constructing the columns and the mesh system for leachate collection to study mineral weathering

Améliorer la séquestration du CO2 : une approche du biote du sol pour stimuler l’altération minérale

Enhanced weathering (EW) is a relatively new and low-tech carbon dioxide removal (CDR) technology with a significant potential to mitigate climate change1,2,3. The principle of this technology relies on accelerating the natural mineral weathering process in soils, leading to the sequestration of carbon dioxide (CO2) as inorganic carbon (IC)3. Enhanced weathering aims at increasing IC sequestration by artificially optimizing the factors governing mineral weathering, thereby enhancing the speed through which weathering occurs to humanly relevant time scales3. For EW to be most effective, fast-weathering silicate minerals are ground into a powder with a grain size distribution in the micrometers to millimeters range to reach a high reactive surface area in the ~1 m2&#183;g-1 range3,4.
So far, knowledge about EW has been mainly provided by experiments that focus on abiotic factors governing the rates at which minerals are dissolved5. These include mineral reactivity and surface area, temperature, solution composition, water residence time, and acidity4,6,7, but research still needs to be done within this context. Besides being influenced by abiotic factors, natural systems, and soils in particular, are shaped by a vast number of organisms, ranging from microbes to macrofauna such as earthworms. Despite some studies having shown little or no influence of the biotic activity of mineral dissolution8,9,10, other studies have provided evidence that soil organisms such as bacteria11,12, fungi13,14, and earthworms15,16 could increase mineral weathering rates. Therefore, biotic components could be key to understanding the actual IC sequestration potential of EW5.
The first common mechanism through which soil organisms could accelerate mineral dissolution is via CO2 release during respiration,which increases soil acidification17. Besides, bacteria and fungi could increase mineral weathering by exuding protons, chelates, organic acids, and enzymes, all of which enhance mineral dissolution18,19,20,21. For example, chelation through carboxyl and hydroxyl groups can create ion imbalances, transporting elements away from the surfaces of minerals and lowering saturation states20,22. This could lead to less secondary mineral formation and higher efficiency of EW. Moreover, by feeding on soil particles, the strong actions of earthworms&#39; body walls could break down mineral grains into finer particles, increasing their available reactive surface area23. Microbes dwelling in earthworms&#39; intestines and fresh droppings could further attack these smaller particles, which further exudate organic acids and enzymes24,25. Through their burrowing activity, in addition to contributing to the mixing of organic and mineral particles, earthworms also create macropores that could allow water flow to bypass saturated pore space17. This could enable the water to interact with different mineral surfaces and enhance the water-rock contact rate.
Until now, no setup has been built to study EW rates and therefore IC sequestration using soil organisms while ensuring the possibility to optimize different relevant abiotic conditions, such as water inputs, temperature, mineral type, and mineral grain size. Here, the design and explanation of the construction steps of an innovative setup that aims at increasing EW rates through the activity of soil organisms in small mesocosms are presented. The experimental setup consists of 203 columns (length 15 cm, diameter 7 cm) placed in a climate chamber (4.54 m x 2.72 m) at 25 &#176;C for 8 weeks. The 203 columns are divided into 10 groups of 18 and 2 groups of 10 to fit in the climate chamber. One of the two groups of 10 columns is used to allow the insertion of three more columns which are used as blanks. Each group is placed above a fridge and is topped by a remotely controllable irrigation system, which allows for variable irrigation rates within and between fridges. The leachate of each column is collected in a jerrycan kept at a constant temperature in the fridge (Figure 1). One fridge collects the leachate of a group of columns, meaning that one fridge can be considered as a single system of either 18 or 10 columns. Therefore, the number of columns in this experimental setup can be adjusted according to experimental requirements with a maximum of 203 columns.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65563/65563fig01.jpg" /> 
Figure 1: Schematic side-view of the setup showing 5 columns but considering a system of 18 columns. The frame holding the columns is made of stainless-steel plates, stainless steel screws and acrylic plates. Columns are positioned in the middle of the frame and are topped by an irrigation system. Below the columns, funnels are connected to jerrycans through pipes to collect the leachate. Jerrycans are in a fridge that holds the whole system. The fridge can be opened by lifting the lid. <a href="https://www.jove.com/files/ftp_upload/65563/65563fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this setup, the use of silicate rock powders of specific grain sizes ensures that high weathering rates can be reached, while the inoculation with specifically selected bacteria, fungi, and earthworms grants the biotic activity in this artificial system. The setup enables concurrent quantification of carbon sequestered in the solid and in the liquid samples by measuring both dissolved and solid IC, as well as total alkalinity (TA). Besides, other parameters such as pH, electrical conductivity (EC), and ions can be measured in the leachate as indicators of weathering. This setup also allows the assessment of the impact of soil organisms&#39; survival and activity. Representative results are shown to prove the suitability of this protocol to build a setup where increases in weathering rates are derived not only from abiotic factors but also from biotic ones.

Pleins feux sur l’auteur : Démêler le rôle des vers de terre dans l’amélioration de l’altération minérale pour l’élimination du CO2 

Conception et construction d’un dispositif expérimental pour améliorer l’altération minérale par l’activité des organismes du sol

Watch this Scientific Journal Video about Constructing the Columns and the Mesh System for Leachate Collection to Study Mineral Weathering at JoVE.com

Constructing the Columns and the Mesh System for Leachate Collection to Study Mineral Weathering  

Construction des colonnes et du système de maillage pour la collecte des lixiviats afin d’étudier l’altération minérale

Pour commencer, construisez l’installation du réfrigérateur pour la collecte des lixiviats. Prenez la colonne en PVC pour incuber la poudre de roche et les organismes du sol. Acquérez également des anneaux centraux pour maintenir les colonnes au-dessus des entonnoirs.Positionnez les anneaux à quelques centimètres du bas des colonnes. Acquérir du matériel pour créer un système de maillage au bas des colonnes afin de filtrer le lixiviat. Placez la maille de 20 micromètres au bas de la colonne et ajoutez une couche d’un centimètre de billes de plastique sur cette maille.Ensuite, placez un maillage de 10 micromètres sur le maillage de 20 micromètres. Fixez les mailles en place à l’aide de deux serre-câbles. Serrez-les fermement et retirez les liens en excès en coupant leurs bords.L’installation est maintenant prête à être remplie avec le mélange organominéral et inoculée avec des organismes du sol.

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Research

JoVE Journal

Biochemistry

Constructing the Columns and the Mesh System for Leachate Collection to Study Mineral Weathering

393 vues. Pour commencer, construisez l’installation du réfrigérateur pour la collecte des lixiviats. Prenez la colonne en PVC pour incuber la poudre de roche et les organismes du sol. Acquérez également des anneaux centraux pour maintenir les colonnes au-dessus des entonnoirs.Positionnez les anneaux à quelques centimètres du bas des colonnes. Acquérir du matériel pour créer un système de maillage au bas des colonnes afin de filtrer le lixiviat. Placez la maille de 20 micromètres au...

Vidéo: Constructing the Columns and the Mesh System for Leachate Collection to Study Mineral Weathering  

Design and Construction of an Experimental Setup to Enhance Mineral Weathering through the Activity of Soil Organisms

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies on accelerating the natural process of mineral weathering in soils by manipulating the abiotic variables that govern this process, in particular mineral grain size and exposure to acids dissolved in water. EW mainly aims at reducing atmospheric CO2 concentrations by enhancing inorganic carbon sequestration. Until now, knowledge of EW has been mainly gained through experiments that focused on the abiotic variables known for stimulating mineral weathering, thereby neglecting the potential influence of biotic components. While bacteria, fungi, and earthworms are known to increase mineral weathering rates, the use of soil organisms in the context of EW remains underexplored. 
 This protocol describes the design and construction of an experimental setup developed to enhance mineral weathering rates through soil organisms while concurrently controlling abiotic conditions. The setup is designed to maximize weathering rates while maintaining soil organisms' activity. It consists of a large number of columns filled with rock powder and organic material, located in a climate chamber and with water applied via a downflow irrigation system. Columns are placed above a fridge containing jerrycans to collect the leachate. Representative results demonstrate that this setup is suitable to ensure the activity of soil organisms and quantify their effect on inorganic carbon sequestration. Challenges remain in minimizing leachate losses, ensuring homogeneous ventilation through the climate chamber, and avoiding flooding of the columns. With this setup, an innovative and promising approach is proposed to enhance mineral weathering rates through the activity of soil biota and disentangle the effect of biotic and abiotic factors as drivers of EW.

Here we present the construction and operation of an experimental setup to enhance mineral weathering through the activity of soil organisms while concurrently manipulating abiotic variables known to stimulate weathering. Representative results from the functioning of the setup and sample analyses are discussed together with points for improvement.

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies ...