Miocene colored waters: A new significant source of thallium in the environment

•Colored Miocene waters are a newly discovered significant source of thallium.•Tl concentrations are higher than those for surface water by 2–3 orders of magnitude.•The majority of this thallium is entrapped in suspended solids.•Thallium concentration in SS exceeds ten times that in Zn–Pb ores and is alarming•Median of soluble Tl from colored waters is 10-times higher than in surface water

Thallium is a toxic non-essential element which is subject to some dispersion in the environment due to industrial activity and natural processes. There is a need for this dispersion to be monitored. Colored Miocene water seems to be a newly discovered significant source of such dispersion.The presence of colored water within the brown coal Miocene formation is related to the formation of organic sediments in that period which changed into layers of brown coal.The aim of this study was to investigate the concentration of Tl in colored waters, both in soluble form and entrapped in suspended solid matter (SS). Tl was determined by flow-injection differential-pulse anodic stripping voltammetry (FI-DP-ASV).It was found that Miocene colored waters from the Wielkopolska region contain very high Tl concentrations, and are thus a newly discovered significant source of Tl pollution in the environment. The concentrations are higher than the results for surface water by 2–3 orders of magnitude, and are a serious cause for concern. The majority of the total Tl in the colored waters is entrapped in suspended solids (more than 95% in the majority of samples). Even a low percentage of soluble Tl, however, creates a high concentration of the element in water (median 0.11 μg L− 1), which is approximately 10 times higher than in surface water from the River Warta. Tl concentration in SS is very high (median 15 μg g− 1) and exceeds by one order of magnitude the concentration of the element in crude Zn–Pb ores.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide