Soil chemistry
Understanding these processes enable us to better predict the fate and toxicity of contaminants and provide the knowledge to develop scientifically correct, and cost-effective remediation strategies.
The presence of oxygen in the soil is important because it helps in breaking down insoluble rocky mass into soluble minerals and organic humification.
Silt particles allow water and air to pass readily, yet retain moisture for crop growth.
Biota rely on inputs of organic matter in order to sustain themselves and increase population sizes.
With the many different interactions that take place, biota can largely impact their environment physically, chemically, and biologically (Pavao-Zuckerman, 2008).
A prominent factor that helps to provide some degree of stability with these interactions is biodiversity, a key component of all ecological communities.
Biodiversity allows for a consistent flow of energy through trophic levels and strongly influences the structure of ecological communities in the soil.
Types of living soil biota can be divided into categories of plants (flora), animals (fauna), and microorganisms.
Vegetative cover on the soil surface greatly reduces erosion, which in turn prevents compaction and helps to maintain aeration in the soil pore space, providing oxygen and carbon to the biota and cation exchange sites that depend on it.
Animals are essential to soil chemistry, as they regulate the cycling of nutrients and energy into different forms.
Given the significance of the effects of microbes on their environment, the conservation and promotion of microbial life is often desired by many plant growers, conservationists, and ecologists.
The chief elements found in humus, the product of organic matter decomposition in soil, are carbon, hydrogen, oxygen, sulphur and nitrogen.
Humus is a dynamic product and is constantly changing because of its oxidation, reduction and hydrolysis; hence, it has much carbon content and less nitrogen.
These cycles are influenced by water, gas exchange, biological activity, immobilization, and mineralization dynamics, but each element has its own course of flow (Deemy et al., 2022).
In many cases, the soil samples are air dried at ambient temperatures (e.g., 25 °C (77 °F)) and sieved to a 2 mm size prior to storage for further study.
Such drying and sieving soil samples markedly disrupts soil structure, microbial population diversity, and chemical properties related to pH, oxidation-reduction status, manganese oxidation state, and dissolved organic matter; among other properties.
The soil slurry then is shaken or swirled for a given amount of time (e.g., 15 minutes to many hours) to establish a steady state or equilibrium condition prior to filtering or centrifuging at high speed to separate sand grains, silt particles, and clay colloids from the equilibrated solution.
In each case, the analysis quantifies the concentration or activity of an ion or molecule in the solution phase, and by multiplying the measured concentration or activity (e.g., in mg ion/mL) by the solution-to-soil ratio (mL of extraction solution/g soil), the chemist obtains the result in mg ion/g soil.
A related approach uses a known volume to solution to leach (infiltrate) the extracting solution through a quantity of soil in small columns at a controlled rate to simulate how rain, snow meltwater, and irrigation water pass through soils in the field.
[11] These laboratory experiments and analyses have an advantage over field studies in that chemical mechanisms on how ions and molecules react in soils can be inferred from the data.
One can draw conclusions or frame new hypotheses on similar reactions in different soils with diverse textures, organic matter contents, types of clay minerals and oxides, pH, and drainage condition.
