This work was supported by a Food from Thought Commercialization Grant, which is funded from the Canada First Research Excellence Fund. Canadian Wollastonite provided industrial financial support as part of this Grant.

1. Soil sampling method and core collection
<ol>
	<li>Divide the mapped and a demarcated agricultural land area of interest into different plots based on the land elevation, historical crop yield, and/or land management strategy. Determine the leveling of each plot using a GPS receiver, classify crop yield based on historical farm records (below-average, average, above-average), and the land management strategy used for each plot (types of soil amendments used, if any). Place the flags at the boundaries of each plot to ease subsequent sampling. 
	NOTE: Figure 1 shows the sectioning of the rectangular area under study into four plots (A, B, C, D). Such an experimental design and information will be helpful to check the statistical significance of the analyzed data. Furthermore, it can be appropriate for irregular farmlands and be convenient for aligning sampling according to a parameter deemed necessary, from the orientation of crop rows to the direction of terrain, runoff, dominant wind, sun path, etc. These four plots were considered in order to facilitate a field filming campaign.</li>
	<li>Use the directed random sampling method to collect cores across each plot. Subdivide each plot following a grid pattern into 25 sub-plots (Figure 2). Collecting 25 cores is above the traditionally minimum recommend number of cores (15-20).</li>
</ol>
&#8203;<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61996/61996fig01.jpg" /> 
Figure 1: Representation of the plots used for sample collection (each plot represents an area of 5 m &#215; 10 m (totally four x 50 m2).&#160;Black flags delimit each plot boundary to ease sampling, and white flags mark locations for deep sampling.&#160;<a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/61996/61996fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61996/61996fig02.jpg" /> 
Figure 2: Sub-sectioning of each plot for collecting core samples (each sub-section represents an area of 1 m x 2 m), based on directed random sampling method.&#160;<a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/61996/61996fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>Collect core samples from random points within each sub-plot, one per sub-plot. Use a soil probe or a soil core sampler to collect the soil core down to three depth zones of 0-15 cm, 15-30 cm, and 30-60 cm to account for the SIC variation with depth due to silicate soil amendment. 
	NOTE: Depending on the type of soil and the probe/sampler used, a different sampler may be required to collect the 30-60 cm sample.</li>
	<li>Use an extendable auger (or similarly capable sampler) to collect deep soil samples from the white flag locations in Figure 1, down to additional three depth zones of 60-100 cm, 100-175 cm, and 175-250 cm. These samples account for the soil characterization variation within these depths as well as evaluate background SIC level in the investigated land area, down to the upper depth of the naturally occurring pedogenic carbonate horizon. 
	NOTE: Based on the local properties in site (e.g., depth of groundwater table), the deepest zone may be modified in different locations.</li>
	<li>Transport the soil samples into buckets, one for each sampled depth at each plot. Hand-blend the soils in each bucket thoroughly. Place the portable moisture tester into the mixed soil sample. Wait until the moisture content fixes at a stable point on the gauge of the device. Press the holder button and record the value as the real-time moisture content of blended soils.</li>
	<li>Store the composite samples in sealed bags. Label bags properly with information about the plots (A, B, C, or D), the soil depth (0-15 cm, 15-30 cm, 30-60 cm, 60-100 cm, 100-175cm, 175-250 cm), and date of sampling.</li>
</ol>
2. Soil fractionation prior to chemical analysis
<ol>
	<li>Air-dry the soil samples as soon as possible after sampling to minimize the oxidation of soil carbon. For this, place the soil samples in cardboard boxes (2.5&#34; x 3&#34; x 3&#34;) and place the boxes in a drying cabinet at 50 &#176;C for 24-48 h, until the soil is dry. Store the air-dried samples in sample bags until further analysis.</li>
	<li>Prior to soil fractionation, run the soil samples through a 2-mm sieve to remove large fragments of rocks and plant remains.</li>
	<li>Oven-dry the sieved soils by placing the samples in a muffle furnace maintained at 105&#160;&#177; 2 &#176;C for at least 15 h.</li>
	<li>For soil fractionation, place 1 kg of the oven-dried sample onto the top mesh of the sieve shaker consisting of different mesh sizes (710 to 50 &#181;m). Shake the sieves at 60 rpm for 15 min. Pan fractions &#60;50 &#181;m are preferably used for analyses, as this is the pedogenic carbonate-enriched soil fraction. 
	&#8203;NOTE: Other soil fractions can also be tested to yield additional data for verification of SIC accumulation due to enhanced weathering of amended silicates.</li>
</ol>
3. Pedogenic inorganic carbon sequestration determination
<ol>
	<li>To determine the inorganic carbon content of soil samples using calcimetry analysis, place 5 g of a sieved soil sample in an appropriate Erlenmeyer flask. Suspend the sample in 20 mL of ultrapure water. Add 7 mL of 4&#160;M HCl to a small flat-bottomed glass test tube, then place this tube upright inside the flask using a pair of tweezers.</li>
	<li>Carefully attach the flask to the calcimeter by affixing the rubber stopper. The burette water levels on the calcimeter should have been previously adjusted as required, and blanks and CaCO3 standards should have been once run on the calcimeter as needed.</li>
	<li>Shake the flask, thereby knocking over the acid tube, until the water level in the burette reaches a constant value, and no bubbling is observed in the solution (this takes approximately 5 min).</li>
	<li>Calculate the CaCO3-equivalent (CaCO3(eqv)) content of the sample (g,CaCO3(eqv)&#183;(kg,soil)-1) based on the volume change observed in the burette, and the blank and CaCO3 calibration values, using the appropriate calcimetry formula. SIC content is obtained by converting the g,CaCO3(eqv)&#183;(kg,soil)-1 value into kg,CO2&#183;(tonne,soil)-1 or kg,C&#183;(tonne,soil)-1.
	<ol>
		<li>Calculate the CaCO3(eqv) content of the sample using the below formula: 
		<img alt="Equation 1" src="/files/ftp_upload/61996/61996eq1.jpg" />&#160; (4) 
		Where: 
		w (CaCO3(eqv)) = the carbonate content of the oven-dried soil 
		m1&#160;= the mass of the test portion 
		m2 &#8203;= the mean mass of the calcium carbonate standards 
		V1 = the volume of carbon dioxide produced by the reaction of the test portion 
		V2 = the mean volume of carbon dioxide produced by the calcium carbonate standards 
		V3 = the volume change in the blank determinations 
		w (H2O)&#160;= the water content of the dried sample 
		NOTE: steps 3.1 to 3.4 are conducted based on a standard protocol29.</li>
	</ol>
	</li>
	<li>For measuring bulk density (BD) of soil ((tonne,soil)&#183;m&#8722;3), place a sufficiently large aliquot of the oven-dried soil sample in a container with a known volume. Weigh the sample using a scale. The ratio of the dried weight to the volume of the sample is considered as BD. 
	NOTE: The alternative devices for calculating &#34;undisturbed bulk density&#34; are introduced in the discussion.</li>
	<li>Calculate the Areal SIC (kg,CO2&#183;(hectare)&#8722;1) using the following formula: 
	<img alt="Equation 2" src="/files/ftp_upload/61996/61996eq2.jpg" />&#160; (5) 
	Where: 
	A = the surface area 
	DT = depth thickness</li>
	<li>Calculate the Total SIC (SIC 0-60 cm, kg,CO2&#183;(hectare)&#8722;1) for each plot, using the areal SIC values obtained for each depth, as follows: 
	SICPlot A&#160;= SIC0-60 cm&#160;= SIC0-15 cm&#160;+ SIC15-30 cm&#160;+ SIC30-60 cm&#160; (6)</li>
	<li>Add the Total areal SIC (SIC 0-60 cm, kg,CO2&#183;(hectare)&#8722;1) content for each plot (A, B, C, D) investigated, and obtain the average mean as follows: 
	<img alt="Equation 3" src="/files/ftp_upload/61996/61996eq3v2.jpg" />&#160; &#160; (7)</li>
	<li>Divide the Mean areal SIC (kg,CO2&#183;(hectare)&#8722;1) obtained from Eq. 7 by the application rate of silicate mineral/rock used for the soil amendment ((tonne, silicate)&#183;(hectare)&#8722;1). 
	NOTE: This will provide the amount of pedogenic inorganic carbon sequestered in terms of kg of CO2 per tonne of silicate applied (kg, CO2&#183;(tonne, silicate)&#8722;1). If a multi-year investigation is done, or a control plot without silicate amendment is present, this step needs to be modified to account for total sequestration and total amendment over a longer-term, or year-over-year values, or net pedogenic carbon sequestration.</li>
</ol>

