Name: experimental column setup for studying anaerobic biogeochemical interactions between iron (oxy)hydroxides, trace elements, and bacteria
Uploaded: 2017-12-19T12:30:00
Description: Watch this Scientific Journal Video about Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron OxyHydroxides, Trace Elements, and Bacteria at JoVE.com

Dette arbeidet var delfinansiert av BRGM, en postdoktor stipend fra Conseil Général du Loiret og Carnot Institute. Vi erkjenner også takknemlig økonomisk støtte fra PIVOTS prosjektet Région sentrum - Val de Loire.

1. eksperimentelle forberedelse
<ol>
	<li>Acid-Wash alle materialer (glass, polytetrafluoroethylene (PFTE)) i kontakt med prøver (5 dager i 20% salpetersyre (HNO3) v/v) etterfulgt av fem dager i saltsyre (HCl) 10% v/v). Skyll flere ganger med svært rent vann og tørr under en laminær strømning hette før bruk.</li>
	<li>Bruker polyetylen hansker (eller lignende) og avtrekksvifte for alle trinn som involverer kjemikalier.</li>
</ol>
2. Forbered Hg og som piggete amorfe jernoksid
...

<ol>
	<li>Oremland, R. S., Stolz, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Ecology+of+Arsenic.">The Ecology of Arsenic.</a> Science. 300 (5621), 939 (2003).</li><li>Silver, S., Phung, L. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genes+and+enzymes+involved+in+bacterial+oxidation+and+reduction+of+inorganic+arsenic.">Genes and enzymes involved in bacterial oxidation and reduction of inorganic arsenic.</a> Appl Environ Microbiol. 71 (2), 599-608 (2005).</li><li>Compeau, G. C., Bartha, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfate-Reducing+Bacteria:+Principal+Methylators+of+Mercury+in+Anoxic+Estuarine+Sediment.">Sulfate-Reducing Bacteria: Principal Methylators of Mercury in Anoxic Estuarine Sediment.</a> Appl. Environ. Microbiol. 50, (1985).</li><li>Fleming, E. J., Mack, E. E., Green, P. G., Nelson, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mercury+Methylation+from+Unexpected+Sources:+Molybdate-Inhibited+Freshwater+Sediments+and+an+Iron-Reducing+Bacterium.">Mercury Methylation from Unexpected Sources: Molybdate-Inhibited Freshwater Sediments and an Iron-Reducing Bacterium.</a> Appl. Environ. Microbiol. 72 (1), 457-464 (2006).</li><li>Barkay, T., Miller, S., Summers, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+mercury+resistance+from+atoms+to+ecosystems.">Bacterial mercury resistance from atoms to ecosystems.</a> FEMS Microbiol Rev. 27 (2-3), 355-384 (2003).</li><li>Dixit, S., Hering, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+arsenic(V)+and+arsenic(III)+sorption+onto+iron+oxide+minerals:+Implications+for+arsenic+mobility.">Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: Implications for arsenic mobility.</a> Environ. Sci. Technol. 37, (2003).</li><li>Andersson, H. A., Nriagu, J. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Biochemistry of Mercury in the Environnment. , 79-112 (1979).</li><li>Khwaja, A., Bloom, P. R., Brezonik, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Binding+Constants+of+Divalent+Mercury+in+Soil+Humic+Acids+and+Soil+Organic.">Binding Constants of Divalent Mercury in Soil Humic Acids and Soil Organic.</a> Environ. Sci. Technol. 40, (2006).</li><li>Neculita, C. M., Zagury, G. J., Deschenes, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mercury+Speciation+in+Highly+Contaminated+Soils+from+Chlor-Alkali+Plants+Using+Chemical+Extractions.">Mercury Speciation in Highly Contaminated Soils from Chlor-Alkali Plants Using Chemical Extractions.</a> J Environ Qual. 34 (1), (2005).</li><li>Schuster, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+behaviour+of+mercury+in+the+soil+with+special+emphasis+on+complexation+and+adsorption+processes+-+a+review+of+the+literature.">The behaviour of mercury in the soil with special emphasis on complexation and adsorption processes - a review of the literature.</a> Water Air Soil pollut. 56 (56), 667-680 (1991).</li><li>Wallschl&#228;ger, D., Desai, M. V. M., Spengler, M., Windm&#246;ller, C. C., Wilken, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+humic+substances+dominate+mercury+geochemistry+in+contaminated+floodplain+soils+and+sediments.">How humic substances dominate mercury geochemistry in contaminated floodplain soils and sediments.</a> J. Environ. Qual. 27 (5), (1998).</li><li>Lovley, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissimilatory+Fe(III)+and+Mn(IV)+reduction.">Dissimilatory Fe(III) and Mn(IV) reduction.</a> Microbiol. Mol. Biol. Rev. 55 (2), 259-287 (1991).</li><li>Lovley, D. R., Kashefi, K., Vargas, M., Tor, J. M., Blunt-Harris, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+humic+substances+and+Fe(III)+by+hyperthermophilic+microorganisms.">Reduction of humic substances and Fe(III) by hyperthermophilic microorganisms.</a> Chem. Geol. 169 (3-4), 289-298 (2000).</li><li>Hansel, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+constraints+of+ferric+(hydr)oxides+on+dissimilatory+iron+reduction+and+the+fate+of+Fe(II).">Structural constraints of ferric (hydr)oxides on dissimilatory iron reduction and the fate of Fe(II).</a> Geochimica Cosmochimica Acta. 68, 3217-3229 (2004).</li><li>Thamdrup, B., Fossing, H., J&#248;rgensen, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manganese,+iron+and+sulfur+cycling+in+a+coastal+marine+sediment+Aarhus+bay,+Denmark.">Manganese, iron and sulfur cycling in a coastal marine sediment Aarhus bay, Denmark.