bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluoride Solubility in Dust Emission from an Aluminum Smelter
Authors: Arnesen A. K. M.
Published: July 2010

Fluorides are emitted to the atmosphere as hydrogenfluoride (HF) gas and in particle forms from the production of aluminum (Al). The solubilities of fluoride (F) and Al in particle emission from an aluminum smelter were studied in relation to pH and dust/water ratio. A soil column experiment was performed to study the retention of dust‐components in soil and the effect on chemistry of soil leachate. The solubility of F in the dust decreased when pH in water was increased from 2 to 6.5. From pH 6.5 to 9, the solubility was almost constant. The solubility of Al decreased with increased pH up to pH about 7.5. The amounts of water‐soluble F increased from about 3.5% of the dust with dust/water ratio 1:100 to about 5.8% with dust/water ratio 1:10 000. The corresponding results for Al were 1.3 and 2% of the dust. Relatively high leaching of F occurred from columns with quartz‐sand. High leaching occurred from humus. A podzolic Bs‐horizon retained almost all of the added F. Leaching of Al and organic material were significantly elevated by the highest dust input in all the columns. Leaching of Na was elevated by the dust‐input, but differed less between the columns. Dust particles deposited will to a great extent solubilize and react with the soil. The retention of F and Al in the soil depends on soil type, with little sorption in organic soil and strong sorption in mineral horizons with Al‐oxides/hydroxides.
Phosphorus Transformations in the Sediments of Delaware's Agricultural Drainageways: II. Effect of Reducing Conditions on Phosphorus Release
Authors: Sallade Y. E. , Sims J. T.
Published: July 2010

Most agricultural fields in Delaware's Inland Bays' watershed are high or excessive in P from long‐term applications of poultry litter (PL) and fertilizers and many are arable only because they have been drained by large open ditches. The possible role of sediments in these ditches in P loading to the Inland Bays was assessed in laboratory studies. Sediments collected from 17 ditches ranged in biologically available P (BAP) from 5 to 1218 mg P kg−1 and in soil test P from 3 to 62 mg P kg−1. Sequential fractionation indicated that Al‐P (0.05 N NH4F) and Fe‐P (1.0 N NaOH) were the predominant forms of sediment inorganic P. The degree of phosphorus saturation (DPS), defined as BAP ÷ PSI (P sorption index, a rapid measure of sediment P sorption capacity), averaged 46 and 37% in the top and bottom sediments, respectively. The potential for P release from sediments to drainage waters was determined by incubating all sediments under flooded, anoxic conditions for 21 d. The effects of time and temperature (7 and 35°C) on P release were determined in a separate study with six sediments incubated for 42 d. Initial P in solution was well correlated with BAP (r = 0.74***) and organic matter (r = 0.66***), while P release after 21 d was well correlated with DPS (r = 0.75***) and total Fe‐oxide content (r = 0.66***). A critical sediment DPS value of 40% is proposed to target drainage ditches with higher potential to release P to overlying waters.
Heavy Metals of the 20th Century Recorded in Oak Tree Rings
Authors: Jonsson Arne , Eklund Mats , Håkansson Karsten
Published: July 2010

Tree rings from 23 oak trees (Quercus robur L.) were used to monitor historical heavy metal emissions from anthropogenic sources on a regional scale. The concentrations of Cd and Pb in the tree rings were analyzed using atomic absorption spectrophotometry. From the results, chronologies were constructed representing the heavy metal background load of the 20th century. The chronologies were compared with calculated estimates of the accumulation of these metals in soil. The method of tree‐ring analysis proved to be useful for monitoring Cd and Pb emissions from diffuse sources when applied as a complement to other methods, in this case calculated accumulation. This study also indicates that no radial transport occurs in the inward direction, from sapwood to heartwood, but that outward diffusion to some extent might occur at least within the sapwood. The conspicuous difference between the soil/wood ratios for Cd and Pb implies that a larger proportion of the soil Cd is taken up by the tree than is the case for Pb.
Methyl Mercury Contamination and Emission to the Atmosphere from Soil Amended with Municipal Sewage Sludge
Authors: Carpi Anthony , Lindberg Steven E. , Prestbo Eric M. , Bloom Nicolas S.
Published: July 2010

In an effort to identify the effect of municipal sewage sludge application on mercury (Hg) concentrations in soil, we studied the contamination of sludge‐amended soil with inorganic and methyl Hg and the emission of these contaminants to the atmosphere using a Teflon dynamic flux chamber. The routine application of municipal sewage sludge to cropland significantly increased both total and methyl Hg in surface soil from 80 to 6100 µg kg−1 and 0.3 to 8.3 µg kg−1, respectively. Both inorganic and methyl Hg were transported from the sludge/soil matrix to the environment by emission to the atmosphere, however, there was no indication of Hg transport in limited soil water lysimeter experiments. Our data from soil amended with municipal sewage sludge represent the first quantitatively measured terrestrial source of methyl mercury (MeHg) to the atmosphere. Sludge‐amended soil emitted an average of 12 to 24 pg m−2 h−1 of monomethyl Hg and ∼100 ng m−2 h−1 of inorganic Hg to the atmosphere. A simple dispersion model suggests that sludge‐amended soil may increase regional atmospheric MeHg concentrations by ∼5%. These data highlight the need for further research to quantify the transport of Hg from sludge‐amended soil and identify the sources of MeHg in the atmosphere.
Application of Biosolids to Degraded Semiarid Rangeland: Nine‐Year Responses
Authors: White C. S. , Loftin S. R. , Aguilar R.
Published: July 2010

