Publications

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    ABSTRACT: The natural manure-borne hormones, 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), and estrone (E1), are routinely detected in surface water near agricultural land and wastewater treatment facilities. Once in the stream network, hormones may enter the sediment bed where they are subject to anaerobic conditions. This study focuses on the difference in anaerobic transformation rates and formation of metabolites from 17α-E2, 17β-E2, and E1 (applied at ~3.66 mol kg-1 of sediment on a dry weight basis) under nitrate- and sulfate-reducing conditions. Sediment extracts were analyzed using negative electrospray ionization tandem mass spectrometry. Under both redox conditions, degradation was stereospecific and followed similar trends in half-lives: 17β-E2 < 17α-E2 < E1, with degradation considerably slower under sulfate-reducing conditions. Both E2 isomers were predominantly converted to E1; however, isomeric conversion also occurred with peak concentrations of ~1.7 mol% of 17β-E2 formed in 17α-E2 amended soils and peak concentrations of ~2.4 mol% of 17α-E2 formed from 17β-E2. In E1-amended systems, E1 transformed to E2 with preferential formation of the more potent 17β isomer up to ~30 mol% suggesting that isomer interconversion is through E1. Sediments, therefore, may serve as both a sink and a source of the more estrogenic compound E2. Transformation of amended hormones in autoclaved sediments was markedly slower than in non-autoclaved sediments. Results support the inclusion of isomer-specific behavior and the potential for reversible transformation and interconversion in anaerobic sediments in modeling fate in stream networks and developing risk management strategies.
    Environmental Science & Technology 05/2013; · 5.48 Impact Factor
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    ABSTRACT: Aerobic biodegradation of 8:2 fluorotelomer stearate (FTS) and 8:2 fluorotelomer citrate triester (TBC) was evaluated in a forest soil in closed bottle microcosms. Loss of parent, production of 8:2 fluorotelomer alcohol (8:2 FTOH), which is released along with stearic acid (SA) by microbial ester linkage, and subsequent metabolites from FTOH degradation were monitored for up to 7months. Soil microcosms were extracted with ethyl acetate followed by two heated 90/10 v/v acetonitrile/200mM NaOH extractions. Cleavage of the ester linkage in the 8:2 FTS occurred (t(1/2)∼28d), producing 8:2 FTOH and various levels of subsequent metabolites. Quantifying the generation of SA from ester cleavage in FTS was complicated by the natural production and degradation of SA in soil, which was probed in an additional FTS and SA study with the same soil that had been stored at 4°C for 12months. In the latter study, FTS degraded faster (t(1/2)∼5d) such that SA production well above soil background levels was clearly observed along with rapid subsequent SA degradation. Cold storage was hypothesized to enrich fungal enzymes, which are known to be effective at hydrolytic cleavage. 8:2 TBC biotransformation was slow, but evident with the production of PFOA well above levels expected from known FTOH residuals. Slower degradation of TBC compared to FTS is likely due to steric hindrances arising from the close proximity of three 8:2 FT chains on the citrate backbone limiting the enzyme access.
    Chemosphere 01/2013; · 3.14 Impact Factor
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    ABSTRACT: The use of single-wall carbon nanotubes (SWNTs) in manufacturing and biomedical applications is increasing at a rapid rate; however data on the effects of a potential environmental release of the materials remain sparse. In this study, soils with either low or high organic matter contents as well as pure cultures of E. coli are challenged with either raw As-Produced SWNTs (AP-SWNTs) or SWNTs functionalized with either polyethyleneglycol (PEG-SWNTs) or m-polyaminobenzene sulfonic acid (PABS-SWNTs). To mimic chronic exposure, the soil systems were challenged weekly for six weeks; microbial activities and community structures for both the prokaryote and eukaryote community were evaluated. Results show that repeated applications of AP-SWNTs can affect microbial community structures and induce minor changes in soil metabolic activity in the low organic matter systems. Toxicity of the three types of SWNTs was also assessed in liquid cultures using a bioluminescent E. coli-O157:H7 strain. Although decreases in light were detected in all treated samples, low light recovery following glucose addition in AP-SWNTs treatment and light absorption property of SWNTs particles suggest that AP-SWNTs suppressed metabolic activity of the E. coli, while the two functionalized SWNTs are less toxic. The metals released from the raw forms of SWNTs would not play a role in the effects seen in soil or the pure culture. We suggest that sorption to soil organic matter plays a controlling role in the soil microbiological responses to these nanomaterials.
    Environmental Science & Technology 11/2012; · 5.48 Impact Factor
  • R F Turco, M Bischoff, Z H Tong, L Nies
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    ABSTRACT: A fundamental lack of data on the potential impacts of carbon based nanomaterials on natural ecosystems currently exists. The gap between what we know about environmental impacts and new products that may contain nanomaterials continues to get wider especially related to knowledge about nanocomposites. In this paper we present ideas and concerns about the current state of knowledge on nanomaterials in the environment and present a number of points about what recent work has provided us about the novel materials.
    Current opinion in biotechnology 08/2011; 22(4):527-32. · 7.82 Impact Factor
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    ABSTRACT: Artificial subsurface drainage in cropland creates pathways for nutrient movement into surface water; quantification of the relative impacts of common and theoretically improved management systems on these nutrient losses remains incomplete. This study was conducted to assess diverse management effects on long-term patterns (1998-2006) of NO, NH, and PO loads (). We monitored water flow and nutrient concentrations at subsurface drains in lysimeter plots planted to continuous corn ( L.) (CC), both phases of corn-soybean [ (L.) Merr.] rotations (corn, CS; soybean, SC), and restored prairie grass (PG). Corn plots were fertilized with preplant or sidedress urea-NHNO (UAN) or liquid swine manure injected in the fall (FM) or spring (SM). Restored PG reduced NO eightfold compared with fields receiving UAN (2.5 vs. 19.9 kg N ha yr; < 0.001), yet varying UAN application rates and timings did not affect NO across all CCUANs and CSUANs. The NO from CCFM (33.3 kg N ha yr) were substantially higher than for all other cropped fields including CCSM (average 19.8 kg N ha yr, < 0.001). With respect to NH and PO, only manured soils recorded high but episodic losses in certain years. Compared with the average of all other treatments, CCSM increased NH in the spring of 1999 (217 vs. 680 g N ha yr), while CCFM raised PO in the winter of 2005 (23 vs. 441 g P ha yr). Our results demonstrate that fall manuring increased nutrient losses in subsurface-drained cropland, and hence this practice should be redesigned for improvement or discouraged.
    Journal of Environmental Quality 01/2011; 40(4):1229-40. · 2.35 Impact Factor
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    ABSTRACT: Mycobacterium avium subsp paratuberculosis (Map), the causative agent of Johne's disease, has a robust ability to survive in the environment. However, the ability of Map to migrate through soil to drainage tiles or ground water, leave the farm, and leak into local watersheds is inadequately documented. In order to assess the ability of Map to leach through soil, two laboratory experiments were conducted. In the first study, 8 columns (30 cm long each) of a sandy loam soil were treated with pure cultures of Map. Two soil moisture levels and two Map concentrations were used. The columns were leached with 500 mL of water once a week for three weeks, the leachate was collected, and detection analysis was conducted. In the second experiment, manure from Map negative cows (control) and Map high shedder cows (treatment) were deposited on 8 similar columns and the columns were leached with 500 mL of water once a week for four weeks. Map detection and numeration in leachate samples were done with RT-PCR and culture techniques, respectively. Using RT-PCR, Map could be detected in the leachates in both experiments for several weeks but could only be recovered using culture techniques in experiment one. Combined, these experiments indicate the potential for Map to move through soil as a result of rainfall or irrigation following application.
    Veterinary medicine international. 01/2011; 2011:506239.