</a> Geochim.Cosmochim. Acta. 58 (23), 5115-5129 (1994).</li><li>Planer-Friedrich, B., London, J., McCleskey, R. B., Nordstrom, D. K., Wallschl&#228;ger, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thioarsenates+in+Geothermal+Waters+of+Yellowstone+National+Park:+Determination,+Preservation,+and+Geochemical.">Thioarsenates in Geothermal Waters of Yellowstone National Park: Determination, Preservation, and Geochemical.</a> Environ. Sci. Technol. 41 (15), 5245-5251 (2007).</li><li>Burnol, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decoupling+of+arsenic+and+iron+release+from+ferrihydrite+suspension+under+reducing+conditions:+a+biogeochemical+model.">Decoupling of arsenic and iron release from ferrihydrite suspension under reducing conditions: a biogeochemical model.</a> Geochem. Trans. 8 (1), 12 (2007).</li><li>Kocar, B. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrated+biogeochemical+and+hydrologic+processes+driving+arsenic+release+from+shallow+sediments+to+groundwaters+of+the+Mekong+delta.">Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong delta.</a> Appl. Geochem. 23 (11), (2008).</li><li>Harris-Hellal, J., Grimaldi, M., Garnier-Zarli, E., Bousserrhine, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mercury+mobilization+by+chemical+and+microbial+iron+oxide+reduction+in+soils+of+French+Guyana.">Mercury mobilization by chemical and microbial iron oxide reduction in soils of French Guyana.</a> Biogeochem. 103 (1), (2011).</li><li>Islam, F. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+metal-reducing+bacteria+in+arsenic+release+from+Bengal+delta+sediments.">Role of metal-reducing bacteria in arsenic release from Bengal delta sediments.</a> Nature. 430, (2004).</li><li>Schultz-Zunkel, C., Rinklebe, J., Bork, H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trace+element+release+patterns+from+three+floodplain+soils+under+simulated+oxidized-reduced+cycles.">Trace element release patterns from three floodplain soils under simulated oxidized-reduced cycles.</a> Ecol. Eng. 83, 485-495 (2015).</li><li>Nickson, R. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+arsenic+release+to+groundwater,+bangladesh+and+West+Bengal.">Mechanisms of arsenic release to groundwater, bangladesh and West Bengal.</a> App. Geochem. 15, 403-413 (2000).</li><li>Varsanyi, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arsenic,+iron+and+organic+matter+in+sediments+and+groundwater+in+the+Pannonian+basin,+Hungary.">Arsenic, iron and organic matter in sediments and groundwater in the Pannonian basin, Hungary.</a> App. Geochem. 21, 949-963 (2006).</li><li>Hellal, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mercury+mobilization+and+speciation+linked+to+bacterial+iron+oxide+and+sulfate+reduction:+A+column+study+to+mimic+reactive+transfer+in+an+anoxic+aquifer.">Mercury mobilization and speciation linked to bacterial iron oxide and sulfate reduction: A column study to mimic reactive transfer in an anoxic aquifer.</a> J. Contam. Hydrol. 180, 56-68 (2015).</li><li>Battaglia-Brunet, F., Dictor, M. C., Garrido, F., Crouzet, C., Morin, D., Dekeyser, K., Clarens, M., Baranger, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+arsenic(III)-oxidizing+bacterial+population:+selection,+characterization,+and+performance+in+reactors.">An arsenic(III)-oxidizing bacterial population: selection, characterization, and performance in reactors.</a> J Appl. Microbiol. 93 (2002), 656-667 (2002).</li><li>Salvato, N., Pirola, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+mercury+traces+by+means+of+solid+sample+atomic+absorption+spectrometry.">Analysis of mercury traces by means of solid sample atomic absorption spectrometry.</a> Microchim Acta. 123 (1), 63-71 (1996).</li><li>Huguet, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Caract&#233;risation biog&#233;ochimique et potentiel de m&#233;thylation du mercure de biofilms en milieu tropical (retenue de Petit Saut et estuaire du Sinnamary, Guyane Fran&#231;aise). . , (2009).</li><li>Mamindy-Pajany, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arsenic+in+Marina+Sediments+from+the+Mediterranean+Coast:+Speciation+in+the+Solid+Phase+and+Occurrence+of+Thioarsenates.">Arsenic in Marina Sediments from the Mediterranean Coast: Speciation in the Solid Phase and Occurrence of Thioarsenates.</a> Soil Sed. Contam. 22, 984-1002 (2013).</li><li>dos Santos Afonso, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reductive+dissolution+of+iron(III)+(hydro)oxides+by+hydrogen+sulfide.">Reductive dissolution of iron(III) (hydro)oxides by hydrogen sulfide.</a> Langmuir. 8, 1671-1675 (1992).</li><li>Postma, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox+zonation:+equilibrium+constraints+on+the+Fe(III)/SO4-reduction+interface.">Redox zonation: equilibrium constraints on the Fe(III)/SO4-reduction interface.</a> Geochem Cosmochim. Acta. 60, 3169-3175 (1996).</li><li>Kumar, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfur+and+oxygen+isotope+tracing+in+zero+valent+iron+based+In+situ+remediation+system+for+metal+contaminants.">Sulfur and oxygen isotope tracing in zero valent iron based In situ remediation system for metal contaminants.</a> Chemosphere. 90, 1366-1371 (2013).</li></ol>

