Environment Quality

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reaction...

Switchgrass ( L.) has been promoted as a potential feedstock for cellulosic biofuel in the United States. Switchgrass is known to respond to N fertilizer, but optimal rates remain unclear. Given the potential nonlinear response of nitrous oxide (NO) emissions to N inputs, N additions to switchgrass above optimal levels could have large impacts on the greenhouse gas balance of switchgrass-based biofuel. Additionally, N additions are likely to have large impacts on switchgrass production costs. Yield, N removal, and net returns were measured in switchgrass receiving 0 to 200 kg N ha in Manhattan, KS, from 2012 to 2014. Emissions of NO were measured in the 0- to 150-kg N ha treatments. Total emissions of NO increased from 0.2 to 3.0 kg NO-N ha as N inputs increased from 0 to 150 kg N ha. The 3-yr averages of fertilizer-induced emission factors were 0.7, 2.1, and 2.6% at 50, 100, and 150 kg N ha, respectively. Removal of N at harvest increased linearly with increasing N rate. Switchgras...

Livestock manure can be a significant source of greenhouse gases (GHG) including methane (CH 4) and nitrous oxide (N 2 O). However, GHG emissions are strongly affected by the type of waste management system (WMS) used. For example, CH 4 emissions increase substantially under anaerobic conditions that occur in many WMSs. There is a need for improved estimates at regional and national scales of the effect of WMSs on GHG emissions and identification of opportunities and associated costs to mitigate these emissions. As New York State is the fourth largest dairy producer in the country, our objectives were to quantify (i) the changes in WMS and associated GHG emissions over time, (ii) a methane conversion factor (MCF) derived from existing data from three covered manure storage units in New York, and (iii) the benefit and cost of installing covers and flares to destroy CH 4 from existing storage units. We found that GHG emissions from changing manure management increased from 0.7 Tg carbon dioxide equivalents per year (CO 2 e yr −1) in 1992 to 1.6 Tg CO 2 e yr −1 in 2012. We derived an MCF of 0.61 based on data from dairy manure storage units with covers that captured and flared CH 4 in 2010 and used this MCF to project GHG reductions for a statewide mitigation scenario in year 2022. This scenario, covering and flaring CH 4 from 662 manure storage units, mitigates 1.8 Tg CO 2 e annually or 62% of manure GHG (CH 4 and N 2 O) at an estimated

Another example is the Surface Mining Control and containing a land area of 166 km 2 (63 mi 2), has a long history of in-Reclamation Act (SMCRA), which became law in 1977. dustrial development and attendant environmental abuses from both The SMCRA established mining performance and land land and water pollution practices. The water in Deckers Creek was sampled in 1974 at 29 locations along the main stem and resampled reclamation standards, including the assurance that "surin 1999-2000 to determine water quality changes over this 25-year peface coal mining operations are so conducted as to proriod. Water samples were analyzed for pH, acidity, alkalinity, iron, tect the environment." It also provided a mechanism and calcium at both times, while aluminum, manganese, zinc, and fewhere previously disturbed and abandoned, unreclaimed cal coliform (FC) bacteria densities were added in 1999-2000. Water land could be reclaimed to current standards. at almost all sampling points showed lower acidity and metal contents The effects of these two laws on water quality improvein 1999-2000 compared with 1974. Water pH increased at the mouth ments are often overlooked because changes in land from 5.4 in 1974 to 6.0 in 1999-2000. Acidity and iron concentrations and water resources over decades of time are forgotten were decreased an average of 70% in the upper stretches of the creek. or not passed on to succeeding generations. The Deckers However, one major untreated point source of water from an aban-Creek watershed has a long history of industrial develdoned underground mining complex continues to degrade the quality opment and associated environmental abuses from both of the creek in its lower stretches. In the upper section, the water quality in Deckers Creek has improved due to decreased surface and land and water pollution practices. This watershed is underground coal mining activities, reclamation of abandoned and re-used as an example to evaluate the changes of water cently permitted surface mined lands, and natural healing of past quality in the Appalachian region where resource extracland use scars from timbering and mining over time. The decrease in tion practices have occurred during the past 100 years. mineral extraction activities and the reclamation of disturbed lands has occurred due to the passage and enforcement of water quality DESCRIPTION, HISTORY, AND and land reclamation laws and regulations. More time and additional POLLUTION OF DECKERS CREEK reclamation projects will continue to enhance the water quality in the creek. Improved water chemistry in the majority of the creek, how-Division of Plant and Soil Sciences, West Virginia Univ., Morgantown, active, mesic Fluventic Dystrudept) series in the bot

