bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Cycling in Lake Wingra
Authors: Isirimah N. O. , Keeney D. R. , Dettmann E. H. 
Published: July 2010

AbstractMonitoring of the forms of N in water and sediment, and investigations of N cycling in Lake Wingra, a small, eutrophic, hardwater lake in southern Wisconsin, were conducted. Nitrification in the waters appeared to be by heterotrophs, while autotrophic nitrification dominated in the sediments. Rapid turnover of 15N‐NH4+ occurred in the waters, but not in the sediments, while 15N‐NO3− turnover was slow in the waters. In the sediments, denitrification and immobilization of 15N‐NO3− was rapid. About 80% of the added 15N‐NO3− was denitrified, the remainder being immobilized. Detrital‐15N was slowly mineralized in the sediments. Sediment‐water interchange occurred at a significant rate. About 40 µg NH4+‐N/liter sediment/day was formed from organic‐N, and subsequently released to the overlying water. Estimates of the overall average N content in various compartments indicated that about 50% of the “available” N was in the water, 20% in the macrophytes, and 30% in the sediments, while over 97% of the total N in the lake (to 30 cm sediment depth) was as sediment organic N. Consideration of seasonal changes in the NH4+‐N content of the sediments gave an average release rate of NH4+‐N of 7 to 29 mg m−2 day−1. This would supply from 3 to 14 metric tons of N to the lake water yearly. This is about the same order of magnitude as all external N inputs. Thus, even if the controllable point sources of N were eliminated, the biomass N in the lake water would not be significantly decreased.
The Role of Systems Analysis in the Use of Agricultural Wastes
Authors: Schulte D. D. , Kroeker E. J. 
Published: July 2010

AbstractAgricultural waste management is a multidisciplinary field which has grown in an attempt to solve problems of agricultural byproduct utilization and disposal. Development of meaningful solutions to agricultural waste management problems will be much simpler if practitioners and researchers educate one another and together work to solve the different problems of the producer. Many disciplines have already become involved in the problem‐solving process; yet, there is a need for a generalist in agricultural waste management who can bridge disciplinary gaps and promote effective cooperation between specialists in various fields of study. Systems analysis can serve a useful purpose in agricultural waste management by providing a focal point for cooperation between disciplines working on various aspects of the problem. Systems analysis has been used to: (i) provide a common structure for comparison of agricultural waste management strategies; (ii) identify processes or links within waste‐utilization systems which are costly or sensitive to operating conditions; (iii) predict effects of external constraints such as government policy, fertilizer taxes, and prices on the effectiveness of waste utilization strategies; (iv) yield information to predict where research funds would be spent most effectively; and (v) assist in technology transfer from researchers to practitioners through the aid of computer‐based educational models.
Soil and Microclimate Effects on Trifluralin Volatilization
Authors: Harper L. A. , White A. W. , Bruce R. R. , Thomas A. W. , Leonard R. A. 
Published: July 2010

AbstractA large fraction of many applied pesticides are lost to the air and dissipated. Microclimatological methods were used to determine the diurnal loss rates by volatilization of trifluralin applied and incorporated into the soil of a 1.26‐ha upper Piedmont plateau watershed. Trifluralin flux decreased to very low levels during daytime when surface soil water content was low even though turbulence, soil temperature, and evaporative demand were high. During nighttime, when evaporative demand subsided and the surface soil water content increased, the trifluralin flux increased as the surface soil water content increased. Trifluralin and lindane flux on a limited plot‐size study were compared and both pesticides reacted similarly to environmental conditions, except lindane volatilized more rapidly.When the soil surface was not wet, trifluralin and lindane fluxes appeared to be controlled by surface soil water content and the water content's effect on pesticide adsorption to the soil particle. Apparently, adsorption to the soil particle upon soil drying is a reversible process since efflux of the pesticides was rapid when soil was rewetted by dew or rainfall to above the equivalent of three molecular layers of adsorbed soil water. Under controlled soil‐water conditions, where the soil surface remained wetter than three molecular layers of adsorbed water, the pesticide fluxes responded to increased soil temperature and turbulence, and atmospheric stability conditions.
The Effects of Temperature and Soil Water on Conversion of DDT to DDE in Soil
Authors: Guenzi W. D. , Beard W. E. 
Published: July 2010

