Where Air and Water Meet
Atmospheric Deposition to the Pacific Coast
WORKSHOP REPORT 2000
The aquatic ecosystems on the Pacific coast of North America are impacted by multiple stresses--point source sewage discharges; agricultural runoff of pesticides, herbicides, nutrients, and sediments; deforestation; and pollutants resulting from urbanization. Pollutants from atmospheric deposition also affect the water and surrounding landscape. Atmospheric deposition has been shown to be significant in other areas of the country, but there is limited knowledge of its impact on Pacific Coast aquatic ecosystems or human health. It is important to better understand how deposition to Pacific Coast ecosystems effect the health of both these ecosystems and the people who live near them. To facilitate a discussion about the role of atmospheric deposition on the Pacific Coast and raise interest among scientists and managers, the Ecological Society of America (ESA) hosted a one and a half-day workshop on February 9 and 10, 2000 in Los Angeles, CA. The workshop was supported by the U.S. Environmental Protection Agency?s (EPA) Office of Wetlands, Oceans, and Watersheds, the University of California at Los Angeles (UCLA) Institute of the Environment, the University of California Toxic Substances Research and Teaching Program, and the Southern California Coastal Water Research Project (SCCWRP). It is one of a series of workshops investigating atmospheric inputs to coastal waters held jointly by the EPA and ESA.
The goal of the workshop was to facilitate on-going discussions about the significance of atmospheric deposition to the Pacific coast. This report is intended only to be a summary of the presentations and discussions of the workshop. Presentations included an outline of the state-of-the-knowledge on atmospheric deposition to Pacific Coast ecosystems, updates on atmospheric deposition projects, and technical transfer talks describing how other areas are dealing with the issue. The workshop participants identified knowledge gaps, including those that are priorities. A list of suggested readings on toxic deposition to aquatic systems is contained in Appendix I. The agenda and a list of participants are contained in Appendices II and III.
Summary of Major Points
Status of Pacific Coast Aquatic Ecosystems
The climate, flora, and fauna of the Pacific Coast, from Alaska to Baja, are greatly influenced by the air and ocean currents coming from the west, as well as changes in these currents. Over the last three decades, there have been declines in the abundance and health of marine resources, from plankton to fish to marine mammals and birds. Even common coastal fish populations are declining drastically. The big question is "why?" Possible causes include scarcity of ocean nutrients, increases in contaminant levels, over fishing, altered predator-prey interactions, climatic changes, some combinations of these, or other unidentified causes. So far, there is no simple single answer. It is possible, however, that air deposition is part of the problem.
While levels of PCBs, PAHs, and other toxic substances in marine organisms increased for several decades, studies such as NOAA?s mussel watch are now showing decreasing levels in many of these due to point source reductions. However, there are some areas which still show high levels of contamination of some toxics and the number of fish and shellfish consumption advisories appears to be increasing. Our knowledge of "traditional" sources of contamination in most areas of the Pacific Coast is highly incomplete, and even less is known about atmospheric inputs. In addition to knowing the magnitude of pollutant loads, it is necessary to know the ecological impact of those loads in order to predict effects on Pacific coastal ecosystems.
A Summary of Atmospheric Deposition to the Pacific Coast
Scientific understanding of atmospheric deposition on the Pacific coast is a sparse patchwork of isolated research and monitoring projects. In the Eastern United States, there are well-defined environmental effects and health risks related to atmospheric deposition of toxics (e.g., PCB-contaminated fish in Lake Superior far removed from any sources; mercury-contaminated fish in remote lakes in Maine, etc.). In contrast, few contamination problems in the West, specifically along the Pacific coast, are unambigouously related to atmospheric deposition. Presumably, atmospheric deposition plays some role in contamination of areas such as San Francisco Bay and Puget Sound, but runoff and tributary contamination to these waterbodies is so great that it is not clear how significant is atmospheric deposition. Recent research has begun to demonstrate a possible link between atmospheric deposition and toxic contamination.
Peterson et al. (2000) found that the frequency distribution of mercury in fish and streams in Oregon showed no difference in mercury contamination levels across the state. The presence of this type of pattern is one of the "warning flags" that atmospheric deposition is a source of contamination to an ecosystem. In this case it could be that mercury from long-range transport is affecting the entire state.
Organochlorines, mercury, and other volatile pollutants in air currents condense in cold climates. This means they deposit at high rates in northern climates and at high elevations. This is why lighter persistent organo-pollutants (POPs) are found in relatively high concentrations in remote arctic areas. Evidence of this cold condensation effect includes increasing hydrocarbon concentration with increasing latitude and mercury in high latitude lake sediment fluxes. These pollutants seem to come from regional sources.
Blais et al. (1998) found high levels of contaminants in glacial snow pack in Western British Columbia and the Canadian Rockies and tracked these contaminants into glacial lakes. Similar high rates of pollutant deposition have been seen in the Sierras. For example, snow pack sampling by Landers in 1992 found potentially high concentrations of contaminants. The Sierra snow pack is intercepting contaminants from somewhere, but it is not clear if the sources are local, regional, or intercontinental.
Intuitively, we believe that the rivers draining the Sierras transport contaminants back to the coast through runoff and snowmelt, but there has been no data collected to demonstrate this. A study of sediments and striped bass of San Francisco Bay found that those from the South and Central Bay had higher levels of PCBs than those from the North Bay (Pereira et al. 1994). The rivers that feed these portions of the Bay originate in the Sierras, so atmospheric deposition to the Sierra snowpack could be a source. However, the rivers also drain agricultural, urban, and industrial areas, so atmospheric deposition is not the only source and identifying its impact is difficult.
Atmospheric deposition can run upstream too. While looking at the importance of keystone species to coastal environments, Ewald et al. (1998) found that salmonids bring both nutrients and contaminants from the ocean to the spawning grounds. When the animals die after spawning, these compounds are released into the ecosystem.
This brief tour of atmospheric deposition work on the Pacific coast highlights some of the problems facing research and management communities interested in how significant atmospheric deposition is in these environments. There is no cohesive or coordinated research or monitoring program, and each researcher uses different methodologies. If we want to get a comprehensive view of the entire picture (i.e., what is going on along the entire coast for each of the pollutants of concern), it would be necessary to invest in a standardized design for measuring contaminants.
Projects and Problems
Five current or recent projects investigating atmospheric inputs of toxics to aquatic ecosystems were presented. The presentations included brief descriptions of the research conducted, including the pollutants studied, methods used, potential or suspected sources and impacts, and potential management strategies.
Santa Monica Bay and the Southern
California Coastal Ocean
The Santa Monica Bay and the Southern California Coastal Ocean are impacted by a heavily urbanized watershed (Los Angeles and surrounding communities). Previous studies have shown that atmospheric deposition does impact the Bay, but have not quantified the total load to the Bay or measured its effects. UCLA, the Santa Monica Bay Restoration Project (SMBRP), SCCWRP, and other partners are in the first year of a cooperative three-year project to look at atmospheric deposition to the Santa Monica Bay. The goals of the project include:
- estimating the total annual load of pollutants entering Santa Monica Bay via atmospheric deposition;
- estimating the proportion of the annual atmospheric pollutant load that is contributed during specific meteorological events and conditions (such as Santa Ana winds); and
- describing how atmospheric pollutant loads vary spatially within Santa Monica Bay and among other regions of the Los Angeles air basin.
To answer these questions, the project will directly measure wet deposition of selected pollutants (metals and organics) to the watershed, model dry deposition to the watershed, and model both wet and dry deposition to the Bay itself. It is very difficult to make accurate deposition measurements, particularly dry deposition measurements, over water, primarily because of the difficulty of making estimates of air concentrations over water. The modeled deposition to the Bay will be compared with measurements of the Bay microlayer. The study is using an Air Quality Monitoring Division (AQMD) monitoring study to get a regional pattern of metals deposition. There are also a UCLA station and nine microlayer stations.
Early findings indicate that air appears to be a significant source relative to other sources and dry deposition is more important than wet (Southern California generally doesn?t receive much rain). The study has uncovered some temporal and spatial trends, including two "coastline effects." The first is spatial with higher microlayer values near the coast at all times. The second is temporal and is associated with a change in wind direction in the early morning. At sites nearest the coast, early morning offshore winds cause a peak in contamination levels in the microlayer. There is also a diurnal effect during certain seasons that could be significant. The Santa Ana winds blow offshore from east to west and are associated with a plume of urban air extending far over the water. There is a lot of seasonal and spatial variability in emissions from sources (both in and outside the watershed) and deposition rates across Bay.
Preliminary results have also indicated the importance of the microlayer as both a source and a receptor for pollutant transfer (pollutants are volatilized from the microlayer as well as deposited to it). There may well be a seasonal or weather component to this process as well. The concentration of pollutants in the microlayer also appears to be toxic in laboratory bioassay studies.
In addition to accurately quantifying
the deposition load, the study will attempt to tease out information on
sources of deposition.
What is the Microlayer?
The microlayer is the very thin surface layer of water. It is only 50-500 microns thick. This layer is home to a significant number of microscopic plants and animals that form the basis of coastal food chains. Pollutants, especially hydrophobic ones, concentrate in this layer. Therefore, organisms that live there may be subject to much higher doses of atmospheric pollutants than otherwise expected.
San Francisco Bay Atmospheric
Deposition Pilot Study
Sixty-four local dischargers and the City of San Jose are funding the San Francisco Estuary Institute and others to conduct a study to determine if air deposition is a significant source of pollution to the San Francisco Bay. The Regional Monitoring Program for Trace Substances is investigating general sources, pathways, and loadings, as well as effects of the contaminants. Atmospheric deposition is one piece of the much larger assessment program. The program will compare collected information to relevant benchmarks (regulatory and non-regulatory), look at patterns and trends, and synthesize and distribute information. The goals of the atmospheric deposition component are to:
- estimate seasonal and annual deposition of selected pollutants from the air to the Bay;
- compare results to loadings from other pathways or mechanisms; and
- explore tools for reducing total pollutant loading to the Bay.
The study measures both wet and dry deposition at three monitoring stations (North, Central, and South Bay). Phase 1 will look at trace elements (copper, nickel, mercury, cadmium, and chromium) and Phase 2 will include trace organics (PAHs, PCBs, and dioxins). Preliminary data has been collected for wet deposition of copper, nickel, cadmium, and chromium, for mercury air sampling, and for direct dry deposition of copper, nickel, cadmium, and chromium.
The dry deposition portion of the study was highlighted at the workshop because dry deposition is difficult to quantify and therefore is generally underestimated. The dry deposition study was conducted using surrogate surface plates with a larger surface area and shorter exposure time than generally used in dry deposition monitoring. Preliminary data are available from measurements taken on bi-weekly intervals from September through December, 1999.
Challenges facing the project include:
- funding for the project?the study group wants to measure more pollutants at more sites, but is limited by budget;
- problems with wet deposition measurements (e.g., inconsistent precipitation collection of trace metals vs. mercury samples and pre-charged acidic solutions for mercury samples evaporating at inconsistent rates); and
- problems with mercury air sampling which required the redesign of the mercury sampling trap (e.g., the mercury concentration measured was surprising low and measures in filter traps (particulate) were greater than in gold traps (gaseous)).
