Environmental Science – Biogeochemical cycles

Welcome back to our environmental science series! Today we will be talking about biogeochemical cycles, the biological, chemical, and geological ways chemicals move through our planet’s systems and is reused/recycled.

This talk is going to be more visual than textual. Understanding these cycles is important because it shows us how vital chemicals are recycled and used on our planet. We will go over the Water, Carbon, Nitrogen, Sulfur, and Phosphorous Cycles.

The Water Cycle:

This cycle is important because it collects freshwater, fixes polluted water and replenishes areas with water promoting life. Evaporation is when water is heated and rises as water vapor, only to condense in the air due to colder temperatures, and then releasing the pressure as a liquid through precipitation. Precipitated water runs off back into streams, rivers, lakes, or marine ecosystems. Sometimes water can enter the ground as well, entering aquifers which are natural underground water purifiers using rocks. Transpiration is when excess water leaves the stomata openings in plant leaves as a gas.

The Carbon Cycle:

Carbon is the main component of life. It is key in photosynthesis as well as cellular respiration, two major cellular processes in living organisms. Once plants and animals die and decay they restore the carbon into the soil, and in millions of years this carbon soil becomes what we know as fossil fuels. Humans affect this cycle by burning fossil fuels in factories and causing air pollution, increasing the carbon content in the atmosphere as CO2. The largest sink of carbon in the ocean, where CO2 is dissolved with calcium, and the largest source of carbon are fossil fuels.

The Sulfur cycle:

Sulfur begins as SO2 gas from volcano eruption and factories. It makes rain acidic, and rains as H2SO3 or H2SO4 and is absorbed by plants. Once they decompose they become fossil fuels or dissolve into ocean systems where bacteria convert it to dimethyl sulfide, where it can rise again as a gas. It can be stored as gypsum or pyrite in the Lithosphere.

The Phosphorous Cycle:

Phosphorous is the only cycle which is not atmospheric. Phosphorous begins by rocks that have been weathered through events such as erosion, precipitation, runoff, or drilling. It gets drained into water systems and absorbed by plant roots. Once plants decompose they leave phosphate as sediment in the soil. This phosphate can also keep going down the river systems and turn to the sediment layer at the bottom of large aquatic ecosystems. The sediment gets compacted or heated and then gets uplifted as rocks, restarting the whole cycle. Humans affect this cycle by adding phosphate to fertilizer, which gets runoff into water systems causing eutrophication, massive algal blooms, which use up all the oxygen in aquatic habitats and kills the ecosystems. This cycle is very, very long because it takes a lot of time for rocks to erode, uplift, and compact.

The Nitrogen Cycle:

The important thing to know about this cycle is that it is bacteria dependent. Without bacteria, this cycle would not work. Nitrogen fixation, ammonification, nitrification, and denitrification are all processes run by bacteria in the soil. Each process is different from the bacteria that run the process and the reactants and products. Remembering this diagram is the best way to have a basic understanding of each process. The largest sink of Nitrogen is the atmosphere.

Both phosphorous and nitrogen are limiting factors, meaning that they are limited by processes, and limit characteristics of ecosystems. They both are significant in the formation of important organic molecules such as nucleic acids and Adenosine Triphosphate (ATP). Animals obtain many of these nutrients through eating other organisms, while plants get these nutrients by absorbing them from the soil with their roots.

That is it for this talk! In the next talk, we will talk about the relationships between organisms. Remember to try to save the environment every day! Comment if you have any questions and stay tuned for more talks on interesting topics. 

-Written By: Neil D. 3/4/2019


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