Den eksperimentelle kolonneinnstillinger viste seg for å være en praktisk laboratorium enhet å studere anaerob biogeochemical prosesser i kontinuerlig forhold. Kontinuerlig kolonnen systemer tillater arbeider i forholdene nærmere de av virkelige akviferer enn slurry satsvise systemer eller microcosms. Kontinuerlig systemer kan simulere bevegelse av grunnvann gjennom akvifer sedimenter.
Det viktigste trinnet i protokollen forbereder TE-jern (oxy) hydroxides og blandingen med silica gel og s...

Forstå og forutse spor element (TE) mobilitet og biogeochemistry i miljøet er avgjørende for å overvåke, utvikle og bruke riktige beslutninger for forurensede områder. Dette gjelder særlig i tilfelle av giftige TEs som arsen (As) og kvikksølv (Hg). Skjebne og artsdannelse av disse TEs i jord eller aquifers er nært beslektet fysikalsk-kjemiske forhold, som Eh og pH, men også mikrobiell aktiviteter som kan spille enten en direkte rolle på artsdannelse eller en indirekte rolle på mobilitet.
Faktisk kan noen bakterier direkte oksidere As(III) til As(V) eller redusere As(V) til As(III). Dette påvirker som toksisitet, siden As(III) er den mest giftige, og mobilitet, siden As(III) er mer mobil enn As(V), som kan lett adsorberes jern (oxy) hydroxides eller organisk materiale1,2. Likeledes, bakterier er sterkt involvert i kvikksølv sykling, enten gjennom sin metylering, hovedsakelig av sulfat og jern redusere bakterier3,4, danner neurotoxin monomethyl kvikksølv (lett bioaccumulated i næringskjeden), eller gjennom sin reduksjon til flyktige elementære Hg (Hg °)5.
Begge som Hg skjebne er også sterkt knyttet til jord eller akvifer komposisjon, siden forbindelser som organisk materiale og jern (oxy) hydroxides kan påvirke deres lagring og biotilgjengelighet. AS(V) adsorbs godt til jern (oxy) hydroxides6, mens Hg har svært høy affinitet for organisk materiale (OM, hovedsakelig for thiol grupper), men også for kolloidalt jern eller mangan (oxy) hydroxides i OM utarmet miljøer7,8 , 9 , 10 , 11.
Bakteriell aktiviteter kan deretter påvirke skjebnen til TEs adsorbert (oxy) hydroxides eller organisk materiale gjennom reduksjon av jern (oxy) hydroxides eller mineraliseringen av organisk materiale. Direkte jern reduksjon av bakterier er dominerende veien for jern redusert svovel utarmet soner12,13, Fe(III) brukes som en terminal elektron acceptor, mens indirekte Fe(III) kan reduseres til Fe(II) sulfide dannet av en bakteriell sulfate reduksjon14. Videre, tilstedeværelse av sulfat kan også endre Hg og artsdannelse gjennom dannelsen av komplekser som deg selv thio-arsenates15 som eller metacinnabar med Hg.
Således, en bedre forståelse av virkningen av jern og sulfate sykling på skjebnen til TE, som Hg og som kan hjelpe oss å bedre administrere kontaminerte områder og vedlikeholde jord og vann kvalitet. Data kan også bidra til å forsterke eksisterende metall-mobilitet modeller. Mikrobiell Fe (III)-reduksjon16,17,18 kan føre til desorpsjon av TE. Teoretisk sett, indirekte reduksjon av jern (oxy) hydroxides av sulfide produsert av mikrobielle reduksjon av sulfat kan også påvirke TE mobilitet. Men er omfanget og kinetics av disse reaksjonene generelt studert i satsvis homogen systemer eller satsvis microcosms16,18,19,20. Ulempen med satsvise eksperimenter er mangelen av forekommende fenomener; faktisk aktivitet er basert på og begrenset av ressursene i bunken og bare gir et endelig resultat av endringer i artsdannelse og adsorpsjon. Med en kolonne tilnærming kan fornyelse av inflowing media og overvåking av skjebnen til TE over tid og rom. Disse forholdene er mer realistisk sammenlignet med en akvifer, hvor virkelige fenomener er nært knyttet til kontinuerlig percolation forhold. Videre heterogene jern (oxy) hydroksid forekomst i akvifer sedimenter er vanlige21,23, og romlig endringene i mineralogiske og kjemiske sammensetningen av solid fasene sikkert stasjoner mikrobiell aktiviteter .