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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=Neoformation+of+pedogenic+carbonates+by+irrigation+and+fertilization+and+their+contribution+to+carbon+sequestration+in+soil.">Neoformation of pedogenic carbonates by irrigation and fertilization and their contribution to carbon sequestration in soil.</a> Geoderma. 262, 12-19 (2016).</li><li>Carmi, I., Kronfeld, J., Moinester, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequestration+of+atmospheric+carbon+dioxide+as+inorganic+carbon+in+the+unsaturated+zone+under+semi-arid+forests.">Sequestration of atmospheric carbon dioxide as inorganic carbon in the unsaturated zone under semi-arid forests.</a> Catena. 173, 93-98 (2019).</li><li>Washbourne, C. L., Lopez-Capel, E., Renforth, P., Ascough, P. L., Manning, D. A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+removal+of+atmospheric+CO2+by+urban+soils.">Rapid removal of atmospheric CO2 by urban soils.</a> Environmental Science and Technology. 49 (9), 5434-5440 (2015).</li></ol>

The authors have no conflict of interest.

Given that collecting samples from fertilized agricultural fields is usually difficult, it is suggested that samples should be collected before nutrient application. It is also advisable to avoid collecting samples from frozen fields. The sampling depth may vary in different areas depending on the ease of sampling over the vertical profile, and the depth of the water table. The selected soil sampling device is dependent on the soil structure and depth of interest33. While it is more convenient to ...