Evaluation of the Atmospheric Deposition
of Toxic Contaminants to Puget Sound
In 1990, the Puget Sound Water Quality Action Team conducted a study, funded by EPA through the National Estuary Program, to determine if atmospheric deposition was a significant source of contamination in Puget Sound. The study measured metals and organics and focused on the area of Puget Sound near a high concentration of industries. Aerosol data was collected at six sites and deposition data was collected at five sites over six months. Modeling was conducted to apportion aerosol data to sources and to estimate the spatial distribution of contaminants. The study found that the load from atmospheric deposition to the water column is low compared to direct discharges into the water. However, atmospheric deposition may be significant in particular zones such as the sea-surface microlayer. Deposition of lead and zinc, though small, was important to the total mass loading of these two metals.
Potential ecological impacts of atmospheric deposition of metals and organics to Puget Sound include potential effects on the health and survival of aquatic life in the Sound and potential effects through the food chain on human health. Exposure during development may harm organisms especially if they spend this critical time in the microlayer. The study estimated indirect deposition (how much atmospheric deposition is falling on the land and washing into the Bay), but because of the difficulties involved likely underestimated the amount of indirect deposition and therefore the total atmospheric load.
The study also found that sources of atmospheric deposition vary by season. In the summer, most of the deposition is in the form of larger particles and originates from local sources (earth moving construction, ore off-loading, pulp and paper mills, and smelters). In the winter, the deposition is in the form of finer particles primarily from wood smoke, which is a regional source.
Management strategies identified to reduce atmospheric deposition to Puget Sound include better control of fugitive dust sources, particularly those containing toxics, removal of PAH sludge, and reduction of wood smoke. Although atmospheric deposition was not identified as a significant source of contamination to the water column, all of the management strategies have been implemented because of their effects on air quality.
Atmospheric Deposition of Persistent
Organic Pollutants at High Altitudes in Western Canada
Recent research in the Canadian Rockies and western British Columbia found large amounts of volatile and semi-volatile pollutants in these remote places (Blais et al. 1998). The low temperature and high amount of precipitation (in the form of snow) in these areas results in cold condensation of atmospherically-borne chemicals. This causes mountain and high latitude environments to act as sinks for atmospheric compounds.
In one study, snow samples were collected from high and lower altitudes and the concentration of toxic compounds measured. Higher concentration was correlated with higher altitude for volatile compounds. Possible causes for the presence of large concentrations of contaminants at higher elevation include:
- the grasshopper effect?colder air condenses semi-volatile organic compounds and they are emitted at higher elevations;
- a higher catchment export of contaminants from alpine terrain due to their steepness and thin vegetative cover; and
- glaciers which store contaminants from historical deposition and release them through glacial melting.
In another study, a flux budget of hydrocarbons was calculated for Bow Lake for May-August 1998. Hydrocarbon levels increased in the lake because the inputs were greater than the outputs. The potential sources of hydrocarbons to the lake are direct atmospheric deposition, alpine catchment drainage, meadow catchment drainage, and glacier melt. At the alpine site, there was a large discharge of hydrocarbons with snow melt, but the highest concentration of toxics came from the glacial site. The glacier appears to have been a historical sink for hydrocarbon deposition. Melting of glacial ice and release of pollutants deposited from the atmosphere in earlier decades may be a significant contributor of toxics to aquatic environments. It is likely that this process happens everywhere there are permanent snowpacks and that these pollutants are transported into alpine ecosystems. They may be transported beyond those ecosystems to the coast.
Atmospheric Deposition at Mauna
Evidence of long-range transport of pollution is regularly collected at NOAA?s Mauna Loa Observatory (MLO) in Hawaii. MLO is a prime location for measuring long-range transport because it is located above the inversion layer, where the air is dryer and faster. The Observatory has been collecting data to develop a global picture of CO2 concentration and air movement. Other pollutants are also transported around the globe via atmospheric currents.
Mauna Loa receives an average of 30 dust storms per year. The dust hits MLO approximately five days after leaving Asia. Size- and time- resolved aerosol composition measurements were combined with isentropic backward air-mass trajectories and gas measurements of radon, methane, carbon monoxide, and carbon dioxide to identify potential source regions of anthropogenic aerosols (Perry et al. 1999). The measurements of methane and radon indicate that the air has previously been over land, which can provide further evidence that the dust/pollution events are from emissions occuring in Asia. Three types of long-range transport episodes were identified: (1) anthropogenic aerosols mixed with Asian dust; (2) Asian pollution with relatively small amounts of soil dust; and (3) biomass burning emissions from North America (Perry et al. 1999). Smoke from the 1998 Mexican forest fires was measured at MLO, blown in by strong offshore winds.
In short, it appears that pollutants are easily transported long distances in upper atmospheric currents. This happens more easily and more often than had first been assumed. While much of these pollutants are deposited near the source, significant amounts are also deposited hundreds or thousands of miles from where they were emitted.
NOAA is interested in conducting additional sampling to characterize more accurately what pollutants are being transported from Asia. NOAA also offered their sites as part of cooperative monitoring and assessment efforts with other organizations. NOAA is also looking for a future observatory site on the U.S. West Coast.
Pollutant Sources and Pathways
Local Sources and Pathways
The Santa Monica Bay Restoration Project was used as an example for a discussion of local sources and pathways of atmospheric deposition to coastal waters. The Bay is under multiple stresses including a large coastal population and a variety of point and non-point sources along the coast. The sediments of Santa Monica Bay have a higher concentration of chemicals than those in the surrounding Southern California Bight. There is also a greater enrichment of Bay soils by trace metals. However, it is difficult to tease out the natural fractions of these elements from the man-made.
