Site overview
The Upper Silesian Coal Basin (USCB) is located in the Silesian Upland in southern Poland. The Silesian Upland is a plateau between 200 and 300 m above sea level, divided into distinct ridges by river valleys. The USCB area is affected by long term industrial activity that began in 12th century with silver mining which was followed later by lead and zinc ore exploitation. Since the turn of the 18th and 19th centuries underground coal mining, ironworks and coal fired power plants have left an imprint on the local environment.
Currently, fossil fuel and mining industries in Europe are reducing. However, within the USCB area about 30 underground coal mines are still in operation. From an environmental perspective, one of the most important sources of contamination within the USCB area is from ‘formation water’ pumped from underground mines into surface retention ponds. The daily discharge of mine waters into these ponds exceeds 400,000 m3. This volume has not significantly decreased even though many mines have closed as water must be still pumped to the surface to protect neighbouring mines from flooding.
Why is the USCB a radioecological observatory?
Sulphate, chloride, suspended matter, heavy metals, and radium isotopes present in mine waters pumped to the surface lead to a mixed contaminant situation. To control the discharge of sulphates and chlorides into inland water the pumped mine water is stored in retention ponds before direct discharge into rivers. Pollutants accumulate in the bottom sediments of these ponds. In the USCB area there are about 25 settling ponds currently in use which contain in total up to 5,000,000 m3 of sediment; some ponds contain enhanced levels of radium isotopes and heavy metals.
Usually, the natural uranium and thorium decay series are not fully represented in the bottom sediments and start with Ra-226 and Ra-228, respectively. Hence, the most important radionuclides are radium isotopes Ra-228 and Ra-226 as well as their long-lived decay products Th-228, Rn-222, Pb-210 and Po-210. Radium activity concentrations in the sediments are up to 200 kBq kg-1 for Ra-226 and up to 150 kBq kg-1 for Ra-228, however as Ra-228 is not supported by its parent radionuclide its activity concentration in sediment decreases noticeably over time.
Highly mineralised formation water is also the source of heavy metal contamination. Heavy metal concentrations in sediments of settling ponds of 10 different coal mines reach 122,000 ppm for Ba, 830 ppm for Pb, 760 ppm for Zn and 270 ppm for Cu. Despite the high mineralisation the saline mine waters are often used for technological purposes, resulting in additional contamination with hydrocarbons used as engine oil and lubricants.
The Radioecological Observatory in the USCB comprises many sites all within 60 km of Katowice, they comprise flowing, semi-stagnant and stagnant waters as well as terrestrial ecosystems affected by mine sediments. All sites are located close to active mine water discharge points.