The Georgia Basin-Puget Sound Airshed Characterization Report 2014: chapter 6
6. Air Quality Monitoring
Roxanne Vingarzan, Sarah Hanna and Rita So (Environment Canada)
The previous chapter identified the primary emission sources that are responsible for the airborne chemicals found in the Georgia Basin/Puget Sound airshed. The way these emissions are transported, transformed, dispersed and deposited, determines the ambient air quality.
Ambient air quality and meteorological data are routinely collected at a number of sites in the airshed. Many of these sites form part of the monitoring networks that support air quality programs administered by government agencies. There are several air quality networks in the airshed, each with associated air quality programs and specific measurement and operational procedures to meet agency requirements.
The three main ambient air quality indicators tracked by these networks are gaseous pollutant concentrations, particles (and constituents), and the surface deposition of contaminants. Meteorological data including, but not limited to, wind speed and direction, air temperature, relative humidity, and barometric pressure are also collected via these networks. This chapter will focus on describing the established air quality monitoring networks in the Georgia Basin/Puget Sound airshed. Measurements related to ozone and particulate matter are discussed in Chapter 7 and Chapter 8, respectively. Chapter 12 presents measurements and impacts of pollutant deposition.
6.1 Air Quality Monitoring in the Airshed
Air quality monitoring networks provide most of the air quality measurements for the airshed on both sides of the border. Air pollutant concentrations are measured, quality controlled and assured, then archived using comparable procedures and methodologies. The measurements provide hourly or 24 hourly concentrations of the criteria air contaminants; preliminary data are reported in near real-time, unless laboratory analysis is needed. The near real-time technology provides a detailed and timely assessment of air quality concentrations and gives agencies the ability to alert the public to air quality problems.
In British Columbia, air quality is measured by the National Air Pollution Surveillance Network (NAPS), the Canadian Air and Precipitation Monitoring Network (CAPMoN), the BC Ministry of the Environment (BC MOE) and the WISE Air Quality Monitoring Network (LFVAQN). Air quality monitoring in Washington State is carried out by the Washington State Monitoring Network (WSMN), the National Atmospheric Deposition Program (NADP), the Chemical Speciation Network (CSN), the Clean Air Status and Trends Network (CASTNET) and the Interagency Monitoring of Protected Visual Environments (IMPROVE) networks. Other agencies such as the U.S. Department of Interior (National Park Services) operate additional monitoring sites to meet the requirements of their own ambient monitoring programs. The data used to analyse air quality in this report are largely drawn from Environment Canada’s national NAPS and CAPMoN archives and the U.S. Environmental Protection Agency national air quality databases, which include the Air Quality System (AQS), CASNET, IMPROVE, NADP, and the Visibility Information Exchange Web System (VIEWS).These data were chosen to ensure the best possible quality, as well as the highest level of comparability between data sets. The measurement sites used in both jurisdictions are shown in Figure 6.1. Note that a majority of the selected sites are located in the more populous regions of the airshed, and the reader is advised not to interpret the results in this report as being characteristic of the entire airshed.
Figure 6.1. Location of air quality monitoring stations in the Georgia Basin-Puget Sound Airshed.
*The Saturna Island site is a co-located site which is part of the CAPMoN and NADP/MTN network.
**There are four co-located air quality monitoring sites in the Washington State, which include: Marysville (WSMN and CSN), Beacon Hill (WSMN, CSN, IMPROVE), Tacoma South L Street (WSMN and CSN) and Mt. Rainier Tahoma Woods (NADP/NTN, CASTNET, IMPROVE).
Description of Figure 6.1
Figure 6.1 is a relief map of southwestern British Columbia and northwestern Washington State showing the boundary of the Georgia Basin-Puget Sound airshed and the location of the air quality monitoring stations contained within it.