Rangeland restoration through surface application of biosolids (municipal sewage sludge) is an increasing practice. Biosolids supply both organic matter and available nutrients that are lacking in degraded rangeland soils. This study investigated the effects of biosolids applications of 0, 22.5, 45, and 90 Mg ha−1 to a degraded rangeland in 1985 on the soil chemical properties and N mineralization potentials 8 and 9 yr after the application, respectively. Following an initial increase in proportion to the application rate, levels of water‐extractable Ca, Mg, Na, nitate (NO3‐N), and electrical conductivity declined to that near the control soils after 8 yr. Nearly all diethylenetriaminepentaacetic acid (DTPA)‐extractable metals (Fe, Zn, Cu, Cd, and Pb) were highest in the collection 4 yr after application, but were near concentrations in the control soil after 8 yr. Nitrogen mineralization potentials were significantly higher (P < 0.05) in the 45 and 90 Mg ha−1 applications after 9 yr, indicating that site fertility remained higher even though most soil chemical properties were returning to untreated levels.
Mineralizable Nitrogen in Broiler Litter: II. Effect of Selected Soil Characteristics
Authors: Gordillo R. M. , Cabrera M. L.
Published: July 2010

Broiler litter (BL) is a mixture of chicken (Gallus gallus domesticus) manure and bedding material that is commonly used as fertilizer for crops and pastures. Knowledge of the factors that determine the amount of potentially mineralizable N in BL is needed to estimate adequate application rates. Limited evidence suggests that soil characteristics such as texture can significantly affect the amounts of net N mineralized from BL. This work was conducted to compare the kinetics of N mineralization of the same BL in nine different soil samples, and to determine the effect of selected soil characteristics on the amount and rate of decomposition of potentially mineralizable N in BL. Samples from the same BL were mixed with nine soils (150 mg organic N kg−1, −0.02 MPa) and incubated at 25°C for 146 d. A two‐pool, first‐order kinetics model adequately described cumulative net N mineralized from the litter, which ranged from 364 to 784 g N kg−1 organic N. Multiple regression analysis generated statistically significant equations that identified the ratio of (sand content/water content at field capacity) and pH as soil characteristics with a significant effect on the fast and slow pools of mineralizable N. Combining a predictive equation for total mineralizable N based on BL characteristics with a predictive equation for total mineralizable N based on soil characteristics, we generated an equation that predicts total mineralizable N based on BL and soil characteristics. Future work should further test this equation and correlate plant N uptake with predicted values of potentially mineralizable N in BL.
Ammonia and Nitrous Oxide Emissions from Sprinkler Irrigation Applications of Swine Effluent
Authors: Sharpe R. R. , Harper L. A.
Published: July 2010

In the USA, swine operations produce more than 14 Tg of manure each year. About 30% of this manure is stored in anaerobic lagoons before effluent applications to land. Although land application is the preferred means of disposal and can supply nutrients for crop production, it leads to gaseous emissions of ammonia (NH3) and nitrous oxide (N2O), both of which can be detrimental to the environment. Our objectives were to quantify gaseous emissions of NH3 and N2O from effluent applications under field conditions and to relate N2O fluxes to soil water content. Three applications of swine effluent were applied to oat (Avena sativa “GA‐Mitchell”) starting at heading stage. Gaseous fluxes were determined from gas concentration profiles and the momentum balance transport coefficient. About 13% of the ammonium (NH4‐N) was lost through drift or volatilization of NH3 during irrigation. An additional 69% was volatilized within 24 h of application. Nitrous oxide emissions were low before effluent applications (19 mg N2O‐N ha−1 d−1) and increased to 0.25 t o 0.38 kg N2O‐N ha−1 d−1 after irrigation. Total N2O emissions during the measurement period were 4.7 kg N2O‐N ha−1, which was about 13% of total N applied. The large losses of NH3 and N2O illustrate the difficulty of basing effluent irrigation schedules on N concentrations and the data indicate that compared to N2O, NH3 emissions made greater contributions to N enrichment of the environment.
Variability of Leaf Phosphorus among Sugarcane Genotypes Grown on Everglades Histosols
Authors: Glaz Barry , Deren Christopher W. , Snyder George H.
Published: July 2010

The P content of drainage water of the Everglades Agricultural Area (EAA) of Florida must be reduced by at least 25% from a baseline mean calculated using 1978 through 1988 data. This minimum P reduction is one of several measures to sustain much of the unique habitat of remaining natural regions of the Everglades. The objectives of this study were to evaluate variability in leaf tissue P concentration among elite sugarcane (interspecific hybrids of Saccharum spp.) clones and to recommend sampling strategies to detect differences among clones. Leaf samples were collected four times per annual crop in the plant‐cane and first‐ratoon crops from three fields, representing low, medium, and high available soil P. Leaf P of sugarcane should be tested at several locations in at least two crop years, and at least once, but preferably twice per crop. The clone with the most leaf P had 0.65 g P kg−1 leaf tissue more than the clone with the least. This difference among leaves allowed us to speculate that P removal may differ by about 8.5 kg ha−1 among commercial cultivars and that genetic improvement of this trait could be feasible. If further studies show that differences in leaf P concentration can reliably predict differences in total P removal from a sugarcane field, then classification of cultivars for leaf P concentration could make available to EAA sugarcane farmers another best management practice (BMP) to reduce P content of their drainage waters.
Agricultural Nutrient Losses to Surface Water in the Netherlands: Impact, Strategies, and Perspectives
Authors: Van der Molen Diederik T. , Breeuwsma Auke , Boers Paul C. M.
Published: July 2010