For å belyse påvirkning av disse heterogeneities på geo-mikrobiell fenomener og skjebnen til jern-assosiert TE, utviklet vi et laboratorium, en kontinuerlig-matet kolonne representerer en forenklet modell akvifer. Kolonnen er fylt til å lage en jern-utarmet sone på kolonnen inngangen og en jern-rik sone øverst. Vanlig prøvetaking porter gjør oss å studere hver sone individuelt, samt grensesnitt-assosiert fenomener. Et eksempel på bruk av eksperimentelle enheten for studier av Hg skjebne og artsdannelse er allerede tilgjengelig24. Her gir vi en detaljert beskrivelse av det eksperimentelle oppsettet og et annet eksempel av anvendelsen fokusert på virkemåten til som forurenset akviferer.

<table border="0" cellpadding="0" cellspacing="0" width="991">
	<tbody>
		<tr height="120">
			<td height="120" style="height:120px;width:276px;">Glass columns&#160;</td>
			<td style="width:171px;">Beaucaverre, France</td>
			<td style="width:127px;">Specific request</td>
			<td style="width:417px;">columns were composed of 3 separate pieces, the main column core with the cooling jacket and the 5 sampling ports (size GL14 with olive) and a top and bottom piece that fits to the main column body and is held in place with a silicone joint and screw (RIN F 40x38 &#38; SVL 42). note: this design was discussed directly with the company. We recommend to find a local glazier.</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Septa PTFE/silicone diam 20mm&#160;</td>
			<td>Sigma-Aldrich&#160;</td>
			<td>508608</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">PTFE tubing ID 3mm</td>
			<td style="width:171px;">VWR</td>
			<td>228-0745</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Peristaltic pump</td>
			<td style="width:171px;">Dominique Dutsher SAS</td>
			<td style="width:127px;">66493</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Peristaltic pump tubing LMT 55</td>
			<td style="width:171px;">VWR</td>
			<td>224-2250</td>
			<td>Tygon&#174; LMT 55&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Fontainbleau sand&#160; D50=209 &#181;m</td>
			<td>SIBELCO,&#160; France</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:276px;">N2 for bubbling&#160;</td>
			<td style="width:171px;">Air Liquide, France</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Gamma iradiation</td>
			<td>Ionisos, Dagneux, France</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Automatic Mercury Analyser (AMA 254, )</td>
			<td style="width:171px;">Courtage Analyses, France</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Varian SpectrAA 300 Zeeman</td>
			<td style="width:171px;">Agilent&#160;</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:276px;">Name</td>
			<td style="width:171px;">Company</td>
			<td style="width:127px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Chemicals</td>
			<td style="width:171px;"></td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:276px;">HNO3 Supra pur</td>
			<td style="width:171px;">VWR</td>
			<td style="width:127px;">1.00441.1000</td>
			<td>Producer: Merck</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">HCL 30% Supra pur</td>
			<td style="width:171px;">VWR</td>
			<td>1.00318.1000</td>
			<td>Producer: Merck</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:276px;">Hg(NO3)2</td>
			<td style="width:171px;">Merck</td>
			<td>516953</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:276px;">As2O3</td>
			<td style="width:171px;">Merck</td>
			<td style="width:127px;">202673</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:276px;">FeCl3-6H2O</td>
			<td>Merck</td>
			<td>207926</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">silica gel</td>
			<td>Sigma-Aldrich&#160;</td>
			<td>336815-500G</td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental column setup for studying anaerobic biogeochemical interactions between iron (oxy)hydroxides, trace elements, and bacteria

