Rainwater acidity

CCN). Changes in the concentrations of CCN may alter the cloud droplet concentration, the droplet surface reflectivity, the radiative properties of clouds (cloud albedo) (2), and hence, the earth s climate (8-101. This mechanism has been proposed for the remote atmosphere, where the radiative properties of clouds are theoretically predicted to be extremely sensitive to the number of CCN present (ID). Additionally, these sulfate particles enhance the acidity of precipitation due to the formation of sulfuric acid after cloud water dissolution (11). The importance of sulfate aerosol particles to both radiative climate and rainwater acidity illustrates the need to document the sources of sulfur to the remote atmosphere. 

Sulfuric acid is the most wideiy produced industriai chemicai. it is aiso formed when suifur oxides, emitted into the atmosphere by burning fossii fueis high in suifur content, dissoive in water. This makes rainwater acidic, forming acid rain. 

The HNO3 may be washed out of the air by rainwater (acid rain), or it may react with traces of NH3 in the air to form solid NH4NO3, 2, particulate pollutant. 

The notion that chemical reactions in the aqueous phase may be important to atmospheric chemistry dates back at least 30 yr, when Junge and Ryan (1958) called attention to the great potential of cloud water for the oxidation of dissolved S02 by heavy-metal catalysis. At that time the process appeared to be the only viable oxidation mechanism for atmospheric S02. Later, when the concept of OH radical reactions gained ground, the gas-phase oxidation of S02 by OH was recognized to be equally important. The recent revival of interest in aqueous phase reactions is connected with efforts to achieve a better understanding of the origins of rainwater acidity. An oxidation of N02 to nitric acid also takes place in cloud water. Contrary to previous ideas, however, this process was recently shown to have little influence on atmospheric reactions of N02. 

Some earlier data on rainwater acidity in Thailand were summarized by Ayers... 

American atmospheric scientists were unable to find support for even the very limited precipitation network. This is widely recognized as possible short-sightedness in view of present questions about the impact of rainwater acidity on ecological processes in the northeastern United States. 

Volume-weighted H concentration in precipitation in Wilmington, NC, decreased by a factor of 2 between 1985 and 2005, typical of the nationwide decrease of rainwater acidity. Error bars are 11 standard deviation. [From. D. Willey, R. ]. Kieber, and G. B. Avery, r., Environ. Sci. Technol. 2006,40, 5675.] In volume weighting, [H ] in each rainfall is multiplied by the volume of that rainfall to get moles. Total moles for the year are divided by total volume for the year. 

The principal components that make rainwater acidic are nitric and sulfuric acids, which are strong acids. Each molecule oi strong acid or strong base in aqueous solution dissociates completely to provide one molecule of or OH . Nitric acid is a strong acid, so the reaction... 

A certain sample of rainwater gives a yellow color with methyl red and a yellow color with bromthymol blue. What is the approximate pH of the water Is the rainwater acidic, neutral, or basic (See Figure 16.10.)... 

This makes rainwater acidic, forming acid rain. 

Figure 2 shows weekly pH variations in rainwater, throughfall and stream water at Tijuca National Park. It is clear that during its course to stream channel, rainwater acidity decreases. 

Rainwater acidic 15-35 9 Resistant only slight changes to weight dimensions or properties the medium does not cause any irreversible damage to the polymer "... 

Rainwater acidic 15-35 9 Resistant only slight changes to "... 

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