bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiment to mitigate size effect on deep beams
Authors: Tan K.-H. , Cheng G.-H. , Zhang N.
Published: September 2008

Size effect is a phenomenon in reinforced-concrete beams associated with a reduction of shear strength owing to an increase in member size. It is postulated here that the size effect is related to the effectiveness of strut-and-tie model (STM), the mobilisation of which largely depends on the strut geometry and the strut boundary conditions. Strut geometry is governed by the size of the loading and support plates as well as the beam depth, while strut boundary conditions are governed by the spacing and diameter of web reinforcement transverse to the inclined struts. The test programme provided experimental evidence to the hypotheses obtained from STM. Test specimens consisted of two groups of four geometrically similar specimens. The first group consisted of beams without any web reinforcement; the dimensions of the loading and support plates were kept constant. The second group corresponded to the first group, except that they had (a) orthogonal web reinforcement and (b) proportionally increased loading and support plate widths. It was observed that the ultimate shear strengths reduced sharply for the first group of beams without web reinforcement, showing significant size effect. For the second group of beams the ultimate shear strengths were, however, size independent.
Compressive behaviour of CFRP-confined rectangular concrete columns
Authors: Tao Z. , Yu Q. , Zhong Y.-Z.
Published: September 2008

While there is abundant research on fibre reinforced polymer (FRP)-confined circular concrete columns, information on FRP-confined rectangular concrete columns is much more limited. This paper thus presents the axial compression test results of carbon fibre reinforced polymer (CFRP)-confined concrete short columns with rectangular cross-sections. The parameters considered in this study were (a) the concrete strength; (b) the cross-sectional aspect ratio; (d) the number of CFRP layers; and (d) the corner radius. Five existing design-oriented models were used to predict the stress–strain curves of the test specimens with an aim to verify their accuracy. Considerable deviations were found between various model predictions.
A linear test method for determining early-age shrinkage of concrete
Authors: Newlands M. D. , Paine K. A. , Vemuri N. A. , Dhir R. K.
Published: September 2008

For certain applications, the early-age dimensional stability of concrete can significantly affect aesthetics and long-term durability performance. The combined effects of plastic settlement, plastic shrinkage and autogenous shrinkage in fresh and hardening concrete will depend on mix proportions, constituent materials and environmental conditions as well as levels of crack inducing restraint. A new linear test method has been developed for measuring early-age shrinkage in concrete to allow investigation of the effects of new constituents on early volume stability. Single operator repeatability under laboratory conditions was investigated and the sensitivity of the test to varying temperature (20°C ± 2°C and 40°C ± 2°C), relative humidity (10% ± 2%, 50% ± 5%, 95% ± 5%) and wind velocity (7·5 km/h) was also determined. The test method was deemed suitable for use as a tool to measure the influence of new types of cements and aggregates on the early-age volume stability of concrete.
Fire tests on unbonded post-tensioned one-way concrete slabs
Authors: Bailey C.G. , Ellobody E.
Published: September 2008

This paper presents the results from four fire tests carried out on one-way spanning unbonded post-tensioned concrete floor slabs. The elevated temperature tests are augmented with the results from two additional tests carried out to failure, on slabs with identical geometry and tendon reinforcement, at ambient temperature. The fire tests highlighted the different structural response between using limestone and Thames gravel aggregates and different restraint conditions to longitudinal thermal expansion. It is shown that slabs with Thames gravel aggregates have a much higher deflection compared to slabs with limestone aggregates. The restrained slabs had lower vertical deflection compared to the equivalent unrestrained slabs. In all the fire tests, cracks directly inline and parallel to the tendons occurred owing to thermal stresses at relatively low tendon temperatures, which were not observed in the ambient tests. In one fire test, which was taken to overall collapse, it was shown that the strength reduction factors for tendon reinforcement currently used in the European design codes is conservative. The test data, comprising tendon strains, vertical and horizontal displacements and temperatures through the slab, will allow validation of developed computer models to predict the behaviour of unbonded slabs under fire conditions.
An experimental study on shear strengthening of RC T-section beams with CFRP plates subjected to cyclic load
Authors: Sakar G. , Tanarslan H.M. , Alku O.Z.
Published: September 2008

The aim of this experimental study was to investigate the behaviour of reinforced concrete (RC) T-section beams that were strengthened by carbon fibre reinforced polymer (CFRP) plates. Six specimens, one of which was the control specimen and five of which were the shear deficient test specimens, were strengthened with side-bonded and ⍽-jacketed CFRP plates. Unidirectional and bidirectional CFRP sheets were used as strengthening material. Distinct CFRP type, CFRP arrangement, number of sheet layers and wrapping schemes were the variables that were investigated during the experimental programme. The main objective of the study was to obtain ductile flexural behaviour from the shear deficient RC T-section beams. Debonding reduces the strengthening potential of the externally bonded CFRP thus obstructs structures to meet the expected requirement from strengthening materials. To block debonding, mechanical anchorages were used at the end regions of CFRP plates. Test results confirmed that all performance CFRP arrangements differ from type and wrapping scheme improved the strength and behaviour of the specimens in different level significantly. Nevertheless, specimens that were strengthened with ⍽-jacketed bidirectional CFRP showed better strength and behaviour than the remaining specimens. To verify the reliability, test results were compared with results of ACI-440 design code and Concrete Society TR55.
Simultaneous heat and moisture transfer in concrete with time-dependent boundary conditions
Authors: Qian C. , Chen D. , Wang H. , Wang Y.
Published: September 2008

