bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzymatic Oxidative Transformation of Chlorophenol Mixtures
Authors: Bollag J.‐M. , Chu Horng‐Lun , Rao M. A. , Gianfreda L.
Published: August 2012

Chlorinated phenols are major industrial and agricultural xenobiotics that pollute soil and ground water. It has been shown that laccases catalyze the oxidative coupling of phenolic compounds. Therefore, the transformation of one or a mixture of several chlorinated phenols by a laccase from the fungus Trametes villosa was studied. Generally, if more than one phenol was added, the transformation of chlorinated phenols decreased, and if the concentration of the laccase was increased, the transformation of the phenols was enhanced. There were exceptions to these observations: for instance, the transformation of 0.1 mM 4‐chlorophenol incubated with 1 mM 2,4‐dichlorophenol in buffered salt solutions was not enhanced if the concentration of the laccase was increased from 2 to 20 DMP units/mL. The reason for the reduced transformation of chlorinated phenols in the presence of additional phenols is still unknown. However, in spite of some limitations, the application of laccase to decontaminate wastewater polluted with chlorinated phenols appears feasible.
Evaluation of Nitrate Nitrogen Fluxes from a Tile‐Drained Watershed in Central Iowa
Authors: Tomer M. D. , Meek D. W. , Jaynes D. B. , Hatfield J. L.
Published: August 2012

Nitrate N fluxes from tile‐drained watersheds have been implicated in water quality studies of the Mississippi River basin, but actual NO3–N loads from small watersheds during long periods are poorly documented. We evaluated discharge and NO3–N fluxes passing the outlet of an Iowa watershed (5134 ha) and two of its tile‐drained subbasins (493 and 863 ha) from mid‐1992 through 2000. The cumulative NO3–N load from the catchment was 168 kg ha−1, and 176 and 229 kg ha−1 from the subbasins. The outlet had greater total discharge (1831 mm) and smaller flow‐weighted mean NO3–N concentration (9.2 mg L−1) than the subbasins, while the larger subbasin had greater discharge (1712 vs. 1559 mm) and mean NO3–N concentration (13.4 vs. 11.3 mg L−1) than the smaller subbasin. Concentrations exceeding 10 mg L−1 were common, but least frequent at the outlet. Nitrate N was generally not diluted by large flows, except during 1993 flooding. The outlet showed smaller NO3–N concentrations at low flows. Relationships between discharge and NO3–N flux showed log–log slopes near 1.0 for the subbasins, and 1.2 for the outlet, considering autocorrelation and measurement‐error effects. We estimated denitrification of subbasin NO3–N fluxes in a hypothetical wetland using published data. Assuming that temperature and NO3–N supply could limit denitrification, then about 20% of the NO3–N would have been denitrified by a wetland constructed to meet USDA‐approved criteria. The low efficiency results from the seasonal timing and NO3–N content of large flows. Therefore, agricultural and wetland best management practices (BMPs) are needed to achieve water quality goals in tile‐drained watersheds.
Polyvalent Cation Effects on myo‐Inositol Hexakis Dihydrogenphosphate Enzymatic Dephosphorylation in Dairy Wastewater
Authors: Dao Thanh H.
Published: August 2012

Information is needed on organic polyphosphates such as myo‐inositol 1,2,3,5/4,6‐hexakis dihydrogenphosphate or phytate (IP6) contribution to the sources and sinks of dissolved phosphorus (PO4–P) in the soil–manure–water system. Effects of Na+, Ca2+, Al3+, and Fe3+ and cation to IP6‐P mole ratios on the enzymatic dephosphorylation of IP6 were studied to determine controlling mechanisms of dephosphorylation and persistence in manure. Phytate‐ and PO4–P were analyzed by high‐performance liquid chromatography. Phytate dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 decreases by 50 ± 3.6 and 40 ± 4% at pH 4.5 and 6, respectively, as Ca2+ concentrations increase and cation to IP6‐P mole ratios reach 6:6. Polyanionic IP6 has a high affinity for Al3+ and Fe3+ and reductions in dephosphorylation average 27 and 32% at a cation to IP6‐P mole ratio of 1:6 for Al3+ and Fe3+, respectively, while reaching more than 99% at a mole ratio of 6:6. A phytase‐hydrolyzable phosphorus (PHP) fraction is native to ruminant animal manure and is proportional to total solids (TS) concentration in 1 to 100 g L−1 suspensions. Added phytase, in effect, increases water‐extractable P content of manure and the risk of environmental P dispersion. As the bioavailability and ecological effect of IP6‐P appear to be regulated not only by pH‐controlled enzyme activity but also by the associated counterions, the differential protective effects of cations influence the accuracy of manure PHP fraction estimates and increase phytate resistance to enzymatic dephosphorylation that may lead to its persistence in manure.
Determination of Redox‐Sensitive Phosphorus in Field Runoff without Sediment Preconcentration
Authors: Uusitalo Risto , Turtola Eila
Published: August 2012