AbstractA laboratory study was conducted to determine the rates of DDT (1,1,1‐trichloro‐2,2‐bis [p‐chlorophenyl] ethane) degradation and DDE (1,1‐dichloro‐2,2‐bis [p‐chlorophenyl] ethylene) formation in soil. Degradation rates increased with higher temperatures and in the presence of water. Of the DDT mixed with Raber silty clay loam, 82.1, 74.5, 53.2, and 38.3% was recovered as DDT and 6.7, 12.5, 21.6, and 34.8% as DDE after 140 days incubation at 30, 40, 50, and 60C, respectively. A comparison of DDE formation in sterile and nonsterile soil showed that 84% of the conversion was due to a chemical process at 30C and 91% at 60C. In sterile systems at 30C, rates of DDE formation were similar in submerged soil and soil at 1/3 bar suction, and both were much higher than in air‐dried soil.
Nitrate‐nitrogen Movement through Soil as Affected by Soil Profile Characteristics
Authors: Devitt Dale , Letey J. , Lund L. J. , Blair J. W. 
Published: July 2010

AbstractThe contribution of agricultural practices to pollution of ground and surface waters by nitrogen is not completely known. Six tile systems installed on commercial farms with differing soil profile characteristics were selected for investigation. Soil solution samples were extracted from 61‐, 91‐, 122‐, and 183‐cm depths and analyzed for nitrate‐nitrogen, manganese and chloride concentrations, and electrical conductivity. Redox potential measurements were made at 91‐ and 183‐cm depths. Tensiometers were installed at 61‐, 91‐, and 122‐cm depths to measure hydraulic gradients. Tile effluent samples were also collected and analyzed. Data on redox potential, manganese concentrations, and nitrate‐nitrogen concentrations indicated that there was very low denitrificetion potential in coarse‐textured profiles and that the nitrate‐nitrogen concentration and movement were dependent on water movement and amounts of nitrate available for leaching. Irrigation management to provide low leaching fraction resulted in relatively higher nitrate‐nitrogen concentration in the tile effluent but smaller amounts of total nitrate lost as compared to irrigation management for high leaching fractions. Redox potentials and the chloride to nitrate‐nitrogen ratios indicated that subsurface layers of high clay content promote denitrificetion. With one exception, a smaller fraction of the applied nitrogen was lost in the tile effluent from profiles containing layers of high clay content as compared to the coarse‐textured profiles. The one exception was a profile having high clay content throughout which was recently brought under cultivation. Extremely high residual nitrate‐nitrogen was found in this profile which would account for the high concentrations in the tile effluent.
Nitrogen Transformations in Aerated Swine Manure Slurries
Authors: Loynachan T. E. , Bartholomew W. V. , Wollum A. G. 
Published: July 2010

AbstractA laboratory study was conducted to evaluate the effect of aeration rate, temperature, and manure loading rate on nitrogen transformations in swine manure slurries. Periodic samples were collected and analyzed for residual organic N, NH4‐N, NO2‐N, and NO3‐N, as well as NH3 volatilized from the aerated slurries. It was found that organic N decreased rapidly leaving a rather constant fraction after the first several weeks. At the end of the 83‐day study at 25C, one‐fourth of the N remained in solution in organic forms. This represents N that was not mineralized and consequently would not be lost during the denitrification process. From 16 to 26% of the added N was volatilized as NH3‐N and from 48 to 87% of the added C was evolved as CO2‐C during the study. Increasing temperature, increasing loading rate, and increasing aeration tended to increase volatilization of NH3 and CO2. An N balance at the conclusion of the study showed that 22 to 48% of the N was unaccounted for. While the mechanism responsible for the N losses was not determined, NH3 volatilization apparently predominated. The quantities of lost N increased with an increase in temperature. There appeared to be no relationship between the losses of N and changes in concentration of oxidized forms of N in solution. While nitrification occurred in extensively aerated swine‐manure slurries, about 1/4 of the original total N was not mineralized. As this represents a rather stable form and because only 3% of added N occurred in a mineral form at any given time, the extent of denitrification would be limited. Consequently, nitrification‐denitrification schemes probably have limited application to N removal from waste substances.
Evaluation of a Sulfur‐Thiobacillus denitrificans Nitrate Removal System
Authors: Sikora L. J. , Keeney D. R. 
Published: July 2010

