Chemical composition of precipitation

Wet deposition (D. ordinate at right) and concentration (C ordinate at left) of sulfate ions in precipitation as a function of precipitation quantity (P) 

3 Concerning details of chemical analyses the interested reader is referred to the original papers cited. 

Precipitation amount is normally reported in millimeters. One millimeter of precipitation means that 1 liter of water fell on 1 m2 of horizontal surface. Thus, if we multiply the concentration, expressed in mg l-1, by the precipitation quantity in mm, we obtain the mass of trace constituents in mg deposited on 1 m2 of the ground during the sampling time. The value of this parameter, termed the wet deposition, increases linearly with increasing precipitation quantity (see curve D in Fig. 45). 

The study of the chemical composition of precipitation is of interest for the evaluation of many scientific and practical problems. Thus, a knowledge of the chemical composition makes it possible to evaluate the degree of air pollution, the sink terms in the atmospheric cycle of aerosol particles and water soluble gases, the corrosiveness of atmospheric waters and the effect of precipitation on the material balance of soils, waters and vegetation. For these reasons, many precipitation analyses have been done, mostly in the last three decades. In this book only those works are mentioned in which an extensive network were (or are) operated, as in the American, Swedish and Soviet programs. 

We have seen that the trace constituents of precipitation are principally soluble acids and salts. Furthermore, it has been pointed out that, under tropospheric background conditions, water-soluble components are predominant in the particulate matter. For this reason we shall restrict our discussion to the ions found in precipitation water, including hydrogen ion. 

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Chemical compositions of hydrothermal solutions are summarized in Table 2.2 and chemical compositions of precipitates are presented in Table 2.3. Cl concentration of hydrothermal solutions precipitating base metals is high compared with hydrothermal solution not associated with base metal precipitations. 

Ayers, G. P., "The Chemical Composition of Precipitation A Southern Hemisphere Perspective, in Atmospheric Chemistry (E. D. Goldberg, Ed.), pp. 41-56, Springer-Verlag, New York, 1982. 

Discuss differences and reasons for those differences in the general chemical composition of precipitation, soil moisture, surface-waters and shallow (water-table) and deep (artesian) groundwaters. 

As part of the studies we have determined the dynamics of the change in the chemical composition of precipitation measured at some stations (Tashkent - Observatory, Kaunchi), by applying the commonly used indices (pH, electric conductivity, total ions, S04, NO3 ,... 

After analyzing the data on the chemical composition of the atmospheric precipitation measured over the territory of Tashkent city and Tashkent province, it was found that the local sources of atmospheric pollution have a certain effect on the chemical composition of precipitation (Figure 11). 

The next stage of the work included the study of the dynamics of the chemical composition of precipitation sampled at the meteostations of Almalyk, Tashkent and Chirchik, with the purpose of estimating the possible impact of the local pollution of the atmosphere on... 

Selezneva, E. S., 1972 Estimation of the background contamination of the atmosphere from the chemical composition of precipitation. Tellus 24 122-127. 

Georgii, H. W. (1982). Review of the chemical composition of precipitation as measured by the WMO, BAPMON Global Environmental Monitoring System. World Meteorological Organization, Geneva, Switzerland. 

Granat L., Suksomsankh K., Simachaya S., Tabucanon M. and Rodhe H., 1996. Regional acidity and chemical composition of precipitation in Thailand. Atmospheric Environment, 30 1589-1596. 

Sodeelund R (1982) On the difference in chemical composition of precipitation collected in bulk and wet-only collectors. Univ. of Stockholm, Report CM 57. 

Bootsma. H. A., M. J. Bootsma R. E. Hecky, 1996. The chemical composition of precipitation and its significance to the nutrient budget of Lake Malawi. In Johnson, T. C. E. O. Odada (eds.) The Limnology, Climatology and Paleoclimatology of the East African Lakes. Gordon and Breach, Amsterdam 251-265. 

The chemical composition of precipitation is a result of three different processes ... 

Various tests of the chemical composition of precipitation indicate that acids are present in larger quantities than would occur naturally. This phenomenon is attributed to ever increasing sulfur dioxide (SO2) and nitrogen oxides (NOx = NO + NO2) pollution of the air. In Europe, the acidification of precipitation was found to increase gradually in various countries. Because of this phenomenon and its possible environmental consequences, the number of rain water analyses has been increased. 

A variety of techniques to identify and quantify acid and base components in rainwater are applied to data for southern California. Charge balance calculations using major cation and anion concentration data indicate southern California probably had alkaline rain in the 1950 s and the 1960 s with the exception of the Los Angeles area which probably had acidic precipitation. Measurements of the chemical composition of precipitation collected in Pasadena, California, from February 1976 to September 1977 are compared with the charge balance and conductivity balance constraints. A chemical balance is used to determine the relative importances of different sources. The pH is found to be controlled by the interaction of bases and strong acids with nitric acid being 32% more important on an equivalent basis than sulfuric acid. The uncertainties in the various calculations are discussed. 

Table 2.1 Main calcium phosphate compounds. The first six compounds precipitate at room temperature in aqueous systems. The last six compounds are obtained by thermal decomposition or thermal synthesis. The five columns contain the name, the corresponding chemical formula, the Ca to P molar ratio, the mineral name, and the typical acronym, respectively. When x > 0 in the chemical composition of precipitated hydroxyapatite, one talks also about calcium-deficient hydroxyapatite (CDHA). Generally, x= 1 so that in most cases CDHA has the composition Ca9(HP04) (P04)60H...

Table 3 Chemical composition of precipitation in some Brazilian regions values in umol/1 mean/standard deviation) Amazon data are mean value for the whole basin, except snow samples.

That assumption, equal in metric units to about 35 mg NH4/L, was much too liberal. Recent worldwide measurements of the chemical composition of precipitation show values ranging mostly between 0.1 and 1 mg/L, with the U.S. continental mean of about 0.3 mg/L. Given the much less concentrated and much less productive agricultural activities of the first half of the nineteenth century, typical concentrations of ammonia in Europe in the 1840s could not have been above... 

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