To address these concerns, SCCWRP is estimating pollutant loads from all sources--point, nonpoint, and atmospheric--and assessing their impacts to the Bay. Mass emissions are a useful tool for managers to help them understand total input, how sources compare, and trends.
Some sources of chemicals and trace metals to U.S. coastal waters are known better than others:
- Waste treatment point sources have been well studied and regulated over the last 30 years, have relatively constant flows and concentrations, and have shown a decreasing trend in suspended solids and metals even with increases in flow.
- Surface runoff is less studied, highly variable in flows and concentrations, and increasingly regulated.
- Atmospheric deposition is not routinely measured for toxics in most areas, the loads to aquatic ecosystems are unknown and there is not much regulatory structure to deal with them.
In determining zinc loadings to the Santa Monica Bay by source, SCCWRP found that 62% were due to atmospheric deposition (calculated using local air concentrations and deposition velocities). To further investigate the loadings from atmospheric deposition, SCCWRP is cooperating with UCLA and SMBRP on an atmospheric deposition study, which also received funding from the Los Angeles County Department of Public Works. The study is measuring the total atmospheric load to the Bay, how it is changing over time, and how it varies spatially (see page 3 for more details on the study results).
One challenge that the collaborative project has highlighted is the difference between airsheds and watersheds. Water resource managers are used to working in watersheds but they are not yet comfortable working with the larger number of agencies and stakeholders in an airshed. Air resource managers are also not used to considering deposition into watersheds far from air emission sources. The process of learning to work together to identify sources of existing problems and solve them in a reasonable manner is another of the challenges in addressing atmospheric deposition.
Long-Range Sources and Pathways
As our understanding of global pollutant transport has grown, long-range transport of pollutants from Asia to North America has become the subject of significant research. In addition, there has been and likely will continue to be increases in coal and other industrial emissions from China and other developing Asian economies.
Air from Asia can be transported to the west coast of the U.S. in as little as five days (Jaffe et al. 1999). The "arrival" region is along approximately 130 degrees longitude (primarily northern California to British Columbia). Pollutant "storms" are easily identifiable because the large dust particles are transported to the U.S. only during discrete meteorological events. The large particle pollutants must be entrained in high air currents in order for them to reach the coast of North America.
Researchers have been able to identify "pollution" events from Asia, but there are also background emissions from Asia that reach the U.S. These are harder to identify. Long-range transport from Asia can be isolated as a pollution source by:
- screening atmospheric data by local wind direction;
- confirming that local winds are representative of standard conditions;
- using short lived tracers found in local sources to identify what portion of the load is not local;
- using back trajectory analysis to identify long-range transport and possible source regions; and
- where possible, taking into account consistent patterns between source emissions and receptors.
The Photochemical Ozone Budget of Eastern North Pacific Atmosphere (PHOBEA) project (Dan Jaffee, University of Washington at Bothell) is using instantaneous measurement techniques at Checka Peak Observatory in the NW corner of the Olympic Penisula. Measurements were taken in the Springs of 1997, ?98, and ?99, and were complemented by 14 research flights in 1999.
Isentropic back trajectories were used to find potential source regions. However, small differences in which path air took at a convergence of airstreams gave different source areas. Spring is likely to be the most important season for these transport events from Asia, but fall is also important in terms of frequency of transport and we are also seeing cases in summer. The percent of the pollutant lost during transport varies by pollutant species. Chemical concentrations can be diluted via deposition to oceans. It is likely that larger particles deposit more locally while smaller particles travel farther. The species of the pollutant is likely to be important in whether it will remain in the atmosphere and be transported from Asia to North America:
- ozone ? evidence of high background rates at 2-3km in air, at levels that may cause vegetation impacts, as well as human impacts (Berntsen et al. 1999; Kotchenruther et al. 2000);
- particulates ? evidence of long-range transport from Asia;
- mercury ? no data;
- persistent organic pollutants ? no data; and
- acids ? no evidence of long-range transport from Asia and may not be an issue as they are highly soluble and probably don?t survive long-range transport across the Pacific.
Future research should focus on integrated
efforts, combining different types of monitoring for a number of contaminants
co-located in space and time. Research is also needed on the cumulative
effects of these pollutants on watersheds and vegetation.
What we know about long-range transport in the Western U.S.
EPA TMDL Pilot Project:
Technology Tools and Management Implications
A TMDL--total maximum daily load--is the amount of pollution a waterbody can receive and still meet water quality standards. TMDLs serve as the second line of defense after point source permits by protecting waterbodies where these permits are not stringent enough to protect the health of the aquatic ecosystem. The TMDL process is relatively straightforward:
- Every two years, each state identifies all the waterbodies not meeting water quality criteria and identifies which pollutants are present in excess amounts. This list is called the 303(d) list.
- For every waterbody (or waterbody segment) listed, the state must develop a TMDL.
- To do so, the state first identifies the acceptable pollutant loading to the waterbody and identifies all the sources of the pollutant.
- The state then allocates pollutant loads among point and nonpoint sources based on ease of pollutant reduction, cost, and other reasons the state may choose. There is no set formula for how to allocate pollutant reductions among sources.
- The state uses federal, state, and local laws to enforce the loadings reductions from the various sources.
