weeks during April and May. The on-site crop field was flood irrigated in early May. Monensin was isolated from water via solid phase extraction. Wells were also monitored for changes in pH, EC, water elevation, and anions and cations, including NO3- and NH4+. The data reveal that irrigation water does not reach groundwater after a single application, but pushes through existing soil water. Therefore, monensin does not transport to groundwater after a single manure-irrigation event. The data suggest that manure storage site and improper management techniques may be a more significant threat of monensin and other antibiotics to groundwater than irrigation. B. Impact of biochar on plant uptake of pharmaceuticals The primary objective of this project component was to examine the potential for biochar addition to biosolid-amended soil to minimize plant uptake of three widely used antibiotics (ciprofloxacin, triclocarban and triclosan) in carrots and lettuce. This research was conducted with carrots and lettuce grown in pots containing soil amended with pharmaceutical spiked biosolids (63 g/kg) and three treatments of walnut shell biochar were used (0, 10, 100 t/ha). The soil moisture was maintained at 60% water holding capacity and the plants were harvested after 60 days. The pharmaceuticals content in plant tissue was quantified in roots and shoots by high performance liquid chromatography/mass spectrometry. The data demonstrate that walnut shell biochar has a high sorption potential for our pharmaceuticals of interest. Additionally, no adverse effect on plant growth was seen in carrots and lettuce grown in soils amended with biosolids spiked with pharmaceuticals. This research demonstrates that the use of walnut shell biochar has potential to effectively mitigate the concentration of ciprofloxacin and triclocarban in the edible parts of lettuce and triclosan in the root of the carrot.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Popova, I.E., D.A. Bair, K.W. Tate, and S.J. Parikh. 2013. Sorption, Leaching, and Surface Runoff of Beef Cattle Veterinary Pharmaceuticals under Simulated Irrigated Pasture Conditions. J. Environ. Qual. 42: 1167-1175.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2013
Citation:
Bair, D.A., C. Anderson, K.M. Scow, S.J. Parikh. SSSA Impact of Biochar Co-Amendments On Plant Uptake of Antibiotics Found in Biosolids. Soil Science Society of America Annual Meetings. Nov. 3-6, Tampa, FL.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2013
Citation:
Hafner, S.C., T. Harter, D.M. Holstege, and S.J. Parikh. 2013. Acute Transport of Monensin to Groundwater at a California
Dairy. Soil Science Society of America Annual Meetings. Nov. 3-6, Tampa, FL.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Mukome, F.N.D., X. Zhang, L.C.R. Silva, J. Six, and S.J. Parikh. 2013. Use of chemical and physical characteristics to investigate trends in biochar feedstocks.�J. Agric. Food. Chem. 61:2196-2204.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Mukome, F.N.D., L.E. Emberson, and S.J. Parikh. Biochar Database: An Open-Access Resource to the Black Continuum. Soil Science Society of America Annual Meetings.�Nov. 3-6, Tampa, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Mukome, F.N.D., X. Zhang, L.C.R. Silva, J. Six, and S.J. Parikh. Use of Chemical and Physical Characteristics to Investigate Trends in Biochar Feedstocks. Soil Science Society of America Annual Meetings.�Nov. 3-6, Tampa, FL.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Outcomes for this project include presentations at the national and regional meetings. A. Soil Science Society of America National Meetings: Bair, D.A., I.E. Popova, K.W. Tate, and S.J. Parikh. 2012. Sorption, Leaching and Surface Runoff of Rangeland Veterinary Pharmaceuticals From Soil Boxes. Soil Science Society of America National Meetings. October 21-24, Cincinnati, OH. Parikh, S.J., I.E. Popova, D.A. Bair, and K.W. Tate. 2012. Transport of Veterinary Antibiotics in Surface Runoff From Irrigated Pastures. Soil Science Society of America National Meetings. October 21-24, Cincinnati, OH. Popova, I. and S.J. Parikh. Pressurized liquid extraction of chlortetracycline and oxytetracycline from soil with in-cell cleanup. HPLC 2012. June 16-21, Anaheim, CA. B. Western Soil Science Society and the West Regional Cooperative Soil Survey Conference: Popova, I.E. D.A. Bair, K.W. Tate, and S.J. Parikh. 2012. Leaching of veterinary pharmaceuticals from manure amended soils: Packed soil boxes study. Joint Meeting Western Soil Science Society and the West Regional Cooperative Soil Survey Conference. June 25-27, Davis, CA. Bair, D.A., F.N.D. Mukome, A. Jefferson, T.M. Young, and S.J. Parikh. 2012. How do biochar and biosolid co-amendments impact the mobility of pharmaceuticals, heavy metals, and herbicides in soils Joint Meeting Western Soil Science Society and the West Regional Cooperative Soil Survey Conference. June 25-27, Davis, CA. C. California Plant and Soil Conference Parikh, S.J., F.N.D. Mukome, E. Suddick, E.I.P. Pereira, E. Verhoeven, and J.W. Six. 2012. Investigating Potential Benefits of Soil Biochar Amendments. California Plant and Soil Conference, American Society of Agronomy, CA Chapter. Feb. 7-8, Visalia, CA. Bair, D.A., T.M. Young, and S.J. Parikh. 2012. Can Biochar Reduce Mobility of Pharmaceuticals in Biosolid Amended Soils California Plant and Soil Conference, American Society of Agronomy, CA Chapter. Feb. 7-8, Visalia, CA. D. A presentation as the USDA-AFRI project directors meeting in 2012: Tate, K., E.P. Kolodziej, R. Atwill, A. Craigmill, T. O'Geen, D. Holstege, S.J. Parikh, and G.D. Jones. 2011. Transport and Mitigation of Beef Cattle Veterinary Pharmaceuticals and Hormones PARTICIPANTS: Thomas Harter (Faculty, UCD) Edwared Kolodziej (Faculty, UN Reno) Toby O'Geen (Faculty, UCD) Ken Tate (Faculty, UCD) Thomas Young (Faculty, UCD) Johan Six (Faculty, UCD) Kate Scow (Faculty, UCD) Daoyuan Wang (Visiting Scholar, UCD) Fungai Mukome (Postdoctoral Scholar, UCD) Ina Popova (Postdoctoral Scholar, UCD) Danny Bair (PhD Student, UCD) Sarah Hafner (PhD Student) Training and professional development of graduate and undergraduate students and postdoctoral scholars has been an important part of this project. To date training has focused on development of experimental protocols, chemical analysis techniques, and critical evaluation of data. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A.Examining pharmaceutical transport via surface runoff on irrigated pasture.A series of experiments have been conducted using packed soil boxes and surface runoff plots to study the potential for pharmaceutical via surface runoff from irrigated rangeland. One manuscript from these efforts has been submitted for publication and another is currently in preparation.Impact: The use of veterinary pharmaceuticals in beef cattle in grazed watersheds has lead to concerns associated with the development of antibiotic resistance in bacteria and endocrine disruption in aquatic organisms. The objective of this study was to assess the transport of common beef cattle pharmaceuticals (i.e., oxytetracycline, chlortetracycline, ivermectin) via surface runoff and leachate from manure-amended grass vegetated soil boxes under irrigated pasture conditions. The transport of pharmaceuticals from animal manure as surface runoff and soil leachate was relatively low and appears to be limited by desorption and transport of pharmaceuticals entrained in the manure.B. Investigating the impact of biochar soil amendments on pesticide and pharmaceutical transport in soil.Experiments have been completed to examine the sorption of pharmaceuticals and pesticides to soil (Yolo silt loam), soil minerals (kaolinite), biosolids, biochar (wood feedstock and walnut shell), and activated carbon. We investigated a fluoroquinolone antibiotic (i.e., ciprofloxacin) used in human medicine and phenylurea pesticides (i.e., linuron, diuron, monuron). A manuscript is in prepration for publication of these results.Impact: Land application of biosolids can transfer pharmaceutical compounds and their degradation products to the soil environment, allowing for potential bioavailability. Biochar, a co-product of biofuel production, has potential to stabilize biosolid C, N, and P in soil, increase soil fertility and crop yield, and attenuate heavy metals, agrochemicals, and pharmaceuticals. Due to its chemical composition, biochars are favorable absorbents for many pharmaceuticals and pesticides. The use of biochar as a co-amendment with biosolids has potential to provide important benefits to agroecosystems by reducing contaminant mobility and improving soil fertility.C.Sorption and facilitated transport of common veterinary antibiotics to soil minerals.Our preliminary sorption data reveals no sorption of sulfamethazine to mineral phases studied besides birnessite and therefore suggest transport through soil. For monensin, of the minerals evaluated, only goethite was shown to bind monensin.Impact: The ionophore, monensin, is commonly used as a growth promoter as it is believe to increase feed absorption efficiency; however, to date little is known about its reactivity in soil. While monensin is an effective antibiotic at the correct dose, the difference between a therapeutic and toxic dose is very small, and toxicity varies widely between species. Understanding the specific mechanisms of monensin sorption and degradation in soil will help predict its transport in the environment and provide guidelines for its use in animal agriculture.
