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This article was downloaded by: [University of Leeds] On: 31 August 2012, At: 08:19 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Geomicrobiology Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ugmb20 Biogeochemical Reduction Processes in a Hyper- Alkaline Leachate Affected Soil Profile Ian T. Burke a , Robert J. G. Mortimer a , Shanmugam Palaniyandi b c , Robert A. Whittleston a , Cindy L. Lockwood a , David J. Ashley a & Douglas I. Stewart b a Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom b School of Civil Engineering, University of Leeds, Leeds, United Kingdom c Central Leather Research Institute (CSIR), Adyar, Chennai, India Accepted author version posted online: 06 Apr 2012. Version of record first published: 30 Aug 2012 To cite this article: Ian T. Burke, Robert J. G. Mortimer, Shanmugam Palaniyandi, Robert A. Whittleston, Cindy L. Lockwood, David J. Ashley & Douglas I. Stewart (2012): Biogeochemical Reduction Processes in a Hyper-Alkaline Leachate Affected Soil Profile, Geomicrobiology Journal, 29:9, 769-779 To link to this article: http://dx.doi.org/10.1080/01490451.2011.619638 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Geomicrobiology Journal, 29:769–779, 2012 Copyright © Taylor & Francis Group, LLC ISSN: 0149-0451 print / 1521-0529 online DOI: 10.1080/01490451.2011.619638 Biogeochemical Reduction Processes in a Hyper-Alkaline Leachate Affected Soil Profile Ian T. Burke,1 Robert J. G. Mortimer,1 Shanmugam Palaniyandi,2 Robert A. Whittleston,1 Cindy L. Lockwood,1 David J. Ashley,1 and Douglas I. Stewart2 1Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom 2School of Civil Engineering, University of Leeds, Leeds, United Kingdom seeps, deep mine waters (Brazelton et al. 2010; McMillan et al. Hyperalkaline surface environments can occur naturally or be- 2009; Pollock et al. 2007; Takai et al. 2001; 2005), but many are cause of contamination by hydroxide-rich wastes. The high pH also due to human activities. These anthropogenic sites occur produced in these areas has the potential to lead to highly special- as a result of the presence of residues from a range of industrial ized microbial communities and unusual biogeochemical processes. processes, e.g., lime production waste, steelworks slags, coal This article reports an investigation into the geochemical processes that are occurring in a buried, saturated, organic-rich soil layer combustion residues, Solvay process waste, chromite ore at pH 12.3. The soil has been trapped beneath calcite precipitate processing residues, bauxite processing wastes, borax wastes (tufa) that is accumulating where highly alkaline leachate from and cementitious construction wastes (Carlson and Adriano a lime kiln waste tip is emerging to atmosphere. A population of 1993; Deakin et al. 2001; Effler et al. 1991; Hartland et al. 2009; anaerobic alkaliphilic bacteria dominated by a single, unidentified Mayes et al. 2006; 2008; 2011; Townsend et al. 1999; Ye et al. species within the Comamonadaceae family of β-proteobacteria has established itself near the top of the soil layer. This bacterial pop- 2004). Weathering of these wastes typically produces highly ulation appears to be capable of nitrate reduction using electron alkaline leachate (pH 10–13) due to the ubiquitous presence donors derived from the soil organic matter. Below the zone of ni- of Ca, Na and K oxides (primarily CaO) that hydrolyze in trate reduction a significant proportion of the 0.5N HCl extractable natural waters to produce soluble metal hydroxides. As these iron (a proxy for microbial available iron) is in the Fe(II) oxidation wastes are often a legacy from times when disposal was poorly state, indicating there is increasing anoxia with depth and sug- gesting that microbial iron reduction is occurring. Supplemental controlled, alkaline leachate emanating from such wastes can materials are available for this article. Go to the publisher’s online contaminate any groundwater resources beneath disposal sites edition of Geomicrobiology Journal to view the free supplemental (Hartland et al. 2009; Stewart et al. 2010). files. The trace metal composition of these leachates varies greatly with the composition of individual wastes but elevated concen- Keywords anaerobe, alkaliphile, bacteria, contaminated land, iron- trations of contaminant trace metals and metalloids such as As, reduction, nitrate-reduction, microbial-reduction Downloaded by [University