bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Method To Predict Performance of Horizontal and Multilateral Wells
Authors: Tabatabaei M.. , Ghalambor A..
Published: October 2010

Production enhancement and ultimate recovery improvement have given horizontal wells the edge over vertical wells in many marginal reservoirs. However, it is more expensive to drill and complete a horizontal well than a vertical one. Therefore, to determine the economical feasibility of drilling a horizontal well, engineers need reliable methods to estimate its productivity.

After a broad literature review, a simple semianalytical model has been developed in this study for predicting the productivity of horizontal oil wells. This model couples flow from a box-shaped drainage volume to flow in the wellbore. Along with friction, acceleration, and fluid-inflow effect, change in flow regime from laminar to turbulent is also taken into account to describe flow in the wellbore. The reservoir-inflow model used in this productivity model represents flow in the reservoir using a combination of 1D and 2D models and also considers varying skin along the wellbore to account for the heterogeneity of the near-wellbore region because of drilling-fluid invasion into the formation. In addition, reservoir-permeability anisotropy and convergence of flow to the wellbore have been taken into account in this inflow model. Comparison of this model with three existing models using field data reveals that the proposed model is more accurate because of more-realistic modeling of reservoir inflow and wellbore flow.

The semianalytical nature of this coupling model makes it comprehensive and applicable to reservoirs with varying conditions, especially heterogeneous reservoirs. Moreover, this productivity model can be extended easily to estimate the deliverability of multilateral wells by coupling the inflow performance of individual laterals with hydraulics in buildup sections and the main vertical section. A logical procedure for calculating the deliverability of multilateral wells by using this productivity model is described in this paper.
Inhibition of Calcium Sulfate and Strontium Sulfate Scale in Waterflood
Authors: BinMerdhah Amer Badr
Published: October 2010

One of the most common methods of preventing downhole and topside mineral-scale formation in oil fields is through the use of chemical-scale inhibitors. Several aspects of the brine composition may affect the performance of the various scale inhibitors used in oilfield applications. This study was conducted to investigate the permeability reduction caused by deposition of calcium sulfate (CaSO4) and strontium sulfate (SrSO4) in Malaysian sandstone and Berea cores from mixing injected Malaysian seawaters (SW) (Angsi and Barton) and formation water (FW) that contain a high concentration of calcium and strontium ions at various temperatures (50 to 95°C) and differential pressures (75 to 200 psig). Scale-inhibition efficiency was determined in both the bulk jar and the core tests by using scale inhibitors methylene phosphonic acid (DETPMP), polyphosphino carboxylic acid (PPCA), and phosphorus-based scale inhibitor (PBSI) at various temperatures (50 to 95°C) and concentrations. The results showed a large extent of permeability damage caused by calcium and strontium sulfates that deposited on the rock pore surface. At higher temperatures, the rate of CaSO4 and SrSO4 precipitation increases because the solubilities of CaSO4 and SrSO4 scales decrease with increasing temperature. At 90°C temperature, PBSI was the best inhibitor because it reduced more scale deposition compared to the DETPMP and PPCA inhibitors.
A Mathematical Improvement to SAGD Using Geomechanical Modelling
Authors: Azad A. , Chalaturnyk R.J.
Published: October 2010

Steam assisted gravity drainage (SAGD) is a thermal oil recovery technique which has been used mostly for Alberta's unconventional oil sands reservoirs. Roger Butler, known as the father of SAGD, was the first one to establish a theory and an analytical model for SAGD. His model is a rigorous solution and is widely referred to as a SAGD fast flow simulator. However, geomechanics, which has been shown to be a relevant part of SAGD's physics, has not been included in the model. When rock properties are influenced by geomechanical behaviour, the Butler theory is not able to capture the complete physics of the SAGD process. In such cases, the model must adopt unrealistic or high values for rock properties.

In this study, a classical theory in the field of geotechnical engineering (limit equilibrium) is employed to act as the geomechanical module for SAGD's mathematical coupled simulation. The Butler/Reis model has also been improved using a model of slices for flow simulation. Methodology of combining these two models in a single coupled mathematical simulator is presented in this paper. The solver is a fast and realistic proxy and can be used as a low-order tool for history matching. The results of coupled simulations show that the model is able to predict permeability and porosity of the reservoir closer to real values than uncoupled (flow only) modelling.
Calculation of Permeability Tensors for Unstructured Gridblocks
Authors: Hassanpour R.M. , Manchuk J.G. , Leuangthong O. , Deutsch C.V.
Published: October 2010

Geostatistical models of reservoir properties are high resolution with many grid cells; it is impractical to use them directly in flow simulation because of computational costs. Upscaling techniques are applied to average small-scale permeability values to larger flow simulation blocks. In cases where unstructured grids are used or the geological features inside the gridblock are not aligned with the block geometry, symmetric or full-permeability tensors arise instead of a simple diagonal tensor. A method is presented to calculate the permeability tensor for an unstructured gridblock to account for the small-scale heterogeneity information inside the gridblock. Single-phase flow-based upscaling is performed based on random boundary conditions and the effective tensor permeability is found through an optimization technique. Full, symmetric and diagonal permeability tensors are calculated for 2D and 3D blocks and sensitivity analysis is performed.
A 3D Analytical Model for Wellbore Friction
Authors: Aadnoy Bernt S. , Fazaelizadeh Mohammad , Hareland Geir
Published: October 2010

This paper presents a new friction model for application in petroleum wells. Although very simple, it applies for all wellbore shapes such as straight sections, drop-off bends, build-up bends, side bends or a combination of these. The drillstring is modelled as a soft string. In high tension the string weight is negligible as compared to the tension. This leads to simplified equations where the friction caused by the weight is negligible. For this case the friction in a bend is formulated in terms of the 3D dogleg. The same model therefore applies for 2D and 3D wellbores.