Nutrient emissions from agricultural activities have become the dominant source of nutrient loads to freshwater in the Netherlands. This paper focuses on nutrient emissions from agriculture, emphasizing nutrient loads to surface waters, and strategies and perspectives to reduce these emissions. Although adverse environmental effects of intensive agriculture have been known for several years, it was not until 1987 that stabilization of animal manure production and application began. Since 1991 manure application rates have been reduced. Recently, application standards have been replaced by agriculturally inevitable nutrient losses and environmentally acceptable nutrient losses and these losses are reduced to an equilibrium fertilization in 2010, defined as the supply of manure and fertilizers that meets crop uptake and compensates for inevitable losses. In the 1980s, the most important tool to manage nutrient losses was a manure bookkeeping; recently a mineral bookkeeping has been introduced. Agricultural nutrient emissions to and their impact upon surface waters have been estimated from field experiments and model calculations, which indicate that the proposed legislation will not significantly improve water quality. Increasing areas will be saturated with P, especially where intensive livestock farming is located on sandy soils. Tailor‐made regional programs are necessary to achieve ecological restoration of surface waters, with priority for catchment areas with vulnerable receiving waters. These programs may consist of a further reduction of nutrient application rates, hydrological measures, selection of crops that extract P from the soils or measures to increase the P adsorption capacity of the soil, and buffer strips.
A Nonelectrostatic Surface Complexation Model for Lead Sorption on Soils and Mineral Surfaces
Authors: Van Benschoten John E. , Young William H. , Matsumoto Mark R. , Reed Brian E.
Published: July 2010

A nonelectrostatic surface complexation model is applied to three data sets of increasing complexity: synthetic data for Pb adsorption to hydrous ferric oxide (HFO); data from the literature involving Pb adsorption to three mineral surfaces (goethite, alumina, and silica); and data for Pb adsorption on a field soil. The model is intended for engineering applications (e.g., soil remediation) rather than to provide a comprehensive description of sorption phenomena. The model is simple enough that it can be implemented on a standard spreadsheet and in its simplest form requires only two fitting parameters. Proton stoichiometry for the surface reactions is determined using Kurbatov plots; total site density (ST) and surface‐binding constant (Kpb) are fit to experimental sorpfion data. Complexation reactions between Pb and major ligands are included in the model. Although similar models have been presented previously by other researchers, dissolved solute speciation often was ignored and applications focused on trace metal adsorption and not on soil contamination and remediation. Model applications to Pb sorption data for mineral surfaces have shown excellent correlation with experimental data (r2 values from 0.95 to 0.99, SE of 3–7%). For an environmental soil, r2 values f rom 0.82 t o 0.96 and std errors from 4 to 8% were observed. The model simulates effects of solution chemistry on sorption nearly as well as traditional surface complexation models, but with fewer fitting parameters. Interpretation of fitted parameters and guidelines for model use are discussed.
Mercury Concentrations in Soils Adjacent to a Former Chlor‐Alkali Plant
Authors: Rule J. H. , Iwashchenko M. S.
Published: July 2010

The mean soil mercury (Hg) concentration (1.060 mg−1) for samples collected within 2 km of a former chlor‐alkali plant (National Priority List 418) in Saltville, VA, was determined to be approximately 17 times higher than regional background soil samples (0.063 mg kg−1). Anomalous values as defined by the mean of the regional background plus three standard deviations were found at all but one of 28 sampling sites within a 2‐km radius from the former chlor‐alkali plant. Soil organic C, topographic factors, wind patterns, and elevation were variables significantly related to Hg concentration as determined by analysis of data by multiple regression. Soil Hg levels decreasing with distance from the former plant were indicative of a point source distribution pattern. A made land soil type (Udorthent), which appears to be a by‐product of the chlor‐alkali manufacturing process, was found proximal to the former plant site and contained about 68 times (4.310 mg kg−1) more Hg than the regional background concentration. The significant environmental Hg contamination is likely to remain in the Saltville ecosystem for a very long time due to continued emissions from waste ponds. The range of contamination, especially downwind of the plant site, most probably extends well beyond the bounds of the present study area.
Dissolution of Trapped Nonaqueous Phase Liquids in Sand Columns
Authors: Fortin J. , Jury W. A. , Anderson M. A.
Published: July 2010

Soil column experiments were designed to evaluate the dissolution and leaching under continuous water flow of two immobilized nonaqueous phase liquids (NAPL): o‐xylene, which is lighter than water (LNAPL) and o‐dichlorobenzene, which is denser than water (DNAPL). Major differences were observed in the mobility and dissolution of the LNAPL and the DNAPL under continuous leaching. Under water‐saturated conditions and downward flow, the trapped LNAPL was removed from sand columns by dissolution and by mobilization of small droplets. In contrast, the DNAPL remained trapped in the soil matrix during the leaching phase and was removed by dissolution only. The model used to describe the data assumes that the NAPL is trapped in the soil volume as ideal spheres of initial diameter d0. The transport parameters of the model were determined by a separate tracer experiment, so that the only parameter fitted to the resident residual NAPL and outflow observations was the initial diameter of the spheres. The sphere model described the data fairly well, with optimum initial sphere diameter of 0.12 cm for o‐dichlorobenzene and varying between 0.17 to 0.21 cm for o‐xylene. The optimum diameter of the spheres was used to calculate the length of the mass transfer zone (Lm) over which solution passing through the NAPL region changes from zero NAPL concentration to NAPL water solubility. Lm varied between 7.9 to 11.1 cm for o‐xylene, and from 3.7 cm in the finer sand to 5.2 cm in the coarser material for o‐dichlorobenzene.
Patchiness in Microbial Nitrogen Transformations in Groundwater in a Riparian Forest
Authors: Jacinthe Pierre‐Andre , Groffman Peter M. , Gold Arthur J. , Mosier Arvin
Published: July 2010

