Showing papers on "Air quality index published in 2001"
TL;DR: In this article, an analysis of temperature trends for the last 100 years in several large U.S. cities indicate that, since ∼1940, temperatures in urban areas have increased by about 0.5-3.0°C.
1,526 citations
TL;DR: The Secondary Organic Aerosol Model (SORGAM) as mentioned in this paper has been developed for use in comprehensive air quality model systems and is capable of simulating secondary organic aerosol (SOA) formation including the production of lowvolatility products and their subsequent gas/particle partitioning.
Abstract: The Secondary Organic Aerosol Model (SORGAM) has been developed for use in comprehensive air quality model systems. Coupled to a chemistry-transport model, SORGAM is capable of simulating secondary organic aerosol (SOA) formation including the production of low-volatility products and their subsequent gas/particle partitioning. The current model formulation assumes that all SOA compounds interact and form a quasi-ideal solution. This has significant impact on the gas/particle partitioning, since in this case the saturation concentrations of the SOA compounds depend on the composition of the SOA and the amount of absorbing material present. Box model simulations have been performed to investigate the sensitivity of the model against several parameters. Results clearly show the importance of the temperature dependence of saturation concentrations on the partitioning process. Furthermore, SORGAM has been coupled to the comprehensive European Air Pollution and Dispersion/Modal Aerosol Dynamics Model for Europe air quality model system, and results of a three-dimensional model application are presented. The model results indicate that assuming interacting SOA compounds, biogenic and anthropogenic contributions significantly influence each other and cannot be treated independently.
811 citations
Max Planck Society1, Scripps Institution of Oceanography2, National Center for Atmospheric Research3, Georgia Institute of Technology4, University of Maryland, College Park5, Utrecht University6, University of Innsbruck7, National Oceanic and Atmospheric Administration8, Physical Research Laboratory9, National Physical Laboratory10, Lawrence Berkeley National Laboratory11, University of California, Riverside12, Stockholm University13
TL;DR: It is shown that agricultural burning and especially biofuel use enhance carbon monoxide concentrations and Fossil fuel combustion and biomass burning cause a high aerosol loading, which gives rise to extensive air quality degradation.
Abstract: The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6°S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.
725 citations
TL;DR: In this paper, the authors consider the variety of transport impacts on the atmospheric environment by reviewing three examples: urban road traffic and human health, aircraft emissions and global atmospheric change, and the contribution of sulphur emissions from ships to acid deposition.
660 citations
TL;DR: In this paper, a review describes databases of small-scale spatial variations and indoor, outdoor and personal measurements of air pollutants with the main focus on suspended particulate matter, and to a lesser extent, nitrogen dioxide and photochemical pollutants.
504 citations
TL;DR: In this paper, the authors examined the effect of air quality regulation on productivity in some of the most heavily regulated manufacturing plants in the United States, the oil refineries of the Los Angeles (South Coast) Air Basin.
Abstract: We examine the effect of air quality regulation on productivity in some of the most heavily regulated manufacturing plants in the United States, the oil refineries of the Los Angeles (South Coast) Air Basin. We use direct measures of local air pollution regulation to estimate their effects on abatement investment. Refineries not subject to these regulations are used as a comparison group. We study a period of sharply increased regulation between 1979 and 1992. Initial compliance with each regulation cost $3 million per plant and a further $5 million to comply with increased stringency. We construct measures of total factor productivity using Census of Manufacturers output and materials data that report physical quantities of inputs and outputs for the entire population of refineries. Despite high costs associated with the local regulations, productivity in the Los Angeles Air Basin refineries rose sharply between 1987 and 1992, which was a period of decreased refinery productivity in other regions. We con...
495 citations
TL;DR: In poorly ventilated buildings-indoor emission source strength is considered a more significant influence on VOC concentrations than infiltration of outdoor air, and in six smoking homes studied, environmental tobacco smoke was found to make a substantial contribution to concentrations of 1,3-butadiene.