mine operations in the early 1970s. For example, the West Virginia legislature passed a law in 1971 requiring Acid-base accounting (ABA) is an analytical procedure that promine operators to show in the permit "the presence of vides values to help assess the acid-producing and acid-neutralizing any acid-producing materials, which, when present, may potential of overburden rocks prior to coal mining and other largecause minesoils with a pH of less than 3.5 and prevent scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requir-effective revegetation" (West Virginia Department of ing an assessment of surface mining on water quality, ABA became a Mines and Minerals, 1971). Dr. Richard M. Smith and preferred method to predict post-mining water quality, and permitting his associates at West Virginia University, in conjuncdecisions for surface mines are largely based on the values determined tion with the existing West Virginia coal regulatory by ABA. To predict the post-mining water quality, the amount of agency, began working on a procedure to identify acidacid-producing rock is compared with the amount of acid-neutralizing producing materials in 1965 (Perry, 1998). Throughout rock, and a prediction of the water quality at the site (whether acid the late 1960s and 1970s, the procedure was refined or alkaline) is obtained. We gathered geologic and geographic data and termed acid-base accounting (ABA) (Smith et al., for 56 mined sites in West Virginia, which allowed us to estimate 1976). Acid-base accounting was originally designed to total overburden amounts, and values were determined for maximum distinguish layers in the overburden that could be used potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP to MPA ratios for each site based on as topsoil substitutes or as hard durable rock for valley ABA. These values were correlated to post-mining water quality fills. Since the method identified both acid-producing from springs or seeps on the mined property. Overburden mass was and acid-neutralizing materials in the overburden, this determined by three methods, with the method used by Pennsylvania method was one of the earliest technologies available researchers showing the most accurate results for overburden mass. to predict the quantity of acid-producing materials prior A poor relationship existed between MPA and post-mining water to mining (Grube et al., 1973; Skousen et al., 1990; West quality, NP was intermediate, and NNP and the NP to MPA ratio Virginia University, 1971). Since the late 1970s and the showed the best prediction accuracy. In this study, NNP and the passage of the Surface Mining Control and Reclamation NP to MPA ratio gave identical water quality prediction results.

Increasing amounts of animal and municipal wastes are being composted before land application to improve handling and spreading characteristics, and to reduce odor and disease incidence. Repeated applications of composted biosolids and manure to cropland may increase the risk for P enrichment of agricultural runoff. We conducted field research in 2003 and 2004 on a Fauquier silty clay loam (Ultic Hapludalfs) to compare the effects of annual (since 1999) applications of composted and uncomposted organic residuals on P runoff characteristics. Biosolids compost (BSC), poultry litter-yard waste compost (PLC), and uncomposted poultry litter (PL) were applied based on estimated plant-available N. A commercial fertilizer treatment (CF) and an unamended control treatment (CTL) were also included. Corn (Zea mays L.) and a cereal rye (Secale cereal L.) cover crop were planted each year. We applied simulated rainfall in fall 2004 and analyzed runoff for dissolved reactive P (DRP), total dissolved P (TDP), total P (TP), total organic C (TOC), and total suspended solids (TSS). End of season soil samples were analyzed for Mehlich-3 P (M3P), EPA 3050 P (3050P), water soluble P (WSP), degree of P saturation (DPS), soil C, and bulk density. Compost treatments significantly increased soil C, decreased bulk density, and increased M3P, 3050P, WSP, and DPS. The concentration of DRP, TDP, and TP in runoff was highest in compost treatments, but the mass of DRP and TDP was not different among treatments because infiltration was higher and runoff lower in compostamended soil. Improved soil physical properties associated with poultry litter-yard waste compost application decreased loss of TP and TSS.

In arid-zone agriculture where available irrigation water is saline, desalination is becoming an attractive method for increasing yields and reducing negative environmental consequences. However, irrigation with desalinated water can be problematic if essential nutrients, including Ca, Mg, and S, removed during reverse osmosis, are not reintroduced. We evaluated two strategies for supplying these nutrients — direct fertilization and blending of

Land application of manure may contribute endocrine disrupting compounds (EDCs) such as steroid hormones to the environment. Little attention has been paid to the potential for degradation of steroid hormones by manure-borne bacteria and their degradation kinetics and pathways. In a laboratory study, the potential for biodegradation of testosterone, 17b-estradiol (E2) and progesterone by swine (Sus scrofa) manure-borne bacteria was examined. In addition, the impact of temperature, pH (6, 7, and 7.5), glucose amendments (0, 3, and 22 mmol L -1 ), and presence of oxygen on testosterone degradation kinetics was determined. Testosterone, 17b-estradiol and progesterone were biodegraded within 25 h of reaction initiation under aerobic conditions. The degradation of testosterone followed pseudo first-order and zero-order reaction kinetics under aerobic and anaerobic conditions, respectively, in tryptic soy broth (TSB) pre-enriched systems. The half-life (t 1/2 ) for the degradation of testosterone under anaerobic conditions was six times longer than aerobic conditions. Testosterone degradation was found to significantly increase (~ 17%) when incubated at 37°C vs. 22°C. The impact of pH (t 1/2 ranged from 4.4-4.9 h) and glucose amendments (t 1/2 ranged from 4.6-5.1 h) on the testosterone degradation rate were found to be small. Testosterone was transformed to dehydrotestosterone (DHT) (major degradation product), androstenedione (AD), and androstadienedione (ADD) under aerobic conditions as revealed by liquid chromatography-time-of-flight mass spectrometry (LC/TOF-MS). These results indicate that testosterone is rapidly degraded by manure-borne bacteria under a wide range of environmentally relevant conditions. However, the formed degradation products are still of potential concern due to their endocrine disrupting potential.

Supplemental Fig. S1 XAFS spectra of the Pb standards used in the experiment Supplemental Fig S2. Pb XAFS spectra of Kansas City site soils and PBET residues (solid lines) and their linear combination fits (LCF: dotted lines); compost-added soils: KC-C1-16d, KC-C2-16d, KC-C3-16d, KC-C1-121d, KC-C2-69d, and KC-C3-105d; control soils: KC-4-16d, KC-5-16d, KC-4-121d, and KC-5-69d. The number followed by "d" in the sample names denotes the days after compost addition. A) Soil at the beginning of the growing season; ‡Composite soil sample of compost-added soils prior to compost addition. B) Soil at harvest. C) PBET residues. R: normalized sum of the squared residuals of the linear combination fit. Supplemental Fig. S3. Pb XAFS spectra of Philadelphia site soils and PBET residues (solid lines) and their linear combination fits (LCF: dotted lines). A) Soil; P-C-115d: Compost-added soil collected 115days after compost addition; P

centrations in surface water increased, seemingly as a direct consequence of drainage and oxidation of Zn Due to geochemical processes, peat soils often have elevated consulfides (Cannon, 1955). The maximum Zn concentracentrations of trace elements, which are gradually released following tion in drainage water was 11 mg L Ϫ1 , with concentradrainage for agriculture. Our objectives were to use incubation temtions in aboveground plants as high as 10 g kg Ϫ1 . The peratures to vary microbial activity in two metalliferous peats (M7 acidic peat and M3 neutral peat) from the Elba, New York region, high concentration of Zn in drainage water is a threat and to use periodic leaching to assess the extent of trace element to surface and ground water quality, and has raised release from these soils. Dried soils were mixed with glass beads to concern about other toxic trace elements (e.g., Cd) that maintain aeration, moistened, and incubated at 4, 16, 28, and 37؇C in may be present in the peat and released in soluble forms.

