Processes of iron and manganese retention in laboratory peat microcosms subjected to acid mine drainage
- Villanova Univ., PA (USA)
The present study was conducted to evaluate the processes responsible for Fe and Mn retention in peat and the effects of microbial activity, pH, temperature, and metal concentration in acid mine drainage (AMD) on these processes. Experimental units consisted in 30 g of fresh Sphagnum peat, which was repeatedly flushed with synthetic AMD at pH 3.5. Of the four major processes of metal cation retention in peat, Fe oxidation and Fe binding on peat organics were predominant, with Fe oxides and organically bound Fe making up, respectively 62 and 22% of the total Fe in the peat at the end of the experiment. Whereas Fe complexation was a finite process, reaching saturation at 12 mg Fe g{sup {minus}1} dry peat, Fe-oxide concentration in peat increased steadily throughout the experiment. At pH 3.5, Fe-oxide precipitation was depressed by the addition of an antiseptic to AMD, suggesting that the process was microbially mediated. Iron oxide precipitation was higher at pH 5.5 than 3.5 and less depressed at pH 5.5 than 3.5 by the presence of formaldehyde in AMD. The efficiency of peat to remove Fe from AMD was diminished at low temperature and high Fe concentration in AMD. Manganese retention in peat was small compared with that of Fe, and Mn was retained in peat almost exclusively as exchangeable Mn{sup 2+}. Retention of Fe{sup 2+} in peat was not affected by the presence of Mn{sup 2+} in AMD. Iron oxides that had accumulated in peat subjected to AMD were not readily resolubilized by any of three processes investigated: photoreduction, microbial Fe(III) reduction under reducing conditions, and exposure to simulated acid precipitation. These findings suggest that constructed wetlands may be an appropriate technology to remove Fe from AMD with low soluble Fe concentration, but are inadequate for treating drainage waters rich in soluble Mn.
- OSTI ID:
- 6349263
- Journal Information:
- Journal of Environmental Quality; (USA), Journal Name: Journal of Environmental Quality; (USA) Vol. 19:2; ISSN JEVQA; ISSN 0047-2425
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010800* -- Coal
Lignite
& Peat-- Waste Management
ACID MINE DRAINAGE
AQUATIC ECOSYSTEMS
BIOLOGICAL ACCUMULATION
CATIONS
CHARGED PARTICLES
COAL MINES
ECOSYSTEMS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
IONS
IRON
MANAGEMENT
MANGANESE
METALS
MICROCOSMS
MICROORGANISMS
MINES
ORGANIC MATTER
PEAT
RETENTION
TRANSITION ELEMENTS
UNDERGROUND FACILITIES
USES
WASTE MANAGEMENT
WETLANDS