Precipitation composition at Cape Grim, 1977-1985

Abstract

Rainwater composition data resulting from monthly, wet-only collections of maritime rain at Cape Grim, Australia, in the period April 1977 to March 1985 have been critically appraised.High local wind speeds prove to be a major determinant of data quality: extremely high sea· salt loadings (average rainwater sodium and chloride concentrations in the low millimolar range) make estimation of excess sulfate impossible against a background sulfate concen· tration of about 150 µeq/l derived from sea-salt. The extreme wind speeds also cause consider· able erosion of the Cape surface, leading to the ubiquitous presence of local soil components in collected rainwater. Both the rainwater data and data from the analysis of local soil samples show that these soil components significantly elevate rainwater pH (observed mean 6.01) and the concentrations of potassium and calcium. Effects upon other ions appear to be minimal, but cannot be ruled out.Calculation of pH for rainwater having the long-term mean composition, but with the effects of local contamination excluded, yielded a value of 5.10. Further calculations in which sea-salt content of the rainwater was varied over the range observed at Cape Grim indicated that at this site, sea-salt alkalinity may be a major determinant of rainwater pH, leading to pH variations from < 5 to > 6.

Fog and rainwater composition in rural SE Australia

“…At AGAL pH and conductivity were redetermined, sodium, potassium, magnesium and calcium concentrations were determined by flame AA, ammonium by the indophenol-blue colorimetric method, and the anions methanesulfonate, formate, acetate, chloride, nitrate and sulfate were determined by suppressed ion chromatography (Dionex AS4A columns). Precision for all individual analyses was to better than 10% uncertainty (see Ayers and Ivey, 1988).…”

A Density Functional Theory Study of the Hydrates of NH3·H2SO4 and Its Implications for the Formation of New Atmospheric Particles

“…He found that samples could quickly become contaminated with ammonia if left exposed to the laboratory environment. Today, it is commonly accepted that many early stratospheric aerosol measurements were contaminated with tropospheric ammonia (with a typical scatter of 20%) after they were sampled. The question of the importance of ammonia's involvement in rapid aerosol formation has still not been resolved …”

Fourth Symposium on our Environment

“…Likens et al (1987), for example, chose central north Australia as the site for a remote, continental rainwater sampling site in their Global Precipitation Chemistry Project. Results from this site, and the BAPMoN baseline station at Cape Grim, Tasmania (Ayers and Ivey, 1988) show convincingly that nss-sulfate and nitrate concentrations of < 10 jleq/L are to be expected in 'unpolluted' regions . In contrast the studies of Ayers and Gillet (1981) and Ayers et al (1986) in the urban area of Sydney (pop.…”

“…Australia Bridgman (1988) provides an excellent summary of work on rainwater composition that had been carried out in Australia prior to 1988: he referenced 16 separate datasets covering clean marine, clean continental, and polluted continental regions. Several other works have been published since the review of Bridgman (1988); see Ayers and Gillett (l988c,d), Ayers and Ramsdale (1988), Gillett and Ayers (1988), Bridgman et al (1988), Ayers and Ivey (1988), Noller et al (1990) and Gillett et al (1990).…”