bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Preferential Flow at Varying Irrigation Rates by Quantifying Mass Fluxes
Authors: Gish T. J. , Kung K.‐J. S. , Perry D. C. , Posner J. , Bubenzer G. , Helling C. S. , Kladivko E. J. , Steenhuis T. S.
Published: June 2010

Solute concentration and soluble dye studies inferring that preferential flow accelerates field‐scale contaminant transport are common but flux measurements quantifying its impact are essentially nonexistent. A tile‐drain facility was used to determine the influence of matrix and preferential flow processes on the flux of mobile tracers subjected to different irrigation regimes (4.4 and 0.89 mm h−1) in a silt loam soil. After tile outflow reached steady state either bromide (Br; 280 kg ha−1) or pentafluorobenzoic acid (PFBA; 121 kg ha−1) was applied through the irrigation system inside a shed (3.5 × 24 m). Bromide fluxes were monitored at an irrigation rate of 4.4 mm h−1 while PFBA fluxes were monitored at an irrigation rate of 0.89 mm h−1 At 4.4 mm h−1 nearly one‐third of the surface‐applied Br was recovered in the tile line after only 124 mm of irrigation and was poorly fit by the one‐dimensional convective–dispersive equation (CDE). On the other hand, the one‐dimensional CDE fit the main PFBA breakthrough pattern almost perfectly, suggesting the PFBA transport was dominated by matrix flow. Furthermore, after 225 mm of water had been applied, less than 2% of the applied PFBA had been leached through the soil compared with more than 59% of the applied Br. This study demonstrates that the methodology of applying a narrow strip of chemical to a tile drain facility is appropriate for quantifying chemical fluxes at the small‐field scale and also suggests that there may be a critical input flux whereby preferential flow is initiated.
Bacterial Removal and Protozoan Grazing in Biological Sand Filters
Authors: Bomo Anne‐Marie , Stevik Tor Kristian , Hovi Ine , Hanssen Jon Fredrik
Published: June 2010

The objective of the study was to investigate the importance of protozoan predation as a biological removal mechanism in sand filters used for purification of bacteria from wastewater. Eleven sand filter columns were seeded with a high dose of wastewater (70 mm d−1) and a high concentration (108 colony forming units [CFU] mL−1) of Aeromonas hydrophila (American Type Culture Collection [ATCC] 14715) for a period of 30 d. Water samples from three filter outlets were analyzed for the concentration of A. hydrophila In addition, one filter column was sacrificed each sampling day for the quantification of A. hydrophila, culturable bacteria (heterotrophic plate counts, HPC), total bacterial counts, and protozoa in the sand. The mean removal efficiency of A. hydrophila in the sand filter columns was 4.7 log units. The concentration of A. hydrophila in the sand filter effluent, however, had a clearly time‐dependent pattern from high (log 6) and unstable concentrations to low and more stable levels (log 2). The removal efficiency of A. hydrophila correlated significantly (P = 0.0005, r2 = 0.6) with numbers of protozoa in the sand filters. Significantly higher (P < 0.05) concentrations of A. hydrophila were observed in sand filter effluents from columns treated with the protozoan inhibitor cycloheximide, compared with nontreated columns. Results from the present study show that protozoan grazing plays an important role as a bacterial removal mechanism in sand infiltration systems.
Quantity and Quality of Runoff from a Beef Cattle Feedlot in Southern Alberta
Authors: Miller Jim J. , Handerek Brian P. , Beasley Bruce W. , Olson Edith C. S. , Yanke L. Jay , Larney Francis J. , McAllister Tim A. , Olson Barry M. , Selinger L. Brent , Chanasyk David S. , Hasselback Paul
Published: June 2010

Southern Alberta, which has a cold climate dominated by strong chinook winds, has the highest density of feedlot cattle in Canada. However, the quantity and quality of runoff from beef cattle (Bos taurus) feedlots in this unique region has not been investigated. Our objectives were to compare runoff quantity (1998–2002) with catch‐basin design criteria; determine concentrations of selected inorganic chemical parameters (1998–2000) in runoff in relation to water quality guidelines and the potential implications of irrigating adjacent cropland; and determine if total heterotrophs, total coliforms, and Escherichia coli (1998–2000) persisted in the catch‐basin water and soil. Runoff (<0.1 to 42.5 mm) for a 24‐h duration that included maximum peak discharge was less than the recommended design criteria of 90 mm based on runoff from 24 h of rainfall with a 30‐yr return period. We found that curve numbers between 52 and 96 (mode of 90) were required to match the USDA Natural Resources Conservation Service predicted runoff and actual runoff volumes. Total P posed the greatest threat to water quality guidelines, and K posed the greatest threat for exceeding crop fertilizer requirements if catch‐basin effluent was used as irrigation water. Water in the catch basin had continually high populations of E. coli throughout the study, with values ranging between log10 2 and log10 8 100 mL−1 In contrast, soil in the catch basin generally had low populations of E. coli that were <log10 2 g−1 wet wt., but at times higher populations between log10 2 and log10 6 g−1 wet wt. were also found.
A Comparison of In Situ Methods for Measuring Net Nitrogen Mineralization Rates of Organic Soil Amendments
Authors: Hanselman Travis A. , Graetz Donald A. , Obreza Thomas A.
Published: June 2010

