Biogeochemical Cycles (Environmental Chemistry)
Biogeochemical cycles trace how elements move and transform among the atmosphere, hydrosphere, lithosphere, and biosphere, linking chemistry, biology, and geology at the planetary scale.
Definition
The study of the cyclical movement and chemical transformation of elements through Earth's environmental compartments and living organisms, treated from a chemical perspective.
Scope
This area covers the global cycles of carbon, nitrogen, phosphorus, sulfur, and trace elements, including the reservoirs, fluxes, and chemical transformations that connect them. Within environmental chemistry the emphasis is on the chemical reactions and oxidation-state changes that drive the cycles and on how human activity has perturbed them.
Sub-topics
Core questions
- What are the major reservoirs and fluxes of each element?
- Which chemical and microbial transformations drive each cycle?
- How are the cycles coupled to one another and to climate?
- How have human activities altered global element cycles?
Key theories
- Reservoir-flux model of element cycling
- Each element's global cycle is represented as reservoirs connected by fluxes; quantifying these and their perturbation by human activity allows assessment of imbalances such as the buildup of atmospheric carbon dioxide.
- Coupling of biogeochemical cycles
- The carbon, nitrogen, and phosphorus cycles are linked through the stoichiometry of biological production, so perturbing one cycle propagates through the others.
Mechanisms
Cycles are organized as reservoirs joined by fluxes mediated by photosynthesis, respiration, weathering, deposition, and human inputs. Microbial redox reactions interconvert oxidation states, while biological stoichiometry ties the cycles together, making them respond jointly to disturbance.
Clinical relevance
Biogeochemical cycling underpins climate change, eutrophication, and air- and water-quality problems, and it frames the planetary-scale consequences of fossil-fuel use and fertilizer production.
History
Biogeochemistry traces to Vernadsky's concept of the biosphere and Hutchinson's quantitative cycle analyses, maturing into a global-change science as human perturbations of the carbon and nitrogen cycles became measurable.
Key figures
- Vladimir Vernadsky
- G. Evelyn Hutchinson
- William H. Schlesinger
Related topics
Seminal works
- schlesinger2013
- falkowski2000
- galloway2008
Frequently asked questions
- How does this relate to biogeochemical cycles in ecology?
- It treats the same global cycles but emphasizes the chemical reactions and oxidation-state changes, complementing the ecosystem-ecology view of pools, fluxes, and organisms.