In Canada there are the following stations. There are three stations in the BC MOE network located at Courtney, Duncan, and Victoria BC. There are three stations belonging to LFVAQN located at Abbotsford, at the Point Roberts, and at Indian Arm. There are thirteen stations run jointly by NAPS and BC MOE which are located at Campbell River, the south tip of Quadra Island, Powell River, Whistler, Squamish, Langdale, north and south of Nanaimo, Crofton, Duncan, Saanich, Victoria, and Sooke. There are twenty-eight stations belonging jointly to NAPS and LFVAQN all contained within the lower Fraser Valley. These are located at Vancouver-Downtown, Vancouver-Kitsilano, Burnaby-Kensington Park, N. Vancouver-Second Narrows, Port Moody, Chilliwack, North Delta, Burnaby Mountain, Surrey East, Richmond South, Burnaby South, Pitt Meadows, Burnaby-Burmount, Burnaby-Capitol Hill, Burnaby North, N. Vancouver-Mahon Park, Langley, Hope Airport, Maple Ridge, Richmond-Airport, Coquitlam, Abbotsford-Mill Lake, Horseshoe Bay, Alex Fraser Bridge, Annacis Island, Tsawwassen, Abbotsford Airport, and White Rock. There is also a station on Saturna Island that is a co-located site which is part of the CAPMoN and NADP/MTN network.
In the US there are the following stations. In the IMPROVE network there are three stations located at Snoqualamie Pass, North Cascades, and Olympic. In the NADP/MDN network there is one station in Seattle. In the NADP/NTN network there are sites at Alder Lake just west of Mt Ranier, and in just south of Baker Lake. In the NPS network there is a station in the Olympic Mountains. In the WSMN network there are twenty-eight stations at Cheeka Peak, Neah Bay, Port Angeles, Port Townsend, Anacortes, Bellingham, Custer-Loomis, Mt Vernon, Darrington, Marysville, Shelton-W Franklin, Lacey-College St, Yelm-Northern Pacifc, Mt Rainier, Puyallup-128th St, Enumclaw, Puyallup-Puyallup Tribe, Tacoma, Kent, North Bend, Issaquah-Lake Sammamish, Bellevue, Lake Forest Park-Town Center, Edmonds, Bremerton, and three stations in Seattle. There are also four co-located air quality monitoring sites in the Washington State, which include: Marysville (WSMN and CSN), Beacon Hill (WSMN, CSN, IMPROVE), Tacoma South L Street (WSMN and CSN), and Mt. Rainier Tahoma Woods (NADP/NTN, CASTNET, IMPROVE).
6.1.1 Georgia Basin Air Quality Monitoring Networks
The National Air Pollution Surveillance (NAPS) Program is a joint federal, provincial, territorial and municipal initiative to coordinate the collection of air quality data into a unified national data base (Dann et al., 2011). The British Columbia Ministry of the Environment, Metro Vancouver and the Fraser Valley Regional District operate additional monitoring stations to meet the requirements of their own ambient monitoring programs. For instance, the WISE Air Quality Monitoring Network (LFVAQN) is operated by Metro Vancouver and consists of air quality monitoring stations located in the Metro Vancouver and Fraser Valley Regional Districts (FVRD). Air Quality and weather data from most of the stations are collected automatically on a continuous basis, transmitted to Metro Vancouver’s Head Office, and stored in an electronic database, which is also archived by the national NAPS network (Metro Vancouver, 2011). The measurements are reported in near real-time on an hourly basis, unless laboratory analysis is needed. The data are used to communicate air pollutant information to the public, through reports and air quality health index (AQHI) values, the latter issued by Environment Canada. In addition, local air quality agencies perform special-purpose monitoring studies, either independently or through inter-agency collaboration.
The Canadian Air and Precipitation Monitoring Network (CAPMoN) is operated by the Air Quality Research Division of the Science and Technology Branch of Environment Canada. The objectives of CAPMoN differ from those of NAPS in that CAPMoN measurements provide data for research into: (1) regional-scale spatial and temporal variations of air pollutants and deposition, (2) long range transport of air pollutants (including transboundary transport), and (3) atmospheric processes, and chemical transport model evaluation. In contrast to most (but not all) NAPS sites, which are generally located in urban, suburban and industrial areas, CAPMoN sites are located in rural and remote areas (Dann et al., 2011). There is currently a single CAPMoN site located in the Georgia Basin airshed, at Saturna Island.