In situ incubation methods may help provide site‐specific estimates of N mineralization from land‐applied wastes. However, there are concerns about the reliability of the data generated by the various methods due to containment artifacts. We amended a sandy soil with either poultry manure, biosolids, or yard‐waste compost and incubated the mixtures using four in situ methods (buried bags, covered cylinders, standard resin traps, and “new” soil–resin traps) and a conventional laboratory technique in plastic bags. Each incubation device was destructively sampled at 45‐d intervals for 180 d and net N mineralization was determined by measuring the amount of inorganic N that accumulated in the soil or soil plus resin traps. Containment effects were evaluated by comparing water content of the containerized soil to a field‐reference soil column. In situ incubation methods provided reasonable estimates of short‐term (<45 d) N mineralization, but long‐term (>45 d) mineralization data were not accurate due to a variety of problems specific to each technique. Buried bags and covered cylinders did not retain mineralized N due to water movement into and out of the containers. Neither resin method captured all of the mineralized N that leached through the soil columns, but the new soil–resin trap method tracked field soil water content better than all other in situ methods evaluated. With further refinement and validation, the new soil–resin trap method may be a useful in situ incubation technique for measuring net N mineralization rates of organic soil amendments.
Denitrification Enzyme Activity of Fringe Salt Marshes in New England (USA)
Authors: Wigand Cathleen , McKinney Richard A. , Chintala Marnita M. , Charpentier Michael A. , Groffman Peter M.
Published: June 2010

Coastal salt marshes are a buffer between the uplands and adjacent coastal waters in New England (USA). With increasing N loads from developed watersheds, salt marshes could play an important role in the water quality maintenance of coastal waters. In this study we examined seasonal relationships between denitrification enzyme activity (DEA) in salt marshes of Narragansett Bay, Rhode Island, and watershed N loadings, land use, and terrestrial hydric soils. In a manipulative experiment, the effect of nutrient enrichment on DEA was examined in a saltmeadow cordgrass [Spartina patens (Aiton) Muhl.] marsh. In the high marsh, DEA significantly (p < 0.05) increased with watershed N loadings and decreased with the percent of hydric soils in a 200‐m terrestrial buffer. In the low marsh, we found no significant relationships between DEA and watershed N loadings, residential land development, or terrestrial hydric soils. In the manipulation experiment, we measured increased DEA in N‐amended treatments, but no effect in the P‐amended treatments. The positive relationships between N loading and high marsh DEA support the hypothesis that salt marshes may be important buffers between the terrestrial landscape and estuaries, preventing the movement of land‐derived N into coastal waters. The negative relationships between marsh DEA and the percent of hydric soils in the adjacent watershed illustrate the importance of natural buffers within the terrestrial landscape. Denitrification enzyme activity appears to be a useful index for comparing relative N exposure and the potential denitrification activity of coastal salt marshes.
Improvements to Measuring Water Flux in the Vadose Zone
Authors: Masarik Kevin C. , Norman John M. , Brye Kristofor R. , Baker John M.
Published: June 2010

Evaluating the impact of land use practices on ground water quality has been difficult because few techniques are capable of monitoring the quality and quantity of soil water flow below the root zone without disturbing the soil profile and affecting natural flow processes. A recently introduced method, known as equilibrium tension lysimetry, was a major improvement but it was not a true equilibrium since it still required manual intervention to maintain proper lysimeter suction. We addressed this issue by developing an automated equilibrium tension lysimeter (AETL) system that continuously matches lysimeter tension to soil‐water matric potential of the surrounding soil. The soil‐water matric potential of the bulk soil is measured with a heat‐dissipation sensor, and a small DC pump is used to apply suction to a lysimeter. The improved automated approach reported here was tested in the field for a 12‐mo period. Powered by a small 12‐V rechargeable battery, the AETLs were able to continuously match lysimeter suction to soil‐water matric potential for 2‐wk periods with minimal human attention, along with the added benefit of collecting continuous soil‐water matric potential data. We also demonstrated, in the laboratory, methods for continuous measurement of water depth in the AETL, a capability that quantifies drainage on a 10‐min interval, making it a true water‐flux meter. Equilibrium tension lysimeters have already been demonstrated to be a reliable method of measuring drainage flux, and the further improvements have created a more effective device for studying water drainage and chemical leaching through the soil matrix.
Nitrogen Cycling through Swine Production Systems
Authors: Harper Lowry A. , Sharpe Ron R. , Parkin Tim B. , De Visscher Alex , van Cleemput Oswald , Byers F. Michael
Published: June 2010

Ammonia (NH3) emissions from animal systems have become a primary concern for all of livestock production. The purpose of this research was to establish the relationship of nitrogen (N) emissions to specific components of swine production systems and to determine accurate NH3 emission factors appropriate for the regional climate, geography, and production systems. Micrometeorological instrumentation and gas sensors were placed over two lagoons in North Carolina during 1997–1999 to obtain information for determining ammonia emissions over extended periods and without interfering with the surrounding climate. Ammonia emissions varied diurnally and seasonally and were related to lagoon ammonium concentration, acidity, temperature, and wind turbulence. Conversion of significant quantities of ammonium NH4+ to dinitrogen gas (N2) were measured in all lagoons with the emission rate largely dependent on NH4+ concentration. Lagoon NH4+ conversion to N2 accounted for the largest loss component of the N entering the farm (43% as N2); however, small amounts of N2O were emitted from the lagoon (0.1%) and from field applications (0.05%) when effluent was applied nearby. In disagreement with previous and current estimates of NH3 emissions from confined animal feeding operation (CAFO) systems, and invalidating current assumptions that most or all emissions are in the form of NH3, we found much smaller NH3 emissions from animal housing (7%), lagoons (8%), and fields (2%) using independent measurements of N transformation and transport. Nitrogen input and output in the production system were evaluated, and 95% of input N was accounted for as output N from the system.
Coupled Abiotic–Biotic Mineralization of 2,4,6‐Trinitrotoluene (TNT) in Soil Slurry
Authors: Schrader Paul S. , Hess Thomas F.
Published: June 2010

