bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulating Nitrate Drainage Losses from a Walnut Creek Watershed Field
Authors: Bakhsh A. , Hatfield J. L. , Kanwar R. S. , Ma L. , Ahuja L. R. 
Published: July 2013

ABSTRACTThis study was designed to evaluate the improved version of the Root Zone Water Quality Model (RZWQM) using 6 yr (1992–1997) of field‐measured data from a field within Walnut Creek watershed located in central Iowa. Measured data included subsurface drainage flows, NO3–N concentrations and loads in subsurface drainage water, and corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The dominant soil within this field was Webster (fine‐loamy, mixed, superactive, mesic Typic Endoaquolls) and cropping system was corn–soybean rotation. The model was calibrated with 1992 data and was validated with 1993 to 1997 data. Simulations of subsurface drainage flow closely matched observed data showing model efficiency of 99% (EF = 0.99), and difference (D) of 1% between measured and predicted data. The model simulated NO3–N losses with subsurface drainage water reasonably well with EF = 0.8 and D = 13%. The simulated corn grain yields were in close agreement with measured data with D < 10%. Nitrogen‐scenario simulations demonstrated that corn yield response function reached a plateau when N‐application rate exceeded 90 kg ha−1 Fraction of applied N lost with subsurface drainage water varied from 7 to 16% when N‐application rate varied from 30 to 180 kg ha−1 after accounting for the nitrate loss with no‐fertilizer application. These results indicate that the RZWQM has the potential to simulate the impact of N application rates on corn yields and NO3–N losses with subsurface drainage flows for agricultural fields in central Iowa.
Assessment of a δ15N Isotopic Method to Indicate Anthropogenic Eutrophication in Aquatic Ecosystems
Authors: Cole Marci L. , Valiela Ivan , Kroeger Kevin D. , Tomasky Gabrielle L. , Cebrian Just , Wigand Cathleen , McKinney Richard A. , Grady Sara P. , Carvalho da Silva Maria Helena 
Published: July 2013

ABSTRACTIncreased anthropogenic delivery of nutrients to water bodies, both freshwater and estuarine, has caused detrimental changes in habitat, food web structure, and nutrient cycling. Nitrogen‐stable isotopes may be suitable indicators of such increased nutrient delivery. In this study, we looked at the differences in response of macrophyte δ15N values to anthropogenic N across different taxonomic groups and geographic regions to test a stable isotopic method for detecting anthropogenic impacts. Macrophyte δ15N values increased with wastewater input and water‐column dissolved inorganic nitrogen (DIN) concentration. When macrophytes were divided into macroalgae and plants, they responded similarly to increases in wastewater N, although macroalgae was a more reliable indicator of both wastewater inputs and water‐column DIN concentrations. Smooth cordgrass (Spartina alterniflora Loisel.) δ15N increased uniformly with wastewater inputs across a geographic range. We used the relationship derived between S. alterniflora and relative wastewater load to predict wastewater loads in locations lacking quantitative land use data. The predictions matched well with known qualitative information, proving the use of a stable isotopic method for predicting wastewater input.
Dynamics of Potassium Leaching on a Hillslope Grassland Soil
Authors: Alfaro Marta A. , Gregory Peter J. , Jarvis Stephen C. 
Published: July 2013

ABSTRACTThere have been only a few studies of potassium (K) losses from grassland systems, and little is known about their dynamics, especially in relation to nitrogen (N) management. A study was performed during the autumn and winter of 1999 and 2000 to understand the effects of N and drainage on the dynamics of K leaching on a hillslope grassland soil in southwestern England. Two N application rates were studied (0 and 280 kg N ha−1 yr−1), both with and without tile drainage. Treatments receiving N also received farmyard manure (FM). Higher total K losses and K concentrations in the leachates were found in the N + FM treatments (150 and 185% higher than in 0 N treatments), which were related to K additions in the FM. Drainage reduced K losses by 35% because of an increase in dry matter production and a reduction in overland and preferential flow. The pattern of change in K concentration in the leachates was associated with preferential flow at the beginning of the drainage season and with matrix flow later in winter, and was best described by a double exponential curve. Rainfall intensity and the autumn application of FM were the main determinants of K losses by leaching. The study provided new insights into the relationships between soil hydrology, rainfall, and K leaching and its implications for grassland systems.
Mathematical Modeling of Phosphorus Losses from Land Application of Hog and Cattle Manure
Authors: Grant R. F. , Amrani M. , Heaney D. J. , Wright R. , Zhang M. 
Published: July 2013