Four types of measurements are made by CAPMoN, namely: the chemical composition of precipitation (major ions and cations) (mostly 24 hour integrated sample collected daily, with the exception of mercury), the chemical composition of atmospheric particles (both acidic and basic), particle mass (PM2.5 and PM10) (24 hour integrated samples, on a 1 in 3 days sampling schedule), and the concentration of selected gases including O3, SO2, nitric acid (HNO3), NO/NO2/NOy, peroxyacetyl nitrate (PAN), mercury (Hg) and ammonia (NH3) (continuous hourly average). It should be noted that mercury in precipitation is collected based on a 7 day integrated sample started at 08:00 local standard time every Tuesday. CAPMoN measurement methods include both size-selective and non-size-selective filter methods for particle composition and mass, specialized denuders, impregnated filters, continuous monitors for gases, and wet-only deposition collectors for precipitation chemistry (Dann et al., 2011).
6.1.2 Puget Sound Air Quality Monitoring Networks
Ambient air quality in the Puget Sound airshed is primarily monitored by the Washington State Monitoring Network (WSMN). The WSMN is composed of State and Local Air Monitoring Stations (SLAMS) and Special Purpose Monitoring Stations (SPMS). Data collected from these stations are reported hourly in near real time, unless laboratory analysis is required, and are archived in the U.S. Environmental Protection Agency Air Quality System (AQS). SLAMS is a network of monitoring stations whose size and distribution is largely determined by the needs of state and local air pollution control agencies, either to follow federal monitoring guidelines, based on U.S. National Ambient Air Quality Standards (NAAQS), or to meet their respective State Implementation Plan (SIP) requirements. Some contaminants and locations not serviced by the basic networks are monitored by supplementary measurement sites, called the Special Purpose Monitoring Stations (SPMS). These temporary and modifiable stations are employed by state and local agencies to supplement the fixed monitoring networks and address changing needs and priorities. The archived data from SPMS meet all quality assurance and methodology requirements for SLAMS monitoring. Additional ambient air quality monitoring sites are operated by the U.S. Department of Interior (National Park Services) to provide air quality information for the two national parks, Olympic and Mt. Rainier, in the Puget Sound airshed. These data are also archived in the U.S. EPA AQS database.
The assessment of deposition processes in Washington State is conducted through the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). The network is a cooperative effort between many different groups, including the State Agricultural Experiment Stations, U.S. Geological Survey, U.S. Department of Agriculture, and numerous other governmental and private entities. The purpose of the network is to collect data on the chemistry of precipitation for monitoring of geographical and temporal long-term trends. The precipitation at each station is collected weekly and then analyzed for pH (acidity), sulphate, nitrate, ammonium, chloride, and base cations (such as calcium, magnesium, potassium and sodium). In addition to the NTN, the NADP has a Mercury Deposition Network (NADP/MDN) which provides a long term record of total mercury (Hg) concentration and deposition in precipitation in the U.S. and Canada. All MDN sites follow standard procedures and have uniform precipitation chemistry collectors and gages. Weekly precipitation samples are sent to the Mercury Analytical Laboratory (HAL) at Frontier Global sciences, Inc. to analyze for total mercury. There are currently two NADP/MDN sites (Saturna Island and Seattle-NOAA) located in Georgia Basin/ Puget Sound airshed.
The assessment of dry deposition is measured through the Clean Air Status Trends Network (CASTNET). CASTNET is considered the nation’s primary source for atmospheric data to estimate dry acidic deposition and to provide data on rural ozone levels. Dry deposition data are collected and analyzed on a weekly basis, where ozone data are monitored continuously and are averaged and reported hourly. Currently, there is a single CASTNET monitoring station, located at Mt. Rainier Tahoma Woods, in the Washington State. CASTNET complements the NADP/NTN network; together, these two long-term monitoring programs provide the necessary data to estimate temporal and spatial trends in total atmospheric deposition.
The chemical speciation of particulate matter in both urban and rural areas is monitored by the Chemical Speciation Network (CSN) and the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, respectively. The CSN (previously the Speciation Trend Network) was implemented in support of the PM2.5 NAAQS. The U.S. EPA established the CSN network to provide nationally consistent speciated PM2.5data for the assessment of trends at representative sites in urban and suburban areas across the country. The IMPROVE monitoring program was established to aid the creation of U.S. federal and state implementation plans (SIPS) for the protection of visibility in Class I areas. As defined in the Clean Air Act, Class I areas are those that were in existence as of August 7, 1977 and include the following: national parks over 6,000 acres, national wilderness areas and national memorial parks over 5,000 acres, and international parks. The IMPROVE monitoring program measures bulk PM2.5 mass, coarse mass (difference between PM10 and PM2.5), and the chemical components of PM2.5 such as sulphate, nitrate, OC, EC, soil elements, and other trace elements. This network of sites measures ambient air quality to establish current visibility and aerosol conditions in mandatory Class I areas, to identify chemical species and emission sources responsible for existing human-made visibility impairment, to document long-term trends for assessing progress towards the national visibility goal, and to monitor regional haze in all visibility-protected federal Class I areas, wherever practical. The Puget Sound airshed has four IMPROVE samplers in Class I areas, as well as a fifth sampler installed at the Beacon Hill site in Seattle. The sampling frequency for both CSN and IMPROVE vary from 24-hour samples every day to once in three or six days.
6.1.3 Measurements of Particulate Matter
Debate over the most appropriate way to measure airborne particles continues. The values used in this report are taken from the Canadian and American national air quality data inventories. These archives also include information on instrumentation and the quality control and quality assurance methods used to obtain the data. For the most part, the data acquired and reported here are compatible between the two jurisdictions.
PM Measurements in the Georgia Basin (adapted from Dann et al., 2011)
In Canada, the manual, 24-hour, filter-based, gravimetric method (Method No.: 8.06/1.0/M) has been adopted as the NAPS Reference Method (RM) for PM2.5 measurements (Dann et al., 2011). Interim data quality objectives (DQOs) have also been established for comparison of continuous PM2.5 instruments with the reference method monitors. The samplers have specially designed inlet “heads” that allow a certain percentage of particles with different diameters to be measured. The sample size or fraction is defined by the 50 per cent cut-point, which is the particle size at which the sampler will collect 50 per cent of the sample, rejecting the other 50 per cent. Therefore, a PM2.5 sampler will retain 50 per cent of particles with a 2.5 μm diameter. Smaller particles will be collected, with efficiencies rapidly rising towards 100 per cent.
Speciation sampling sites are equipped with R&P Partisol-Plus 2025-D sequential dichotomous particulate samplers along with R&P Partisol Model 2300 Speciation samplers. These units share common software and data storage systems. The speciation sampler uses Harvard designed Chemcomb® cartridges, which employ honeycomb glass denuders and filter packs with Teflon and Nylon media (Dann et al., 2011).
The samplers are operated once every three days, and samples are collected over 24 hours. One fine and one coarse filter sample are collected on the dichotomous sampler and three Chemcomb® cartridge samples are collected with the speciation sampler. The Chemcomb® cartridges are shipped to the field completely assembled and sealed and require only mounting and leak-checking. A complete description of analytical protocols can be found in Environment Canada (2004). Organic carbon (OC) and elemental carbon (EC) are determined on quartz filters using a DRI Model 2001 thermal/dual-optical carbon analyzer (Atmoslytic Inc., Calabasas CA) and the IMPROVE (Interagency Monitoring of Protected Visual Environments) analysis protocol. All collected samples are analysed in Ottawa (Dann et al., 2011). There are two speciation sampling sites located in the Georgia Basin, at Burnaby South and Abbotsford Airport.
