Abstract
We have completed a paleolimnological analysis of sediment cores from four lakes in the Sierra Nevada Range of California (USA). The diatom-inferred pH profile from Harriet Lake in Yosemite National Park (present pH=6.52) indicates no significant trends over the last 250 years. Inferred pH from Emerald Lake in Sequoia National Park (present pH=6.10) indicates a very small increase (<0.1 pH unit) over the past 60 years and perhaps another small increase (ca. 0.15 pH unit) since 1976. Eastern Brook Lake in Inyo National Forest (present pH=7.06) shows evidence of both long-term alkalinification (ca. 0.3 pH unit over the last 200 years) and pH fluctuations since 1970. Lake 45 in King's Canyon National Park (present pH=5.16) appears to have acidified slightly (ca. 0.2 pH unit) over the last 60 years. Factors causing the observed trends are uncertain, but a role for acidic deposition cannot be ruled out.
Published Version
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