Sulfate in rain

Coplen TB, Brand WA, Gehre M, Groning M, Meijer HA, Toman B, Verkouteren RM (2006) New guidelines for S C measurements. Anal Chem 78 2439-2441 Cortecci G, Longinelli A (1970) Isotopic composition of sulfate in rain water, Pisa, Italy. Earth Planet Sci Lett 8 36 0... 

The oxidation of SO in rain drops by means of O3 and H2O2 is consequently the dominant non-catalytic reaction. It is interesting to note that the HiOi-oxidation is rather insensitive to decrease of pH. These reactions due to their rates are probably quite capable of producing enough sulfate in rain water to account for observed levels. 

The other removal process, wet deposition, removes sulfur from the atmosphere as sulfates in rain. This would be the fate of sulfuric acid produced via the homogeneous oxidation of SO2, but oxidation also proceeds within droplets. Aqueous sulfur dioxide is oxidized only slowly by dissolved oxygen, but the production of sulfuric acid, which is much stronger, leads to acidification... 

Junge, C. E., and R. T. Werby. 1958. The concentration of chloride, sodium, potassium, calcium and sulfate in rain water over the United States. J. Meteorol. 15 417-25. 

Fig. 10-7. Sulfate in rain water. Upper part Global average distribution of concentration in units of mg S/liter. Lower part Deposition rate in units of g S/m2 yr. [From Georgii (1982), with permission.]...

Pollutants are removed from the atmosphere by rain and snow and are transferred to soils, natural waters, and vegetation by wet and dry deposition processes. Through these processes, plants are exposed periodically to substances dissolved in atmospheric precipitation and to gaseous pollutants. The major soluble constituents in rain and snow in the eastern U.S. are hydrogen, sulfate, and nitrate ions and there is concern over the environmental influence of these substances, particularly acidity (Jacobson et al., 1976). Knowledge of plant nutrition and response to pollutants raises the question of whether it is necessary to consider the supply of nitrate and sulfate in rain and the concentration of ozone in the atmosphere when determinations are made of the effects of acidic precipitation on vegetation of the eastern U.S. 

Our results indicate that both the exposure of plants to nitrate and sulfate in rain and to ozone in the atmosphere are important factors to consider when determinations are made of the effects of acidic precipitation on vegetation. The qualitative character and magnitude of effects of acidic precipitation may change with different conditions of plant nutrition and air pollution. Future experiments should be performed with these factors controlled or carefully measured before a full understanding of the effects of acidic precipitation on vegetation can be obtained. 

JACOBSON I think the clearest way of describing the data in Table III is that the applications of simulated rain with the higher sulfate to nitrate ratios increased the dry mass of apical leaves and roots of lettuce plants. Unfortunately, we have no information on the sulfur content of the soil. Perhaps addition of sulfate in rain can overcome sulfur deficiency in the soil. Future experiments on the effects of acid rain should always include measurement of soil sulfur. 

The total amount of sulfur deposited agrees well with the total amount of sulfur emitted (Table 4). In fact, the agreement is better than one might expect considering the moderate uncertainties in some of the terms. This agreement indicates that we have not overlooked a major source of sulfur. We conclude that man-made sulfur emissions are the chief cause of acid sulfate in rain in the eastern U.S. and that these emissions are also responsible for dry deposition of acid sulfate. 

Dr. Mohnen... as I understand your conclusion, it is that the quantity of sulfate... in rain that came from the Midwest sector was roughly comparable to that which came from other sectors. Is that a fair summary " Mohnen balked. He had to acknowledge that two thirds of the acid sulfate in rain came from the Midwestern sector. He was then forced to address the finding that so little of the pollution came from the Northeast. 

Paints and coatings for automobiles have not been immune to damage by air polluhon. Wolff and co-workers (13) found that damage to automobile finishes was the result of scarring by calcium sulfate crystals formed when sulfuric acid in rain or dew reacted with dry deposited calcium. 

For both polluted and remote conditions, therefore, the cycling of sulfur from low oxidation state gas to sulfate particles and then back to the surface in rain takes place on a time scale of a few days. 

About half the manmade emissions of sulfur dioxide become sulfate aerosol. That implies that currently 35 Tg per year of sulfur in sulfur dioxide is converted chemically to sulfate. Because the molecular weight of sulfate is three times that of elemental sulfur, Q is about 105 Tg per year. Studies of sulfate in acid rain have shown that sulfates persist in the air for about five days, or 0.014 year. The area of the Earth is 5.1 x lO m. Substituting these values into the equation for B yields about 2.8 X 10 g/m for the burden. 