The explosive 2,4,6‐trinitrotoluene (TNT) is a contaminant of soils and ground waters worldwide. To help alleviate such environmental contamination, we investigated a coupled abiotic–biotic treatment scheme for remediating TNT‐contaminated soil in slurry solutions. Two types of soil were used (sandy and silt loam) to simulate different soils that might be found at actual sites. These soils were subsequently contaminated with 5000 mg kg−1 TNT. Mineralization of TNT was initially optimized for minimum reactant use (Fe3+ and H2O2) and maximum soil slurry percentage (percent solids) using modified Fenton reactions conducted in the absence of light followed by the addition of an uncharacterized aerobic biomass. Greater than 97% TNT degradation was observed under optimum reaction conditions for both soils. Using two optimum reactant concentrations for each soil, coupled abiotic–biotic reactions showed an increase in TNT mineralization, from 41 to 73% and 34 to 64% in the sandy soil (10 and 20% slurry, respectively, 1470 mM H2O2), and increases from 12 to 23% and 13 to 28% in the silt loam soil (5% slurry, 294 and 1470 mM H2O2, respectively). These results show promise in the use of combined abiotic–biotic treatment processes for soils contaminated with high concentrations of TNT.
Simulating Nitrogen Dynamics in Agricultural Soils Fertilized with Pig Slurry and Urea
Authors: Marchetti Rosa , Ponzoni Gilda , Spallacci Pasquale
Published: June 2010

Within the framework of an interregional project in the Emilia Romagna region of northern Italy, the coupled MACRO–SOILN model was chosen to estimate soil protective capacity against pollutants. The aim of our study was to evaluate the model to better identify key parameters and processes that influence N losses in agricultural soils. Nitrate N content was monitored in soil under corn (Zea maysL.) fertilized with urea and/or pig slurry, in two field experiments performed on four different soils: a Fienili clay, a Barco‐like silt, a Sant'Omobono silt loam, and a La Boaria silty clay soil. Measurements were compared with model predictions. For all soils, nitrate content was underestimated on average by 24 to 88% at lower N rates; it was overestimated by 1 to 104% at higher N rates. The root mean square error (RMSE) was equal to 81.1%. Simulation of crop N uptake and soil water flow, estimation of the ammonia losses at pig slurry spreading, and N transformation parameter setting were considered as possible error sources. The calibration of crop N uptake gave rise to good model efficiency index values. The RMSE for the simulation of soil water content varied between 9.8 and 20.2%. A more accurate setting of the ammonia losses and of the feces transformation parameter values could allow the RMSE for the simulation of soil nitrate content to be reduced by no more than 10 to 15%. It is possible for the model not to include the simulation of processes that could have relevant effects on the soil N dynamics.
Influence of Nutrient Levels on Uptake and Effects of Mercury, Cadmium, and Lead in Water Spinach
Authors: Göthberg Agneta , Greger Maria , Holm Karin , Bengtsson Bengt‐Erik
Published: June 2010

In Southeast Asia the aquatic macrophyte water spinach (Ipomoea aquatica Forsk.) is a popular vegetable that is cultivated in freshwater courses. These often serve as recipients for domestic and other sorts of wastewater that often contain a variety of pollutants, such as heavy metals. In addition, fertilizers are frequently used where water spinach is cultivated commercially for the food market. To estimate the importance of ambient nutrient concentrations for accumulation of mercury (Hg), cadmium (Cd), and lead (Pb) in water spinach, plants were exposed to nutrient solutions of different strength and with varying metal concentrations. Metal‐induced toxic effects, which might possibly affect the yield of the plants, were also studied. The lower the nutrient strength in the medium was, the higher the metal concentrations that accumulated in the different plant parts and the lower the metal concentration in the medium at which metal‐induced toxic effects occurred. Accordingly, internal metal concentrations in the plants were correlated to toxic effects. Plants exposed to metals retained a major proportion of the metals in the roots, which had a higher tolerance than shoots for high internal metal concentrations.
Effect of Cobalt Sorption on Metal Fractionation in Anaerobic Granular Sludge
Authors: Osuna M. Begoña , van Hullebusch Eric D. , Zandvoort Marcel H. , Iza Jon , Lens Piet N. L.
Published: June 2010