Temperature and moisture are responsible for the deterioration processes of concrete structures and the extensive failures in concrete elements often result from both thermal and moisture loads. Heat and moisture transfer in concrete with time-dependent boundary conditions was investigated by numerical simulation using the Coupling Temperature and Moisture Simulation System for Concrete (CTMSoft). The temperature and moisture distribution in concrete were numerically simulated through solving the coupling transfer equations based on heat and moisture transfer in porous media by analytical method inolving Laplace transformation and transfer function. The hygro-thermal induced by the moisture and temperature changes in concrete are analysed using CTMSoft. The comparison between the numerical and experimental (or Fiber Bragg Grating monitoring data) suggests that the numerical model can be used accurately to predict the deformation resulting from the simultaneous heat and moisture transfer.
Long-term behaviour of a reinforced concrete wall under compressive stress applied to part of the wall's entire width
Authors: Lee Y. , Lee B.-Y. , Kwon S.-H. , Kim Y.-Y. , Kim J.-K.
Published: September 2008

The purpose of this study is to suggest a method of quantitatively predicting long-term deformation of walls under an axial load concentrated on a part of the entire width of the walls. Four wall specimens were tested and three-dimensional finite element analyses were performed for these specimens. The test results verified the finite element models. On the basis of this verification, analysis parameters were selected with respect to various dimensions of the walls and the sectional area of the concentrated load, and finite element analyses for these parameters were carried out. The novel concept of the effective width coefficient was introduced as a method of predicting the long-term behaviour of walls. Furthermore, from the regression analysis, a function is suggested that can optimally fit the effective width coefficients that were calculated from the analysis results for the selected parameters. The suggested function can be conveniently used to predict the long-term behaviour under loads concentrated on a local area for the entire width of walls.
Re‐evaluating eradication of nuisance species: invasion of the tunicate, Ciona intestinalis
Authors: Edwards Paul K , Leung Brian
Published: September 2008

Eradication is an important concept in the management of biological invasions, but it is rarely considered in practice. This may be because managers commonly work with incomplete data and little or no practical guidance. Past eradication frameworks provide some useful criteria, but do not provide quantitative guidelines. Here, we argue that eradication is not always adequately considered, and we develop a framework for rapid assessment of its feasibility, despite limited data. This quantitative model offers criteria to rapidly assess the potential for eradication and provide estimates of the necessary effort and timing, and of the size of the target area. This framework is applied to a recent tunicate (Ciona intestinalis) invasion around Prince Edward Island, Canada, which is causing considerable economic damage to harvesters of blue mussels (Mytilus edulis). Our framework suggests that eradication may be feasible and, based on a cost–benefit analysis, could require only a ≥ 16% chance of success to constitute a worthwhile risk.
Metal accumulation and biomarker responses in Daphnia magna following cadmium and zinc exposure
Authors: Fan Wen-Hong , Tang GE , Zhao Chun-Mei , Duan Yong , Zhang Rong
Published: September 2008

Metal accumulation (quantified as body burden) and the responses of two biomarkers (metallothionein [MT] induction and superoxide dismutase [SOD] activity) in a freshwater cladoceran Daphnia magna were quantified after being exposed to different concentrations of Cd and Zn for 3 d. The Cd and Zn body burdens increased with increasing exposure concentrations. The responses of biomarkers were metal-specific and concentration-dependent. As a detoxification mechanism, MT was induced by exposure to Cd or Zn or Cd + Zn and was dependent on the exposure concentrations. Low concentrations of Cd or Zn exposure increased the SOD activity, which was, however, inhibited at higher metal exposure concentrations. Metallothionein concentrations in daphnids were significantly related to the metal body burden. The SOD activity was inversely related to Cd body burden, while it was independent of the Zn body burden. Survivorship of D. magna was high at lower Cd/MT ratios in the animals but then decreased linearly when the ratio exceeded six. In contrast, the relationship between survivorship and Zn/MT ratio was different due to the essentiality of Zn. Overall, MT induction was a useful indicator of metal pollution in cladocerans.
Selenium and mercury concentrations in California gulls breeding on the Great Salt Lake, Utah, USA
Authors: Conover Michael R. , Vest Josh L.
Published: September 2008