The entire well can be modelled by two sets of equations, one for straight wellbore sections and one for curved wellbores. The latter is based on the absolute directional change, or the dogleg of the wellbore.

Three worked examples are given in the paper: a 2D well, a 3D well and combined hoisting and rotation in the 3D well.

One main purpose of this paper is to provide a simple explicit tool to model and to study friction throughout the well by separating gravitational and tensional friction effects.
Improved Drilling Efficiency Technique Using Integrated PDM and PDC Bit Parameters
Authors: Motahhari H.R. , Hareland G. , James J.A.
Published: October 2010

In this paper, a new drilling optimization procedure is presented that is designed to improve the drilling efficiency with positive displacement motors (PDMs) and PDC bits. This developed optimization method is based on predicting rate of penetration (ROP) from PDM outputs for any PDC bit design. More specifically, optimization is done for a hole section and optimum values of weight on bit (WOB) and surface RPM are obtained for the section. For given flow rates, estimated values of optimum WOB and surface RPM are used to calculate the corresponding motor differential pressures and the foot by foot ROP values. Also, the method is used to show how improper operational parameter selection can affect total drilling time. A case study was done to consider different PDMs with different lobe configurations and a set of fixed operational parameters.

The presented method is verified by generating a confined rock strength log based on drilling data for a previously drilled well in Alberta. This foot-by-foot strength log is compared to a confined rock strength log generated as a follow-up analysis by a commercially available drilling simulator package. Also, a PDM differential pressure log is generated and compared to field-recorded on-bottom differential pressure values.

The method's application is best demonstrated by simulating the drilling operation of the Alberta well with three different PDMs. It is shown that consideration of PDM performance/selection in the drilling planning phase will help to perform a safe and cost-effective operation by preventing motor stalls and maintaining highest average ROP for the section. It is also shown that by optimizing WOB and surface RPM values for a constant mud flow rate and predefined bit wear at total depth, a maximum average ROP for the section can be reached for any PDM.
Experimental Study of Stability and Integrity of Cement in Wellbores Used for CO2 Storage
Authors: Tarco Jose C. , Asghari Karoosh
Published: October 2010

This paper examines the results obtained from several sets of experimental work conducted on cement deterioration in environments similar to those found in CO2 injection and storage projects.

In order to investigate various changes in macroscopic and microscopic properties and behaviour of cement in presence of sulphate ions and CO2, several sets of experiments were conducted.

The study consisted of preparing and investigating the behaviour of several hundred samples of cement in presence of various concentrations of sulphate, from 0.1 wt% up to 6%, as well as CO2  at 15160 kPa and 55ºC. The effect of sulphate ions on cement was studied at 30ºC, 55ºC and 75º C. The two common classes of cement of Type 10 and Class G were tested during this study. A total of 300 identical cubic and 400 identical cylindrical samples were tested. The change in permeability, compressive strength, and shear and hydraulic bonding strength for these samples were monitored after 2, 4, 6, 8, 10 and 12 months.

Laboratory results showed that sulphate ions and CO2 improve the performance of cement during the first few months. However, the effect is reversed under prolonged experiments. The highest reduction in performance was observed for hydraulic shear bonding, which indicates that the highest risk of CO2 leakage is through pathways between the cement and casing.
Scaling Analysis of Wells With Downhole Water Loop Completion for Bottomwater Control
Authors: Jin Lu , Wojtanowicz Andrew Krzysztof , Afonja Gbolahan , Li Wenjing
Published: October 2010

The theoretical paper presents development and verification of dimensionless groups describing a novel "smart?? well completion with downhole water loop (DWL) that stimulates wells affected by water coning. A well producing from an oil reservoir with bottomwater coning is completed at the top of oil for oil inflow and lifting, below the oil/water contact (OWC) for water drainage and deeper in the same aquifer for water injection. The two lower completions are hydraulically isolated from the top completion and work as a "water loop?? by draining the water to control OWC deformation (water cone) and injecting the drained water into the same aquifer. To date, computer simulations and field trials have shown that the wells with bottomwater drainage would produce more oil, and sooner, by removing water invasion to the oil-producing completion. However, addition of the water injection component makes the well's completion more complex and controlled by a multitude of well system parameters and reservoir and fluid properties. Therefore, dimensionless analysis is needed to simplify the system's description using only few dimensionless groups.

The study employs the inspectional analysis (IA) method to confirm known and define new dimensionless groups specific for DWL wells. Then, the resulting cluster of dimensionless groups has been reduced by verifying the groups for redundancy and interdependence.