A sequential extraction procedure was applied to two anaerobic methanogenic sludges (Eerbeek and Nedalco) to examine the speciation of micro‐ and macronutrients in the sludges after cobalt sorption by exposing the sludge to a 1 mM Co solution for 4 d at pH 7 and 30°C. The effect of different physicochemical conditions on cobalt sorption was studied as well: effect of pH (6–8), effect of competition by a second trace element (Ni or Fe), modification of the granular matrix by glutaraldehyde or heat treatment, and EDTA (ethylenediaminetetraacetic acid) addition. Sorbed Co was found to distribute between the carbonates, organic matter + sulfides, and residual fractions. Cobalt adsorption resulted in an antagonistic interaction with other metals present in the granular matrix, evidenced by the solubilization of other trace elements (e.g., Ni, Cu, and Zn) as well as macronutrients (especially Ca and Fe). Modification of the sludge matrix by glutaraldehyde or heat treatment, or exposure to EDTA, led to serious modifications of the Co sorption capacity and strong interactions with multivalent cations (i.e., Ca2+ and Fe2+).
Transport and Fate of Nitrate in Headwater Agricultural Streams in Illinois
Authors: Royer Todd V. , Tank Jennifer L. , David Mark B.
Published: June 2010

Nitrogen inputs to the Gulf of Mexico have increased during recent decades and agricultural regions in the upper Midwest, such as those in Illinois, are a major source of N to the Mississippi River. How strongly denitrification affects the transport of nitrate (NO3–N) in Illinois streams has not been directly assessed. We used the nutrient spiraling model to assess the role of in‐stream denitrification in affecting the concentration and downstream transport of NO3–N in five headwater streams in agricultural areas of east‐central Illinois. Denitrification in stream sediments was measured approximately monthly from April 2001 through January 2002. Denitrification rates tended to be high (up to 15 mg N m−2 h−1), but the concentration of NO3–N in the streams was also high (>7 mg N L−1). Uptake velocities for NO3–N (uptake rate/concentration) were lower than reported for undisturbed streams, indicating that denitrification was not an efficient N sink relative to the concentration of NO3–N in the water column. Denitrification uptake lengths (the average distance NO3–N travels before being denitrified) were long and indicated that denitrification in the streambed did not affect the transport of NO3–N. Loss rates for NO3–N in the streams were <5% d−1 except during periods of low discharge and low NO3–N concentration, which occurred only in late summer and early autumn. Annually, most NO3–N in these headwater sites appeared to be exported to downstream water bodies rather than denitrified, suggesting previous estimates of N losses through in‐stream denitrification may have been overestimated.
Sorption of Apolar Aromatic Compounds to Soil Humic Acid Particles Affected by Aluminum(III) Ion Cross‐Linking
Authors: Lu Yuefeng , Pignatello Joseph J.
Published: June 2010

Sorption of hydrophobic compounds in soils often shows nonlinearity, competition, and hysteresis. Since such behaviors have been associated with organic polymers in glassy state, it has been postulated that some forms of soil humic substances are glassy. The glassy state is favored by properties that decrease the flexibility of macromolecules, such as cross‐linking, presence of unsaturated bonds, and high molecular weight. Polyvalent metal ions, which are abundant in soils, may cross‐link humic substances by coordinating to multiple functional groups on different strands. Accordingly, we prepared an Al3+–cross‐linked humic acid (Al‐HA) from the H+ form (H‐HA) of a soil humic acid by a flocculation technique that leaves Al ions bound to organic groups. Sorption of naphthalene and 1,2,4‐trichlorobenzene (TCB) on H‐HA was nonlinear, competitive, and slightly hysteretic, in agreement with previous studies showing glass transition temperatures of humic acids that lie above room temperature. Nonlinearity, competition, and hysteresis were all enhanced in Al‐HA, validating the hypothesis that metal ion cross‐linking enhances nonideal sorption. Application of a glassy polymer sorption model reveals that cross‐linking increases the affinity of solutes for the hole domain relative to the dissolution domain. The results (i) indicate that isolated, purified soil humic acid behaves like a glassy solid, (ii) indicate that metal‐ion cross‐linking creates a more rigid‐chain structure and supports a link between nonideal sorption and the glassy character of soil organic matter, and (iii) underscore the importance of metal ions on humic structure in relation to sorption of hydrophobic organic compounds.
Phosphorus Desorption Dynamics in Soil and the Link to a Dynamic Concept of Bioavailability
Authors: Koopmans G. F. , Chardon W. J. , de Willigen P. , van Riemsdijk W. H.
Published: June 2010

Soils under intensive livestock farming and heavily fertilized with animal manure may have elevated soil phosphorus (P) contents. We determined P desorption kinetics in batch experiments using soils from a pot experiment where grass was cropped on a P‐rich noncalcareous sandy soil without P addition, to lower the soil P content. A diffusion model was used to describe P desorption kinetics from a spherical aggregate. The model was calibrated with data from the batch experiments. Simulation results show that in the pot experiment, P desorption from the solid phase of the inner layers was initially far from equilibrium with the rest of the aggregate, but desorption came closer to equilibrium as the soil P content decreased further. A simple tool is presented, referred to as the dynamic bioavailability index (DBI), to determine whether kinetics of P desorption limits plant uptake. This tool is the dimensionless ratio of the modeled maximal diffusive flux from soil aggregates to solution and the plant uptake rate measured in the pot experiment. The DBI was initially much larger than one; the maximal possible P desorption rate exceeded the uptake rate, so uptake was not limited by desorption. The DBI stabilized at a value somewhat larger than one after a while, due to soil transport limitations. This decrease coincided with a large decrease of the P content in the grass to a value (far) below what is considered as optimal; the supply rate of P from soil to the root cannot meet the demand needed for optimal P uptake. The DBI could be seen as a promising onset to a new dynamic approach of bioavailability.
Potential Loss of Phosphorus from a Rice Field in Taihu Lake Basin
Authors: Zhang ZhiJian , Zhu YinMei , Guo PeiYong , Liu GuangSheng
Published: June 2010