Skjebne og artsdannelse sporstoffer (TEs), som arsen (As) og kvikksølv (Hg), i vannførende lag er nært beslektet physio-kjemiske forhold, som redoks potensielle (Eh) og pH, men også mikrobiell aktiviteter som kan spille en direkte eller indirekte rolle på artsdannelse og/eller mobilitet. Faktisk kan noen bakterier direkte oksidere As(III) til As(V) eller redusere As(V) til As(III). Likeledes, bakterier er sterkt involvert i Hg sykling, enten gjennom sin metylering, danner neurotoxin monomethyl kvikksølv, eller gjennom sin reduksjon til elementær Hg °. Skjebnen til både og Hg er også sterkt knyttet til jord eller akvifer komposisjon; faktisk som og Hg kan binde organiske forbindelser eller (oxy) hydroxides, som vil påvirke mobilitet. I sin tur bakteriell aktiviteter som jern (oxy) hydroksid reduksjon eller organisk materiale mineralisering kan indirekte påvirke som og Hg lagring. Tilstedeværelsen av sulfat/sulfide kan også sterkt påvirke disse bestemte elementer gjennom dannelsen av komplekser som deg selv thio-arsenates med som eller metacinnabar med Hg.
Følgelig mange viktige spørsmål har blitt reist på skjebne og artsdannelse av som og Hg i miljøet og hvordan du kan begrense deres toksisitet. Men fordi deres reaktivitet mot akvifer komponenter er det vanskelig å tydelig dissociate biogeochemical prosessene som oppstår og deres forskjellige virkninger på skjebnen til disse TE.
For å gjøre så, vi utviklet en original, eksperimentell, kolonneinnstillinger som etterligner en akvifer som - eller Hg--jernoksid rike områder mot jern oppbrukt områder, slik at en bedre forståelse av TE biogeochemistry i anoksisk forhold. Følgende protokollen gir trinnvise instruksjoner for kolonne oppsett for som eller Hg, samt et eksempel med som i jern og sulfate redusere forhold.

Eksempel 1. Virkningen av jern reduksjon av mobilitet og artsdannelse
Som kolonnen var direkte inokulert med grunnvann fra et nettsted som presenterer en As konsentrasjon høyere enn de drikke standardene (Bracieux, Loire et Cher, Frankrike). Grunnvann var samplet i sterilt flasker, og lagret på 5 ° C før bruk. Kolonnen ble matet fra bunnen med dette vannet som inneholder naturlige endogene mikrobiell samfunn...

Watch this Scientific Journal Video about Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron OxyHydroxides, Trace Elements, and Bacteria at JoVE.com

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron OxyHydroxides, Trace Elements, and Bacteria

Skjebne og artsdannelse av arsen og kvikksølv i vannførende lag er nært knyttet til physio-kjemiske forhold og mikrobiell aktivitet. Her presenterer vi en opprinnelige eksperimentelle kolonneinnstillinger som etterligner en akvifer og muliggjør en bedre forståelse av spor element biogeochemistry anoksisk forhold. To eksempler er presentert, kombinere geokjemiske og mikrobiologiske tilnærminger.