Many 303(d) listed waterbodies and TMDLs already mention atmospheric deposition as a source, often because other sources want the responsibility spread between all pollution sources (not just traditional water pollution sources). Listing waterbodies when atmospheric deposition is the primary source of pollution and including air sources in all TMDLs will become mandatory under the new regulation. However, it is easier to identify atmospheric deposition as a pathway than it is to implement reductions in air emissions at particular sources that will improve water quality. This is because the data linking emissions from specific sources to deposition in specific places and the legal experience with reducing emissions from those sources is often lacking. If TMDLs are going to be a tool to improve water quality from all sources, including atmospheric deposition, air and water agencies need to work together more closely.
The EPA is conducting a TMDL Pilot Project to work through the hurdles of including air deposition of mercury in TMDLs. The project will identify technical challenges (specifically, how to link air and water models and what information is needed to develop a TMDL for mercury from air sources) and the legal issues (specifically, what authority states and the federal government have to get reductions from these sources).
The primary data analysis for the project involves connecting air and water models to link atmospheric emissions of mercury to fish contaminated with mercury. In this case, the air and water models are being run simultaneously. The water model generates a dose-response curve where potential mercury inputs (from any source) are translated into fish tissue concentrations. The air deposition model then calculates the actual input to the water model, and the resulting fish contamination data is read off the already-developed dose-response curve. Technical uncertainties and data gaps identified in the pilot include limited mercury speciation data; meteorological variability; uncertainties about the chemistry of mercury in the atmosphere; and the lack of international inventories.
The pilot has also identified a number of questions involving implementation of TMDLs for atmospheric sources of mercury. A report of the pilot study and lessons learned is expected in late 2000.
For more information on the TMDL Pilot Study, contact:
TMDL Pilot Project Coordinator
USEPA Office of Water
| Randy Waite
TMDL Pilot Project Coordinator
USEPA Office of Air and Radiation
Look Down the Road: Expanding Atmospheric Deposition
Monitoring from One Site to a Regional Approach
As atmospheric deposition has been identified as an issue of concern, efforts to monitor it have expanded from single sites to regional network approaches. Examples of these networks include the National Atmospheric Deposition Project?s National Trends Network (NADP NTN), the Mercury Deposition Network (NADP MDN) and the Integrated Atmospheric Deposition Network (IADN).
Reasons for using networks to monitor atmospheric deposition include:
- atmospheric deposition is a significant source of pollution in many areas;
- networks encompass the spatial variability in deposition rates that usually occurs in urban areas and over large regions;
- data collected from several sites is more statistically robust than data from one site;
- networks that operate for several years provide estimates of long-term trends;
- network data provides input to and validation of modeling and research; and
- network data provides indications of important sources and source regions.
The NADP NTN was established to look at acid rain and acid related deposition. The NADP NTN is a national network that is regionally representative (the sites are located in relatively rural areas to avoid proximity to large sources). Uniform sampling procedures and equipment are used and chemical analyses are performed at a single central laboratory. The NADP NTN has a strong field and laboratory quality assurance program and rapid and open data dissemination (http://nadp.sws.uiuc.edu).
Mercury contamination in fish is the prime route of exposure for humans, so the sources of mercury in water are closely monitored. The Mercury Deposition Network (MDN) was established as part of the NADP to measure trends in wet mercury deposition across time and space (http://nadp.sws.uiuc.edu/mdn/). The most active compound of mercury deposition is oxidized mercury which is less volatile and more water soluble than elemental mercury. Therefore, measuring wet deposition is a good way of monitoring mercury in areas where there is significant rainfall. In areas where rainfall is not significant, dry deposition can be an important component of mercury monitoring, one not included in the MDN. The main sources of atmospheric mercury are municipal solid waste and medical waste incineration and coal combustion. Areas with high mercury emissions include the Ohio valley (coal combustion) and major urban areas (incineration).
The Integrated Atmospheric Deposition Network (IADN) is more ambitious in the pollutants it monitors (PCBs, PAHs, organochlorine compounds, and trace metals). It is a joint effort of US & Canadian labs to measure atmopsheric deposition to the Great Lakes region (http://www.epa.gov/glnpo/iadn). During the development of the network, there was significant discussion of whether to characterize the loads from urban areas around the Great Lakes or focus on regional deposition. The decision was made that the network should focus initially on the regional issue and rural sites were selected to avoid the concentrated sources of urban areas. Since then, urban sites have been added to the IADN. For example, the mass balance in a study of Lake Michigan does include measurements from urban sources, including the city of Chicago. In fact, Chicago has been shown to be a large contributor to deposition for many toxic contaminants in the southwest portion of Lake Michigan.
Recent findings from IADN highlight the need to measure deposition rate and water concentration consistently over long periods of time. PCB data was collected at the Sturgeon Point, NY, site and plotted against time to determine trends. When this information was first reviewed, PCB concentrations seemed to be stable or decreasing over time, however recently they have started increasing with no indication as to why. Therefore, some baseline amount of monitoring needs to be continued over longer time periods and should not stop when we think concentrations have stabilized.
A Look Down the Road: Moving From Research to Management
The NY/NJ Harbor National Estuary Program (HEP) is in the process of incorporating atmospheric deposition into its management strategy to clean up the Harbor. In order to do that, HEP began a research program in conjunction with New Jersey Department of Environmental Protection and the Hudson River Foundation to set up a monitoring network. The network was designed with both scientific experts and managers to identify the important components and ensure the data would be sufficient for its intended uses (quantifying the atmospheric load and identifying sources). A large part of the effort is encouraging state air and water programs to discuss their joint problem of atmospheric deposition sources to the Harbor.