ABSTRACTMathematical models may provide a means to estimate phosphorus (P) losses from land application of manure. Phosphorus losses typically occur during brief episodes of runoff and erosion. Models must be able to simulate P losses during these episodes by representing the basic chemical, physical, and biological processes by which these losses occur. The mathematical model ecosys combines dynamic distributed flow of solutes and nonsolutes through runoff and erosion with convective–dispersive transport of solutes, and both biologically and thermodynamically driven transformations between solutes and nonsolutes. This model was tested against P lost in runoff, erosion, and leachate measured during 90 min of controlled rainfall at 65 mm h−1 on soils from six sites at which different rates of manure had been applied over the previous 3 to 6 yr. Transport and transformation kinetics in the model enabled it to simulate changes of dissolved inorganic phosphorus (DIP) in runoff from >1.0 to <0.05 mg L−1 and changes of total phosphorus (TP) in sediment from 15 to 3 mg L−1 measured during controlled rainfall on soils with diverse P contents. Results from 60‐yr model runs using these kinetics with different application rates of cattle manure indicated that (i) a positive interaction exists between annual rainfall and application rate on P losses and (ii) rates greater than 30 Mg ha−1 yr−1 would cause TP concentrations in water leaving the site to rise above acceptable limits. The interaction between rainfall and rate suggests that P losses from manure application at any site should be assessed under the upper range of likely rainfall intensities.
Infiltration of Acetochlor and Two of Its Metabolites in Two Contrasting Soils
Authors: Baran Nicole , Mouvet Christophe , Dagnac Thierry , Jeannot Roger 
Published: July 2013

ABSTRACTTo obtain data concerning the risk of leaching of acetochlor (2‐chloro‐2′‐methyl‐6′‐ethyl‐N‐ethoxymethyl‐acetanilide) and its major metabolites, ethanesulfonic acid (ESA) and oxanilic acid (OA), to ground water, we studied the fate of these products in two different soil types (luvisol and calcisol) under the same weather conditions. The metabolites were detected in the soils as early as 7 d after application, indicating a rapid onset of acetochlor degradation. Ethanesulfonic acid was predominant over OA in the calcisol, regardless of time or depth, whereas the ESA to OA ratio varied with both time and depth in the luvisol. The maximum depths at which they were detected were 60 to 70 and 10 to 20 cm for ESA and OA, respectively, in the luvisol, and 60 to 70 cm (maximum depth sampled) and 30 to 40 cm for ESA and OA, respectively, in the calcisol. Acetochlor was still detected in the surface layer of the two soils 344 d after its application, although the molecule was partially leached. The maximum depths at which acetochlor was detected (60–70 cm in the luvisol and 50–60 cm [maximum depth sampled] in the calcisol) were recorded during the first sampling 7 d after application. Acetochlor was not detected on later dates below the 30‐ to 40‐cm layer in the calcisol or the 5‐ to 10‐cm layer in the luvisol. The greater preferential flow in the luvisol, which would have favored leaching, might partially explain why the mass balances done 7 d after application were lower in the luvisol (approximately 26%) than in the calcisol (approximately 45%).
Formation of π–π Complexes between Phenanthrene and Model π‐Acceptor Humic Subunits
Authors: Wijnja Hotze , Pignatello Joseph J. , Malekani Kalumbu 
Published: July 2013

ABSTRACTπ–π Interactions may play a role in association of aromatic compounds with natural organic substances. Complexation in aqueous solvents was studied between the π donor, phenanthrene (PHEN), and model π‐acceptor species (quinones and N‐heteroaromatic cations) that represent certain functional units of humic substances. Charge‐transfer bands in the UV and ring‐current shifts in the proton nuclear magnetic resonance (NMR) spectrum confirmed the face‐to‐face, π–π donor–acceptor nature of the bond. Complexation constants were obtained by the solubility enhancement method; solubility enhancements up to 2500 were found. Ruled out as predominant causes of solubility enhancement were monomer desolvation (i.e., “hydrophobic” effects), partitioning into micelles, π–cation interactions, and π–hydrogen bonding. Acceptor self‐stacking and formation of higher‐stoichiometry acceptor–donor complexes had to be considered in evaluating donor–acceptor equilibria in some cases. The affinity of acceptor for PHEN followed the order of increasing π‐acceptor strength and varied strongly with the degree of ring overlap with PHEN. Complexation between PHEN and the free solution faces of an acceptor was less favorable than intercalation of PHEN between two acceptor units in a stack. A positive hydrophobic effect on complexation was evident in water mixtures with acetone or methanol and found to correlate with the number of faces of PHEN requiring desolvation to form the complex. When hydrophobic effects are subtracted out, the π–π complex actually becomes favored as the solvent water content and polarity decline. The results suggest that phenanthrene, and by implication other donor aromatic compounds, are capable of forming π–π interactions with appropriate humic fragments.
Organic Ligand Effects on Enzymatic Dephosphorylation of myo‐Inositol Hexakis Dihydrogenphosphate in Dairy Wastewater
Authors: Dao Thanh H. 
Published: July 2013