Further reduction of the number of groups - from 14 to seven - has been accomplished by testing sensitivity of the recovery factor to the groups. Of the final seven, four dimensionless groups uniquely describe the DWL system.
Distributions of Median Nutrient and Chlorophyll Concentrations across the Red River Basin, USA
Authors: Longing S. D. , Haggard B. E.
Published: October 2010

Acquisition and compilation of water‐quality data for an 11‐yr time period (1996–2006) from 589 stream and river stations were conducted to support nutrient criteria development for the multistate Red River Basin shared by Arkansas, Louisiana, New Mexico, Oklahoma, and Texas. Ten water‐quality parameters were collected from six data sources (USGS, Arkansas Department of Environmental Quality, Louisiana Department of Environmental Quality, Oklahoma Conservation Commission, Oklahoma Water Resources Board, and Texas Commission on Environmental Quality), and an additional 13 parameters were acquired from at least one source. Median concentrations of water‐quality parameters were calculated at each individual station and frequency distributions (minimum, 10th, 25th, 50th, 75th, 90th percentiles, and maximum) of the median concentrations were calculated. Across the Red River Basin, median values for total nitrogen (TN), total phosphorus (TP), and sestonic chlorophyll‐a (chl‐a) ranged from <0.02 to 20.2 mg L−1, <0.01 to 6.66 mg L−1, and 0.10 to 262 μg L−1, respectively. Overall, the 25th percentiles of TN data specific to the Red River Basin were generally similar to the USEPA‐recommended ecoregion nutrient criteria of 0.31 to 0.88 mg L−1, whereas median TP and chl‐a data specific to the Red River Basin showed 25th percentiles higher than the USEPA‐recommended criteria (0.010–0.067 mg TP L−1; 0.93–3.00 μg chl‐a L−1). The unique location of the Red River Basin in the south‐central United States places it near the boundaries of several aggregate ecoregions; therefore, the development of ecoregion nutrient criteria likely requires using data specific to the Red River Basin, as shown in these analyses. This study provided basin‐specific frequency distribution of median concentrations of water‐quality parameters as the first step to support states in developing nutrient criteria to protect designated uses in the multijurisdictional Red River Basin.
Transport and Retention of Fullerene Nanoparticles in Natural Soils
Authors: Wang Yonggang , Li Yusong , Kim Hyunjung , Walker Sharon L. , Abriola Linda M. , Pennell Kurt D.
Published: October 2010

Commercial production and use of fullerene (C60) nanomaterials will inevitably lead to their release into the environment, where knowledge of C60 fate and transport is limited. In this study, a series of one‐dimensional column experiments was conducted to assess the transport and retention of nanoscale fullerene aggregates (nC60) in water‐saturated soils. Under the experimental conditions, complete retention of nC60 was observed in columns (2.5 cm inside diameter × 11 cm length) packed with Appling or Webster soil, which contain 0.75 and 3.33% organic carbon by weight, respectively. When the volume of aqueous nC60 suspension (∼4.5 mg L−1) applied to Appling soil was increased from 5 to 65 pore volumes, the travel distance increased from 3 to 8 cm, and the retention capacity approached a limiting value of 130 μg g−1, although nC60 was not detected in the column effluent. The addition of 20 mg C L−1 Suwannee River humic acid to the influent suspension increased the nC60 transport in Appling soil but did not result in breakthrough. Attempts to simulate the experimental data using clean‐bed filtration theory were not satisfactory, yielding retention profiles that failed to match observed data. Subsequent incorporation of a limiting retention capacity expression into the mathematical model resulted in accurate predictions of the measured nC60 retention profiles and transport behavior. The sizable retention capacities observed in this study suggest that transport of nC60 is limited in relatively fine‐textured soils containing appreciable amounts of clay minerals and organic matter, with substantial accumulation of nC60 aggregates near the point of release.
Fate and Transport of Engineered Nanomaterials in the Environment
Authors: Lin Daohui , Tian Xiaoli , Wu Fengchang , Xing Baoshan
Published: October 2010

With the fast development of nanotechnology, engineered nanomaterials (ENMs) will inevitably be introduced into the environment. Increasing studies showed the toxicity of various ENMs, which raises concerns over their fate and transport in the environment. This review focuses on advances in the research on environmental transport and fate of ENMs. Aggregation and suspension behaviors of ENMs determining their fate and transport in aqueous environment are discussed, with emphasis on the influencing factors, including natural colloids, natural organic matter, pH, and ionic strength. Studies on the transport of ENMs in porous media and its influencing factors are reviewed, and transformation and organism cleansing, as two fate routes of ENMs in the environment, are addressed. Future research directions and outlook in the environmental transport and fate of ENMs are also presented.
Association of Quantum Dot Nanoparticles with Pseudomonas aeruginosa Biofilm
Authors: Morrow Jayne B. , P. Catalina Arango , Holbrook R. David
Published: October 2010