In 1997, HEP helped to form the NJ atmospheric deposition network to determine potential air impacts, assess the impacts of nearby sources, identify and quantify out-of-state pollutants, and integrate the NEP efforts with PM2.5 and groundwater monitoring networks. In 1998, HEP held an air deposition workshop and formed technical workgroups to develop workplans to monitor and manage toxics, nutrients, and pathogens. In 1999 two air-water expert panels were formed to determine if sufficient information existed to set regulatory goals and identify data gaps and research needs. The workgroups identified the following assessment strategies: system-wide mass budgets to assess atmospheric contribution; concentration/depositional fields to develop spatial gradients; ozone transport models to evaluate regional and long-range sources; and back-trajectory analyses to evaluate source signature. The research needs/data gaps identified included:
- data quality must be assured and statistical assessment tools employed;
- source assessments and back trajectories need to be performed;
- air-land-water spatial models need to be linked;
- additional pollutants need to be included;
- particle size distributions are unknown;
- meteorology/sea breeze impacts need to be understood; and
- NADP co-locations need to be developed and linked to the HEP monitoring network.
For more information on the NY/NJ Harbor NEP, contact:
NJ Department of Environmental Protection
Bureau of Environmental Assessment
609-633-3866; 609-292-7340 (fax)
| Bob Nyman
NY/NJ Harbor NEP
USEPA Region II
A Look Down the Road: Emerging Issues for the Pacific Coast
The emerging stresses that are likely to have significant impacts on Pacific coast aquatic ecosystems in the next decade include:
- water supply;
- demand for power;
- seafood quality;
- contaminated sludge/biosolvent treatment and disposal;
- "new" pollutants (e.g., endocrine disruptors); and
- spills (pipelines, vessels, tank farms).
Future activities that managers of coastal ecosystems will encounter include monitoring, TMDLs, the Endangered Species Act, and requirements for Essential Fish Habitat.
Researchers and managers will have to work together to tackle emerging challenges such as:
- climate change impacts on the productivity of the coastal ocean;
- understanding multimedia issues (air and water, including ocean, coastal, and freshwater ecosystems);
- ecosystems processes; and
- fate and transport of toxics through air, water, and biota.
There are four essential questions which will need to be asked and answered about coastal ecosystems:
- Is it safe to swim?
- Is it safe to eat the seafood?
- Are fisheries (and other non-fishery commodities) protected?
- Are wildlife and their habitats protected? (Is the environment suitable for organisms to reproduce, etc.?)
Challenges and Priorities
Workshop participants identified
challenges facing researchers and managers investigating the role of atmospheric
deposition of toxics in the health of Pacific Coast aquatic ecosystems.
They also identified corresponding research and monitoring, and management
priority actions that, if completed, will allow managers to identify with
some certainty how atmospheric deposition affects the Pacific Coast and
to point in the direction of likely sources.
Challenges and Priority Actions
Research and Monitoring:
There is an incomplete understanding of the linkages between atmospheric
deposition in the watershed and concentrations in coastal areas through
There is uncertainty about how marine organisms are impacted by atmopsheric
deposition. It is not clear if sensitive species or lifestages are adversely
impacted due to their biological structure or ecological behavior.
There is an incomplete understanding of the effects of deposition on organisms
in the microlayer and the process of pollutant exchange between air and
water through the microlayer.
The impact of atmospherically-deposited nutrients to estuaries and the
Pacific ocean is unknown.
Measurement methods are too inaccurate for many of the purposes they are
used for. Problems include: difficulty of making direct deposition measurements
over water, and several technical difficulties related to measuring dry
deposition, especially of mercury.
Determine how local, regional, and global sources impact each area on the
There is a lack of data on sources and methods for source apportionment.
Develop source profiles for toxic pollutants that are deposited into coastal
watersheds as part of the source identification process.
Address the question of authority/jurisdiction/statutes needed to manage
atmospheric deposition to aquatic systems.
Identify possible intervention points to develop a management strategy
that prevents pollution.
Good science must be in place to support management actions.
It is difficult to include atmospheric deposition in watershed restoration
or protection strategies without knowing how significant it is in the ecosystem.
Enhanced coordination between air and water researchers and managers is
necessary to answer most of the questions raised about atmospheric deposition
and address any current or future atmospheric deposition problems.
Understand what sources contribute to long-range transport and what can
be done to regulate them.
Current funding is not sufficient to do the needed research and monitoring.
Suggestions for Further Reading
Baltensperger, U., Schwikowski, M. Gaggeler, H.W., Jost, D.T., Beer, J. Siegenthaler, U., Wagenbach, D., Hofmann, H.J., and Synal, H.A. (1993) Transfer of atmospheric constituents into an alpine snow field. Atmospheric Environment, 27A(12): 1881-1890.
Berntsen, T.K., Karlsdottir, S. and Jaffe, D.A. (1999) Influence of Asian emissions on the composition of air reaching the Northwestern United States. Geophys. Res. Letts. 26:2171-2174.
Blais, J.M., Schindler, D.W., Muir, D.C.G., Kimpe, L.E., Donald, D.B., and Rosenberg, B. (1998) Accumulation of persistent organochlorine compounds in mountains of western Canada. Nature, 395:585-588.
Datta, S., McConnell, L.L., Baker, J.E., Lenoir, J., and Seiber, J.N. (1998) Evidence for atmospheric transport and deposition of polychlorinated biphenyls to the Lake Tahoe Basin, California-Nevada. Environ. Science Tech., 32:1378-1385.
Eilers, J.M. (1991) Are lakes in the Cascade Mountains receiving high ammonium deposition? Northwest Science, 65(5):238-247.
Eilers, J.M., Bernert, J.A., Dixit, S.S., Gubala, C.P., and Sweets, P.R. (1996) Processes influencing water quality in a subalpine Cascade Mountain lake. Northwest Science, 70(2):59-70.
Eilers, J.M., Sullivan, T.J., and Hurley, K.C. (1990) The most dilute lake in the world?Hydrobiologia,199:1-6.
