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The chemical composition of intercepted cloudwater in the Sierra Nevada

Collett, Jeffrey L., Jr. and Daube, Bruce C., Jr. and Hoffmann, Michael R. (1990) The chemical composition of intercepted cloudwater in the Sierra Nevada. Atmospheric Environment Part A-General Topics, 24 (4). pp. 959-972. ISSN 0960-1686. doi:10.1016/0960-1686(90)90298-2.

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The chemical composition of cloudwater in the Sierra Nevada is dominated by NO_3^−, SO_4^(2−), and NH_4^+. Cloudwater pH is determined largely by the balance between the concentrations of these three species, although inputs of formic and acetic acid also are believed to be important, particularly when anthropogenic inputs are small. Cloudwater samples collected in Sequoia National Park (SNP) exhibited pH values ranging from 3.9 to 6.5; Yosemite National Park (YNP) cloudwater samples had pH values ranging from 3.8 to 5.2. Samples collected at YNP were more acidic than those collected at SNP. The difference in pH between the two regions appears to be due to relatively small differences in inputs of NO_3^−, SO_4^(2−), and NH_4^+. In the absence of inputs of NH_3, cloudwater pH values in the Sierra may fall below 3. Over 250 h of cloud interception were observed during a 12 month period at a cloud monitoring site at 1856 m elevation in SNP. Estimates of cloudwater deposition of NO_3^−, SO^4^(2−), and NH^4^+ indicate that cloud interception contributes significantly to regional acid deposition for closed forest canopies. Cloud interception may be the dominant deposition mechanism for isolated conifers and ridgetop canopies, where wind speeds are higher and cloudy air parcels can impact directly on foliar surfaces.

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Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1990 Published by Elsevier Ltd. First received 1 May 1989 and in final form 11 September 1989. We are grateful to the National Park Service for granting us access to the sampling sites in both Yosemite and Sequoia National Parks. We also would like to acknowledge the assistance of the Research and Resource Management staffs at Sequoia National Park and the Resource Management staff at Yosemite National Park. Several members of these staffs, including Dave Parsons, Tom Stohlgren, Annie Esperanza, and Diane Ewell of Sequoia National Park, and Teri Grosse, Charisse Sydoriak, Carol Moses, and Theresa Dunn of Yosemite National Park, made important contributions to the success of this project. Several people served as site operators during the course of the project: Bob Stanley, Tom Suk, Louis Andaloro, Paul Schlitt, Diane Ewell, and Meg Heim at Sequoia National Park, and Jan Cauthorn, Antonina Hines, and Theresa Dunn at Yosemite National Park. This project would not have been possible without their dedicated efforts. Our colleagues J. William Munger and Dieter Gunz also deserve recognition for their assistance in the field and laboratory and for numerous helpful discussions. This work was funded by the California Air Resources Board (CARB contract No. A6-185-32).
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California Air Resources Board (CARB)A6-185-32
Subject Keywords:Cloudwater; deposition; cloudwater acidity; ammonium; nitrate; sulfate; pH; cloud interception; automated cloudwater sampling; Sierra Nevada; California; Yosemite National Park; Sequoia National Park
Issue or Number:4
Record Number:CaltechAUTHORS:20150813-105955212
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Official Citation:Jeffrey L. Collett Jr., Bruce C. Daube Jr., Michael R. Hoffmann, The chemical composition of intercepted cloudwater in the Sierra Nevada, Atmospheric Environment. Part A. General Topics, Volume 24, Issue 4, 1990, Pages 959-972, ISSN 0960-1686, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59491
Deposited By: Ruth Sustaita
Deposited On:13 Aug 2015 19:03
Last Modified:10 Nov 2021 22:21

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