Quantum dots (QDs) of two different surface chemistries (carboxyl [COOH] and polyethylene glycol [PEG] modified) were utilized to determine the impact of surface functionality on QD mobility and distribution in Pseudomonas aeruginosa PAO1 biofilms. Confocal laser scanning microscopy was utilized to evaluate QD association with biofilm components (proteins, cells, and polysaccharides). Quantum dots did not preferentially associate with cell surfaces compared but did colocalize with extracellular proteins in the biofilm matrix. Neither PEG nor COOH QDs were found to be internalized by individual bacterial cells. Neither QD functionality nor flow rate of QD application (0.3 mL min−1 or 3.0 mL min−1) resulted in a marked difference in QD association with P. aeruginosa biofilms. However, center of density determinations indicated COOH QDs could more easily penetrate the biofilm matrix by diffusion than PEG QDs. Biofilms with PEG QDs associated had rougher polysaccharide layers and rougher cell distribution than biofilms with COOH QDs. This work suggests natural biofilms may serve as deposition locations in natural and engineered environmental systems, and biofilm structural parameters may change based on exposure to nanomaterials of varied physical characteristics.
Nanoparticle Aggregation: Challenges to Understanding Transport and Reactivity in the Environment
Authors: Hotze Ernest M. , Phenrat Tanapon , Lowry Gregory V.
Published: October 2010

Unique forms of manufactured nanomaterials, nanoparticles, and their suspensions are rapidly being created by manipulating properties such as shape, size, structure, and chemical composition and through incorporation of surface coatings. Although these properties make nanomaterial development interesting for new applications, they also challenge the ability of colloid science to understand nanoparticle aggregation in the environment and the subsequent effects on nanomaterial transport and reactivity. This review briefly covers aggregation theory focusing on Derjaguin‐Landau‐Verwey‐Overbeak (DLVO)‐based models most commonly used to describe the thermodynamic interactions between two particles in a suspension. A discussion of the challenges to DLVO posed by the properties of nanomaterials follows, along with examples from the literature. Examples from the literature highlighting the importance of aggregation effects on transport and reactivity and risk of nanoparticles in the environment are discussed.
An Ecological Perspective on Nanomaterial Impacts in the Environment
Authors: Bernhardt Emily S. , Colman Benjamin P. , Hochella Michael F. , Cardinale Bradley J. , Nisbet Roger M. , Richardson Curtis J. , Yin Liyan
Published: October 2010

Growing concerns over the potential for unintended, adverse consequences of engineered nanoparticles (ENPs) in the environment have generated new research initiatives focused on understanding the ecological effects of ENPs. Almost nothing is currently known about the fate and transport of ENPs in environmental waters, soils, and sediments or about the biological impacts of ENPs in natural environments, and the bulk of modern nanotoxicogical research is focused on highly controlled laboratory studies with single species in simple media. In this paper, we provide an ecological perspective on the current state of knowledge regarding the likely environmental impacts of nanomaterials and propose a strategy for making rapid progress in new research in ecological nanoscience.
Copper Lability in Soils Subjected to Intermittent Submergence
Authors: Biasioli M. , Kirby J. K. , Hettiarachchi G. M. , Ajmone‐Marsan F. , McLaughlin M. J.
Published: October 2010

Reducing conditions in soils can have significant influences on the availability of nutrient and toxic metals, through their remobilization, their release through reductive dissolution of oxide phases, and from the formation of precipitates. In the literature, contrasting results are reported on the effects of temporary waterlogging conditions on the availability of metals. In the present study, changes in the “labile” or “potentially available” pool of copper (Cu) in soils as a consequence of up to three intermittent soil submergence cycles was investigated using isotopic dilution. The soils (an Oxisol and an Inceptisol) selected were amended in the field with both biosolids‐Cu and salt‐Cu. Intermittent soil submergence was found to have a significant effect on the lability of Cu in soils, with Etotal values generally increasing in all the treatments with the different submergence cycles, the highest lability of Cu observed in the Cu‐salt treatment. The presence of nonexchangeable colloidal forms of Cu, influenced by treatments and submergence cycles, was also reported.
Multiscale Effects of Management, Environmental Conditions, and Land Use on Nitrate Leaching in Dairy Farms
Authors: Oenema Jouke , Burgers Saskia , Verloop Koos , Hooijboer Arno , Boumans Leo , Berge Hein ten
Published: October 2010

Nitrate leaching in intensive grassland‐ and silage maize‐based dairy farming systems on sandy soil is a main environmental concern. Here, statistical relationships are presented between management practices and environmental conditions and nitrate concentration in shallow groundwater (0.8 m depth) at farm, field, and point scales in the Netherlands, based on data collected in a participatory approach over a 7‐yr period at one experimental and eight pilot commercial dairy farms on sandy soil. Farm milk production ranged from 10 to 24 Mg ha−1 Soil and hydrological characteristics were derived from surveys and weather conditions from meteorological stations. Statistical analyses were performed with multiple regression models. Mean nitrate concentration at farm scale decreased from 79 mg L−1 in 1999 to 63 in 2006, with average nitrate concentration in groundwater decreasing under grassland but increasing under maize land over the monitoring period. The effects of management practices on nitrate concentration varied with spatial scale. At farm scale, nitrogen surplus, grazing intensity, and the relative areas of grassland and maize land significantly contributed to explaining the variance in nitrate concentration in groundwater. Mean nitrate concentration was negatively correlated to the concentration of dissolved organic carbon in the shallow groundwater. At field scale, management practices and soil, hydrological, and climatic conditions significantly contributed to explaining the variance in nitrate concentration in groundwater under grassland and maize land. We conclude that, on these intensive dairy farms, additional measures are needed to comply with the European Union water quality standard in groundwater of 50 mg nitrate L−1 The most promising measures are omitting fertilization of catch crops and reducing fertilization levels of first‐year maize in the rotation.
Phosphorus Concentrations, Loads, and Sources within the Illinois River Drainage Area, Northwest Arkansas, 1997–2008
Authors: Haggard Brian E.
Published: October 2010

