DEPENDENCE OF THE CONTENT OF MICROCOMPONENTS ON THE DEGREE OF TOTAL MINERALIZATION IN GROUNDWATER

P. A. UDODOV, S. L. SHVARTSEV, N. M. SHVARTSEVA

Determining the dependence of the content of microcomponents in groundwater on the degree of its total mineralization is of great importance, since it makes it possible, as a first approximation, to assess the migration capacity of chemical elements under specific conditions, which is important in carrying out hydrogeochemical prospecting. Clarifying this question is also important from the standpoint that, if it were resolved positively, we would have a number of very simple and reliable prospecting hydrogeochemical criteria. Therefore the interest shown by researchers in solving this question is understandable; in recent times a number of contradictory opinions have been expressed on it. Thus, A. A. Brodsky [2] indicates that, with an increase in the total mineralization of groundwater, the copper content in it decreases. M. S. Gurevich [5], studying the content of microcomponents in the groundwater of the West Siberian artesian basin, comes to the conclusion that in “deep groundwaters, with increasing mineralization, the content of microcomponents in them does not increase.” P. A. Udodov, I. P. Onufrienok, and Yu. S. Parilov [10] note that “no regular influence of the total mineralization of waters on the content of metals in them is observed”; E. E. Belyakova [1], on the basis of her work carried out in regions with an arid climate, comes to the conclusion that “the ability of elements to accumulate in waters within a pH range specific to each of them leads to a direct or almost direct relationship between the degree of mineralization of the water and the content of the element,” and she places this direct relationship at the basis of compiling “medium-scale reconnaissance prognostic hydrochemical maps.”

To test this debatable question, material from hydrogeochemical studies in various regions of Siberia was used, as well as some published data. In doing so, we separately considered the main types of waters by chemical composition with definite pH values. Acid sulfate waters of the oxidation zones of sulfide deposits were also singled out separately; these have been most fully studied in the Norilsk copper-nickel deposit and the Gai pyrite deposit.

In order to obtain the most objective data for establishing the relationship, the method of mathematical statistics was applied. Since what interests us first of all is the very fact of the presence or absence of a relationship, we used the rank correlation coefficient \(R\) of van der Waerden [3], which has previously been used in geology and has yielded positive—

positive results [7]. The rank correlation coefficient is calculated by the formula:

\[ R = 1 - \frac{6\sum d^2}{n(n-1)(n+1)}, \]

where \(d\) is the difference between the ordinal numbers assigned to the correlated elements in accordance with decreasing contents,

\(n\) is the number of analyses.

To verify the statistical significance of the obtained values of \(R\), i.e., to prove that the found values of the rank correlation coefficients are not random deviations from zero, the dependence criterion \(R_\beta\) was used, calculated by the refined asymptotic formula, which makes it possible to obtain a better approximation to the exact limits than the normal and Student distributions:

\[ R_\beta = \frac{\psi(1-\beta)}{\sqrt{n-1}} \left\{ 1 - \frac{0.19}{n-1}\left[\psi^2(1-\beta)-3\right] \right\}, \]

where \(\psi\) is taken from table [3],

\(\beta\) is the specified significance level,

\(n\) is the number of analyses.

As usual, the relationship between the content of a microcomponent in waters and total mineralization was considered to exist if \(R > R_\beta\). The calculation was performed at \(\beta = 0.005\).

The obtained values of the rank correlation coefficient are given in Table 1; as a rule, they are considerably lower than the corresponding values of \(R_\beta\), i.e., for the most part there is no relationship between the elements studied and total mineralization. Let us consider this relationship in more detail by water types.

The correlation relationship between certain microcomponents and total mineralization for the hydrocarbonate type of waters was studied using the example of the Kolyvan-Tomsk folded zone, the Kuznetsk Alatau, the Western Sayan, and the northwestern part of the Siberian Platform (supra-permafrost and bog waters). In the calculation, only those points were selected that were not associated with knowingly known mineralization zones. As can be seen from the table presented, of the 39 cases obtained, only in 3 is there a correlation relationship, while in the remaining 36 it is absent; moreover, almost half of them (17 cases) have an inverse relationship (a negative value of \(R\)). It is interesting that all cases in which this relationship is observed can apparently be explained by the presence of the corresponding mineralization in the areas studied, although known deposits of these elements are not yet present there.

For the chloride type of waters, we used the materials of G. M. Rogov for the Kuznetsk coal basin and of A. E. Kontorovich for the deep waters of the West Siberian artesian basin. Of the 13 cases studied, only in one does the relationship under investigation exist, namely for barium in deep artesian waters. It is possible that this is connected with the peculiarity of its migration under these conditions. But one cannot fail to note also the fact that some of the studied wells are located in areas of oil fields. In the latter, as is known, elevated concentrations of barium in waters are often observed.

The sulfate type of waters was studied by us only within the oxidation zones of sulfide deposits (Norilsk and Gai), with a wide range of pH values. Under these conditions, of the 11 cases studied, the relationship under investigation is observed in 7, which amounts to 63.6%. At the same time, it is noted that the relationship is observed for the principal ore-forming

Table 1

Coefficients of rank correlation between the magnitude of total mineralization and the content of various elements in waters

forming elements. The elements, however, that occur in significant quantities in ores show no relationship with total mineralization. This is in full accord with the nature of weathering processes in oxidation zones: the increase in the total mineralization of groundwater is due chiefly to the presence of the sulfate ion—the product of sulfide oxidation—whereby the ore-forming elements pass into solution approximately in parallel with the sulfate ion. Often the lowered pH values of the waters help to keep them in solution.

The relationship between certain microcomponents and the total mineralization of groundwater for arid regions, using Central Kazakhstan as an example, was studied by G. F. Larionov et al. [6]. They convincingly showed that the contents of copper, lead, and zinc in waters do not depend on the total mineralization of the latter, and that no relationship between these quantities exists. As for molybdenum and uranium, in the mineralization interval studied (0.5–25 g/l), the authors indicate some dependence of the contents of these elements in the waters on the magnitude of their total mineralization, although this has not been proved mathematically.

Thus, it may be concluded that, in general, there is no relationship between microcomponents and the total mineralization of groundwater, especially in waters not directly associated with ore bodies. The existence of such a relationship is a particular, not a general, case and may be observed only under certain specific conditions, for example within some sulfide deposits.

The conclusion we have obtained does not contradict the general conditions governing the enrichment of groundwater with chemical elements; rather, it confirms the fact that some chemical elements pass into solution from rocks more rapidly and remain in it longer than others. This situation is connected with the action of a large number of natural factors and is reflected in the differing migrational capacity of chemical elements in groundwater. Thus, as early as 1934, B. B. Polynov [9] showed that the contents of chemical elements in rocks and in natural waters forming within those same rocks are not identical. Later this idea was reflected in the works of A. I. Perel’man [8] in characterizing landscape geochemistry. For ore deposits, the same was confirmed by the works of I. I. Ginzburg [4], P. A. Udodov, I. P. Onufrienok, Yu. S. Parilov [10], and other researchers, who showed that the contents of chemical elements in waters are functions of many variables: the pH and $Eh$ of the medium, the adsorption capacity of the rocks in which the groundwater occurs, the forms of migration of the elements, the solubility limits of the salts and hydroxides of these elements, their coprecipitation with various salts, the various internal properties of the chemical elements, and so forth.

Naturally, the behavior of different elements in waters is complex and is determined by specific natural conditions.

As for E. E. Belyakova’s conclusion about a direct relationship between the content of microcomponents in groundwater and the total mineralization of the latter, it was obtained through the use of an erroneous formula in the calculations, as we have already shown in one of our previous works [11]; therefore we shall not dwell on this question here.

Thus, the behavior of each element in groundwater, including its relationship with mineralization, must be considered in conjunction with the physicogeographical, geological, and structural features of the region. Only in this case can correct conclusions be reached.

References

1. E. E. Belyakova, A. A. Reznikov, L. E. Kramarenko, T. F. Kronidova. Hydrogeochemical method for prospecting ore deposits in arid and semiarid regions. Gosgeoltekhizdat, 1962.

2. A. A. Brodskii. Geochemical method for prospecting copper. Gosgeoltekhizdat, 1956.

3. B. L. Van der Waerden. Mathematical Statistics. IL, 1960.

4. I. I. Ginzburg. An attempt to develop the theoretical foundations of geochemical methods for prospecting ores of nonferrous and rare metals. Gosgeoltekhizdat, 1957.

5. M. S. Gurevich. Rare and dispersed elements in artesian waters. Bulletin of VSEGEI, issue 2, 1960.

6. G. F. Larionov, V. Ya. Rivman, G. B. Sveshnikov. On the characteristics of the migration of copper, lead, zinc, molybdenum, and uranium in the groundwaters of Kazakhstan. Report at the Interuniversity Conference on Hydrogeochemical and Paleohydrogeological Methods of Research, held in Tomsk in February 1965.

7. V. V. Mogarovskii. On the correlation of thallium with zinc at the Daraiso sulfide deposit (Central Asia). Geochemistry, No. 7, 1962.

8. A. I. Perelman. Geochemistry of the Landscape. Geografgiz, 1961.

9. B. B. Polynov. Weathering Crust. Publishing House of the Academy of Sciences of the USSR, 1934.

10. P. A. Udodov, I. P. Onufrienok, Yu. S. Parilov. An experiment in hydrogeochemical study in Siberia. Publishing House, issue 1962.

11. P. A. Udodov, G. M. Rogov, N. M. Rasskazov, S. L. Shvartsev, A. A. Lukin. On the article by E. E. Belyakova “Principles and methods for compiling prognostic hydrochemical maps for ore mineral resources.” Soviet Geology, No. 10, 1963.