Evaluation of Environmental Impacts of the Figueira Coal-Fired Power Plant, Paraná, Brazil

Abstract

The present study investigates the petrographical and chemical characteristics of the feedcoal used in the coal-fired Figueira Power Plant, Paraná, Brazil, and the chemical characteristics of fly and bottom ashes generated in the combustion process. Chemical characteristics of soils, water and plants collected in the proximity (250 to 5000 m) of the power plant were also studied in order to determine if there exist any contamination caused by emissions of the power plant. The feedcoal is of high volatile C/B rank. Mean ash content is 30.3 wt% and the mean sulphur content is 4.3 wt%. Trace element concentrations > 500 mg·kg−1 include Zn and As, trace elements > 100 mg·kg−1 include Mn, B, Pb and Sn, and trace elements > 50 mg·kg−1 include Cr, U, V. For fly and bottom ashes the highest trace element concentrations were recorded for Zn, As, Mn, Sn and B, with most trace element enriched in the fly ashes. In the soil samples the mean values of the trace elements are highly variable ranging from < 1 mg·kg−1 for elements such as Cd, Sb, Se and Tl to concentrations > 20 mg·kg−1 for elements such as B, Cr, Mn, V and Zn. At 5 sample locations out of 38 As concentrations were found to exceed the upper limits considered by the Brazilian Environmental Agency, and at one point each Co and Sb was found to be elevated. The saturated hydrocarbon fraction in the soils suggest an origin from terrestrial plants by the predominance of C27, C29 and C31 n-alkanes. Enrichment of PAHs were determined at sample locations near the power plant, with PAH ratios suggesting an origin both of petroleum and coal combustion. Analyses of the surface water showed sulfate concentrations well within the range reported for fresh water, with pH values indicative of neutral conditions for most samples. At one locality very high sulfate concentrations, along with a low pH value and enrichment in a number of trace elements (B, Be, Cd, Co, Li, Mn, Ni, Tl, U and Zn) were observed. It is suggested that these unusual concentrations are related to the proximity of the sample location to an abandoned coal mine. The saturated hydrocarbons determined in the water samles indicate a contribution of terrestrial plants by the predominant C27, C29 and C31 n-alkanes, whereas most PAHs where below the detection limit. Trace element concentrations in the Fern and Arrow Leave samples taken at locations of the prevailing southerly wind direction show for a number of elements (As, B, Pb, U, Zn) increasing values at sample sites near the power plant. One extraordinary high concentration of As (5248 mg kg−1) was determined in a fern sample, which also showed a relatively high Se value. It is suggested that the high As and Se concentrations are not related to emissions from the power plant, but rather reflect the proximity of the sample location to mine waste areas of the operating nearby coal mine. Enrichment of certain elements such as Zn and As found in soil and plant samples and the occurrence of some PAHs at locations near the power plant, suggest a contribution from emissions by the power plant. However, most trace element concentrations do not exceed the upper limits as indicated by the Brazilian Environmental Agency and PAH ratios suggest for many samples an origin of petroleum (incomplete fuel burning by motor vehicles) rather than coal combustion. Enrichment of trace elements and sulfate concentration in soil and water samples observed at a limited number of sample locations may be related to other anthropogenic sources such as abandoned coal mine sites and mine waste areas of operating coal mines.