bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Regression Methodology with Low‐Frequency Water Quality Sampling to Estimate Constituent Loads for Ephemeral Watersheds in Texas
Authors: Toor Gurpal S. , Harmel R. Daren , Haggard Brian E. , Schmidt Gerd
Published: August 2008

Water quality regulation and litigation have elevated the awareness and need for quantifying water quality and source contributions in watersheds across the USA. In the present study, the regression method, which is typically applied to large (perennial) rivers, was evaluated in its ability to estimate constituent loads (NO3–N, total N, PO4–P, total P, sediment) on three small (ephemeral) watersheds with different land uses in Texas. Specifically, regression methodology was applied with daily flow data collected with bubbler stage recorders in hydraulic structures and with water quality data collected with four low‐frequency sampling strategies: random, rise and fall, peak, and single stage. Estimated loads were compared with measured loads determined in 2001–2004 with an autosampler and high‐frequency sampling strategies. Although annual rainfall and runoff volumes were relatively consistent within watersheds during the study period, measured annual nutrient and sediment concentrations and loads varied considerably for the cultivated and mixed watersheds but not for the pasture watershed. Likewise, estimated loads were much better for the pasture watershed than the cultivated and mixed landuse watersheds because of more consistent land management and vegetation type in the pasture watershed, which produced stronger correlations between constituent loads and mean daily flow rates. Load estimates for PO4–P were better than for other constituents possibly because PO4–P concentrations were less variable within storm events. Correlations between constituent concentrations and mean daily flow rate were poor and not significant for all watersheds, which is different than typically observed in large rivers. The regression method was quite variable in its ability to accurately estimate annual nutrient loads from the study watersheds; however, constituent load estimates were much more accurate for the combined 3‐yr period. Thus, it is suggested that for small watersheds, regression‐based annual load estimates should be used with caution, whereas long‐term estimates can be much more accurate when multiple years of concentration data are available. The predictive ability of the regression method was similar for all of the low‐frequency sampling strategies studied; therefore, single‐stage or random strategies are recommended for low‐frequency storm sampling on small watersheds because of their simplicity.
Small‐Scale Spatial Variability of Atrazine and Dinoseb Adsorption Parameters in an Alluvial Soil
Authors: Mermoud A. , Martins J. M. F. , Zhang D. , Favre A. C.
Published: August 2008

Soil sorption processes largely control the environmental fate of herbicides. Therefore, accuracy of sorption parameters is crucial for accurate prediction of herbicide mobility in agricultural soils. A combined experimental and statistical study was performed to investigate the small‐scale spatial variability of sorption parameters for atrazine and dinoseb in soils and to establish the number of samples needed to provide a value of the distribution coefficient (Kd) next to the mean, with a given precision. The study explored sorption properties of the two herbicides in subsurface samples collected from four pits distributed along a transect of an alluvial soil; two to four samples were taken at about 30 cm apart at each sampling location. When considering all the data, the distribution coefficients were found to be normally and log‐normally distributed for atrazine and dinoseb, respectively; the CVs were relatively high (close to 50% for dinoseb and 40% for atrazine). When analyzed horizon by horizon, the data revealed distribution coefficients normally distributed for both herbicides, whatever the soil layer, with lower CVs. The Kd values were shown to vary considerably between samples collected at very short distance (a few centimeters), suggesting that taking a single soil sample to determine sorption properties through batch experiments can lead to highly unrepresentative results and to poor sorption/mobility predictions.
Direct and Indirect Hydrological Controls on E. coli Concentration and Loading in Midwestern Streams
Authors: Vidon P. , Tedesco L. P. , Wilson J. , Campbell M. A. , Casey L. R. , Gray Mark
Published: August 2008

This study investigates hydrological controls on E. coli concentration and loading in two artificially drained agricultural watersheds (58 and 23 km2) of the U.S. Midwest. Stream E. coli concentrations are significantly (p < 0.02) lower at base flow than high flow; however, E. coli load is significantly higher at high flow than at low flow (p < 0.001). Although E. coli concentrations are not significantly higher (p = 0.253) in summer/fall (3269 MPN/100 mL) than in the winter/spring (2411 MPN/100 mL), E. coli load is significantly higher (p < 0.05) in winter/spring (346 MPN/day) than in summer/fall season (75 MPN/day). Correlation analysis indicates that discharge and precipitation are the best indicators of E. coli concentration and 7‐d antecedent precipitation (7dP), the best indicator of E. coli loading in the watersheds studied regardless of flow conditions and location. However, E. coli concentration and loading best correlate to 7dP and turbidity at base flow. A spatial dependency is also observed at base flow with E. coli concentration and load correlating better to 7dP in the headwaters and to turbidity in the lower reaches of the watersheds studied. For high flow conditions, E. coli concentration and loading are poorly correlated to most variables, except stream water temperature and 7‐d antecedent discharge. These results are consistent with those reported in the literature and suggest that, at least during base flow conditions, turbidity and 7dP may be usable in artificially drained landscapes of the Midwest to identify potential hot spots of E. coli contamination.
Selection of Plants for Optimization of Vegetative Filter Strips Treating Runoff from Turfgrass
Authors: Smith Katy E. , Putnam Raymond A. , Phaneuf Clifford , Lanza Guy R. , Dhankher Om P. , Clark John M.
Published: August 2008

