bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Land Use on Soil Respiration
Authors: Carlisle Eli A. , Steenwerth Kerri L. , Smart David R.
Published: July 2006

We examined constraints on soil CO2 respiration in natural oak woodlands, and adjacent vineyards that were converted approximately 30 yr ago from oak woodlands, in the Oakville Region of Napa Valley, California. All sites were located on the same soil type, a Bale (variant) gravelly loam (fine‐loamy, mixed, superactive, thermic Cumulic Ultic Haploxeroll) and dominated by C3 vegetation. Seasonal soil CO2 efflux was greatest at the oak woodland sites, although during the summer drought the rates of soil CO2 efflux measured from oak sites were generally similar to those measured from the vineyards. Soil profile CO2 concentrations at the oak woodland sites were lower below 15 cm despite higher CO2 efflux rates. Soil gas diffusion coefficients for oak sites were larger than for vineyard sites, and this indicated that the apparent discrepancy in soil profile carbon dioxide concentration ([CO2]) may be caused by a diffusion limitation. Soil profile [CO2] and δ13C values showed substantial temporal changes over the course of a year. Vineyard soil CO2 was more depleted in 13CO2 below 25 cm in the soil profile during the active growing season as indicated by more negative δ13C ratios. This result indicated that different C sources were being oxidized in vineyard soils. Annual C losses were less from vineyard soils (7.02 ± 0.58 Mg C ha−1 yr−1) as compared to oak soils (15.67 ± 1.44 Mg C ha−1 yr−1), and both were comparable to losses reported in previous investigations.
DAYCENT National‐Scale Simulations of Nitrous Oxide Emissions from Cropped Soils in the United States
Authors: Del Grosso S. J. , Parton W. J. , Mosier A. R. , Walsh M. K. , Ojima D. S. , Thornton P. E.
Published: July 2006

Until recently, Intergovernmental Panel on Climate Change (IPCC) emission factor methodology, based on simple empirical relationships, has been used to estimate carbon (C) and nitrogen (N) fluxes for regional and national inventories. However, the 2005 USEPA greenhouse gas inventory includes estimates of N2O emissions from cultivated soils derived from simulations using DAYCENT, a process‐based biogeochemical model. DAYCENT simulated major U.S. crops at county‐level resolution and IPCC emission factor methodology was used to estimate emissions for the approximately 14% of cropped land not simulated by DAYCENT. The methodology used to combine DAYCENT simulations and IPCC methodology to estimate direct and indirect N2O emissions is described in detail. Nitrous oxide emissions from simulations of presettlement native vegetation were subtracted from cropped soil N2O to isolate anthropogenic emissions. Meteorological data required to drive DAYCENT were acquired from DAYMET, an algorithm that uses weather station data and accounts for topography to predict daily temperature and precipitation at 1‐km2 resolution. Soils data were acquired from the State Soil Geographic Database (STATSGO). Weather data and dominant soil texture class that lie closest to the geographical center of the largest cluster of cropped land in each county were used to drive DAYCENT. Land management information was implemented at the agricultural–economic region level, as defined by the Agricultural Sector Model. Maps of model‐simulated county‐level crop yields were compared with yields estimated by the USDA for quality control. Combining results from DAYCENT simulations of major crops and IPCC methodology for remaining cropland yielded estimates of approximately 109 and approximately 70 Tg CO2 equivalents for direct and indirect, respectively, mean annual anthropogenic N2O emissions for 1990–2003.
Carbon Banks
Authors: Esuola Adeyemi G. , Weersink Alfons
Published: July 2006

Carbon sequestration is one of the options that can be used to reduce atmospheric carbon, but its use in an offset market is complicated by the temporary nature of sequestered carbon and the risks associated with carbon release and price. In this paper a carbon bank is proposed to handle these problems. The bank is both an aggregator and a risk bearer. Sink generators deposit their credits with the bank and are paid for maintaining their “savings” with the bank. The carbon bank is also the source where large‐scale emitters can come and buy either a temporary or permanent credit and pay the bank in return for the credit and services provided. The advantages of the bank over alternative institutional designs include lower transaction costs, flexible carbon credits and price, and lower risk to risk‐averse parties. The carbon bank could be an effective means to deal with many of the unresolved issues within the forthcoming Canadian offset system.
Long‐Term Cropping System Effects on Carbon Sequestration in Eastern Oregon
Authors: Machado Stephen , Rhinhart Karl , Petrie Steve
Published: July 2006