We examined selenium (Se) and mercury (Hg) concentrations in adult California gulls (Larus californicus) nesting on the Great Salt Lake, Utah, USA, during 2006 and 2007. During 2006, the mean Se concentration (± standard error) was 18.1 ± 1.5 μg/g in blood on a dry-weight basis and 8.1 ± 0.4 μg/g in liver. During 2007, Se concentrations were 15.7 ± 1.5 μg/g in blood and 8.3 ± 0.4 μg/g in liver; Hg concentrations were 2.4 ± 0.3 μg/g in blood and 4.1 ± 0.5 μg/g in liver. Gulls collected from a freshwater colony located within the watershed of the Great Salt Lake had similar levels of Se in the blood and liver as gulls collected on the Great Salt Lake but lower Hg concentrations. Body mass of adult gulls was not correlated with Se or Hg concentrations in their blood or liver. Selenium concentration in California gull eggs collected during 2006 was 3.0 ± 0.10 μg/g. Of 72 eggs randomly collected from Great Salt Lake colonies, only one was infertile, and none of the embryos exhibited signs of malposition or deformities. We examined 100 newly hatched California gull chicks from Great Salt Lake colonies for teratogenesis; all chicks appeared normal. Hence, the elevated Se and Hg concentrations in adult gulls nesting on the Great Salt Lake did not appear to impair gulls' health or reproductive ability.
Evaluation of Intra‐annual Variation in U.S. Geological Survey National Water Quality Assessment Ground Water Quality Data
Authors: Rosen Michael R. , Voss Frank D. , Arufe Jorge A.
Published: September 2008

Assessment of ground‐water quality trends under the U.S. Geological Survey National Water‐Quality Assessment Program (NAWQA) included the analysis of samples collected on a quarterly basis for 1 yr between 2001 and 2005. The purpose of this quarterly sampling was to test the hypothesis that variations in the concentration of water‐quality parameters of selected individual wells could demonstrate that the intra‐annual variation was greater or less than the decadal changes observed for a trend network. Evaluation of more than 100 wells over this period indicates that 1 yr of quarterly sampling is not adequate to address the issue of intra‐annual variation because variations seem to be random and highly variable between different wells in the same networks and among networks located in different geographical areas of the USA. In addition, the data from only 1 yr makes it impossible to assess whether variations are due to univariate changes caused by land use changes, hydrologic variations due to variable recharge, or variations caused by ground‐water pumping. These data indicate that funds allocated to this activity can be directed to the collection of more effective trend data, including age dating of all wells in the NAWQA network using multiple techniques. Continued evaluation of data and updating of monitoring plans of the NAWQA program is important for maintaining relevance to national goals and scientific objectives.
Agriculture‐Related Trends in Groundwater Quality of the Glacial Deposits Aquifer, Central Wisconsin
Authors: Saad David A.
Published: September 2008

Measuring and understanding trends in groundwater quality is necessary for determining whether changes in land‐management practices have an effect on groundwater quality. This paper describes an approach that was used to measure and understand trends using data from two groundwater studies conducted in central Wisconsin as part of the USGS NAWQA program. One of the key components of this approach, determining the age of sampled groundwater, gave a temporal component to the snapshots of water quality that were obtained through synoptic‐sampling efforts. This approach can be used at other locations where groundwater quality data are collected, groundwater age can be determined, and associated temporal data are available. Results of these studies indicate measured concentrations of nitrate and atrazine plus deethylatrazine were correlated to historical patterns of fertilizer and atrazine use. Concentrations of nitrate in groundwater have increased over time; concentrations of atrazine plus deethylatrazine increased and then decreased. Concentrations of nitrate also were correlated to screen depth below the water level and concentrations of dissolved O2; concentrations of atrazine plus deethylatrazine were correlated to dissolved O2and annual precipitation. To measure trends in concentrations of atrazine plus deethylatrazine, the data, collected over a near‐decadal period, were adjusted to account for changes in laboratory‐reporting levels and analytical recoveries. Only after accounting for these changes was it apparent that the median concentrations of atrazine plus deethylatrazine decreased over the near‐decadal interval between sampling efforts.
Decadal‐Scale Changes of Nitrate in Ground Water of the United States, 1988–2004
Authors: Rupert Michael G.
Published: September 2008

This study evaluated decadal‐scale changes of nitrate concentrations in ground water samples collected by the USGS National Water‐Quality Assessment Program from 495 wells in 24 well networks across the USA in predominantly agricultural areas. Each well network was sampled once during 1988–1995 and resampled once during 2000–2004. Statistical tests of decadal‐scale changes of nitrate concentrations in water from all 495 wells combined indicate there is a significant increase in nitrate concentrations in the data set as a whole. Eight out of the 24 well networks, or about 33%, had significant changes of nitrate concentrations. Of the eight well networks with significant decadal‐scale changes of nitrate, all except one, the Willamette Valley of Oregon, had increasing nitrate concentrations. Median nitrate concentrations of three of those eight well networks increased above the USEPA maximum contaminant level of 10 mg L−1Nitrate in water from wells with reduced conditions had significantly smaller decadal‐scale changes in nitrate concentrations than oxidized and mixed waters. A subset of wells had data on ground water recharge date; nitrate concentrations increased in response to the increase of N fertilizer use since about 1950. Determining ground water recharge dates is an important component of a ground water trends investigation because recharge dates provide a link between changes in ground water quality and changes in land‐use practices.
Regional Nitrate and Pesticide Trends in Ground Water in the Eastern San Joaquin Valley, California
Authors: Burow Karen R. , Shelton Jennifer L. , Dubrovsky Neil M.
Published: September 2008