Abstract: Concentrations of 15 VOCs including 1,3-butadiene, benzene, and styrene were measured in a wide range of urban microenvironments, viz: homes, offices, restaurants, pubs, department stores, coach and train stations, cinemas, libraries, laboratories, perfume shops, heavily trafficked roadside locations, buses, trains, and automobiles. For most target VOCs-including 1,3-butadiene and benzene-mean concentrations at heavily trafficked roadside locations were exceeded by those in automobiles and were comparable to those in pubs and train stations. With regard to indoor-outdoor relationships in homes, this study revealed higher mean indoor concentrations, no correlation between simultaneously measured indoor and outdoor concentrations, and significantly different patterns of diurnal variation. Thus-in poorly ventilated buildings-indoor emission source strength is considered a more significant influence on VOC concentrations than infiltration of outdoor air. In the six smoking homes studied, environmental tobacco smoke (ETS) was found to make a substantial contribution to concentrations of 1,3-butadiene. This finding was based on the significantly higher concentrations detected in smoking compared to nonsmoking homes, the significant correlation between 1,3-butadiene concentrations and those of 3-ethenylpyridine (an ETS marker), factor analysis, and the results of a source apportionment exercise based on ratios of 1,3-butadiene to 3-ethenylpyridine.
377 citations
TL;DR: In this paper, climate change may affect exposures to air pollutants by affecting weather, anthropogenic emissions, and biogenic emissions and by changing the distribution and types of airborne allergens, but the specific types of change (i.e., local, regional, or global), the direction of change in a particular location, and the magnitude of change that may be attributable to climate change are a matter of speculation, based on extrapolating present understanding to future scenarios.
Abstract: Climate change may affect exposures to air pollutants by affecting weather, anthropogenic emissions, and biogenic emissions and by changing the distribution and types of airborne allergens. Local temperature, precipitation, clouds, atmospheric water vapor, wind speed, and wind direction influence atmospheric chemical processes, and interactions occur between local and global-scale environments. If the climate becomes warmer and more variable, air quality is likely to be affected. However, the specific types of change (i.e., local, regional, or global), the direction of change in a particular location (i.e., positive or negative), and the magnitude of change in air quality that may be attributable to climate change are a matter of speculation, based on extrapolating present understanding to future scenarios. There is already extensive evidence on the health effects of air pollution. Ground-level ozone can exacerbate chronic respiratory diseases and cause short-term reductions in lung function. Exposure to particulate matter can aggravate chronic respiratory and cardiovascular diseases, alter host defenses, damage lung tissue, lead to premature death, and possibly contribute to cancer. Health effects of exposures to carbon monoxide, sulfur dioxide, and nitrogen dioxide can include reduced work capacity, aggravation of existing cardiovascular diseases, effects on pulmonary function, respiratory illnesses, lung irritation, and alterations in the lung's defense systems. Adaptations to climate change should include ensuring responsiveness of air quality protection programs to changing pollution levels. Research needs include basic atmospheric science work on the association between weather and air pollutants; improving air pollution models and their linkage with climate change scenarios; and closing gaps in the understanding of exposure patterns and health effects.
289 citations
TL;DR: In this article, a methodology based on PM2.5 measurement alone is not adequate for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major ambient air particles derived from these emissions are mainly in the range of 2.5-10μm.
229 citations
Book•
18 Oct 2001TL;DR: A detailed overview of the history of the air pollution problem in the US can be found in this article, where the authors describe the development of the Clean Air Act and its application in the field of air quality monitoring.