Soil organic carbon (SOC) has beneficial effects on soil quality and productivity. Cropping systems that maintain and/or improve levels of SOC may lead to sustainable crop production. This study evaluated the effects of long‐term cropping systems on C sequestration. Soil samples were taken at 0‐ to 10‐, 10‐ to 20‐, 20‐ to 30‐, and 30‐ to 40‐cm soil depth profiles from grass pasture (GP), conventional tillage (CT) winter wheat (Triticum aestivumL.)–fallow (CTWF), and fertilized and unfertilized plots of continuous winter wheat (WW), spring wheat (SW), and spring barley (Hordeum vulgareL.) (SB) monocultures under CT and no‐till (NT). The samples were analyzed for soil organic matter (SOM) and SOC was derived. Ages of experiments ranged from 6 to 73 yr. Compared to 1931 SOC levels (initial year), CTWF reduced SOC by 9 to 12 Mg ha−1in the 0‐ to 30‐cm zone. Grass pasture increased SOC by 6 Mg ha−1in the 0‐ to 10‐cm zone but decreased SOC by 3 Mg ha−1in the 20‐ to 30‐cm zone. Continuous CT monocultures depleted SOC in the top 0‐ to 10‐cm zone and the bottom 20‐ to 40‐cm zone but maintained SOC levels close to 1931 SOC levels in the 10‐ to 20‐cm layer. Continuous NT monocultures accumulated more SOC in the 0‐ to 10‐cm zone than in deeper zones. Total SOC (0‐ to 40‐cm zone) was highest under GP and continuous cropping and lowest under CTWF. Fertilizer increased total SOC only under CTWW and CTSB by 13 and 7 Mg ha−1in 13 yr, respectively. Practicing NT for only 6 yr had started to reverse the effect of 73 yr of CTWF. Compared to CTWF, NTWW and NTSW sequestered C at rates of 2.6 and 1.7 Mg ha−1yr−1, respectively, in the 0‐ to 40‐cm zone. This study showed that the potential to sequester C can be enhanced by increasing cropping frequency and eliminating tillage.
Carbon Storage by Urban Soils in the United States
Authors: Pouyat Richard V. , Yesilonis Ian D. , Nowak David J.
Published: July 2006

We used data available from the literature and measurements from Baltimore, Maryland, to (i) assess inter‐city variability of soil organic carbon (SOC) pools (1‐m depth) of six cities (Atlanta, Baltimore, Boston, Chicago, Oakland, and Syracuse); (ii) calculate the net effect of urban land‐use conversion on SOC pools for the same cities; (iii) use the National Land Cover Database to extrapolate total SOC pools for each of the lower 48 U.S. states; and (iv) compare these totals with aboveground totals of carbon storage by trees. Residential soils in Baltimore had SOC densities that were approximately 20 to 34% less than Moscow or Chicago. By contrast, park soils in Baltimore had more than double the SOC density of Hong Kong. Of the six cities, Atlanta and Chicago had the highest and lowest SOC densities per total area, respectively (7.83 and 5.49 kg m−2). On a pervious area basis, the SOC densities increased between 8.32 (Oakland) and 10.82 (Atlanta) kg m−2 In the northeastern United States, Boston and Syracuse had 1.6‐fold less SOC post‐ than in pre‐urban development stage. By contrast, cities located in warmer and/or drier climates had slightly higher SOC pools post‐ than in pre‐urban development stage (4 and 6% for Oakland and Chicago, respectively). For the state analysis, aboveground estimates of C density varied from a low of 0.3 (WY) to a high of 5.1 (GA) kg m−2, while belowground estimates varied from 4.6 (NV) to 12.7 (NH) kg m−2 The ratio of aboveground to belowground estimates of C storage varied widely with an overall ratio of 2.8. Our results suggest that urban soils have the potential to sequester large amounts of SOC, especially in residential areas where management inputs and the lack of annual soil disturbances create conditions for net increases in SOC. In addition, our analysis suggests the importance of regional variations of land‐use and land‐cover distributions, especially wetlands, in estimating urban SOC pools.
Net Global Warming Potential and Greenhouse Gas Intensity in Irrigated Cropping Systems in Northeastern Colorado
Authors: Mosier Arvin R. , Halvorson Ardell D. , Reule Curtis A. , Liu Xuejun J.
Published: July 2006

The impact of management on global warming potential (GWP), crop production, and greenhouse gas intensity (GHGI) in irrigated agriculture is not well documented. A no‐till (NT) cropping systems study initiated in 1999 to evaluate soil organic carbon (SOC) sequestration potential in irrigated agriculture was used in this study to make trace gas flux measurements for 3 yr to facilitate a complete greenhouse gas accounting of GWP and GHGI. Fluxes of CO2, CH4, and N2O were measured using static, vented chambers, one to three times per week, year round, from April 2002 through October 2004 within conventional‐till continuous corn (CT‐CC) and NT continuous corn (NT‐CC) plots and in NT corn–soybean rotation (NT‐CB) plots. Nitrogen fertilizer rates ranged from 0 to 224 kg N ha−1 Methane fluxes were small and did not differ between tillage systems. Nitrous oxide fluxes increased linearly with increasing N fertilizer rate each year, but emission rates varied with years. Carbon dioxide efflux was higher in CT compared to NT in 2002 but was not different by tillage in 2003 or 2004. Based on soil respiration and residue C inputs, NT soils were net sinks of GWP when adequate fertilizer was added to maintain crop production. The CT soils were smaller net sinks for GWP than NT soils. The determinant for the net GWP relationship was a balance between soil respiration and N2O emissions. Based on soil C sequestration, only NT soils were net sinks for GWP. Both estimates of GWP and GHGI indicate that when appropriate crop production levels are achieved, net CO2 emissions are reduced. The results suggest that economic viability and environmental conservation can be achieved by minimizing tillage and utilizing appropriate levels of fertilizer.
Potential of Carbon Accumulation in No‐Till Soils with Intensive Use and Cover Crops in Southern Brazil
Authors: Amado Telmo Jorge Carneiro , Bayer Cimélio , Conceição Paulo Cesar , Spagnollo Evandro , de Campos Ben‐Hur Costa , da Veiga Milton
Published: July 2006