The importance of animal production in the overall context of human activity is undisputed and influences food supply, job security, income producing, as well as landscape and local ecosystems conservation. This relevance enhances the charges by society as the environmental impacts of various activities, especially in relation to ruminant production amid the current problems of climate changes. In this context, we analyzed the main environmental impacts of two typical beef cattle production systems from southern Brazil, namely the extensive system (ES) and the improved system (IS), and identified the components that have the greatest environmental impacts using the life cycle assessment method. The basis of the system construction was a cattle herd that originated from 100 weaned heifers, four weaned calves, and the progeny of these cattle during their productive life (12 years), and the land areas, external inputs, and other natural resources and technologies necessary to the operations. The functional unit was the production of 1 kg of live weight. The values of greenhouse gas emissions, land use, and freshwater depletion in the ES were higher compared with those values obtained for the IS (22.52 and 9.16 kg CO 2 equivalents; 234.78 and 21.03 m 2 a; and 0.217 and 0.0949 m 3 , respectively). These variations were attributed to the permanence time of the animals in each system and to the quality and production of the pastures. The ES presented lower potential impacts than the IS on metal depletion and soil acidification (0.000519 and 0.0536 kg Fe equivalents; and 0.0028 and 0.0038 kg SO 2 equivalents, respectively) mainly due to the pasture improvement practices and the salt supply to the animals. Moreover, the values of freshwater eutrophication and fossil depletion were higher in the ES than in the IS (0.00383 and 0.00219 kg P equivalents and 0.0042 and À0.1255 kg oil equivalents, respectively). While the pasture nutrient loss from runoff and leaching defined the values of eutrophication, the introduction of legumes compensates the use of fossil fuels. The diversity of the results provides a better understanding of the environmental impacts of different production systems and of regional singularities.

Dissolved organic carbon (DOC) export from soils can play a significant role in soil C cycling and in nutrient and pollutant transport. However, information about DOC losses from agricultural soils as influenced by management practices is scarce. We compared the effects of mineral fertilizer (MF) and liquid hog manure (LHM) applications on the concentration and molecular size of DOC released in runoff and tile-drain water under corn (Zea mays L.) and forage cropping systems. Runoff and tile-drain water samples were collected during a 2-mo period (October to December 1998) and DOC concentration was measured. Characterization of DOC was performed by tangential ultrafiltration with nominal cut-offs at 3 and 100 kDa. Mean concentration of DOC in runoff water (12.7 mg DOC L 21 ) was higher than in tile-drain water (6.5 mg DOC L 21 ). Incorporation of corn residues increased the DOC concentration by 6-to 17-fold in surface runoff, but this effect was short-lived. In runoff water, the relative size of the DOC molecules increased when corn residues and LHM were applied probably due to partial microbial breakdown of these organic materials and to a faster decomposition or preferential adsorption of the small molecules. The DOC concentration in tile-drain water was slightly higher under forage (7.5 mg DOC L 21 ) than under corn (5.4 mg DOC L 21 ) even though the application rates of LHM were higher in corn plots. We suggest that preferential flow facilitated the migration of DOC to tile drains in forage plots. In conclusion, incorporation of corn residues and LHM increased the concentration of DOC and the relative size of the molecules in surface runoff water, whereas DOC in tile-drain water was mostly influenced by the cropping system with relatively more DOC and larger molecules under forage than corn.

few. There obviously exists a distinct need for a major paradigm shift from a conveyance mentality to a dispersed, "start-at-the-Crop Production in Saline Environments: Global and Intesource" form of micromanagement based on infiltration. This grative Perspectives-Sham S. Goyal, Surinder K. Sharma, novel approach, taken across the spatial scale from suburban and D. William Rains. The Haworth Press, 10 Alice Street, parking lots to riparian zones, wetlands, and watersheds, is devel-Binghamton, NY 13904-1580. 2003 oped and explored in the handbook by renowned practitioners 1-56022-097-X.

Roof-harvested rainwater (RHRW) has been considered an effective alternative water source for drinking and various nonpotable uses in a number of countries throughout the world. The most significant issue in relation to using untreated RHRW for drinking or other potable uses, however, is the potential public health risks associated with microbial pathogens. This paper reviews the available research reporting on the microbial quality of RHRW and provides insight on the capacity of fecal indicator bacteria to monitor health risks and disease outbreaks associated with the consumption of untreated RHRW. Several zoonotic bacterial and protozoan pathogens were detected in individual and communal rainwater systems. The majority of the studies reported in the literature assessed the quality of rainwater on the basis of the presence or absence of specific pathogens, with little information available regarding the actual numbers of such pathogens. In addition, no information is available concerning the ongoing prevalence of different pathogens in RHRW over time. The published data suggest that the microbial quality of RHRW should be considered less than that expected for potable water and that the commonly used indicators may not be suitable to indicate the presence of pathogens in RHRW. Several case control studies established potential links between gastroenteritis and consumption of untreated RHRW. Therefore, health risks assessment models, such as those using Quantitative Microbial Risk Assessment, should be used to manage and mitigate health risks associated with drinking and nonpotable uses of RHRW.

The Energy Technology Options Conference opened with a presentation from Professor Thomas Johansson on the prospects for renewable energy in a global context. It was based upon a study commissioned by the United Nations Solar Energy Group for Environment and Development, which he chairs. This study has since been published in a large book entitled Renewable Energy: Sources for Fuels and Electricity; it contains reports by specialists on a long list of renewable technologies (see

A simple, precise, and rapid method for estimating total N (to include nitrate and nitrite) in natural water is given. The proposed method involves evaporation of the water sample, pretreatment of the evaporated sample with reduced iron and H₂SO₄ to reduce nitrate to ammonium, and subsequent Kjeldahl digestion of the sample to recover organic N. Evaporation, pretreatment, and digestion of samples are accomplished in Folin-Wu nonprotein tubes. Ammonium in the digest is estimated by steam distillation and subsequent titration. Evaluation of the proposed method revealed that the recovery of nitrate N and organic N in samples was affected by the amount of reduced iron added (200 mg was satisfactory), by the brand of reduced iron used (several preparations were satisfactory), and by gently boiling the sample with reduced iron and H₂SO₄ prior to digestion. The proposed method was effective in recovering nitrate N and organic N from water solution over a wide range in concentration and the method was successful in recovering nitrate N and organic N added to filtered and unfiltered river and pond water samples. The precision of the proposed method was satisfactory for total N analysis of water samples, and the method appears adequate for estimation of total N in most water and waste water samples.

This chapter provides an economic perspective of environmental law and policy with regard to both normative and positive dimensions. It begins with an examination of the central problem in environmental regulation: the tendency of pollution generators in an unconstrained market economy to externalize some of the costs of their production, leading to an inefficiently large amount of pollution. We examine the ends of environmental policy, that is, the setting of goals and targets, beginning with normative issues, notably the Kaldor-Hicks criterion and the related method of assessment known as benefit-cost analysis. We examine this analytical method in detail, including its theoretical foundations and empirical methods of estimation of compliance costs and environmental benefits. We include a review of critiques of benefit-cost analysis, briefly examine alternative approaches to analyzing the goals of environmental policies, and survey the efforts of the Federal governmental to employ these analytical methods.

