Grantee Research Project Results
1999 Progress Report: Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
EPA Grant Number: R825433C026Subproject: 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
Project Period Covered by this Report: October 1, 1998 through September 30, 1999
RFA: Exploratory Environmental Research Centers (1992) RFA Text | Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research
Objective:
To determine how photochemical reactions in fog drops and aerosol particles affect the fate and transport of atmospheric pollutants in the Central Valley.
Progress Summary:
1. Photochemical reactions of organic nitrogen in fog waters. Heterogeneous photochemical reactions can be significant sinks for many pollutants either through the direct photochemical destruction of a compound that absorbs sunlight, or through indirect oxidation in which sunlight produces an oxidant species (such as hydroxyl radical) which in turn destroys the pollutant. Our photochemical studies to date have focused on reactions of organic nitrogen compounds in fog waters collected in Davis during the past two winters. The reactions that occur in these fog drops are expected to also occur in aqueous aerosol particles during the fall, winter and spring. We have focused on the reactions of organic nitrogen (ON) compounds because there are significant amounts of ON in the troposphere, it represents a significant fraction of the total nitrogen deposited to Lake Tahoe (and, undoubtedly, most of the Sierra-Nevada range), and because extremely little is known of its atmospheric chemistry.
Our photochemical experiments have demonstrated that several organic nitrogen species - including some amino acids and heterocyclic nitrogen compounds - are rapidly destroyed in sunlight-illuminated fog drops, while a number of other ON species are relatively unaffected. These results are significant for a number of reasons. First, they suggest that atmospheric reactions of organic nitrogen may increase its bioavailability and therefore its biological impact after deposition. Second, the fact that a number of amino acids and alkyl amines were not appreciably destroyed during illumination indicates that these compounds may be useful tracers for organic nitrogen deposited in the Sierras. Third, these photodestruction reactions suggest that the oxidation of organic nitrogen may be a source of inorganic nitrogen (e.g., nitrate and ammonium) in the atmosphere. To follow up on this third idea, we have carried out several experiments which have shown that significant amounts of ammonia can be formed during the simulated sunlight illumination of fog waters.
2. Photoformation of hydroxyl radical and singlet molecular oxygen in fog waters. In order to understand the mechanisms for the photodestruction of organic nitrogen discussed above, and to be able to predict rates of destruction of other atmospheric constituents, we have characterized the photoformation of two important oxidants - hydroxyl radical (OH) and singlet molecular oxygen (1O2*) - in the illuminated fog waters. For each oxidant we have characterized the formation rate and steady state concentrations in several fog waters collected over a two year period.
Measured steady state concentrations for OH and 1O2* ranged from (3 - 7) × 10-16 M and (1 - 6) × 10-13 M, respectively. These results are somewhat surprising for several reasons. First, the hydroxyl radical concentrations are quite low, indicating that it is not a significant sink for the destruction of reactive compounds (i.e., those compounds which are destroyed rapidly, such as the ON species described above). This is significant because it suggests that current models of fog water chemistry are likely overestimating the importance of OH as a sink for organic compounds. Second, the concentrations of 1O2* indicate that it can be an important sink for a number of compounds, including some organic nitrogen compounds, polycyclic aromatic hydrocarbons (PAH) and phenols. Third, the narrow concentration ranges for both oxidants indicates that OH and 1O2* concentrations in drops can be estimated fairly easily, e.g., in computer models which consider the fate of atmospheric pollutants.
3. Speciation and quantification of atmospheric nitrogen. Because atmospheric deposition has likely been an important source of nitrogen to the Sierras (as seen for Lake Tahoe) we have been working to identify and quantify the atmospheric nitrogen compounds over the Central Valley and Sierras. As one component of this work we have collected biweekly aerosol samples in Davis for the past year. We have analyzed these samples for ammonia, nitrate, nitrite and amino acids and are currently working to determine concentrations of total organic nitrogen. Our data indicate that ammonia concentrations are strongly correlated with (and much higher than) concentrations of amino acids and that both concentrations are highest in the spring. Furthermore, we have found that the amino acids which were most quickly destroyed in our photochemical experiments described above were not found in any of the aerosol samples.
In addition to this ground-based sampling of particles, in conjunction with John Carroll and Alan Dixon we recently started to collect nitrogenous gases and particles from aircraft flights over the Sacramento area and Sierra foothills. Our hope with these flights is to be able to characterize the emission and transport of nitrogen over the Central Valley and Sierras. Although preliminary, our initial results indicate that there are significant concentrations of both particulate organic nitrogen (including amino acids) and gaseous inorganic nitrogen (primarily ammonia) in these regions.
Future Activities:
In terms of the speciation and quantification of atmospheric nitrogen, we should finish our analyses of the Davis aerosol particles within the next few months. This annual record, in conjunction with future aircraft sampling, should give us some sense of the relative importance of organic and inorganic nitrogen in atmospheric particles in the Central Valley and may yield a rough source profile for Central Valley atmospheric nitrogen. This data, along with additional aircraft flights, may allow us to estimate the significance of the transport of atmospheric nitrogen from the Central Valley as a source of nitrogen deposition to Lake Tahoe and the Sierras.
In conjunction with Britt Holmén (Crocker Nuclear Laboratory) and Tom Young (Civil and Environmental Engineering), this fall we will also begin to study pesticides on soil dust generated in the Central Valley through a grant from the USDA. The three major goals of this project are to: determine the flux of dust-bound pesticides from Central Valley fields; characterize the atmospheric lifetime of the pesticides, and evaluate the importance of soil-derived aerosol particles as a means for the long-range transport of pesticides (e.g., to the Sierra-Nevadas).
Supplemental Keywords:
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, bioaccumulationProgress and Final Reports:
Original AbstractMain 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
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.