Arsenic concentration in porewater of an alkaline coal ash disposal site: Roles of siderite precipitation/dissolution and soil cover

Kangjoo Kim, Sung Min Park, Jinsam Kim, Seok Hwi Kim, Yeongkyoo Kim, Jeong Tae Moon, Gab Soo Hwang, Wang Seog Cha

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The geochemical behavior of As in porewaters of an alkaline coal ash disposal site was investigated using multilevel samplers. The disposal site was in operation from 1983 until 1994 and was covered with 0.3-0.5 m thick soils in 2001 when this study was initiated. Sequential extraction analyses and batch leaching experiments were also performed using the coal ash samples collected from the disposal site. The results suggest the important roles of siderite (FeCO3) precipitation/dissolution and soil cover, which have been ignored previously. Arsenic levels in the porewater were very low (average of 10 μg L-1) when the site was covered with soil due to coprecipitation with siderite. The soil cover enabled the creation of anoxic conditions, which raised the Fe concentration by the reductive dissolution of Fe-(hydr)oxides. Because of the high alkalinity generated from the alkaline coal ash, even a small increase in the Fe concentration (0.66 mg L-1 on average) could cause siderite precipitation. When the soil cover was removed, however, an oxidizing condition was created and triggered the precipitation of dissolved Fe as (hydr)oxides. As a result, the dissolution of previously precipitated As-rich siderite caused higher As concentration in the porewater (average of 345 μg L-1).

Original languageEnglish
Pages (from-to)222-227
Number of pages6
JournalChemosphere
Volume77
Issue number2
DOIs
StatePublished - Sep 2009

Keywords

  • Alkaline coal ash
  • Alkalinity
  • Coal ash disposal site
  • Porewater
  • Siderite
  • Soil cover

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