Runoff from turf environments, such as golf courses, is of increasing concern due to the associated chemical contamination of lakes, reservoirs, rivers, and ground water. Pesticide runoff due to fungicides, herbicides, and insecticides used to maintain golf courses in acceptable playing condition is a particular concern. One possible approach to mitigate such contamination is through the implementation of effective vegetative filter strips (VFS) on golf courses and other recreational turf environments. The objective of the current study was to screen ten aesthetically acceptable plant species for their ability to remove four commonly‐used and degradable pesticides: chlorpyrifos (CP), chlorothalonil (CT), pendimethalin (PE), and propiconazole (PR) from soil in a greenhouse setting, thus providing invaluable information as to the species composition that would be most efficacious for use in VFS surrounding turf environments. Our results revealed that blue flag iris (Iris versicolor) (76% CP, 94% CT, 48% PE, and 33% PR were lost from soil after 3 mo of plant growth), eastern gama grass (Tripsacum dactyloides) (47% CP, 95% CT, 17% PE, and 22% PR were lost from soil after 3 mo of plant growth), and big blue stem (Andropogon gerardii) (52% CP, 91% CT, 19% PE, and 30% PR were lost from soil after 3 mo of plant growth) were excellent candidates for the optimization of VFS as buffer zones abutting turf environments. Blue flag iris was most effective at removing selected pesticides from soil and had the highest aesthetic value of the plants tested.
Watershed Vulnerability Predictions for the Ozarks Using Landscape Models
Authors: Lopez Ricardo D. , Nash Maliha S. , Heggem Daniel T. , Ebert Donald W.
Published: August 2008

Forty‐six broad‐scale landscape metrics derived from commonly used landscape metrics were used to develop potential indicators of total phosphorus (TP) concentration, total ammonia (TA) concentration, and Escherichia coli bacteria count among 244 sub‐watersheds of the Upper White River (Ozark Mountains, USA). Indicator models were developed by correlating field‐based water quality measurements and contemporaneous remote‐sensing–based ecological metrics using partial least squares (PLS) analyses. The TP PLS model resulted in one significant factor explaining 91% of the variability in surface water TP concentrations. Among the 18 contributing landscape model variables for the TP PLS model, the proportions of a sub‐watershed that are barren and in human use were key indicators of water chemistry in the associated sub‐watersheds. The increased presence and reduced fragmentation of forested areas are negatively correlated with TP concentrations in associated sub‐watersheds, particularly within close proximity to rivers and streams. The TA PLS model resulted in one significant factor explaining 93% of the variability in surface water TA concentrations. The eight contributing landscape model variables for the TA PLS model were among the same forest and urban metrics for the TP model, with a similar spatial gradient trend in relationship to distance from streams and rivers within a sub‐watershed. The E. coli PLS model resulted in two significant factors explaining 99.7% of the variability in E. coli cell count. The 17 contributing landscape model variables for the E. coli PLS model were similar to the TP and TA models. The integration of model results demonstrates that forest, riparian, and urban attributes of sub‐watersheds affect all three models. The results provide watershed managers in the Ozark Mountains with a broad‐scale vulnerability prediction tool, focusing on TP, TA, and E. coli, and are being used to prioritize and evaluate monitoring and restoration efforts in the vicinity of the White River, a major tributary to the Mississippi River and Gulf of Mexico.
Nitrogen Leaching from Douglas‐fir Forests after Urea Fertilization
Authors: Flint Cynthia M. , Harrison Rob B. , Strahm Brian D. , Adams A. B.
Published: August 2008

Leaching of nitrogen (N) after forest fertilization has the potential to pollute ground and surface water. The purpose of this study was to quantify N leaching through the primary rooting zone of N‐limited Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] forests the year after fertilization (224 kg N ha−1 as urea) and to calculate changes in the N pools of the overstory trees, understory vegetation, and soil. At six sites on production forests in the Hood Canal watershed, Washington, tension lysimeters and estimates of the soil water flux were used to quantify the mobilization and leaching of NO3–N, NH4–N, and dissolved organic nitrogen below the observed rooting depth. Soil and vegetation samples were collected before fertilization and 1 and 6 mo after fertilization. In the year after fertilization, the total leaching beyond the primary rooting zone in excess of control plots was 4.2 kg N ha−1 (p = 0.03), which was equal to 2% of the total N applied. The peak NO3–N concentration that leached beyond the rooting zone of fertilized plots was 0.2 mg NO3–N L−1 Six months after fertilization, 26% of the applied N was accounted for in the overstory, and 27% was accounted for in the O+A horizon of the soil. The results of this study indicate that forest fertilization can lead to small N leaching fluxes out of the primary rooting zone during the first year after urea application.
New Measurements of Cyanobacterial Toxins in Natural Waters Using High Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry
Authors: Hedman Curtis J. , Krick William R. , Karner Perkins Dawn A. , Harrahy Elisabeth A. , Sonzogni William C.
Published: August 2008

The presence and levels of the cyanobacterial toxins microcystin‐LR, anatoxin‐a, and cylindrospermopsin were measured in various Wisconsin waters where algal nuisance or bloom conditions were noted. Out of 74 samples analyzed, 36 had detectable levels of microcystin‐LR (49%), and four had detectable levels of anatoxin‐a (5%). Cylindrospermopsin, the toxin produced by Cylindrospermopsis (a warm water species that has been moving its range northward, including to Wisconsin), was not detected in the field samples tested. Concentrations of microcystin‐LR ranged from 1.2 to 7600 μg L−1 Anatoxin‐a ranged from 0.68 to 1750 μg L−1, which is the highest concentration reported from around the world. Cyanobacterial toxins, because of their high potency, deserve continued scrutiny by resource managers and public health officials responsible for recreational waters.
Water Quality Trends and Changing Agricultural Practices in a Midwest U.S. Watershed, 1994–2006
Authors: Renwick William H. , Vanni Michael J. , Zhang Qianyi , Patton Jon
Published: August 2008

Sediment and nutrient concentrations in surface water in agricultural regions are strongly influenced by agricultural activities. In the Corn Belt, recent changes in farm management practices are likely to affect water quality, yet there are few data on these linkages at the landscape scale. We report on trends in concentrations of N as ammonium (NH4) and nitrate (NO3), soluble reactive phosphorus (SRP), and suspended sediment (SS) in three Corn Belt streams with drainage areas of 12 to 129 km2 for 1994 through 2006. During this period, there has been an increase in conservation tillage, a decline in fertilizer use, and consolidation of animal feeding operations in our study watersheds and throughout the Corn Belt. We use an autoregressive moving average model to include the effects of discharge and season on concentrations, LOWESS plots, and analyses of changes in the relation between discharge and concentration. We found significant declines in mean monthly concentrations of NH4 at all three streams over the 13‐yr period, declines in SRP and SS in two of the three streams, and a decline in NO3 in one stream. When trend coefficients are converted to percent per year and weighted by drainage, area changes in concentration are −8.5% for NH4, −5.9% for SRP, −6.8% for SS, and −0.8% for NO3 Trends in total N and P are strongly tied to trends in NO3, SRP, and SS and indicate that total P is declining, whereas total N is not.
Potential Negative Consequences of Adding Phosphorus‐Based Fertilizers to Immobilize Lead in Soil
Authors: Kilgour Douglas W. , Moseley Rebecca B. , Barnett Mark O. , Savage Kaye S. , Jardine Philip M.
Published: August 2008

A study of the potential negative consequences of adding phosphate (P)‐based fertilizers as amendments to immobilize lead (Pb) in contaminated soils was conducted. Lead‐contaminated firing range soils also contained elevated concentrations of antimony (Sb), a common Pb hardening agent, and some arsenic (As) of unknown (possibly background) origin. After amending the soils with triple superphosphate, a relatively soluble P source, column leaching experiments revealed elevated concentrations of Sb, As, and Pb in the leachate, reflecting an initial spike in soluble Pb and a particularly dramatic increase in Sb and As mobility. Minimal As, Sb, and Pb leaching was observed during column tests performed on non‐amended control soils. In vitro extractions tests were performed to assess changes in Pb, As, and Sb bioaccessibility on P amendment. Lead bioaccessibility was systematically lowered with increasing P dosage, but there was much less of an effect on As and Sb bioaccessibility than on mobility. Our results indicate that although P amendments may aid in lowering the bioaccessibility of soil‐bound Pb, it may also produce an initial increase in Pb mobility and a significant release of Sb and As from the soil, dramatically increasing their mobility and to a lesser extent their bioavailability.
Farm Factors Associated with Reducing Cryptosporidium Loading in Storm Runoff from Dairies
Authors: Miller W. A. , Lewis D. J. , Pereira M. D. G. , Lennox M. , Conrad P. A. , Tate K. W. , Atwill E. R.
Published: August 2008

A systems approach was used to evaluate environmental loading of Cryptosporidium oocysts on five coastal dairies in California. One aspect of the study was to determine Cryptosporidium oocyst concentrations and loads for 350 storm runoff samples from dairy high use areas collected over two storm seasons. Selected farm factors and beneficial management practices (BMPs) associated with reducing the Cryptosporidium load in storm runoff were assessed. Using immunomagnetic separation (IMS) with direct fluorescent antibody (DFA) analysis, Cryptosporidium oocysts were detected on four of the five farms and in 21% of storm runoff samples overall. Oocysts were detected in 59% of runoff samples collected near cattle less than 2 mo old, while 10% of runoff samples collected near cattle over 6 mo old were positive. Factors associated with environmental loading of Cryptosporidium oocysts included cattle age class, 24 h precipitation, and cumulative seasonal precipitation, but not percent slope, lot acreage, cattle stocking number, or cattle density. Vegetated buffer strips and straw mulch application significantly reduced the protozoal concentrations and loads in storm runoff, while cattle exclusion and removal of manure did not. The study findings suggest that BMPs such as vegetated buffer strips and straw mulch application, especially when placed near calf areas, will reduce environmental loading of fecal protozoa and improve stormwater quality. These findings are assisting working dairies in their efforts to improve farm and ecosystem health along the California coast.
Major Factors Influencing the Efficacy of Vegetated Buffers on Sediment Trapping: A Review and Analysis
Authors: Liu Xingmei , Zhang Xuyang , Zhang Minghua
Published: August 2008

