Calibration of collection procedures for the determination of precipitation chemistry |
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| Authors: | James N Galloway Gene E Likens |
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| Institution: | 1. Section of Ecology and Systematics, Cornell University, 14853, Ithaca, New York, U.S.
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| Abstract: | Precipitation is currently collected by several methods, including several different designs of collection apparatus. We are investigating these differing methods and designs to determine which gives the most representative sample of precipitation for the analysis of some 25 chemical parameters. The experimental site, located in Ithaca, New York, has 22 collectors of 10 different designs. The designs include bulk (wet and dry deposition collected together), wet only (only rain and snow) and wet/dry (collects wet and dry deposition separately). In every sampling period, which varies from 1 day to 1 mo, depending on the time variable being tested, the following chemical parameters are determined: conductivity, pH, Ca, Mg, Na, K, NH4, N03, Ntotal Si04, PO4, Ptotal, Cl, SO4, DOC, Zn, Cu, Mn, Fe, Al, Ni, Cd, Pb, Ag, DDT, DDE, Dieldrin and PCB's. The results of the investigation lead us to conclude that: - Precipitation samples must exclude dry deposition if accurate information on the chemical content of precipitation is required.
- Substantial contamination results when glass and plastic collectors are used to sample precipitation for inorganic and organic components, respectively.
- The inorganic components of precipitation samples of low pH (3.5 to 4.5), with the exception of P04 and Cl, exhibited no significant change in concentration when stored at 4\dgC for a period of 8 mo. We believe this is due to the stabilizing influence of a large concentration of H ions.
- If quantitative information on the chemical composition is required, precipitation samples should be collected at no longer than weekly intervals if immediate collection is not possible.
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