Nonpoint‐source pollution by phosphorus (P) poses a threat to waters in the Taihu Lake basin in China. The potential transfer of P in rice (Oryza sativa L.) fields through surface drainage and subsurface flow was investigated under simulated conventional irrigation–drainage management. Surface drainage events were conducted to avoid overflow across the plots after heavy rainfall and for rice harvest, at which time P losses were also investigated. This study was conducted in 2001 in a long‐term rice field experiment. The experimental plots were treated with 0, 26, or 52 kg P ha−1 as superphosphate or 26 kg P ha−1 with equal parts of P supplied as superphosphate and pig manure. Phosphorus concentrations and loads in field floodwater on plots receiving P rapidly declined in a nonlinear manner before the first drainage, three weeks after fertilizer application. The combined application of fertilizer and manure P resulted in higher P transfer potential in field floodwater than with fertilizer P alone one week after P application. Phosphorus concentrations in interflow water sampled by Teflon suction cups inserted at a depth of 150 to 200 mm gradually increased within two weeks after P application, then declined. The concentration of P in interflow water was related to soil P buildup from long‐term P application, as well as recently applied P. The 26 kg P ha−1 treatment (the conventional P rate in this region) resulted in a loss of 0.74 kg total phosphorus (TP) ha−1 and a drainage‐weighted average concentration of 0.25 mg TP L−1 from the three surface drainage events. Results indicate that avoiding overflow drainage after P input and extending the time between P application and drainage may reduce P losses from rice paddies.
Preferential Flow of Bromide, Bentazon, and Imidacloprid in a Dutch Clay Soil
Authors: Júnior Rômulo Penna Scorza , Smelt Johan H. , Boesten Jos J. T. I. , Hendriks Rob F. A. , van der Zee Sjoerd E. A. T. M.
Published: June 2010

Leaching to ground water and tile drains are important parts of the environmental assessment of pesticides. The aims of the present study were to (i) assess the significance of preferential flow for pesticide leaching under realistic worst‐case conditions for Dutch agriculture (soil profile with thick clay layer and high rainfall) and (ii) collect a high‐quality data set that is suitable for testing pesticide leaching models. The movement of water, bromide, and the pesticides bentazon [3‐isopropyl‐1H‐2, 1,3‐benzothiadiazine‐4(3H)‐one‐2,2‐dioxide] and imidacloprid [1‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐N‐nitro‐2‐imidazolidinimine] was monitored in a clay soil for about 1 yr. The 1.2‐ha field was located in the central part of the Netherlands (51°53′ N, 5°43′ E). The soil was a Eutric Fluvisol cropped with winter wheat (Triticum aestivum L.). Tile drains were present at a 0.8‐ to 0.9‐m depth and the ground water level fluctuated between a 0.5‐ and 2‐m depth. All chemicals were applied in spring. None of the soil concentration profiles showed bimodal concentration distributions. However, for each substance the highest concentration in drain water was found in the first drainage event after its application, which indicates preferential flow. This preferential flow is probably caused by permanent macropores that were present in the 0.3‐ to 1.0‐m layer. At the time of the first drainage event, the drain water concentration of each substance was about an order of magnitude higher than its ground water concentration. Thus, the flux concentrations in drain water proved to be a more sensitive detector of preferential flow than the resident concentrations in the soil profile and the ground water.
Phosphorus Speciation in Manure‐Amended Alkaline Soils
Authors: Hansen Jeremy C. , Cade‐Menun Barbara J. , Strawn Daniel G.
Published: June 2010

Two common manure storage practices are stockpiles and lagoons. The manure from stockpiles is applied to soils in solid form, while lagoon manure is applied as a liquid. Soil amendment with manure in any form introduces a significant amount of phosphorus (P) that exists in both organic and inorganic forms. However, little is known about P speciation in manure stored under different conditions, or the subsequent forms when applied to soils. We used solution 31P nuclear magnetic resonance (NMR) spectroscopy and conventional P fractionation and speciation methods to investigate P forms in dairy manure and liquid lagoon manure, and to study how long‐term amendment with these manures influenced surface and subsurface soil P speciation. Our results show that the P forms in solid and lagoon manure are similar. About 30% of the total P was organic, mostly as orthophosphate monoesters. On a dry weight basis, total P was much higher in the solid manure. In the manure‐amended soils the total P concentrations of the surface soils were similar, regardless of manure type. Total P in the subsurface soil was greater in the lagoon‐manure‐amended soil than the solid‐manure‐amended subsurface soil. However, the fraction of organic P was greater in the subsurface of the solid‐manure‐amended soil. The NMR results indicate that the majority of organic P in the soils is phytic acid, which is enriched in the surface soils compared with the subsurface soils. These results provide insight into P speciation and dynamics in manure‐amended soils that will further increase our understanding on how best to manage manure disposal on soils.
Phosphorus Distribution in Dairy Manures
Authors: He Zhongqi , Griffin Timothy S. , Honeycutt C. Wayne
Published: June 2010