Real-time particle monitoring began in the NAPS network in 1995, and the number of instruments grew rapidly with over 185 instruments reporting to the network in 2006; approximately 50 of those instruments are located in the Georgia Basin. The majority of the instruments are THERMO Tapered Element Oscillating Microbalance (TEOM) instruments that measure and report hourly values of PM2.5 mass. Beginning in 2002 many TEOM instruments in the NAPS PM2.5 network were fitted with a sample equilibration system (SES). Note that only the TEOM instruments in the Metro Vancouver network were fitted with SES in the Georgia Basin. The SES incorporates a special low-particle-loss Nafion dryer allowing for conditioning of the PM sample stream to a lower humidity and temperature level (Dann et al., 2011). Unless indicated otherwise, all PM2.5 mass data in this chapter are from TEOM-SES instruments operated at 30°C or TEOMs operating at 40°C.
The addition of real-time PM monitoring to the NAPS network has greatly increased the spatial and temporal resolution of the network. However, as with all methods for measuring the mass of particles or aerosols suspended in air, there are uncertainties with the TEOM measurements associated with the loss of semi-volatile chemical constituents. Due to the heterogeneous physical and chemical makeup of PM2.5, no suitable reference standard exists for calibrating PM2.5 instruments. Therefore, PM2.5can only be defined operationally according to the sampling and mass determination method utilized. The U.S. EPA has defined a Federal Reference Method (FRM) for sampling PM2.5, which includes a combination of design and performance based criteria for both the sampler and subsequent laboratory treatment of the sample filter. The calibration of PMsamplers for accuracy is estimated by comparison with the designated “reference” method instrument. Performance specification limits are used to control the overall PM sampling accuracy (Dann et al., 2011).
At a number of locations in Canada, TEOMs, BAMs and TEOM-FDMS units (along with a number of other commercially available units) have been co-located with reference method filter-based samplers, and numerous comparisons of continuous and manual PM2.5 measurement methods have been conducted. Preliminary data confirm the results of similar studies in Europe, the USA and western Canada, namely, that TEOM mass measurements in the cold season are generally lower than mass measured by the manual gravimetric methods (NAPS reference method) due largely to the volatilization of semi-volatile compounds from the TEOMs (Allen et al., 1997; Environment Canada, 2004, Dann et al., 2006). This discrepancy between the TEOMs and the reference method in the cold season is quite consistent across Canada. Agreement between the TEOM and filter-based methods during the warm season is generally very good (Environment Canada, 2004).
PM Measurements in the Puget Sound (adapted from WA DOE (2000a and 2000b)
In Washington State, a 24-hour, filter-based federal reference method for PM2.5measurements is also used (WA DOE 2000a). A Partisol®-Plus Model 2025 Sequential Air Sampler draws a known volume of ambient air at a constant flow rate through a size-selective inlet followed by a WINS Impactor (particle size separator). Particles in the PM2.5 size range are then collected on a Teflon® filter during a specified 24-hour sampling period. Each sample filter is weighed before and after sampling to determine the net weight (mass) gain of the collected PM2.5 sample. This mass concentration is reported as micrograms per cubic meter at ambient conditions. The reference method for PM2.5 sampling is given in the Code of Federal Regulations (40 CFR 50, Appendix L) (WA DOE, 2000a). Three FRM samplers are currently operated within the Puget Sound area, at Marysville, Tacoma (both daily samples) and Seattle-Beacon Hill (operated once every three days).
TEOMS have been used by the Washington State Department of Ecology Air Quality Program, Puget Sound Clean Air Agency and the Spokane Regional Clean Air Agency at some sites. The R&P 1400a TEOM, configured to sample PM2.5 and generate concentrations in actual conditions, is sited with a Federal Reference Method (FRM) PM2.5 sampler. The TEOM provides continuous data that will be used to supplement FRM data to determine diurnal cycles, identify the need to increase FRM sampling frequency, evaluate real-time data to issue alerts or implement control strategies, and provide data when the FRM sampler is not sampling. The first step of TEOM operation is particle separation, which occurs by drawing a controlled volume of air (16.67 L/min) through a cyclone inlet. The sampler cyclone head removes particles greater than 2.5 mm and allows 2.5 mm in diameter and smaller particles to be collected on a Teflon®-coated glass fiber filter surface. To minimize a bias caused by atmospheric moisture, the sample stream entering the TEOM sensor unit is heated to minimize water collection on the sample filter. As the air is drawn into the TEOM, the sample stream (main flow) is heated at the base of the air inlet. The temperature of the upper part of the mass transducer, the rest of the mass transducer, and the temperature inside the sensor unit are all controlled at specific temperature set points (WA DOE, 2000b).
