Rare earth and trace element signatures for assessing an impact of rock mining and processing on the environment: WiA > niwka case study, south-central Poland

摘要

A detailed hydrogeochemical study was performed in the WiA > niwka mining area (south-central Poland). This covered three acid pit bodies, historic tailings acid ponds, acid pools, and additionally two neighboring rivers. All these acid mine drainage (AMD) waters are characterized by the pH in the range of 1.7 (pools) to 3.5 (tailings ponds). The most interesting is the PodwiA > niwka acid pit lake that shows a very low pH (2.2-2.5) and very high concentrations of SO4 (2-) (2720-5460 mg/L), Fe (545-1140 mg/L), Al (86.2 mg/L), As (9603-24,883 mu g/L), Co (1317-3458 mu g/L), Cr (753-2047 mu g/L), Cu (6307-18,879 mu g/L), Ni (1168-3127 mu g/L), and rare earth element (REE) (589-1341 mu g/L). In addition, seeps that drain the PodwiA > niwka mine tailings and partly aggregate piles form strong acid pools in the mining area. Along with these pools, in which As and REE contents reach 369,726 and 6288 mu g/L, respectively, these waters are among the most distinctive As- and REE-rich AMD surface waters across the world. It is noteworthy that the PodwiA > niwka acid pit lake and WiA > niwka DuA 1/4a acid pit sump exhibit different element signatures and REE concentration patterns normalized to North American Composite Shale (NASC): the PodwiA > niwka acid pit lake always shows a characteristic roof-shaped medium REE (MREE) profile with distinct enrichments in Gd, Eu, and Tb whereas the other one displays a step-shaped heavy REE (HREE) profile with positive Tb and Gd anomalies. The REE undergo fractionation during weathering and the subsequent leaching of dissolved and suspended fractions from rocks to acid water bodies where these and other elements are further fractionated by geochemical processes. This study shows that the individual REE have greater affinities for Mn, HREE for Fe and SO4 (2-), and only La and Ce for Al. This specific water geochemistry has enabled us to (i) pinpoint the location of AMD "hot spots" originated from quartzite mining and processing operations conducted by current and previous mining companies, (ii) predict the directions and effects of future strip mining for quartzites in the WiA > niwka DuA 1/4a and PodwiA > niwka open pits, and (iii) evaluate the potential impact of mining and processing effluents on the quality of rivers.