The area under no‐till (NT) in Brazil reached 22 million ha in 2004–2005, of which approximately 45% was located in the southern states. From the 1970s to the mid‐1980s, this region was a source of carbon dioxide to the atmosphere due to decrease of soil carbon (C) stocks and high consumption of fuel by intensive tillage. Since then, NT has partially restored the soil C lost and reduced the consumption of fossil fuels. To assess the potential of C accumulation in NT soils, four long‐term experiments (7–19 yr) in subtropical soils (Paleudult, Paleudalf, and Hapludox) varying in soil texture (87–760 g kg−1of clay) in agroecologic southern Brazil zones (central region, northwest basaltic plateau in Rio Grande Sul, and west basaltic plateau in Santa Catarina) and with different cropping systems (soybean and maize) were investigated. The lability of soil organic matter (SOM) was calculated as the ratio of total organic carbon (TOC) to particulate organic carbon (POC), and the role of physical protection on stability of SOM was evaluated. In general, TOC and POC stocks in native grass correlated closely with clay content. Conversely, there was no clear effect of soil texture on C accumulation rates in NT soils, which ranged from 0.12 to 0.59 Mg ha−1yr−1The C accumulation was higher in NT than in conventional‐till (CT) soils. The legume cover crops pigeon pea [Cajanus cajan(L.) Millsp] and velvet beans (Stizolobium cinereumPiper & Tracy) in NT maize cropping systems had the highest C accumulation rates (0.38–0.59 Mg ha−1yr−1). The intensive cropping systems also were effective in increasing the C accumulation rates in NT soils (0.25–0.34 Mg ha−1yr−1) when compared to the double‐crop system used by farmers. These results stress the role of N fixation in improving the tropical and subtropical cropping systems. The physical protection of SOM within soil aggregates was an important mechanism of C accumulation in the sandy clay loam Paleudult under NT. The cropping system and NT effects on C stocks were attributed to an increase in the lability of SOM, as evidenced by the higher POC to TOC ratio, which is very important to C and energy flux through the soil.
Simulating Long‐Term and Residual Effects of Nitrogen Fertilization on Corn Yields, Soil Carbon Sequestration, and Soil Nitrogen Dynamics
Authors: He X. , Izaurralde R. C. , Vanotti M. B. , Williams J. R. , Thomson A. M.
Published: July 2006

Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO2 and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958–1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha−1 (1958), increased to 92 kg ha−1 (1963), and reached 140 kg ha−1 (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha−1 Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958–1983 decreased as N rate increased (LTN1 = −5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985–1991 were larger than during the first period. Simulated and observed mean yields during 1958–1991 were highly correlated (R2 = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from −5.8 to 0.5% in 1984 and from −5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.
Soil Carbon and Nitrogen Storage in Response to Fire in a Temperate Mixed‐Grass Savanna
Authors: Dai X. , Boutton T. W. , Hailemichael M. , Ansley R. J. , Jessup K. E.
Published: July 2006

Vegetation fires may alter the quantity and quality of organic matter inputs to soil, rates of organic matter decay, and environmental factors that influence those processes. However, few studies have evaluated the impacts of this land management technique on soil organic carbon (SOC) and total N in grasslands and savannas. We evaluated the impact of repeated fires and their season of occurrence on SOC and total N storage in a temperate mixed‐grass–mesquite savanna where fire is used to control woody plant encroachment. Four fire treatments varying in season of occurrence were examined: summer only (SF), winter only (WF), alternate summer and winter fires (SWF), and unburned controls. In each treatment, soils were sampled to 1 m under three vegetation types: C3grasses, C4grasses, and mesquite trees. The SOC storage at 0 to 20 cm was significantly greater in SF (2693 g C m−2) and SWF (2708 g C m−2) compared to WF (2446 g C m−2) and controls (2445 g C m−2). The SWF treatment also increased soil total N (271 g N m−2) relative to all other treatments (228–244 g N m−2) at 0 to 20 cm. Fire had no effect on SOC or total N at depths of >20 cm. Vegetation type had no significant influence on SOC or total N stocks. The δ13C value of SOC was not affected by fire, but increased from −21‰ at 0 to 10 cm to −15‰ at depths of >20 cm indicating that all treatments were once dominated by C4grasses before woody plant encroachment during the past century. These results have implications for scientists, land managers, and policymakers who are now evaluating the potential for land uses to alter ecosystem C storage and influence atmospheric CO2concentrations and global climate.
Effect of Chemical and Microbial Amendment on Phosphorus Runoff from Composted Poultry Litter
Authors: DeLaune P. B. , Moore P. A. , Lemunyon J. L.
Published: July 2006