The chemical composition of manure P is a key factor determining its potential bioavailability and susceptibility to runoff. The distribution of P forms in 13 dairy manures was investigated with sequential fractionation coupled with orthophosphate‐releasing enzymatic hydrolysis. Among the 13 dairy manures, manure total P varied between 4100 and 18300 mg kg−1 dry matter (DM). Water‐extractable P was the largest fraction, with inorganic phosphorus (Pi) accounting for 12 to 44% of manure total P (1400–6800 mg kg−1) and organic phosphorus (Po) for 2 to 23% (130–1660 mg kg−1), respectively. In the NaHCO3 fraction, Pi varied between 740 and 4200 mg P kg−1 DM (4–44% of total manure P), and Po varied between 340 and 1550 mg P kg−1 DM (2–27% of total manure P). In the NaOH fraction, Pi fluctuated around 200 mg P kg−1 DM, and Po ranged from 130 to 630 mg P kg−1 DM. Of the enzymatically hydrolyzable Po in the three fractions, phytate‐like P dominated, measuring 26 to 605 mg kg−1 DM, whereas monoester P and DNA‐like P were relatively low and less variable. Although concentrations of various P forms varied considerably, significant correlations between manure total P and certain P forms were observed. For example, H2O‐extracted Pi was correlated with total manure P (R2 = 0.62), and so was NaOH‐extracted Po (R2 = 0.81). Data also show that the amount of P released by a single extraction with sodium acetate (100 mM, pH 5.0) was equivalent to the sum of P in all three fractions (H2O‐, NaHCO3–, and NaOH‐extractable P). Thus, a single extraction by sodium acetate buffer could provide an efficient evaluation of plant‐available P in animal manure, while the sequential fractionation approach provides more detailed characterization of manure P.
Analysis of Volatile and Semivolatile Hydrocarbons Recovered from Steam‐Classified Municipal Solid Waste
Authors: Leahy Joseph G. , Carrington Thomas E. , Eley Michael H.
Published: June 2010

Hazardous household wastes comprise a significant proportion of municipal solid waste (MSW), and therefore serve as the source of many toxic or carcinogenic organic chemicals that are released in the environment through landfill gases or leachates. In the present study, we demonstrate the utility of the steam classification process in removing hazardous semivolatile organic compounds (SVOCs) and volatile organic compounds (VOCs) from MSW. Steam classification is a patented technology that involves the treatment of MSW with steam under pressure to yield a cellulosic biomass product that can be used as a fuel or in building materials. The SVOCs and VOCs from the waste off‐gases are collected in the steam condensate and in an effluent charcoal filter. The results of this study show that at least two SVOCs and at least 17 VOCs can be removed from the waste. The most commonly identified compounds were diethylphthalate, styrene, 1,4‐dichlorobenzene, and toluene in the condensates, and styrene, 1,1,1‐trichloroethane, and toluene in the charcoal filters. On a weight basis, aromatic hydrocarbons were primarily recovered in the condensates, while the chloroaliphatic hydrocarbons were recovered almost exclusively from the charcoal filters. 1,3‐Dichlorobenzene, 1,4‐dichlorobenzene, and chloroform together comprised nearly 50% of the 4470 μg kg−1 average mass of SVOCs and VOCs recovered from about 454 kg of MSW in these experiments. Toxicity characteristic leaching procedure (TCLP) analyses showed that steam classification recovered at least 75 to 91% of tested analytes. Overall, these results suggest that steam classification represents an effective technology for a significant reduction or the removal of hazardous organics from the waste stream, and, consequently, in reducing the extent of environmental contamination associated with landfill leachates and gases.
Photodegradation of the Endocrine‐Disrupting Chemical 4‐Nonylphenol in Biosolids Applied to Soil
Authors: Xia Kang , Jeong Chang Yoon
Published: June 2010

There is increasing concern about the environmental fate and impact of biosolids‐associated anthropogenic organic chemicals, among which 4‐nonylphenol (4‐NP) is one of the most studied chemicals. This is primarily because 4‐NP is an endocrine disruptor and has been frequently detected in environmental samples. Due to its high hydrophobicity, 4‐NP has high affinity for biosolids. Land application of 4‐NP–containing biosolids could potentially introduce large quantities of this chemical into the environment. A laboratory experiment was conducted to investigate the effect of artificial sunlight on 4‐NP degradation in biosolids applied to soil. When exposed to artificial sunlight for 30 d, the top‐5‐mm layer of biosolids showed a 55% reduction of 4‐NP, while less than 15% of the 4‐NP was degraded when the biosolids were kept in the dark. Our results indicate that sensitized photolysis reaction plays an important role in reducing the levels of 4‐NP in land‐applied biosolids. Surface application rather than soil incorporation of biosolids could be effective in reducing biosolids‐associated organic chemicals that can be degraded through photolysis reactions. However, the risks of animal ingestion, foliar deposition, and runoff should also be evaluated when biosolids are applied on the soil surface.
Enzyme Activities and Arylsulfatase Protein Content of Dust and the Soil Source: Biochemical Fingerprints?
Authors: Acosta‐Martínez V. , Zobeck T. M.
Published: June 2010

