Soil chemistry
Encyclopedia
Soil chemistry is the study of the chemical
characteristics of soil
. Soil chemistry is affected by mineral
composition, organic matter
and environmental
factors.
or that affect plant growth. Since then, concerns have grown about environmental pollution
, organic and inorganic soil contamination
and potential ecological health
and environmental health
risks. Consequently, the emphasis in soil chemistry has shifted from pedology
and agricultural soil science
to an emphasis on environmental soil science
.
chemistry is paramount to predicting the fate, mobility and potential toxicity
of contaminants in the environment. The vast majority of environmental contaminants are initially released to the soil. Once a chemical is exposed to the soil environment a myriad of chemical reaction
s can occur that may increase or decrease contaminant toxicity. These reactions include adsorption
/desorption
, precipitation
, polymerization
, dissolution
, complexation and oxidation/reduction
. These reactions are often disregarded by scientists and engineers involved with environmental remediation. 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.
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
characteristics of soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
. Soil chemistry is affected by mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
composition, organic matter
Organic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
and environmental
Environment (biophysical)
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...
factors.
History
Until the late 1960s, soil chemistry focused primarily on chemical reactions in the soil that contribute to pedogenesisPedogenesis
Pedogenesis is the science and study of the processes that lead to the formation of soil ' and first explored by the Russian geologist Vasily Dokuchaev , the so called grandfather of soil science, who determined that soil formed over time as a consequence of...
or that affect plant growth. Since then, concerns have grown about environmental pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
, organic and inorganic soil contamination
Soil contamination
Soil contamination or soil pollution is caused by the presence of xenobiotic chemicals or other alteration in the natural soil environment....
and potential ecological health
Ecological health
Ecological health or ecological integrity or ecological damage are the symptoms of an ecosystem's pending loss of carrying capacity, its ability to perform ecological services, or a pending ecocide, due to cumulative causes such as pollution. it can also be defined as farming so as to minimize the...
and environmental health
Environmental health
Environmental health is the branch of public health that is concerned with all aspects of the natural and built environment that may affect human health...
risks. Consequently, the emphasis in soil chemistry has shifted from pedology
Pedology
Pedology may refer to:*Pedology *Pedology *Pediatrics...
and agricultural soil science
Agricultural soil science
Agricultural soil science is a branch of soil science that deals with the study of edaphic conditions as they relate to the production of food and fiber. In this context, it is also a constituent of the field of agronomy.-History:...
to an emphasis on environmental soil science
Environmental soil science
Environmental soil science is the study of the interaction of humans with the pedosphere as well as critical aspects of the biosphere, the lithosphere, the hydrosphere, and the atmosphere...
.
Environmental soil chemistry
A knowledge of environmental soilEnvironmental soil science
Environmental soil science is the study of the interaction of humans with the pedosphere as well as critical aspects of the biosphere, the lithosphere, the hydrosphere, and the atmosphere...
chemistry is paramount to predicting the fate, mobility and potential toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
of contaminants in the environment. The vast majority of environmental contaminants are initially released to the soil. Once a chemical is exposed to the soil environment a myriad of chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
s can occur that may increase or decrease contaminant toxicity. These reactions include adsorption
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
/desorption
Desorption
Desorption is a phenomenon whereby a substance is released from or through a surface. The process is the opposite of sorption . This occurs in a system being in the state of sorption equilibrium between bulk phase and an adsorbing surface...
, precipitation
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
, polymerization
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
, dissolution
Solvation
Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...
, complexation and oxidation/reduction
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
. These reactions are often disregarded by scientists and engineers involved with environmental remediation. 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.
Concepts
- Anion and cation exchange capacityCation exchange capacityIn soil science, cation-exchange capacity is the maximum quantity of total cations, of any class, that a soil is capable of holding, at a given pH value, for exchanging with the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect...
- Soil pHSoil pHThe soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
- Mineral formation and transformation processes
- ClayClayClay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
mineralogyMineralogyMineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing... - Sorption and precipitationPrecipitation (chemistry)Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
reactions in soil - Oxidation-reductionRedoxRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
reactions - Chemistry of problem soils