Environmental impacts of composting poultry litter with chemical amendments at the field scale have not been well quantified. The objectives of this study were to measure (i) P runoff and (ii) forage yield and N uptake from small plots fertilized with composted and fresh poultry litter. Two composting studies, aerated using mechanical turning, were conducted in consecutive years. Composted litter was collected at the completion of each study for use in runoff studies. Treatments in runoff studies included an unfertilized control, fresh (uncomposted) poultry litter, and litter composted with no amendment, H3PO4, alum, or a microbial mixture. An additional treatment, litter composted with alum plus the microbial mixture, was evaluated during the first year. Fertilizer treatments were applied at rates equivalent to 8.96 Mg ha−1 and rainfall simulators were used to produce a 5 cm h−1 storm event. Composted poultry litter, regardless of treatment, had higher total P concentrations than fresh poultry litter. Composting poultry litter resulted in reductions of N/P ratios by as much as 51%. Soluble reactive P concentrations were lowest in alum‐treated compost, which reduced soluble P concentrations in runoff water by as much as 84%. Forage yields and N uptake were greatest from plots fertilized with fresh poultry litter. Composting poultry litter without the addition of C sources can increase P concentrations in the end product and surface runoff. This study also indicated that increased rates of composted poultry litter would be required to meet equivalent N rates supplied by fresh poultry litter.
Accuracy and Performance of Three Water Quality Models for Simulating Nitrate Nitrogen Losses under Corn
Authors: Jabro J. D. , Jabro A. D. , Fox R. H.
Published: July 2006

Simulation models can be used to predict N dynamics in a soil‐water–plant system. The simulation accuracy and performance of three models: LEACHM (Leaching Estimation And CHemistry Model), NCSWAP (Nitrogen and Carbon cycling in Soil, Water And Plant), and SOILN to predict NO3–N leaching were evaluated and compared to field data from a 5‐yr experiment conducted on a Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf). Nitrate N losses past 1.2 m from N‐fertilized and manured corn (Zea mays L.) were measured with zero‐tension pan lysimeters for 5 yr. The models were calibrated using 1989–1990 data and validated using 1988–1989, 1990–1991, 1991–1992, and 1992–1993 NO3–N leaching data. Statistical analyses indicated that LEACHM, NCSWAP, and SOILN models were able to provide accurate simulations of annual NO3–N leaching losses below the 1.2‐m depth for 8, 9, and 7 of 10 cases, respectively, in the validation years. The inaccuracy in the models' annual simulations for the control and manure treatments seems to be related to inadequate description of processes of N and C transformations in the models' code. The overall performance and accuracy of the SOILN model were worse than those of LEACHM and NCSWAP. The root mean square error (RMSE) and modeling efficiency (ME) were 10.7 and 0.9, 9.5 and 0.93, and 20.7 and 0.63 for LEACHM, NCSWAP, and SOILN, respectively. Overall, the three models have the potential to predict NO3–N losses below 1.2‐m depth from fertilizer and manure nitrogen applied to corn without recalibration of models from year to year.
An approach for developing a national estimate of waterborne disease due to drinking water and a national estimate model application
Authors: Messner Michael , Shaw Susan , Regli Stig , Rotert Ken , Blank Valerie , Soller Jeff
Published: July 2006

In this paper, the US Environmental Protection Agency (EPA) presents an approach and a national estimate of drinking water related endemic acute gastrointestinal illness (AGI) that uses information from epidemiologic studies. There have been a limited number of epidemiologic studies that have measured waterborne disease occurrence in the United States. For this analysis, we assume that certain unknown incidence of AGI in each public drinking water system is due to drinking water and that a statistical distribution of the different incidence rates for the population served by each system can be estimated to inform a mean national estimate of AGI illness due to drinking water. Data from public water systems suggest that the incidence rate of AGI due to drinking water may vary by several orders of magnitude. In addition, data from epidemiologic studies show AGI incidence due to drinking water ranging from essentially none (or less than the study detection level) to a rate of 0.26 cases per person-year. Considering these two perspectives collectively, and associated uncertainties, EPA has developed an analytical approach and model for generating a national estimate of annual AGI illness due to drinking water. EPA developed a national estimate of waterborne disease to address, in part, the 1996 Safe Drinking Water Act Amendments. The national estimate uses best available science, but also recognizes gaps in the data to support some of the model assumptions and uncertainties in the estimate. Based on the model presented, EPA estimates a mean incidence of AGI attributable to drinking water of 0.06 cases per year (with a 95% credible interval of 0.02–0.12). The mean estimate represents approximately 8.5% of cases of AGI illness due to all causes among the population served by community water systems. The estimated incidence translates to 16.4 million cases/year among the same population. The estimate illustrates the potential usefulness and challenges of the approach, and provides a focus for discussions of data needs and future study designs. Areas of major uncertainty that currently limit the usefulness of the approach are discussed in the context of the estimate analysis.
Workshop summary: estimating waterborne disease risks in the United States
Authors: Craun Gunther F. , Calderon Rebecca L.
Published: July 2006

A workshop was held in Atlanta on July 7–8, 2005, to evaluate the epidemiologic and other information available for estimating endemic waterborne illness risks in the United States. Each paper written for this special issue was discussed and fourteen recommendations were made based on the discussion. In addition, seven major data gaps were identified as being key to reducing the uncertainty associated with a calculation of a national estimate. This summary is provided to help regulatory officials, public health professionals, and others better understand the health measures being estimated and adequacy of the current risk information. The summary also provides a blueprint for researchers interested in studying the endemic and epidemic risks of microbes in drinking water.
Privatisation of urban water service provision: the Kenyan experiment
Authors: K'Akumu O. A. , Appida P. O.
Published: July 2006

One of the services that have been poorly provided in the urban areas in Kenya is water and sanitation. There are many reasons, which can be attributed to poor provision of water and sanitation as undertaken by the local authorities in Kenya.

