Lauri Solismaa, Teemu Karlsson & Päivi Kauppila, Geological Survey of Finland, P.O. BOX 1237, FI-70211 Kuopio, FINLAND, e-mail: lauri.solismaa (at)gtk.fi, teemu.karlsson(at)gtk.fi
Field measurements are usually the most simple and effective way of monitoring the changes in the environment and to make a preliminary characterisation of the mine wastes or to complement the characterisation data from the laboratory analyses and tests.Techniques of measurement are developing rapidly. It won’t propably take long to see that also element contents of mine influenced waters can be monitored reliably in situ. Methods include e.g. mineralogical analysis, chemical, physico-chemical, geophysical and geotechnical measurements. For example, when taking water samples, field measurements of pH, EC, alkalinity and dissolved oxygen are essential. Field measurements typically provide quick overview of the waste material or the environmental conditions resulting from the waste disposal and can be used to focus the more detailed sampling and analysis as well as more sophisticated field studies.
Picture 1: Measuring different parameters from seepage water in field conditions with multi parameter water quality sonde. Picture: Pekka Forsman GTK
Descriptions of typical field measurements made from water, soil and aquatic sediments, and mine waste material are explained to more detail below:
- Field methods for mineralogical and chemical tests
- Special probes for direct measurements
- Mineralogical on-site observation, visual description
- Near infrared spectrometer (IRS)
- Chemical additions (for observing reactions indicating mineral types)
- The advanced space borne thermal emission and reflection radiometer (ASTER) (mineral alteration products)
- Thermal image camera (heat generation (sulfide oxidation))
Observations concerning the field investigations of mine wastes:
- Analysis of the solid samples, information that can be obtained in the field: mineralogy (with a hand lens), grain size (simple field methods for the bulk grain sizes), hydraulic conductivity (infiltration tests), moisture content (saturation index), paste pH and totally dissolved solids (TDS), and drainage chemistry (rainfall simulation tests or similar).
- Sampling of seepage water or groundwater below the tailings pile may provide information on the geochemical processes within the pile and work as a full scale column test.
- Waste rocks
- The possible analyses for the solids are the same as for the tailings
- Macro and matrix flow monitoring