A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 2 – air quality

Panek, Jeanne; Saah, David; Esperanza, Annie

The condition of air quality in Sequoia and Kings Canyon National Parks (SEKI) is a consequence of its geographic location relative to significant sources of air pollution. The Parks are downwind of numerous major urban areas with associated industrial activity, two heavily-travelled transportation corridors (I-5 and CA 99), and the extensive San Joaquin Valley agricultural landscape which is among the largest producers of agricultural products in the U.S. Long-range transport of pollutants from Asia and elsewhere also contribute to upwind sources. The Parks are within the San Joaquin Valley Air Basin, the southern half of California’s broad central valley, which is classified as ―extreme non-attainment‖, the worst category relative to federal standards of ozone. Over ten percent of the state’s population lives in the eight counties of the SJVAB and air pollution emission sources within the SJV account for about 14 percent of total statewide emissions. Since 1980, population growth in the SJV has been more rapid than in other parts of California, and is projected to reach over 5 million by 2020 (almost 12% of state population). Geographically, the SJVAB is rimmed to the west by the Coast Range, to the south by the Tehachapi Range, and to the east by the Sierra Nevada, and therefore constrains pollutants within its boundaries. General surface air flow patterns carry contaminants southeastward from their sources, through the San Joaquin Valley to the southern end where they are blocked by the Tehachapi Range. From here, pollutants are forced upward and outward, into major drainages, or re-circulate northward along the western flanks of the Sierra Nevada in a vortex called the Fresno Eddy. Sequoia and Kings Canyon National Parks are situated on the eastern edge of the SJVAB and the lower slopes and drainages of the western flanks of the Parks are severely impacted by air pollution, including the Fresno Eddy. Airflow patterns in the SJVAB that bring pollutants, especially ozone, to the Parks have been well-characterized. Factors influencing direction, strength, and pollutant load include incursions of marine air through major western passes into the SJVAB, upslope and downslope winds in the Sierra Nevada, temperature, and air pressure patterns. The conditions of highest pollutant loading to the west slopes of the Sierra occur during anticyclonic events, high pressure systems that push down and trap polluted air onto the lower slopes of the Sierra Nevada, near the foothills of Sequoia. Sequoia and Kings Canyon National Parks have the most severe air pollution impacts on vegetation of any other western national park. The Mediterranean climate of California has implications for timing, type, and distribution of pollutant deposition. Very little precipitation falls between June and October, temperatures are hot, and the air is dry, favoring particulate and gaseous pollutant deposition. Pollutants can build up on leaf and other surfaces, and then wash off when it rains, creating pollutant pulses into soils, streams and lakes. Precipitation between the months of November and May delivers wet chemical species, but generally cleans the air of particulates. This, combined with cooler temperatures, leads to decreased dry and gaseous pollutants in the winter. High elevation snowpack is generally deep, up to 4 m, and can sequester pollutants throughout the winter until released by summer snowmelt.Pollutants of concern to SEKI, and summarized in this report, include ozone and its precursors, wet and dry nitrogen deposition, wet and dry sulfur deposition, fine and coarse particulates, mercury, pesticides, and other contaminants.

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 2 – air quality

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