of Leeds] at 08:19 31 August 2012 Pb, V and Cr are commonly reported (Chaurand et al. 2007; Mayes et al. 2009; Stewart et al. 2007). In addition, due to the leaching of sulphur bearing minerals, elevated sulphate concen- INTRODUCTION trations are often reported to affect overall water quality (Mayes There are many different environments that occur both on et al. 2008; Schwab et al. 2006; Whittleston et al. 2010). When and in the Earth that are characterized by high pH. Some are en- Ca concentrations are not limiting, the alkaline leachate reacts tirely natural, e.g., soda lakes, hot springs, oceanographic cold rapidly with atmospheric CO2 where it emerges into sub-aerial environments, sometimes producing very high rates of calcite precipitation (Deakin et al. 2001; Hartland et al. 2009). This has Received 5 July 2011; accepted 18 August 2011. a detrimental impact on surface environments due to the build Current affiliation for Shanmugam Palaniyandi: Central Leather Research Institute (CSIR), Adyar, Chennai, India. up of tufa deposits that smother natural vegetation and benthic The authors would like to thank Martin Pedley and Mike Rogerson organisms (Effler et al. 1991). As disposal sites rarely have im- for introducing us to the site and Juan Diego Rodriguez-Blanco for permeable barriers underneath the waste, the fate of the alkaline organising XRD and XRF analysis. leachate, and particularly any contaminants within that leachate, Address correspondence to Douglas I. Stewart, School of Civil depends solely on biogeochemical interactions with soils and Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom. E-mail: [email protected] sediments present beneath or adjacent to waste disposal sites. 769 770 I.T.BURKEETAL. TABLE 1 Microbially significant half-reaction reduction potentials: Standard reduction potential, E0, and redox potential, Eh, at pH 12 (at 25◦C and atmospheric pressure) Eh @ pH 7 Eh @ pH 12 Transformation Reaction E0 (V) (V) (V) Assumptions + + − O2 depletion O2 + 4H + 4e = 2H201.230 0.816 0.510 PO2 = 0.2 bar + − + + + − = . − = − Nitrate reduction to nitrite NO3 2H 2e 0 845 0 431 0 135 [NO3 ] [NO2 ] − + NO2 H2O − + + + − = . − . − = µ −1 Nitrite reduction to nitric NO2 2H e 1 192 0 484 0 106 [NO2 ] 100 mol L $ −6 oxide NO + H2O PNO = 10 bar + + + − = 1 . = = −6 Nitric oxide reduction to NO H e 2 N2O 1 588 0 996 0 700 PNO PN2O 10 bar nitrous oxide$ + 1 2 H2O 1 + + + − = 1 . = −6 = Nitrous oxide reduction to 2 N2O H e 2 N2 1 769 1 180 0 884 PN2O 10 bar PN2 $ 1 nitrogen + H2O 0.8 bar ∗ 2 + Mn reduction Mn(III) to Mn3O4 + 2H + 2H2O 0.480 0.066 −0.230 — − Mn(II) + 2e = 3Mn(OH)2 + + − −1 Fe reduction Fe(III) to Fe(II) Fe(OH)3 + 3H + e 0.975 0.014 −0.453 [Fe2+] = 18 µmol L 2+ = Fe + 3H2O ∗ − + + + − . − . − . − = − Fe reduction Fe(III) to Fe(II) Fe(OH)4 H e 0 308 0 106 0 402 [Fe(OH)4 ] [Fe(OH)3 ] = − + Fe(OH)3 H2O + 2− + + + − . − . − . 2− = Sulfate reduction S(VI) to SO4 10H 8e 0 301 0 217 0 587 [SO4 ] [H2S] S(-II) = H2S + 4H2O × 2− + + + − . − . − . − = − = Carbonate reduction C(VI) 2CO3 11H 8e 0 340 0 292 0 648 [CO3 ] [CH3COO ] − −1 to C(0) = CH3COO + 4H2O 20 mmol L +after Langmuir (1997). ∗calculated using thermodynamic data from Stumm and Morgan (1996) ×calculated using thermodynamic data from Thauer (1977). $calculated using thermodynamic data from Latimer (1952). The ability of indigenous soil microorganisms to couple or- energize solute uptake and motility (Detkova and Pusheva 2006; ganic matter oxidation to the reduction of soluble oxyanions Krulwich et al. 2001). such as nitrate and sulphate, and transition metals such as iron Alkaliphiles are commonly divided into two broad groups; and manganese, is well documented (Lovley 1993; 1997; Lov- those that grow from circum-neutral to alkaline conditions are ley et al. 2004; Tebo and Obraztsova 1998). Where sufficient classified as facultative alkaliphiles (Sturr et al. 1994), however, organic matter is available for oxidation, progressively more those that only growth at around pH 9 or above are classified Downloaded by [University of Leeds] at 08:19 31 August 2012 anoxic conditions develop and a cascade of terminal-electron- as obligate alkaliphiles (McMillan et al. 2009). Although for all accepting processes occur in sequence (but dependent on the alkaliphiles optimum growth commonly occurs at around pH availability of electron acceptors), with either increasing in- 9–10, some species are reported to continue to grow up to around cubation time (Burke et al.