Impact of Oil Shale Opencast Mining and Combustion on Narva River and Its Tributaries: Chemical and Ecotoxicological Characterisation

Abstract

The influence of oil shale extraction in Narva opencast and combustion in Eesti and Balti power plants on the quality of surface waters and sediments of the Narva River left-bank tributaries was studied. Altogether, 22 sites were sampled for water and 21 for sediments. The concentrations of Cd, Pb, Cu and Cr in the surface water and sediment samples remained below the respective limit values for surface water and residential soils, respectively. Cd/Zn/Pb and Cr in the sediments were below the detection limits of the respective sensor bacteria (mg metal/kg sediment): <0.006 Cr 3+ ; <0.05 Cr 6+ ; <0.16 Zn 2+ ; <0.11 Cd 2+ ; <0.15 Pb 2+. As-specific sensor bacteria showed bioavailable sub-toxic levels of As in two sediments (up to 0.26 mg As 3+ /kg or, alternatively, up to 0.1 mg As 5+ /kg). Comparative ecotoxicity analysis of the suspensions and aqueous extracts of sediments using Vibrio fischeri kinetic luminescence inhibition test (Flash Assay) showed particle-bound acute toxicity in suspensions of four sediment samples out of 20 analysed. However, there was no acute toxicity of the respective aqueous extracts of sediments in the Flash Assay. The obtained results show the importance of combining both chemical and biological methods for environmental monitoring.

Leachability of Trace Elements From the Aged and Fresh Spent Shale Deposit – A Field Study

“…Oil shale, commonly defined as a fine-grained sedimentary rock containing significant amounts of organic matter, is widely distributed around the world [1]. Increased attention has been lately paid to the use of oil shale for oil and energy production, as well as related environmental problems [2][3][4][5][6].…”

“…The deposition of huge amounts of spent shale may affect the surrounding environment due to the leaching of harmful constituents, including potentially hazardous trace elements [3,8,13]. Coupled hydrological, geochemical and biological processes may influence the fate and transport of pollutants in the disposal site [6,9,14,15]. The extent of contribution depends on the properties of wastes and field conditions.…”