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    ABSTRACT: To better protect consumers from exposure to produce contaminated with Escherichia coli, the potential transfer of E. coli from manure or irrigation water to plants must be better understood. We used E. coli strains expressing bioluminescence (E. coli O157:H7 lux) or multiantibiotic resistance (E. coli²(+)) in this study. These marked strains enabled us to visualize in situ rhizosphere colonization and metabolic activity and to track the occurrence and survival of E. coli in soil, rhizosphere, and phyllosphere. When radish and lettuce seeds were treated with E. coli O157:H7 lux and grown in an agar-based growth system, rapid bacterial colonization of the germinating seedlings and high levels of microbial activity were seen. Introduction of E. coli²(+) to soil via manure or via manure in irrigation water showed that E. coli could establish itself in the lettuce rhizosphere. Regardless of introduction method, 15 days subsequent to its establishment in the rhizosphere, E. coli²(+) was detected on the phyllosphere of lettuce at an average number of 2.5 log CFU/g. When E. coli²(+) was introduced 17 and 32 days postseeding to untreated soil (rather than the plant surface) via irrigation, it was detected at low levels (1.4 log CFU/g) on the lettuce phyllosphere 10 days later. While E. coli²(+) persisted in the bulk and rhizosphere soil throughout the study period (day 41), it was not detected on the external portions of the phyllosphere after 27 days. Overall, we find that E. coli is mobile in the plant system and responds to the rhizosphere like other bacteria.
    Journal of food protection 11/2010; 73(11):2001-9. · 1.83 Impact Factor
  • International Annual Meeting American Society of Agronomy/ Crop Science Society of America/ Soil Science Society of America 2009; 11/2009
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    ABSTRACT: Nanoparticles are being used in many commercial applications. We describe the toxicity of two commercial silver (Ag) nanoparticle (NP) products, NanoAmor and Sigma on Pimephales promelas embryos. Embryos were exposed to varying concentrations of either sonicated or stirred NP solutions for 96 h. LC(50) values for NanoAmor and Sigma Ag NPs were 9.4 and 10.6 mg/L for stirred and 1.25 and 1.36 mg/L for sonicated NPs, respectively. Uptake of Ag NPs into the embryos was observed after 24 h using Transmission Electron Microscopy and Ag NPs induced a concentration-dependent increase in larval abnormalities, mostly edema. Dissolved Ag released from Ag NPs was measured using Inductively Coupled-Mass Spectrometry and the effects tested were found to be three times less toxic when compared to Ag nitrate (AgNO(3)). The percentage of dissolved Ag released was inversely proportional to the concentration of Ag NPs with the lowest (0.625 mg/L) and highest (20 mg/L) concentrations tested releasing 3.7 and 0.45% dissolved Ag, respectively and percent release was similar regardless if concentrations were stirred or sonicated. Thus increased toxicity after sonication cannot be solely explained by dissolved Ag. We conclude that both dissolved and particulate forms of Ag elicited toxicity to fish embryos.
    Ecotoxicology 10/2009; 19(1):185-95. · 2.77 Impact Factor
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    ABSTRACT: An enrichment culture approach was used to isolate a pure culture of the yeast Lipomyces kononenkoae, which had the ability to grow on the herbicide picloram. The yeast rapidly and completely degraded 50 microg mL(-1) picloram by 48 h of growth. While L. kononenkoae was found to use both N atoms of picloram as a sole nitrogen source for growth, it failed to mineralize the herbicide or use it as a sole C source. Product analysis done using LC-ESI-MS indicated that biodegradation of picloram by L. kononenkoae proceeds via a didechlorinated, dihydroxylated, pyridinecarboxylic acid derivative. Our results are consistent with the hypothesis that the majority of picloram degradation in the soil is likely due to microbial catabolic processes.