We measured microbial N transformations in 15 cm diam. by 40 cm intact horizontal sections of aquifer material (mesocosms), taken from a riparian forest in Rhode Island, USA, incubated under ambient conditions. The mesocosms allowed us to measure these transformations on the same scale as hydrologic tracer methods (Br−/NO−3 ratios) that measure net NO−3 removal. Our objective was to reconcile discrepancies between hydrologic tracer and microbial measurements in previous studies where laboratory‐based microbial NO−3 consumption measurements were much lower than in situ hydrologic measurements of net NO−3 removal. We hypothesized that small “patches” of organic matter in the aquifer matrix, which are easily missed when sampling for microbial measurements, are “hotspots” of NO−3 removal and are responsible for these discrepancies. Mesocosms were subjected to three treatments [Br− only, Br− + 15NO−3 Br− + 15NO−3 + dissolved organic carbon (DOC)]. Solution (NH+4, NO−3, dissolved organic N) and gaseous (N2O, 15N2O, and 15N2) inputs and outputs to the mesocosms were measured over a 132‐d incubation, followed by destructive sampling for the presence of patches and residual 15N in aquifer matrix and patch material. Total (gross) NO−3 consumption by denitrification and immobilization was greater than net removal of NO−3 measured by Br−/NO−3 ratios. Net NO−3 consumption was only observed in mesocosms that contained “patches” of organic matter and was not increased by addition of DOC, suggesting that these patches, which represent <1% of aquifer weight, are critical to groundwater NO−3 removal in riparian forests.
Phytoremediation of a Radiocesium‐Contaminated Soil: Evaluation of Cesium‐137 Bioaccumulation in the Shoots of Three Plant Species
Authors: Lasat Mitch M. , Fuhrmann Mark , Ebbs Stephen D. , Cornish Jay E. , Kochian Leon V.
Published: July 2010

A field study was conducted to investigate the potential of three plant species for phytoremediation of a 137Cs‐contaminated site. Approximately 40‐fold more 137Cs was removed from the contaminated soil in shoots of red root pigweed (Amaranthus retroflexus L.) than in those of Indian mustard [Brassica juncea (L.) Czern] and tepary bean (Phaseolus acutifolius A. Gray). The greater potential for 137Cs removal from the soil by A. retroflexus was associated with both high concentration of 137Cs in shoots and high shoot biomass production. Approximately 3% of the total 137Cs was removed from the top 15 cm of the soil (which contained most of the soil radiocesium) in shoots of 3‐too‐old A. retroflexus plants. Soil leaching tests conducted with 0.1 and 0.5 M NH4NO3 solutions eluted as much as 15 and 19%, respectively, of the soil 137Cs. Addition of NH4NO3 to the soil, however, had no positive effect on 137Cs accumulation in shoots in any of the species investigated. It is proposed that either NH4NO3 solution quickly percolated through the soil before interacting at specific 137Cs binding sites or radiocesium mobilized by NH4NO3 application moved below the rhizosphere, becoming unavailable for root uptake. Further research is required to optimize the phytotransfer of the NH4NO3‐mobilized 137Cs. With two croppings of A. retroflexus per year and a sustained rate of extraction, phytoremediation of this 137Cs‐contaminated soil appears feasible in <15 yr.
Biosolids Effects on Tobosagrass and Alkali Sacaton in a Chihuahuan Desert Grassland
Authors: Benton Mark W. , Wester David B.
Published: July 2010

Environmentally responsible use of anaerobically digested biosolids (municipal sewage sludge) is an increasingly urgent ecological and societal concern. There is relatively little information available on effects of biosolids in arid and semiarid rangelands. The purpose of this research was to evaluate effects of rate, season, and number of consecutive years of biosolids application on tobosagrass (Hilaria mutica) and alkali sacaton (Sporobolus airoides), two commonly occurring native grasses in the Chihuahuan desert grassland. Biosolids were topically applied at rates of 0, 7, 18, 34, or 90 Mg ha−1 either during the dormant season or just prior to the onset of the growing season for 1 yr only, or for 2, 3, or 4 consecutive years; one‐half of the experimental plots were provided supplemental irrigation. In general, biosolids increased plant length and aboveground standing crop of these species. Plants responded more to dormant season application than to growing season application in the first year of the study. Carry‐over effects from earlier applications on current year's growth were species‐specific and depended on growing conditions.
Soluble Organic Carbon and Carbon Dioxide Fluxes in Maize Fields Receiving Spring‐Applied Manure
Authors: Gregorich E. G. , Rochette P. , McGuire S. , Liang B. C. , Lessard R.
Published: July 2010