A modeling framework consisting of a farm-scale model, Agricultural Policy Environmental Extender (APEX); a watershed-scale model, Soil and Water Assessment Tool (SWAT); and databases was used in the Conservation Effects Assessment Project to quantify the environmental benefits of conservation practices on cropland. APEX is used to simulate conservation practices on cultivated cropland and Conservation Reserve Program land to assess the edge-of-field water-quality benefits. Flow and pollutant loadings from APEX are input to SWAT. SWAT simulates the remaining noncultivated land and routes flow and loads generated from noncultivated land, point sources, and cropland to the basin outlet. SWAT is used for assessing the effects of practices on local and in-stream water-quality benefits. Each river basin is calibrated and validated for streamflow and loads at multiple gauging stations. The objectives of the current study are to estimate the effects of currently existing and additional con...

This volume of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive, state-of-the-art and worldwide overview of scientific knowledge related to the mitigation of climate change. It includes a detailed assessment ...

This chapter provides an economic perspective of environmental law and policy with regard to both normative and positive dimensions. It begins with an examination of the central problem in environmental regulation: the tendency of pollution generators in an unconstrained market economy to externalize some of the costs of their production, leading to an inefficiently large amount of pollution. We examine the ends of environmental policy, that is, the setting of goals and targets, beginning with normative issues, notably the Kaldor-Hicks criterion and the related method of assessment known as benefit-cost analysis. We examine this analytical method in detail, including its theoretical foundations and empirical methods of estimation of compliance costs and environmental benefits. We include a review of critiques of benefit-cost analysis, briefly examine alternative approaches to analyzing the goals of environmental policies, and survey the efforts of the Federal governmental to employ these analytical methods.

Land degradation caused by deforestation, overgrazing, and inappropriate irrigation practices aff ects about 16% of Latin America and the Caribbean (LAC). Th is paper addresses issues related to the application of remote sensing technologies for the identifi cation and mapping of land degradation features, with special attention to the LAC region. Th e contribution of remote sensing to mapping land degradation is analyzed from the compilation of a large set of research papers published between the 1980s and 2009, dealing with water and wind erosion, salinization, and changes of vegetation cover. Th e analysis undertaken found that Landsat series (MSS, TM, ETM+) are the most commonly used data source (49% of the papers report their use), followed by aerial photographs (39%), and microwave sensing (ERS, JERS-1, Radarsat) (27%). About 43% of the works analyzed use multi-scale, multi-sensor, multi-spectral approaches for mapping degraded areas, with a combination of visual interpretation and advanced image processing techniques. Th e use of more expensive hyperspectral and/or very high spatial resolution sensors like AVIRIS, Hyperion, SPOT-5, and IKONOS tends to be limited to small surface areas. Th e key issue of indicators that can directly or indirectly help recognize land degradation features in the visible, infrared, and microwave regions of the electromagnetic spectrum are discussed. Factors considered when selecting indicators for establishing land degradation baselines include, among others, the mapping scale, the spectral characteristics of the sensors, and the time of image acquisition. Th e validation methods used to assess the accuracy of maps produced with satellite data are discussed as well.

Assessments of the efficacy of mitigation of greenhouse gas (GHG) emissions from paddy rice systems have typically been analyzed based on field studies. Extrapolation of the mitigation potential of alternative management practices from field studies to a national scale may be enhanced by spatially explicit process models, like the DeNitrification and DeComposition (DNDC) model. Our objective was to analyze the impacts of mitigation alternatives, management of water, fertilizer, and rice straw, on net GHG emissions (carbon dioxide, methane, and nitrous oxide fluxes), yields, and water use. After constructing a GIS database of soil, climate, rice cropping area and systems, and management practices, we ran DNDC with 21-yr alternative management schemes for each of the approximately 2500 counties in China. Results indicate that, despite large-scale adoption of midseason drainage, there is still large potential for additional methane reductions from Chinese rice paddies of 20 to 60% over 2000-2020. However, changes in management for reducing CH 4 emissions simultaneously affect soil carbon dynamics as well as N 2 O emissions and can thereby reorder the ranking of technical mitigation effectiveness. The order of net GHG emissions reduction effectiveness found here is upland rice . shallow flooding . ammonium sulfate . midseason drainage . off-season straw . slow-release fertilizer . continuous flooding. Most of the management alternatives produced yields comparable to the baseline; however, continuous flooding and upland rice significantly reduced yields. Water management strategies appear to be the most technically promising GHG mitigation alternatives, with shallow flooding providing additional benefits of both water conservation and increased yields.