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long‐term quality of ground water. In this study, spatial and temporal trends in concentrations of nitrate and pesticides in ground water in the eastern San Joaquin Valley, California, were evaluated to determine the long‐term effects of agricultural and urban development on regional ground‐water quality. Trends in concentrations of nitrate, the nematocide 1,2‐dibromo‐3‐chloropropane, and the herbicide simazine during the last two decades are generally consistent with known nitrogen fertilizer and pesticide use and with the position of the well networks in the regional ground‐water flow system. Concentrations of nitrate and pesticides are higher in the shallow part of the aquifer system where domestic wells are typically screened, whereas concentrations are lower in the deep part of the aquifer system where public‐supply wells are typically screened. Attenuation processes do not seem to significantly affect concentrations. Historical data indicate that concentrations of nitrate have increased since the 1950s in the shallow and deep parts of the aquifer system. Concentrations of nitrate and detection of pesticides in the deep part of the aquifer system will likely increase as the proportion of highly affected water contributed to these wells increases with time. Because of the time of travel between the water table and the deep part of the aquifer system, current concentrations in public‐supply wells likely reflect the effects of 40‐ to 50‐yr‐old management practices.
Short‐Term Sustainability of Drainage Water Reuse: Spatio‐Temporal Impacts on Soil Chemical Properties
Authors: Corwin Dennis L. , Lesch Scott M. , Oster James D. , Kaffka Stephen R.
Published: September 2008

Greater urban demand for finite water resources, increased frequency of drought resulting from erratic weather, and increased pressure to reduce drainage water volumes have intensified the need to reuse drainage water. A study was initiated in 1999 on a 32.4‐ha saline‐sodic field (Lethent clay loam series; fine, montmorillonitic, thermic, Typic Natrargid) located on the west side of California's San Joaquin Valley (WSJV) with the objective of evaluating the sustainability of drainage water reuse with respect to impact on soil quality. An evaluation after 5 yr of irrigation with drainage water is presented. Geo‐referenced measurements of apparent soil electrical conductivity (ECa) were used to direct soil sampling at 40 sites to characterize the spatial variability of soil properties (i.e., salinity, Se, Na, B, and Mo) crucial to the soil's intended use of growing Bermuda grass (Cynodon dactylon (l.) Pers.) for livestock consumption. Soil samples were taken at 0.3‐m increments to a depth of 1.2 m at each site in August 1999, April 2002, and November 2004. Drainage water varying in salinity (0.8–16.2 dS m−1), SAR (5.4–52.4), Mo (80–400 μg L−1), and Se (<1–700 μg L−1) was applied to the field since July 2000. An analysis of the general temporal trend shows that overall soil quality has improved due to leaching of B from the top 0.6 m of soil; salinity and Na from the top 1.2 m, but primarily from 0 to 0.6 m; and Mo from the top 1.2 m. Short‐term sustainability of drainage water reuse is supported by the results.
Fate and Transport of Pesticides in the Ground Water Systems of Southwest Georgia, 1993–2005
Authors: Dalton Melinda S. , Frick Elizabeth A.
Published: September 2008

Modern agricultural practices in the United States have resulted in nearly unrivaled efficiency and productivity. Unfortunately, there is also the potential for release of these compounds to the environment and consequent adverse affects on wildlife and human populations. Since 1993, the National Water‐Quality Assessment (NAWQA) program of the U.S. Geological Survey has evaluated water quality in agricultural areas to address these concerns. The objective of this study is to evaluate trends in pesticide concentrations from 1993–2005 in the surficial and Upper Floridan aquifers of southwest Georgia using pesticide and pesticide degradate data collected for the NAWQA program. There were six compounds—five herbicides and one degradate—that were detected in more than 20% of samples: atrazine, deethylatrazine (DEA), metolachlor, alachlor, floumeturon, and tebuthiuron. Of the 128 wells sampled during the study, only eight wells had pesticide concentrations that either increased (7) or decreased (1) on a decadal time scale. Most of the significant trends were increasing concentrations of pesticides in older water; median pesticide concentrations did not differ between the surficial and Upper Floridan aquifers from 1993 and 2005. Deethylatrazine, in the Upper Floridan aquifer, was the only compound that had a significant change (increase) in concentration during the study. The limited number of wells with increases in pesticide concentrations suggest that ground‐water sources of these compounds are not increasing in concentration over the time scale represented in this study.
Drainage Water Reuse: Biological, Physical, and Technological Considerations for System Management
Authors: Dudley Lynn M. , Ben‐Gal Alon , Lazarovitch Naftali
Published: September 2008