ABSTRACTAnimal manure contains partially digested feed fiber and grains where phosphorus (P) is bound in organic compounds that include myo‐inositol 1,2,3,5/4,6‐hexakis dihydrogenphosphate or phytic acid (IP6). Information is needed on the effects of other (non‐IP6) organic ligands (LIGND) on the enzymatic dephosphorylation of IP6, which is a potential source of dissolved orthophosphate P (PO4–P) in the soil–manure–water system. The effects of 1,2‐cyclohexane diamino‐tetraacetate (CDTA), diethylenetriamine‐N,N,N′,N″,N″‐pentaacetate (DTPA), ethylenediamine‐N,N,N′,N′‐tetraacetate (EDTA), oxalate (OXA), and phthalate (PHTH) and LIGND to IP6 molar ratio and charge concentration ratio on IP6 dephosphorylation were studied to determine controlling mechanisms of IP6 persistence in manure. Solution PO4–P concentrations were analyzed by ion chromatography as the phosphomolybdate–ascorbic acid method partly includes IP6‐P. Uncomplexed IP6 dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 at pH 4.5 and 6 is unaffected by the presence of LIGNDs. As the concentrations of Ca2+, Al3+, or Fe3+ increase, dephosphorylation is reduced. Their inhibitory effect lessens in the presence of LIGNDs, in the following order: CDTA = EDTA > DTPA ≫ OXA ≥ PHTH. Whether CDTA or EDTA is the most effective LIGND depends upon the acidity of the suspension and LIGND charge concentration, reducing the inhibitory effect of polyvalent counterions to the point of promoting the hydrolysis of a manure phytase‐hydrolyzable phosphorus (PHP) fraction that is otherwise unavailable. Therefore, ligand‐induced changes increase the mobilization and dephosphorylation of complexed organic P, above and beyond the simple dissolution of inorganic phosphates. An analytical method for potentially bioavailable PHP in animal manure should include a LIGND as extracting reagent. Also, potential LIGNDs in an organic carbon–rich dairy wastewater may increase the release of PHP and environmental dispersion of PO4–P.
Dissolved Phosphorus Retention and Release from a Coastal Plain In‐Stream Wetland
Authors: Novak J. M. , Stone K. C. , Szogi A. A. , Watts D. W. , Johnson M. H. 
Published: July 2013

ABSTRACTDissolved phosphorus (DP) can be released from wetlands as a result of flooding or shifts in water column concentrations. Our objectives were to determine the long‐term (1460 d) DP retention and release characteristics of an in‐stream wetland, and to evaluate how these characteristics respond to flooding, draining, and changes in DP concentrations. The studied in‐stream wetland drains an agriculturally intensive subwatershed in the North Carolina Coastal Plain region. The wetland's DP retention and release characteristics were evaluated by measuring inflow and outflow DP concentrations, DP mass balance, and DP movement across the sediment–water column interface. Phosphorus sorption isotherms were measured to determine the sediment's equilibria P concentration (EPCo), and passive samplers were used to measure sediment pore water DP concentrations. Initially, the in‐stream wetland was undersized (0.31 ha) and released 1.5 kg of DP. Increasing the in‐stream wetland area to 0.67 ha by flooding resulted in more DP retention (28 kg) and low outflow DP concentrations. Draining the in‐stream wetland from 0.67 to 0.33 ha caused the release of stored DP (12.1 kg). Shifts both in sediment pore water DP concentrations and sediment EPCo values corroborate the release of stored DP. Reflooding the wetland from 0.33 to 0.85 ha caused additional release of stored DP into the outflowing stream (10.9 kg). We conclude that for a time period, this in‐stream wetland did provide DP retention. During other time periods, DP was released due to changes in wetland area, rainfall, and DP concentrations.
Alum Treatment of Poultry Litter
Authors: Gilmour J. T. , Koehler M. A. , Cabrera M. L. , Szajdak L. , Moore P. A. 
Published: July 2013