Reduction‐induced phosphorus (P) release from particles transported by field runoff has been poorly studied for want of a method that could be used for large surveys. To rectify this shortcoming, we modified the bicarbonate–dithionite (BD) extraction step of a sediment P speciation scheme for analyzing redox‐sensitive P in runoff without sample preconcentration. The extraction comprised the addition of bicarbonate (pH buffer) and dithionite (reducing agent) into a runoff sample, 15 min of gentle shaking, filtration, and sample digestion. The samples were greatly reduced (Eh < −200 mV), and Fe and P were solubilized, but Al solubility was not increased. Phosphorus release from rock phosphates (calcium phosphates) was greater in the BD extraction than in water or bicarbonate solution, although no more than 0.2% of the total P was released. For runoff from a very fine Typic Cryaquept, the particulate phosphorus (PP) versus BD‐PP relationship was linear up to a PP concentration of about 1.0 mg L−1, but over the whole PP range studied (up to 2.6 mg L−1) somewhat better described by an exponential equation (BD‐PP = 0.297 × PP0.766; r2 = 0.91, n = 79). The minimum detectable value given by the method was relatively low, 0.023 mg L−1, but reproducibility varied, with the coefficient of variation for 10 samples analyzed with 5 replicates ranging from 1.8 to 28.5%. Considering the variable reproducibility of the results and the lack of suitable reference material, the method needs further refinement and testing if it is to be used for quantitative determination of redox‐sensitive P in runoff.
Nutrient Transport in a Restored Riparian Wetland
Authors: Vellidis G. , Lowrance R. , Gay P. , Hubbard R. K.
Published: August 2012

We determined the water quality effect of a restored forested riparian wetland adjacent to a manure application area and a heavily fertilized pasture in the Georgia Coastal Plain. The buffer system was managed based on USDA recommendations and averaged 38 m in width. Water quality and hydrology data were collected from 1991–1999. A nitrate plume in shallow ground water with concentrations exceeding 10 mg NO3–N L−1 moved into the restored forested riparian wetland. Along most of the plume front, concentrations were less than 4 mg NO3–N L−1 within 25 m. Two preferential flow paths associated with past hydrologic modifications to the site allowed the nitrate plume to progress further into the restored forested riparian wetland. Surface runoff total N, dissolved reactive phosphorus (DRP), and total P concentrations averaged 8.63 mg N L−1, 1.37 mg P L−1, and 1.48 mg P L−1, respectively, at the field edge and were reduced to 4.18 mg N L−1, 0.31 mg P L−1, and 0.36 mg P L−1, respectively, at the restored forested riparian wetland outlet. Water and nutrient mass balance showed that retention and removal rates for nitrogen species ranged from a high of 78% for nitrate to a low of 52% for ammonium. Retention rates for both DRP and total P were 66%. Most of the N retention and removal was accounted for by denitrification. Mean annual concentrations of total N and total P leaving the restored forested riparian wetland were 1.98 mg N L−1 and 0.24 mg P L−1, respectively.
Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater
Authors: Hunt Patrick G. , Matheny Terry A. , Szögi Ariel A.
Published: August 2012

Constructed wetland treatment of swine wastewater probably involves substantial denitrification. Our objective was to assess denitrification and denitrification enzyme activity (DEA) in such wetlands in relation to plant communities, N loading, carbon or nitrogen limitations, and water depth. Two wetland cells each 3.6 m wide and 33.5 m long were connected in series. One set of cells was planted with rushes and bulrushes, including soft rush (Juncus effusus L.), softstem bulrush [Schoenoplectus tabernaemontani (K.C. Gmel.) Palla], American bulrush [Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller], and woolgrass bulrush [Scirpus cyperinus (L.) Kunth]. Another set was planted with bur‐reeds and cattails, including American bur‐reed (Sparganium americanum Nutt.), broadleaf cattail (Typha latifolia L.), and narrowleaf cattail (Typha angustifolia L.). The sets will be referred to herein as bulrush and cattail wetlands, respectively. Denitrification and DEA were measured via the acetylene inhibition method in intact soil cores and disturbed soil samples that were taken during four years (1994–1997). Although DEA in the disturbed samples was greater than denitrification in the core samples, the measurements were highly correlated (r2 ≥ 0.82). The DEA was greater in the bulrush wetlands than the cattail wetlands, 0.516 and 0.210 mg N kg−1 soil h−1, respectively; and it increased with the cumulative applied N. The DEA mean was equivalent to 9.55 kg N ha−1 d−1 in the bulrush wetlands. We hypothesized and confirmed that DEA was generally limited by nitrate rather than carbon. Moreover, we determined that one of the most influential factors in DEA was wetland water depth. In bulrush wetlands, the slope and r2 values of the control treatment were −0.013 mg N kg−1 soil h−1 mm−1 depth and r2 = 0.89, respectively. Results of this investigation indicate that DEA can be very significant in constructed wetlands used to treat swine wastewater.
Iron Sulfide Oxidation as Influenced by Calcium Carbonate Application
Authors: Hossner L. R. , Doolittle J. J.
Published: August 2012

Two overburden materials, with different FeS2contents (1.9 and 4.1%) and low acid neutralization potential, were limed with CaCO3at rates of 0, 25, 50, 75, 100, and 125% based on the amount of CaCO3needed to provide an acid–base account deficit (A/Ba) of zero (A/Ba= neutralization potential − potential acidity − exchangeable acidity). The limed overburden materials were inoculated withThiobacillus ferrooxidansand leached weekly with deionized water. Residual FeS2and CaCO3were determined in samples over a 378‐d period. Oxidation followed zero‐order kinetics with respect to FeS2concentration at pH values greater than 4 and first‐order kinetics at pH values less than 4. Zero‐order oxidation rates ranged from 0.0l to 0.46 μmol g−1d−1in the overburden with 1.9% FeS2and from 0.01 to 0.22 μmol g−1d−1in the overburden with 4.1% FeS2Oxidation following the first‐order rate law had a first‐order rate constant of 0.03 d−1in the 1.9% FeS2overburden and 0.01 d−1in the 4.1% FeS2overburden. The calculated half‐life was 23 d for the 1.9% FeS2overburden and 69 d for the 4.1% FeS2overburden. Additions of CaCO3affected FeS2oxidation by controlling the pH of the system. Liming to greater than 50% of the acid–base account deficit did not significantly affect the zero‐order oxidation rate. Dissolution of the applied CaCO3was found to be faster than the oxidation of FeS2at pH values greater than 4. It was projected that at lime rates up to 125%, the CaCO3would dissolve and leach out of the system before all the FeS2oxidized, leaving the potential for acid minesoil formation.
Compost and Calcium Surface Treatment Effects on Subsoil Chemistry in Acidic Minespoil Columns
Authors: von Willert Frank J. , Stehouwer Richard C.
Published: August 2012

