Module 1.3 Carbon Cycle in the Environment

Brief introduction of carbon cycle

1. CEE 298: Advanced Biological Treatment Dr. Shakira Hobbs Assistant Professors Civil & Environmental Engineering Module 1.4 –Carbon & Nitrogen Cycle Lecture 5: April 30, 2024 Battin , T., Luyssaert , S., Kaplan, L.  et al.  The boundless carbon cycle.  Nature Geosci   2 , 598–600 (2009). https:// doi.org /10.1038/ngeo618

2. Objective(s) for today: (1) Understand carbon & nitrogen cycle. (2)Demonstrate knowledge of carbon reservoirs, photosynthesis and decomposition, methane hydrates, carbon balances. (3) Identify the important roles and differences of nitrification and denitrification in the nitrogen cycle

3. Carbon Cycle On a global basis, carbon (C) cycles as CO 2 through all of Earth’s reservoirs: Atmosphere Land Oceans Freshwaters Sediment Rocks Biomass

4. Carbon cycle The carbon and oxygen cycles are closely linked Phototrophic organism are foundation of the carbon cycle Oxygenic phototrophic organism can be dived into two groups Plants Microorganism Plants dominate phototrophic organisms of terrestrial environments Phototrophic microbes dominate aquatic environments

5. Carbon cycle CO 2 in the atmosphere is the most rapid transferred carbon reservoir CO 2 is removed from the atmosphere primarily by photosynthetic land plants and marine microbes CO 2 is returned to the atmosphere by respiration of animals and chemoorganotrophic microbes as well as anthropogenic activities Microbial decomposition is the largest source of CO 2 released in the atmosphere

6. Key reactions for the Carbon Cycle Photosynthesis and respiration are reverse reactions Photosynthesis CO 2 + H 2 O  (CH 2 O) +O 2 Respiration (CH 2 O) + O 2  CO 2 + H 2 O

7. Single most contribution to CO2 to the atmosphere was microbial decomposition of organic material

8. Global warming

9. Photosynthesis and Decomposition Redox reaction in photosynthesis 6CO 2 + 6H 2 O  (C 6 H 12 O 6 ) + 6O 2 Hint: GER : G ain E lectrons R eduction LEO : L ose E lectrons O xidation goes Reduction Oxidation

10. Photosynthesis and Decomposition (redox cycle of C) CO 2 + H 2 O  (CH 2 O) +O 2 Photosynthesis (CH 2 O) + O 2  CO 2 + H 2 O Respiration Autotrophic (producers) Heterotrophic (consumers)

11. Decomposition Two major end products of decomposition are CH 4 and CO 2 On a global basis, biotic processes release more CH 4 than abiotic processes

12. Syntropy and Methanogenesis

13. Microbial Competition Metabolic cooperation can also be seen in activities of organism carrying out complementary metabolism Ex. Nitrifying prokaroytes oxidize NH3 to NO3-, although the NH3 oxidizers nor NO3—oxidizers can do this alone

14. Syntropy and Methanogenesis Acetogenesis is a competing H 2 - consuming process to methanogenesis in some environments e.g. termite hindgut, permafrost soils Acetogens can ferment glucose and methoxylated aromatic compounds from lignin whereas methanogens cannot

15. Think, pair, share. Work in pairs to complete the worksheet. Active Learning

16. Nitrogen Nitrogen (N) in the largest singe source in the atmosphere An element used to build DNA, RNA, and proteins, this is the building block of life Most living organisms are unable to use N as it exist in the atmosphere It can be used by most living organisms by travelling through one of the four processes in the nitrogen cycle nasa.gov

17. Nitrogen Cycle Nitrogen fixation Ammonification Nitrification Denitrification Genesis Ag

18. Nitrification

19. Nitrogen Fixation NH4 + is oxidized to NO 2 - according to the following energy-yielding reactions, which is normalized to one electron equivalent.