In the Ozark Highlands and across the United States, effluent phosphorus (P) sources often have a profound impact on water column concentrations and riverine transport. This study evaluated (i) annual P loads at the Illinois River at Arkansas Highway 59 from calendar year 1997 through 2008, (ii) the relative contribution of effluent P sources to annual riverine P transport, (iii) longitudinal gradients in water column P concentrations downstream from several wastewater treatment plant effluent discharges, and (iv) changes in monthly P loads over the last decade. This study showed that annual P loads have ranged from 64,000 kg to over 426,000 kg and that P transport was positively correlated to hydrology (i.e., the amount of water delivered downstream). The relative contribution of P inputs from municipal facilities has decreased from 40% of the annual P load at the Illinois River at Arkansas Highway 59 to <15% in recent years. Elevated P concentrations during base flow conditions were traced 45 river km upstream to one municipal effluent discharge, but all effluent discharges influenced P concentrations in the receiving streams. Most important, flow‐adjusted monthly P loads showed two distinct trends over time. Flow‐adjusted loads significantly increased from 1997 through 2002 and significantly decreased from 2002 through 2008. The concentrations and transport of P within the Illinois River drainage area are significantly decreasing from all the watershed management changes that have occurred, and monitoring should continue to determine if this decrease continues at the same rate over the next several years.
The Role of Atmospheric Transformations in Determining Environmental Impacts of Carbonaceous Nanoparticles
Authors: Tiwari Andrea J. , Marr Linsey C.
Published: October 2010

In studies that have explored the potential environmental impacts of manufactured nanomaterials, the atmosphere has largely been viewed as an inert setting that acts merely as a route for inhalation exposure. Manufactured nanomaterials will enter the atmosphere during production, use, and disposal, and rather than simply being transported, airborne nanoparticles are in fact subject to physical and chemical transformations that could modify their fate, transport, bioavailability, and toxicity once they deposit to aqueous and terrestrial ecosystems. The objective of this paper is to review the factors affecting carbonaceous nanomaterials' behavior in the environment and to show that atmospheric transformations, often overlooked, have the potential to alter nanoparticles' physical and chemical properties and thus influence their environmental fate and impact. Atmospheric processing of naturally occurring and incidental nanoparticles takes place through coagulation, condensation, and oxidation; these phenomena are expected to affect manufactured nanoparticles as well. It is likely that carbonaceous nanomaterials in the atmosphere will be oxidized, effectively functionalizing them. By influencing size, shape, and surface chemistry, atmospheric transformations have the potential to affect a variety of nanoparticle–environment interactions, including solubility, interaction with natural surfactants, deposition to porous media, and ecotoxicity. Potential directions for future research are suggested to address the current lack of information surrounding atmospheric transformations of engineered nanomaterials.
Quantifying Nitrogen Process Rates in a Constructed Wetland Using Natural Abundance Stable Isotope Signatures and Stable Isotope Amendment Experiments
Authors: Erler Dirk V. , Eyre Bradley D.
Published: October 2010

This study describes the spatial variability in nitrogen (N) transformation within a constructed wetland (CW) treating domestic effluent. Nitrogen cycling within the CW was driven by settlement and mineralization of particulate organic nitrogen and uptake of NO3− The concentration of NO3− was found to decrease, as the δ15N‐NO3− signature increased, as water flowed through the CW, allowing denitrification rates to be estimated on the basis of the degree of fractionation of δ15N‐NO3− Estimates of denitrification hinged on the determination of a net isotope effect (η), which was influenced by processes that enrich or deplete 15NO3− (e.g., nitrification), as well as the rate constants associated with the different processes involved in denitrification (i.e., diffusion and enzyme activity). The influence of nitrification on η was quantified; however, it remained unclear how η varied due to variability in denitrification rate constants. A series of stable isotope amendment experiments was used to further constrain the value of η and calculate rates of denitrification, and nitrification, within the wetland. The maximum calculated rate of denitrification was 956 ± 187 μmol N m−2 h−1, and the maximum rate of nitrification was 182 ± 28.9 μmol N m−2 h−1 Uptake of NO3− was quantitatively more important than denitrification throughout the wetland. Rates of N cycling varied spatially within the wetland, with denitrification dominating in the downstream deoxygenated region of the wetland. Studies that use fractionation of N to derive rate estimates must exercise caution when interpreting the net isotope effect. We suggest a sampling procedure for future natural abundance studies that may help improve the accuracy of N cycling rate estimates.
Characterization and Dispersion Modeling of Odors from a Piggery Facility
Authors: Karageorgos Petros , Latos Manolis , Mpasiakos Christos , Chalarakis Elefterios , Dimitrakakis Emmanuel , Daskalakis Charis , Psillakis Elefteria , Lazaridis Mihalis , Kalogerakis Nicolas
Published: October 2010