Surface incorporation of a liming agent in combination with compost or biosolids is a proven way to revegetate acidic minespoils, but little is known about the effect of the surface amendments on subsoil chemistry. We conducted a greenhouse column experiment to investigate how different surface amendments affected plant growth and subsoil chemistry in highly acidic minespoil material. Columns were filled with shale minespoil material (pH ≈ 2.5), amended with CaCO3, CaSO4·2H2O (gypsum), and two rates of compost, and seeded with birdsfoot trefoil (Lotus corniculatus L.) and ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.). We measured leachate and plant growth over a 170‐d period with extensive irrigation. Without CaCO3, plants could only grow at the high compost rate (68.8 g kg−1), even though the soil pH in those treatments was below 3.5, indicating the capability of natural organic matter to detoxify Al3+ by forming Al–organic matter complexes. Compost had no effect on the subsoil. When CaCO3 or gypsum was added to the surface, extractable Ca increased in the subsoil, but there was no relevant increase in subsoil pH. Even in the first 5 cm of subsoil material, extractable Al did not decrease very much, possibly because a jurbanite‐like solid phase controlled subsoil Al3+ activities. During the reclamation of highly acidic minespoil material one should therefore not expect significant effects of the surface treatment on the untreated subsoil. A sufficient root zone would have to be achieved by incorporating the liming agent down to the desired rooting depth.
Laboratory‐Scale Measurement of Trace Gas Fluxes from Landfarm Soils
Authors: Ausma Sandra , Edwards Grant C. , Gillespie Terry J.
Published: August 2012

Trace gas emissions from refinery and bioremediation landfarms were investigated in a mesocosm‐scale simulator facility. Five simulators were constructed and integrated with a data acquisition system and trace gas analyzers, allowing automated real‐time sampling and calculation of total hydrocarbon (THC), CO2, and water vapor fluxes. Experiments evaluating the influence of simulated cultivation and rainfall on trace gas fluxes from the soil surfaces were conducted. Results were compared with published field results. Results showed that cultivating dry or moderately wet soil resulted in brief enhancements of THC fluxes, up to a factor of 10, followed by a sharp decline. Cultivating dry soil did not enhance respiration. Cultivating wet soil did result in sustained elevated levels of respiration. Total hydrocarbon emissions were also briefly enhanced in wet soils, but to a lesser magnitude than in dry soil. Hydrocarbon fluxes from refinery landfarm soil were very low for the duration of the experiments. This lead to the conclusion that elevated THC fluxes would only be expected during waste application. An evaluation of the influence of simultaneous water vapor fluxes on other trace gas fluxes highlighted the importance in lab‐scale experiments of correcting trace gas fluxes from soils. The results from this research can be used to guide management practices at landfarms and to provide data to aid in assessing the effect of landfarms.
Virus Retention and Transport as Influenced by Different Forms of Soil Organic Matter
Authors: Zhuang Jie , Jin Yan
Published: August 2012

Organic materials are widespread in natural soil and aquatic environments. Their effect on virus transport is very important in assessing the risk for contamination of ground water by viruses. This study aimed to determine how different forms (mineral‐associated and dissolved) of natural organic matter influence the retention and transport of two bacteriophages (MS‐2 and φX174) in two porous media (a sand and a soil). We found that mineral‐associated organic matter significantly promoted the transport of one virus (MS‐2) but not the other (φX174) in a phosphate‐buffered saline solution. Similarly, MS‐2 was retained less in sand columns with increasing concentrations of dissolved humic acid, while little effect was observed for φX174 under the same conditions. The two viruses have different surface properties and thus exhibited different reactivity to the metal oxides present on sand particles and were affected differently by organic matter. Because the organic matter used in the study was negatively charged and hydrophilic, blocking of virus sorption sites and increasing of virus–medium electrostatic repulsion arising from modification of the sand and virus surface by organic matter are probably responsible for the facilitated transport. For dissolved humic acid, its competition for sorption sites with viruses was an additional mechanism involved. This study suggests that the effect of organic matter varied depending on the organic material properties and the type of viruses involved. As a general trend, the effect of organic matter was dominated by electrostatic rather than hydrophobic interactions.
Root Growth and Metal Uptake in Four Grasses Grown on Zinc‐Contaminated Soils
Authors: Palazzo Antonio J. , Cary Timothy J. , Hardy Susan E. , Lee C. Richard
Published: August 2012