Abstract: A HISTORICAL OVERVIEW OF THE DEVELOPMENT OF CLEAN AIR REGULATIONS A Brief History of the Air Pollution Problem Federal Involvement in Air Pollution Control Characterizing the Atmosphere Recipe for an Air Pollution Problem References CLEAN AIR ACT History of the Clean Air Act 1990 Clean Air Act Amendments References AIR PERMITS FOR NEW SOURCE Elements of a Permit Application Best Available Control Technology Air Quality Analysis NSR Reform References ATMOSPHERIC DIFFUSION MODELING FOR PSD PERMIT REGULATIONS Introduction - Meteorological Background The Tall Stack Classifying Sources by Method of Emission Atmospheric-Diffusion Models EPA Computer Programs for Regulation of Industry The Source-Transport-Receptor Problem References SOURCE TESTING Introduction Code of Federal Regulations Representative Sampling Techniques References AMBIENT AIR QUALITY AND CONTINUOUS EMISSIONS MONITORING Ambient Air Quality Sampling Program Objectives of a Sampling Program Monitoring Systems Federal Reference Methods and Continuous Monitoring The "Complete" Environmental Surveillance and Control System Typical Air Sampling Train Integrated Sampling Devices for Suspended Particulate Matter Continuous Air Quality Monitors References COST ESTIMATING Time Value of Money Types of Cost Estimates Air Pollution Control Equipment Cost References PROCESS DESIGN AND THE STRATEGY OF PROCESS DESIGN Introduction to Process Design The Strategy of Process Design Mass and Energy Balances References PROFITABILITY AND ENGINEERING ECONOMICS Introduction - Profit Goal Profitability Analysis The Effect of Depreciation Capital Investment and Total Product Cost References INTRODUCTION TO CONTROL OF GASEOUS POLLUTANTS Absorption and Adsorption References ABSORPTION FOR HAP AND VOC CONTROL Introduction Aqueous Systems Nonaqueous Systems Types and Arrangements of Absorption Equipment Design Techniques for Countercurrent Absorption Columns Countercurrent Flow Packed Absorption Tower Design Sample Design Calculation References for Absorption ADSORPTION FOR HAP AND VOC CONTROL Introduction to Adsorption Operations Adsorption Phenomenon Adsorption Processes Nature of Adsorbents The Theories of Adsorption Adsorption Isotherms Polanyi Potential Theory Unstady-State Fixed-Bed Adsorbers Fixed Bed Adsorber Design Considerations Pressure Drop Through Adsorbers Adsorber Effectiveness and Regeneration Breakthrough Model Regeneration Modeling References THERMAL OXIDATION FOR VOC CONTROL Combustion Basics Flares Incineration Catalytic Oxidation References CONTROL OF VOC AND HAP BY CONDENSATION Introduction VOC Condensers Coolant and Heat Exchanger Type Mixtures of Organic Vapors Air as a Noncondensable References Appendix A: Derivation of the Area Model for a Mixture Condensing from a Gas Appendix B: Algorithm for the Area Model for a Mixture Condensing from a Gas CONTROL OF VOC AND HAP BY BIOFILTRATION Introduction Theory of Biofilter Operation Design Parameters and Conditions Biofilter Compared to Other Available Control Technology Successful Case Studies Further Considerations References MEMBRANE SEPARATION Overview Polymeric Membranes Performance Applications References NOX CONTROL NOX from Combustion Control Techniques References CONTROL OF SOX H2S Control SO2 (and HCI) Removal SO3 and Sulfuric Acid References FUNDAMENTALS OF PARTICULATE CONTROL Particle Size Distribution Aerodynamic Diameter Cunningham Clip Correction Collection Mechanisms References HOOD AND DUCTWORK DESIGN Introduction Hood Design Duct Design Effect of Entrance into a Hood Total Energy Loss Fan Power Hood-Duct Example References CYCLONE DESIGN Collection Efficiency Pressure Drop Saltation References DESIGN AND APPLICATION OF WET SCRUBBERS Introduction Collection Mechanisms and Efficiency Collection Mechanisms and Particle Size Selection and Design of Scrubbers Devices for Wet Scrubbing The Semrau Principle and Collection Efficiency A Model for Counter-Current Spray Scrubbers A Model for Venturi Scrubbers The Calvert Cut Diameter Design Technique The Cut-Power Relationship References Appendix: Calvert Performance Cut Diameter Data FILTRATION AND BAGHOUSES Introduction Design Issues Cleaning Mechanisms Fabric Properties Baghouse Size Pressure Drop Bag Life References ELECTROSTATIC PRECIPITATORS Early Development Basic Theory Practical Application of Theory Flue Gas Conditioning Using V/I Curves for Troubleshooting INDEX
204 citations
TL;DR: Aromatic carbonyls, unsaturatedAliphatic aldehydes, and aliphatic dicarbonyls represented larger fractions of the total carbonyl emissions for 7-8 HD vehicles than for LD vehicles, and formaldehyde and acetaldehyde emission factors measured in this study are generally lower than those measured in earlier work.
Abstract: Vehicle emissions are a major source of carbonyls, which play an important role in atmospheric chemistry and urban air quality. Yet, little data are available for speciated carbonyls emitted by veh...