Piggeries are known for their nuisance odors, creating problems for workers and nearby residents. Chemical substances that contribute to these odors include sulfurous organic compounds, hydrogen sulfide, phenols and indoles, ammonia, volatile amines, and volatile fatty acids. In this work, daily mean concentrations of ammonia (NH3) and hydrogen sulfide (H2S) were measured by hand‐held devices. Measurements were taken in several places within the facility (farrowing to finishing rooms). Hydrogen sulfide concentration was found to be 40 to 50 times higher than the human odor threshold value in the nursery and fattening room, resulting in strong nuisance odors. Ammonia concentrations ranged from 2 to 18 mL m−3 and also contributed to the total odor nuisance. Emission data from various chambers of the pig farm were used with the dispersion model AERMOD to determine the odor nuisance caused due to the presence of H2S and NH3 to receptors at various distances from the facility. Because just a few seconds of exposure can cause an odor nuisance, a “peak‐to‐mean” ratio was used to predict the maximum odor concentrations. Several scenarios were examined using the modified AERMOD program, taking into account the complex terrain around the pig farm.
Effect of Electrokinetics on the Bioaccessibility of Polycyclic Aromatic Hydrocarbons in Polluted Soils
Authors: Niqui‐Arroyo José‐Luis , Ortega‐Calvo José‐Julio
Published: October 2010

Bioaccessibility is one of the most relevant aspects to be considered in the restoration of soils using biological technologies. Polycyclic aromatic hydrocarbons (PAH) usually have residual fractions that are resistant to biodegradation at the end of the biological treatment. In some situations, these residual concentrations could still be above legal standards. Here, we propose that the available knowledge about electroremediation technologies could be applied to enhance bioremediation of soils polluted with PAH. The main objective of this study was to show that a previous electrokinetic treatment could reduce the PAH residual fractions when the soil is subsequently treated by means of a bioremediation process. The approach involved the electrokinetic treatment of PAH‐polluted soils at a potential drop of 0.9 to 1.1 V/cm and the subsequent estimations of bioaccessibility of residual PAHs after slurry‐phase biodegradation. Bioaccessibility of PAH in two creosote‐polluted soils (clay and loamy sand, total PAH content averaging 300 mg/kg) previously treated with an electric field in the presence of nonionic surfactant Brij 35 was often higher than in untreated controls. For example, total PAH content remaining in clay soil after bioremediation was only 62.65 ± 4.26 mg/kg, whereas a 7‐d electrokinetic pretreatment had, under the same conditions, a residual concentration of 29.24 ± 1.88 mg/kg after bioremediation. Control treatments without surfactant indicated that the electrokinetic treatment increased bioaccessibility of PAHs. A different manner of electric field implementation (continuous current vs. current reversals) did not induce changes in PAH bioaccessibility. We suggest that this hybrid technology may be useful in certain bioremediation scenarios, such as soils rich in clay and black carbon, which show limited success due to bioavailability restrictions, as well as in highly heterogeneous soils.
Phytoestrogens and Mycotoxins in Iowa Streams: An Examination of Underinvestigated Compounds in Agricultural Basins
Authors: Kolpin Dana W. , Hoerger Corinne C. , Meyer Michael T. , Wettstein Felix E. , Hubbard Laura E. , Bucheli Thomas D.
Published: October 2010

This study provides the first broad‐scale investigation on the spatial and temporal occurrence of phytoestrogens and mycotoxins in streams in the United States. Fifteen stream sites across Iowa were sampled five times throughout the 2008 growing season to capture a range of climatic and crop‐growth conditions. Basin size upstream from sampling sites ranged from 7 km2to >836,000 km2Atrazine (herbicide) also was measured in all samples as a frame‐of‐reference agriculturally derived contaminant. Target compounds were frequently detected in stream samples: atrazine (100%), formononetin (80%), equol (45%), deoxynivalenol (43%), daidzein (32%), biochanin A (23%), zearalenone (13%), and genistein (11%). The nearly ubiquitous detection of formononetin (isoflavone) suggests a widespread agricultural source, as one would expect with the intense row crop and livestock production present across Iowa. Conversely, the less spatially widespread detections of deoxynivalenol (mycotoxin) suggest a more variable source due to the required combination of proper host and proper temperature and moisture conditions necessary to promoteFusariumspp. infections. Although atrazine concentrations commonly exceeded 100 ng L−1(42/75 measurements), only deoxynivalenol (6/56 measurements) had concentrations that occasionally exceeded this level. Temporal patterns in concentrations varied substantially between atrazine, formononetin, and deoxynivalenol, as one would expect for contaminants with different source inputs and processes of formation and degradation. The greatest phytoestrogen and mycotoxin concentrations were observed during spring snowmelt conditions. Phytoestrogens and mycotoxins were detected at all sampling sites regardless of basin size. The ecotoxicological effects from long‐term, low‐level exposures to phytoestrogens and mycotoxins or complex chemicals mixtures including these compounds that commonly take place in surface water are poorly understood and have yet to be systematically investigated in environmental studies.
Sequential Accelerated Solvent Extraction of Polycyclic Aromatic Hydrocarbons with Different Solvents: Performance and Implication
Authors: Xiaoxuan Ma , Yong Ran , Jian Gong , Diyun Chen
Published: October 2010