Previous reviews of drainage water reuse have discussed principles of water reuse and disposal; provided examples of reuse practices; offered reuse criteria for salinity, for trace elements, and for bacteria; discussed mitigation of dissolved trace elements in reuse strategies; and summarized the California experience with a focus on discussion of salinity, sodicity, B, Mo, and Se issues. This review emphasizes recent literature contributing to understanding physical and biological constraints to drainage water reuse. The potential for drip irrigation and, particularly, low‐flow/high‐frequency systems to enhance the use of drainage water while minimizing the deleterious effects on yield and on water and soil resources is examined using the numeric HYRDUS‐2d model. Additionally, an analytical model is used to illustrate physical and biological limitations to drainage water management that result from the self‐regulating nature of the soil–plant–water system. The models suggest that crop, soil, irrigation frequency, and delivery systems might be manipulated to reduce the quantity of drainage water, but they also suggest that the nature of the system may seriously constrain the amount of reduction that might be achieved.
Soil Enzyme Activities of Long‐Term Reclaimed Wastewater‐Irrigated Soils
Authors: Chen Weiping , Wu Laosheng , Frankenberger William T. , Chang Andrew C.
Published: September 2008

Studies have shown that physical and chemical properties of soils may be significantly changed when they are subjected to long‐term reclaimed water irrigation. It remains unclear how reclaimed water application may affect nutrient cycling in soils. Soil enzymes are responsible for the biogeochemical cycling of many elements and are more sensitive indicators of the ecological changes. In this study, 17 soil enzymes, including those associated with the C, N, P, and S cycles and two oxidoreductases (catalase and dehydrogenase), were assayed in soils obtained from five long‐term reclaimed wastewater irrigation sites in southern California. The soil enzyme activities varied widely among the sampling sites. Compared with their respective controls, the overall activities of enzymes involved in the cycling of the four elements in soil were enhanced by an average of 2.2‐ to 3.1‐fold. Principal component analysis and cluster analysis indicated that the soil microbial functional diversity may be evaluated based on activities of catalase, alkaline phosphatase, acid phosphatase, dehydrogenase, and urease.
Modeling Vadose Zone Processes during Land Application of Food‐Processing Waste Water in California's Central Valley
Authors: Miller Gretchen R. , Rubin Yoram , Mayer K. Ulrich , Benito Pascual H.
Published: September 2008

Land application of food‐processing waste water occurs throughout California's Central Valley and may be degrading local ground water quality, primarily by increasing salinity and nitrogen levels. Natural attenuation is considered a treatment strategy for the waste, which often contains elevated levels of easily degradable organic carbon. Several key biogeochemical processes in the vadose zone alter the characteristics of the waste water before it reaches the ground water table, including microbial degradation, crop nutrient uptake, mineral precipitation, and ion exchange. This study used a process‐based, multi‐component reactive flow and transport model (MIN3P) to numerically simulate waste water migration in the vadose zone and to estimate its attenuation capacity. To address the high variability in site conditions and waste–stream characteristics, four food‐processing industries were coupled with three site scenarios to simulate a range of land application outcomes. The simulations estimated that typically between 30 and 150% of the salt loading to the land surface reaches the ground water, resulting in dissolved solids concentrations up to sixteen times larger than the 500 mg L−1 water quality objective. Site conditions, namely the ratio of hydraulic conductivity to the application rate, strongly influenced the amount of nitrate reaching the ground water, which ranged from zero to nine times the total loading applied. Rock–water interaction and nitrification explain salt and nitrate concentrations that exceed the levels present in the waste water. While source control remains the only method to prevent ground water degradation from saline wastes, proper site selection and waste application methods can reduce the risk of ground water degradation from nitrogen compounds.
Sustainability of Land Application of Class B Biosolids
Authors: Pepper Ian L. , Zerzghi Huruy , Brooks John P. , Gerba Charles P.
Published: September 2008

Land application of Class B biosolids is routinely undertaken in the United States. However, due to public concern over potential hazards, the long‐term sustainability of land application has been questioned. Thus, the objective of this review article was to evaluate the sustainability of land application of Class B biosolids. To do this we evaluated (i) the fate and transport of potential biological and chemical hazards within biosolids, and (ii) the influence of long‐term land application on the microbial and chemical properties of the soil. Direct risks to human health posed by pathogens in biosolids have been shown to be low. Risks from indirect exposure such as aerosolized pathogens or microbially contaminated ground water are also low. A long‐term land application study showed enhanced microbial activity and no adverse toxicity effects on the soil microbial community. Long‐term land application also increased soil macronutrients including C, N, and, in particular, P. In fact, care should be taken to avoid contamination of surface waters with high phosphate soils. Available soil metal concentrations remained low over the 20‐yr land application period due to the low metal content of the biosolids and a high soil pH. Soil salinity increases were not detected due to the low salt content of biosolids and irrigation rates in excess of consumptive use rates for cotton. Our conclusion, based on these studies, is that long‐term land application of Class B biosolids is sustainable.
Geospatial Methods for Monitoring a Vegetative Treatment Area Receiving Beef Feedlot Runoff
Authors: Eigenberg Roger A. , Lesch Scott M. , Woodbury Bryan , Nienaber John A.
Published: September 2008