Ewald, G., Larsson, P., Linge, H., Okla, L., and Szarzi, N. (1998) Biotransport of organic pollutants to an inland Alaska lake by migrating sockeye salmon (Oncorhynchus nerka). Arctic, 51(1):40-47.
Fernandez, P., Vilanova, R.M., and Grimalt, J.O. (1999) Sediment fluxes of polycyclic aromatic hydrocarbons in European high altitude mountain lakes. Environ. Science Tech., 33:3716-3722.
Hargrave, B.T., Barrie, L.A., Bidleman, T.F., and Welch, H.E. (1997) Seasonality in exchange of organochlorides between Arctic air and seawater. Environ. Science Tech., 31:3258-3266.
Jaffe, D.A., Anderson, T., Covert, D., Kotchenruther, R., Trost, B., Danielson, J., Simpson, W., Berntsen, T., Karlsdottir, S., Blake, D., Harris, J., Carmichael, G., and Uno, I. (1999) Transport of Asian air pollution to North America. Geophys. Res. Letts. 26:711-714.
Jassby, A.D., Reuter, J.E., Axler, R.P., Goldman, C.R., and Hackley, S.H. (1994) Atmospheric deposition of nitrogen and phosphorus in the annual nutrient load of Lake Tahoe (California-Nevada). Water Resources Research, 30(7):2207-2216.
Kidd, K.A., Schindler, D.W., Muir, D.C.G., Lockhart, W.L., and Hesslein, R.H. (1995) High concentrations of toxaphene in fishes from a subarctic lake.
Kotchenruther, R., Jaffe, D.A., Beine, H., Anderson, H., Bottenheim, J., Harris, J., Blake, D., Rainer Schmitt, R., (submitted April 2000) Observations of ozone and related species inthe Northeast Pacific during the PHOBEA campaigns: 2. Airborne observations. J. Geophys. Res.
Landers, D.H. (unpublished) Persistent organochlorine compounds in Sierra snow.
Landers, D.H., Gubala, C., Verta, M. Lucotte, M., Johansson, K., Vlasova, T., and Lockhart, W.L. (1998) Using lake sediment mercury flux ratios to evaluate the regional and continental dimensions of mercury deposition in Arctic and Boreal ecosystems. Atmospheric Environment, 32(5):919-928.
Li, Y.F., Bidleman, T.F., Barrie, L.A., and McConnell, L.L. (1998) Global hexachloro-cyclohexane use trends and their impact on the arctic atmospheric environment. Geophysical Research Letters, 25(1):39-41.
Livett, E.A. (1998) Geochemical monitoring of atmospheric heavy metal pollution: theory and applications. In Advances in Ecological Research, Academic Press Inc., London. pp. 65-177.
Muir, D.C.G., Omelchenko, A., Grift, N.P., Savoie, D.A., Lockhart, W.L., Wilkinson, P., and Brunskill, G.J. (1996) Spatial trends and historical deposition of polychlorinated biphenyls in Canadian midlatitude and Arctic lake sediments. Environ. Science Tech., 30:3609-3617.
Pereira, W.E., Hostettler, F.D., Cashman, J.R., and Nishioka, R.S. (1994) Occurrence and distribution of organochloride compounds in sediment and livers of striped bass (Morone saxatilis) from the San Francisco Bay-Delta Estuary. Marine Pollution Bulletin, 28(7):434-441.
Perry, K.D., Cahill, T.A., Schnell, R.C., and Harris, J.M. (1999) Long-range transport of anthropongenic aerosols to the National Oceanic and Atmospheric Administration baseline station at Mauna Loa Observatory, Hawaii. Journal of Geophysical Research, 104(D15):18,521-18,533.
Peterson, S.A., Hughes, R.M., Motter, K., Herlihy, A.T., and Robbins, J. (2000) Level and extent of mercury contamination in Oregon iotic fish. In review.
Pfirman, S.L., Eicken, H., Bauch, D., and Weeks, W.F. (1995) The potential transport of pollutants by Arctic sea ice. The Science of the Total Environment, 159:129-146.
Psenner, R. (1999) Living in a dusty world: airborne dust as a key factor for alpine lakes. Water, Air, and Soil Pollution, 112:217-227.
Puget Sound Estuary Program (1991) Evaluation of the atmospheric deposition of toxic contaminants to Puget Sound. EPA 910/9-91-027, U.S. Environmental Protection Agency.
Simonich, S.L. and Hites, R.A. (1995) Global distribution of persistent organochlorine compounds. Science, 269:1851-1854.
Welch, E.B., Spyridakis, D.E., Easthouse, K.B., and Smayda, T.J. (1992) Response to a smelter closure in Cascade Mountain lakes. Water, Air, and Soil Pollution, 61:325-338.
Wesely, M.L. and B.B. Hicks (2000) A review of the current status of knoweldge on dry deposition. Atmospheric Environment, 34:2261-2282.
This report was written by Lori Hidinger and Tamara Saltman of the Ecological Society of America based on the presentations and discussions at the workshop. We would like to thank all those that contributed to the development and review of this report, specifically Lucia Adams, Los Angeles County Department of Public Works; Mary Barber, Ecological Society of America; Dan Jaffe, University of Washington at Bothell; Dixon Landers, USEPA Office of Research and Development; Deborah Martin, USEPA Office of Water; James Pederson, California Air Resources Board; Keith Stolzenbach, UCLA Institute of the Environment; Clyde Sweet, National Atmospheric Deposition Program; and Guang-yu Wang, Santa Monica Bay Restoration Project. We would also like to thank the U.S. Environmental Protection Agency Office of Wetlands, Oceans, and Watersheds, the UCLA Institute of the Environment, the University of California Toxic Substances Research and Teaching Program, and the Southern California Coastal Water Research Project for supporting this workshop and subsequent report. Finally, we would like to thank the workshop presenters and participants for their time and brainpower.
