Mobility of elements bound in river sediments affected by coal mining

Abstract

Trace elements are a natural part of the environment; however, anthropogenic activities can significantly contribute to their abundance and mobility in the environment. This study is focused on trace element mobility in sediments of a river system (the Bílina River, Czech Republic) affected by coal mining. It follows the previous research of trace element mobility in lignite from the Main Coal Seam in Bílina Quarry (Cahová et al. 2019). Eight samples of river sediment were taken along the Bílina River flow to evaluate the changes in As, Cr, Ni and V contents. Sequential extraction analysis modified according to Querol et al. (1996) and Feng et al. (2000) was used to determine the mobility of the studied elements under conditions close to natural. The amount of studied elements contained in each extract was determined by inductively coupled plasma mass spectrometry (ICP-MS). Water-extractable species of toxic elements may pose a risk to the environment due to their high mobility and bioavailability. It has been found that the release of compounds from the river sediment into the environment is conditioned by acidic conditions. While total metal contents in the river sediment ranges from tens to hundreds of μg/g, the amounts of metals extracted in each extraction step (deionised water and 1 M ammonium acetate at pH 5 and 7), typically reaches only tens to hundreds of ng/g, therefore the amount of easily mobilized elements is minimal. Mobilita prvků vázaných v říčních sedimentech ovlivněných těžbou uhlí