CO2 is a major greenhouse gas (GHG), and its concentration in the atmosphere is increasing continuously. Preindustrial global average CO2 was about 315 parts per million (ppm), and as of April 2020, the atmospheric CO2 concentration increased to over 416 ppm, hence causing global warming1. Therefore, it is critical to reduce the concentration of this heat-trapping GHG in the atmosphere. Socolow2 has suggested that to stabilize the concentration of atmospheric CO2 to 500 ppm by 2070, nine &#39;stabilization wedges&#39; will be required, where each stabilization wedge is an individual mitigation approach, sized to achieve 3.67 Gt CO2 eq per year in emissions reduction.
Carbon capture and storage (CCS) is the main technology to reduce the CO2 from the atmosphere, as recommended by the Mission Innovation initiative, launched at the United Nations Climate Change Conference 20153. To capture atmospheric CO2, the three main storage options available are ocean storage, geological storage, and mineral carbonation4. Focusing on mineral carbonation, CO2 is stored by converting alkaline earth metals, mainly calcium- and magnesium-rich silicates, into thermodynamically stable carbonates for geological timeframes (over millions of years)5. For example, olivine, pyroxene, and serpentine group minerals have the potential to undergo mineral carbonation6; however, under normal conditions, these reactions are limited by slow reaction kinetics. Therefore, to speed up the process under ambient conditions, finely comminuted (crushed/milled) forms of these silicates can be applied to agricultural soils, a process referred to as terrestrial enhanced weathering7. Soil is a natural sink to store CO2, presently being a reservoir for 2500 Gt of carbon, which is thrice the atmospheric reservoir (800 Gt carbon)8. Pedogenic processes in soils and subsoils regulate atmospheric CO2 by two major natural pathways, namely the organic matter cycle and the weathering of alkaline earth metal minerals, affecting organic and inorganic carbon pools, respectively9.
It is estimated that almost 1.1 Gt of atmospheric CO2 is mineralized through chemical rock weathering annually10. Silicate rocks rich in calcium and magnesium (e.g., basalt) are regarded as the primary feedstocks for enhanced weathering9,11,12. Once crushed silicate-containing minerals are applied to agricultural fields, they begin to react with CO2 dissolved in soil porewater, concluding with the mineral precipitation of stable carbonates11,13. Olivine14,15, wollastonite (CaSiO3)13, dolerite, and basalt16 are among minerals which have demonstrated carbon sequestration potential through enhanced weathering in previous studies. Despite the greater availability, and hence possibly greater CO2 sequestration capacity, of magnesium silicates, there are concerns about their application for enhanced weathering in croplands due to their potential environmental impact as a result of Cr and Ni leaching and the possible presence of asbestiform particulates11,15,17,18. As a calcium-bearing silicate, wollastonite is herein highlighted as a prime candidate for this process due to its high reactivity, simple chemical structure, being environmentally benign as well as facilitating the production of carbonates due to the weaker bonding of Ca ions to its silica matrix12,19,20,21. Wollastonite that is mined in Kingston, Ontario, Canada, and is presently commercialized by Canadian Wollastonite for agricultural applications, does not contain elevated levels of hazardous metals. The worldwide wollastonite reserves are estimated to be over 100 Mt, with China, India, USA, Mexico, Canada, and Finland as the top productive countries22.
Enhanced weathering of silicate mineral is reckoned to promote soil health, notably crop yield increase and plant growth improvement, leading to the potential reduction in the application of synthetic fertilizers, which can further contribute to GHG emissions reduction11,18,19. Previous studies have reported that the application of Ca-rich silicate minerals to soils supplies basicity for neutralizing acidity in the soil medium, favoring crop production23,24,25. This also impedes toxic metals mobilization, susceptible to acidic conditions, and enhanced weathering could be useful for retarding erosion through soil organic matter increment11.
Equations 1-3 show how pedogenic carbon sequestration as inorganic carbonates is possible by amending soils with wollastonite. Ambient CO2 enters the soil through rainwater or is produced in soil by microbial activity degrading organic compounds. Once in contact with soil porewater, carbonic acid is formed, which dissociates to form bicarbonate and proton (Equation 1). In the presence of plants, root exudates, such as citric acid and maleic acid, are released, which also provide protons in the system. These protons facilitate the dissolution of wollastonite in the soil through releasing Ca ions and leaving behind amorphous silica (Equation 2). The released Ca ions ultimately react with the bicarbonate to precipitate as carbonates (crystalline calcite or other varieties, depending on geochemical conditions) (Equation 3). This formed calcium carbonate becomes part of the soil inorganic carbon (SIC) fraction26.
Ambient CO2 solvation:
2CO2(g) + 2H2O(l) &#8596; 2H2CO3(aq) &#8596; 2HCO3- + 2H+ (1)
Wollastonite dissolution (H+ from the dissociation of carbonic acid and root exudates):
CaSiO3(s) + 2 H+ &#8594; Ca2+ + H2O(l) + SiO2(s)&#160;(2)
Pedogenic inorganic carbonate precipitation:
Ca2+ + 2 HCO3- &#8594;&#160; CaCO3(s)&#8595; + H2O(l) + CO2(g)&#160;(3)
