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Acid deposition: State of science and technology. Summary report of the U. S. National Acid Precipitation Assessment Program
Abstract
The twenty-seven State-of-Science and State-of-Technology (SOS/T) Reports, published in 1990 as the definitive scientific and technical synthesis of information obtained during the first decade of the U.S. national Acid Precipitation Assessment Program (NAPAP), are summarized in the document. In most cases, these summaries were the final chapter of the complete SOS/T Report.
... While the representation of gas and aerosol dry deposition in many of these models is derived from the resistance framework introduced in Wesely and Hicks (1977) and Wesely (1989), its specific implementation can differ between models (Hardacre et al., 2015;Clifton et al., 2020a;Galmarini et al., 2021), and its use to represent aerosol dry deposition is an area of active model development (Saylor et al., 2019;Emerson et al., 2020;Pleim et al., 2022;Alapaty et al., 2022;Cheng et al., 2022). Likewise, the calculation of wet deposition fluxes in many models follows similar approaches to those used during initial acid deposition modeling (Chang et al., 1987;Irving and Smith, 1991;Hass et al., 1993), but differences exist in how models represent microphysics, precipitation, and aerosols. ...
The fourth phase of the Air Quality Model Evaluation International Initiative (AQMEII4) is conducting a diagnostic intercomparison and evaluation of deposition simulated by regional-scale air quality models over North America and Europe. In this study, we analyze annual AQMEII4 simulations performed with the Community Multiscale Air Quality Model (CMAQ) version 5.3.1 over North America. These simulations were configured with both the M3Dry and Surface Tiled Aerosol and Gas Exchange (STAGE) dry deposition schemes available in CMAQ. A comparison of observed and modeled concentrations and wet deposition fluxes shows that the AQMEII4 CMAQ simulations perform similarly to other contemporary regional-scale modeling studies. During summer, M3Dry has higher ozone (O3) deposition velocities (Vd) and lower mixing ratios than STAGE for much of the eastern US, while the reverse is the case over eastern Canada and along the US West Coast. In contrast, during winter STAGE has higher O3 Vd and lower mixing ratios than M3Dry over most of the southern half of the modeling domain, while the reverse is the case for much of the northern US and southern Canada. Analysis of the diagnostic variables defined for the AQMEII4 project, i.e., grid-scale and land-use-specific effective conductances and deposition fluxes for the major dry deposition pathways, reveals generally higher summertime stomatal and wintertime cuticular grid-scale effective conductances for M3Dry and generally higher soil grid-scale effective conductances (for both vegetated and bare soil) for STAGE in both summer and winter. On a domain-wide basis, the stomatal grid-scale effective conductances account for about half of the total O3 Vd during daytime hours in summer for both schemes. Employing land-use-specific diagnostics, results show that daytime Vd varies by a factor of 2 between land use (LU) categories. Furthermore, M3Dry vs. STAGE differences are most pronounced for the stomatal and vegetated soil pathway for the forest LU categories, with M3Dry estimating larger effective conductances for the stomatal pathway and STAGE estimating larger effective conductances for the vegetated soil pathway for these LU categories. Annual domain total O3 deposition fluxes differ only slightly between M3Dry (74.4 Tg yr−1) and STAGE (76.2 Tg yr−1), but pathway-specific fluxes to individual LU types can vary more substantially on both annual and seasonal scales, which would affect estimates of O3 damage to sensitive vegetation. A comparison of two simulations differing only in their LU classification scheme shows that the differences in LU cause seasonal mean O3 mixing ratio differences on the order of 1 ppb across large portions of the domain, with the differences generally being largest during summer and in areas characterized by the largest differences in the fractional coverages of the forest, planted and cultivated, and grassland LU categories. These differences are generally smaller than the M3Dry vs. STAGE differences outside the summer season but have a similar magnitude during summer. Results indicate that the deposition impacts of LU differences are caused by differences in the fractional coverages and spatial distributions of different LU categories and the characterization of these categories through variables like surface roughness and vegetation fraction in lookup tables used in the land surface model and deposition schemes. Overall, the analyses and results presented in this study illustrate how the diagnostic grid-scale and LU-specific dry deposition variables adopted for AQMEII4 can provide insights into similarities and differences between the CMAQ M3Dry and STAGE dry deposition schemes that affect simulated pollutant budgets and ecosystem impacts from atmospheric pollution.