A vegetative treatment area (VTA) offers alternative solutions to traditional feedlot runoff holding ponds, but the distribution of nutrients is not easily defined. Methods for monitoring salt accumulations in soils have been demonstrated at the United States Salinity Laboratory, Riverside, CA. This study was conducted to determine if methods developed to inventory saline soils can be used to inventory a VTA designed to control feedlot runoff. A soil conductivity map was generated at a VTA site using electromagnetic induction equipment (Dualem‐1S) and global positioning satellite. The ESAP software package, developed by the United States Salinity Laboratory at Riverside, CA, was used to determine a representative set of (n = 20) soil sampling locations for estimating the chloride distribution in the VTA (Cl−: selected as an indicator ion to track feedlot runoff). An additional set of (n = 20) stratified random sampling (SRS) locations were selected for comparison. The ESAP‐generated, prediction‐based sampling plan exhibited better design optimality criteria than the SRS plan. Statistical validation tests confirmed that the regression model estimated from the ESAP‐generated sample data was capable of producing accurate and unbiased predictions of the natural log (Cl−) levels at the independently chosen SRS sites. The combination of geo‐referenced soil conductivity, directed soil sample data, and regression modeling provides a cost‐effective tool to observe and manage liquid flow patterns in a VTA.
Water Quality Improvements of Wastewater from Confined Animal Feeding Operations after Advanced Treatment
Authors: Vanotti Matias B. , Szogi Ariel A.
Published: September 2008

Current trends of animal production concentration and new regulations promote the need for environmentally safe alternatives to land application of liquid manure. These technologies must be able to substantially remove nutrients, heavy metals, and emissions of ammonia and odors and disinfect the effluent. A new treatment system was tested full‐scale in a 4360‐swine farm in North Carolina to demonstrate environmentally superior technology (EST) that could replace traditional anaerobic lagoon treatment. The system combined liquid–solids separation with nitrogen and phosphorus removal processes. Water quality was monitored at three sites: (i) the treatment plant as the raw manure liquid was depurated in the various processes, (ii) the converted lagoon as it was being cleaned up with the treated effluent, and (iii) an adjacent traditional anaerobic lagoon. The treatment plant removed 98% of total suspended solids (TSS), 76% of total solids (TS), 100% of 5‐d biochemical oxygen demand (BOD5), 98% of total Kjeldahl nitrogen (TKN) and NH4–N, 95% of total phosphorus (TP), 99% of Zn, and 99% of Cu. The quality of the liquid in the converted lagoon improved rapidly as cleaner effluent from the plant replaced anaerobic lagoon liquid. The converted lagoon liquid became aerobic (dissolved oxygen, 6.95 mg L−1; Eh, 342 mv) with the following mean reductions in the second year of the conversion: 73% of TSS, 40% of TS, 77% of BOD5, 85% of TKN, 92% of NH4–N, 38% of TP, 37% of Zn, and 39% of Cu. These findings overall showed that EST can have significant positive impacts on the environment and on the livestock industries.
Reuse of Urban Runoff in Australia: A Review of Recent Advances and Remaining Challenges
Authors: Fletcher Tim D. , Deletic Ana , Mitchell V. Grace , Hatt Belinda E.
Published: September 2008

The degradation of aquatic ecosystems due to hydrologic and water quality impacts of urbanization, combined with increasing water scarcity, has generated increasing interest in the harvesting of urban storm water. This paper reviews the rationale for integrated storm water treatment and harvesting and synthesizes recent advances and trends and knowledge gaps that limit its application. Storm water harvesting is shown to be a viable alternative water supply and to provide a potential solution to the increases in runoff frequency and peak flows that occur as a result of catchment urbanization. In general, treatment technologies for storm water harvesting have been adapted from existing “water‐sensitive urban design” approaches, with limited use of traditional water supply and wastewater technologies. Risk management is often lacking, in part due to a lack of relevant guidance. Reported performance shows variable levels of potable water savings, with cases of up to 100% substitution recorded. Costs of storm water harvesting systems are shown to be inversely related to their scale. The limited cost data show the importance of context, with the harvested water costing more or less than alternative supplies, depending on the cost of the alternative. Limited data exist on environmental benefits, such as reductions in pollutant loads and flow peaks. Implementation of storm water harvesting systems is impeded by inadequate data on risk, lifecycle costs, externalities, and water–energy tradeoffs. Furthermore, retrofit of storm water harvesting into existing urban areas is proving to be a challenge, creating an urgent need for specific technologies for use in retrofit situations.
Cumulative Soil Chemistry Changes from Land Application of Saline–Sodic Waters
Authors: Ganjegunte Girisha K. , King Lyle A. , Vance George F.
Published: September 2008