In our recent work, enhanced weathering through the application of wollastonite to agricultural soils, as a limestone-alternative amendment, has been found effective for CaCO3 precipitation in topsoil, both at laboratory and field scales, and over short (few months) and long (3 years) terms. In the field studies, chemical and mineralogical assessments have revealed that the SIC content increases proportionally to wollastonite application dosage (tonne&#183;hectare-1)13. In laboratory studies, the mineralogical analysis showed the presence of pedogenic carbonate due to carbon sequestration19. Pedogenic carbonate formation in soil depends on several factors, most notably: topography, climate, surface vegetation, soil biotic processes, and soil physicochemical properties27. Our previous study23 determined the role of plants (a leguminous plant (green bean) and a non-leguminous plant (corn)) on wollastonite weathering and inorganic carbonate formation in soil. Our ongoing research on the pedogenic carbon formation and migration in soils and subsoils includes investigating the fate of soil carbonates in agricultural soil, first formed in topsoils due to mineral weathering at various depths and over time. According to Zamanian et al.27, the naturally occurring pedogenic carbonate horizon is found farther from the surface as the rate of local precipitation increases, with the top of this horizon commonly appearing between a few centimeters to 300 cm below the surface. Other ambient and soil parameters, such as soil water balance, seasonal dynamics, the initial carbonate content in parent material, soil physical properties, also impact the depth of this occurrence27. Thus it is of significance to sample soils to a sufficient depth at all opportunities to obtain an accurate understanding of the original and the incremental levels of SIC resulting from enhanced weathering of silicates.
At the field scale, an important limitation is the use of low application rates of silicate soil amendments. As there is limited knowledge on the effect of many silicates (such as wollastonite and olivine) on soil and plant health, commercial producers avoid testing higher application rates that could result in significant carbon sequestration. As a result of such low application rates, as well as the large area of crop fields, a research challenge commonly faced is to determine changes in SIC when values are relatively low, and to recover and isolate the silicate grains and weathering products from the soil to study morphological and mineralogical changes. In our past work, we reported on how physical fractionation of the wollastonite-amended soil (using sieving) enabled a better understanding of the weathering process, especially the formation and accumulation of pedogenic carbonates28. Accordingly, the higher contents of wollastonite and weathering products were detected in the finer fraction of soil, which provided reasonably high values during analyses, ensuring more precise and reliable results. The findings highlight the importance of using physical fractionation, through sieving or other segregation means, for reliable estimation of the sequestrated carbon accumulation in silicate-amended soils. However, the degree of fractionation could vary from soil to soil and from silicate to silicate, so it should be further researched.
Accurate measurement of SIC is critical for establishing a standard and scientific procedure that can be adopted by various researchers interested in analyzing the evolution of SIC and (and organic carbon) over time and depth of the soil. Such methodology enables farmers to claim carbon credit as a result of SIC formation in their field soils. The following protocol describes, in detail: (1) a soil sampling method to be used following soil silicate amendment, which accounts for the statistical significance of the analyzed soil data; (2) a soil fractionation method that improves the accuracy of quantifying changes in pedogenic inorganic carbonate pool as a result of enhanced silicate weathering, and (3) the calculation steps used to determine the SIC sequestration rate as a result of soil silicate amendment. For the purpose of this demonstration, wollastonite, sourced from Canadian Wollastonite, is assumed to be the silicate mineral applied to agricultural soils, and the agricultural soils are considered to be similar to those found in Southern Ontario&#39;s farmlands.
The procedure involving amending agricultural soil with wollastonite (e.g., determining the amount of wollastonite to apply per hectare, and the method to spread it over the soil) was described in our previous study13. The study area in our prior and present work is rectangular plots; therefore, the direct random sampling method is appropriate for such studies. This is a commonly used method owing to its low cost, reduced time requirement, and ability to provide adequate statistical uncertainty. Similarly, depending on the various field conditions and the level of statistical significance desired, zonal or grid sampling methods can also be used. Accuracy in soil sampling is essential to reduce statistical uncertainty as a result of sampling bias. When statistics are used, achieving less than 95% confidence (i.e., p &#60; 0.05) is not considered &#34;statistically significant.&#34; However, for certain soil studies, the confidence level may be relaxed to 90% (i.e., p &#60; 0.10) owing to the number of uncontrolled (i.e., naturally varying) parameters in the field conditions that affect the general precision of measurements. In this protocol, two sets of samples are collected in order to investigate SIC content and other chemical, mineral, and morphological properties of the soil throughout its vertical profile.