More than 19 million Mg of dairy manure are produced annually in the Canadian provinces of Quebec and Ontario, and most of it is spread on agricultural fields. Quantitative information on the impact of manure management practices on levels of soluble organic carbon (SOC) and emissions of CO2 is important for assessing whether this management significantly contributes to increasing atmospheric CO2 concentrations. The objective of this study was to measure the effects of dairy cattle manure (applied at 0, 56, and 112 Mg ha−1) on SOC levels in, and soil surface CO2 fluxes from, a typical maize (Zea mays L.) field in central Canada, from April to October. The higher rate of manure increased both the CO2 emissions and the SOC levels by a factor of two to three compared with the control. Fluxes of CO2 were very low immediately after thaw, increased sharply following manure application and increased again in mid‐June at the time when temperature and soil moisture increased; thereafter, fluxes declined throughout the rest of the season. Over the season, which was drier than normal, SOC was not a good predictor of CO2 flux. Carbon dioxide flux increased proportionately less for the second 56 Mg ha−1 increment of manure added than for the first increment. Factors other than the quantity of S OC limited soil respiration at the highest manure application rate. Carbon dioxide is contributed to the atmosphere at a lower rate, and proportionately more manure C is retained in soil with increasing levels of manure applied.
Hydrologic Controls on Phosphorus Loss from Upland Agricultural Watersheds
Authors: Gburek William J. , Sharpley Andrew N.
Published: July 2010

Development of strategies for controlling P loss from upland agricultural watersheds requires an ability to identify specific source areas of P at field and farm scales, and to predict their resultant effects at the watershed scale. Key to identification of P source areas is defining the interaction between P availability over the landscape and its potential for movement to the watershed outlet by runoff and erosion. A current weakness in quantifying this interaction is determining specific zones of runoff and erosion within a watershed, that is, source areas for the P transport mechanisms. Research results from a series of studies within a small, upland agricultural watershed in east‐central Pennsylvania show that the zones of runoff production, and consequently the areas ultimately controlling most P transport, are often a limited and identifiable portion of the landscape. Quantifying the hydrologic controls on P transport within and from a watershed in this way allows us to focus management options on small and definable portions of the total watershed that contribute most export.
Phosphorus Loss in Agricultural Drainage: Historical Perspective and Current Research
Authors: Sims J. T. , Simard R. R. , Joern B. C.
Published: July 2010

The importance of P originating from agricultural sources to the nonpoint source pollution of surface waters has been an environmental issue for decades because of the well‐known role of P in eutrophication. Most previous research and nonpoint source control efforts have emphasized P losses by surface erosion and runoff because of the relative immobility of P in soils. Consequently, P leaching and losses of P via subsurface runoff have rarely been considered important pathways for the movement of agricultural P to surface waters. However, there are situations where environmentally significant export of P in agricultural drainage has occurred (e.g., deep sandy soils, high organic matter soils, or soils with high soil P concentrations from long‐term overfertilization and/or excessive use of organic wastes). In this paper we review research on P leaching and export in subsurface runoff and present overviews of ongoing research in the Atlantic Coastal Plain of the USA (Delaware), the midwestem USA (Indiana), and eastern Canada (Quebec). Our objectives are to illustrate the importance of agricultural drainage to nonpoint source pollution of surface waters and to emphasize the need for soil and water conservation practices that can minimize P losses in subsurface runoff.
Reducing Phosphorus Losses from Surface‐Irrigated Fields: Emerging Polyacrylamide Technology
Authors: Lentz R. D. , Sojka R. E. , Robbins C. W.
Published: July 2010

Most P losses from surface‐irrigated fields occur via runoff, are associated with eroded sediment, and can be minimized by eliminating irrigation‐induced erosion. A convenient new practice that eliminates furrow irrigation‐induced soil losses uses a high molecular weight, anionic polyacrylamide (PAM) applied to initial irrigation inflows. We hypothesized that, compared to control furrows, PAM treatment would reduce field losses of ortho P, total P, NO3, and lower tailwater chemical oxygen demand (COD). Two PAM treatments were tested: I10 applied 10 mg L−1 PAM only during the furrow advance (i.e., the application was halted after runoff began) and C1 applied 1 mg L−1 PAM continuously throughout the irrigation. Soil was Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid) with 1.6% slope. Initial inflows were cut back from 23 to 15 L min−1 after 1.5 to 6 h. Total soil loss over four irrigations was 3.06 Mg ha−1 for control furrows vs. 0.33 (C1) and 0.24 (I10) for PAM‐treated furrows. Ortho‐P and total P concentrations in control tailwaters were five to seven times that of PAM treatments, and COD levels were four times those of PAM treatments. Runoff in controls was two times that of PAM‐treated furrows. PAM‐I10 lowered furrow stream nutrient concentrations more than did PAM‐C1, but owing to disparities in runoff, the two treatments produced similar cumulative sediment and nutrient mass losses. The PAM is effective, convenient, and economical, and greatly reduces P and organic material (COD) losses from surface‐irrigated fields.
A Laboratory Evaluation of Trace Element Mobility from Flooding and Nutrient Loading of Coeur d'Alene River Sediments
Authors: La Force M. J. , Fendorf S. E. , Li G. C. , Schneider G. M. , Rosenzweig R. F.
Published: July 2010

