Chemical stability checklist

Lauri Solismaa, Kaisa Turunen, Geological Survey of Finland, PO Box 1237, 70211 Kuopio, Finland; lauri.solismaa@gtk.fi, kaisa.turunen@gtk.fi

Environmental sampling and field assays

The purpose of the geochemical and hydrogeochemical studies is to assess the potential impacts of past mining activities to the environment in comparison to natural geogenic or other relevant background and to estimate possible environmental risks, as well as to mitigate and prevent harmful impacts in the long-term. In addition, the aim of each environmental study is set in the scoping of the sampling campaign for field and laboratory analyses. Laboratory instruments are usually bulky, expensive to operate and maintain, and require fully equipped laboratories. In contrast, field assays aim at almost similar detection limits as fixed lab methods and can produce a large number of results in a short time and with a fairly low cost. Field assays can be used in screening the most essential sampling sites for more detailed laboratory analyses. However, for many variables reliable and accurate in situ analysis methods still need further development, but some technological advances in a variety of instruments have been made.

The sampling media have to be selected based on the questions to be answered by the monitoring. When estimating the ecological and health related risks and exposure, it is relevant to collect especially top soil samples e.g. humus. If the aim is also to study contaminant transport and contamination risks of surface and ground water at the mine site, subsoil samples and sediment samples near aquatic environments are also needed. In addition, when comparing geogenic and anthropogenic sources of contaminants bedrock samples may be relevant. Hydrogeochemistry of the mine site and its surroundings should be characterised to examine the net results and impacts of the mining activity, industrial processes as well as geogenic emissions to the environment. Selection of background sampling points is critical, because the air emissions from a mine site may spread considerable distances (over 5 km in cases). Sampling points should be selected based on information on hydrogeology and groundwater flow directions at the site as well as bedrock mineralogy and fracture zones.

A list of the most common methods to be used in monitoring chemical stability at different areas within the influence area of a closed mine site.

1. Water sampling
2. Soil and sediment sampling
3. Field measurements
4. Dust

Table 1. Chemical stability checklist