Depth and area of rooting are important to long‐term survival of plants on metal‐contaminated, steep‐slope soils. We evaluated shoot and root growth and metal uptake of four cool‐season grasses grown on a high‐Zn soil in a greenhouse. A mixture of biosolids, fly ash, and burnt lime was placed either directly over a Zn‐contaminated soil or over a clean, fine‐grained topsoil and then the Zn‐contaminated soil; the control was the clean topsoil. The grasses were ‘Reliant’ hard fescue (Festuca brevipila R. Tracey), ‘Oahe’ intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia], ‘Ruebens’ Canada bluegrass (Poa compressa L.), and ‘K‐31’ tall fescue (Festuca arundinacea Schreb.). Root growth in the clean soil and biosolids corresponded to the characteristic rooting ability of each species, while rooting into the Zn‐contaminated soil was related to the species' tolerance to Zn. While wheatgrass and tall fescue had the strongest root growth in the surface layers (0–5 cm) of clean soil or biosolids, wheatgrass roots were at least two times more dense than those of the other grasses in the second layer (5–27 cm) of Zn‐contaminated soil. When grown over Zn‐contaminated soil in the second layer, hard fescue (with 422 mg/kg Zn) was the only species not to have phytotoxic levels of Zn in shoots; tall fescue had the highest Zn uptake (1553 mg/kg). Thus, the best long‐term survivors in high‐Zn soils should be wheatgrass, due to its ability to root deeply into Zn‐contaminated soils, and hard fescue, with its ability to effectively exclude toxic Zn uptake.
Herbicide Loading to Shallow Ground Water beneath Nebraska's Management Systems Evaluation Area
Authors: Spalding Roy F. , Watts Darrell G. , Snow Daniel D. , Cassada David A. , Exner Mary E. , Schepers James S.
Published: August 2012

Better management practices can counter deterioration of ground water quality. From 1991 through 1996 the influence of improved irrigation practices on ground water pesticide contamination was assessed at the Nebraska Management Systems Evaluation Area. Three 13.4‐ha corn (Zea mays L.) fields were studied: a conventional furrow‐irrigated field, a surge‐irrigated field and a center pivot–irrigated field, and a center pivot–irrigated alfalfa (Medicago sativa L.) field. The corn fields received one identical banded application of Bicep (atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4,‐diamine] + metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide]) annually; the alfalfa field was untreated. Ground water samples were collected three times annually from 16 depths of 31 multilevel samplers. Six years of sample data indicated that a greater than 50% reduction in irrigation water on the corn management fields lowered average atrazine concentrations in the upper 1.5 m of the aquifer downgradient of the corn fields from approximately 5.5 to <0.5 μg L−1 Increases in deethylatrazine (DEA; 2‐chloro‐4‐amino‐6‐isopropylamino‐s‐triazine) to atrazine molar ratios indicated that reducing water applications enhanced microbial degradation of atrazine in soil zones. The occurrence of peak herbicide loading in ground water was unpredictable but usually was associated with heavy precipitation within days of herbicide application. Focused recharge of storm runoff that ponded in the surge‐irrigated field drainage ditch, in the upgradient road ditch, and at the downgradient end of the conventionally irrigated field was a major mechanism for vertical transport. Sprinkler irrigation technology limited areas for focused recharge and promoted significantly more soil microbial degradation of atrazine than furrow irrigation techniques and, thereby, improved ground water quality.
Adsorption and Transport of Arsenic(V) in Experimental Subsurface Systems
Authors: Williams L. Elizabeth , Barnett Mark O. , Kramer Timothy A. , Melville Joel G.
Published: August 2012

The adsorption and transport of As(V) in a heterogeneous, iron oxide–containing soil was investigated in batch and column laboratory experiments. The As(V) adsorbed rapidly to the soil over the first 48 h, but continued to adsorb slowly over the next several weeks, clearly indicating the potential for rate‐limited transport. The equilibrium As(V) adsorption isotherm was markedly nonlinear, further indicating the potential for nonideal transport. A model developed for the adsorption of As(V) to hydrous ferric oxide (HFO) was able to predict the pH‐dependent adsorption of As(V) to the soil in batch experiments within 0.116 to 0.726 root mean square error (RMSE). Arsenic(V) was significantly retarded in column transport experiments. The column transport experiments were modeled using the one‐dimensional advection–dispersion equation, considering both linear and nonlinear adsorption equilibrium. Although the nonlinear local equilibrium model (NLLE, RMSE = 0.273) predicted the data better than the linear local equilibrium model (LLE, RMSE = 0.317), As(V) breakthrough occurred more rapidly than predicted by either model due to adsorption nonequilibrium. However, due to the presence of an irreversible or slowly desorbing fraction, the peak aqueous As(V) concentration (0.624 mg L−1) and the total amount of As(V) recovered (44%) was lower than predicted based on the two equilibrium models (NLLE and LLE). For the conditions used in this study [1 mg L−1 As(V), pH 4.5 and 9, 0–0.25 mM PO4, 0.53–1.6 cm min−1 pore water velocity], the effect on As(V) mobility and recovery increased in the order pH < pore water velocity < PO4
Partitioning and Availability of Uranium and Nickel in Contaminated Riparian Sediments
Authors: Sowder Andrew G. , Bertsch Paul M. , Morris Pamela J.
Published: August 2012

