Grantee Research Project Results

Final Report: Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley

EPA Grant Number: R825433C026
Subproject: this is subproject number 026 , 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: UC Davis Center for Children's Environmental Health and Disease Prevention
Center Director: Van de Water, Judith
Title: Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
Investigators: Anastasio, Cort
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research

Objective:

The objectives of this research project were to: (1) determine how photochemical reactions in fog drops and aerosol particles affect the fate and transport of atmospheric pollutants in the Central Valley; (2) characterize the concentrations and chemistry of atmospheric nitrogen (including organic forms) in the Central Valley and their potential ecological effects; and (3) measure atmospheric nitrogen and phosphorus in the Lake Tahoe Air Basin and determine whether Central Valley air contributes to these nutrient levels.

Summary/Accomplishments (Outputs/Outcomes):

We measured the formation of two reactive oxidants (hydroxyl radical [OH] and singlet molecular oxygen) in a number of Davis fog waters illuminated with simulated sunlight. Our results showed surprisingly low concentrations of hydroxyl radicalin fog drops, indicating that it is not generally a significant sink for the destruction of reactive compounds. Subsequently, we used our oxidant measurements to examine the destruction of amino acids as a case study of the role of these two oxidants in transforming pollutants and nutrients in fog drops. The results from our experiments show that although many of these compounds have very long lifetimes in fog drops (weeks to months), several compounds are degraded on time scales of minutes to hours.

In a related project, we examined the photochemical destruction of pesticides sorbed on dry dust particles from agricultural fields in the Central Valley. Evidence from a few previous studies indicated that pesticides bound to airborne soil particles can be transported long distances, suggesting that these dust-bound residues might have significant effects on air quality, human health, and ecosystem health. We studied the fluxes of gaseous and particle-bound pesticides from agricultural fields during the application and soil incorporation of two herbicides.

Because atmospheric deposition is an important source of nitrogen and phosphorusto the Sierra (including Lake Tahoe), we identified and quantified these atmospheric nutrients over the Central Valley and the Sierra Nevada. We collected biweekly aerosol samples in Davis for 1 year and fog waters for three consecutive winters. In addition, we used an instrumented aircraft to sample atmospheric nitrogen and phosphorus over the Sierra Foothills and in the Lake Tahoe Basin. Our results suggest that the Central Valley can be a source of nitrogen to Lake Tahoe during the summer, when winds typically blow from the valley to the lake.

The following activities were accomplished:

• Our results show that although many organic nitrogen (ON) compounds have very long lifetimes in fog drops (weeks to months), several compounds are degraded on time scales of minutes to hours. Measurements of oxidants in the same samples showed that these values could be used to determine lifetimes of amino acids in fog drops. This indicates that our oxidant measurements can be applied to determine the rates of destruction of pollutants and nutrients in fog drops. Because these fog drops form on aerosol particles, it also suggests that similar chemistry occurs in aqueous aerosol particles.

• Our results showed surprisingly low concentrations of hydroxyl radical in fog drops, indicating that it is not generally a significant sink for the destruction of reactive compounds. This is significant because it suggests that current models of fog water chemistry likely are overestimating the importance of OH as a sink for organic pollutants, and that the lifetimes of these pollutants are underestimated. These findings may prompt investigators and environmental regulatory agencies to reconsider current approaches to pollutant monitoring.

• We found that there are significant amounts of pesticides bound to soil dust coming from agricultural fields. Our initial laboratory results show that these pesticide residues can be degraded by sunlight. The next step in this project will be to evaluate the importance of soil-derived aerosol particles as a means for the long-range transport of pesticides, for example, from the Central Valley to the Sierra Nevada. These findings complement what we know about gaseous pesticides, and will have important implications for agricultural and environmental policymakers.

• We found—for the first time—that ON in fog water and aerosol particles was photochemically converted into more bioavailable inorganic nitrogen species and is a key component in smog (ozone) formation. These results are significant for a number of reasons. First, they indicate that atmospheric reactions increase ON bioavailability and, therefore, increase its ecological impact after deposition. Similar reactions also probably occur after deposition (e.g., in Lake Tahoe). Therefore, investigators must consider inputs of ON on nutrient loading to aquatic and terrestrial ecosystems in the Sierra. Second, the conversion of atmospheric ON into inorganic forms might have important impacts on atmospheric chemistry (e.g., via NOx release), and the properties of atmospheric particles and aqueous drops (e.g., their climatic and health effects). These results will improve models of nitrogen transport and ecological impacts.

• Concentrations of fine particulate nitrogen measured over a 1-year period at a site in the Central Valley indicated that local concentrations peak in the later winter/early spring, and that ON is a significant component (typically ~ 20 percent) of the total nitrogen load. This is significant because ON often is not measured in atmospheric samples. Our results show that this would cause a significant underestimate of the total amount of atmospheric nitrogen, its deposition, and its ecological impacts. These findings will help scientists and policymakers improve estimates of nitrogen concentrations and impacts.

• Aircraft measurements suggest that regional, "out of basin" areas such as the Central Valley can be significant sources of nitrogen pollution to Lake Tahoe during the summer, when winds predominantly blow from the Central Valley to the Sierra. In contrast, phosphorus measurements during summer indicate that air from the Central Valley is unlikely to be a significant source of phosphorus to Lake Tahoe. Measurements of nitrogen and phosphorus in a forest fire plume clearly indicate that forest fires in the Sierra can be significant sources of nitrogen and phosphorus to Lake Tahoe. They also suggest that wood burning within the Tahoe Basin might be a significant “in basin” source of both nitrogen and phosphorus. Because atmospheric deposition contributes significantly to the nutrient burden of Lake Tahoe, these aircraft measurements will help policymakers take more effective action in halting the decline of water clarity in the lake.

• The results from this research have been presented in 18 talks and posters at scientific meetings, two seminars at universities, and at the Lake Tahoe Higher Education and Research Symposium (May 2002). In addition, these results were featured in a short article in the Fall 2002 issue of Outlook (a magazine of the College of Agricultural and Environmental Studies at University of California at Davis), and were part of a College IMPACT Sheet entitled "Cleaning California's Air" (Summer 2003). Finally, the results from this research project were presented in a few classes at University of California–Davis, including the Ecotoxicology Core Course "Chemistry and Deposition of Atmospheric Nitrogen" (September 2002).

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., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Air Quality, Environmental Chemistry, State, Fate & Transport, Monitoring/Modeling, Analytical Chemistry, Forestry, Environmental Monitoring, Atmospheric Sciences, Ecological Risk Assessment, Ecology and Ecosystems, fate and transport, monitoring, food chain, environmental measurement, biomarkers, pesticides, fog water chemistry, kinetics, PCBs, fish consumption, emissions, mercury cycling, modeling, air pollution, detection system, soil dust, watershed influences, emission control, ecological risk, field detection, Lake Tahoe, California (CA), analytical models, atmospheric deposition, bioaccumulation

Relevant Websites:

http://ice.ucdavis.edu/cehr/ Exit

Progress and Final Reports:

Original Abstract

1997

1998

1999 Progress Report

Main Center Abstract and Reports:

R825433    UC Davis Center for Children's Environmental Health and Disease Prevention

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