<table><tbody><tr><td>Analytical scale</td><td>Sartorius</td><td>Quintix 224-S1</td><td>Four decimals.</td></tr><tr><td>Calcimeter</td><td>Eijkelkamp</td><td>Model 08.53</td><td>To determine the wt% CaCO&lt;sub&gt;3&lt;/sub&gt;-equivalent in the sample.</td></tr><tr><td>Drying cabinet/muffle furnace</td><td>Thermo Scientific</td><td>F48055-60</td><td>50&amp;deg;C or 103 &amp;plusmn; 2&amp;deg;C.</td></tr><tr><td>HCl</td><td>Fisher Scientific</td><td>A144S-500</td><td>Reagent grade (36.5%-38.0%).</td></tr><tr><td>HNO&lt;sub&gt;3&lt;/sub&gt;</td><td>Fisher Scientific</td><td>T003090500</td><td>Trace metal analysis grade (69.0%-70.0%)</td></tr><tr><td>Inductively Coupled Plasma Mass Spectrometer (ICP-MS)</td><td>PerkinElmer</td><td>NexION</td><td>To determine the concentration of Ca in the microwave-digested soil.</td></tr><tr><td>Microwave digester</td><td>PerkinElmer</td><td>Titan</td><td>To digest soils in concentrated HNO&lt;sub&gt;3&lt;/sub&gt;.</td></tr><tr><td>pH meter</td><td>Oakton</td><td>700</td><td>Calibrated with standard solutions before each set of measurements; temperature corrected to 25 &amp;deg;C.</td></tr><tr><td>Scanning Electron Microscope -Energy Dispersive Spectroscope (SEM-EDS)</td><td>Oxford</td><td>X-Max20 SSD</td><td>To determine the morphology of soil particulates.</td></tr><tr><td>Sieve shaker</td><td>Retsch</td><td>AS-200</td><td>For soil fractionation.</td></tr><tr><td>Soil auger sampler</td><td>Eijkelkamp</td><td>01-16</td><td>Depths down to 700 cm.</td></tr><tr><td>Soil Dakota probe sampler</td><td>JMC</td><td>PN139</td><td>Depths down to 100 cm.</td></tr><tr><td>Soil probe sampler</td><td>JMC</td><td>PN031</td><td>Depths down to 30 cm.</td></tr><tr><td>Soil moisture meter</td><td>Extech</td><td>MO750</td><td>Measure moisture content up to 50%</td></tr><tr><td>Wavelength Dispersive X-ray Fluorescence spectroscope (WDXRF)</td><td>Malvern Panalytical</td><td>Zetium</td><td>To characterize elemental composition of soil.</td></tr><tr><td>X-ray Diffraction analyzer (XRD)</td><td>Panalytical</td><td>Empyrean</td><td>To characterize mineralogicalbproperties of soil.</td></tr></tbody></table>

monitoring pedogenic inorganic carbon accumulation due to weathering of amended silicate minerals in agricultural soils.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in agricultural soils. To this end, the core soil samples taken at different depth (including 0-15 cm, 15-30 cm, and 30-60 cm profiles) are collected from an agriculture field, the topsoil of which has already been enriched with an alkaline earth metal silicate containing mineral (such as wollastonite). After transporting to the laboratory, the soil samples are air-dried and sieved. Then, the inorganic carbon content of the samples is determined by a volumetric method called calcimetry. The representative results presented herein showed five folded increments of inorganic carbon content in the soils amended with the Ca-silicate compared to control soils. This compositional change was accompanied by more than 1 unit of pH increase in the amended soils, implying high dissolution of the silicate. Mineralogical and morphological analyses, as well as elemental composition, further corroborate the increase in the inorganic carbon content of silicate-amended soils. The sampling and analysis methods presented in this study can be adopted by researchers and professionals looking to trace pedogenic inorganic carbon changes in soils and subsoils, including those amended with other suitable silicate rocks such as basalt and olivine. These methods can also be exploited as tools for verifying soil inorganic carbon sequestration by private and governmental entities to certify and award carbon credits.

The SIC content of soils can be determined using various methods, including an automated carbon analyzer or a calcimeter. The automated carbon analyzer for total soil carbon determination measures the CO2 pressure built-up in a closed vessel30. In calcimetry, the evolved volume of CO2 released after acidification, typically by the addition of concentrated HCl acid, of the carbonate-containing sample is measured. The calcimetry method is relati...