... While the representation of gas and aerosol dry deposition in many of these models is derived from the resistance framework introduced in Wesely and Hicks (1977) and Wesely (1989), its specific implementation can differ between models (Hardacre et al., 2015;Galmarini et al., 2021) and its use to represent aerosol dry deposition is an area 50 of active model development (Saylor et al., 2019;Emerson et al., 2020;Pleim et al., 2022;Alapaty et al., 2022, Cheng et al., 2022. Likewise, the calculation of wet deposition fluxes in many models follows similar approaches as those used during initial acid deposition modeling (Chang et al., 1987;Irving and Smith, 1991;Hass et al., 1993) but differences exist in how models represent microphysics, precipitation, and aerosols. ...
The fourth phase of the Air Quality Model Evaluation International Initiative (AQMEII4) is conducting a diagnostic intercomparison and evaluation of deposition simulated by regional-scale air quality models over North America and Europe. In this study, we analyze annual AQMEII4 simulations performed with the Community Multiscale Air Quality Model (CMAQ) version 5.3.1 over North America. These simulations were configured with both the M3Dry and Surface Tiled Aerosol and Gas Exchange (STAGE) dry deposition schemes available in CMAQ. A comparison of observed and modeled concentrations and wet deposition fluxes shows that the AQMEII4 CMAQ simulations perform similarly to other contemporary regional-scale modeling studies. During summer, M3Dry has higher ozone (O3) deposition velocities (Vd) and lower mixing ratios than STAGE for much of the eastern U.S. while the reverse is the case over eastern Canada and along the West Coast. In contrast, during winter STAGE has higher O3 Vd and lower mixing ratios than M3Dry over most of the southern half of the modeling domain while the reverse is the case for much of the northern U.S. and southern Canada. Analysis of the diagnostic variables defined for the AQMEII4 project, i.e. grid-scale and land-use (LU) specific effective conductances and deposition fluxes for the major dry deposition pathways, reveals generally higher summertime stomatal and wintertime cuticular grid-scale effective conductances for M3Dry and generally higher soil grid-scale effective conductances (for both vegetated and bare soil) for STAGE in both summer and winter. On a domain-wide basis, the stomatal grid-scale effective conductances account for about half of the total O3 Vd during daytime hours in summer for both schemes. Employing LU-specific diagnostics, results show that daytime Vd varies by a factor of 2 between LU categories. Furthermore, M3Dry vs. STAGE differences are most pronounced for the stomatal and vegetated soil pathway for the forest LU categories, with M3Dry estimating larger effective conductances for the stomatal pathway and STAGE estimating larger effective conductances for the vegetated soil pathway for these LU categories. Annual domain total O3 deposition fluxes differ only slightly between M3Dry (74.4 Tg/year) and STAGE (76.2 Tg/yr), but pathway-specific fluxes to individual LU types can vary more substantially on both annual and seasonal scales which would affect estimates of O3 damages to sensitive vegetation. A comparison of two simulations differing only in their LU classification scheme shows that the differences in LU cause seasonal mean O3 mixing ratio differences on the order of 1 ppb across large portions of the domain, with the differences generally largest during summer and in areas characterized by the largest differences in the fractional coverages of the forest, planted/cultivated, and grassland LU categories. These differences are generally smaller than the M3Dry vs. STAGE differences outside the summer season but have a similar magnitude during summer. Results indicate that the deposition impacts of LU differences are caused both by differences in the fractional coverages and spatial distributions of different LU categories as well as the characterization of these categories through variables like surface roughness and vegetation fraction in look-up tables used in the land-surface model and deposition schemes. Overall, the analyses and results presented in this study illustrate how the diagnostic grid-scale and LU-specific dry deposition variables adopted for AQMEII4 can provide insights into similarities and differences between the CMAQ M3Dry and STAGE dry deposition schemes that affect simulated pollutant budgets and ecosystem impacts from atmospheric pollution.
... More so, industrial manufacturing processes are also responsible for acidic emissions. 24 Exposure to higher concentrations of sulfur oxides generates breathing problems for asthmatic patients, while its less exposure can as well cause whizzing, shortness of breath and chest tightness. SO 2 is responsible for bronchitis, lung cancer and emphysema in humans. ...
Population growth, Urbanization and Industrialization created many social economic environmental and health issues for Pakistan. Industries are major sources of environmental pollution specially water and air pollution due to lack of advanced technologies. This review mainly focused on the emission of heavy metals from industries, their detection methods which are available in Pakistan. Heavy metals are released into the environment through different industries and combine with other pollutants to form secondary compounds which are even more harmful to the environment. When these heavy metals combine with water and soil, they change the soil and water ecosystem functions, plant growth mechanism and disrupt the many other functions of soil. More so, groundwater contamination owing to these metals poses many serious health problems in humans and animals, and when this groundwater mixes with sea water, it threatens the health of aquatic lives and food species growing in water and bioaccumulated in the food chain of biological system. By using advanced detection, controlled and treatment technologies, ecosystem can be saved from the possible problem of heavy metal emissions and contamination.
