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Processes controlling the composition of precipitation at a remote southern hemispheric location: Torres del Paine National Park, Chile

1996; American Geophysical Union; Volume: 101; Issue: D3 Linguagem: Inglês

10.1029/95jd03229

2156-2202

James N. Galloway, W. C. Keene, Gene E. Likens,

Marine and coastal ecosystems

Precipitation composition measured at Torres del Paine National Park, Chile (TdP) (51°10′S, 71°58′W), between 1984 and 1993 was acidic (volume‐weighted‐average pH of 4.96) with a dilute seawater component. H + was the dominant non‐sea‐salt (nss) cation; in decreasing order of abundance, nss anions were HCOO − , Cl − , SO 4 = , CH 3 COO − , and NO 3 − . Relative to lower latitude, remote locations, concentrations and per‐event depositions of nss SO 4 = , NO 3 − , and NH 4 + at TdP were lower; those of HCOO t (HCOO − + HCOOH) and CH 3 COOH t , (CH 3 COO − and CH 3 COOH) were similar; and those of CH 3 SO 3 − were higher. Concentrations and deposition fluxes of HCOO t , CH 3 COO t , nss SO 4 = , CH 3 SO 3 − , and NH 4 + varied seasonally with summer maxima and winter minima. Carboxylic acids probably originated from both direct terrestrial emissions and oxidation of hydrocarbons emitted by marine and terrestrial biota. Nss SO 4 = and CH 3 SO 3 − originated primarily from oxidation of biogenic (CH 3 ) 2 S emitted from the southern Pacific Ocean. Direct emissions of NH 3 from upwind terrestrial and marine ecosystems probably accounted for most observed NH 4 + . NO 3 − concentrations and depositions were highest during the latter part of austral winter and spring suggesting abiotic controls. Transport of precursors from lightning, biomass burning, and fossil‐fuel combustion at lower latitudes and possibly transport of reactive N from the stratosphere apparently contributed oxidized N to the southern Patagonian troposphere. Although the ionic strength of precipitation at TdP is currently among the world's lowest, future changes are likely because of increases in local and regional population and energy and food production.