Biogeochemical cycles are processes that occur in nature to ensure the recycling of chemical elements in the environment.
It is these cycles that allow elements to interact with the environment and with living beings, that is, ensuring that the element flows through the atmosphere, hydrosphere, lithosphere and biosphere.
The main biogeochemical cycles found in nature are the water, carbon, oxygen and nitrogen cycles.
Types of biogeochemical cycles and characteristics
Biogeochemical cycle of water
Water is an element that moves and transforms all the time. Therefore, we can find it in nature in three states: solid, liquid and gaseous.
The biogeochemical cycle of water is characterized exactly by its change in physical state. Let’s see how it happens, in stages:
- In the first stage, the evaporation of water from rivers, lakes and oceans goes hand in hand with the transpiration of water, present in plants.
- After evaporation and transpiration, water (in the gaseous state) passes to the clouds, where condensation occurs, that is, the transformation to the liquid state.
- With the accumulation of water droplets that formed in condensation, water precipitation occurs and, consequently, rain returns it to rivers, lakes, oceans and soils.
Nitrogen biogeochemical cycle
The biogeochemical nitrogen cycle begins with nitrogen in its gaseous form (N2) present in the environment. At this point, it is important that the nitrogen is fixed in the soil, that is, that the soil absorbs it.
This process is called fixation and it occurs thanks to the help of bacteria and cyanobacteria that are present in the soil.
With the nitrogen already fixed in the soil, the next step is to transform it into ammonia, a process called ammonification. The ammonia produced will be absorbed by bacteria that generate nitrites, and this step is called nitrification.
Nitrites will produce nitrates, which will be used in the assimilation process so that plants can synthesize proteins, and will also be used in denitrification, which is nothing more than the return of nitrogen to the environment.
The sequences of this cycle are:
- Fixation
- Ammonification
- Nitrification
- Denitrification
Observation: assimilation into plants is an event that occurs as a consequence of the cycle, that is, it does not take place within the cycle.
Biogeochemical oxygen cycle
First of all, it is important to remember that oxygen is part of organic and inorganic molecules.
The biogeochemical oxygen cycle begins in photosynthesis, when the plant absorbs CO2, producing oxygen that will be released into the atmosphere.
This oxygen that is present in the atmosphere is absorbed by animals and humans. In addition, it can also participate in the decomposition process and burning of fossil fuels.
These two processes will generate and release CO2 into the atmosphere that will be used in photosynthesis, resuming the cycle.
Phosphorus biogeochemical cycle
Phosphorus is an element that is present in the genetic material and in the molecule that provides us with energy: adenosine triphosphate, or simply ATP.
The biogeochemical cycle of phosphorus occurs in soils, plants and animals. To begin with, plants absorb it from the soil and water. Animals and humans, on the other hand, obtain phosphorus through food.
When living things die and decompose, phosphorus is returned to the soil and water, thus renewing the cycle.
Sulfur biogeochemical cycle
Sulfur is an essential element in the life of living beings, because it participates in the composition of our amino acids for the production of proteins in our body.
This element is found in rock sediments and soil, where it is absorbed by plants with the help of bacteria and then dissolved in water.
This water evaporates, turning into acid rain and returning sulfur to the soil, sequencing the biogeochemical cycle of sulfur.
Importance
Biogeochemical cycles are very important for living beings because they carry out the exchange of these elements between the environment and living beings, helping to maintain life. They also prevent these elements from ending up in Earth’s nature.
Biogeochemical cycles promote the cycling of elements, ensuring their use and, subsequently, their availability. This is a factor of great importance, because some elements are essential for living beings, and their constant use, without replacement, could cause the extinction of species.
Furthermore, decomposing agents have the important role of restarting cycles, returning elements to the ecosystem and maintaining continuous flow.