Little is known about the potential of enzyme activities, which are sensitive to soil properties and management, for the characterization of dust properties. Enzyme activities may be among the dust properties key to identifying the soil source of dust. We generated dust (27 and 7 μm) under controlled laboratory conditions from agricultural soils (0–5 cm) with history of continuous cotton (Gossypium hirsutum L.) or cotton rotated with peanut (Arachis hypogaea L.), sorghum [Sorghum bicolor (L.) Moench], rye (Secale cereale L.), or wheat (Triticum aestivum L.) under different water management (irrigated or dryland) and tillage (conservation or conventional) systems. The 27‐ and 7‐μm dust samples showed activities of β‐glucosidase, alkaline phosphatase, and arylsulfatase, which are related to cellulose degradation and phosphorus and sulfur mineralization in soil, respectively. Dust samples generated from a loam and sandy clay loam showed higher enzyme activities compared with dust samples from a fine sandy loam. Enzyme activities of dust samples were significantly correlated to the activities of the soil source with r > 0.74 (P < 0.01). The arylsulfatase proteins contents of the soils (0.04–0.65 mg protein kg−1 soil) were lower than values reported for soils from other regions, but still dust contained arylsulfatase protein. The three enzyme activities studied, as a group, separated the dust samples due to the crop rotation or tillage practice history of the soil source. The results indicated that the enzyme activities of dust will aid in providing better characterization of dust properties and expanding our understanding of soil and air quality impacts related to wind erosion.
Changes in Soil Nitrogen and Phosphorus under Different Broiler Production Systems
Authors: Kratz Sylvia , Rogasik Jutta , Schnug Ewald
Published: June 2010

In a field study, soils of four conventional free‐range and organic broiler runs were analyzed for N and P concentrations in the years 2000 and 2001. Zones of different use intensity by broilers were identified on the free runs and mean zonal nutrient contents were compared with each other. Intensity of use by birds and spatial distribution of soil nutrient concentrations were found to be related to each other. Fecal N input by broilers resulted in accumulation of soil mineral nitrogen (Nmin) contents down to a 90‐cm sampling depth. In highly frequented “hot spots,” plant requirement as defined by the German “N‐Basis‐Sollwert” (110 kg/ha Nmin) for grassland was exceeded in all four cases. This implies an increased environmental risk of ammonia volatilization and nitrate leaching. Fecal P input by broilers resulted in accumulation of plant‐available and thus mobile soil P (phosphorus extracted with calcium‐acetate‐lactate [PCAL] and phosphorus extracted with water [Pw]) in the most intensely used zones. In these areas, soil P contents exceeded 90 mg/kg PCAL (upper limit of soil test P defined in Germany for optimum plant yield) by as much as 217 mg/kg, which indicates an enhanced risk of P loss from the soil via runoff or leaching. The conclusion might be drawn that, with regard to nutrient loss from free‐run soils, intensive indoor production in a closed system may be more environmentally neutral than conventional free‐range or organic production. However, to put this into perspective, the scope of the environmental risk connected with spatially limited point accumulation of nutrients should be considered. Furthermore, an environmental evaluation must also account for the fate and environmental effects of the broiler litter produced inside the broiler house.
Sorption and Degradation of Alachlor and Metolachlor in Ground Water Using Green Sands
Authors: Lee Taeyoon , Benson Craig H.
Published: June 2010

Reactive barriers are used for in situ treatment of contaminated ground water. Waste green sand, a by‐product of gray‐iron foundries that contains iron particles and organic carbon, was evaluated in this study as a low‐cost reactive material for treating ground water contaminated with the herbicides alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)acetanilide] and metolachlor [2‐chloro‐6′‐ethyl‐N‐(2‐methoxy‐1‐methylethyl)‐o‐acetoluidide]. Batch and column tests were conducted with 11 green sands to determine transport parameters and reaction rate constants for the herbicides. Similar Fe‐normalized rate constants (KSA) were obtained from the batch and column tests. The KSA values obtained for green sand iron were also found to be comparable with or slightly higher than KSA values for Peerless iron, a common reactive medium used in reactive barriers. Partition coefficients ranging between 3.6 and 50.2 L/kg were obtained for alachlor and between 1.0 and 54.8 L/kg for metolachlor, indicating that the organic carbon and clay in green sands can significantly retard the movement of the herbicides. Partition coefficients obtained from the batch and column tests were similar (±25%), but the batch tests typically yielded higher partition coefficients for green sands exhibiting greater sorption. Calculations made using transport parameters from the column tests indicate that a 1‐m‐thick reactive barrier will result in a 10‐fold reduction in concentration of alachlor and metolachlor for seepage velocities less than 0.1 m/d provided the green sand contains at least 2% iron. This level of reduction generally is sufficient to reduce alachlor and metolachlor concentrations below maximum contaminant levels in the United States.
Kinetics of Chromate Adsorption on Goethite in the Presence of Sorbed Silicic Acid
Authors: Garman Stephanie M. , Luxton Todd P. , Eick Matthew J.
Published: June 2010