... More so, industrial manufacturing processes are also responsible for acidic emissions. 24 Exposure to higher concentrations of sulfur oxides generates breathing problems for asthmatic patients, while its less exposure can as well cause whizzing, shortness of breath and chest tightness. SO 2 is responsible for bronchitis, lung cancer and emphysema in humans. ...
Population growth, Urbanization and Industrialization created many social economic
environmental and health issues for Pakistan. Industries are major sources of environmental
pollution specially water and air pollution due to lack of advanced technologies. This review
mainly focused on the emission of heavy metals from industries, their detection methods
which are available in Pakistan. Heavy metals are released into the environment through
different industries and combine with other pollutants to form secondary compounds which
are even more harmful to the environment. When these heavy metals combine with water
and soil, they change the soil and water ecosystem functions, plant growth mechanism and
disrupt the many other functions of soil. More so, groundwater contamination owing to
these metals poses many serious health problems in humans and animals, and when this
groundwater mixes with sea water, it threatens the health of aquatic lives and food species
growing in water and bioaccumulated in the food chain of biological system. By using
advanced detection, controlled and treatment technologies, ecosystem can be saved from
the possible problem of heavy metal emissions and contamination
... More so, industrial manufacturing processes are also responsible for acidic emissions. 24 Exposure to higher concentrations of sulfur oxides generates breathing problems for asthmatic patients, while its less exposure can as well cause whizzing, shortness of breath and chest tightness. SO 2 is responsible for bronchitis, lung cancer and emphysema in humans. ...
Population growth, Urbanization and Industrialization created many social economic environmental and health issues for Pakistan. Industries are major sources of environmental pollution specially water and air pollution due to lack of advanced technologies. This review mainly focused on the emission of heavy metals from industries, their detection methods which are available in Pakistan. Heavy metals are released into the environment through different industries and combine with other pollutants to form secondary compounds which are even more harmful to the environment. When these heavy metals combine with water and soil, they change the soil and water ecosystem functions, plant growth mechanism and disrupt the many other functions of soil. More so, groundwater contamination owing to these metals poses many serious health problems in humans and animals, and when this groundwater mixes with sea water, it threatens the health of aquatic lives and food species growing in water and bioaccumulated in the food chain of biological system. By using advanced detection, controlled and treatment technologies, ecosystem can be saved from the possible problem of heavy metal emissions and contamination.
... 1986). Two key research programmes were the Surface Water Acidification Programme (1985( , Mason, 1990) funded by the UK (GBP 5 million) and the National Acid Precipitation Assessment Program (1980( , Irving, 1991 funded by the US government (USD 17 million). At the end of the 1980s, the critical load concept was developed as an effectbased approach for emission reductions (Nilsson and Grennfelt, 1988) and served as a link between science and policy within the framework of the UNECE-CLRTAP (the United Nations Economic Commission for Europe -Convention on Long-Range Transport of Air Pollutants) (Lidskog and Sundqvist, 2002). ...
Soil and water acidification was internationally recognised as a severe environmental problem in the late 1960s. The interest in establishing “critical loads” led to a peak in weathering research in the 1980s and 1990s, since base cation weathering is the long-term counterbalance to acidification pressure. Assessments of weathering rates and associated uncertainties have recently become an area of renewed research interest, this time due to demand for forest residues to provide renewable bioenergy. Increased demand for forest fuels increases the risk of depleting the soils of base cations produced in situ by weathering. This is the background to the research programme Quantifying Weathering Rates for Sustainable Forestry (QWARTS), which ran from 2012 to 2019. The programme involved research groups working at different scales, from laboratory experiments to modelling. The aims of this study were to (1) investigate the variation in published weathering rates of base cations from different approaches in Sweden, with consideration of the key uncertainties for each method; (2) assess the robustness of the results in relation to sustainable forestry; and (3) discuss the results in relation to new insights from the QWARTS programme and propose ways to further reduce uncertainties. In the study we found that the variation in estimated weathering rates at single-site level was large, but still most sites could be placed reliably in broader classes of weathering rates. At the regional level, the results from the different approaches were in general agreement. Comparisons with base cation losses after stem-only and whole-tree harvesting showed sites where whole-tree harvesting was clearly not sustainable and other sites where variation in weathering rates from different approaches obscured the overall balance. Clear imbalances appeared mainly after whole-tree harvesting in spruce forests in southern and central Sweden. Based on the research findings in the QWARTS programme, it was concluded that the PROFILE/ForSAFE family of models provides the most important fundamental understanding of the contribution of weathering to long-term availability of base cations to support forest growth. However, these approaches should be continually assessed against other approaches. Uncertainties in the model approaches can be further reduced, mainly by finding ways to reduce uncertainties in input data on soil texture and associated hydrological parameters but also by developing the models, e.g. to better represent biological feedbacks under the influence of climate change.
