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

这项工作是共同的 BRGM, 博士后授予来自总参谋部杜 Loiret 和卡诺研究所。我们还感谢 Région 中心--卢瓦尔河谷向枢纽项目提供的财政支助。

1. 实验准备
<ol>
	<li>酸洗所有材料 (玻璃, 聚四氟乙烯 (PFTE)) 与样品接触 (5 天在20% 硝酸 (硝酸3) v/v) 然后5天在盐酸 (HCl) 10% v/v)。用超纯水冲洗多次, 并在使用前在层流罩下干燥。</li>
	<li>使用聚乙烯手套 (或类似) 和油烟罩的所有步骤涉及化学品。</li>
</ol>
2. 制备 Hg 和非晶态铁氧化物
<ol>
	<li>准备大约20克 ferryhydrate (Fe (OH)3): 溶解50克 FeCl3-6H2O 在500?...

<ol>
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实验柱的设置证明是一个方便的实验室设备, 研究厌氧生物地球化学过程中的连续条件。连续柱系统允许在比泥浆批处理系统或缩影更接近实际含水层的条件下工作。连续系统可以模拟地下水通过含水层沉积物的流动。
该协议中最关键的步骤是制备 TE 铁 (氧) 氢氧化物和硅凝胶和沙子的混合物, 这需要迅速创建, 以获得均匀的质地。除了这一一般关键步骤之外, 还必须仔细设计?...

了解和预测环境中的微量元素 (TE) 移动性和地球化学是至关重要的, 以便监测、开发和适用污染场址的适当管理决策。这尤其适用于有毒的附加费, 如砷 (as) 和汞 (汞) 的情况。这些污水附加费在土壤或含水层中的命运和形态与物理化学条件密切相关, 如 Eh 和 pH, 也与可以直接作用于物种形成或对流动的间接作用的微生物活动有关。
的确, 有些细菌可以直接氧化为 (iii) 至 as (v) 或减少为 (v) 至 as (iii)。这影响作为毒性, 因为 (iii) 是作为和流动性的最毒的形式, 因为 (iii) 比作为 (V) 更流动, 能容易地吸附对铁 (氧) 氢氧化物或有机物质1,2。同样, 细菌强烈参与水星循环, 或者通过它的甲基化, 主要由硫酸盐和铁减少的细菌3,4, 形成神经毒素一甲基汞 (容易生物在食物链中),或通过其还原为挥发性单质 Hg (Hg°)5。
砷和汞的命运也与土壤或含水层组成密切相关, 因为有机物质或铁 (氧) 氢氧化物等化合物可以影响它们的螯合和生物利用度。作为 (V) 吸附井对铁 (氧) 氢氧化物6, 而 Hg 有非常高亲和性为有机物 (om; 主要为硫醇基团), 但也为胶体铁或锰 (氧) 氢氧化在 OM 耗尽的环境7,8,9,10,11。
通过减少铁 (氧) 氢氧化物或有机质的矿化作用, 细菌活动就能影响吸附于 (氧) 氢氧化物或有机物的污水附加费的命运。用细菌直接还原铁是硫磺枯竭区铁还原的主要途径12,13, fe (iii) 被用作终端电子受体, 而间接地, fe (iii) 可由硫化物还原为 fe (II)由细菌硫酸盐减少14形成。此外, 硫酸盐的存在也可以通过形成络合物, 如硫代砷15以汞或 metacinnabar 的形式来改变 hg 和形态。
因此, 更好地了解铁和硫酸盐循环对汞的命运的影响, 如 Hg 和 as, 可以帮助我们更好地管理受污染的场址和保持土壤和水的质量。数据也有助于加强现有的金属流动模型。微生物 Fe (III)-减少16,17,18可导致 TE 的解吸。从理论上讲, 通过微生物还原硫酸盐产生的硫化物间接还原铁 (氧), 也会影响 TE 的流动性。但是, 这些反应的程度和动力学一般都是在批同质系统或批缩影16、18、19、20中进行研究的。间歇实验的缺点是缺乏对发生现象的分离;事实上, 活动是基于和有限的资源存在于批中, 只给出最后的结果的转变的形态和吸附。使用列方法可以更新流入媒体, 并监视时间和空间上的 TE 的命运。与含水层相比, 这些条件更切合实际, 那里的实际现象与连续的渗流条件密切相关。此外, 非均质铁 (氧) 氢氧化物发生在含水层沉积是共同的21,23, 并且固相矿物和化学成分的空间变化肯定会推动微生物活动.
为了阐明这些质对地质微生物现象的影响和与铁相关的 TE 的命运, 我们开发了一个实验室, 一个连续哺养的专栏代表一个简化的模型含水层。柱子被填装在专栏入口创造一个铁枯竭的区域和一个富铁的区域在顶端。定期取样端口使我们能够单独研究每个区域以及与接口相关的现象。这个实验装置的应用的例子为研究 Hg 命运和形态学已经是可利用的24。在这里, 我们给出了实验设置的详细描述和第二个例子, 其应用的重点是在受污染的含水层的行为。

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	<tbody>
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			<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>
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			<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

含水层中的砷 (as) 和汞 (汞) 等微量元素的命运和形态与物理化学条件密切相关, 如氧化还原电位 (Eh) 和 pH 值, 但也与可直接或间接作用于生物的微生物活动有关形态和/或移动性。的确, 有些细菌可以直接氧化为 (iii) 至 as (v) 或减少为 (v) 至 as (iii)。同样, 细菌也强烈参与汞循环, 无论是通过其甲基化, 形成神经毒素单汞, 或通过其还原为元素 Hg°。砷和汞的命运也与土壤或含水层组成密切相关;事实上, 砷和汞可以结合到有机化合物或 (氧) 氢氧化物, 这将影响它们的流动性。反过来, 细菌活动, 如铁 (氧) 氢氧化还原或有机质矿化可以间接影响和汞螯合物。硫酸盐/硫化物的存在也能强烈地影响这些特定的元素, 通过形成诸如硫砷与砷或 metacinnabar 与汞的配合物。
因此, 人们对环境中砷和汞的命运和形态以及如何限制它们的毒性提出了许多重要的问题。然而, 由于它们对含水层组分的反应性, 很难明确地将发生的生物地球化学过程和它们对这些物质的命运的不同影响区分开来。
为了做到这一点, 我们开发了一个原始的, 实验的, 列的设置, 模拟一个含水层与砷或 Hg 氧化铁丰富的地区与铁耗尽地区, 使更好地了解 TE 地球化学在缺氧条件。以下协议给列设置的一步一步指示为作为或 Hg, 并且一个例子与一样在铁和硫酸盐减少的情况之下。

示例1。铁的减少对流动性和形态的影响
as 柱是直接接种与地下水从一个网站呈现的浓度高于饮用水标准 (Bracieux, 卢瓦尔等雪儿, 法国)。在无菌瓶中抽取地下水, 贮存在5° c 直至使用。这一列是从底部喂养的水中含有天然内源性微生物群落在低流速率 (2 毫升 h-1), 以促进细菌附着在沙子上。温度最初固定在25...

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

含水层中砷和汞的命运和形态与生理-化学条件和微生物活动密切相关。在这里, 我们提出了一个原始的实验柱设置, 模拟一个含水层, 并使更好地了解在缺氧条件下的痕量元素地球化学。结合地球化学和微生物方法, 提出了两个实例。

用于研究铁 (氧) 氢氧化物、微量元素和细菌之间厌氧生物地球化学相互作用的实验柱装置

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.

Research

JoVE Journal

Environment

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron (Oxy)Hydroxides, Trace Elements, and Bacteria

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科研

环境科学

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