The path to remedy the poor provision of water and sanitation has been charted in privatisation in the form of commercialisation. Commercialisation in Kenya was first implemented on an experimental basis in three urban areas: Nyeri, Eldoret and Nakuru. This involved formation of a publicly owned water company as an agent of the local authority. The companies formed as a result were set up and operated according to the provisions of the Companies Act chapter 486 of the Laws of Kenya. This paper looks at the genesis of privatisation of water services based on the contributions of GTZ, UWASAM and KFW to an experiment in formulating and implementing privatisation in the three urban areas. The outcome of the experiment is then compared to the current on-going exercise of water privatisation by local authorities.

Privatisation of water and sanitation services is expected to solve the problem of poor and inadequate service provision that hitherto characterised urban areas. It would do this by achieving its goals of decentralisation and economic viability. However, the outcome of the experiment indicated that privatisation failed to achieve these two fundamental goals. For that matter, privatisation failed to meet its intended objectives of solving the woes of service provision in urban areas.

A close examination of the current privatisation indicates that the operation has again failed to achieve its fundamental goals of decentralisation and economic viability. The failure of the current exercise in meeting the objectives of ridding the urban areas of water woes can therefore be predicted on this basis.
Salinisation in irrigated agriculture in Pakistan: mistaken predictions
Authors: Kijne J. W.
Published: July 2006

This paper revisits data and information that was collected through field studies by the International Irrigation Management Institute (IIMI) in Pakistan in the early 1990s. Analysis of available data led in 1996 to the publication of an IIMI research report (Kijne, 1996) whose main conclusion was that current cropping intensities and groundwater usage in Pakistan's irrigated agriculture were not sustainable. Ten years on there is no evidence that this prediction came true and the paper questions why those predictions were wrong. Based on more recent field data and information, the water and salt balances for one of the experimental sites are recalculated.

Reasons for the mistaken predictions include: lack of understanding of farmers' reactions to signs of salinity in their fields, insufficient knowledge of the actual groundwater usage and underestimating the leaching fractions. The difficulty in accurately determining the actual leaching fraction from easily measurable field parameters affects the prediction of salt accumulation in the soil. The conclusion that current practices are all right is conditional on maintaining sufficient downward fluxes in the soil profile. The paper ends with some general reflections on predictions for the future.
Variability control: key to regulatory compliance and sustainability goals
Authors: Englande A.J. , Eckenfelder W.W. , Jin G.
Published: July 2006

The focus of this paper is on variability concerns in wastewater treatment and approaches to control unacceptable fluctuations in effluent quality. Areas considered include: factors contributing to variability in both waste loads and process technology performance; variability assessment; control of variability employing the process best management practice (BMP); design/operation of biological waste treatment technologies for variability reduction; and modelling to enhance process control.
Cleaner production and methodological proposal of eco-efficiency measurement in a Mexican petrochemical complex
Authors: Morales M.A. , Herrero V.M. , Martínez S.A. , Rodríguez M.G. , Valdivieso E. , Garcia G. , de los Ángeles Elías Ma.
Published: July 2006

In the frame of the Petróleos Mexicanos Institutional Program for Sustainable Development, processes were evaluated in the manufacture operation of the petrochemical industry, with the purpose of reducing their ecological fingerprint. Thirteen cleaner production opportunities were registered in six process plants: ethylene oxide and glycols, acetaldehyde, ethylene, high density polyethylene, polypropylene switch and acrylonitrile, and 45 recommendations in the waste water treatment plant. Morelos is the second most important petrochemical complex in the Mexican and Latin American petrochemical industry. A tool was developed to obtain eco-efficiency indicators in operation processes, and as a result, potential savings were obtained based on best performance, as well as the integrated distribution of Sankey diagrams. Likewise, a mechanism of calculation to obtain economic savings based on the reduction of residues during the whole productive process is proposed. These improvement opportunities and recommendations will result in economic and environmental benefits minimising the use of water, efficient use of energy, raw materials and reducing residues from source, generating less environmental impacts during the process.
Effects of antibacterial agents, levofloxacin and clarithromycin, on aquatic organisms
Authors: Yamashita N. , Yasojima M. , Nakada N. , Miyajima K. , Komori K. , Suzuki Y. , Tanaka H.
Published: July 2006

Contamination of surface waters by pharmaceutical chemicals is an emerging environmental problem. This study evaluated the toxic effects of the antibacterial agents levofloxacin (LVFX) and clarithromycin (CAM), which are widely used in Japan, on aquatic organisms. Ecotoxicity tests using a bacterium, alga and crustacean were conducted. Microtox test using a marine fluorescent bacterium showed that LVFX and CAM have no acute toxicity to the bacterium. From the results of the Daphnia immobilisation test, LVFX and CAM did not show acute toxicity to the crustacean. Meanwhile, an algal growth inhibition test revealed that LVFX and CAM have high toxicity to the microalga. The phytotoxicity of CAM was about 100-fold higher than that of LVFX from a comparison of EC50 (median effective concentration) value. From the Daphnia reproduction test, LVFX and CAM also showed chronic toxicity to the crustacean. Concentrations of LVFX and CAM in the aquatic environment were compared with PNEC (predicted no effect concentration) to evaluate the ecological risk. As a result, the ecological risk of LVFX is considered to be low, but that of CAM is higher, suggesting that CAM discharged into an aquatic environment after therapeutic use may affect organisms in the aquatic environment.
Study of different methods for enhancing the nitrate removal efficiency of a zero-valent metal process
Authors: Cheng S.F. , Huang C.Y. , Liu J.Y.
Published: July 2006

