In order to improve its effectiveness in attaining health-based state and federal clean air standards, the Bay Area Air Quality Management District (Air District) initiates or participates in a wide range of programs. Three important ones will be underway this summer—an expanded Spare the Air program, a study of ozone increases on weekends, and a major study of ozone in Central California.
Spare the Air Program
The Air District's Spare the Air Program promotes voluntary curtailment of air-polluting activities on days when the ozone standard is likely to be exceeded. Aimed primarily at people who drive to work, it also focuses on the use of some consumer products and gasoline-powered equipment.
Preparation for Spare the Air 2000 began with the Spring 2000 Lawnmower Buyback Campaign. Gas-powered mowers could be exchanged for a $150 credit toward purchase of a rechargeable battery-powered, mulching electric mower, with a final cost of $219 plus tax. Campaigns were held in Contra Costa, Napa, Solano, and Sonoma Counties and in Palo Alto and San Jose. Supported by a consortium of funders, the exchanges increase public awareness, reduce waste by promoting mulching, shift to a cleaner energy source, and improve air quality.
During the summer smog season, the Spare the Air Program alerts people—through their employers, by e-mail, by telephone, by radio and television spots, and by other means—the day before when air pollution levels are expected to be high. On these days, people are urged to forego air-polluting activities.
With funds from a Congestion Management Air Quality grant from the Metropolitan Transportation Commission, the Spare the Air Program will continue to expand its advertising campaign. The employer program will include recruiting more participants, expanding the e-mail program, developing workshops for employers, improving "how-to" materials, and incentives. Additional cities and counties will be asked to join in Spare the Air outreach to their residents. Partnerships with transit agencies and special events promoters to encourage transit use will be increased.
Expanded surveys will be used to evaluate the program.
The goal of the Spare the Air Program is to promote public awareness and to influence people to adopt less polluting habits. This year the efforts to initiate behavioral changes to reduce air pollution will get special emphasis.
Weekend Effect
Beginning in the 1980s, ozone levels at some monitoring stations were observed to increase from Fridays to Saturdays, remain high or increase slightly on Sundays, and drop back down to weekday levels on Mondays. Dubbed the "Weekend Effect" by atmospheric scientists, this phenomenon is the subject of a concentrated study by the state Air Resources Board (ARB) to understand its causes and to learn how to deal with it.
During the smoggy warm summer months, two air basins in California often experience the weekend effect—the South Coast Air Basin and the San Francisco Bay Area Air Basin. In contrast, the Sacramento Area Air Basin exhibits little or no weekend effect. (Studies of the levels of particulate matter have shown that there is no weekend effect for this pollutant.)
Because health-based air quality standards are more often exceeded on weekends, the state ARB has been conducting a short-term study to examine existing data relating to the weekend effect. Data being examined include the meteorology, inventories of pollutants, photochemistry, and activities during the time when the weekend effect has been observed.
The weekend effect occurs more strongly at upwind monitoring sites, although it may not be observed at upwind sites with brisk prevailing winds that clear out air pollutants rapidly. It is less strong at downwind sites; sites far downwind and sites where much of the air pollution is transported from upwind sites usually do not exhibit it.
Ground-level ozone is formed in the atmosphere when its two precursor emissions, volatile organic compounds (VOC) and oxides of nitrogen (NOx), react together in high temperatures and sunlight. The optimum ratio of VOC to NOx for the formation of ozone is between 6:1 and 9:1. At ratios higher than 9:1, less ozone will be formed because less NOx is available for the reaction (a NOx-limited reaction). Similarly, conditions where VOC to NOx ratios are less than 6:1 are characterized as VOC-limited. Thus, decreasing either precursor reduces the amount of ozone formed. Also, if either precursor is increased so that the proportion between the two is even farther from the optimal ratios, less ozone may be formed. Other conditions affecting ozone formation include timing and spatial proximity of the emissions.
Four hypotheses are being evaluated as possible weekend effect causes:
More than one of these hypotheses may be needed to fully explain the weekend effect. The results of this short-term study are not expected to provide conclusive evidence, but will indicate the direction for further longer-term studies to identify and mitigate the causes of the higher ozone on weekends.
Central California Ozone Study
From June 1 through September 30, the large-scale Central California Ozone Study (CCOS) will collect meteorological and air quality data from the central section of California, from Redding in the north to the Mojave Desert in the south, and from the coast to the Sierra Nevada. This multi-million-dollar study is being undertaken by a public-private partnership operating under a joint powers agreement, involving a wide range of participants, including the EPA, the Air District, the ARB, the California Energy Commission, the Sacramento and San Joaquin Valley Air Districts, other central California air pollution control districts, and the private sector.
Planes and weather balloons will aid in collecting data at ground level and aloft. The data collected will improve the understanding of the role of meteorology on the formation and behavior of air pollutants and their precursors and emission sources and patterns. The information gathered will be used to develop an improved modeling system that will be used in preparing plans to attain the new federal 8-hour ozone standard, as well as to update the Clean Air Plan to attain the state ozone standard. Both plans are due in 2003. This year, the U.S. Environmental Protection Agency will announce which areas are not in attainment of the 8-hour standard.
Also ongoing is the California Regional Particulate Air Quality Study to provide information for planning to attain the new federal standards for fine particulates.
Ten years ago, in 1990, the Air District participated in another large-scale air quality study, the San Joaquin Valley Air Quality Study, which made substantial contributions to the understanding of ozone formation and provided data for improved ozone modeling tools. The CCOS study will expand on that knowledge and bring us closer to understanding the complexities of the atmosphere and how human activities affect it.
Adelia Sabiston
For more information:
Spare the Air: 1-800-HELP-AIR; http://www.sparetheair.org
Weekend Effect: ARB, 1-800-272-4572; Joann Myrhe, jmyhre@arb.ca.gov; http://www.arb.ca.gov/aqd/weekendeffect/weekendeffect.htm
Ozone Study: ARB, 1-800-272-4572; Saffet Tanrikulu, stanriku@arb.ca.gov; http://www.arb.ca.gov/ccaqs/ccos/ccos.htm
There are many ways to find out when your help is needed to Spare the Air:
• call 1-800-HELP-AIR
• visit the Spare the Air Website: http://www.sparetheair.org
• sign up for an e-mail notification
• watch and listen for alerts from the media, public agencies, and participating employers