The main stem (MSCDR) and south fork (SFCDR) of the Coeur d'Alene River, Idaho, are contaminated with heavy metals from many years of mining. To assess the potential impacts of flooding on water quality in the river system, contaminants in undisturbed sediments were subjected to selective extraction, and their rates of release measured in simulated laboratory flooding experiments. To simulate flooding, 18 columns were constructed allowing the sediment‐water interface to be monitored for pH, Eh, and dissolved concentrations of As, Fe, Mn, Pb, and Zn. These columns were subjected to four types of treatments. The first two involved overlaying the columns with N2(g)‐ or air‐purged river water, whereas the latter two involved overlaying sediment columns with N2(g)‐ or air‐purged river water amended with C and N. Treatment with unamended river water resulted in the immediate release of Zn at an average concentration of 10.4 mg L−1 from sediment taken along the MSCDR at Cataldo, ID. Treatment with either oxic or anoxic river water amended with glucose and N resulted in an order of magnitude increase in sediment microbial density. These biotic changes correlated with fivefold to 100‐fold increases in the release of trace elements into the aqueous phase. Our results suggest that heavy metal loading of waters in the Coeur d'Alene system occurs not only as a result of the resuspension of particulate matter, but also as a result of transformations that are either directly or indirectly mediated by sediment microbiota. Undisturbed sediments currently situated in the riverbanks of the MSCDR and SFCDR have the capacity to release contaminants into the river system during flooding. This release could be dramatically enhanced by increased nutrient levels into the CDA river system.
Bioavailability of Copper and Zinc in Soils Treated with Alkaline Stabilized Sewage Sludges
Authors: Luo Y. M. , Christie P.
Published: July 2010

A glasshouse experiment was conducted to determine the bioavailability of Cu and Zn in a sandy loam and a clay loam. Spring barley (Hordeum vulgare L. cv. Forrester) was grown for 40 d in the two soils following application of alkaline‐stabilized sewage sludge. The soils were mixed with sludge product to give mixtures equivalent to fresh sludge cake application rates of 30, 90, and 120 Mg/ha. Unamended controls and all sludge‐treated soils except those receiving 90 Mg/ha were sequentially extracted to fractionate Cu and Zn into five operationally defined chemical forms. About 74% of total Cu and 80% of total Zn remained in the RESD fraction of the sludge‐amended soils. The largest extractable Cu fraction was OM‐Cu while the largest extractable Zn fraction was FeMnOX‐Zn in both types of sludge product and in both soils. The EXCH and CARB fractions together comprised <2% of total Cu and Zn in sludge‐amended soils. The sludge product raised soil pH and, except for EXCH‐Zn, increased the concentrations of both metals in the four extractable soil fractions. The sludge product increased barley shoot uptake of Cu by 112% and of Zn by 67% on average. However, sludge application decreased the shoot Zn concentration by 39% in the clay loam. This may be due to a decrease in EXCH‐Zn in the soil together with a dilution effect in the shoots resulting from a positive yield response to the sludge cake. Plant metal uptake was correlated (P < 0.05) with the various soil fractions, particularly EXCH‐Cu and CARB‐Zn.
A Comparison of Three Kriging Methods Using Auxiliary Variables in Heavy‐Metal Contaminated Soils
Authors: Juang Kai‐Wei , Lee Dar‐Yuan
Published: July 2010

Characterization of the spatial distribution of pollutants in contaminated soils is important for risk assessment and soil reclamation. In this study, three kriging methods using auxiliary variables, cokriging, kriging combined with regression, and kriging combined with Q‐mode factor analysis, were used for interpolation of heavy metal concentrations in a contaminated site. The three interpolation methods were evaluated for whether or not they could make better use of an auxiliary variable for estimation of the spatial distribution of heavy metals. A heavy metal contaminated site about 10 ha in area, situated in Taoyuan, Taiwan, was studied. The results demonstrate that better use of the auxiliary variable in interpolations of the target variable was made using kriging combined with regression compared to using cokriging or kriging combined with Q‐mode factor analysis. The results also show that the spatial distribution patterns of the target variables estimated using kriging combined with Q‐mode factor analysis were more similar to those estimated using kriging combined with regression than were those estimated using cokriging. In addition, kriging combined with regression and kriging combined with Q‐mode factor analysis could avoid negative estimates, which occur in cokriging. Moreover, both of them were more robust than cokriging. Simultaneous estimation of spatial distributions of several target variables using an auxiliary variable was demonstrated for the kriging combined with Q‐mode factor analysis procedure. However, for only one target variable, kriging combined with regression was simpler and less cumbersome than cokriging.
Effects of Carbon Dioxide and Nitrogen on Growth and Nitrogen Uptake in Ponderosa and Loblolly Pine
Authors: Johnson D. W. , Thomas R. B. , Griffin K. L. , Tissue D. T. , Ball J. T. , Strain B. R. , Walker R. F.
Published: July 2010

The purpose of this paper is to summarize the results of a series of greenhouse and open‐ top chamber studies on the effects of N and elevated atmospheric CO2 on ponderosa and loblolly pine (Pinus ponderosa Laws, and P. taeda L.) to evaluate common patterns of response. Growth response to elevated CO2 ranged from zero to more than 1000%, depending largely upon N status. In both species, growth response to CO2 was greater under moderate N deficiency than under extreme N deficiency or N sufficiency/excess. Elevated CO2 generally caused lowered tissue N concentrations in many (but not all) cases, which in turn resulted in smaller increases in N uptake than in biomass. Growth response to N ranged from −50 (in ponderosa pine) to more than 1000%, depending upon the N status of the control medium. Growth response to N was enhanced by elevated CO2 when N was in the extreme deficiency range but not when N was in the moderate deficiency range. In two separate studies, ponderosa pine responded negatively to high N inputs, and in each case this response was mitigated by elevated CO2. Collectively, these results show that (i) N deficiency is a continuum rather than a step function, (ii) responses to elevated CO2 vary across this continuum of N deficiency, and (iii) elevated CO2 greatly enhances growth response to N additions when N is initially in the extremely deficient range.
Dairy Manure Management: An Application of Probabilistic Risk Assessment
Authors: Johnson Andrew , Thurow Amy Purvis , Vietor Donald
Published: July 2010