This study explores the effect of several enhancing methods, namely acid wash pretreatment, ultrasound treatment and addition of nickel catalyst on the nitrate removal efficiency of three zero-valent metals – iron, aluminium and zinc. It is hoped that by learning about the major reaction pathways of nitrate removal with zero-valent metals and the main factors influencing the reactivity of those zero-valent metals, optimum process conditions may be identified. The study results show that direct transfer of electrons is the major reaction pathway. Thus increasing a clean, fresh metal surface and decreasing the thickness of the diffusion layer to accelerate mass transfer are the main determinants of reaction rate. In the absence of a clean, fresh metal surface, the catalytic reaction of nickel becomes the primary removal pathway.
Photocatalytic oxidation of methyl ethyl ketone over sol-gel and commercial TiO2 for the improvement of indoor air
Authors: Raillard C. , Héquet V. , Le Cloirec P. , Legrand J.
Published: July 2006

This work focuses on the photocatalytic oxidation of gaseous methyl ethyl ketone chosen as a typical indoor air pollutant. Two types of TiO2 coatings were prepared and deposited on glass plates: one using the commercial Degussa P25 TiO2 and the other one by sol-gel method. The first objective of this study was to compare different ways of preparing thin films of sol-gel TiO2 coated on glass plates, taking into account their general aspect and their photocatalytic efficiency. Several parameters were tested, such as the stabilising agent, the glass type of the support, the number of coatings and the calcination temperature. One of the synthesised materials was then kept to carry out the following study. The study aimed to assess the influence of TiO2 coating types on the effect of water vapour. This was achieved by performing MEK photocatalytic degradation kinetics under two levels of humidity at a fixed temperature. Experimental results were then modelled by the Langmuir-Hinshelwood equation. The obtained parameters gave specific trends in function of the considered catalyst. The second part of this work was to identify MEK degradation byproducts during its photocatalytic oxidation. The main detected intermediate was acetaldehyde, followed by methyl formate. A MEK degradation pathway was then proposed.
Electrolytic degradation of biorefractory organics and ammonia in leachate from bioreactor landfill
Authors: Shao L. , He P. , Xue J. , Li G.
Published: July 2006

Electrochemical oxidation was applied to treat the effluent from bioreactor landfill with leachate recirculation, characterised as poor biodegradability and high NH3-N concentration. In this study, the effluent was electrolysed in a batch reactor with Ti/TiO2-IrO2-RuO2 anode and stainless steel cathode. The oxidation of dissolved organic matter (DOM) during electrolysis was evaluated based on the evolution of molecular weight grade, hydrophilic fractionation (humic acid, fulvic acid and hydrophilic fractions), specific ultraviolet absorbance (SUVA254) and AOX. The impact of the initial NH3-N concentration on the oxidation was discussed. The results showed that at a current density of 100 mA/cm2, electrolysis time of 1.5 h and electrode gap of 1 cm, NH3-N with an initial concentration of 1.2 g/L could be completely eliminated and 56% of COD with an initial concentration of 1.2 g/L could be removed, which illustrated that the electrolysis-produced chlorine preferentially oxidised ammonia. The electrolysis mainly resulted in the degradation of humic substances and other high molecular DOM, followed by the increase of BOD/COD ratio and decline of SUVA254 of the leachate. The current efficiencies for COD and ammonia oxidation gradually decreased during the electrolysis, with the latter obviously higher than the former. At the optimal electrolysis time of 1.5 h, NH3-N could be totally removed and the BOD/COD ratio could be enhanced to 0.3, which was also favourable to control the AOX at a reasonable level.
Microbial conversion of selected azo dyes and their breakdown products
Authors: Yemashova N. , Kalyuzhnyi S.
Published: July 2006

Four selected azo dyes (acid orange 6, acid orange 7, methyl orange and methyl red) were completely decolourised in the presence of anaerobic granular sludge, while only methyl red was degraded in aerobic conditions using a conventional activated sludge. Additional experiments with culture broth devoid of cells showed that anaerobic decolourisation of azo dyes was performed by extracellular reducing agents produced by anaerobic bacteria. This was further confirmed by abiotic experiments with sulphide and NADH. The presence of redox mediators such as riboflavin led to dramatic acceleration of the anaerobic biodecolourisation process. The azo dye reduction products were found to be sulphanilic acid and 4-aminoresorcinol for acid orange 6; sulphanilic acid and 1-amino-2-naphthol for acid orange 7; N,N-dimethyl-1,4-phenylenediamine and sulphanilic acid for methyl orange; and N,N-dimethyl-1,4-phenylenediamine and anthranilic acid for methyl red. Anaerobic toxicity assays showed that the azo dyes were more toxic than their breakdown products (aromatic amines), except 1-amino-2-naphthol. In the presence of activated sludge, only anthranilic acid was completely mineralised while sulphanilic acid was persistent. 4-aminoresorcinol, 1-amino-2-naphthol and N,N-dimethyl-1,4-phenylenediamine underwent autooxidation in aerobic conditions yielding coloured polymeric products. On the contrary, in the presence of granular methanogenic sludge, 4-aminoresorcinol, 1-amino-2-naphthol and anthranilic acid were quantitatively methanised, sulphanilic acid was partially (70%) mineralised while N,N-dimethyl-1,4-phenylenediamine was only demethylated producing 1,4-phenylenediamine as an end product.
Kinetics of the reaction of hypobromous acid and organic matters in water treatment processes
Authors: Echigo S. , Minear R.A.
Published: July 2006

The fate of bromine species from human activity is affected by the bromination reaction in water treatment processes. In this study, kinetic information of the reaction between hypobromous acid (HOBr) and seven different natural organic matters (NOM) was collected by sequential stopped-flow techniques. Multiple reaction phases were found in the reaction between HOBr and NOM. The number of reaction sites for the faster reaction phase ranged from 0.26 to 0.92 μmole (mg DOC)−1, and was correlated to both SUVA and specific phenolic content at pH 7.0. The apparent second-order rate constants for the faster reaction phase at pH 7.0 ranged from 5.4 × 105 to 1.4 × 106 M−1·s−1, indicating that vanillin-like structures are involved in this reaction phase.
Separation of THF and water by room temperature ionic liquids
Authors: Hu X. , Yu J. , Liu H.
Published: July 2006

Liquid–liquid equilibrium data are presented for mixtures of 1-(2-hydroxyethyl)-3-methyl-imidazolium chloride or tetrafluoroborate + tetrahydrofuran(THF) + water at 293.15 K. The data presented provides a valuable insight into how the environmentally friendly ionic liquid solvent can have the separation power of THF-water azeotropic systems. The sloping of the tie lines towards the THF vertex is investigated for mixtures of l-(2-hydroxyethyl)-3-methylimidazolium chloride (or tetrafluoroborate) + THF + water. Selectivity values, derived from the tie line data, indicate that these two ionic liquids are suitable solvents for the liquid–liquid extraction of water from THF.
Measurement and modelling of ordinary heterotrophic organism active biomass concentrations in anoxic/aerobic activated sludge mixed liquor
Authors: Lee B.J. , Wentzel M.C. , Ekama G.A.
Published: July 2006

Ordinary heterotrophic organism (OHO) active biomass (ZBH) is a key parameter in models for activated sludge systems, which defines quantitatively the kinetic rates of relevant processes. However, ZBH has not been measured directly with consistent success: a simple respirometric batch test has provided varying correspondence between measured and theoretical concentrations. In this paper, the batch test is applied to mixed liquors drawn from well defined anoxic/aerobic parent systems at 10 and 20 d sludge ages, with consistent but poor correspondence between measured and theoretical values. In contrast, aerobic digestion batch tests on the same mixed liquors give good correspondences. It is concluded that the differences between theoretical and batch test measured values are due to the batch test method itself and its interpretation. It is found that the batch test conditions (particularly the substrate/ZBH ratio) influence the kinetic constants derived from the data, and hence the ZBH estimate. Two kinetic models with two competing OHO populations, a fast and a slow grower, are developed and applied to the batch tests and parent systems. The first model is based on kinetic selection only, while the second includes additional metabolic selection. Both models can account for the observations in the batch tests, but the second provides greater consistency between simulations of the parent systems and batch tests.
An evaluation of full-scale activated sludge dynamics using microbial fatty acid analysis
Authors: Werker A.G.
Published: July 2006

Patterns of microbial fatty acids (MFAs) from activated sludge samples were analyzed over one year's operation at the Hamilton Woodward municipal wastewater treatment plant in Canada. The objective was to examine community structure dynamics and to consider the potential for interrelationships between the population dynamics and treatment performance. With the exception of a higher than normal solids discharge on one day, the treatment plant operations were otherwise stable during the year. As such, wastewater temperature appeared to be the dominant influence on the observed dynamics of the MFA community structure. MFA monitoring and analysis was demonstrated as a practical diagnostic tool in community structure trend monitoring. While the findings did suggest potential for full-scale treatment process monitoring, further development is required. Advancement in technique and greater insight for the data interpretation will be made with historical data from continued case studies. In future studies, selective sub-sampling of biomass fractions (settling and dispersed fauna), evolution in the compositional analysis methods, and, ideally, complementary genotypic and classical microscopic analyses on select samples are recommended.
Ecophysiology and niche differentiation of Nitrospira-like bacteria, the key nitrite oxidizers in wastewater treatment plants
Authors: Daims H. , Maixner F. , Lücker S. , Stoecker K. , Hace K. , Wagner M.
Published: July 2006

Nitrite-oxidizing bacteria of the genus Nitrospira are key nitrifiers in wastewater treatment plants. Pure cultures of these organisms are unavailable, but cultivation-independent molecular methods make it possible to detect Nitrospira-like bacteria in environmental samples and to investigate their ecophysiology. Comprehensive screening of natural and engineered habitats and of public databases for 16S rRNA sequences of Nitrospira-like bacteria revealed a surprisingly high biodiversity in the genus Nitrospira, which comprises at least four phylogenetic sublineages. All Nitrospira-like bacteria detected in wastewater treatment plants belonged to the sublineages I and II. Subsequently, the population dynamics of different Nitrospira-like bacteria were monitored, by quantitative fluorescence in situ hybridization with rRNA-targeted probes, confocal laser scanning microscopy and digital image analysis, during incubation of nitrifying activated sludge in media containing different nitrite concentrations. These experiments showed that Nitrospira-like bacteria, which were affiliated with the phylogenetic sublineages I or II of the genus Nitrospira, responded differently to nitrite concentration shifts. Previously unknown properties of Nitrospira-like bacteria were discovered in the course of an environmental genomics project. Implications of the obtained results for fundamental understanding of the microbial ecology of nitrite oxidizers as well as for future improvement of nutrient removal in wastewater treatment plants are discussed.
Gene cassette-associated sequences from phosphorus and non-phosphorus removing microbial communities in aerobic:anaerobic sequencing batch reactors
Authors: Beer M. , Seviour R.J.
Published: July 2006

