Selected harmful elements in polish lignite

Lignite from Polish deposits includes numerous rare elements, trace elements and dispersed elements, some of which may have a negative impact on the environment and human health. However, these elements usually do not reach harmful concentration within analyzed coal. This study examined the content of selected elements harmful at each concentration, and elements harmful at higher concentrations. The analysis included the samples of lignite and ash produced during the combustion of coal. Elements toxic at each concentration included: Pb, Hg, Cd, Be and As, while elements toxic at higher concentrations were: Zn, Se, Sb, Cu and Mn. Trace elements were determined though the use of instrumental neutron activation analysis (INAA), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Due to the lack of standards defining the permissible content of harmful elements in lignite, the examination was based on a comparison of the observed content with acceptable daily intake for humans and maximum permissible levels of these elements in soils and waters. Within the tested lignite, Hg, Pb, As and Cd content is low, while their concentration reaches a maximum of up to 2.6 ppm Hg, 26.22 ppm Pb, 19.72 ppm As and 17.76 ppm Cd. These concentrations are very small compared to the maximum permissible levels in soils. The exception is the average mercury content in the “Adamów” lignite deposit. The content of toxic elements in ash is higher than in the raw coal, suggesting that they are related to the mineral matter of coal. At the same time elements like Mn, Pb and Cu have low volatility, which is responsible for their concentration in the ash after combustion of coal. On the other hand, elements like Cd and Hg evaporate during combustion together with flue gas due to their high volatility, and therefore their content in ash is lower than their content in coal. The content of other trace elements (Sb, Zn, Mn and Cu) is also low in lignite and does not pose a threat to the environment.