    Journal of Agricultural and Food Chemistry 07/2009; 57(11):4878-82. · 3.11 Impact Factor
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    ABSTRACT: Artificial subsurface drainage is commonly used in midwestern agriculture and drainage losses of dissolved organic carbon (DOC) from such systems are an under-quantified portion of the terrestrial carbon (C) cycle. The objectives of this study were to determine the effect of common agricultural management practices on DOC losses from subsurface tile drains and to assess patterns of loss as a function of year, time of year, and drainflow. Daily drainflow was collected across six water years (1999-2004) from a restored prairie grass system and cropping systems which include continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr.] rotations fertilized with urea-ammonium-nitrate (UAN) or swine (Sus scrofa) manure lagoon effluent. The DOC concentrations in tile drainflow were low, typically <2 mg L(-1). Yearly DOC losses, which ranged from 1.78 to 8.61 kg ha(-1), were not affected by management practices and were small compared to organic C inputs. Spring application of lagoon effluent increased yearly flow-weighted (FW)-DOC concentrations relative to other cropping systems in three of the years and increased monthly FW-DOC concentrations when drainflow occurred within 1 mo of application. Drainflow was significantly and positively correlated with DOC loss. Drainflow also affected DOC concentrations as greater 6-yr cumulative drainflow was associated with lower 6-yr FW-DOC concentrations and greater daily drainflow was associated with higher daily DOC concentrations. Our results indicate that lagoon effluent application and fertilizer N rates do not affect long-term losses of DOC from tile drains and that drainflow is the main driver of DOC losses.
    Journal of Environmental Quality 01/2009; 38(3):1205-15. · 2.35 Impact Factor
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    ABSTRACT: A prototype bioluminescence-based biosensor was designed and constructed to evaluate the antimicrobial efficacy of chlorine dioxide (ClO(2)) gas under various treatment conditions. The biosensor consisted of a bioluminescent bioreporter (Pseudomonas fluorescens 5RL), an optical transducer (photomultiplier tube), and a light-tight chamber housing, the bioreporter and the transducer. The bioluminescent recombinant P. fluorescens 5RL in the biosensor allowed for online monitoring of bioluminescence during ClO(2) gas disinfection. Experiments were performed to evaluate the effects of the two key physical parameters associated with ClO(2) disinfection: relative humidity (40, 60, 80%) and ClO(2) gas concentration (0.5, 1.0, 1.6, 2.1 mg/l) on the bioreporter. Results showed that increasing concentrations of ClO(2) gas corresponded to a faster decrease in luminescence. The rates of luminescence decrease from P. fluorescens 5RL, and the log reduction time (LRT, time required to obtain 1-log reduction in luminescence) were calculated for each treatment tested. The LRT values of luminescence were 103, 78, 53, and 35 s for 0.5, 1.0, 1.6, and 2.1 mg/l of ClO(2) gas treatment, respectively, at 78% relative humidity. The gas concentration which caused a tenfold change in LRT (z value) for luminescence of P. fluorescens 5RL was 3.4 mg/l of ClO(2). The prototype biosensor showed potential for many applications, such as monitoring real-time microbial inactivation and understanding parameters that influence the efficacy of gaseous decontamination procedures.
    Applied Microbiology and Biotechnology 04/2008; 78(4):573-80. · 3.81 Impact Factor
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    Leila Nyberg, Ronald F Turco, Loring Nies
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    ABSTRACT: As the technological benefits of nanotechnology begin to rapidly move from laboratory to large-scale industrial application, release of nanomaterials to the environment is inevitable. Little is known about the fate and effects of nanomaterials in nature. Major environmental receptors of nanomaterials will be soil, sediment, and biosolids from wastewater treatment. Analysis of anaerobic microbial activity and communities provides needed information about the effects of nanoparticles in certain environments. In this study, biosolids from anaerobic wastewater treatment sludge were exposed to fullerene (C60) in order to model an environmentally relevant discharge scenario. Activity was assessed by monitoring production of CO2 and CH4. Changes in community structure were monitored by denaturing gradient gel electrophoresis (DGGE), using primer sets targeting the small subunit rRNA genes of Bacteria, Archaea, and Eukarya. Findings suggest that C60 fullerenes have no significant effect on the anaerobic community over an exposure period of a few months. This conclusion is based on the absence of toxicity indicated by no change in methanogenesis relative to untreated reference samples. DGGE results show no evidence of substantial community shifts due to treatment with C60, in any subset of the microbial community.