The effects of iron oxides and organic matter on the partitioning and chemical lability of U and Ni were examined for contaminated riparian sediments from the U.S. Department of Energy's Savannah River Site. In sequential extractions of four sediments that ranged from 12.7 to 82.2 g kg−1 in organic carbon, U was found almost exclusively in moderately labile fractions (93% in acid‐soluble + organically bound). Nickel was distributed across all operationally defined fractions, including substantial amounts in the very labile fractions (4–15% in water‐soluble + exchangeable), noncrystalline and crystalline iron oxides (38–49%), and in the nonlabile residual fraction (25–34%). Aqueous U concentrations in 1:1 sediment–water extracts were highly correlated to dissolved organic carbon (DOC) (R2 = 0.96; p < 0.0001) and ranged from 29 to 410 μg L−1 Aqueous concentrations of Ni exceeded U by two to three orders of magnitude (124–2227 μg L−1) but were not correlated with DOC (R2 = 0.04; p = 0.53). Partitioning and solubility trends suggest that Ni availability is controlled primarily by iron‐oxide phases, whereas U availability is dominated by naturally occurring organic carbon. Discrete mineral phases were also identified as nonlabile reservoirs of anthropogenic metals. In spite of comparably high sediment concentrations, Ni appears to be significantly more available than U in riparian sediments and therefore warrants greater consideration in terms of environmental consequences (i.e., transport, biological uptake, and toxicity).
Characterization of Lead Removal from Contaminated Soils by Nontoxic Soil‐Washing Agents
Authors: Neilson Julia W. , Artiola Janick F. , Maier Raina M.
Published: August 2012

Few effective strategies exist for remediating and restoring metal‐contaminated soils. We have evaluated the potential of two environmentally compatible, nondestructive, biological soil‐washing agents for remediating aged, lead‐contaminated soils. Two contaminated soils were washed with 10 mM rhamnolipid biosurfactant and 5.3% carboxymethyl‐β‐cyclodextrin (CMCD). The metal removal efficiency of these agents was compared with 10 mM diethylenetriamine pentaacetic acid (DTPA) and 10 mM KNO3 Lead removal rates by both soil‐washing agents exceeded the removal by KNO3, but were an order of magnitude less than removal by the synthetic chelator, DTPA. Analysis of soil extractions revealed that the Pb in the first soil (3780 mg kg−1) was primarily associated with the soluble, exchangeable, oxide, and residual fractions while the Pb in the second soil (23 900 mg kg−1) was found in the soluble, exchangeable, carbonate, and residual fractions. After 10 consecutive washes, rhamnolipid had removed 14.2 and 15.3% of the Pb from the first and second soils, respectively, and CMCD had removed 5 and 13.4% from the same two soils. The Pb removal rate by both agents either increased or was consistent throughout the 10 extractions, indicating a potential for continued removal with extended washing. Significant levels of Cu and Zn in both soils did not prevent Pb removal by either agent. Interestingly, the effectiveness of each agent varied as a function of Pb speciation in the soil. Rhamnolipid was more effective than CMCD in removing Pb bound to amorphous iron oxides, while both agents demonstrated similar potential for removing soluble, exchangeable, and carbonate‐bound Pb. Neither agent demonstrated potential for the complete remediation of metal‐contaminated soils.
Surface Runoff Losses of Copper and Zinc in Sandy Soils
Authors: Zhang Mingkui , He Zhenli , Calvert David V. , Stoffella Peter J. , Yang Xiaoe
Published: August 2012

Increased anthropogenic inputs of Cu and Zn in soils have caused considerable concern relative to their effect on water contamination. Copper and Zn contents in surface soil directly influence the movement of Cu and Zn. However, minimal information is available on runoff losses of Cu and Zn in agricultural soils, and soil‐extractable Cu and Zn in relation to runoff water quality. Field experiments were conducted in 2001 to study dissolved Cu and Zn losses in runoff in Florida sandy soils under commercial citrus and vegetable production and the relationship between soil‐extractable Cu and Zn forms and dissolved Cu and Zn concentrations in runoff water. Five extraction methods were compared for extracting soil available Cu and Zn. Concentrations of dissolved Cu and Zn in runoff were measured and runoff discharge was monitored. Mean dissolved Cu in field runoff water was significantly correlated with the extractable Cu obtained only by 0.01 mol L−1 CaCl2, Mehlich 1, or DTPA–TEA methods. Dissolved Zn in runoff water was only significantly correlated with extractable Zn by 0.01 mol L−1 CaCl2 The highest correlations to dissolved Cu in runoff were obtained when soil‐available Cu was extracted by 0.01 mol L−1 CaCl2 The results indicate that 0.01 mol L−1 CaCl2–extractable Cu and Zn are the best soil indexes for predicting readily released Cu and Zn in the sandy soils. Both runoff discharge and 0.01 mol L−1 CaCl2–extractable Cu and Zn levels had significant influences on Cu and Zn loads in surface runoff.
Effectiveness of Grassed Waterways in Reducing Runoff and Sediment Delivery from Agricultural Watersheds
Authors: Fiener P. , Auerswald K.
Published: August 2012