Sediment is a major agricultural pollutant threatening water quality. Vegetated buffers, including vegetative filter strips, riparian buffers, and grassed waterways, are best management practices (BMPs) installed in many areas to filter sediments from tailwaters, and deter sediment transport to water bodies. Along with reducing sediment transport, the filters also help trap sediment bound nutrients and pesticides. The objectives of this study were: (i) to review vegetated buffer efficacy on sediment trapping, and (ii) to develop statistical models to investigate the major factors influencing sediment trapping. A range of sediment trapping efficacies was found in a review of over 80 representative BMP experiments. A synthesis of the literature regarding the effects of vegetated buffers on sediment trapping is needed. The meta‐analysis results based on the limited data showed that buffer width and slope are two major factors influencing BMPs efficacy of vegetated buffers on sediment trapping. Regardless of the area ratio of buffer to agricultural field, a 10 m buffer and a 9% slope optimized the sediment trapping capability of vegetated buffers.
Revisiting a Statistical Shortcoming when Fitting the Langmuir Model to Sorption Data
Authors: Bolster Carl H.
Published: August 2008

The Langmuir model is commonly used for describing the sorption behavior of reactive solutes to surfaces and is often fit to sorption data using nonlinear least squares regression. An important assumption of least squares regression is that the predictor variable is error free. In the case of sorption data, this assumption is not valid, and therefore the potential for parameter bias exists. Although alternative regression methods exist that either explicitly account for error in the predictor variable (Model II regression) or minimize the error in the predictor variable, these methods are not commonly used. Therefore, this paper more fully explores the differences in fitted parameters and model fits between these different data fitting methods by fitting P sorption data collected on 26 different soil samples using three different regression methods. For a majority of soils tested in this study, the differences in model fits between the three regression methods were not statistically significant. Statistical differences were observed in over a third of the soils, however, suggesting that errors in the predictor variable may be large enough to produce biased parameter estimates. These results suggest that multiple regression methods should be used when fitting the Langmuir model to sorption data to better assess the potential impact of error on model fits.
Transport of Particulate Matter Fractions in Urban Source Area Pavement Surface Runoff
Authors: Sansalone John J. , Kim Jong‐Yeop
Published: August 2008

This study used manual full cross‐sectional flow discrete sampling and suspended sediment concentration (SSC) methods to gravimetrically characterize noncolloidal hetero‐disperse particulate matter (PM). This PM was examined as suspended, settleable, and sediment fractions to assess the distinct transport behavior of each PM fraction throughout each runoff event. Eight runoff events loading an urban paved source area watershed were examined to characterize transport of PM (as SSC) and fractions thereof. An event‐based PM mass balance demonstrated recoveries exceeding 90%. With respect to PM transport, two phases were differentiated using a first flush index (m = ΔM/ΔV) developed in this study. The m ≥ 1 and m < 1 transport phases of the coarser settleable/sediment PM accounted for a higher mass fraction of PM transported during higher flow rates, whereas delivery of the finer suspended fraction became more significant at lower flows. A positive relationship between PM concentration and particle size distribution was found for all events. Event mean concentrations (EMCs) of PM (as SSC) were compared with literature EMCs, sampling methods, and PM analysis method (as total suspended solids [TSS]). Particulate matter study results (as SSC) were higher than many published EMCs (as TSS) (p < 0.05). Differences are attributed to full cross‐sectional flow sampling and the use of the the SSC method in contrast to automated sampling combined with TSS methods. Representative characterization of hetero‐disperse source area PM is important for water chemistry monitoring, regulatory decisions, best management practice performance and maintenance, and PM inventories in urban systems.
Modeling Effluent Distribution and Nitrate Transport through an On‐Site Wastewater System
Authors: Hassan G. , Reneau R. B. , Hagedorn C. , Jantrania A. R.
Published: August 2008

Properly functioning on‐site wastewater systems (OWS) are an integral component of the wastewater system infrastructure necessary to renovate wastewater before it reaches surface or ground waters. There are a large number of factors, including soil hydraulic properties, effluent quality and dispersal, and system design, that affect OWS function. The ability to evaluate these factors using a simulation model would improve the capability to determine the impact of wastewater application on the subsurface soil environment. An existing subsurface drip irrigation system (SDIS) dosed with sequential batch reactor effluent (SBRE) was used in this study. This system has the potential to solve soil and site problems that limit OWS and to reduce the potential for environmental degradation. Soil water potentials (Ψs) and nitrate (NO3) migration were simulated at 55‐ and 120‐cm depths within and downslope of the SDIS using a two‐dimensional code in HYDRUS‐3D. Results show that the average measured Ψs were −121 and −319 cm, whereas simulated values were −121 and −322 cm at 55‐ and 120‐cm depths, respectively, indicating unsaturated conditions. Average measured NO3 concentrations were 0.248 and 0.176 mmol N L−1, whereas simulated values were 0.237 and 0.152 mmol N L−1 at 55‐ and 120‐cm depths, respectively. Observed unsaturated conditions decreased the potential for NO3 to migrate in more concentrated plumes away from the SDIS. The agreement (high R2 values ≈0.97) between the measured and simulated Ψs and NO3 concentrations indicate that HYDRUS‐3D adequately simulated SBRE flow and NO3 transport through the soil domain under a range of environmental and effluent application conditions.
Passive Treatment of Acid Mine Drainage with High Metal Concentrations Using Dispersed Alkaline Substrate
Authors: Rötting Tobias S. , Thomas Robert C. , Ayora Carlos , Carrera Jesús
Published: August 2008

