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Final Report: Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
EPA Grant Number: R825433C022Subproject: this is subproject number 022 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
Investigators: Carroll, John
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992)
Research Category: Center for Ecological Health Research , Targeted Research
Description:
Objective:The objectives of this research project were to document the regional and temporal distribution of several warm season air pollutants (ozone, NOy, particles, ammonia, and other nitrogen containing compounds), and to estimate the exposure of these pollutants to the forests and surface waters in the Sierra Nevada. We used three approaches in pursuit of our objectives: (1) analysis of existing databases; (2) numerical modeling of fluid dynamical and chemical processes in the atmosphere; and (3) aircraft-borne instrumentation to obtain detailed information in selected geographic areas.
Summary/Accomplishments (Outputs/Outcomes):We analyzed various public domain databases such as Project Forest Ozone Response Study, which includes several measures of foliar injury and continuous meteorological and ozone concentration data at 11 sites in the Sierra foothills, distributed from Mt. Lassen in the north to Sequoia National Park in the south. From these data, we developed exposure response relationships for foliar injury in response to Jeffery and ponderosa pine. Foliar injury appears to be significantly correlated with ozone exposure, especially when that exposure is averaged over 14-24 hours. We found that injury was in plots at which the average daily 1-hour ozone maximum was as low as 80 ppbv. Although the consensus of the research community is that ozone damage to plants occurs primarily to the cells within the stomata as a result of the respiring of polluted air, we found significant injury at sites where high ozone concentrations occur primarily at night. Thus, stomatal conductance is either not zero at night, or it does not regulate the rate of ingestion of ozone.
We used another public domain database, which contains air quality data and various aggregate metrics compiled by the California Air Resources Board, to examine long-term trends using the mean of the highest concentrations of ozone and particulate matter (PM10) on the 30 worst days of each year. We also used county population figures coupled with county-specific air quality data to attempt to correlate population trends with air quality trends (Sahoto, 2002). To assess wind patterns and identify any climatologically significant wind regimes and their frequency, we analyzed surface wind data for many sites in the Sacramento Valley and the Sierra foothills (Zaremba and Carroll, 1998). An analysis of long-term trends showed that emission controls have reduced worst-case events in traditionally highly polluted areas, but these areas are still very polluted. In the Sierra foothills, ozone concentrations have been increasing in recent years. We believe that these trends reflect the significant decease in emissions resulting from control technology—especially the three-way catalytic systems on automobiles. However, although emissions per mile driven have decreased, rapid population growth in previously rural locations, such as the Central Valley and foothills, has greatly increased the total emissions in these areas in recent years. Trends in ozone concentrations within the Tahoe Basin do not mimic those in the Central Valley or in the Sierra Foothills, but closely follow those seen in the rural and remote northeastern corner of California.
An analysis of the wind statistics in and around the Sacramento Valley confirmed the existence of three major, repeatable wind regimes during the warm season. The flow is dominated by an extended sea breeze and inflow of marine air into the Central Valley (72 percent of days between May 1 and September 30, 1991), with moderate pollution levels and strong daytime upslope flow over the Sierra foothills. North to northwest winds prevailed on 14 percent of the days with low pollution and weak mountain valley winds. Calm and transitional winds were found on 14 percent of the days, which had hot temperatures (38-43°C), shallow mixing depths, high pollution concentrations, and weak slope winds. When the marine intrusion replaces the stagnant regime, a mass of heavily polluted air moves upslope and over the Sierra, accounting for short-lived episodes of very high pollutant concentrations observed over the high Sierra.
We used numerical modeling techniques to simulate relevant atmospheric phenomena affecting the transport, diffusion, and chemical transformation of pollutants. Our model simulations illustrated the complexity of interactions between the evolving planetary boundary layer and the large-scale wind systems, as modulated by local sea breezes and mountain valley winds. The boundary layer-chemical model results are fully consistent with observed behavior of the atmospheric boundary layer and with generally observed pollutant distributions. The model runs mimic the main features of the observed evolution of the concentrations of primary and secondary pollutant species, including the development of highly polluted, elevated nocturnal layers and the increased ozone production on the third and fourth days of a pollution episode.
Lastly, we developed and utilized aircraft-borne instrumentation systems to obtain high-resolution three-dimensional observations of meteorological and air quality variables over the foothills and within the Lake Tahoe Basin. Aircraft data from the Sacramento plume study were used to document the time-space evolution and dispersion of the pollutant plume from that area, as well to establish the typical eastern limit of the upslope propagation. Because ozone is a secondary pollutant, we expected its maximum concentration to occur downwind from the areas of maximum emissions. As hypothesized, these data show that the maximum concentrations of ozone are found 20 to 60 km downwind of the city, and are significantly higher than the maximum ozone concentrations found in the urban area on the same day. Data from aircraft sampling in the Tahoe Basin indicate that pollutant concentrations are much lower than those in the Central Valley and foothills to the west, and are generally well mixed within deep vertical layers within the basin.
The following activities were accomplished:
• Visible foliar ozone injury to sensitive pine species occurs at Sierra Nevada sites that have average daily 1-hour maximum concentrations in the 80 to 100-ppbv range. This information is crucial for the setting of secondary air quality standards by environmental regulatory agencies and policymakers.
• Diurnal patterns of ozone exposure vary greatly among locations—even those in close proximity to each other. Hence, investigators cannot use simple statistical or regression models based on altitude or latitude to describe the geographic distribution of ozone and ozone exposure.
• Ozone concentrations in severely impacted urban areas have declined over the past 20 years, but have remained flat or have been increasing at historically rural and remote sites. Policymakers and planners need to explicitly address this issue as the population expands into rural areas.
• Pollutant transport to the Sierra occurs because of upslope winds generated by daytime heating of the slopes, as modulated by the large-scale flow. High ozone impacts are expected downwind of major source areas, especially following stagnation periods. Air quality implementation plans need to use these types of climatological wind scenarios to predict mitigation effectiveness.
• Ozone concentrations in the Tahoe Basin rarely exceed 100 ppbv. When they do exceed this concentration, they appear to be short lived. Such high concentrations likely result from the transit of highly polluted air flushed out of the Central Valley following a period of stagnation. Hence, efforts to reduce ozone precursor emissions in the basin will only marginally reduce peak ozone concentrations.
• Concentrations of nitrogen compounds (primarily ammonia and ammonium) are two to four times higher over the western Sierra then in the Tahoe Basin. Although these appear to be the major nitrogen species deposited from the atmosphere, they are transported from the west and undergo significant dilution before entering the basin. Environmental management agencies should be aware that mitigation efforts in the basin would have little net effect.
• Smoke from the one forest fire sampled had higher nitrogen, organic nitrogen, and phosphorous concentrations then either the ambient foothill samples or the Tahoe Basin samples. Fireplace wood burning and prescribed fires could be a significant inbasin source of nutrients to the lake and should be regulated accordingly.
• No significant gradients in photochemical pollution levels were found across the Tahoe Basin, implying that local sources are, at most, small contributors to photochemical pollution in the basin. Again, specific efforts to reduce inbasin emissions of photochemical precursors would have only a minor effect at this time.