Management of large volumes (60,000 ha‐m) of co‐production water associated with coal bed natural gas (CBNG) water extraction is a potential concern in the Powder River Basin (PRB) of Wyoming and Montana due to elevated water salinity and sodicity levels. Land application of saline–sodic CBNG water is a common water management method being practiced in the PRB, which can result in deterioration in soil quality. The objective of this study was to evaluate effects from 1 to 4 yr of land application with CBNG water on soil chemical properties at six study sites (fine to loamy, mixed to smectitic, mesic, Ustic Ardisols and Entisols) in the Wyoming PRB region. Changes in chemistry of soils collected from six depths irrigated with CBNG water were compared with representative nonirrigated soils. Applications of CBNG water significantly increased soil EC, SAR, and ESP values (up to 21, 74, and 24 times, respectively) compared with nonirrigated soils. Differences in soil chemical properties between an irrigated and nonirrigated coarse‐textured soil were less than that of fine‐textured soils, emphasizing texture as an important factor for salinity buildup. Pretreatment of CBNG water using a sulfur burner and application of gypsum and elemental S soil amendments reduced soil pH but did not prevent the build‐up of salts and sodium. Study results suggest that current CBNG water management strategies are not as effective as projected. Additional research is needed to develop management strategies appropriate for mitigating adverse effects of CBNG water irrigation.
Soil and Plant Responses from Land Application of Saline–Sodic Waters: Implications of Management
Authors: Vance George F. , King Lyle A. , Ganjegunte Girisha K.
Published: September 2008

Land application of co‐produced waters from coalbed natural gas (CBNG) wells is one management option used in the Powder River Basin (PRB) of Wyoming and Montana. Unfortunately, the co‐produced CBNG waters may be saline and/or sodic. The objective of this study was to examine the effects of irrigation with CBNG waters on soils and plants in the PRB. Soil properties and vegetation responses resulting from 1 to 4 yr of saline‐sodic water (electrical conductivity [EC], 1.6–4.8 dS m−1; sodium adsorption ratio [SAR], 17–57 mmol1/2 L−1/2) applications were studied during 2003 and 2004 field seasons on sites (Ustic Torriorthent, Haplocambid, Haplargid, and Paleargid) representing native range grasslands, seeded grass hayfields, and alfalfa hayfields. Parameters measured from each irrigated site were compared directly with representative non‐irrigated sites. Soil chemical and physical parameters, including pH, EC, SAR, exchangeable sodium percent, texture, bulk density, infiltration, and Darcy flux rates, were measured at various depth intervals to 120 cm. Multiple‐year applications of saline‐sodic water produced consistent trends of increased soil EC and SAR values to depths of 30 cm, reduced surface infiltration rates, and lowered Darcy flux rates to 120 cm. Significant differences (p ≤ 0.05) were determined between irrigated and non‐irrigated areas for EC, SAR, infiltration rates, and Darcy flux (p ≤ 0.10) at most sites. Saline‐sodic CBNG water applications significantly increased native perennial grass biomass production and cover on irrigated as compared with non‐irrigated sites; however, overall species evenness decreased. Biological effects were variable and complex, reflecting site‐specific conditions and water and soil management strategies.
Feasibility of Irrigating Pickleweed (Salicornia bigeloviiTorr) with Hyper‐saline Drainage Water
Authors: Grattan S. R. , Benes S. E. , Peters D. W. , Diaz F.
Published: September 2008

Reuse of drainage water (DW) for irrigation reduces the volume of DW requiring treatment or disposal. We conducted a greenhouse study to evaluate the performance of the halophyteSalicornia bigeloviiTorr. when irrigated with hyper‐saline DW and seawater (SW) treatments, ranging from 1/3 strength to full strength (18–49 dS m−1), in a sand‐culture system. Results indicate thatSalicorniagrows well over the entire range of iso‐osmotic SW and DW salinity treatments. Moreover, when boron (B) was added to SW treatments to concentrations equivalent to that of corresponding 1/3‐ and 2/3‐strength DW treatments (i.e., 9 and 17 mg L−1), growth was not affected, and tissue B concentrations were <150 mg kg−1dry wt. However, when plants were irrigated with synthetic DW where B was reduced to solution culture levels (0.5–1.0 mg L−1), plants generally performed worse than when irrigated with actual DW high in B at the same salinity level. Evapotranspiration (ET) rates exceeded that lost from an evaporation pan from 1.5 to 2.5 times. Using a method accounting for changes in the isotopic signature of water in the reservoir due to evaporation, we estimated that high ET rates were due primarily to high transpiration rates (>78% of ET). The salt content in the tissue was very high (ash content 43–52%), but ionic composition in the shoot tissue reflected that of the treatment water used to irrigate the plants. These data indicate that hyper‐saline DW, characteristic of California's San Joaquin Valley, can be used to irrigateSalicorniaand substantially reduce drainage volumes.
Degraded Water Reuse: An Overview
Authors: O'Connor G. A. , Elliott H. A. , Bastian R. K.
Published: September 2008

Communities around the world face increasingly severe fresh water supply shortages, largely due to expanding populations and associated food supply, economic development, and health issues. Intentional reuse of degraded waters (e.g., wastewater effluents, irrigation return flows, concentrated animal feeding operations [CAFO] effluents, stormwater, and graywater) as substitutes for fresh waters could be one solution to the challenge. We describe the various degraded water types and reuse options and limitations and restrictions to their use. Emphasis is given to reuse scenarios involving degraded water applications to soil. The potential for degraded water reuse is enormous, but significant barriers exist to widespread adoption. Barriers include research questions (some addressable by traditional soil science approaches, but others requiring novel techniques and advanced instrumentation), the lack of unifying national regulations, and public acceptance. Educational programs, based on hard science developed from long‐term field studies, are imperative to convince the public and elected officials of the wisdom and safety of reusing degraded waters.
Infiltration into Cropped Soils: Effect of Rain and Sodium Adsorption Ratio–Impacted Irrigation Water
Authors: Suarez Donald L. , Wood James D. , Lesch Scott M.
Published: September 2008