The adsorption of chromate on mineral surfaces has received much attention due to its toxicity in natural systems. Spectroscopic studies have demonstrated that chromate forms inner‐sphere complexes on variable‐charge surfaces. However, in natural systems chromate has been observed to be fairly mobile, which has been explained by the presence of naturally occurring ligands competing with chromate for mineral surface sites. Silicic acid is a ubiquitous ligand in soil and water environments and also sorbs strongly to variable‐charge surfaces. Yet little research has examined its influence on chromate adsorption to variable‐charge surfaces such as goethite. This study examined the influence of silicic acid (0.10 and 1.0 mM) on the adsorption kinetics of chromate (0.05 and 0.10 mM) on goethite over a range of common soil pH values (4, 6, and 8). The rate and total quantity of chromate adsorption decreased in all the experiments except at a pH value of 4 and a chromate concentration of 0.05 mM The inhibition of chromate adsorption ranged from 3.1% (pH = 4, Si = 0.10 mM, chromate = 0.10 mM) to 83.3% (pH = 8, Si = 1.0 mM, chromate = 0.05 mM). The rate of chromate adsorption decreased with an increase in pH and silicic acid concentration. This was attributed to a reduction in the surface potential of goethite on silicic acid adsorption as well as a competition for surface sites. The presence of naturally occurring ligands such as silicic acid may be responsible for the enhanced mobility of chromate in natural systems and demonstrates the importance of competitive adsorption for evaluating the mobility of trace elements.
Degradation of N,N′‐Dibutylurea (DBU) in Soils Treated with only DBU and DBU‐Fortified Benlate Fungicides
Authors: Lee Linda S. , Sassman Stephen A. , Bischoff Marianne , Turco Ronald F.
Published: June 2010

N,N′‐dibutylurea (DBU) is a breakdown product of benomyl [methyl 1‐(butylcarbamoyl)‐2‐benzimidazole carbamate], the active ingredient in Benlate fungicides, and has been proposed to cause crop damage after the use of Benlate 50 DF fungicide (DuPont, Wilmington, DE). Our research focused on DBU persistence after application into soil. We assessed DBU persistence on direct application of DBU (carbonyl–14C) at two concentrations (0.08 and 0.8 μg DBU kg−1) to seven soils and two potting mixes in soil microcosms incubated at various combinations of soil water potential (−0.03 or −0.1 MPa) and temperature (23, 33, 44°C). For two soils at a subset of treatment variables we assessed DBU persistence in the presence of Benlate DF and SP fungicide formulations. Parent compounds, metabolites, and 14CO2 were tracked using chromatographic analysis with radioassay and UV detection, liquid scintillation counting, and post‐extraction oxidation of the soil. DBU degradation was primarily microbial and for most soil–treatment combinations, half‐lives were less than 2 wk. DBU degradation was retarded at the lower soil water potential and enhanced at 33°C. In the presence of the formulation, DBU degradation was slower for one soil type. The longest half‐life observed in any case was less than 7 wk; therefore, long‐term persistence of DBU applied to soils through a Benlate application is very unlikely.
Effects of Aeration on Water Quality from Septic System Leachfields
Authors: Potts David A. , Görres Josef H. , Nicosia Erika L. , Amador José A.
Published: June 2010

We conducted a pilot‐scale study at a research facility in southeastern Connecticut to assess the effects of leachfield aeration on removal of nutrients and pathogens from septic system effluent. Treatments consisted of lysimeters periodically aerated to maintain a headspace O2 concentration of 0.209 mol mol−1 (AIR) or vented to an adjacent leachfield trench (LEACH) and were replicated three times. All lysimeters were dosed with effluent from a septic tank for 24 mo at a rate of 12 cm d−1 and subsequently for 2 mo at 4 cm d−1 LEACH lysimeters had developed a clogging mat, or biomat, 20 mo before the beginning of our study. The level of aeration in the AIR treatment was held constant regardless of loading rate. No conventional biomat developed in the AIR treatment, whereas a biomat was present in the LEACH lysimeters. The headspace of LEACH lysimeters was considerably depleted in O2 and enriched in CH4, CO2, and H2S relative to AIR lysimeters. Drainage water from AIR lysimeters was saturated with O2 and had significantly lower pH, five‐day biological oxygen demand (BOD5), and ammonium, and higher levels of nitrate and sulfate than LEACH lysimeters regardless of dosing rate. By contrast, significantly lower levels of total N and fecal coliform bacteria were observed in AIR than in LEACH lysimeters only at the higher dosing rate. No significant differences in total P removal were observed. Our results suggest that aeration may improve the removal of nitrogen, BOD5, and fecal coliforms in leachfield soil, even in the absence of a biomat.
Seawater Neutralization of Alkaline Bauxite Residue and Implications for Revegetation
Authors: Menzies N. W. , Fulton I. M. , Morrell W. J.
Published: June 2010

Reaction of bauxite residue with seawater results in neutralization of alkalinity through precipitation of Mg‐, Ca‐, and Al‐hydroxide and carbonate minerals. In batch studies, the initial pH neutralization reaction was rapid (<5 min), with further reaction continuing to reduce pH for several weeks. Reaction with seawater produced a residue pH of 8 to 8.5. Laboratory leaching column studies were undertaken to provide information on seawater neutralization of the coarse‐textured fraction of the waste, residue sand (RS), under conditions comparable with those that might be applied in the field. An 0.80‐m‐deep column of RS was neutralized by the application of the equivalent of 2‐m depth of seawater. In addition to lowering the pH and Na content of the residue, seawater neutralization resulted in the addition of substantial amounts of the plant nutrients Ca, Mg, and K to the profile. Similar results were also obtained from a field‐scale assessment of neutralization. However, the accumulation of precipitate, consisting of hydrotalcite, aragonite, and pyroaurite, in the drainage system may preclude the use of in situ seawater neutralization as a routine rehabilitation practice. Following seawater neutralization, RS remains too saline to support plant growth and would require fresh water leaching before revegetation.