Publications
- Mukome, F.N.D., X. Zhang, L.C.R. Silva, J. Six, and S.J. Parikh. 2013. Use of chemical and physical characteristics to investigate trends in biochar feedstocks. J. Agric. Food. Chem. In press. DOI: 10.1021/jf3049142.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Outcomes for this project include presentations at the national meeting of the Soil Science Society of America: Parikh, S.J., A. Jefferson, N. Ghazal, X.E., Zhang, D.A. Bair, and F.N.D. Mukome. 2011. Soil Science Society of America Annual Meeting. Oct. 16-19, San Antonio, TX. Hafner, S., and S.J. Parikh. 2011. Binding and Degradation of Monensin by Soil Minerals. Soil Science Society of America Annual Meeting. Oct. 16-19, San Antonio, TX. A presentation as the USDA-AFRI project directors meeting in 2011: Tate, K., E.P. Kolodziej, R. Atwill, A. Craigmill, T. O'Geen, D. Holstege, S.J. Parikh, and G.D. Jones. 2011. Transport and Mitigation of Beef Cattle Veterinary Pharmaceuticals and Hormones An overview talk of the subject addressed by this project was also given Plant and Soil Conference of the CA chapter of the Agronomy Society of America. This talk provided an opportunity for outreach to the CA agricultural stake holders. Parikh, S.J. 2011. Understanding the Fate of Antibiotics in Concentrated Animal Feeding Operations. Plant and Soil Conference, American Society of Agronomy, CA Chapter. Feb. 1-2, Fresno, CA. PARTICIPANTS: Thomas Harter (Faculty, UCD) Edwared Kolodziej (Faculty, UN Reno) Toby O'Geen (Faculty, UCD) Ken Tate (Faculty, UCD) Thomas Young (Faculty, UCD) Fungai Mukome (Postdoctoral Scholar, UCD) Ina Popova (Postdoctoral Scholar, UCD) Christopher Alaimo (Staff Research Associate, UCD) Danny Bair (PhD Student, UCD) Sarah Hafner (PhD Student) Allie Jefferson (Undergraduate Student, UCD) Training and professional development of graduate and undergraduate students and postdoctoral scholars has been an important part of this project. To date training has focused on development of experimental protocols, chemical analysis techniques, and critical evaluation of data. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A. Examining transport of veterinary antibiotics from California dairies to groundwater This study investigates the potential for rapid transport of antibiotics present within land applied dairy lagoon water to a shallow groundwater aquifer. Groundwater samples were obtained from two monitoring wells in one nineteen day sampling campaign conducted in September 2010 concurrent with fertigation of an agricultural field at a dairy facility in the Central Valley of California. Eight common veterinary antibiotics (oxytetracycline, chlortetracycline, sulfamethazine, sulfamerazine, sulfadiazine, sulfamethoxazole, sulfadimethoxine, and monensin) used in the dairy industry were targeted for analysis. Analysis of groundwater and irrigation water samples collected from the agricultural field confirmed the occurrence of several target analytes in the samples; however, the results suggest that antibiotics were present before the irrigation season and indicate persistence in the groundwater. Impact: Groundwater contamination from concentrated animal feeding operations (CAFOs) is a potential environmental problem. The primary concern with environmental loading of antibiotics from dairy CAFOs is the potential for an increase in antibiotic resistance of pathogenic bacteria. Although antibiotics introduced into the environment have the potential to produce this harmful side effect, the behavior of these compounds in soil remains poorly understood. The results from this research confirm that antibiotics can reach groundwater sources, but indicate that rapid transport is not likely. Instead, upon irrigation, a flush of the soil column occurs and antibiotics from the soil are transported to groundwater. B. Sorption and facilitated transport of common veterinary antibiotics to soil minerals Sorption experiments for the two antibiotics most commonly found (i.e., monensin, sulfamethazine) in groundwater samples provide additional insight into the field scale transport mechanisms of veterinary antibiotics. Our preliminary sorption data reveals no sorption of sulfamethazine to mineral phases studied besides birnessite and therefore suggest transport through soil. For monensin, of the minerals evaluated, only goethite was shown to bind monensin. Impact: Although a great deal is already known regarding the sorption and transport of antibiotics in soil the specific mechanisms of sorption for certain antibiotics remains poorly understood. The ionophore, monensin, is commonly used as a growth promoter as it is believe to increase feed absorption efficiency; however, to date little is known about its reactivity in soil. Monensin is commonly used in poultry and beef cattle, and was recently approved for use in dairy cattle in the U.S., where it is used to increase lactation. While monensin is an effective antibiotic at the correct dose, the difference between a therapeutic and toxic dose is very small, and toxicity varies widely between species. Understanding the specific mechanisms of monensin sorption and degradation in soil will help predict its transport in the environment and provide guidelines for its use in animal agriculture.