Passive treatment systems based on the dissolution of coarse calcite grains are widely used to remediate acid mine drainage (AMD). Unfortunately, they tolerate only low metal concentrations or acidity loads, because they are prone to passivation (loss of reactivity due to coating) and/or clogging (loss of permeability) by precipitates. To overcome these problems, a dispersed alkaline substrate (DAS) composed of a fine‐grained alkaline reagent (calcite sand) mixed with a coarse inert matrix (wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate, whereas the dispersion of nuclei for precipitation on the inert surfaces retards clogging. Chemical and hydraulic performance of DAS was investigated in two laboratory columns fed at different flow rates with natural AMD of pH 2.3 to 3.5 and inflow net acidity 1350 to 2300 mg/L as CaCO3 The DAS columns removed 900 to 1600 mg/L net acidity, 3 to 4.5 times more than conventional passive treatment systems. Regardless of the flow rate employed, Al, Fe(III), Cu, and Pb were virtually eliminated. Minor Zn, Ni, and Cd were removed at low flow rates. High acidity removal is possible because these metals accumulate intentionally in DAS, and their precipitation promotes further calcite dissolution. During 15 mo, DAS operated without clogging at 120 g acidity/m2·d, four times the loading rate recommended for conventional passive systems; DAS may therefore be capable of treating AMD at sites where influent chemistry precludes the use of other passive systems.
Combined Monitoring and Modeling Indicate the Most Effective Agricultural Best Management Practices
Authors: Easton Zachary M. , Walter M. Todd , Steenhuis Tammo S.
Published: August 2008

Although water quality problems associated with agricultural nonpoint source (NPS) pollution have prompted the rapid and widespread adoption of a variety of so called “best management practices” (BMPs), there have been few realistic efforts to assess their combined effectiveness in reducing NPS pollution. This study used the Variable Source Loading Function (VSLF) model, a distributed watershed model, to simulate phosphorus (P) loading from an upstate New York dairy farm before and after the implementation of a suite of BMPs. With minimal calibration, the model calculates the dissolved P (DP) losses from impervious surfaces (e.g., barnyards), the plant/soil complex, field‐applied manure, and loads associated with baseflow conditions. The simulated DP loads agreed well with measured loads for both the pre‐BMP and post‐BMP periods. More importantly, results showed that BMPs reduced DP loads by 35%, which is over half of the expected reduction if all manure was removed from the watershed, i.e., ∼50% reduction. The model results indicate that had no BMPs been installed DP loads would be ∼37% greater than observed at the watershed outlet. The most effective BMPs were those that disassociated pollutant loading areas from areas prone to generating runoff, i.e., hydrologically sensitive areas. By contrast, attempts to reduce P content in manure were somewhat less effective. This study demonstrates that a combination of distributed, mechanistic modeling and long‐term monitoring provides better insights into the effectiveness of water quality protection efforts than either individually.
Evaluating Long‐Term Nitrogen‐ versus Phosphorus‐Based Nutrient Management of Poultry Litter
Authors: Maguire Rory O. , Mullins Greg L. , Brosius Mike
Published: August 2008

Environmental concerns are driving manure management in many areas from a traditional nitrogen (N) basis toward phosphorus (P)‐based nutrient management plans. We investigated how changing nutrient management from an N to a P basis affected crop yields and soil properties in high P soils over a 7‐yr period. Three sites were established on farmers' fields, and at each site the same six treatments were applied for 6 or 7 yr. These treatments were (i) no P; (ii) poultry litter applied on an N basis; (iii) inorganic P, equal to the P applied in treatment 2; (iv) poultry litter applied on an estimated annual crop P removal basis; (v) inorganic P, equal to the P applied in treatment iv; and (vi) poultry litter applied once every 2 or 3 yr at a 2‐ or 3‐yr crop removal P rate. All treatments received the same rate of plant‐available N. Yields, P balance, soil pH, Mehlich 1 P, and water‐soluble P (WSP) were monitored during the experiment. Over the course of the experiment, litter had the beneficial effect of raising soil pH relative to the inorganic treatments. After 7 yr, Mehlich 1 P and WSP were greatest in soils under the N‐based treatments, smallest in the no P treatment, and intermediate in the P‐based treatments. For example, at the Shenandoah site, Mehlich 1 P decreased by 35 mg kg−1 under the no P treatment and increased by 36 mg kg−1 under the inorganic N‐based treatment. There were no significant differences between inorganic fertilizer and poultry litter nutrient sources. The results of this study show that soil test P can be decreased in high‐P soils over a few years by changing from an N‐based to a P‐based nutrient management plan or stopping P applications without negatively affecting yields.
Thirty‐Year Trends in Suspended Sediment in Seven Lake Erie Tributaries
Authors: Richards R. Peter , Baker David B. , Crumrine John P. , Kramer Jack W. , Ewing D. Ellen , Merryfield Barbara J.
Published: August 2008

Sediment is an important pollutant for Lake Erie and its tributaries as a carrier of other substances and as a pollutant in its own right. Environmental managers have called for major reductions in sediment loadings in Lake Erie tributaries. In this study, 30‐yr (1975–2005) datasets with daily resolution are analyzed to identify and interpret trends in sediment concentrations and loads in major US tributaries to Lake Erie. The Maumee and Sandusky Rivers in agricultural northwest Ohio show continual decreases throughout this period, but the River Raisin shows increases, especially in the last decade. The urban and forested Cuyahoga River shows little trend before 2000 but shows increases since then. The mostly forested Grand River shows strong decreases before 1995, little change thereafter until the early 2000s, and then increases. In most cases, the greatest decreases or smallest increases, depending on the river, are associated with summer and fall and with low flow conditions, whereas the smallest decreases or greatest increases are associated with the spring and with high flow conditions. Analysis of concentration–flow relationships indicates that these changes are not due to weather but reflect positive and negative anthropogenic influences. Sediment decreases in the northwestern Ohio tributaries seem to reflect the successful use of agricultural practices to reduce erosion and prevent sediment loss. Opportunities for further reductions in sediment loads and concentrations lie in better management of sediment losses during winter and spring.
Co‐digestion of Animal Slurry Can Increase Short‐Term Nitrogen Recovery by Crops
Authors: de Boer H. C.
Published: August 2008

Co‐digestion changes slurry characteristics and is supposed to increase short‐term nitrogen (N) uptake by crops after application. A higher N uptake from slurry reduces the need for additional mineral N fertilizer. If farmers apply co‐digested slurry (CS), a higher N recovery has to be taken into account to prevent losses to the environment. Since data on the effects of co‐digestion on N recovery by crops are scarce, a pot experiment was performed. The apparent N recovery (ANR) of five different co‐digested pig slurries was compared with their raw source slurries (RS) during 105 d after a single fertilization of ryegrass (Lolium perenne L.), grown under controlled conditions. Slurry was mixed with sandy soil and grass was cut every 35 d. The results show that co‐digestion increased (p < 0.05) the ANR at first cut on average from 39 to 50%, at second cut from 7 to 9% (p < 0.05), and had no effect on ANR at third cut (3%). The ANR increase at first cut was likely due to an increase of the NH4–N/total N ratio along with a decrease of the organic C/total N ratio of slurry during co‐digestion. Field application may under certain circumstances decrease N fertilizer value of CS, due to a higher NH3 emission compared to RS. A potential ANR increase may then be reduced, absent, or even become a decrease. Under comparable NH3 emissions, however, CS can in the short term be more valuable as an N fertilizer than RS, and fertilizer savings can likely be realized.
Biological Alkylation and Colloid Formation of Selenium in Methanogenic UASB Reactors
Authors: Lenz Markus , Smit Martijn , Binder Patrick , van Aelst Adriaan C. , Lens Piet N. L.
Published: August 2008

Bioalkylation and colloid formation of selenium during selenate removal in upflow anaerobic sludge bed (UASB) bioreactors was investigated. The mesophilic (30°C) UASB reactor (pH = 7.0) was operated for 175 d with lactate as electron donor at an organic loading rate of 2 g COD L−1 d−1 and a selenium loading rate of 3.16 mg Se L−1 d−1 Combining sequential filtration with ion chromatographic analysis for selenium oxyanions and solid phase micro extraction gas chromatography mass spectrometry (SPME‐GC–MS) for alkylated selenium compounds allowed to entirely close the selenium mass balance in the liquid phase for most of the UASB operational runtime. Although selenate was removed to more than 98.6% from the liquid phase, a less efficient removal of dissolved selenium was observed due to the presence of dissolved alkylated selenium species (dimethylselenide and dimethyldiselenide) and colloidal selenium particles in the effluent. The alkylated and the colloidal fractions contributed up to 15 and 31%, respectively, to the dissolved selenium concentration. The size fractions of the colloidal dispersion were: 4 to 0.45 μm: up to 21%, 0.45 to 0.2 μm: up to 11%, and particles smaller than 0.2 μm: up to 8%. Particles of 4 to 0.45 μm were formed in the external settler, but did not settle. SEM‐EDX analysis showed that microorganisms form these selenium containing colloidal particles extracellularly on their surface. Lowering the temperature by 10°C for 6 h resulted in drastically reduced selenate removal efficiencies (after a delay of 1.5 d), accompanied by the temporary formation of an unknown, soluble, organic selenium species. This study shows that a careful process control is a prerequisite for selenium treatment in UASB bioreactors, as disturbances in the operational conditions induce elevated selenium effluent concentrations by alkylation and colloid formation.
Landfill Cover Soil, Soil Solution, and Vegetation Responses to Municipal Landfill Leachate Applications
Authors: MacDonald Neil W. , Rediske Richard R. , Scull Brian T. , Wierzbicki David
Published: August 2008

Municipal solid waste landfill leachate must be removed and treated to maintain landfill cover integrity and to prevent contamination of surface and ground waters. From 2003 to 2007, we studied an onsite disposal system in Ottawa County, Michigan, where leachate was spray irrigated on the vegetated landfill cover. We established six 20‐m‐diameter circular experimental plots on the landfill; three were spray irrigated as part of the operational system, and three remained as untreated control plots. We quantified the effects of leachate application on soil properties, soil solution chemistry, vegetative growth, and estimated solute leaching. The leachate had high mean levels of electrical conductivity (0.6–0.7 S m−1), Cl (760–900 mg L−1), and NH4–N (290–390 mg L−1) but was low in metals and volatile organic compounds. High rates of leachate application in 2003 (32 cm) increased soil electrical conductivity and NO3–N leaching, so a sequential rotation of spray areas was implemented to limit total leachate application to <9.6 cm yr−1per spray area. Concentrations of NO3–N and leaching losses remained higher on irrigated plots in subsequent years but were substantially reduced by spray area rotation. Leachate irrigation increased plant biomass but did not significantly affect soil metal concentrations, and plant metal concentrations remained within normal ranges. Rotating spray areas and timing irrigation to conform to seasonal capacities for evapotranspiration reduced the localized impacts of leachate application observed in 2003. Careful monitoring of undiluted leachate applications is required to avoid adverse impacts to vegetation or soils and elevated solute leaching losses.
Targeting CD22 Reprograms B-Cells and Reverses Autoimmune Diabetes
Authors: Fiorina Paolo , Vergani Andrea , Dada Shirine , Jurewicz Mollie , Wong Masie , Law Kenneth , Wu Erxi , Tian Ze , Abdi Reza , Guleria Indira , Rodig Scott , Dunussi-Joannopoulos Kyri , Bluestone Jeffrey , Sayegh Mohamed H.
Published: August 2008

OBJECTIVES—To investigate a B-cell–depleting strategy to reverse diabetes in naïve NOD mice.

RESEARCH DESIGN AND METHODS—We targeted the CD22 receptor on B-cells of naïve NOD mice to deplete and reprogram B-cells to effectively reverse autoimmune diabetes.

RESULTS—Anti-CD22/cal monoclonal antibody (mAb) therapy resulted in early and prolonged B-cell depletion and delayed disease in pre-diabetic mice. Importantly, when new-onset hyperglycemic mice were treated with the anti-CD22/cal mAb, 100% of B-cell–depleted mice became normoglycemic by 2 days, and 70% of them maintained a state of long-term normoglycemia. Early therapy after onset of hyperglycemia and complete B-cell depletion are essential for optimal efficacy. Treated mice showed an increase in percentage of regulatory T-cells in islets and pancreatic lymph nodes and a diminished immune response to islet peptides in vitro. Transcriptome analysis of reemerging B-cells showed significant changes of a set of proinflammatory genes. Functionally, reemerging B-cells failed to present autoantigen and prevented diabetes when cotransferred with autoreactive CD4+ T-cells into NOD.SCID hosts.

CONCLUSIONS—Targeting CD22 depletes and reprograms B-cells and reverses autoimmune diabetes, thereby providing a blueprint for development of novel therapies to cure autoimmune diabetes.
Transforming Growth Factor-β Suppresses the Activation of CD8+ T-Cells When Naïve but Promotes Their Survival and Function Once Antigen Experienced
Authors: Filippi Christophe M. , Juedes Amy E. , Oldham Janine E. , Ling Ellie , Togher Lisa , Peng Yufeng , Flavell Richard A. , von Herrath Matthias G.
Published: August 2008

OBJECTIVE—Transforming growth factor-β (TGF-β) can exhibit strong immune suppression but has also been shown to promote T-cell growth. We investigated the differential effect of this cytokine on CD8+ T-cells in autoimmunity and antiviral immunity.

RESEARCH DESIGN AND METHODS—We used mouse models for virally induced type 1 diabetes in conjunction with transgenic systems enabling manipulation of TGF-β expression or signaling in vivo.

RESULTS—Surprisingly, when expressed selectively in the pancreas, TGF-β reduced apoptosis of differentiated autoreactive CD8+ T-cells, favoring their expansion and infiltration of the islets. These results pointed to drastically opposite roles of TGF-β on naïve compared with antigen-experienced/memory CD8+ T-cells. Indeed, in the absence of functional TGF-β signaling in T-cells, fast-onset type 1 diabetes caused by activation of naïve CD8+ T-cells occurred faster, whereas slow-onset disease depending on accumulation and activation of antigen-experienced/memory CD8+ T-cells was decreased. TGF-β receptor–deficient CD8+ T-cells showed enhanced activation and expansion after lymphocytic choriomeningitis virus infection in vivo but were more prone to apoptosis once antigen experienced and failed to survive as functional memory cells. In vitro, TGF-β suppressed naïve CD8+ T-cell activation and γ-interferon production, whereas memory CD8+ T-cells stimulated in the presence of TGF-β showed enhanced survival and increased production of interleukin-17 in conjunction with γ-interferon.

CONCLUSIONS—The effect of TGF-β on CD8+ T-cells is dependent on their differentiation status and activation history. These results highlight a novel aspect of the pleiotropic nature of TGF-β and have implications for the design of immune therapies involving this cytokine.
Predicting Diabetes: Clinical, Biological, and Genetic Approaches
Authors: Balkau Beverley , Lange Céline , Fezeu Leopold , Tichet Jean , de Lauzon-Guillain Blandine , Czernichow Sebastien , Fumeron Frederic , Froguel Philippe , Vaxillaire Martine , Cauchi Stephane , Ducimetière Pierre , Eschwège Eveline
Published: August 2008

OBJECTIVE—To provide a simple clinical diabetes risk score and to identify characteristics that predict later diabetes using variables available in the clinic setting as well as biological variables and polymorphisms.

RESEARCH DESIGN AND METHODS—Incident diabetes was studied in 1,863 men and 1,954 women, 30–65 years of age at baseline, with diabetes defined by treatment or by fasting plasma glucose ≥7.0 mmol/l at 3-yearly examinations over 9 years. Sex-specific logistic regression equations were used to select variables for prediction.

RESULTS—A total of 140 men and 63 women developed diabetes. The predictive clinical variables were waist circumference and hypertension in both sexes, smoking in men, and diabetes in the family in women. Discrimination, as measured by the area under the receiver operating curves (AROCs), were 0.713 for men and 0.827 for women, a little higher than for the Finish Diabetes Risk (FINDRISC) score, with fewer variables in the score. Combining clinical and biological variables, the predictive equation included fasting glucose, waist circumference, smoking, and γ-glutamyltransferase for men and fasting glucose, BMI, triglycerides, and diabetes in family for women. The number of TCF7L2 and IL6 deleterious alleles was predictive in both sexes, but after including the above clinical and biological variables, this variable was only predictive in women (P < 0.03) and the AROC statistics increased only marginally.

CONCLUSIONS—The best clinical predictor of diabetes is adiposity, and baseline glucose is the best biological predictor. Clinical and biological predictors differed marginally between men and women. The genetic polymorphisms added little to the prediction of diabetes.
Barriers to Physical Activity Among Patients With Type 1 Diabetes
Authors: Brazeau Anne-Sophie , Rabasa-Lhoret Rémi , Strychar Irene , Mircescu Hortensia
Published: August 2008

OBJECTIVE—To determine, in an adult population with type 1 diabetes, barriers to regular physical activity using a diabetes-specific barriers measure (the Barriers to Physical Activity in Diabetes [type 1] [BAPAD1] scale) and factors associated with these barriers.

RESEARCH DESIGN AND METHODS—One hundred adults with type 1 diabetes answered a questionnaire assessing perceived barriers to physical activity and related factors. A1C was obtained from the medical chart of each individual.

RESULTS—Fear of hypoglycemia was identified as being the strongest barrier to physical activity. Greater knowledge about insulin pharmacokinetics and using appropriate approaches to minimize exercise-induced hypoglycemia were factors associated with fewer perceived barriers. Greater barriers were positively correlated with A1C levels (r = 0.203; P = 0.042) and negatively with well-being (r = −0.45; P < 0.001).

CONCLUSIONS—Fear of hypoglycemia is the strongest barrier to regular physical activity in adults with type 1 diabetes, who should therefore be informed and supported in hypoglycemia management.
Dietary Energy Density Predicts the Risk of Incident Type 2 Diabetes
Authors: Wang Jing , Luben Robert , Khaw Kay-Tee , Bingham Sheila , Wareham Nicholas J. , Forouhi Nita G.
Published: August 2008

OBJECTIVE—Accumulating evidence suggests that energy-dense foods predispose to obesity and that such foods may also be associated with an increased risk of type 2 diabetes, but there is limited evidence. Our aim was to investigate whether there is an independent association between dietary energy density and incidence of diabetes.

RESEARCH DESIGN AND METHODS—The European Prospective Investigation of Cancer (EPIC)-Norfolk Cohort Study was a population-based prospective study of individuals aged 40–79 years at baseline. We calculated energy density for overall diet (all solids and drinks) using food frequency questionnaires. During 12 years of follow-up, we documented 725 new-onset cases of diabetes among 21,919 participants without diabetes, cancer, or cardiovascular disease at baseline.

RESULTS—Baseline energy density (adjusted for age, sex, and baseline BMI) was higher in those who developed type 2 diabetes (mean 3.08 kJ/g [95% CI 3.03–3.13]) than in those who remained nondiabetic (3.01 kJ/g [3.00–3.02]) (P = 0.012). Energy density was positively associated with incident diabetes (odds ratio 1.21 per unit increase [95% CI 1.06–1.38]) adjusted for known risk factors. There was a 60% higher risk of diabetes (1.60 [1.19–2.16]) in the highest quintile of energy density (range 3.55–7.97 kJ/g) compared with the lowest quintile (1.04–2.43 kJ/g) in adjusted analysis.

CONCLUSIONS—This is the first large population-based prospective study to report that an energy-dense diet may be associated with increased risk of development of diabetes, independent of baseline obesity. The potential public health impact of a low–energy-dense diet on reducing the risk of diabetes deserves further study.
Exhibition of persistent and drug-tolerant L-form habit of Mycobacterium tuberculosis during infection in rats
Authors: Markova Nadya , Michailova Lilia , Jourdanova Mimi , Kussovski Vesselin , Valcheva Violeta , Mokrousov Igor , Radoucheva Tatyana
Published: August 2008

A model for studying mycobacterial L-form formation in vivo was established to demonstrate the ability of M. tuberculosis to behave as a drug-tolerant L-form persister. Rats were infected by intranasal (i.n.) and intraperitoneal (i.p.) routes with 1×108 cells/ml of M. tuberculosis. At weekly intervals during a period of five weeks, samples from lung, spleen, liver, kidney, mesenterial and inguinal lymph nodes, broncho-alveolar and peritoneal lavage liquid were plated simultaneously on Löwenstein-Jensen (LJ) medium or inoculated into specially supplemented for L-forms Dubos broth (drug-free and drug-containing variants). The use of liquid media enabled isolation of mycobacterial L-form cultures during the whole period of experiment including the last two weeks, when tubercle bacilli were not isolated on LJ medium. An unique feature of mycobacterial L-forms was their ability to grow faster than the classical tubercle bacilli. Isolation and growth of L-form cultures in primary drug-containing media demonstrated their drug-tolerant properties. Electron microscopy of liquid media isolates showed that they consisted of morphologically heterogenous populations of membrane-bound and of variable sized L-bodies that completely lack cell walls. The identity of the isolated non-acid fast and morphologically modified L-forms as M. tuberculosis was verified by specific spoligotyping test. The results contribute to special aspects concerning the importance of mycobacterial L-form phenomenon for persistence and latency in tuberculosis, phenotypic drug tolerance, as well as for diagnosis of difficult to identify morphologically changed tubercle bacilli which are often mistaken for contaminants.