Since the R&P 1400a TEOMs do not correct for the volatilization of PM2.5 mass off the microbalance they have often been found biased low compared to FRMs. Several air agencies in Washington have transitioned away from these TEOMs and have replaced them with the Federal Equivalency Method (FEM) TEOMs, which include a Filter Dynamics Measurement System (FDMS) module. The FDMS module compensates for volatilization of aerosol mass by switching the flow to a purged, reference air stream every 6 minutes. The mass lost off the microbalance during these 6 minutes is then programmatically added back in (ThermoFisher Scientific, 2009). No non-FEM TEOMs (R&P 1400a) operate within the Puget Sound area as of 2011.
Light scattering nephelometers are also widely deployed throughout the state. These measure light scattering of particles and utilize a correlation with a FRM to convert to PM2.5. The correlations are pre-determined, based on co-located data obtained in an airshed with similar aerosol characteristics (WA DOE, 2008).
6.2 Chapter Summary
Air quality and meteorological data are collected routinely throughout the Georgia Basin/Puget Sound airshed by various air quality monitoring networks. The ambient air quality indicators tracked by these networks include gaseous pollutant concentrations, particles (and constituents), and the surface deposition of contaminants. Meteorological data including, but not limited to, wind speed and direction, air temperature, relative humidity, and barometric pressure are also collected via these networks.
In British Columbia, air quality is measured by the National Air Pollution Surveillance Network (NAPS), the Canadian Air and Precipitation Monitoring Network (CAPMoN), the BC Ministry of the Environment (BC MOE) and the WISE Air Quality Network (LFVAQN). In Washington State, air quality is monitored by various major networks which include: the Washington State Monitoring Network (WSMN), the National Atmospheric Deposition Program (NADP), the Clean Air Status and Trends Network (CASTNET), the Chemical Speciation Network (CSN) and the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. Air pollutant concentrations are measured, quality controlled and assured, and archived using comparable procedures and methodologies. Depending on the type of measurements and the network protocol, the sampling frequency can vary, ranging from hourly, once in three or six days, weekly, or can be “event-based”.
Methodology and instrumentation employed in Canada and the U.S. for measuring fine particulate matter (PM2.5) are generally similar, but some differences exist. For the most part, the PM2.5 data presented in this report are compatible between the two jurisdictions, despite some differences in methodology and instrumentation.
Allen, G., Sioutas, C., Koutrakis, P., Reiss, R. Lurmann, F., Roberts, P., 1997. Evaluation of the TEOM method for measurement of ambient particulate mass in urban areas, Journal of the Air and Waste Management Association 47: 682-689.
Dann, T., White, L., Biron, A., 2006. Performance of Continuous PM2.5 Monitors at a Monitoring Site in Ottawa, Canada. U.S. Environmental Protection Agency National Air Monitoring Conference, November 2006.
Dann, T., Vingarzan, R., Chan, E., Vet, B., Brook, J., Martinelango, K., Shaw, M., Dabek, E., Wang, D., Herod, D., Mignacca, E., Anlauf, K., Graham, M., O’Brien, J., 2011. Chapter 3: Ambient Measurements and Observations. In: Canadian Smog Science Assessment. Volume 1. Atmospheric Science and Environmental Effects. Environment Canada and Health Canada.(Executive summary) (Full report available upon request)
Environment Canada, Science and Technology Branch, 4905 Dufferin St, Downsview, Ontario, M3H 5T4
Environment Canada, 2004. Performance of Continuous PM2.5 Monitors at Canadian Monitoring Locations. NAPS Managers Technical Working Group on PM Measurement Technology, November 2004.
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