The sodium adsorption ratio (SAR) and salinity criteria for water suitability for irrigation have been developed for conditions where irrigation water is the only water source. It is not clear that these criteria are applicable to environments where there is a combination of rain and irrigation during the growing season. The interaction of rainfall with irrigation water is expected to result in increased sodicity hazard because of the low electrical conductivity of rain. In this study we examined the effects of irrigation waters of SAR 2, 4, 6, 8, and 10 mmol1/2 L−1/2 and electrical conductivities of 1 and 2 dS m−1 on the infiltration rate of two soils with alternating cycles of rain (simulated with a rainfall sprinkler) and irrigation water, separated by drying cycles. The infiltration rate of surface samples from two soils, Kobase silty clay (fine, smectitic, frigid, Torrertic Haplustept) and Glendive very fine sandy loam (coarse‐loamy, mixed superactive, calcareous, frigid Aridic Ustifluvent) were evaluated under alfalfa (Medicago sativa) cropped conditions for over 140 d and under full canopy cover. Reductions in infiltration were observed for both soils for SAR above 2, and the reductions became more severe with increasing SAR. Saturated hydraulic conductivity measurements taken from undisturbed cores at the end of the experiment were highly variable, suggesting that in situ infiltration measurements may be preferred when evaluating SAR effects.
Near‐Decadal Changes in Nitrate and Pesticide Concentrations in the South Platte River Alluvial Aquifer, 1993–2004
Authors: Paschke Suzanne S. , Schaffrath Keelin R. , Mashburn Shana L.
Published: September 2008

The lower South Platte River basin of Colorado and Nebraska is an area of intense agriculture supported by surface‐water diversions from the river and ground‐water pumping from a valley‐fill alluvial aquifer. Two well networks consisting of 45 wells installed in the South Platte alluvial aquifer were sampled in the early 1990s and again in the early 2000s to examine near‐decadal ground‐water quality changes in irrigated agricultural areas. Ground‐water age generally increases and dissolved‐oxygen content decreases with distance along flow paths and with depth below the water table, and denitrification is an important natural mitigation mechanism for nitrate in downgradient areas. Ground‐water travel time from upland areas to the river ranges from 12 to 31 yr on the basis of apparent ground‐water ages. Ground‐water nitrate concentrations for agricultural land‐use wells increased significantly for oxidized samples over the decade, and nitrogen isotope ratios for oxidized samples indicate synthetic fertilizer as the predominant nitrate source. Ground‐water concentrations of atrazine, DEA, and prometon decreased significantly. The decrease in pesticide concentrations and a significant increase in the ratio of DEA to atrazine suggest decreases in pesticide concentrations are likely caused by local decreases in application rates and/or degradation processes and that atrazine degradation is promoted by oxidizing conditions. The difference between results for oxidizing and nitrate‐reducing conditions indicates redox state is an important variable to consider when evaluating ground‐water quality trends for redox‐sensitive constituents such as nitrate and pesticides in the South Platte alluvial aquifer.
Temporal Trends in Nitrate and Selected Pesticides in Mid‐Atlantic Ground Water
Authors: Debrewer Linda M. , Ator Scott W. , Denver Judith M.
Published: September 2008

Evaluating long‐term temporal trends in regional ground‐water quality is complicated by variable hydrogeologic conditions and typically slow flow, and such trends have rarely been directly measured. Ground‐water samples were collected over near‐decadal and annual intervals from unconfined aquifers in agricultural areas of the Mid‐Atlantic region, including fractured carbonate rocks in the Great Valley, Potomac River Basin, and unconsolidated sediments on the Delmarva Peninsula. Concentrations of nitrate and selected pesticides and degradates were compared among sampling events and to apparent recharge dates. Observed temporal trends are related to changes in land use and chemical applications, and to hydrogeology and climate. Insignificant differences in nitrate concentrations in the Great Valley between 1993 and 2002 are consistent with relatively steady fertilizer application during respective recharge periods and are likely related to drought conditions in the later sampling period. Detecting trends in Great Valley ground water is complicated by long open boreholes characteristic of wells sampled in this setting which facilitate significant ground‐water mixing. Decreasing atrazine and prometon concentrations, however, reflect reported changes in usage. On the Delmarva Peninsula between 1988 and 2001, median nitrate concentrations increased 2 mg per liter in aerobic ground water, reflecting increasing fertilizer applications. Correlations between selected pesticide compounds and apparent recharge date are similarly related to changing land use and chemical application. Observed trends in the two settings demonstrate the importance of considering hydrogeology and recharge date along with changing land and chemical uses when interpreting trends in regional ground‐water quality.