Supplemental Keywords:ecosystem, ecosystem protection, environmental exposure and risk, geographic area, international cooperation, water, terrestrial ecosystems, aquatic ecosystem, aquatic ecosystem restoration, aquatic ecosystems and estuarine research, biochemistry, ecological effects, ecological indicators, ecological monitoring, ecology and ecosystems, environmental chemistry, restoration, state, water and watershed, watershed, watershed development, watershed land use, watershed management, watershed modeling, watershed restoration, watershed sustainability, agricultural watershed, exploratory research environmental biology, California, CA, Clear Lake, Lake Tahoe, anthropogenic effects, aquatic habitat, biogeochemical cycling, ecological assessment, ecology assessment models, ecosystem monitoring, ecosystem response, ecosystem stress, environmental stress, environmental stress indicators, fish habitat, hydrologic modeling, hydrology, integrated watershed model, lake ecosystems, lakes, land use, nutrient dynamics, nutrient flux, water management options, water quality, wetlands. , Ecosystem Protection/Environmental Exposure & Risk, INTERNATIONAL COOPERATION, Geographic Area, Scientific Discipline, Waste, RFA, Air Quality, Ecological Risk Assessment, Atmospheric Sciences, Fate & Transport, Environmental Chemistry, Forestry, Monitoring/Modeling, Ecology and Ecosystems, Environmental Monitoring, State, California (CA), ozone , airborne organics, fate and transport, forested watersheds, ecological risk, aquifer fate and treatment, field detection, atmospheric deposition, emissions, monitoring, chemical kinetics, analytical models, detection system, emission control, air pollution, atmospheric chemistry, environmental measurement, nitrogen, pesticides, agricultural runoff, modeling, watershed influences, kinetics, agrochemicals
Relevant Websites:
Progress and Final Reports:
1999 Progress Report
2000 Progress Report
Original Abstract
Main Center Abstract and Reports:
R825433 EERC - Center for Ecological Health Research (Cal Davis)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
R825433C002 Sacramento River Watershed
R825433C003 Endocrine Disruption in Fish and Birds
R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
R825433C005 Fish Developmental Toxicity/Recruitment
R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
R825433C009 Modeling Ecosystems Under Combined Stress
R825433C010 Mercury Uptake by Fish
R825433C011 Clear Lake Watershed
R825433C012 The Role of Fishes as Transporters of Mercury
R825433C013 Wetlands Restoration
R825433C014 Wildlife Bioaccumulation and Effects
R825433C015 Microbiology of Mercury Methylation in Sediments
R825433C016 Hg and Fe Biogeochemistry
R825433C017 Water Motions and Material Transport
R825433C018 Economic Impacts of Multiple Stresses
R825433C019 The History of Anthropogenic Effects
R825433C020 Wetland Restoration
R825433C021 Sierra Nevada Watershed Project
R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
R825433C025 Regional Movement of Toxics
R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
R825433C031 Pre-contact Forest Structure
R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
R825433C035 Border Rivers Watershed
R825433C036 Toxicity Studies
R825433C037 Watershed Assessment
R825433C038 Microbiological Processes in Sediments
R825433C039 Analytical and Biomarkers Core
R825433C040 Organic Analysis
R825433C041 Inorganic Analysis
R825433C042 Immunoassay and Serum Markers
R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
R825433C045 Microbial Community Assays
R825433C046 Cumulative and Integrative Biochemical Indicators
R825433C047 Mercury and Iron Biogeochemistry
R825433C048 Transport and Fate Core
R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
R825433C053 Currents in Clear Lake
R825433C054 Data Integration and Decision Support Core
R825433C055 Spatial Patterns and Biodiversity
R825433C056 Modeling Transport in Aquatic Systems
R825433C057 Spatial and Temporal Trends in Water Quality
R825433C058 Time Series Analysis and Modeling Ecological Risk
R825433C059 WWW/Outreach
R825433C060 Economic Effects of Multiple Stresses
R825433C061 Effects of Nutrients on Algal Growth
R825433C062 Nutrient Loading
R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
R825433C064 Chlorinated Hydrocarbons
R825433C065 Sierra Ozone Studies
R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
R825433C067 Terrestrial - Agriculture
R825433C069 Molecular Epidemiology Core
R825433C070 Serum Markers of Environmental Stress
R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
R825433C072 Molecular Monitoring of Microbial Populations
R825433C073 Aquatic - Rivers and Estuaries
R825433C074 Border Rivers - Toxicity Studies