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Summary

Environment Class 05

## A BRIEF OVERVIEW OF THE PREVIOUS CLASS: (01:06:00 PM)

- Biogeochemical Cycles.

## SULFUR CYCLE: (01:11:00 PM)

- Sulfur is a very important macronutrient in plants.
- Plats directly take a very small amount from the air in the form of sulfur dioxide(SO2).
- However, the major source is sulfate Ions from the soil.
- Note:
- **Gaseous Cycle:**
- Whenever an element is taken by the life forms in the form of gases, and it majorly moves through the gases in the ecosystem, then it is called a gaseous cycle.
- For example, Carbon, Water Cycle, etc.
- **Sedimentary Cycle:**
- Whenever an element is taken by the life forms in the solid form, and it majorly moves through the solid states in the ecosystem, then it is called a sedimentary cycle.
- **Pool:**
- It is a body in which an element is present in a concentrated form in an ecosystem.
- For example, rocks, water bodies, soil, and atmosphere are examples of pools.
- **Sources of Sulfur:**
- Volcanic Eruption- Volcanic eruption releases Sulfur, H2S, and SO2 in the environment.
- Minerals and rocks-  for example, Pyrite(FeS2, Fool's Gold)
- Chemical Actions in rock -> SO2 to the atmosphere.
- Bruning of fossil fuels -> SO2, H2S, etc.
- Industries like oil refineries, Paper, & chemical industries release huge amounts of H2S.
- Forest fires release Ammonium Sulfate.
- Mycorrhiza fungi which are attached to the plant's roots decompose dead plant or animal material and release sulfate ion that is taken by the plant's roots.
- Aspergillus is one very important fungi in decomposing organic matter( dead plant or animal material).
- Decay of dead plant or animal material -> Hydrogen sulfide(H2S).
- Bacterias convert this H2S to Sulfate Ions. Most important bacteria is Thiobacillus.
- Sulfate ions can be reconverted into H2S by another class of bacteria like Salmonella.
- H2S reacts with Oxygen in the atmosphere to produce SO2 which then can react with water/snow and come to the ground as Sulfuric Acid -> Wet Deposit.
- SO2 can also react with Oxygen to produce Supfate ions which come directly as dust to the surface known as Dry Deposit.
- Sulfate reacts with water and forms Sulfide which is absorbed by rocks or minerals and deposited.

## NITROGEN CYCLE: (02:22:00 PM)

- Nitrogen molecules are very stable and can't be taken by life forms directly from the atmosphere.
- N2 is a chemically inert gas.
- Nitrogen is very important for living beings as it is required in pricing Amino acids, DNA, etc.
- Nitrate Ions(NO3) Ions are the most important form which is taken up by living beings.
- **Sources of Nitrogen to the Atmosphere:**
- Volcanic eruptions- Oxides of Nitrogen.
- Bacterial decomposition of plants and animal material -> Oxides of Nitrogen mainly N2O(Nitrous Oxide) and NO(Nitric Oxide).
- Breakdown of nitrogenous fertilizers ->  Oxides of Nitrogen.
- Fossil Fuel burnings(Minaly automobile exhaust) produce N2O(Nitrous Oxide) and NO(Nitric Oxide).
- Coal Burning -> Most importantly NO(Nitirc Oxide).
- **By lightening:**
- N2+ O2 -> Oxides of Nitrogen -> Nitrate (NO3-) -> Settles on Earth's surface as dust- Dry deposition.
- Nitrate + Water -> HNO3(Ntiric Acid) comes with rain - Wet deposition.
- **Nitrogen Fixation:**
- It is the production of Ammonia(NH3) or Ammonium(NH4-) by the nitrogen-fixing bacteria & algae which decompose dead animal and plant matter.
- These microorganisms are close to the roots of the plants to get their carbon which is released by plant roots.
- When these algae and bacteria decompose dead organic matter  Ammonia(NH3) or Ammonium(NH4-) are produced.
- Algae Like Nostoc and Bacteria like Azaztobacter, Clostridium produce Ammonia(NH3) or Ammonium(NH4-).
- **Nitrification:**
- Biological conversion of Ammonia(NH3) or Ammonium(NH4-) into Nitrite(NO2-) and Nitrates(NO3-).
- Ammonia is first converted into Nitrite(NO2-) by bacteria like Nitrococus & Nitrosomonas.
- Then Nitrite(NO2-) is converted into Nitrate(NO3-) by a bacteria Nitrobactor -> Plants -> Animals.
- Immobilization- It s when the nitrates are taken up by the rocks or minerals.
- **Denitrification:**
- It is the biological conversion of Nitrate into Nitrogen (N2) by a sequence of stages.
- It is done by a bacteria called Pseudomonas.
- Nitrates(NO3-) -> Nitrite(NO2-) -> Nitirc Oxide(NO) -> Dinitrogen(N2).

## CARBON CYCLE: (03:38:00 PM)

- Carbon is one of the most important elements of organic life.
- A very small amount of Carbon(only about 2% of the total Carbon) is part of the Biogeochemical cycle.
- **Sources of Carbon:**
- Breakdown of rocks & release of CO2.
- Volcanic eruptions.
- Decay and decomposition of organic materials.
- Combustion of fossil fuels.
- Respiration by animals and plants.
- Forest fires. etc.
- **Carbon is removed from the atmosphere by:**
- Formation of Coal deposits.
- Absorption by water and ice.
- Photosynthesis by Plants.
- **Oxygen Cycle:**
- 99.5% of the total Oxygen by mass is locked in the Earth's Crust.
- Only 0.5% of the Oxygen is present in the atmosphere.
- **Sources of Oxygen:**
- Breakdown of minerals.
- Release by Plants during Photosynthesis.
- Volcanic Activity.
- Photolysis of water by UV rays. etc.
- **Removal of Oxygen:**
- Respiration by plants & animals.
- All combustion processes.
- Absorption by water bodies, etc.

## TOPICS FOR THE NEXT CLASS:

Ecological Succession, Biomes, etc.