Page 100 - Geochemical Remote Sensing of The Sub-Surface

Geoelectrochemistry and stream dispersion 77

Fig. 2-53. Results obtained by polarographic logging (PL) at the Altyn-Topkan polymetallic
deposit, northern Tajikistan: (A) cathodic logging polarograms of the discrete mode of PL; (B)
distribution of manganese with depth obtained with the discrete mode of PL; (C) distribution of
manganese with depth obtained with the continuous mode of PL; 1- ore interval (galena,
sphalerite, pyrite); 2- potential of the polarographic waves (reproduced with permission from
Klochkov et al., 1989).

S 2-. Using PL it is straightforward to obtain the levels and pattems of the background
distribution of these ions in groundwater, including their hydrochemical zonation. Figure
2-54 shows polarograms from such an investigation: polarogram 2, which has two
polarographic waves of dissolved gaseous O2, is typical for boreholes crossing the
oxygenated part of a deposit; polarograms 1 and 3, on which the corresponding waves
are absent, pick out the non-oxygenated zones, and here polarographic waves reveal that
Fe 2+ and S 2 are present; polarogram 4 shows that the concentration of C1- is independent
of zonality and practically constant at 200-300 mg/1.
Indicative polarographic waves on polarograms have been noted in an area where
industrial contamination includes sulphuric acid. By means of correlation with chemical
analyses of water samples, it was established that these are waves of U022+, V02 +, Fe z+
and Mn 2+ (Fig. 2-55). It is necessary to point out that concentrations of iron and
manganese in the industrial effluent are tens to hundreds of times higher than
concentrations in natural waters.