    Environmental Science and Technology 04/2008; 42(6):1938-43. · 5.48 Impact Factor
  • R. F. TURCO, D. F. BEZDICEK
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    ABSTRACT: The effect of plant genotype, soil temperature, and moisture on recovery of Rhizobium leguminosamm serogroups WA01 and WA02 from soil, was evaluated in the greenhouse using three plant genotypes (Pisum sativum cv. Alaska, Pisum sativum cv. Paloma and Lens culinaris cv. Rechief), three temperatures (12, 20 and 24°C) and soil from two different slope positions. The impact of moisture was followed by assessing pea nodulation after incubation of soil at different preplanting moisture levels. Isolates were also evaluated for serogroup, response to low levels of antibiotics and efficacy of symbiotic characters.Of the 33 antibiotic-strain combinations showing growth, 10 permitted 50% or more of the isolates to grow. Of the 24 clusters obtained, all except one were dominated by isolates in either serogroup. WA01 or WA02. There was no relation between either serogroup or cluster groupings and N2 fixation. Serogroup recovery was influenced by plant genotype and temperature. At root temperatures of 12 and 24°C, serogroup WA02 occurred in a significantly lower fraction of the lentil nodules as compared to the pea species. At 12°C, recovery of WA02 was higher for the Paloma than Alaska pea. Recovery of WA02 in pea nodules generally increased as the soil moisture was preconditioned to drier levels of -0.5 and -1.5 MPa water potential.
    Annals of Applied Biology 02/2008; 111(1):103 - 114. · 2.15 Impact Factor
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    ABSTRACT: The NASA Specialized Center of Research and Training in Advanced Life Support (the ALS NSCORT), a partnership of Alabama A & M, Howard, and Purdue Universities, was established by NASA in 2002 to develop technologies that will reduce the Equivalent System Mass (ESM) of regenerative processes within future space life-support systems. A key focus area of NSCORT research has been the development of efficient microbial bioreactors for treatment of human, crop, and food-process wastes while enabling resource recovery. The approach emphasizes optimizing the energy-saving advantages of hydrolytic enzymes for biomass degradation, with focus on treatment of solid wastes including crop residue, paper, food, and human metabolic wastes, treatment of greywater, cabin air, off-gases from other treatment systems, and habitat condensate. This summary includes important findings from those projects, status of technology development, and recommendations for next steps. The Plant-based Anaerobic-Aerobic Bioreactor-Linked Operation (PAABLO) system was developed to reduce crop residue while generating energy and/or food. Plant residues initially were added directly to the bioreactor, and recalcitrant residue was used as a substrate for growing plants or mushrooms. Subsequently, crop residue was first pretreated with fungi to hydrolyze polymers recalcitrant to bacteria, and leachate from the fungal beds was directed to the anaerobic digester. Exoenzymes from the fungi pre-soften fibrous plant materials, improving recovery of materials that are more easily biodegraded to methane that can be used for energy reclamation. An Autothermal Thermophilic Aerobic Digestion (ATAD) system was developed for biodegradable solid wastes. Objectives were to increase water and nutrient recovery, reduce waste volume, and inactivate pathogens. Operational parameters of the reactor were optimized for degradation and resource recovery while minimizing system requirements and footprint. The start-up behavior and recycling of effluent supernatant were evaluated to maximize degradation and minimize water input. The off-gases proceeded to a bioregenerative air-treatment reactor, and the sludge effluent was investigated for multiple downstream uses including dewatering by reed beds, use as a nutrient supplement for fish or mushroom growth, and as a growth medium and nutrient source for various crops. The Bio-Regenerative Environmental Air Treatment for Health (BREATHe I) reactor treated greywater and off-gases from the thermophilic aerobic digestion reactor which contained elevated levels of ammonia (NH3 ) and hydrogen sulfide (H2 S). BREATHe I development focused initially on removing greywater contaminants with clean air supplied to a biotrickling filter. Limited removal of organic carbon (70%) led to studies indicating that biodegradation metabolites of the surfactant disodium cocoamphodiacetate are recalcitrant. Subsequent studies showed that NH3 loaded at 150 mg/min and H2 S at 0.83 mg/min were removed completely, while removal of carbonaceous compounds from greywater remained constant. A BREATHe II reactor emphasized biofilters and biotrickling filters for removal of ersatz multicomponent gaseous waste streams representative of habitat air and atmospheric condensate. The model waste stream contained a mixture of acetone, n-butanol, methane, ethylene, and ammonia. Both biofilters and biotrickling filters packed with different media were able to achieve complete removal of easily soluble compounds such as acetone, n-butanol, and ammonia within a short startup period, whereas methane was not removed because of its extreme aqueous insolubility. Different packing media and bioreactor configurations were subsequently assessed, as well as the effect of influent ammonia concentration. Research sponsored in part by NASA grant NAG5-12686.