Eksperimentell kolonneinnstillinger for å studere anaerob Biogeochemical vekselsvirkningene mellom jern (Oxy) Hydroxides, sporstoffer og bakterier

Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as ...

The overall goal of this experimental setup is to study the fate of trace metals under sulfate and/or iron-reducing conditions induced by microbial activities. This method can help answer key questions in the biogeochemistry field such as interactions between key biogeochemical cycles like mercury and arsenic. The main advantage of this technique is that due to the continuous water flow, the dynamics of the biogeochemical reactions and lability of trace elements are dissociated and accessible through the sampling ports.And so, this method can provide insight into the fate of mercury and arsenic as demonstrated here ending to iron oxides. It can also be applied to other trace elements or carrier substrates. Demonstrating the procedure will Hafida Tris, a technician from our laboratory.To begin this procedure, add 500 milliliters of ultrapure water to a glass reactor equipped with a magnetic stir bar. Add 50 grams of iron(III)chloride hexahydrate while stirring. Manually add approximately 50 milliliters of a 10-molar solution of sodium hydroxide to begin precipitation of ferrihydrite.Next, adjust the pH to six and continue stirring for one hour to stabilize. For arsenic-spiked hydroxides and oxyhydroxides, prepare 100 milliliters of arsenic trioxide at a concentration of 10 grams per liter. Then, add 70 milliliters of this solution to the iron oxide solution.Continue stirring for three hours. After this, centrifuge at 2, 000 G for 20 minutes. Remove the supernatant and resuspend the pellet with 50 milliliters of ultrapure water.Repeat the centrifugation ane resuspension two additional times. Recover and store the humid hydroxides and oxyhydroxides as outlined in the text protocol. Keep four grams of silica gel in 40 milliliters of 7%potassium hydroxide on a hot plate stirring with a magnetic stir bar until dissolved.Add 60 milliliters of ultrapure water. Cool the solution on ice to about 20 degrees Celsius to avoid the gel setting too quickly. Titrate the silica gel mixture with phosphoric acid 20%to pH 7.5.Then, quickly mix the liquid silica gel with 320 grams of sterile sand previously mixed with 18.3 grams of either mercury-spiked or arsenic-spiked iron oxides before it solidifies. Using a spatula, break up the gelified mixture. To begin setting up the glass columns, connect the water jackets to a water-cooling system.Set the system to maintain an average temperature of 20 degrees Celsius. Cut lengths of PTFE tubing with a three-millimeter inner diameter making sure there is sufficient length for the column inlet and outlet. Then, add a layer of damp rock wool to the column from the top.Add 320 grams of sterile sand. Add the final layer consisting of the previously mixed sterile sand and spiked hydrated amorphous iron oxides fixed in the silica gel matrix. Next, connect the inflow to peristaltic tubing.Connect the other end of the peristaltic tubing to the water medium supply. Connect an ascendent flow of ultrapure sterile water continuously bubbled by nitrogen gas at low velocity of approximately two milliliters per hour. After this, cover the column with aluminum foil to block out the light.After two weeks, a black-colored precipitate is observed at the interface between the two layers of sand. This black zone progressively invades the top iron hydroxide and oxyhydroxide-enriched zones with the entire upper layer becoming black by the end of the experiment. After 35 days of continuous running, the measured levels of sulfate decrease followed by a transient increase in the total dissolved iron.From day 60 onward, the total dissolved arsenic is seen to rise significantly. On day 54, the physical and chemical parameters are profiled. While the pH remains close to pH seven along the column, the redox potential changes significantly with values nearing negative 200 millivolts in the iron-depleted zone where sulfate reduction is occurring and nearing negative millivolts at the top where bacterial and chemical iron reduction is occurring.Dissolved sulfate concentrations reach to approximately 20 milligrams per liter in the bottom layers and decrease to under one milligram per liter in the iron-rich zone. Sulfate also decreases sharply at the interface between iron-deprived and iron-rich zones indicating a peak of sulfate reduction activity. Meanwhile, arsenic is detected in the upper zone while thioarsenate species are seen closer to the interface and thiosulfate is in the bottom iron-deprived layer.These concentration profiles indicate a peak of sulfate reduction activity at the interface between iron-deprived and iron-rich layers. Following this procedure, other methods like scanning electron microscopy, Raman spectroscopy or activity assays can be performed in order to answer additional questions such as which new minerals are formed or which bacterial communities have developed. Don't forget that working with mercury and arsenic can be extremely hazardous and precautions such gloves and fume hoods should be used while performing this procedure.

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