Radium balance in discharge waters from coal mines in Poland the ecological impact of underground water treatment

Abstract

Abstract. Saline waters from underground coal mines in Poland often contain natural radioactive isotopes, mainly 226 Ra from the uranium decay series and 228 Ra from the thorium series. More than 70% of the total amount of radium remains underground as radioactive deposits due to spontaneous co-precipitation or water treatment technologies, but several tens of MBq of 226 Ra and even higher activity of 228 Ra are released daily into the rivers along with the other mine effluents from all Polish coal mines. Mine waters can have a severe impact on the natural environment, mainly due to its salinity. Additionally high levels of radium concentration in river waters, bottom sediments and vegetation were also observed. Sometimes radium concentrations in rivers exceeded 0.7 kBq/m 3 , which was the permitted level for waste waters under Polish law. The investigations described here were carried out for all coal mines and on this basis the total radium balance in effluents has been calculated. Measurements in the vicinity of mine settling ponds and in rivers have given us an opportunity to study radium behaviour in river waters and to assess the degree of contamination. For removal of radium from saline waters a method of purification has been developed and implemented in full technical scale in two of Polish coal mines. The purification station in Piast Colliery was unique, the first underground installation for the removal of radium isotopes from saline waters. Very good results have been achieved -approximately 6 m 3 /min of radium-bearing waters were treated there, more than 100 MBq of 226 Ra and 228 Ra remained underground each day. Purification has been started in 1999, therefore a lot of experiences have been gathered during this period. Since year 2006, a new purification station is working in another colliery, Ziemowit, at the level -650 meters. Barium chloride is used as a cleaning agent, and amount of water to be purified is reaching 9 m 3 /min. Technical measures such as inducing the precipitation of radium in gobs, decreasing the amount of meteoric inflow water into underground workings etc., have been undertaken in several coal mines, and as a result of these measures the total amount of radium released to the surface waters is much has diminished significantly during the last 15 years.

Radon problems in mining and post-mining areas in Upper Silesia region, Poland

“…Some of the ponds are excluded from use, dried and reclaimed because of the fact that the former mining areas are transferred to local communities. Results of measurements of radon exhalation rates carried out within the borders of abandoned settling ponds and in their close vicinity varied from 2.0 mBq·m 2 ·s −1 up to more than 400 mBq·m 2 ·s −1 , which was the highest value measured in the USCB [27].…”

“…Many of the mines are connected by a complex system of galleries and cessation and dewatering of closed ones is not possible. Because of the continuing dewatering of closed collieries, the several tens of megabecquerel of 226 Ra and even higher activity of 228 Ra are still released daily into the settling ponds and rivers [27]. In Upper Silesia, there are currently more than 20 settling ponds in use, numerous of them containing waters and bottom sediments with enhanced concentration of radium isotopes.…”

“…The total dissolved concentration is usually about 100 kg/m 3 but may be as high as 220 kg/m 3 [26]. Importantly, Silesian mining brines contain elevated concentrations of radium isotopes, 226 Ra and 228 Ra [27]. Considerable concentrations of radium are found at the surface, especially in settling ponds.…”

Influence of Dose Conversions, Equilibrium Factors, and Unattached Fractions on Radon Risk Assessment in Operating and Show Underground Mines

“…Further studies conducted in later years on the phenomenon of natural radioactivity in coal mines helped identify additional sources of natural ionising radiation in these mines. It turned out that the primary sources of natural ionising radiation in mines are waters containing radium isotopes, precipitates from these waters, and short-lived radon decay products [ 3 , 4 , 5 , 6 , 7 ]. These problems are not only the domain of Polish coal mines.…”

Application of zeolites for radium removal from mine water

“…From type A waters, radium and barium always co-precipitate as sulfates, when mixed with any water containing sulfate ions. As a result of the precipitation, barium sulfate deposits with highly enhanced radium concentrations are formed (Lebecka et al 1985 ; Lebecka et al 1994 ; Michalik et al 2002 ; Chałupnik and Wysocka 2009 ). The total activity of radium isotopes in these sediments may sometimes reach 400 kBq/kg, while the average radium content in soil is 25 Bq/kg (UNSCEAR 2000 ).…”