    01/2008;
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    ABSTRACT: Luminescence-based techniques for the detection of microbial pathogens are extensively employed in industrial setting where the continuous monitoring of bacterial contamination is of great importance. The primary advantage of all luminescence-based assays is their rapidity and sensitivity. Here we describe two different types of luminescence systems that have been adapted for commercial use, bioluminescence (BL) and chemiluminescence (CL). BL is a naturally occurring process by which living organisms convert chemical energy into light. Light-emitting pathways have been identified in bacteria, insects, and other eukaryotic organisms. Bacterial (lux) systems have been extensively studied and have been engineered for a variety of purposes. In the most common adaptation of the lux genes for the microbial detection, luciferase reporter phages are constructed for the direct and specific identification of many bacterial species including Salmonella spp., Listeria, and E. coli O157:H7. Central to the lux reaction is that bioluminescence is dependent on higher-level energy intermediates, allowing levels of light to be correlated to changes in bacterial metabolism. The firefly (LUC) luciferase is also widely used in biotechnology. Since all living things possess intracellular pools of ATP, many applications of the LUC system capitalize on the ATP-dependency of this luminescence reaction for the detection of microbial populations in situ. The LUC system is also useful in determining the efficacy of sanitizing agents, as decreases in BL are proportional to the number of active bacteria within a defined matrix. Other eukaryotic luciferases, such as those from marine copepod Gaussia princeps and Jamican click beetle, are currently been explored as alternative means for bacterial detection in extreme environmental conditions, and in situations where the simultaneous detection of multiple bacterial species is desired. CL is generally defined as the production of light by chemicals during an exothermic reaction, and CL differs from BL in that light production is not catalyzed by biological reactions. Although not as widely used in industrial applications, CL is sometimes preferred to BL-based detection systems due to the relative simplicity of the reaction and the elimination of certain steps sometimes required for the optimization of BL. CL has been used mainly for the detection of foodborne pathogens in combination with immunoassays. Using CL-linked antibodies specific for certain bacterial antigens, allows the simultaneous detection of E. coli O157:H7, Yersinia enterocolitica, Salmonella typhimurium, and Listeria monocytogenes. Luminescence-based techniques are proven effective agents in the detection of contaminating microbial populations, and with increases in the sensitivity and simplicity of such techniques, their application in numerous industrial and commercial settings will only grow.
    12/2007: pages 213-230;
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    ABSTRACT: The nascent state of the nanoproduct industry calls for important early assessment of environmental impacts before significant releases have occurred. Clearly, the impact of manufactured nanomaterials on key soil processes must be addressed so that an unbiased discussion concerning the environmental consequences of nanotechnology can take place. In this study, soils were treated with either 1 microg C60 g(-1) soil in aqueous suspension (nC60) or 1000 microg C60 g(-1) soil in granularform, a control containing equivalent tetrahydrofuran residues as generated during nC60 formation process or water and incubated for up to 180 days. Treatment effects on soil respiration, both basal and glucose-induced, were evaluated. The effects on the soil microbial community size was evaluated using total phospholipid derived phosphate. The impact on community structure was evaluated using both fatty acid profiles and following extraction of total genomic DNA, by DGGE after PCR amplification of total genomic DNA using bacterial variable V3 region targeted primers. In addition, treatment affects on soil enzymatic activities for beta-glucosidase, acid-phosphatase, dehydrogenase, and urease were followed. Our observations show that the introduction of fullerene, as either C60 or nC60, has little impact on the structure and function of the soil microbial community and microbial processes.