ABSTRACTWhile the poultry industry is a major economic benefit to several areas in the USA, land application of poultry litter to recycle nutrients can lead to impaired surface and ground water quality. Amending poultry litter with alum [Al3(SO4)2·14H2O] has received considerable attention as a method of economically reducing ammonia volatilization in the poultry house and soluble phosphorus in runoff waters. The objective of this study was to characterize the effect of alum on broiler litter decomposition and N dynamics under laboratory conditions. Litter that had been amended with alum in the poultry house after each of the first four of five flock cycles (Experiment I) and litter that had been amended with alum after removal from a poultry house after the third flock cycle (Experiment II) were compared with unamended litter in separate studies. The litters in Experiment I were surface‐applied to simulate application to grasslands, while the litters in Experiment II were incorporated to simulate application to conventionally tilled crops. The only statistically significant differences in decomposition due to alum occurred early in Experiment II and the differences were small. The only statistically significant differences in net N mineralization, soil inorganic N, and soil NH+4–N in either experiment was found in Experiment I after 70 d of incubation where soil inorganic N was significantly greater for the alum treatment. Thus, alum had little effect on decomposition or N dynamics. Results of many of the studies on litter not amended with alum should be applicable to litters amended with alum to reduce P availability.
A Simple High Performance Liquid Chromatography Method for Analyzing Paraquat in Soil Solution Samples
Authors: Ouyang Ying , Mansell Robert S. , Nkedi‐Kizza Peter 
Published: July 2013

ABSTRACTA high performance liquid chromatography (HPLC) method with UV detection was developed to analyze paraquat (1,1′‐dimethyl‐4,4′‐dipyridinium dichloride) herbicide content in soil solution samples. The analytical method was compared with the liquid scintillation counting (LSC) method using 14C‐paraquat. Agreement obtained between the two methods was reasonable. However, the detection limit for paraquat analysis was 0.5 mg L−1 by the HPLC method and 0.05 mg L−1 by the LSC method. The LSC method was, therefore, 10 times more precise than the HPLC method for solution concentrations less than 1 mg L−1 In spite of the high detection limit, the 12C (nonradioactive) HPLC method provides an inexpensive and environmentally safe means for determining paraquat concentration in soil solution compared with the 14C‐LSC method.
Overexpression of ATP Sulfurylase in Indian Mustard
Authors: Wangeline Ami L. , Burkhead Jason L. , Hale Kerry L. , Lindblom Stormy D. , Terry Norman , Pilon Marinus , Pilon‐Smits Elizabeth A. H. 
Published: July 2013

ABSTRACTIndian mustard [Brassica juncea (L.) Czern.] transgenics overexpressing ATP sulfurylase (APS plants) were shown previously to have higher levels of total thiols, S, and Se. The present study explores the effect of ATP sulfurylase overexpression on tolerance and accumulation of other metals, both oxyanions and cations, reasoning that some anions may react directly with ATP sulfurylase, while other ions may be bound by its thiol end products. The APS transgenics were compared with wild‐type plants with respect to tolerance and accumulation of As, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, V, W, and Zn, supplied individually in agar medium (seedlings) or in hydroponics (mature plants). At the seedling stage, APS transgenics were more tolerant than wild type to As(III), As(V), Cd, Cu, Hg, and Zn, but less tolerant to Mo and V. The APS seedlings had up to 2.5‐fold higher shoot concentrations of As(III), As(V), Hg, Mo, Pb, and V, and somewhat lower Cr levels. Mature APS plants contained up to 2.5‐fold higher shoot concentrations of Cd, Cr, Cu, Mo, V, and W than wild type. They also contained 1.5‐ to 2‐fold higher levels of the essential elements Fe, Mo, and S in most of the treatments. Mature APS plants showed no differences in metal tolerance compared with the wild type. Overexpression of ATP sulfurylase may be a promising approach to create plants with enhanced phytoextraction capacity for mixtures of metals.
Source‐Separated Municipal Solid Waste Compost Application to Swiss Chard and Basil
Authors: Zheljazkov Valtcho D. , Warman Philip R. 
Published: July 2013