... The NAPAP task force spent a decade studying atmospheric deposition and its effects on aquatic and terrestrial ecosystems. The resulting summary report (Irving 1991) was a major contribution to the technical understanding of acid rain. In 1984, the U.S. Forest Service, the U.S. Environmental Protection Agency (EPA), and private forest industry combined resources to create the Forest Response Program (FRP) to conduct research on forested ecosystems for NAPAP (U.S. ...
Forest monitoring systems have historically been designed to obtain data needed for timber management, but in the past few decades forests have been increasingly viewed as holistic systems that are best monitored with an integrated approach which includes the ecological and social aspects of forests (Riitters and Tkacz 2004). The demand for more comprehensive and science-based information has led the U.S. Forest Service to assemble a monitoring program that is based on a cooperative and integrated approach to gathering and reporting information on many aspects of forest health. This paper provides a brief history of the U.S. Forest Health Monitoring (FHM) Program, a summary of the conceptual approaches, and a description of current operations. Additional details are available on the Program's web site at http://fhm.fs.fed.us/. History of Forest Health Monitoring Beginning in the late 1970's, widely reported declines in the health of European forests spawned much debate that similar symptoms observed in the U.S. might be attributed to air pollution and acid rain (Peterson and Shriner 2004). The lack of science-based information necessary to respond to these allegations led the U.S. Congress to create an interagency task force to study the issue. The National Acid Precipitation Assessment Program (NAPAP) was thus established in 1980. The NAPAP task force spent a decade studying atmospheric deposition and its effects on aquatic and terrestrial ecosystems. The resulting summary report (Irving 1991) was a major contribution to the technical understanding of acid rain. In 1984, the U.S. Forest Service, the U.S. Environmental Protection Agency (EPA), and private forest industry combined resources to create the Forest Response Program (FRP) to conduct research on forested ecosystems for NAPAP (U.S. Department of Agriculture 1989). As part of its contribution to this cooperative research effort, the Forest Service launched the National Vegetation Survey (NVS). One objective of the NVS was to design a long-term approach to forest health monitoring. While the Forest Service and EPA were collaborating in the Forest Response Program, the EPA Science Advisory Board initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor the condition of the nation's major ecological resources by using a series of ecological indicators (Thornton et al. 1993; Hunsaker and Carpenter 1990). EMAP targeted seven ecological resources for monitoring, one of which was forests. Facilitated by the pre-existing collaborative relationship between the Forest Service and the EPA, the NVS and EMAP-Forest programs were combined in 1990 to create the U.S. Forest Health Monitoring Program. A
... open-top chambers) revealed that exposure to ambient levels of 0 3 could induce visible foliar injuries in many native tree species such as red maple (Acer rubrum), black cherry (Prunus serotin), yellow-poplar (Liriodendron tulipifera) and table mountain pine (Pinus pungens), and these 03-specific symptoms are similar to those observed at mountainous areas with forest decline (Kress and Skelly, 1982;Duchelle et al., 1982;Skelly et al., 1983;Neufeld et al., 1992). From the results of several experimental studies conducted by National Acid Precipitation Assessment Program (NAPAP), main cause of some forest decline in North America, for example, pine species in Sierra Nevada Mountains and red spruce (Picea rubens) in Appalachian Mountains, is considered to be high 0 3 pollution (Irving, 1991;Chevone and Linzon, 1988;McLaughlin and Percy, 1999). Furthermore, several model studies suggested that forestry production in North America has already been reduced in the range of 0-10% per year by the current levels of 0 3 (Pye, 1988;Hogsett et al., 1997;Chappelka and Samuelson, 1998). ...
... 15,34 Modeling work by the National Acid Precipitation Assessment Program suggest that this remains a reasonable approximation when aqueous processes are included. 54 Therefore, decreases in SO 2 emissions are likely to be effective at reducing PM 2.5 in the MCMA. The effects of changes in NO x emissions are complicated by oxidant chemistry and cannot be easily assessed without an air quality model. ...
Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.
... Nitrogen deposition is of particular importance in these ecosystems. Emissions of nitrogen oxides are increasing in the western US (Placetalso cause major changes in aquatic ecosystems (Irving 1992; Schindler 1988). The effect of emissions from snowmobile activity on air quality and deposition in high elevation ecosystems has been studied primarily at Yellowstone National Park (YNP) in NW Wyoming. ...