    Environmental Science and Technology 05/2007; 41(8):2985-91. · 5.48 Impact Factor
  • Nasser A. Assaf, Ronald F. Turco
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    ABSTRACT: It has been proposed that levels of carbon and nitrogen in soil affect the rate at which triazine herbicides degrade. The present study was designed to investigate the effects of varying the levels of initial soil carbon and nitrogen as well as the effects of a later carbon addition on the mineralization of atrazine and its metabolites in soil. Atrazine degradation in soils amended with carbon as mannitol, and with nitrogen as urea, at levels of 10, 30, 50, or 80 mg kg−1 mannitol, urea, or mannitol and urea was similar to degradation in unamended soils. Only 39% of applied atrazine was mineralized after 326 days regardless of the initial carbon or nitrogen treatment. In contrast, a second mannitol amendment of 1 g kg−1 soil at day 140 increased [14C]carbon dioxide evolution by an additional 17% as a result of enhancing the mineralization rate of the atrazine metabolites. This conclusion is supported by our finding that periodic extraction of the soil with methanol followed by quantification on HPLC showed complete dissipation of the parent atrazine in 120 days. The metabolites hydroxyatrazine (HA), deisopropylatrazine (DIA), deethylatrazine (DEA), and diaminochlorotriazine (DACT) began to appear in the methanol extract 10 days following atrazine application. The greatest concentrations of HA, DEA, DIA. and DACT in the methanol extracts were 19, 12.4, 10.1, and 6.7% of applied atrazine, respectively. These concentrations were observed at day 95 except for DEA where the concentration continued to increase until day 142. A second soil extraction with hydrochloric acid (1m) + methanol (20 + 80 by volume) recovered additional HA, deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA), and DACT. When the extraction data were combined, 31.9, 12.4, 10.1. 10.2, 12.0 and 7.8% of applied atrazine was recovered as HA, DEA, DIA, DEHA. DIHA, and DACT, respectively. Combustion of the extracted soil showed 20% of the applied atrazine remained as soil-bound residues after 326 days.
    Pesticide Science 09/2006; 41(1):41 - 47.
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    ABSTRACT: As a regional committee under the auspices of the North Central Regional Association (NCRA) of Agricultural Experiment Station Directors, the North Central Education and Research Activity Committee (NCERA)-59 has enjoyed a long and productive history. In 1946, the Federal Research and Marketing Act set aside 25% of Experiment Station Hatch funds for regional research to be undertaken by regional research committees. In 1947, the North Central Regional Association was formed, and research committees in this region quickly coalesced. NCERA-59 had its origins in the research committee NC-17, initiated in 1952 to address questions about how organic matter and management practices could improve soil structure and productivity. Members included Champ Tanner (Wisconsin), Don Kirkham (Iowa), Frank Stevenson (Illinois), Herb Reuszer (Indiana), and Jim Mortenson (Ohio). Two lines of work emerged on the committee, one related to the chemical nature of organic matter and the other to soil and crop practices relating to soil structure. In 1962, the project was divided into NC-55 "Chemical and physical characteristics of soil organic matter" and NC-56 "Soil structure and plant growth." With the generous funding they received (60% of their annual salaries), members of NC-55 could conduct extensive research projects as well as host guest speakers at their meetings, like Malcolm Oades. When the renewal for NC-55 was submitted in 1967, it was turned down because the National Program had determined that projects related to societal problems like conservation or pollution should be given preference for funding over those oriented to basic research. Thus the committee was redesignated NCR-59 and research funds for committee members were no longer provided. Members who joined in the 60s and 70s included Jack Bremner (Iowa), George Wagner (Missouri), Bob Miller (Ohio), Gordon Chesters (Wisconsin), Ed Schmidt (Minnesota), John Moraghan (North Dakota), Ed Clapp (USDA-ARS), Morris Schnitzer (Canada), J.P. Martin (California) and Ron Malcolm (USGS). As important contributions on the chemical make up and function of soil organic matter were made in the 1960s by committee members like Stevenson and Schnitzer, the focus shifted from physical characteristics of organic matter to soil biochemistry and the analysis of humic substances. Ron Malcolm, who conducted groundbreaking work on fulvic acids in water, became a founding member of the International Humic Substances Society in 1981. Throughout the 1980s, the committee served as a base of support for the IHSS. During that decade, the configuration of the committee shifted from soil biochemists and chemists such as Ron Malcolm, Frank Stevenson, Steve Boyd and Paul Bloom to microbiologists, including Robin Harris, Jean-Marc Bollag, Ron Turco, and Dianne Stott. Whether chemical or biological in slant, the committee's main focus remained on organic matter, with two of the foremost textbooks on soil organic matter of the time authored by two committee members, Frank Stevenson and Robert Tate III. In the 1990s, the committee added a focus on soil quality and sponsored a number of symposia and books on the subject, with strong leadership by John Doran (USDA-ARS). More recently, the focus has shifted again, back to an emphasis on chemical and physical fractionation of organic matter and its role in soil structure, as well as the application of organic matter research to agronomic and environmental concerns, such as nutrient cycling and use efficiency in cropping systems, carbon sequestration, and bioremediation. Committee members are again very active in a newly revitalized U.S. chapter of the International Humic Substances Society. Other contributions in recent years include: exposing thousands of interested public to new knowledge of soil organic matter function and practical management options, through a wide range of outreach materials, including a website on soil quality; writing chapters for and producing the book Soil Organic Matter in Sustainable Agriculture (Magdoff and Weil, 2004) and informing policy makers at a national and regional level. This decades long organized research effort among diverse state agricultural experiment stations and the USDA underscores the important role of organic matter in agronomic production systems and environmental quality now and in the future.
    01/2006; International Union Soil Sci..
  • M Bischoff, Linda S Lee, R F Turco
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    ABSTRACT: In a recent study on the degradation of N,N'-dibutylurea (DBU), a breakdown product of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate], the active ingredient in Benlate fungicides, degradation half-lives of 1.4-46.5 days were observed across several soils incubated at various combinations of soil moisture potential (-0.03 and -0.1 MPa) and temperature (23, 33, and 44 degrees C) for a single DBU application of 0.08 and 0.8 microg g(-1) (Lee et al. 2004). However, Benlate can be applied as often as every 7 days resulting in the repeated application of DBU likely to be present in the Benlate over a growing season. In this study, the effect of seven repeated DBU applications on mineralization rate was investigated in two soils, which encompass the range in rates previously observed. For the slower degrading soil, repeated DBU application increased mineralization from 0.029 to 0.99 day(-1) at the 0.08 microg g(-1) rate, and 0.037 to 0.89 day(-1) at the 0.8 microg g(-1) rate. For the faster degrading soil, effects on mineralization of repeated DBU applications were small to negligible. For the latter soil, the effect on mineralization of applied DBU concentrations from 0.0008 to 80 microg g(-1) was also investigated. Mineralization rates decreased from 0.43 to 0.019 day(-1) with increasing DBU concentrations. However, the amount of DBU mineralized by day 70 was similar across concentrations and averaged 83% of applied. Microbial respiration was not affected by increasing DBU concentrations. These findings support the supposition that DBU is readily degraded by soil microorganisms, thus unlikely to accumulate in agricultural soils.
    Biodegradation 07/2005; 16(3):265-73. · 2.17 Impact Factor

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