Grassed waterways (GWWs) drain surface runoff from fields without gullying along the drainageway. Secondary functions include reducing runoff volume and velocity and retaining sediments and harmful substances from adjacent fields. Grass cover (sward)–damaging sedimentation in the GWW is commonly reduced by frequent mowing, but in doing so the effectiveness of the waterway relative to the secondary functions is reduced. Our objectives were to (i) evaluate whether the maintenance of a GWW can be reduced if on‐site erosion control is effective, (ii) measure the effectiveness of such a GWW, and (iii) analyze the underlying mechanisms. A long‐term (1994–2000) landscape experiment was performed in four watersheds, where two had GWWs for which maintenance was largely neglected. An intensive soil conservation system was established on all fields. Runoff and sediment delivery were continuously measured in the two watersheds with GWWs and in their paired watersheds that were similar, but without GWWs. Runoff was reduced by 90 and 10% for the two sets of paired watersheds, respectively. The different efficiencies of the GWWs resulted from different layouts (doubled width and flat‐bottomed vs. v‐shaped drainageway). The GWWs reduced sediment delivery by 97 and 77%, respectively, but the sward was not damaged by sedimentation. Grain sizes > 50 μm were settled due to gravity in both GWWs. Smaller grain sizes were primarily settled due to infiltration, which increased with a more effective runoff reduction. In general, the results indicated a high potential of GWWs for reducing runoff volume and velocity, sediments, and agrochemicals coming from agricultural watersheds.
Soil Sorption of Acidic Pesticides
Authors: Spadotto Claudio A. , Hornsby Arthur G.
Published: August 2012

A model of acidic pesticide sorption in soils was developed from theoretical modeling and experimental data, which initially considered a combination of a strongly acidic pesticide and a variable‐charge soil with high clay content. Contribution of 2,4‐D [(2,4‐dichlorophenoxy) acetic acid] anionic‐form sorption was small when compared with molecular sorption. Dissociation of 2,4‐D was not sufficient to explain the variation in Kd as a function of pH. Accessibility of soil organic functional groups able to interact with the pesticide (conformational changes) as a function of organic matter dissociation was proposed to explain the observed differences in sorption. Experimental 2,4‐D sorption data and Koc values from literature for flumetsulam [N‐(2,6‐difluorophenyl)‐5‐methyl [1,2,4] triazolo [1,5‐a] pyrimidine‐2‐sulfonamide] and sulfentrazone [N‐[2,4‐dichloro‐5‐[4‐(difluromethyl)‐4,5‐dihydro‐3‐methyl‐5‐oxo‐1H‐1,2,4‐triazol‐1‐y1] phenyl] methanesulfonamide] in several soils fit the model.
Stochastical Analysis of Surfactant‐Enhanced Remediation of Denser‐than‐Water Nonaqueous Phase Liquid (DNAPL)–Contaminated Soils
Authors: Zhang Renduo , Wood A. Lynn , Enfield Carl G. , Jeong Seung‐Woo
Published: August 2012

Stochastical analysis was performed to assess the effect of soil spatial variability and heterogeneity on the recovery of denser‐than‐water nonaqueous phase liquids (DNAPL) during the process of surfactant‐enhanced remediation. UTCHEM, a three‐dimensional, multicomponent, multiphase, compositional model, was used to simulate water flow and chemical transport processes in heterogeneous soils. Soil spatial variability and heterogeneity were accounted for by considering the soil permeability as a spatial random variable and a geostatistical method was used to generate random distributions of the permeability. The randomly generated permeability fields were incorporated into UTCHEM to simulate DNAPL transport in heterogeneous media and stochastical analysis was conducted based on the simulated results. From the analysis, an exponential relationship between average DNAPL recovery and soil heterogeneity (defined as the standard deviation of log of permeability) was established with a coefficient of determination (r2) of 0.991, which indicated that DNAPL recovery decreased exponentially with increasing soil heterogeneity. Temporal and spatial distributions of relative saturations in the water phase, DNAPL, and microemulsion in heterogeneous soils were compared with those in homogeneous soils and related to soil heterogeneity. Cleanup time and uncertainty to determine DNAPL distributions in heterogeneous soils were also quantified. The study would provide useful information to design strategies for the characterization and remediation of nonaqueous phase liquid–contaminated soils with spatial variability and heterogeneity.
Simplified Method for Detecting Tritium Contamination in Plants and Soil
Authors: Andraski B. J. , Sandstrom M. W. , Michel R. L. , Radyk J. C. , Stonestrom D. A. , Johnson M. J. , Mayers C. J.
Published: August 2012

Cost‐effective methods are needed to identify the presence and distribution of tritium near radioactive waste disposal and other contaminated sites. The objectives of this study were to (i) develop a simplified sample preparation method for determining tritium contamination in plants and (ii) determine if plant data could be used as an indicator of soil contamination. The method entailed collection and solar distillation of plant water from foliage, followed by filtration and adsorption of scintillation‐interfering constituents on a graphite‐based solid phase extraction (SPE) column. The method was evaluated using samples of creosote bush [Larrea tridentata (Sessé & Moc. ex DC.) Coville], an evergreen shrub, near a radioactive disposal area in the Mojave Desert. Laboratory tests showed that a 2‐g SPE column was necessary and sufficient for accurate determination of known tritium concentrations in plant water. Comparisons of tritium concentrations in plant water determined with the solar distillation–SPE method and the standard (and more laborious) toluene‐extraction method showed no significant difference between methods. Tritium concentrations in plant water and in water vapor of root‐zone soil also showed no significant difference between methods. Thus, the solar distillation–SPE method provides a simple and cost‐effective way to identify plant and soil contamination. The method is of sufficient accuracy to facilitate collection of plume‐scale data and optimize placement of more sophisticated (and costly) monitoring equipment at contaminated sites. Although work to date has focused on one desert plant, the approach may be transferable to other species and environments after site‐specific experiments.
Reactions of Mid‐Southern U.S. Soybean Cultivars to Bean Pod Mottle Virus and Tobacco Ringspot Virus
Authors: Shakiba Ehsan , Chen Pengyin , Gergerich Rose , Li Shuxian , Dombek Donald , Shi Ainong , Brye Kristofor
Published: August 2012