AbstractAn evaluation of sulfur‐Thiobacillus denitrificans nitrate removal system as a means of denitrifying nitrified septic tank effluent was conducted. Duplicate 10 by 64 cm columns were filled with a 1/1 mixture (wt/wt) of elemental S (>2 mm) and dolomite chips (1 cm), and were pretreated by recycling an enrichment culture of T. denitrificans ATCC 23642 through the columns for 3 days. Continuous passage of the nitrified septic tank effluent (column influent) containing 40 µg NO3−‐N/ml through the columns resulted in nearly complete NO3− removal in 3.3 hours at steady‐state conditions (23C). Statistical analyses indicated that the denitrification kinetics closely resemble first order in the range of NO3− concentrations employed. Oxidation‐reduction potentials (Pt black electrodes) ranged from +160 to +300 mV. Analysis the gases produced showed that N2 was present in highest concentration. Sulfate was the major S end product and was present at relatively high concentrations (90 µg SO42−‐S/ml). A significant decrease in inorganic C occurred with depth in the columns while changes in organic C content were insignificant. A significant linear relationship was obtained between decreases in (NO3− + NO2−)‐N and production of S042−‐S. Passage of column effluent through 10 by 60 cm Plainfield sand columns did not significantly decrease SO42− levels. While use of this NO3− removal system appears promising, SO42− contamination of the ground water may limit its applicability.
Chemical Reduction of Nitrate by Ferrous Iron
Authors: Buresh R. J. , Moraghan J. T. 
Published: July 2010

AbstractKnowledge concerning the chemical reduction of NO3− to gaseous products, a process of potential practical significance as an antipollution device, is sparse. The influence of pH on chemical reduction of NO3−‐N (approximate concentration 25 ppm) by Fe2+ in the presence and absence of Cu2+ was studied over a pH range from 6 to 10. After 24‐hours of controlled pH incubations under a helium atmosphere NO3−, NO2−, N2O, NO, N2, and NH4+ were determined. The initial Fe2+/NO3− mole ratio was 8. Reduction of NO3− was negligible in the absence of Cu2+, but was pronounced above pH 7 in the presence of approximately 5 ppm Cu2+. Formation of NH4+ increased with pH and was the dominant process at pH 9 and 10. Nitrous oxide and N2 accumulations were greatest in the pH range from 8 to 8.5 and negligible at pH 6 and 10. Nitrite formation was small except at pH 9 and 10. Trace quantities of NO accumulated during incubation if the pH was allowed to drop below 6.Levels of Cu2+ and Fe2+ influenced the extent and nature of NO3− reduction at pH 8. Maximum reduction of NO3− (93%) and maximum gas production (equivalent to 61% of the original NO3−) occurred when the Fe2+/NO3− mole ratio was 12 and the Cu2+ level was approximately 10 ppm. The N2O/N2 mole ratio in the evolved gases decreased as the Cu2+ level was increased from approximately 1 to 10 ppm and as the Fe2+/NO3− mole ratio was increased from 8 to 12. Nitrate was relatively stable at a Cu2+ content of 0.1 ppm irrespective of the Fe2+/NO3− ratio.
Toxicity of Cadmium in the Freshwater Snail, Physa gyrina Say
Authors: Wier C. F. , Walter W. M. 
Published: July 2010

AbstractUsing both mature and immature snails and cadmium as the toxicant, 50% tolerance limits (TL50) for various exposure durations were determined graphically. The immature snails 96‐hour TL50 of 0.43 ppm indicates they are three times as sensitive to Cd as mature snails whose 96‐hour TL50 was 1.37 ppm. Survivors of bioassays and their offspring were observed. The rate of Cd uptake by snails exposed to 1.30 ppm Cd solution over a 24‐hour period was 0.550 ppm/hour. Following the 24‐hour exposure, the rate of elimination during the next 24 hours was 0.229 ppm/hour. The rate of uptake was nearly twice the rate of elimination, allowing accumulation of Cd in the snail. The higher the Cd concentration to which snails were exposed, the fewer the survivors, the lower their reproductive potential, and the shorter the period the young survived.
Some Thermal and Biological Effects of Forest Cutting in West Virginia
Authors: Lee R. , Samuel D. E. 
Published: July 2010

