Report # 109898

P.I.  Lena Ma, UF

Coal combustion residuals (CCRs) contain variable amounts of trace metals which can potentially negatively impact the environment under certain conditions.  We analyzed metal concentrations in 8 CCRs from five coal-fired power plants in Florida. The objective was to assess the leaching behavior of 7 metals (As, Ba, Cd, Cr, Hg, Pb, and Se) in CCR samples using LEAF Methods 1313 and 1316. The objectives were: (1) assess the leachability of As, Ba, Cd, Cr, Hg, Pb, and Se under a broad range of pH conditions using LEAF Method 1313 (2, 4, 5.5, 7, 8, 9, 10.5, 12, and 13); (2) evaluate how the liquid-solid ratio affects leaching of As, Ba, Cd, Cr, Hg, Pb, and Se using LEAF method 1316 (0.5, 1, 2, 5 and 10); and (3) compare the results to those obtained through Synthetic Precipitation Leaching Procedure (SPLP). Most of the metals showed amphoteric behavior presenting higher leaching at very low and high pH when LEAF Method 1313 was used. However, cadmium (Cd) and mercury (Hg) were exceptions. For Hg, leaching was not observed in most samples, and for Cd, leaching decreased at pH higher than 7, with the highest leaching observed at pH 2 and 4. SPLP results were highly variable when compared to the LEAF data.  Barium (Ba) was the only element that did not exceed its corresponding Florida Groundwater Cleanup Target Level (FGWCTL) at all pH levels. Elemental leaching was low at pH range of 4 to 9, which is the typical pH range of soils in Florida. Due to potential leachability of some trace metals, beneficial use applications of CCRs may need additional evaluation in certain circumstances where soil pH conditions are outside the typical pH range of soils in Florida.


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