Bean pod mottle virus (BPMV) and Tobacco ringspot virus (TRSV) are two important viral pathogens causing reduction of seed yield and quality in soybean [Glycine max (L.) Merr.]. Various BPMV and TRSV isolates have been observed, but no host resistance has been reported. The objective of this study was to screen a set of modern soybean cultivars for resistance or tolerance to BPMV and TRSV. A total of 303 cultivars currently grown in the mid‐southern United States were screened in the greenhouse for their reactions to BPMV and TRSV. Each cultivar was inoculated with a mild and a virulent isolate of each virus. None of the cultivars tested was resistant to BPMV, but a range of tolerance to this virus was observed among the cultivars. An enzyme‐linked immunosorbent assay (ELISA) confirmed the presence of BPMV in the high and low tolerance cultivars. Tolerance to BPMV is associated with less of a reduction in plant height and biomass on infected plants. Cultivars were classified into four groups, high, moderate, low, and very low tolerance, on the basis of their having exhibited ≤20, 21 to 40, 41 to 60, or >60% of a reduction in plant height and ≤25, 26 to 50, 51 to 75, and >75% plant biomass reduction, respectively. None of the cultivars was resistant to TRSV, and all showed bud blight symptoms by 10 d after inoculation. However, 55 cultivars recovered 5 wk after inoculation, with more than 80% of the plants growing out of the bud blight symptoms and forming new leaves. The recovered plants, although systemically infected, clearly showed tolerance to TRSV at a later stage. These results may be helpful to soybean producers for selecting tolerant cultivars to grow in areas where BPMV and/or TRSV may cause problems in production.
Reactions of Commercial Soybean Cultivars from the Mid South to Soybean Mosaic Virus
Authors: Shakiba Ehsan , Chen Pengyin , Gergerich Rose , Li Shuxian , Dombek Donald , Brye Kris , Shi Ainong
Published: August 2012

Soybean mosaic virus (SMV) is one of the most important viral diseases, causing drastic reductions in seed yield and quality. Seven SMV strains, G1 through G7, have been identified, and three resistance loci, Rsv1, Rsv3, and Rsv4, have been reported in the United States. The objectives of this study were to evaluate the reactions of a set of modern soybean [Glycine max (L.) Merr.] cultivars to SMV and to deduce which previously reported genes were involved in resistance. A total of 303 cultivars currently grown in the mid‐southern United States were screened in the greenhouse with six SMV strains (G1, G2, G3, G5, G6, and G7). The results demonstrated that 189 cultivars were susceptible to all six SMV strains. Three cultivars were resistant to G1, G2, G3, G5, and G6 but developed stem‐tip necrosis after infection with G7, so these were presumed to carry the Rsv1 allele. Sixty‐six cultivars were resistant to G1 through G3 but susceptible to G5 through G7 and presumably carry Rsv1‐y. One cultivar was resistant to G1 through G3 but necrotic to G5 through G7 and may carry Rsv1‐k. Two cultivars probably carry Rsv1‐t because they were resistant to G1, G2, G5, and G6 but necrotic to G3 and G7, and another two cultivars may carry Rsv1‐n because they were necrotic to G1, G2, G5, and G6 but susceptible to G2 and G7. Four cultivars were susceptible to G1 through G3 but resistant to G5 through G7, and therefore they may carry Rsv3. Two cultivars were resistant to all six SMV strains, and therefore they may carry Rsv4, Rsv1‐h, or two‐gene combinations. There were 34 cultivars exhibiting unique SMV reaction patterns that may carry novel genes or alleles, including 23 cultivars that may carry novel alleles at the Rsv1 locus and 11 that may carry novel alleles at the Rsv3 locus. The results from this study can be used by breeders to choose resistant cultivars as parents in soybean breeding programs and by producers to select resistant cultivars in areas where SMV is a disease of concern for soybean production.
A Comparison of Tests for QTL Mapping with Introgression Libraries Containing Overlapping and Nonoverlapping Donor Segments
Authors: Mahone Gregory S. , Borchardt Dietrich , Presterl Thomas , Frisch Matthias
Published: August 2012

Near‐isogenic line (NIL) libraries can be used to detect beneficial trait variation in germplasm that is unadapted or has poor agronomic performance. The objectives of our study were to compare the t test, Dunnett test, and linear model test with regard to the power and false positive rate of quantitative trait loci (QTL) detection in NIL libraries of different design. We employed computer simulations with maize genome models to investigate nonoverlapping NIL libraries, overlapping NIL libraries, and stepped aligned inbred recombinant strains (STAIRS) libraries for traits with oligogenic inheritance. Quantitative trait loci detection power of the linear model and Dunnett tests were similar for nonoverlapping and STAIRS libraries; for overlapping NIL libraries the Dunnett test was slightly superior. False positives were greatest for the t test and lowest for the linear model test. False positive sums with the Dunnett test were generally higher than for the linear model test if the heritability was 0.9 or lower. We conclude that the linear model test is superior to the Dunnett test for nonoverlapping NIL libraries and for overlapping NIL libraries with heritabilities below 0.9, as usually occur. Analysis of a rapeseed (Brassica napus L.) library revealed two other major advantages of the linear model test. First, detection of positive and negative QTL effects present in the same line is possible. Second, for NILs with multiple donor segments, observed phenotypic differences can be assigned to individual chromosome segments.
Geographical Patterns of Sesame Accessions Grown Under Mediterranean Environmental Conditions, and Establishment of a Core Collection
Authors: Yol Engin , Uzun Bülent
Published: August 2012