AbstractWater temperatures, benthic fauna, and aquatic insect emergence were observed in four small watersheds to document the effects of forest cutting. During the summer months, complete cutting caused mean temperature increases > 4C, and maximum temperature increases > 9C. The changes diminished to about one‐half after 3 years of natural hardwood regeneration. Complete cutting more than tripled the mean weekly range of stream temperature during summer, and decreased mean minimum temperatures during winter months by about 2C. Two orders, Diptera and Pelecypoda, accounted for most of the benthic biomass in watershed weir ponds; the former predominated in clear‐cut watershed ponds, and the latter in a control (forested area) pond. The control pond produced by far the highest total numbers and biomass of benthic fauna, and the greatest numbers of aquatic insects.
Nitrate Dynamics in Fall Creek, New York
Authors: Johnson Arthur H. , Bouldin David R. , Goyette Edward A. , Hedges Anne M. 
Published: July 2010

AbstractNitrate loss from a 330‐km2 rural watershed in central New York was monitored over a 31‐month period. Seasonal NO3‐N patterns were well defined with highest levels in the winter and lowest levels in the summer resulting from accumulation of NO3‐N in the soil profile during the growing season and leaching during the winter months. Stream water at the outlet of the watershed studied is used as a source of drinking water for some 20,000 people. Nitrate‐N concentrations at the drinking water intake currently do not exceed 3 mg/liter. Human activities affected NO3‐N levels, with dairying and sewage being the major contributors. If agriculture is expanded to its maximum acreage, keeping the present ratio of corn/hay/pasture/people, NO3‐N levels at the drinking water intake will not exceed present standards for drinking water.
DDT Degradation in Flooded Soil as Related to Temperature
Authors: Guenzi W. D. , Beard W. E. 
Published: July 2010

AbstractRaber silt loam was amended with 14C‐labeled DDT [1,1,1‐trichloro‐2,2‐bis(p‐chlorophenyl)ethane] and incubated under anaerobic conditions (flooded) at several selected temperatures for 140 days. Soil samples were analyzed for DOT degradation products at intervals during the experiment. DDT degradation rates were temperature dependent, and after 7 days recovery was 80, 64, 44, 10, and 48% at 30, 40, 50, 60, and 70C, respectively. DDT was not degraded at 2C. The first identifiable intermediate product was DDD [1,1‐dichloro‐2,2‐bis(p‐chlorophenyl)ethane] followed by DDMU [1‐chloro‐2,2‐bis(p‐chlorophenyl)ethylene]. Under these reducing conditions, DDD was not degraded at 30C, but degraded at temperatures of 40C and higher. 14C activity (applied as 14C‐DDT) remaining in the soil sample after solvent extraction, increased during degradation of the parent compound or of its degradation products. The maximum amount of activity in the non‐extractable fraction was found after 140 days in the 60C treatment, and represented 34% of the applied activity; whereas, 49.6% of the activity was extractable, only 15.6% of this was identifiable.
Release of Cadmium from Clays and Plant Uptake of Cadmium from Soil as Affected by Potassium and Calcium Amendments
Authors: Haghiri F. 
Published: July 2010

AbstractThe effects of percent K and/or Ca saturations on the release of Cd from Cd‐treated H‐clays (kaolinite and illite) and on the Cd availability to plants from Cd‐treated Canfield silt loam soil were determined. The concentration of Cd in the dialyzates from both kaolinite and illite clays increased as the percent Ca or K saturation of the clays in the suspension decreased. The release of Cd from both clays was greater in the presence of Ca than K. In a separate experiment, the concentration of Cd in soybean shoots (Glycine max L. Merr.) ‘Corsoy’ decreased with increasing percent Ca or K saturation of the soil. The results indicated that Cd uptake by soybean shoots could be impaired to a great extent by K application.
Effects of Sewage Sludge and Sludge Compost Applied to Soil on some Soil Physical and Chemical Properties
Authors: Epstein E. , Taylor J. M. , Chaney R. L. 
Published: July 2010

AbstractThe effects of different application rates of sewage sludge and sludge compost (0, 40, 80, 120, and 240 metric tons/ha) on soil physical and chemical properties were studied at two pH levels.Sludge application rates exceeding 120 metric tons/ha were difficult to apply and produced a cloddy seedbed, while the same rate of compost was easily applied and produced a friable seedbed. Sludge and compost increased the water content and the water retention of a silt loam soil. Both the sludge and compost increased the salinity and chloride levels of the soil to a level which may affect salt‐sensitive plants. The soil's cation exchange capacity increased as much as threefold as a result of the addition of sludge and compost. Nitrate‐nitrogen levels were highest at the 15–20 cm soil depth but decreased sharply below this level. Available phosphorus was high during the 2‐year study and appeared to be in excess of that needed for good crop growth.
Distribution of Plutonium in Trinity Soils after 28 Years
Authors: Nyhan J. W. , Miera F. R. , Neher R. E. 
Published: July 2010

AbstractThe soils of four intensive study areas located along the fallout pathway of Trinity, the first nuclear detonation, were sampled to determine soil plutonium concentrations as a function of distance from Ground Zero and soil depth.About half of the 239,240Pu in Trinity Site soils was found at the 5–20 cm depth in 1973 compared to total plutonium inventories found only in the upper 5 cm of soil about 20 years ago. Soil plutonium concentrations of samples collected at the same depth of each study area generally exhibited coefficients of variation > 1.2. Maximum penetration depths of 239,240Pu into Trinity Site soils were related to the presence of subsoil horizons containing carbonate accumulations and the maximum extent of rainwater penetration into these soil profiles.Increased amounts of plutonium were associated with < 100 µm fractions as distance from Ground Zero and soil depth increased. The < 100 µm fraction contained 1.2 and 89% of the plutonium in the topsoil at the study areas located 1.6 and 44 km from Ground Zero, respectively. Total amounts of 239,240Pu in the < 100 µm soil size fractions also generally increased with depth; at 1.6 km from Ground Zero, this size fraction contained 1.2% and 13% of the 239,240Pu found at the 0–2.5 and 5.0–10 cm depths, respectively.The soil plutonium data collected at Trinity Site is discussed relative to the sizes of Trinity fallout particles, setting meaningful health standards for plutonium in soils, and the distribution of plutonium in the biota of Trinity Site ecosystems.
Inability of Fish to Methylate Mercuric Chloride In Vivo
Authors: Pennacchioni A. , Marchetti R. , Gaggino G. F. 
Published: July 2010

AbstractExperiments were designed to establish whether mercuric chloride administered to rainbow trout (Salmo gairdneri Rich.) through the gills or by way of the mouth is converted in vivo to methylmercury. The mercury was measured by atomic absorption spectrophotometry and methylmercury determinations were performed by extraction and gas chromatography. The experiments show that while mercuric chloride administered by either method increased the total mercury content of kidney, liver, intestine, and muscle tissues, no evidence was found to support the hypothesis that mercuric chloride was methylated in fish to form methylmercury.
Methylation of Mercury in Agricultural Soils
Authors: Rogers R. D. 
Published: July 2010

AbstractMethylation of applied divalent mercury ion was found to occur in agricultural soils. The production of methylmercury was affected by soil texture, soil moisture content, soil temperature, concentration of the ionic mercury amendment, and time. Methylation was directly proportional to clay content, moisture content, temperature, and mercury concentration. After an initial build‐up of methylmercury in the soil, there appeared to be a mechanism that decreased the methylmercury content with increasing time.
Soil Characteristics and Corn Yield as Affected by Previous Applications of Poultry Manure
Authors: Liebhardt William C. 
Published: July 2010

AbstractThe effect of previous applications of poultry manure on yield and growth of corn and soil characteristics was studied on Elkton loamy sand. Plots with six levels of poultry manure (0, 22, 56, 90, 168, and 224 metric tons/ha) and a fertilizer treatment [224‐5‐186 kg/ha (N‐P‐K)] and 22 metric tons/ha poultry manure plus 224‐5‐168 kg/ha (N‐P‐K) were established with four replications in 1971. These amendments were applied for 3 years (1971, 1972, and 1973). Corn (Zea mays L.) was grown each year on these plots including 1974 and 1975; however, no soil amendments were applied in 1974 and 1975.Soil analysis of 1974 samples indicate that soil salinity resulting from previous poultry manure application was reduced substantially over the winter due to the leaching rain. As a result of the reduction in soil salinity, yield of corn did not experience the typical reduction when poultry manure was being applied. This indicates that excessive application of poultry manure will only be a problem in Delaware's sandy coastal plain soils in the year of application with respect to corn yield.Ear leaf at silking, whole plant, and grain samples indicated no toxicity problem as a result of previous applications of poultry manure.