C04-0146. The largest single use of sulfuric acid is for the production of phosphate fertilizers. The acid reacts with calcium phosphate in a 2 1 mole ratio to give calcium sulfate and calcium dihydrogen phosphate. The mixture is crushed and spread on fields, where the salts dissolve in rain water. (Calcium phosphate, commonly found in phosphate rock, is too insoluble to be a direct source of phosphate for plants.) (a) Write a balanced equation for the reaction of sulfuric acid with calcium phosphate, (b) How many kilograms each of sulliiric acid and calcium phosphate are required to produce 50.0 kg of the calcium sulfate-dihydrogen phosphate mixture (c) How many moles of phosphate ion will this mixture provide ... 

Other sources of river sulfate Include natural biogenic emissions to atmosphere delivered to land in rain (3%), votanism (8%) and pyrite weathering (11 %). 

Fig. 6 Annual average sulfate concentrations in snow and ice at the high-Alpine site Colle Gnifetti and in rain at the lower-elevation site Diibendorf. Data of Diibendorf are from Nabel [24]...

The effects of anthropogenic sulfur dioxide on the remote marine atmosphere may be evident from rainwater studies by Chukhrov et al. (60) in which the isotopic composition of sulfur in rain was studied systematically at great distances from the continent. Rainwater sulfate ranged from +12.1 to +15.0 0/00 over the Atlantic and from +9.5 to +16.2 0/00 over the Pacific, with a one month average value of +13.3 0/00 for the two oceans. Their study included measurements of rainwater sulfate from a wide variety of continental areas and found that most inland 634S values were significantly lower than those over the oceans. The oceanic rainfall sulfate was most likely a mixture of the isotopically lower continental sulfate and the more enriched marine sulfate. 

Sulfite and bisulfite in rain water are rapidly oxidized to sulfate by the catalytic effect of metallic ions such as Fe(III) and Mn(II). The rates of oxidation of S(IV) in test solutions were measured using ion chromatography. The rate constant, k, measured for a 12.5 yM S(IV) solution was found to be 0.6-10.4 hr 1 at pH 3-6 in the presence of 1.8-yM Fe(III) and 0.18 yM Mn(II) catalysts, and 0.4-5.9 x 10 J hr 1 without the catalysts. Triethanolamine (TEA) was used to stabilize actual rain water samples prior to analysis. 

In recent years, the effects of acid rain on lake water, heavy metals contaminated soils and structural materials have been widely discussed (1). Sulfur and nitrogen contained in fossil fuels are released into the atmosphere by combustion. Sulfur and nitrogen oxides dissolve in rain drops as bisulfite, sulfite and nitrite ions. These components are further oxidized into sulfate and nitrate ions. Since these species lower pH, it is important to accurately determine them in rain water. However, these ions are difficult to analyze because they rapidly oxidize in the presence of catalysts such as ferric and manganous ions. Light, temperature, and pH also affect the oxidation rate of S(IV). 

There is sufficient H202 in clouds to oxidize the S02 which reaches cloud height and calculations estimate that the multiphase oxidation of S02 by H2O2 accounts for most of the sulfuric acid present in rain, and over 70% of the sulfate aerosol observed in the atmosphere [79]. The aerosol is produced after evaporation of cloud droplets. It has been found in experiments carried out in the real atmosphere that the overall rate of oxidation of S02 in clouds is many times faster than would be predicted from using laboratory-based measurements [80]. 

The alternative process, wet deposition, deposits the sulfur in rain or other forms of precipitation. Here it is largely as sulfate, which has been incorporated from aerosols or through oxidation of dissolved sulfur dioxide. Sulfate particles can also be dry deposited to the Earth s surface. 

Globally, about half of all atmospheric sulfate is derived from combustion of fossil fuels and half from natural sources (Berner and Bemer 1987). It has been estimated that anthropogenic sources are responsible for 90% of the total atmospheric sulfur deposition in eastern North America, which occurs as dry deposition of SO2 gas and sulfate particles or dissolved in rain. The highest amounts of sulfate and nitrate in U.S. rain, which are found in the northeast [Fig. 8.7(a) and Fig. 8.7(b)], are... 

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