The exploitation of exotic germplasm resources in breeding programs is necessary to enhance the diversity of cultivars. The diversity and relationships in a worldwide collection of sesame (Sesamum indicum L.) germplasm were determined in this study. A total of 345 accessions were assessed in relation to 12 qualitative and nine quantitative traits during two growing seasons. The accessions were grouped on the basis of their geographical patterns and morphological and agronomic characteristics. Specific accessions having high seed yield and number of branches and capsules, early maturity, yellow and brown seed color, purple stem and capsule color, hairiness, nonshattering capsules, and determinate growth habit were identified. Multivariate analysis revealed that genetic variation in the entire collection was mainly evident in days to maturity, stem length to the first capsule, plant height, and number of branches. Cluster analysis showed that the germplasm collection was representative of the geographical distribution of sesame. A core collection was developed, providing an indispensable resource for DNA and fatty acid composition studies based on analyses of fewer accessions than the entire collection. Comparison of the core and entire collections based on the qualitative and quantitative descriptors indicated that the core collection was optimal and appropriately represented the entire collection.
Inheritance of Yield‐Related Traits in Climbing Beans (Phaseolus vulgaris L.)
Authors: Checa Oscar E. , Blair Matthew W.
Published: August 2012

Climbing beans (Phaseolus vulgaris L.) are a traditional crop that has high productivity compared to bush beans. Very little research has been done on climbing beans in comparison to bush beans, and the genetics of its high yield potential are not well understood. The objectives of this work were (i) to evaluate genetic correlations between growth cycle and yield, (ii) to determine the quantitative trait loci (QTL) controlling these phenological and productivity traits, (iii) to compare QTL for seed yield and yield components with QTL for climbing ability in a recombinant inbred line population derived from crossing the climbing bean G2333 by the bush bean G19839, and (iv) to determine heritability for each variable. The experiment was grown on trellises and repeated across four environments, two of which were contrasting for phosphorus fertilization. The results show that inheritance of yield components is simpler and of higher heritability than seed yield itself. Some yield‐related QTL were overlapping across environments while others were independent. A total of four QTL were found for yield, while a total of 12 QTL were found for yield component traits. The higher heritability of seed weight allowed the detection of nine QTL for this trait. Meanwhile, a total of six QTL were found for phenological traits, with the majority being for time to maturity rather than time to flowering since the former trait had higher heritability. We discuss the implications of these results for breeding of climbing beans.
Pollen‐Mediated Gene Flow in Triticale
Authors: Kavanagh Vanessa B. , Hills Melissa J. , Eudes Francois , Topinka Keith , Yang Rong‐Cai , Hall Linda M.
Published: August 2012

Triticale (×Triticosecale Wittm. ex A. Camus) is primarily an animal feed crop with promising qualities for a bioindustrial crop. Development of genetically modified (GM) triticale is in progress and before release of GM cultivars, the potential for pollen‐mediated gene flow (PMGF) needs to be assessed to determine if it can coexist with conventional cultivars without causing market harm. Small and large plot experiments were conducted to quantify PMGF using an experimental blue aleurone triticale line as pollen donor and ‘AC Alta’ as pollen receptor. Small plot experiments were conducted at two locations in both 2007 and 2009 in Alberta, Canada. There were no site or year differences. Average PMGF from 0.2 to 1.4 m was 0.76%. Large plot experiments were conducted at two locations in both 2008 and 2009 using a concentric donor (20 by 20 m) and receptor (120 by 120 m) design. Over 17 million seeds were screened. There were no significant differences between sites or years. Pollen‐mediated gene flow best fit an exponential decay model in which the highest average PMGF (3.4%) occurred adjacent to the donor crop and rapidly declined to 0.09% by 50 m. Directional differences were detected with highest PMGF corresponding to prevailing wind directions at flowering. The estimated adventitious presence of GM triticale after harvest blending within a 50‐m conventional field was 0.22%. Pollen‐mediated gene flow in triticale is similar to spring wheat (Triticum aestivum L.) and should not prevent the coexistence of GM and conventional triticale using the 0.9% threshold established by the European Union.
Using Variability within Digital Images to Improve Tall Fescue Color Characterization
Authors: Ghali Ihab E. , Miller Grady L. , Grabow Garry L. , Huffman Rodney L.
Published: August 2012

Digital image analysis (DIA) provides an accurate, nondestructive, and objective assessment of turf color. Previous research developed an index known as the dark green color index (DGCI) via DIA as an indicator of turf color. The objective of this study was to use DGCI variability to better predict a visual rating (VR) index used to evaluate tall fescue (Festuca arundinacea Schreb.) color under different irrigation treatments. To develop DGCI statistics, two freeware software packages (Image J and R) were used to extract and process information from digital images. The model to predict VR from DIA was developed and calibrated using candidate DGCI statistical moments from 120 images in a calibration data set using a multiple linear regression procedure. Fitness of calibration and validation models were verified using the adjusted coefficient of determination, root mean square error, and the Mallow's Cp statistic. The two‐variable model produced more precise estimates (adjusted R2 = 0.926 and 0.899) than the model that only used one term in predicting the VR values (adjusted R2 = 0.879 and 0.843) for calibration and validation sets, respectively. These data suggest incorporating a measure of color uniformity improves the use of DGCI in predicting VR values compared to using only the mean of DGCI values to predict VR values. Model refinements may be needed for other turf species, but current work suggests using additional statistical moments such as SD improves VR estimate precision and accuracy.