Sixteen USEPA priority polycyclic aromatic hydrocarbons (PAHs) extracted by Soxhlet extraction (S‐PAHs) with dichloromethane and routine accelerated solvent extraction (A‐PAHs) with 1:1 toluene/methanol, respectively, were investigated in 24 soil samples from two cities in the center of the Pearl River Delta, South China. Polycyclic aromatic hydrocarbons, methylphenanthrene and perylene, in two soils, two sediments, and an immature oil shale were also sequentially extracted by accelerated solvent extraction (ASE) with each of four different organic solvents for three times. The A‐PAHs' concentrations are 2.41 times the S‐PAHs' concentrations. For sequential three ASEs, PAHs in the first extract account for 56 to 67% of their total concentrations in the sequential three extractions and toluene displays the best extraction performance among the four solvents. Diagnostic ratios of PAHs in Soxhlet extraction, routine ASE, and sequential ASE with each solvent for a given sample are very similar, suggesting their identical petrogenic and pyrogenic sources in the soils and sediments. But the PAH ratios for the shale have an obvious petrogenic origin. The perylene/5‐ring PAH ratios indicate a diagenetic source, especially in the shale and sediments. The correlation analysis shows that A‐PAHs/S‐PAHs is better associated with the contents of total organic carbon (TOC) than those of black carbon (BC). The above results indicate the significant petrogenic origin of PAHs and the important effect of organic matter on their extraction and distribution in the investigated field soils/sediments.
Nontarget Deposition and Losses of Chlorothalonil in Irrigation Runoff Water from a Commercial Foliage Plant Nursery
Authors: Wilson P. Chris , Riiska Catherine , Albano Joseph P.
Published: October 2010

Commercial foliage plant production requires the use of pesticides for controlling pests and pathogens that can reduce aesthetic qualities of crops, rendering them unwanted by consumers. Chlorothalonil is a common, broad‐spectrum, foliar fungicide used for protecting plants from a variety of fungal diseases. This fungicide may also be acutely toxic to nontarget aquatic organisms due to its mode of action. This study evaluated the amount of chlorothalonil deposited on nontarget ground surfaces during normal sprayer applications at a commercial nursery using Teflon targets. One day following application, irrigation runoff events were initiated and runoff water samples were collected and analyzed for chlorothalonil. Discharge volumes were also measured to allow estimation of the total mass of chlorothalonil discharged during each event. Results indicated that 9.8 to 53.6% of the active ingredient applied landed on nontarget ground surfaces depending on plant size, spacing, and row lengths (short rows sprayed from one side vs. longer rows sprayed from both ends). On an entire production‐area scale, 29.2% of the active ingredient applied was deposited on ground surfaces. Of the total nontarget deposition, 0.25 to 0.53% was detected in runoff water discharged from the production area. Concentrations ranged from 1.2 to 500 μg/L during the first runoff events following application.
Environmental Occurrences, Behavior, Fate, and Ecological Effects of Nanomaterials: An Introduction to the Special Series
Authors: Lowry Gregory V. , Hotze Ernest M. , Bernhardt Emily S. , Dionysiou Dionysios D. , Pedersen Joel A. , Wiesner Mark R. , Xing Baoshan
Published: October 2010

The release of engineered nanomaterials (ENMs) into the biosphere will increase as industries find new and useful ways to utilize these materials. Scientists and engineers are beginning to assess the material properties that determine the fate, transport, and effects of ENMs; however, the potential impacts of released ENMs on organisms, ecosystems, and human health remain largely unknown. This special collection of four review papers and four technical papers identifies many key and emerging knowledge gaps regarding the interactions between nanomaterials and ecosystems. These critical knowledge gaps include the form, route, and mass of nanomaterials entering the environment; the transformations and ultimate fate of nanomaterials in the environment; the transport, distribution, and bioavailability of nanomaterials in environmental media; and the organismal responses to nanomaterial exposure and effects of nanomaterial inputs on ecological communities and biogeochemical processes at relevant environmental concentrations and forms. This introductory section summarizes the state of knowledge and emerging areas of research needs identified within the special collection. Despite recent progress in understanding the transport, transformations, and fate of ENMs in model environments and organisms, there remains a large need for fundamental information regarding releases, distribution, transformations and persistence, and bioavailability of nanomaterials. Moreover, fate, transport, bioaccumulation, and ecological impacts research is needed using environmentally relevant concentrations and forms of ENMs in real field materials and with a broader range of organisms.
Impact of Vertical Hydraulic Gradient on Rill Erodibility and Critical Shear Stress
Authors: Nouwakpo Sayiro K. , Huang Chi-hua , Bowling Laura , Owens Phillip
Published: October 2010