TL;DR: In this paper, the authors exploit the devolved nature of environmental regulation generates rich regulatory variation across regions, industries and time to estimate employment effects of sharply increased air quality regulation in Los Angeles.
TL;DR: In this subtropical city, local air quality objectives should take into account that air pollution has stronger health effects during the cool rather than warm season and that oxidant pollutants are more important indicators of health effects than particulates.
Abstract: In different weather conditions, constituents and concentrations of pollutants, personal exposure, and biologic responses to air pollution may vary. In this study we assessed the effects of four air pollutants on mortality in both cool and warm seasons in Hong Kong, a subtropical city. Daily counts of mortality, due to all nonaccidental causes, and cardiovascular and respiratory diseases were modeled with daily pollutant concentrations [24-hr means for nitrogen dioxide, sulfur dioxide, and particulate matter 0.135). In this subtropical city, local air quality objectives should take into account that air pollution has stronger health effects during the cool rather than warm season and that oxidant pollutants are more important indicators of health effects than particulates.
TL;DR: In this article, it is recognized that infants generally at risk for atrophy when exposed to specific environmental airborne pollutants are more likely to develop asthma, once asthma is established, airborne pollutants were important triggers in causing exacerbations.
TL;DR: In the second half of 1997, large areas in Southeast Asia were severely affected by a smoke-haze pollution episode caused by the emissions of an estimated 45,600 km2 of vegetation that burnt on the Indonesian islands Kalimantan and Sumatra.
Abstract: In the second half of 1997, large areas in Southeast Asia were severely affected by a smoke-haze pollution episode caused by the emissions of an estimated 45,600 km2 of vegetation that burnt on the Indonesian islands Kalimantan and Sumatra. To document the impacts of these fires on air quality, data for total suspended particulate matter (TSP) and for particulate matter below or equal to 10 microns in diameter (PM10) from selected sites in Indonesia, Malaysia and Singapore are analysed in this paper. These data are supplemented by meteorological data, satellite images and a summary of related research. TSP was above 2,000 µg m–3 for several days in Indonesian locations close to the most extensive fire activity. In Malaysia and Singapore, ambient particle concentrations increased to several times their average September levels. Characteristically for emissions from vegetation burning, the additional atmospheric particle loading during the smoke-haze episode was predominantly due to an increase of the fraction below or equal to 2.5 microns in diameter (PM2.5). Due to the dominance of respirable particles (PM2.5) in the smoke-haze, air quality reporting based on TSP or PM10 may be inadequate to assess the health risk. Upgrading of PM2.5 monitoring facilities is therefore needed. Reducing the probability of similar smoke-haze events in future would require appropriate fire use and smoke management strategies.
TL;DR: In this article, a detailed aerosol source apportionment study was performed with two sampling campaigns, during wintertime and summertime in the heavily polluted metropolitan area of S* ao Paulo, Brazil.
Stockholm Environment Institute1, University of Bradford2, Murdoch University3, Natural Resources Canada4, Tokyo University of Agriculture and Technology5, National Institute for Environmental Studies6, National Chung Hsing University7, Banaras Hindu University8, University of the Punjab9, Council of Scientific and Industrial Research10, Spanish National Research Council11
TL;DR: A review of air pollution impacts on vegetation in developing countries by summarising information describing the direct impacts to vegetation caused by a number of air pollutants (sulphur dioxide (SO2), nitrogen oxides (NOx), ozone (O3) and suspended particulate matter (SPM)) was presented in this article.
Abstract: The predicted increases in emissions of primary pollutants in many rapidly industrializing countries may have severe consequences for the health and productivity of forest trees and agricultural crops. This paper presents a review of air pollution impacts on vegetation in developing countries by summarising information describing the direct impacts to vegetation caused by a number of air pollutants (sulphur dioxide (SO2), nitrogen oxides (NOx), ozone (O3) and Suspended Particulate Matter (SPM)). This information has been collected by experts from a number of rapidly industrializing countries in Asia, Latin America and Africa and includes observations of visible injury in the field and the use of transect studies and controlled experimental investigations to ascribe damage to different pollutant concentrations. The ability to synthesise this information to define exposure-response relationships and subsequent air quality guidelines similar to those established in North America and Europe is assessed. In addition, the use of regional and global models describing pollution concentrations is discussed with reference to assessing the extent of adverse impacts and identifying regions likely to be most at risk from air pollution, both for the present day and in the future. The evidence summarised in the paper clearly shows that current pollutant concentrations experienced in many developing countries, particularly Asia, can result in severe damage to vegetation and that without appropriate control measures such damage is likely to worsen in the future as pollutant emissions increase.