Watch this Scientific Journal Video about Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils. at JoVE.com

Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils.

The verification method described here is adaptable for monitoring pedogenic inorganic carbon sequestration in various agricultural soils amended with alkaline earth metal silicate-containing rocks, such as wollastonite, basalt, and olivine. This type of validation is essential for carbon credit programs, which can benefit farmers that sequester carbon in their fields.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in ...

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5.0K Views.  University of Guelph. The verification method described here is adaptable for monitoring pedogenic inorganic carbon sequestration in various agricultural soils amended with alkaline earth metal silicate-containing rocks, such as wollastonite, basalt, and olivine. This type of validation is essential for carbon credit programs, which can benefit farmers that sequester carbon in their fields.

Video: Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils.

A CO2 Concentration Gradient Facility for Testing CO2 Enrichment and Soil Effects on Grassland Ecosystem Function

Continuing increases in atmospheric carbon dioxide concentrations (CA) mandate techniques for examining impacts on terrestrial ecosystems. Most experiments examine only two or a few levels of CA concentration and a single soil type, but if CA can be varied as a gradient from subambient to superambient concentrations on multiple soils, we can discern whether past ecosystem responses may continue linearly in the future and whether responses may vary across the landscape. The Lysimeter Carbon Dioxide Gradient Facility applies a 250 to 500 &#181;l L-1 CA gradient to Blackland prairie plant communities established on lysimeters containing clay, silty clay, and sandy soils. The gradient is created as photosynthesis by vegetation enclosed in in temperature-controlled chambers progressively depletes carbon dioxide from air flowing directionally through the chambers. Maintaining proper air flow rate, adequate photosynthetic capacity, and temperature control are critical to overcome the main limitations of the system, which are declining photosynthetic rates and increased water stress during summer. The facility is an economical alternative to other techniques of CA enrichment, successfully discerns the shape of ecosystem responses to subambient to superambient CA enrichment, and can be adapted to test for interactions of carbon dioxide with other greenhouse gases such as methane or ozone.

A CO2 Concentration Gradient Facility for Testing CO2 Enrichment and Soil Effects on Grassland Ecosystem Function

The Lysimeter Carbon Dioxide Gradient Facility creates a 250 to 500 &#181;l L-1 linear carbon dioxide gradient in temperature-controlled chambers housing grassland plant communities on clay, silty clay, and sandy soil monoliths. The facility is used to determine how past and future carbon dioxide levels affect grassland carbon cycling.

Continuing increases in atmospheric carbon dioxide concentrations (CA) mandate techniques for examining impacts on terrestrial ecosystems. Most ...

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate the environment. This radiocarbon signal &#8212; or rather the absence of signal &#8212; is evenly distributed throughout a contaminant source pool (unlike an added tracer) and is not impacted by biological, chemical or physical processes (e.g., the 14C radioactive decay rate is immutable). If the fossil-derived contaminant is fully degraded to CO2, a harmless end-product, that CO2 will contain no radiocarbon. CO2 derived from natural organic matter (NOM) degradation will reflect the NOM radiocarbon content (usually &#60;30,000 years old). Given a known radiocarbon content for NOM (a site background), a two end-member mixing model can be used to determine the CO2 derived from a fossil source in a given soil gas or groundwater sample. Coupling the percent CO2 derived from the contaminant with the CO2 respiration rate provides an estimate for the total amount of contaminant degraded per unit time. Finally, determining a zone of influence (ZOI) representing the volume from which site CO2 is collected allows determining the contaminant degradation per unit time and volume. Along with estimates for total contaminant mass, this can ultimately be used to calculate time-to-remediate or otherwise used by site managers for decision-making.

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

A protocol is described wherein CO2 mineralized from organic contaminant (derived from petroleum feedstocks) biodegradation is trapped, quantified, and analyzed for 14C content. A model is developed to determine CO2 capture zone's spatial extent. Spatial and temporal measurements allow integrating contaminant mineralization rates for predicting remediation extent and time.

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate ...

Assessment of Labile Organic Carbon in Soil Using Sequential Fumigation Incubation Procedures

Management practices and environmental changes can alter soil nutrient and carbon cycling. Soil labile organic carbon, a readily decomposable C pool, is highly sensitive to disturbance. It is also the primary substrate for soil microorganisms, which is fundamental to nutrient cycling. Due to these attributes, labile organic carbon (LOC) has been identified as an indicator parameter for soil health. Quantifying the turnover rate of LOC also aids in understanding changes in soil nutrient cycling processes. A sequential fumigation incubation method has been developed to estimate soil LOC and potential C turnover rate. The method requires fumigating soil samples and quantifying CO2-C respired during a 10 day incubation period over a series of fumigation-incubation cycles. Labile organic C and potential C turnover rate are then extrapolated from accumulated CO2 with a negative exponential model. Procedures for conducting this method are described.

Labile organic carbon (LOC) and the potential carbon turnover rate are sensitive indicators of changes in soil nutrient cycling processes. Details are provided for a method based on fumigating and incubating soil in a series of cycles and using the CO2 accumulated during the incubation periods to estimate these parameters.

Management practices and environmental changes can alter soil nutrient and carbon cycling. Soil labile organic carbon, a readily decomposable C pool, is ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it regulates the gravity-driven soil movement induced by runoff and tillage activities. The recent application of Light Detection and Ranging (LiDAR) data holds promise for generating high spatial resolution topographic metrics that can be used to investigate soil property variability. In this study, fifteen topographic metrics derived from LiDAR data were used to investigate topographic impacts on redistribution of soil and spatial distribution of soil organic carbon (SOC). Specifically, we explored the use of topographic principal components (TPCs) for characterizing topography metrics and stepwise principal component regression (SPCR) to develop topography-based soil erosion and SOC models at site and watershed scales. Performance of SPCR models was evaluated against stepwise ordinary least square regression (SOLSR) models. Results showed that SPCR models outperformed SOLSR models in predicting soil redistribution rates and SOC density at different spatial scales. Use of TPCs removes potential collinearity between individual input variables, and dimensionality reduction by principal component analysis (PCA) diminishes the risk of overfitting the prediction models. This study proposes a new approach for modeling soil redistribution across various spatial scales. For one application, access to private lands is often limited, and the need to extrapolate findings from representative study sites to larger settings that include private lands can be important.

Landscape processes are critical components of soil formation and play important roles in determining soil properties and spatial structure in landscapes. We propose a new approach using stepwise principal component regression to predict soil redistribution and soil organic carbon across various spatial scales.

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF relies on sequential density separation and sedimentation steps to isolate (1) the free light fraction (uncomplexed organic matter), (2) the occluded light fraction (uncomplexed organic matter trapped in soil aggregates) and (3) a variable number of heavy fractions (soil minerals and their associated organic matter) differing in composition. Provided that the parameters of the CSDF (dispersion energy, density cut-offs, sedimentation time) are properly selected, the method yields heavy fractions of relatively homogeneous mineral composition. Each of these fractions is expected to have a different complexing ability towards organic matter, rendering this a useful method to isolate and study the nature of organo-mineral interactions. Combining density and particle size separation brings an improved resolution compared to simple size or density fractionation methods, allowing the separation of heavy components according to both mineralogy and size (related to surface area) criteria. As is the case for all physical fractionation methods, it may be considered as less disruptive or aggressive than chemically-based extraction methods. However, CSDF is a time-consuming method and furthermore, the quantity of material obtained in some fractions can be limiting for subsequent analysis. Following CSDF, the fractions may be analyzed for mineralogical composition, soil organic carbon concentration and organic matter chemistry. The method provides quantitative information about organic carbon distribution within a soil sample and brings light to the sorptive capacity of the different, naturally-occurring mineral phases, thus providing mechanistic information about the preferential nature of organo-mineral interactions in soils (i.e., which minerals, what type of organic matter).

Combined size and density fractionation (CSDF) is a method to physically separate soil into fractions differing in texture (particle size) and mineralogy (density). The purpose is to isolate fractions with different reactivities towards soil organic matter (SOM), in order to better understand organo-mineral interactions and SOM dynamics.

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF ...

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures

Natural organic matter (NOM) is composed of a highly complex mixture of thousands of organic compounds which, historically, proved difficult to characterize. However, to understand the thermodynamic and kinetic controls on greenhouse gas (carbon dioxide [CO2] and methane [CH4]) production resulting from the decomposition of NOM, a molecular-level characterization coupled with microbial proteome analyses is necessary. Further, climate and environmental changes are expected to perturb natural ecosystems, potentially upsetting complex interactions that influence both the supply of organic matter substrates and the microorganisms performing the transformations. A detailed molecular characterization of the organic matter, microbial proteomics, and the pathways and transformations by which organic matter is decomposed will be necessary to predict the direction and magnitude of the effects of environmental changes. This article describes a methodological throughput for comprehensive metabolite characterization in a single sample by direct injection Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), gas chromatography mass spectrometry (GC-MS), nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography mass spectrometry (LC-MS), and proteomics analysis. This approach results in a fully-paired dataset which improves statistical confidence for inferring pathways of organic matter decomposition, the resulting CO2 and CH4 production rates, and their responses to environmental perturbation. Herein we present results of applying this method to NOM samples collected from peatlands; however, the protocol is applicable to any NOM sample (e.g., peat, forested soils, marine sediments, etc.).

