Point Reyes National Seashore Air Quality Information
Overview
Point Reyes NS is located in the San Francisco Bay Area Air Basin, a predominantly urban air basin with substantial emissions of air pollutants. However, its coastal location near the northwestern edge of the air basin, combined with prevailing northwesterly winds off the Pacific Ocean, place the seashore in a generally upwind position relative to the urbanized portions of the air basin. However, during certain seasons (late summer and early fall), prevailing winds change and the seashore is often impacted by a general haze, which significantly impairs visibility. The principal air pollutants of concern in the seashore are ozone precursors (nitrogen oxides and volatile organic compounds) from mobile sources and particulates from road dust, construction, and residential fuel combustion. Sulfur dioxide emissions are relatively low in the area.
The air quality related values (AQRVs) of Point Reyes NS are those resources that are potentially sensitive to air pollution and include visibility, water quality, soils, vegetation, and wildlife.
Visibility is a sensitive AQRV in Point Reyes NS. Although visibility in the seashore is still superior to that in many parts of the country, visibility is sometimes impaired by light-scattering pollutants (haze). The U.S. Environmental Protection Agency’s Regional Haze regulations require States to establish goals for each Class I air quality area to improve visibility on the haziest days and ensure no degradation occurs on the clearest days. As part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, visibility in Point Reyes NS has been monitored using an aerosol sampler (1998-present) and an automatic 35mm camera (1987-1995). An analysis of 1990-1999 data from the seashore indicates that visibility in the area is improving on both the clearest days and the haziest days.
A web camera was installed in the Point Reyes Lighthouse in January 2004. Digital photos showing visibility conditions at the seashore will be updated every 15 minutes on the NPS NatureNet Air Resources web page. Meteorological information will also be available on the web site.
Surface waters in Point Reyes NS are well buffered and unlikely to be sensitive to acidification from deposition of nitrogen and sulfur compounds. However, soils and vegetation in the park may be sensitive to nutrient enrichment from nitrogen deposition. There is evidence that atmospheric deposition of nitrogen may play an important role in the ongoing replacement of native plant species with exotic, invasive annuals in some coastal sage scrub vegetation communities of California. Native plants that have evolved under nitrogen-poor conditions are replaced by invasive species that are able to take advantage of increased nitrogen levels.
Estimates of wet atmospheric deposition can be obtained from the NPS Air Atlas website. These estimates indicate that wet deposition rates for nitrogen and sulfur are relatively low. There is no dry deposition monitoring in the area.
Several plant species that occur in Point Reyes NS, including Sambucus mexicana (blue elderberry) and Artemisia douglasiana (Douglas’ sagewort, mugwort), are known to be sensitive to ozone. Ozone has been monitored with a continuous analyzer from 1987- 1992 and with passive monitors from 1999-present. Ozone concentrations and cumulative doses are relatively low and not likely to induce vegetation injury.
In 2002, the California Air Resources Board installed a fine particle (PM 2.5) continuous mass monitor at Point Reyes NS to serve as a coastal clean background site for the State’s PM 2.5 network.
Additional information relative to air quality and air quality related values at Point Reyes NS is available in T. Sullivan et al. 2001. Assessment of Air Quality and Air Pollutant Impacts in Class I National Parks of California (April 2001, pdf 6.24mb). National Park Service. Denver, CO.