Field observations and subsequent support from controlled lab experiments have shown the linkage between vertical hydraulic gradients and initiation of rills or incised channels. Nevertheless, current erosion prediction models do not include the hydraulic gradient effect in the erodibility parameters. The objectives of this study were to: (i) quantify the impact of a subsurface hydraulic gradient on rill erodibility and critical shear stress; and (ii) determine the intrinsic critical shear stress of the soil, which is the critical shear stress of the soil without the influence of the vertical hydraulic gradient. Two series of concentrated flow experiments were conducted on a silt loam soil subjected to hydraulic gradients varying from −2 to 2 m m−1 The first series measured soil loss at a given shear stress, while the second was a direct measurement of the critical shear stress by calculating the shear stress at the point of incipient motion of particles. The intrinsic critical shear stress was determined using a fluidized bed approach. We found that the average erodibility under an upward or positive hydraulic gradient was 5.64 times larger than that under a downward hydraulic gradient. The critical shear stress decreased from 1.0 to 0.2 Pa as the hydraulic gradient was increased from −2 to 2 m m−1 Using the fluidized bed approach, we obtained an inherent critical shear stress value of 1.61 Pa. We concluded that the presence of positive pore pressure near the soil surface was a major factor in reducing soil cohesion. We also concluded that with some improvements, the fluidized bed concept can be applied to determine the critical shear stress independent of the hydraulic gradient effect.
Estimating Pedotransfer Function Prediction Limits Using Fuzzy k‐Means with Extragrades
Authors: Tranter G. , Minasny B. , McBratney A. B.
Published: October 2010

We have developed a method for estimating the pedotransfer function uncertainty using fuzzy k‐means with extragrades classification to, first, identify specific areas of covariate space that share similar residuals or distribution of residuals and, second, identify those observations that exist outside the convex hull of the calibration data. Those observations outside the convex hull are considered outliers of the calibration data and subsequently have their uncertainty penalized by a simple multiplier. Uncertainties are presented as upper and lower prediction limits. In addition, the method can be extended to estimate the cumulative density function for the prediction residual. The method was applied to a pedotransfer function for the prediction of gravimetric moisture content at permanent wilting points (‐1500 kPa). The method conformed closely to the desired confidence level; however, some instability was shown at confidence levels >80%. The ability to identify conditions “dissimilar” to those used for model calibration makes the method suitable for a diverse range of prediction problems.
Importance of the Water Table in Controlling Dissolved Carbon along a Fen Nutrient Gradient
Authors: Webster Kara L. , McLaughlin James W.
Published: October 2010

Boreal fens are minerotrophic peatlands that act as important control points for dissolved C between upland and aquatic ecosystems. Fens occupy a minerotrophic continuum from “rich,” having high water tables and large nutrient contributions from upland sources, to “poor,” having low water tables and small nutrient contributions. Dissolved C within these fens will be influenced by the degree of minerotrophy, which in turn impacts peat pore water acidity and alkalinity and downstream productivity. To examine how dissolved C concentrations change along the minerotrophic gradient and to explore possible mechanisms controlling their concentration, pore water chemistry was analyzed from piezometers at 25‐, 50‐, and 100‐cm depths in rich, intermediate, and poor fens during the snow‐free periods of 2005, 2006 (dissolved organic C [DOC] only), 2007, and 2008. We found that dissolved inorganic C (DIC) concentrations increased with higher water tables (poor < intermediate < rich) and wetter years (2005 < 2007 ∼ 2008). In contrast, DOC concentrations decreased with higher water tables (rich < intermediate < poor), but the effect differed among years. Wetter conditions resulted in high DOC concentrations in the intermediate fen, low concentration in the poor fen, and no change in the rich fen. Correlation analyses suggest that DIC concentrations may be linked to groundwater contribution of carbonate materials and DOC to ionic strength and mechanisms of productivity and decomposition. Although further experimentation is required to verify these mechanisms, the evidence points to the importance of minerotrophic status when considering the role of peatlands in watershed C balances and their response to changing climate.
Crop Yield and Soil Phosphorus as Affected by Liquid Swine Manure Phosphorus Application Using Variable‐Rate Technology
Authors: Mallarino Antonio P. , Wittry David J.
Published: October 2010

Soil‐test P (STP) and crop P needs vary within fields and variable‐rate technology can be used to apply P more effectively. The objective of this study was to evaluate within a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation grain yield and STP response to fixed‐rate (FR) and variable‐rate (VR) liquid swine (Sus scrofa domesticus) manure P application using strip‐trials, global positioning systems (GPS), yield monitors, and geographical information systems (GIS). Treatments replicated four or five times were a control and manure P applied with FR or VR once before soybean of two rotation cycles in one field and three cycles in another. Strip width and length were 18.3 m and 605 to 660 m, respectively. Initial soil samples were taken from 0.3‐ha cells and post‐harvest samples were taken each year by treatment (0.1‐ha cells). High N (for corn) and K rates were applied uniformly across all strips. Manure P increased strip‐average grain yield (P ≤ 0.05) in eight of nine site‐years but yield for FR and VR did not differ. The study of yield responses for field areas with different STP showed that manure P always increased yield with STP very low or low (<16 mg Bray‐P1 kg−1) and only in three site‐years with STP optimum (16–20 mg P kg−1). Yield responses differed between FR and VR in very low areas of one site‐year, where VR increased corn yield more than FR. The VR method reduced within‐field STP variability compared with FR with the exception of only one site‐year. Although VR did not increase yield compared with FR, less manure P was applied to high‐testing areas and it reduced STP variability.