Publications
- No publications reported this period
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Outcomes for this project include presentations at the national meeting of the Soil Science Society of America: Bair, D., and S.J. Parikh. 2010. Adsorption and Transformation of Ivermectin with Soil Minerals. Soil Science Society of America Annual Meeting. Oct. 31 - Nov. 3, Long Beach, CA. Hafner, S., and S.J. Parikh. 2010 Mechanisms of Binding and Abiotic Degradation of Sulfamethazine to Iron and Manganese Oxides. Soil Science Society of America Annual Meeting. Oct. 31 - Nov. 3, Long Beach, CA. A presentation as the USDA-AFRI project directors meeting in 2011: Tate, K., E.P. Kolodziej, R. Atwill, A. Craigmill, T. O'Geen, D. Holstege, S.J. Parikh, and G.D. Jones. 2011. Transport and Mitigation of Beef Cattle Veterinary Pharmaceuticals and Hormones An overview talk of the subject addressed by this project was also given Plant and Soil Conference of the CA chapter of the Agronomy Society of America. This talk provided an opportunity for outreach to the CA agricultural stake holders. Parikh, S.J. 2011. 2011. Understanding the Fate of Antibiotics in Concentrated Animal Feeding Operations. Plant and Soil Conference, American Society of Agronomy, CA Chapter. Feb. 1-2, Fresno, CA. PARTICIPANTS: Thomas Harter (Faculty, UCD) Edwared Kolodziej (Faculty, UN Reno) Toby O'Geen (Faculty, UCD) Ken Tate (Faculty, UCD) Thomas Young (Faculty, UCD) Fungai Mukome (Postdoctoral Scholar, UCD) Christopher Alaimo (Staff Research Associate, UCD) Danny Bair (PhD Student, UCD) Lina Bachert (MS Student, Univ. Duisburg-Essen, Germany) Sarah Hafner (PhD Student) Brian Mathison (MS Student, UCD) Allie Jefferson (Undergraduate Student, UCD) Training of graduate and undergraduate students has been a specific component of this project. Training has focused on method for analysis of agrochemicals in soil and water samples. Protocols have largely followed EPA specific methods but have been modified for our specific research projects and equipment. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Animal agriculture is the primary source of antibiotics to the environment, specifically through waste products generated by concentrated animal feeding operations (CAFOs), facilities containing a large number of domestic animals. In facilities with high concentrations of animals in confined areas, subtherapeutic levels of antibiotics are often administered to the animals to prevent the spread of disease. Most of the antibiotics given to livestock are not absorbed or metabolized in the gut, and instead pass chemically unchanged in the excreta. Animal waste products from dairy CAFOs are often stored on-site in lagoons until applied to agricultural land as a fertilizer, where antibiotics are can be introduced to the environment. The primary concern with environmental loading of antibiotics from dairy CAFOs is the potential for an increase in antibiotic resistance in human pathogens, as the antibiotics used in feed animals are often very similar or identical to those used to treat human ailments. Although antibiotics introduced into the environment have the potential to produce this harmful side effect, little is known about the behaviors of these compounds in soil. Limiting development bacterial antibiotic resistance from land application of dairy manure is contingent on understanding how these antibiotics bind or degrade in soil systems. Laboratory batch experiments have been performed using pure minerals such as goethite and birnessite, iron and manganese oxides. These minerals are redox active minerals common to soils and are known to play a role in sorption and degradation of organic compounds. Liquid chromatography tandem mass spectrometry and Fourier transform infrared spectroscopy have been used to investigate possible binding and degradation of sulfamethazin in the presence of these mineral oxides. Results from research in our laboratory is demonstrating interesting abiotic pathways for antibiotic degradation. For example reaction of sulfamethazine with birnessite, a common soil manganese oxide, for just 30 minutes leads oxidation and transformation to a variety of degradation products and the parent compound cannot be detected in solution via liquid chromatography mass spectroscopy analysis. Other results demonstrate rapid, but not complete, degradation of ivermectin via a photo-oxidation pathway. Additional research: 1) rapid transport of antibiotics to groundwater from fertigation with liquid dairy manure; 2) transport of antibiotics from cattle via surface runoff on irrigated rangeland; 3) sorption of oxytetracycline to soils with varied parent material and organic matter contents; and 4) the sorption and remediation of pharmaceuticals in biosolids applied to agricultural land through biochar amendments. A large portion of our efforts have been focused on developing laboratory methods for analysis of agrochemicals specific for our research projects. Additionally, we have been training graduate students to use instrumentation, design experiments, and analyze data. Being a relatively new laboratory, it is required that we create a firm knowledge base and skill set for the laboratory related to procedures related to this project.
Publications
- Parikh, S.J. 2011. 2011. Understanding the Fate of Antibiotics in Concentrated Animal Feeding Operations. Proceedings of the Plant and Soil Conference, American Society of Agronomy, CA Chapter. Feb. 1-2, Fresno, CA.
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