A study was begun in the winter of 2000–2001 and continued through the winter of 2001–2002 to examine air quality at the Green Rock snowmobile staging area at 2,985 m elevation in the Snowy Range of Wyoming. The study was designed to evaluate the effects of winter recreation snowmobile activity on air quality at this high elevation site by measuring levels of nitrogen oxides (NOx
, NO), carbon monoxide (CO), ozone (O3) and particulate matter (PM10 mass). Snowmobile numbers were higher weekends than weekdays, but numbers were difficult to quantify with an infrared sensor. Nitrogen oxides and carbon monoxide were significantly higher weekends than weekdays. Ozone and particulate matter were not significantly different during the weekend compared to weekdays. Air quality data during the summer was also compared to the winter data. Carbon monoxide levels at the site were significantly higher during the winter than during the summer. Nitrogen oxides and particulates were significantly higher during the summer compared to winter. Nevertheless, air pollutants were well dispersed and diluted by strong winds common at the site, and it appears that snowmobile emissions did not have a significant impact on air quality at this high elevation ecosystem. Pollutant concentrations were generally low both winter and summer. In a separate study, water chemistry and snow density were measured from snow samples collected on and adjacent to a snowmobile trail. Snow on the trail was significantly denser and significantly more acidic with significantly higher concentrations of sodium, ammonium, calcium, magnesium, fluoride, and sulfate than in snow off the trail. Snowmobile activity had no effect on nitrate levels in snow.
We present in this technical note the research protocol for phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII4). This research initiative is divided into two activities, collectively having three goals: (i) to define the current state of the science with respect to representations of wet and especially dry deposition in regional models, (ii) to quantify the extent to which different dry deposition parameterizations influence retrospective air pollutant concentration and flux predictions, and (iii) to identify, through the use of a common set of detailed diagnostics, sensitivity simulations, model evaluation, and reduction of input uncertainty, the specific causes for the current range of these predictions. Activity 1 is dedicated to the diagnostic evaluation of wet and dry deposition processes in regional air quality models (described in this paper), and Activity 2 to the evaluation of dry deposition point models against ozone flux measurements at multiple towers with multiyear observations (to be described in future submissions as part of the special issue on AQMEII4). The scope of this paper is to present the scientific protocols for Activity 1, as well as to summarize the technical information associated with the different dry deposition approaches used by the participating research groups of AQMEII4. In addition to describing all common aspects and data used for this multi-model evaluation activity, most importantly, we present the strategy devised to allow a common process-level comparison of dry deposition obtained from models using sometimes very different dry deposition schemes. The strategy is based on adding detailed diagnostics to the algorithms used in the dry deposition modules of existing regional air quality models, in particular archiving diagnostics specific to land use-land cover (LULC) and creating standardized LULC categories to facilitate cross-comparison of LULC-specific dry deposition parameters and processes, as well as archiving effective conductance and effective flux as means for comparing the relative influence of different pathways towards the net or total dry deposition. This new approach, along with an analysis of precipitation and wet deposition fields, will provide an unprecedented process-oriented comparison of deposition in regional air quality models. Examples of how specific dry deposition schemes used in participating models have been reduced to the common set of comparable diagnostics defined for AQMEII4 are also presented.
We present in this technical note the research protocol for Phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII4). This research initiative is divided in two activities, collectively having three goals: (i) to define the current state of the science with respect to representations of wet and especially dry deposition in regional models, (ii) to quantify the extent to which different dry deposition parameterizations influence retrospective air pollutant concentration and flux predictions, and (iii) to identify, through the use of a common set of detailed diagnostics, sensitivity simulations, model evaluation, and reducing input uncertainty, the specific causes for the current range of these predictions. Activity 1 is dedicated to the diagnostic evaluation of wet and dry deposition processes in regional air quality models (described in this paper), and Activity 2 to the evaluation of dry deposition point models against ozone flux measurements at multiple towers with multiyear observations (Part 2). The scope of these papers is to present the scientific protocols for AQMEII4, as well to summarize the technical information associated with the different dry deposition approaches used by the participating research groups of AQMEII4. In addition to describing all common aspects and data used for this multi-model evaluation activity, most importantly, we present the strategy devised to allow a common process-level comparison of dry deposition obtained from models using sometimes very different dry deposition schemes. The strategy is based on adding detailed diagnostics to the algorithms used in the dry deposition modules of existing regional air quality models, in particular archiving land use/land cover (LULC)-specific diagnostics and creating standardized LULC categories to facilitate cross-comparison of LULC-specific dry deposition parameters and processes, as well as archiving effective conductance and effective flux as means for comparing the relative influence of different pathways towards the net or total dry deposition. This new approach, along with an analysis of precipitation and wet deposition fields, will provide an unprecedented process-oriented comparison of deposition in regional air-quality models. Examples of how specific dry deposition schemes used in participating models have been reduced to the common set of comparable diagnostics defined for AQMEII4 are also presented.