Mobile gene elements associated with integrons, including as gene cassettes, have been proposed to play an important role in bacterial evolution by providing an extensive genetic resource. This study hypothesized that critical genes for enzymes involved in EBPR systems, including those involved in polyphosphate, PHA and glycogen synthesis, may be present in mobile gene cassettes. Although no such genes were identified in any of the functional and deteriorated enhanced biological phosphorus removal (EBPR) laboratory-scale SBR systems examined here, many of the open reading frames (ORFs) remained unidentified because of the incompleteness of publicly available databases. An ORF of unknown function (SBR6-2) was encountered in deteriorated EBPR system with an unexpectedly high frequency, comprising 35% of the gene cassette-associated sequences for that system.
Proliferation of glycogen accumulating organisms induced by Fe(III) dosing in a domestic wastewater treatment plant
Authors: Jobbágy A. , Literáthy B. , Wong M.-T. , Tardy G. , Liu W.-T.
Published: July 2006

To meet the effluent requirements given for the sensitive receiving body, the Southpest Wastewater Treatment Plant of Budapest, Hungary uses a combined activated sludge-biofilter system with chemical precipitation for P removal. Causes of the proliferation of glycogen accumulating organisms (GAOs) observed in the unaerated/oxic activated sludge unit of this system were investigated both in full-scale and in lab-scale experiments combined with a detailed analysis of the microbial communities. Concentration profile measurements throughout the 8-stage activated sludge unit indicated anaerobic conditions in the first two unaerated reactors and low orthophosphate level (<1 mg l−1) in all of the stages that could not be attributed to the influent quality, but to Fe (III)-dosing to the returned activated sludge. Microbiological analysis revealed the presence of GAOs from the GB group in the Gammaproteobacteria and occasionally tetrad-forming organisms from Actinobacteria, and the absence of Rhodocyclus-related polyphosphate accumulating organisms (PAOs) in the activated sludge samples. Comparative lab-scale studies carried out in two identically arranged UCT-systems with staged anoxic reactors also confirmed that Fe (III)-dosing may result in phosphorus deficiency of the microbial niche, leading to the suppression of growth and EBPR activity of PAOs and to the proliferation of GAOs.
Microbial community development in a laboratory-scale nitrifying activated sludge system with input from a side-stream bioreactor treating digester supernatant
Authors: Smith R.C. , Oerther D.B
Published: July 2006

Three laboratory-scale activated sludge treatment trains were operated to investigate the effect on biodiversity in plug flow (PFR) main-stream sewage treatment from input of biomass from side-stream reactors treating anaerobic digester supernatant. One train had a completely mixed (CSTR) side-stream reactor, one a PFR side-stream reactor, and the third train was a control that did not receive input from a side-stream reactor. Restriction endonucleases were used to digest polymerase chain reaction-amplified ammonia monooxygenase subunit A (amoA) genes in monthly samples from each reactor. Restriction fragment banding patterns from polyacrylimide gel electrophoresis indicated that the structure of the ammonia oxidizing bacteria (AOB) populations in all five reactors stabilized by the fourth month of operation and then did not vary subsequently. Furthermore, a dendrogram generated using the Jaccard distance showed that the AOB in each side-stream reactor was most similar to the main-stream reactor in the same train indicating that the AOB population in the side-stream reactor exerts a strong influence on the population in the main-stream reactor. Sequencing results indicated that Nitrosomonas europea, an r-strategist, was the dominant AOB in the PFR side-stream reactor, while Nitrosomonas europea and Nitrosomonas marina, a marine bacterium, were strongly represented in the CSTR side-stream reactor.
Effect of phosphorus limitation on microbial floc structure and gene expression in activated sludge
Authors: Liu J.R. , Liu C.T. , Edwards E.A. , Liss S.N.
Published: July 2006

The effect of limiting phosphorus (P) in activated sludge was investigated in laboratory-scale sequencing batch reactors (SBRs). Correlative microscopy revealed that P-limitation (COD:N:P=100:5:0.05) leads to morphological changes in floc structure and the composition of extracellular polymeric substances (EPS). This was found to be accompanied by expression of quorum-sensing in an acyl homoserine lactone bioassay. Differential gene expression in relation to P-limitation was examined in a global profile using the Affymetrix™ Escherichia coli antisense genomic microarray. Three separate experiments were conducted where the impact of P-limitation was examined under batch conditions and in SBRs at stable operating conditions and within 3–7 days following a down-shift in P. Significant changes in open reading frames (ORF) and intergenic regions based on the E. coli microarray were observed. Several genes associated with cell structure, including slt, wbbH, fimH, amB, rfaJ and slp were found to be expressed. Quorum regulated genes were also found to be expressed including psiF which is known to be induced by P-starvation (92% confidence level; 1.45 log ratio).