7:30am - 8:00am
|8:00am - 8:15am||Welcome and Introduction?
Richard Turco, Director, UCLA Institute of the Environment
Marianne Yamaguchi, Director, Santa Monica Bay Restoration Project
Gail Lacy, EPA Office of Air Quality Planning and Standards
Debora Martin, EPA Office of Wetlands, Oceans, and Watersheds
|8:15am - 8:45am||Status of Pacific
Coast Aquatic Ecosystems? Alan Mearns, NOAA
This session will cover impacts (species loss, invasion of non-natives, habitat loss, loss of functions, disruption of interactions, human health, etc.) and stressors (one of which is atmospheric deposition of nutrients and toxics) to Pacific coastal ecosystems to provide context for the workshop. The goal of the workshop is to get a sense of what we know and what we need to know in order to understand how significant atmospheric deposition is to these ecosystems and the people who live near them and how it can be assessed and managed.
|8:45am - 9:15am||Atmospheric Deposition
to Pacific Coastal Waters?Dixon Landers, EPA Office of Research
and Development Western Ecology Division
This session will provide a very broad overview of the status of atmospheric deposition science on the Pacific coast. It will focus on indirect deposition to coastal watersheds, as well as direct deposition to the ocean, and why we are concerned about it.
|9:15am - 12:15pm||Projects and Problems?
Each speaker will provide a brief description of the research in their area, including what pollutants are being studied, how they are being studied, and any information they have about sources, ecological impacts, and management strategies. Each speaker will also identify two challenges they have encountered that the group can help them address.
9:15am - 9:45am Santa Monica Bay - Keith Stolzenbach, UCLA
9:45am - 10:15am San Francisco Bay - Rainer Hoenicke and Pam Tsai, San Francisco Estuary Institute;
Eric Hansen, City of San Jose
10:15am - 10:45am Break
10:45am - 11:15am Puget Sound- Naydene Maykut, Puget Sound Water Quality Action Team
11:15am - 11:45am Canadian Rockies and Artic - Jules Blais, University of Ottawa
11:45am - 12:15pm Mauna Loa - Russ Schnell, NOAA
|12:15pm - 12:30pm||Break|
|12:30pm - 2:15pm||Challenges and
Solutions Working Lunch?
The group will brainstorm resources available for and approaches to the problems identified in previous session.
|2:15pm - 3:15pm||Sources and Pathways?
This session will include discussions of how local and long-range sources may be identified, their pathways, fate in the environment, and available tools for source area identification.
Ken Schiff, Southern California Coastal Water Research Project
Dan Jaffee, University of Washington, Bothell
|3:15pm - 3:30pm||Break|
|3:30pm - 4:15pm||The TMDL Pilot: Technology Tools and Management Implications?Tamara Saltman, USEPA Office of Water|
|4:15pm - 4:45pm||A Look Down the
Road: Expanding from One Site to a Regional Approach?
The Mercury Deposition Network and IADN?Clyde Sweet, National Atmospheric Deposition Project
|4:45pm - 5:15pm||A Look Down the
Road: Moving from Research to Management?
How has New York/New Jersey Harbor NEP begun to approach management of atmospheric deposition??Debra Martin for Robert Naimen, NY/NY Harbor NEP and Tom Belton, NJ Department of Environmental Programs
|5:15pm - 5:45pm||A Look Down the
Road: Emerging Issues on the Pacific Coast?
What are likely to be the biggest air/water issues and concerns in the next decade for the Pacific Coast and how can we prepare for them now??Alan Mearns, NOAA
|5:45pm - 6:00pm||Day One Wrap-Up?|
|6:00pm - 7:30pm||Evening Mixer and Poster Session|
7:30am - 8:00am
|8:00am - 8:30am||Explanation/Organization of Working Session? Debora Martin, EPA Office of Wetlands, Oceans, and Watersheds|
|8:30am - 9:00am||Small Group Work Sessions (what we know/what we need to know)|
|9:00am - 10:15am||Presentation of and Additions to Small Group Results|
|10:15am - 10:30am||Break|
|10:30am - 11:00am||How Can We Fill Our Needs?|
|10:30am - 11:45am||What Should be Done First? How Do We Decide?|
|11:45am - Noon||Next Steps and Closing|
We would like to acknowledge
the support of:
U.S. Environmental Protection Agency Office of Wetlands, Oceans, and Watersheds
UCLA Institute of the Environment
University of California Toxic Substances Research and Teaching Program
Southern California Coastal Water Research Project
Ecological Society of America
1990 M Street, NW, Suite 700
Washington, DC 20036
202-833-8773 x209; 202-833-8775 (fax)
US Environmental Protection Agency
Office of Research and Development
Western Ecology Division
200 SW 35th Street
Corvallis, OR 97333
541-754-4427; 541-754-4716 (fax)
USEPA Coastal Management Branch
401 M Street, S.W.
Washington, DC 20460
202-260-1459; 202-260-9960 (fax)
University of California, Los Angeles
Dept. of Environmental Health Sciences
Los Angeles, CA 90095-1772
310-206-1984; 310-206-3358 (fax)
University of California, Davis
Department of Environmental Science and Policy
Southern California Coastal Water Research Project
7171 Fenwick Lane
Westminster, CA 92683
714-894?2222; 714-894-9699 (fax)
I.H. (Mel) Suffet
Copies of this report are available from: