Speciation of mercury in flue gas from Australian coal fired power stations

Mercury is a potentially toxic trace metal. Mercury exists naturally in coal in very low concentrations, having been incorporated during the coalification process. Consequently, coal fired power stations are a major anthropogenic source of mercury due to the large quantity of coal utilised for electricity generation. In the environment, mercury transforms into methylmercury, a potential neurotoxin, and bioaccumulates in aquatic biota and subsequently enters the food chain. The environmental fate and success in retention of mercury depends on its different physicochemical forms and oxidation states known as speciation. In this work speciation of mercury was conducted at four different coal power stations across Australia (2 in NSW, 1 in WA and 1 in Qld) by the Ontario hydro sampling and analysis method. Total mercury was also analysed in feed coal, bottom ash and fly ash in order to confirm volatile behaviour of mercury under combustion conditions. In flue gas, it was found that the concentration of total mercury was in the range of 0.5 to 2.67 µg/Nm3. Hg(0) was the dominant form while Hg(P) was the lowest in concentrations. Results from this study are compared with previous work and discussed.