Soil and water acidification was first recognised as a severe environmental problem in the 1970s. The interest in establishing critical loads led to a peak in weathering research in the 1980s, since weathering is the long-term counterbalance to acidification pressure. Assessments of weathering rates and associated uncertainties have recently become an area of renewed research interest, this time due to demand for more harvest to provide renewable bioenergy. Increased demand for forest fuels increases the risk of depleting the soils of base cations produced in situ by weathering. This is the background to the research programme Quantifying Weathering Rates for Sustainable Forestry (QWARTS), which ran from 2012 to 2019. The programme involved research groups working at different scales, from lab experiments to extensive modelling. The aims of this paper are to summarise the state of knowledge about weathering rates in Swedish forest soils at different scales, with an emphasis on the knowledge added by the QWARTS programme, to discuss the uncertainties in relation to sustainable forestry, and to highlight knowledge gaps where further research is needed. The variation at single-site level was large, but most sites could be placed reliably in broader classes of weathering rates. At regional to national level, the results from the different approaches were in general agreement. Comparisons of base cation losses after stem-only and whole-tree harvesting showed sites with clear imbalances between weathering supply and harvest losses, and other sites where variation in weathering rates from different approaches obscured the overall balance. Clear imbalances appeared mainly after whole-tree harvesting in spruce forests in southern and central Sweden. Research findings in the QWARTS programme support the continued use of the PROFILE/ForSAFE family of models, but it is important to continue comparisons between these and other approaches. Uncertainties in the model approaches can be further reduced, mainly by finding ways to reduce uncertainties in input data on soil texture and associated hydrological parameters. Another way to reduce uncertainties is by developing the models to better represent the delivery of weathering products to runoff waters and biological feedbacks under the influence of climate change.
To understand the observed characteristics of long-range transport of pollutants in East Asia, an atmospheric transport model which includes detailed chemical reactions, the STEM (Sulfate Transport Eulerian Model; Carmichael et al, 1986), was applied. Model includes the detailed NH3-NO3-NH4 NO3 thermodynamical equilibrium mechanism and the heterogeneous reaction from SO2 (gas) to aerosol sulfate. Numerical simulation with STEM code was conducted from Feb. 4 to Feb. 28, 1992 and then the numerical results were compared with detailed high-time resolution (4-8 hour interval) aerosol monitoring data set at Tsushima, Ogori and Seoul.
The STEM model successfully simulated the typical time variation of observed concentrations (both SO4²⁻ and NO3⁻). It was found that wind pattern variations associated with a synoptic scale pressure system are extremely important for the transport of pollutants. Sensitivity analysis shows that most of the observation data located within the heterogeneous reaction rate 0.5-2.0%/h. Model predicted the large fraction of HNO3 in Tsushima Island even in winter, which is because of the shortcoming of NH3 during the long-range transport over the ocean. Analysis of total dry deposition amount during the period of numerical simulation is also discussed.
The Clean Air Act Amendments of 1977 designated national parks and wilderness areas larger than 1894 ha to be class I areas for air quality management, setting more restrictive criteria than the National Ambient Air Quality Standards. Class I areas are afforded the greatest degree of air quality protection under the Clean Air Act of 1970. In recent years, several studies have documented air pollution effects in the Great Smoky Mountains National Park (GSMNP), the second-largest class I area in the eastern United States. Air pollution problems of greatest concern in the GSMNP are effects of acid deposition, visibility impairment, and tropospheric ozone. Several recent events have increased concerns about air quality management in the class I area of the GSMNP. A forum, sponsored by the Southern Appalachian Man and the Biosphere Cooperative (SAMAB), was held in March 1992, which involved representative parties-at-interest and began to address strategies for better management of air resources in the Southern Appalachians. This paper summarizes those discussions and recommendations and reports actions occurring as a result of the forum. Another objective of this paper is to present a conceptual framework for more effective management of the class I area of the GSMNP. 20 refs., 4 figs., 5 tabs.
We report aerosol SO42− measurements from 1979 to 1996 at Whiteface Mountain located in the Adirondack Mountains and from 1983 at Mayville, in western New York State. From 1981 to 1991 SO42− decreased, ∼3% per year. Reductions of nearly 47% in SO42− and total sulfur concentrations at Whiteface Mountain, and about 30% at Mayville, were observed during 1995 to 96 compared with the mean levels during 1981–91, while the upwind SO2 emissions in the Midwestern United States decreased by 36%. Linear relationships between SO42− and total sulfur concentrations and the SO2 emissions were observed for the entire period. The mean ratio of SO42− concentrations to SO2 emissions for the eighteen year period at Whiteface Mountain is 0.11 ± 0.014 and for thirteen years at Mayville is 0.23± 0.014 µg SO42−/m³ per 10³ metric tons SO2 emitted per day. The data suggest that the observed relationship could be used to predict decreases in atmospheric SO42− levels based on SO2 emissions several years hence. Furthermore, it appears feasible to develop an empirical source-receptor relationship if similar data were acquired from a network of strategically located sampling sites.
The Eulerian Model Evaluation Field Study (EMEFS), perhaps the most ambitious study of its type ever undertaken, gathered routine (daily or hourly) precipitation chemisny, meteorology and air quality data, covering over 21 variables, at up to 137 sites from five combined networks in two countries for two years. Binational intensive measurements were made from up to five aircraft and at six ground stations for several-week periods. In addition, real-time hourly average SO2 and NOx emissions estimates for the 200 largest point sources in eastern Nonh America were made throughout the study in the U.S. and during intensives in Canada. This sweeping scope posed many planning, organizational, and procedural challenges --many of which were met successfully and some, not so successfully. Among the successes were an effective oversight and management structure and a quality assurance program that led to a data capture rate typically exceeding 90%, allowing relatively tight uncertainty estimates to be associated with the measurement data. The primary failure, loss of all the gaseous nitric acid and ammonia data from transition flow reactors, could be traced to reliance on measurement technology that had not been field-proven. This resulted in having to estimate concennations of these gases from the filter pack data, in spite of their variable biases.
Bioavailability of metals to aquatic plants is dependent on many factors including ambient metal concentration, pH of soil or water, concentration of ligands, competition with other metals for binding sites, and mode of exposure. Plants may be exposed to metals through water, air, or soil, depending on growth form. This paper examines the influence of soil type under two regimens of water acidification on metal uptake by four species of aquatic macrophytes: smartweed (Polygonum sagittatum), burreed (Sparganium americanum), pondweed (Potamogeton diversifolius), and bladderwort (Utricularia vulgaris) in constructed, experimentally acidified wetlands. Soil types consisted of a comparatively high-metal clay or a lower-metal sandy loam. Each pond was either acidified to pH ca. 4.8–5.3 or allowed to remain circumneutral. Metal concentrations tended to be higher in the submerged bladderwort and pondweed than in the emergent burreed and smartweed. Soils were important to plant metal concentrations in all species, but especially in the emergents. Acidification influenced plant concentrations of some metals and was especially important in the submerged pondweed. Bioaccumulation of metals occurred for Mn, B, Sr, Ba, and Zn, compared to soil concentrations.
As part of an experimental study of air pollution effects on tree growth and health, we combined process studies with an ecosystem approach to evaluate the effects of acidic deposition on soil acidification, nutrient cycling and proton fluxes in miniature red spruce ecosystems. Ninety red spruce saplings were transplanted into 1-m diameter pots containing reconstructed soil profiles and exposed to simulated acid rain treatments of pH 3.1, 4.1 and 5.1 for four consecutive growing seasons. All the principal fluxes of the major elements were measured.
During the first year of treatments, the disturbance associated with the transplanting of the experimental trees masked any treatment effects by stimulating N mineralization rates and consequent high N03− cation, and H+ flux through the soil profile. In subsequent years, leaching of base cations and labile Al was accelerated in the most intensive acid treatment and corresponding declines in soil pH and exchangeable pools of Ca and Mg and increases in exchangeable Al concentrations were observed in the organic horizon. Leaching of Ca2+ and Mg2+ also was significantly higher in the pH 4.1 than in the pH 5.1 treatment. Flux of Ca from foliage and soil was increased in response to strong acid loading and root uptake increased to compensate for foliar Ca losses. In contrast, K cycling was dominated by root uptake and internal cycling and was relatively insensitive to strong acid inputs. Cation leaching induced by acidic deposition was responsible for the majority of H+ flux in the pH 3.1 treatment in the organic soil horizon whereas root uptake accounted for most of the H+ flux in the pH 4.1 and 5.1 treatments. Although no measurable effects on tree nutrition or health were observed, base cation leaching was significantly accelerated by acidic deposition, even at levels below that observed in the eastern U.S., warranting continued concern about acid deposition effects on the soil base status of forested ecosystems.