Contemporary agricultural enterprises are having difficulty dealing with changing public perceptions about the environmental consequences of current management practices. This study was initiated to investigate the role Probabilistic Risk Assessment (PRA) could play in managing risks and communicating risk information to regulators and the public. The utility of PRA for dairy manure and wastewater management systems was evaluated on three Texas dairies beginning in spring 1992. Information collected from dairymen, along with computerized risk analysis, was used to develop risk estimates for various environmental hazards associated with the dairies. Qualitative and quantitative analysis of individual probability estimates allowed evaluation of the risks posed by various potential nutrient loss pathways. Integration of these probability estimates with simple cost‐effectiveness evaluations provided a risk/cost‐effectiveness value used in comparing alternative waste management technologies. Results indicate PRA, wedded with cost‐effectiveness analysis, may provide a new and effective way for the agricultural community to evaluate, manage, and communicate risk information.
Movement of Simazine in Runoff Water from Citrus Orchard Row Middles as Affected by Mechanical Incorporation
Authors: Troiano J. , Garretson C.
Published: July 2010

In California, preemergence herbicide residues have been measured in runoff water from citrus orchards that resulted from winter rainfall. This study measured the effect of rainfall on the redistribution of herbicides within a citrus orchard and the effect that shallow mechanical incorporation had on residue movement. Simulated rainfall treatments were applied to plots within a citrus orchard where simazine was applied only to row middles. Simazine (2‐chloro‐4, 6‐bis [ethylamino]‐s‐triazine) movement in runoff water was compared between middles that were either undisturbed, the normal orchard practice, or subject to shallow mechanical incorporation. In undisturbed middles, simazine concentration in runoff water collected from the first of two simulated rain events averaged 0.87 mg L−1; simazine concentration in runoff water from a second event applied 7 d later averaged 0.40 mg L−1. Shallow mechanical incorporation of row middles decreased runoff water volume from the first simulated rain event by approximately 50% with simazine concentration decreased to 0.14 mg L−1; runoff water volume was unaffected at the second rainfall event but simazine concentration remained low at 0.07 mg L−1. Total simazine mass removed from both events, which also accounts for mass recovered in furrow soil, was estimated at 13.1% of the amount applied to row middles in undisturbed plots compared to only 2.1% in mechanically disturbed middles. We conclude that ambient rainfall is unreliable for incorporation of preemergence herbicides into orchard soil with low infiltration, and that shallow mechanical incorporation should be tested under commercial citrus growing conditions.
Modeling Pesticide Transport in an Irrigated Field with Variable Water Application and Hydraulic Conductivity
Authors: Ellerbroek D. A. , Durnford D. S. , Loftis J. C.
Published: July 2010

The impact of spatially varying hydraulic properties on chemical transport in the unsaturated zone has been extensively studied. However, few studies have investigated the impact of variable water application on chemical transport. This paper uses field data and a modeling study to evaluate the relative importance of intrinsic and extrinsic sources of variability on pesticide transport through a field soil. Saturated hydraulic conductivity represented the source of intrinsic variability and water application was studied as a source of extrinsic variability. A conceptual model of water flow and solute transport was developed based on results from soil cores, shallow groundwater samples, and dye studies. One important result of the field study was the detection of low levels of the applied pesticide metolachlor ([2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methyethyl) acetamide]) in groundwater samples collected at 2.6 m below ground surface after an average application of only 0.097 m of water. Dye studies indicated gravity‐driven fingered flow occurred in the subsoil, which may explain the early detection of pesticide in the shallow groundwater. Monte Carlo simulations revealed that the variability of water application had a greater impact on pesticide transport than the variability of saturated hydraulic conductivity at this site. Therefore, improving sprinkler uniformity represents an important best management practice (BMP) for reducing groundwater contamination by agricultural chemicals under the conditions studied.
Preferential Transport of a Bromide Tracer Applied in a Pulse of Ponded Water
Authors: Timlin D. J. , Ahuja L. R. , Heathman G. C.
Published: July 2010