This protocol describes a single throughput for complementary analytical and omics techniques culminating in a fully-paired characterization of natural organic matter and microbial proteomics in different ecosystems. This approach permits robust comparisons for identifying metabolic pathways and transformations important for describing greenhouse gas production and predicting responses to environmental change.

Natural organic matter (NOM) is composed of a highly complex mixture of thousands of organic compounds which, historically, proved difficult to ...

Carbon Sequestration and Soil Enhancement Through Onsite Biochar Production

Producing, Characterizing and Quantifying Biochar in the Woods Using Portable Flame Cap Kilns

One of the biggest challenges in utilizing non-commercial forest biomass is its widely distributed nature. The best solution to the biomass problem, to avoid expensive and carbon-intensive processing (chipping) and transportation costs, is to process it onsite. However, conventional burn piles have destructive impacts on forest soil and provide no benefits other than fuel reduction. Converting forest slash to biochar onsite has many ecological advantages over the current practice of slash disposal by incineration in burn piles, including reduced soil heating and particulate emissions, along with multiple benefits of the biochar to forest soil health and water holding capacity when left in place. Making biochar onsite in the woods is a way to return a pyrogenic carbon component to forest soils that has been missing due to the recent history of fire suppression. Biochar is also a leading method of carbon removal and sequestration for climate change mitigation. In this study, we document a method for making biochar using a portable biochar kiln. This low-cost method utilizes hand crews equipped with water for quenching kilns before the biochar burns to ash. Simple techniques for quantifying and characterizing the biochar produced are incorporated into the method for the purpose of measuring impact and qualifying for carbon removal certificates to help pay for the cost of the work. We describe the CM002 Component Methodology that provides standardized procedures for the quantification of GHG benefits during three stages of the process: waste biomass sourcing, biochar production, and biochar soil application. The CM002 Methodology is based on international best practices, including the most recent VCS methodology VM0044 Standards and EBC C-Sink Artisan Standards. Reliable quantification methods utilizing appropriate safety factors are the first essential step toward eligibility for carbon removal finance.

Author Spotlight: On-Site Biochar Production for Woody Debris Incineration in Forestry 

New methods for disposing of forestry slash piles in place produce pyrogenic carbon for restoring forest soil health and for carbon removal and sequestration. Here, we present a biochar production method integrating a new carbon removal accounting methodology and a digital application.

One of the biggest challenges in utilizing non-commercial forest biomass is its widely distributed nature. The best solution to the biomass problem, to ...

Sandy Soil Improvement through Microbially Induced Calcite Precipitation (MICP) by Immersion

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch reactor was assembled to immerse soil samples into cementation media. The cementation media can freely diffuse into the soil samples in the batch reactor instead of cementation media being injected. A full contact flexible mold, a rigid full contact mold, and a cored brick mold were used to prepare different soil sample holders. Synthetic fibers and natural fibers were selected to reinforce the MICP-treated soil samples. The precipitated CaCO3 in different areas of the MICP-treated samples was measured. The CaCO3 distribution results demonstrated that the precipitated CaCO3 was distributed uniformly in the soil sample by the immersion method.

Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion

Here, microbially induced calcite precipitation (MICP) technology is presented to improve soil properties by immersion.

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch ...

Engineering

Impregnation and Grafting of Aminated Compounds onto Silica Substrates

A Synthetic Methodology for Preparing Impregnated and Grafted Amine-Based Silica Composites for Carbon Capture

Recently, there has been a significant effort towards reducing or mitigating CO2 emissions through the use of carbon capture materials for point source or direct air capture (DAC) methods. This work focuses on amine-functionalized CO2 adsorbents for DAC. These materials show promise for CO2 removal because they have low regeneration energy consumption and high adsorption capacity. The incorporation of amine species into a porous substrate combines the advantages of the amine species&#39; affinity to CO2 with the large pore volumes and surface areas of the porous substrate. There are three methods commonly used to prepare amine-based CO2 sorbents, depending on the selection of the amine species, material support, and preparation method. These methods are impregnation, grafting, or chemical synthesis. Silica is a prevalent choice of substrate material because of its adjustable pore size, moisture tolerance, temperature stability, and ability to adsorb CO2 in low concentrations for DAC applications. Typical synthetic procedures and primary attributes of both impregnated and grafted amine-silica composites are described herein.

Author Spotlight: Standardizing the Development of Amine-Based Silica Composites as CO2 Adsorbents for Direct Air Capture 

This work aims to facilitate the development of standardized techniques for impregnating or grafting aminated compounds onto silica substrates, which are often broadly described in the literature. Specific amounts of solvent, substrate, amines, and the values of other important experimental parameters will be discussed in detail.

Recently, there has been a significant effort towards reducing or mitigating CO2 emissions through the use of carbon capture materials for point source or ...

Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils.

Summary

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