The effects of enhanced weathering and hydrology on carbon sequestration in soils
Authors: Cipolla Giuseppe , Calabrese Salvatore , Noto Leonardo Valerio , Porporato Amilcare 
Published: May 2023

&lt;p&gt;The impacts of climate change, mainly due to the use of fossil fuels, have been rising over the last decades. To address this problem, the scientific community is currently making a big effort, coming up with several solutions aiming to reduce greenhouse gas emissions or to sequester the carbon within the atmospheric CO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt;&lt;p&gt;In this context, &lt;strong&gt;Enhanced chemical weathering &lt;/strong&gt;is included in the group of &lt;em&gt;carbon sequestration&lt;/em&gt; technologies. These techniques involve removing CO&lt;sub&gt;2&lt;/sub&gt; from the atmosphere and storing the carbon within it in the oceans, terrestrial environments or geologic formations. The natural &lt;strong&gt;chemical weathering &lt;/strong&gt;is the main process of soil formation, since it is the ensemble of the chemical/biochemical reactions leading to the alteration of primary minerals, thus to the formation of secondary minerals. The &lt;strong&gt;Enhanced chemical weathering &lt;/strong&gt;consists of increasing the natural weathering reaction rates, by adding some highly reactive minerals to the soil. It is widely known that weathering rates are higher under warm and humid climate conditions and high soil acidity.&lt;/p&gt;&lt;p&gt;The present study evaluates the effects of Forsterite, a common silicate mineral also known as Mg-olivine, on soil carbon sequestration. This mineral is recognized by many studies as the best solution for &lt;strong&gt;Enhanced weathering &lt;/strong&gt;applications since it is available in many parts of the world and its reaction rates with CO&lt;sub&gt;2&lt;/sub&gt; are much higher than those of other minerals. In this study, a model simulating the dynamics of the biogeochemistry of a soil treated with olivine under different climate scenarios is presented. The model is forced by a stochastic rainfall, simulated as a marked Poisson process, and puts together the ecohydrology and the biogeochemistry. Plants influence the whole system with their evapotranspiration, nutrients uptake (Na&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt; and Mg&lt;sup&gt;2+&lt;/sup&gt;) and the addition of organic matter to the soil. Biogeochemistry involves all the aspects of the model related to the cycle of the dissolved ions (H&lt;sup&gt;+&lt;/sup&gt;, Na&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt; and Mg&lt;sup&gt;2+&lt;/sup&gt;), litter decomposition and the chemical reaction of olivine with CO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt;&lt;p&gt;Running the model under different climate scenarios highlights that the highest olivine weathering rates are assessed under wet conditions. This happens because high soil moisture leads to higher reactive surface areas of particles and higher dissolution rates. This aspect is emphasized from the fact that soil pH is lower in humid than in dry environments and weathering reaction rates are higher in acid conditions since hydrogen ions are the reactants of many weathering reactions. The study also attempts to evaluate the economic feasibility of the intervention in agricultural fields. Apart from the costs of performing this kind of intervention, some benefits should be taken into account. More specifically, spreading olivine on agricultural fields leads to an increase of Na&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt; and Mg&lt;sup&gt;2+&lt;/sup&gt; concentrations, thus a certain amount of olivine can replace the addition of fertilizers. Therefore, this study proposes a natural solution for facing climate change problems and presents a model that could be used as a decision support system in land management.&lt;/p&gt;