The method of single point, single application liming has been studied as a means of mitigating anthropogenic acid in trout streams in Virginia. Three critically acid sensitive streams were dosed with a total of five applications of limestone sand and monitored before, during and after the treatments to assess changes in water chemistry and biota. Limestone treatments of 8 to 50 tons (particle sizes 150–1000 m), with the amounts based on sulfate deposition loading and existent stream water chemistry, were used to restore lost acid neutralizing capacity (ANC). Contact time between the limestone bed in the stream bottom and the water was the limiting factor affecting the degree of treatment with bed length primarily controlled by the gradient of the stream at the dosing site. A single site application was able to restore approximately 2/3 of the ANC. Exponential fits of limestone consumption data were used to predict that treaments of similar streams would last from two five years before reliming was necessary. Both total and monomeric aluminum levels were reduced up to 50%, and aquatic biota increased below the treatment sites. Post-liming average values for the three streams were pH 6.66, 82.7 eq L–1 ANC and 2.63 mg L–1 Ca. The average ANC improvement suggests that some 88% of the native trout streams in Virginia, which average 29 eq L–1 ANC reduction from acid deposition, could be temporarily restored using single application liming.
The collocation of three national networked programs NADP, EPA's CASTNET, and the Forest Service's IMPROVE Module A, within a few hundred meters of each other in the pristine Medicine Bow forest of Wyoming has made it possible to assess the total amount of sulfur and nitrogen deposition, both wet and dry for this alpine/subalpine ecosystem. Additional sites within a few kilometers add spatial depth to this study. Wet deposition assessed using NADP data accounts for 1 to a little over 3 kg ha−1 yr−1 for both nitrogen and sulfur; however, annual trends for the two species differ. Dry deposition assessed using both CASTNET (a.k.a. NDDN) and IMPROVE (for sulfur) indicates 1–2 kg ha−1 yr−1 for nitrogen but less than 1 kg ha−1 yr−1 for sulfur. The overall trend of wet plus dry for nitrogen has been downward from 5 kg ha−1 yr−1 in 1989 to 3.6 kg ha−1 yr−1 in 1994, while varying between 2 and under 4 kg ha−1 yr−1 for sulfur. This paper introduces the sites and presents the three programs and the analysis approach. Spatial comparisons between sites are investigated. Weekly data are analyzed from three NADP sites, separated horizontally 6.8 and 2.4 km and vertically 430 and 98 m from the highest elevation site. The site comparisons demonstrate that winter season data requires careful analysis due to the vagaries of inefficient precipitation collection during high winds and snow fall.
Atmospheric deposition of nitrogen (AD-N) is a significant source of nitrogen enrichment to nitrogen (N)limited estuarine and coastal waters downwind of anthropogenic emissions. Along the eastern U.S. coast and eastern Gulf of Mexico, AD-N currently accounts for 10 % to over 40 % of new N loading to estuaries. Extension of the regional acid deposition model (RADM) to coastal shelf waters indicates that 11, 5.6, and 5.6 kg N ha �1 may be deposited on the continental shelf areas of the northeastern U.S. coast, southeast U.S. coast, and eastern Gulf of Mexico, respectively. AD-N approximates or exceeds riverine N inputs in many coastal regions. From a spatial perspective, AD-N is a unique source of N enrichment to estuarine and coastal waters because, for a receiving water body, the airshed may exceed the watershed by 10–20 fold. AD-N may originate far outside of the currently managed watersheds. AD-N may increase in importance as a new N source by affecting waters downstream of the oligohaline and mesohaline estuarine nutrient filters where large amounts of terrestrially-supplied N are assimilated and denitrified. Regionally and globally, N deposition associated with urbanization (NO x, peroxyacetyl nitrate, or PAN) and agricultural expansion (NH 4 and possibly organic N) has increased in coastal airsheds. Recent growth and intensification of animal (poultry, swine, cattle) operations in the midwest and mid-Atlantic regions have led to increasing amounts of NH 4 emission and deposition, according
The paper examines the tropospheric aerosol record obtained over the period 1971 to 1990, during which high-altitude balloons with optical particle counters were launched at Laramie, Wyoming, in a long-term study of the stratospheric sulfate aerosol layer. All aerosol particle size ranges display pronounced seasonal variations, with the condensation nuclei concentration and the optically active component showing a summer maximum throughout the troposphere. Mass estimates, assuming spherical sulfate particles, indicate an average column mass between altitudes of 2.5 and 10 km of about 4 and 16 mg/sq m in winter and summer, respectively. Calculated optical depths vary between 0.01 and 0.04 from winter to summer; the estimated mass scattering cross section is about 3 sq m/g throughout the troposphere. There is evidence for a decreasing trend of 1.6-1.8 percent/yr in the optically active tropospheric aerosol over the past 20 yr, which may be related to a similar reduction in SO2 emission in the U.S. over this period.
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