Th e greenhouse gas (GHG) impact of composting a range of potential feedstocks was evaluated through a review of the existing literature with a focus on methane (CH 4 ) avoidance by composting and GHG emissions during composting. Th e primary carbon credits associated with composting are through CH 4 avoidance when feedstocks are composted instead of landfi lled (municipal solid waste and biosolids) or lagooned (animal manures). Methane generation potential is given based on total volatile solids, expected volatile solids destruction, and CH 4 generation from lab and fi eld incubations. For example, a facility that composts an equal mixture of manure, newsprint, and food waste could conserve the equivalent of 3.1 Mg CO 2 per 1 dry Mg of feedstocks composted if feedstocks were diverted from anaerobic storage lagoons and landfi lls with no gas collection mechanisms. Th e composting process is a source of GHG emissions from the use of electricity and fossil fuels and through GHG emissions during composting. Greenhouse gas emissions during composting are highest for highnitrogen materials with high moisture contents. Th ese debits are minimal in comparison to avoidance credits and can be further minimized through the use of higher carbon:nitrogen feedstock mixtures and lower-moisture-content mixtures. Compost end use has the potential to generate carbon credits through avoidance and sequestration of carbon; however, these are highly project specifi c and need to be quantifi ed on an individual project basis.

of a fine-grained soil having low saturated hydraulic conductivity or a "composite barrier" consisting of a Landfill covers are critical to waste containment, yet field perforgeomembrane (plastic sheet, 1-2 mm thick) underlain mance of specific cover designs has not been well documented and by fine-grained soil (USEPA, 1992). The layer of fineet al.Alternative Cover Assessment Project (ACAP) in 1998 Langan Engineering and Environmental Services, Inc., Elmwood to provide a more general understanding of the hydro-Park, NJ 07407. T. Abichou, Department of Civil and Environmental logic behavior of conventional and alternative landfill Engineering, 2525 Pottsdamer Street, Florida State University, Tallafinal covers (Albright et al., 2003). hassee, FL 32310. S.A. Rock,

The USDA initiated the Conservation Effects Assessment Project (CEAP) to quantify the environmental benefits of conservation practices at regional and national scales. For this assessment, a sampling and modeling approach is used. This paper provides a technical overview of the modeling approach used in CEAP cropland assessment to estimate the off-site water quality benefits of conservation practices using the Ohio River Basin (ORB) as an example. The modeling approach uses a farm-scale model, Agricultural Policy Environmental Extender (APEX), and a watershed scale model (the Soil and Water Assessment Tool [SWAT]) and databases in the Hydrologic Unit Modeling for the United States system. Databases of land use, soils, land use management, topography, weather, point sources, and atmospheric depositions were developed to derive model inputs. APEX simulates the cultivated cropland, Conserve Reserve Program land, and the practices implemented on them, whereas SWAT simulates the noncultivated land (e.g., pasture, range, urban, and forest) and point sources. Simulation results from APEX are input into SWAT. SWAT routes all sources, including APEX's, to the basin outlet through each eight-digit watershed. Each basin is calibrated for stream flow, sediment, and nutrient loads at multiple gaging sites and turned in for simulating the effects of conservation practice scenarios on water quality. Results indicate that sediment, nitrogen, and phosphorus loads delivered to the Mississippi River from ORB could be reduced by 16, 15, and 23%, respectively, due to current conservation practices. Modeling tools are useful to provide sciencebased information for assessing existing conservation programs, developing future programs, and developing insights on load reductions necessary for hypoxia in the Gulf of Mexico.