ABSTRACTA growth room experiment was conducted to evaluate the bioavailability of Cu, Mn, Zn, Ca, Fe, K, Mg, P, S, As, B, Cd, Co, Cr, Hg, Mo, Na, Ni, Pb, and Se from a sandy loam soil amended with source‐separated municipal solid waste (SSMSW) compost. Basil (Ocimum basilicum L.) and Swiss chard (Beta vulgaris L.) were amended with 0, 20, 40, and 60% SSMSW compost to soil (by volume) mixture. Soils and compost were sequentially extracted to fractionate Cu, Pb, and Zn into exchangeable (EXCH), iron‐ and manganese‐oxide‐bound (FeMnOX), organic‐matter (OM), and structurally bound (SB) forms. Overall, in both species, the proportion of Cu, Pb, and Zn levels in different fractions followed the sequence: SB > OM ≫ FeMnOX > EXCH for Cu; FeMnOX = SB > OM > EXCH for Pb; and FeMnOX > SB = EXCH ≫ OM for Zn. Application of SSMSW compost increased soil pH and electrical conductivity (EC), and increased the concentration of Cu, Pb, and Zn in all fractions, but not EXCH Pb. Basil yields were greatest in the 20% treatment, but Swiss chard yields were greater in all compost‐amended soils relative to the unamended soil. Basil plants in 20 or 40% compost treatments reached flowering earlier than plants from other treatments. Additions of SSMSW compost to soil altered basil essential oil, but basil oil was free of metals. The results from this study suggest that mature SSMSW compost with concentrations of Cu, Pb, Mo, and Zn of 311, 223, 17, and 767 mg/kg, respectively, could be used as a soil conditioner without phytotoxic effects on agricultural crops and without increasing the normal range of Cu, Pb, and Zn in crop tissue. However, the long‐term effect of the accumulation of heavy metals in soils needs to be carefully considered.
Characterization of Turf Practices in Five North Carolina Communities
Authors: Osmond Deanna L. , Hardy David H. 
Published: July 2013

ABSTRACTLimited information exists on specific urban lawn care practices in the United States. We conducted a door‐to‐door lawn care survey in five North Carolina communities to determine suburban fertilizer, pesticide, and water use. These communities, Cary, Goldsboro, Kinston, New Bern, and Greenville, are mostly located within the Neuse River basin, a nutrient‐sensitive water resource. Residents in Cary used lawn care companies more than twice as frequently as residents in the other communities (43 compared with 20%). Cary had the smallest mean lawn size (445 m2), while the largest was in Goldsboro (1899 m2). Tall fescue [Festuca arundinacea Schreb.] was the predominant grass type in Cary (99%), and centipedegrass [Eremochloa ophiuroides (Munro) Hack.] or centipedegrass mixtures were the predominant grass types in Greenville and New Bern. Kinston had the lowest fertilizer usage with only 54% of the residents using fertilizer; Cary had the highest rate of 83%. The average N fertilizer rate applied to the lawns was dissimilar ranging from 24 to 151 kg N ha−1 Analysis of variance results for fertilizer rates and household income indicated a significant difference (P < 0.05) in application rate between high‐ and medium‐income levels and the low‐income level. Cary, Goldsboro, and Greenville had approximately the same number of fertilizer applications per year (1.5), whereas the average number of fertilizer applications per year in New Bern was 3.0. Most household residents (53%) used instructions on the bag and either grass type and/or lawn area to guide them on fertilizer application rates.
Measured Concentrations of Herbicides and Model Predictions of Atrazine Fate in the Patuxent River Estuary
Authors: McConnell Laura L. , Harman‐Fetcho Jennifer A. , Hagy James D. 
Published: July 2013

ABSTRACTThe environmental fate of herbicides in estuaries is poorly understood. Estuarine physical transport processes and the episodic nature of herbicide release into surface waters complicate interpretation of water concentration measurements and allocation of sources. Water concentrations of herbicides and two triazine degradation products (CIAT [6‐amino‐2‐chloro‐4‐isopropylamino‐s‐triazine] and CEAT [6‐amino‐2‐chloro‐4‐ethylamino‐s‐triazine]) were measured in surface water from four sites on 40 d from 4 Apr. through 29 July 1996 in the Patuxent River estuary, part of the Chesapeake Bay system. Atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) was most persistent and present in the highest concentrations (maximum = 1.29 μg/L). Metolachlor [2‐chloro‐6′‐ethyl‐N‐(2‐methoxy‐1‐methylethyl)‐o‐acetoluidide], CIAT, CEAT, and simazine (1‐chloro‐3,5‐bisethylamino‐2,4,6‐triazine) were frequently detected with maximum concentration values of 0.61, 1.1, 0.76, and 0.49 μg/L, respectively. A physical transport model was used to interpret atrazine concentrations in the context of estuarine water transport, giving estimates of in situ degradation rates and total transport. The estimated half‐life of atrazine in the turbid, shallow upper estuary was t1/2 = 20 d, but was much longer (t1/2 = 100 d) in the deeper lower estuary. Although most (93%) atrazine entered the estuary upstream via the river, simulations suggested additional inputs directly to the lower estuary. The total atrazine load to the estuary from 5 April to 15 July was 71 kg with 48% loss by degradation and 31% exported to the Chesapeake Bay. Atrazine persistence in the estuary is directly related to river flows into the estuary. Low flows will increase atrazine residence time in the upper estuary and increase degradation losses.