Mereni elektrochemickych velicin v podzemnich vodach v hlubokych vrtech

An electrical measurement of hydrochemical parameters in situ is a common part of groundwater geochemistry research. Typical measurements include temperature, pH, conductivity, redox potential and concentration of dissolved oxygen. Water is highly variable medium whose properties change with time. The properties depend on treatment of water samples. The temperature of water, redox potential and concentration of dissolved oxygen are sensitive hydrochemical parameters that can be measured only in the field, or immediately after sample collection. A hydrochemical multi-parameter probe ISY EXO¹(Fig. 1) was used for the research into electrochemical parameters in groundwater in a borehole at depth. The Mel-2 borehole was chosen for the research at locality Melechov - Kostelní les near Ledeč nad Sázavou. Hydrochemical probe ISY EXO¹ was sunk into the Mel-2 borehole at depth of 92 m meters below ground surface. Groundwater was pumped from the same depth level into a measuring cell at the surface. Parallel measurements were performed in situ and ex situ and they were compared to each other. Both measurements shown close values of pH, specific conductivity and concentration of dissolved oxygen after stabilization of the parameters in the measuring cell. Time required for the stabilization of the parameters was 30 to 45 minutes with the cell water inflow of 0.8 l.min^-1(Figs 2, 4). On the other hand, measurements of the temperature of water and redox potential in the measuring cell were inconsistent with the measurements performed by the probe ISY EXO¹ in situ. The redox potential did not reach a stable value in the measuring cell (Fig. 6); the temperature measurement in the measuring cell showed 0.8 °C lower values than the measurement by the probe in the borehole. This difference is 76 % of the local thermal gradient.
A comparative study of geochemical vertical profiles and four-month monitoring of the measured parameters at the depth of 92 m were performed (Figs 3, 5, 7). The probe ISY EXO¹ proved to be a useful technical tool during testing in a research into geothermal anomalies, vertical geochemical profiling within boreholes and flooded mines. It is suitable for a long-term monitoring of the electrochemical parameters in both groundwater and surface water.

References

Holeček, J. - Myška, O. - Bláha, V. (2014): Studium elektrochemických parametrů podzemních vod ve velkých hloubkách pomocí sondy ISY EXO1. In: Halousková, O.: Inovativní sanační technologie ve výzkumu a praxi VII, 1-15. - Vodní zdroje Ekomonitor spol. s r.o. Chrudim.

Rukavičková, L. - Bláha, V. - Otrubová, D. (2006): Hydrogeologický výzkum ve vrtech Mel-1, Mel-2, Mel-3, Mel-4 a Mel-5. Projekt: Provedení geologických a dalších prací na testovací lokalitě Melechovský masiv - 2. etapa. - MS SÚRAO, Praha.