The objective of this study was to quantify relations between preferential transport of a solute and initial water content, infiltration rate, and porosity in a field soil where preferential transport was mainly due to soil heterogeneity. We measured the horizontal and vertical distribution of a tracer chemical applied with ponded water to study the flow paths of the tracer. The soil at the site is a Bosville fine sandy loam (fine‐mixed, thermic Albaquic Paleudalfs). Strontium bromide (SrBr2) tracer was applied with a dye (methylene blue) in a 100 or 50‐mm pulse of water to soil within eight double ring infiltrometers. After 48 h the soil in each infiltrometer was sampled to 0.7 m. Twelve horizontally oriented, continuous soil samples 0.1 m long were collected at each depth. There were very few dye stains of root hairs, root channels, and pores to a depth of about 50 to 80 mm. Recoveries of Br to 0.5 m ranged from 36 to 56% applied. Bromide recovery was negatively correlated with initial water content and positively with total porosity. Below 0.35 m in depth resident solute concentration at a sampling position was positively correlated with concentration in the layer above indicating preferential vertical flow paths. It appeared that a large fraction of solute transport was through the highly porous areas of the cross‐section of soil bounded by the infiltrometer ring. The preferential transport of Br in this study was influenced largely by the properties of the clay layer at 0.35 m that had the lowest conductivity and lowest porosity in the profile and appeared to have cracks filled with sand.
Protein Content in Dairy Cattle Diets Affects Ammonia Losses and Fertilizer Nitrogen Value
Authors: Paul J. W. , Dinn N. E. , Kannangara T. , Fisher L. J.
Published: July 2010

Altering feeding strategies for dairy cattle (Bos taurus) may reduce manure N excretion and NH3 emission from the manure. We determined the effect of dietary formulation on NH3 emission immediately following manure excretion and the availability of manure N for plant growth. Manure (urine and feces) was collected from dairy cattle fed diets containing crude protein levels of 16.4% (T1High), 15.3% (T1Med), and 12.3% (T1Low) in trial 1, and 18.3% (T2High), 16.7% (T2Med), and 15.3% (T2Low) in trial 2. Ammonia emission was measured in the laboratory for up to 48 h. Emissions during the first 24 h following manure excretion were 38 and 23% of the total manure N from Diets T1High and T1Low, and 22, and 15% of the total manure N from Diets T2High and T2Low. Manure NH+4 concentration and pH were positively related to the dietary crude protein level. Manure from cattle‐fed diets T1Med and T1Low were applied to soil at two rates to determine short‐term N availability for three plantings of corn (Zea mays L.) grown for 30 d each in the greenhouse. The recovery of manure and fertilizer N in the plants and the soil for the first two plantings was 48, 31, and 103% for the T1Med, T1Low, and inorganic N treatments, respectively. Whole farm N utilization for diets T2High and T2Low were estimated at 18 and 23%, respectively. Feeding diets lower in crude protein increases efficiency of N on the dairy farm, decreases NH3 emissions following excretion but also decreases the short‐term N availability of the manure.
Soluble Trace Metals in Alkaline Stabilized Sludge Products
Authors: McBride M. B.
Published: July 2010

The application of alkaline sludge products as liming agents to agricultural soils is now commonplace. Laboratory investigations of water extracts from two alkali‐stabilized sludge products used in New York State reveals that 40 to 50% of the total Cu, 15 to 25% of the total Ni, and 11 to 13% of the Mo dissolved out of the sludge product into water, whereas much smaller fractions of the Cd, Zn, Pb, Ag, and Hg were immediately water soluble. Speciation techniques, including differential pulse anodic stripping voltammetry (DPASV), electron spin resonance (ESR), and computer speciation calculations (MINEQL+), indicated that the high solubility of Cu and Ni was a result of complexation with dissolved amines or amino acids in the alkaline (pH12) water extracts. Because of the high affinity of both Cu2+ and Ni2+ for N‐ligands in amines, these metals were mobilized much more than Pb, Zn, or Cd. The low solubilities of Ag and Hg may indicate that they were present in the sludge product as the insoluble metallic or sulfide forms. Prolonged exposure of the alkaline extracts to air caused CO2 to gradually lower the solution pH to 8.1 forming a CaCO3 precipitate. However, the dissolved Cu and Ni concentrations did not diminish with pH, indicating that the metal‐organic complexes were sufficiently stable at pH 8.1 to inhibit metal precipitation with the CaCO3. The results suggest potential for the transport of certain heavy metals from land‐applied alkaline sludges into surface waters and shallow groundwater in some situations.
Mercury and Methylmercury in Decomposing Vegetation of a Pristine and Impounded Wetland
Authors: Heyes A. , Moore T. R , Rudd J. W. M.
Published: July 2010

Mass loss, methylmercury (MeHg), and total mercury (T‐Hg) concentrations were measured in sedge, spruce needles, and Sphagnum moss decomposing in a headwater bog and an impounded riparian wetland. No significant differences in the rates of decomposition were apparent for like tissues among sites. Although concentrations of T‐Hg increased in some tissues, T‐Hg mass was lost from most tissues during decomposition. In the reservoir, approximately 75, 50, and 45% of the initial T‐Hg mass was released from the sedge, needles, and moss, respectively, compared to 45, 0, and 40% in the headwater wetland. Therefore, we propose impoundment promotes the release of T‐Hg during decomposition. Concentrations, masses, and percentages of MeHg decreased in all tissue types at the headwater‐dry site and MeHg concentrations increased in all tissue types at the headwater‐wet and impounded sites. At the headwater‐wet site, the mass of MeHg only increased in the moss (500%) and T‐Hg occurring as MeHg averaged 6% in sedge, 1% in needles, and 7% in moss compared to initial values of 4, 0.5, and 1%. At the impounded sites, the amount of MeHg in the needles and moss increased by approximately 700 and 500%, respectively. Also, T‐Hg occurring as MeHg averaged 12% in sedge, 6% in spruce needles, and 17% in moss. We conclude that decomposition of fresh plant tissue under anoxic conditions increases their MeHg mass and impoundment promotes this process. This increase in tissue MeHg mass is most likely the result of in situ methylation of previously accumulated inorganic Hg.