TL;DR: In this article, a model that treats nesting of gas, size-and composition-resolved aerosol, radiative, and meteorological parameters from the global through urban scales was developed.
Abstract: A model that treats nesting of gas, size- and composition-resolved aerosol, radiative, and meteorological parameters from the global through urban scales (<5-km grid spacing) was developed. The model treats multiple one-way-nested layers and multiple air quality and meteorological domains in each layer between the global and the urban scales. This latter feature allows forecast of air pollution and weather at several urban or regional sites during the same simulation. Regardless of the number of domains used during a single continuous simulation, the central memory required never exceeds 1.5 times and 2.1 times that of the largest domain for gas and gas/aerosol simulations, respectively. A submodule was developed for all domains to treat ground temperatures, latent heat fluxes, and sensible heat fluxes over subgrid soil types (with and without vegetation), water, sea ice, and urban areas. Urban areas are divided into road surfaces, rooftops, vegetation, and bare soil. Snow is treated over all surface types. The global-through-urban model is applied in a companion paper to study elevated ozone, ozone in national parks, and weather during a field campaign in northern and central California.
Patent•
07 Feb 2001
TL;DR: In this article, an air monitoring system is disclosed having at least one sensor for measuring data of an air quality parameter and a computer for storing the air quality parameters data received from the sensor.
Abstract: An air monitoring system is disclosed having an air monitoring unit with at least one sensor for measuring data of an air quality parameter and a computer for storing the air quality parameter data received from the sensor. The air monitoring unit may use an installed or a portable system, or a combination of both, for measuring the air quality parameters of interest. A remote data center may be provided, and the data may be uploaded to the data center from the unit by a communications media such as the Internet. Information or instructions may also be downloaded from the data center to the unit via the communications media for controlling or modifying the function of the unit. An expert system may be provided with the air monitoring system for controlling the unit. The information or instructions downloaded to the unit may be generated by the expert system.
TL;DR: AirGIS as discussed by the authors is a GIS-based model system for air quality management for big Danish cities that is based on the Danish operational street pollution model (OSPM), technical and cadastral digital maps and Danish national administrative databases on buildings, cadastres and populations.
Abstract: A new prototype model system named AirGIS has been developed to support local authorities in air quality management for big Danish cities. The system is based on the Danish operational street pollution model (OSPM), technical and cadastral digital maps and Danish national administrative databases on buildings, cadastres and populations. It applies a geographic information system (GIS). AirGIS estimates ambient air pollution levels at high temporal and spatial resolutions. The model system enables mapping of traffic emissions, air quality levels and human exposures at residence addresses, at workplace addresses and in streets. Mapping and scenario results can be compared with air quality limits. Impact assessment of traffic air pollution abatement measures can also be carried out.
TL;DR: In general, the maximum CO, SO2, NOx, and TSP values occurred during the winter with minimum values occurring during the summer, which can be attributed to a combination of meteorological conditions and photochemical activity in the region.
TL;DR: In this article, the authors presented estimates for air change (ventilation and infiltration) energy use in non-industrial buildings for 13 countries, and estimated financial expenditures, as well as carbon dioxide emissions associated with this energy use are indicated.
TL;DR: In this paper, the difference in the air quality that is perceived by the occupants (breathing zone) and that existing in the occupied zone as a whole was investigated in an environmental chamber with displacement ventilation system.
TL;DR: Although China has a relatively small number of motor vehicles, most of them are concentrated within metropolitan areas, and their emissions are closely related to urban air pollution problems in large cities.
Abstract: As the motor vehicle population in China continues to increase at an annual rate of ~15%, air pollution related to vehicular emissions has become the focus of attention, especially in large cities. There is an urgent need to identify the severity of this pollution in China. Based on an investigation into vehicle service characteristics, this study used a series of driving cycle tests of in-use Chinese motor vehicles for their emission factors in laboratories, which indicated that CO and HC emission factors are 5-10 times higher, and NOx 2-5 times higher, than levels in developed countries. The MOBILE5 model was adapted to the Chinese situation and used to calculate the emission of pollutants from motor vehicles. Results show that vehicle emission is concentrated in major cities, such as Beijing, Guangzhou, Shanghai, and Tianjin. Motor vehicle emissions contribute a significant proportion of pollutants in those cities, with contribution rates of CO and NOx greater than 80% and 40%, respectively, i...
TL;DR: In this article, the ambient air concentrations of many saturated and aromatic hydrocarbons were measured in several sites around an oil refinery, near the city of Corinth in Greece, during 1997.
TL;DR: A nested air quality prediction modeling system (NAQPMS) was developed to investigate the various processes that govern the loading of chemical species and anthropogenic aerosols at various scales of atmospheric motions in urban and regional scales as mentioned in this paper.
Abstract: A nested air quality prediction modeling system (NAQPMS) has been developed to investigate the various processes that govern the loading of chemical species and anthropogenic aerosols at various scales of atmospheric motions in urban and regional scales. The model employs flexible horizontal grid resolution with multiple multi-level nested grids with options for one-way and two-way nesting procedures in a spherical and terrain-following coordinate. The NAQPMS is driven using meteorological fields from the NCAR/Penn State Fifth-Generation Mesoscale Model (MM5). Hourly pollutant levels of 71 stations covering Taiwan are used to evaluate the modeling system. Case simulation of a high-ozone episode occurred during April 13–15 1999 shows that the technique of the model nesting is capable of affording more realistic temporal and spatial structures of concentration fields, processes and precursors.
TL;DR: In this paper, the United States National Ambient Air Quality Standard (NAAQS) for ozone was revised from a 1-h average of 0.12 parts per million (ppm) to an 8-h averaging of 0.08 pm.
TL;DR: In this article, a 3D long-range transport model for yellow sand, with an advanced size-dependent deflation module and driven by the NCAR/Penn State Fifth-Generation Mesoscale Model (MM5), is used to identify the long-term transport of yellow sand to Taiwan in April.
TL;DR: An atmospheric stability index for the evaluation of urban primary pollution, based on the elaboration of natural radioactivity data yielded by a stability monitor, has been developed in this paper, which determines the atmospheric concentration of the short-lived decay products of radon, whose emanation rate can be assumed to be constant in the time and space scale of observation.
TL;DR: A classification system based on gas emission characteristics and effluent concentrations of total phosphorus (P) and total sulfur (S) was devised and tested on 29 swine manure management systems in Iowa, Oklahoma, and North Carolina in an effort to elucidate functional characteristics of these systems.
Abstract: Gaseous emissions from swine (Sus scrofa) manure storage systems represent a concern to air quality due to the potential effects of hydrogen sulfide, ammonia, methane, and volatile organic compounds on environmental quality and human health. The lack of knowledge concerning functional aspects of swine manure management systems has been a major obstacle in the development and optimization of emission abatement technologies for these point sources. In this study, a classification system based on gas emission characteristics and effluent concentrations of total phosphorus (P) and total sulfur (S) was devised and tested on 29 swine manure management systems in Iowa, Oklahoma, and North Carolina in an effort to elucidate functional characteristics of these systems. Four swine manure management system classes were identified that differed in effluent concentrations of P and S, methane (CH 4 ) emission rate, odor intensity, and air concentration of volatile organic compounds (VOCs). Odor intensity and the concentration of VOCs in air emitted from swine manure management systems were strongly correlated (r 2 = 0.88). The concentration of VOC in air samples was highest with outdoor swine manure management systems that received a high input of volatile solids (Type 2). These systems were also shown to have the highest odor intensity levels. The emission rate for VOCs and the odor intensity associated with swine manure management systems were inversely correlated with CH 4 and ammonia (NH 3 ) emission rates. The emission rates of CH 4 , NH 3 , and VOCs were found to be dependent upon manure loading rate and were indirectly influenced by animal numbers.