Biogeochemical Cycle

Abiogeochemical cycle refers to the cycling and transport of a chemical element or compound, usually in multiple forms and physical states, through the biotic (living) and abiotic (nonliving) components of the earth system. Some of the most commonly examined biogeochemical cycles include carbon, nitrogen, oxygen, water, and phosphorous, which are highly interdependent and connected to both the physical environment and human activity. Biogeochemical processes include cycling to and from living organisms in the biosphere, rock minerals in the lithosphere, hydrological processes in the hydrosphere, and air circulation in the atmosphere, making the spatial and temporal variability of biogeochemical cycles quite complex. Biogeochemistry attempts to understand the physical processes that control and make up these cycles, as well as the natural and anthropogenically-induced variation in these cycles, including potentially harmful alterations. Humans depend upon biogeochemical cycles for, among other things, food production, water supplies, and oxygen, so the dynamics and disturbances of these processes are a major concern for environmental scientists and policymakers. Similarly, concerns related to global warming, air pollution, and biodiversity also require an understanding of biogeochemical cycles, as well as their interaction with humans and human activity across the world.

Biogeochemistry is an interdisciplinary science because it requires knowledge of living and nonliving processes that occur at various temporal and spatial scales in all components of the earth system, including the world's oceans, forests, and urban areas. A biogeochemical cycle may include the occurrence of pools or sinks (where an element or compound is stored for longer periods) and sources (where an element or compound is freed from a sink, often in a short time and in relatively large quantities). Both human and nonhuman processes and activities (such as fire) may alter the spatial and temporal cycling of elements such as carbon and oxygen from sources and sinks, which can make it difficult to clearly distinguish “natural” and “human” perturbations of biogeochemical cycles. Furthermore, biogeochemical cycles occur and can be altered at a range scale from molecular to global, making it challenging to study entire biogeochemical cycles at one time. As a result, biogeochemistry examines past, current, and future time scales though the use of paleo-ecology, physical science, and statistical modeling.