Carbon Cycle and Climate Change Notes Flashcards
Carbon Sources
processes that add carbon to the environment
Carbon Sinks
places where carbon is stored (oceans/ bodies of water = largest sinks on Earth; other sinks = organisms, rocks, atmosphere)
Carbon Fluxes
processes that move/ transfer carbon (photosynthesis = largest flux on Earth); negative flux = remove carbon; positive = add carbon
Photosynthesis and Carbon
Carbon dioxide in the atmosphere or hydrosphere diffuses into autotrophs and is “fixed” as organic compounds (e.g. sugars, and even proteins and lipids) – Remember the Calvin Cycle (the light independent reactions?!?)
Note: Photosynthesis has the LARGEST role in transferring carbon/ transfers the LARGEST mass of carbon in the carbon cycle!
Feeding and Carbon
Organic carbon moves from autotrophs to heterotrophs, from one trophic level to the next in food chains/ webs
Respiration and Carbon
All organisms (including plants) metabolize (break down) organic compounds for energy, (ATP) and release carbon dioxide (diffuses into air/ water)
Decomposition and Carbon
releases carbon (as CO2 or CH4) into soil/ water/ atmosphere
Decomposers/ saprotrophs release CO2 during decay (aerobic process)
Methanogens (archaeans) release methane (CH4) as they break down organic matter in ANAEROBIC conditions (methane diffuses into atmosphere or accumulates underground)
In atmosphere, CH4 is oxidized to CO2 and water
In soils/ sea beds, deposits of CH4 (in anoxic conditions) form natural gas
In waterlogged soils, anaerobic conditions produce acidic conditions that inhibit saprotrophs, so organic matter only partially decomposed = forms PEAT
Lithification and Carbon
compaction of carbon-containing compounds in sediments/ rocks/ fossils
Fossilization and Carbon
Carbon from partially decomposed/ dead organisms becomes trapped in
sediment/ porous rock and forms coal, oil, and natural gas over millions of years
PEAT becomes compressed under sediments, heat and pressure remove moisture and force out impurities = COAL forms
Marine organisms die/ partially decay on ocean floor, buried/ compressed/ heated under sediments in anoxic conditions and hydrocarbons form OIL and NATURAL GAS (which move into surrounding porous rock)
Combustion and Carbon
During the burning of fossil fuels and biomass (forests etc.), carbon dioxide is released
Carbon Cycling in Oceans/ Bodies of Water
-Carbon dioxide dissolves in bodies of water (from the atmosphere) - used for aquatic food chains (photosynthesis, feeding, and respiration)
-As CO2 dissolves in water, some of it combines with water to form carbonic acid: 1. CO2 + H2O ⇄ H2CO3
-Carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions (release of H+ ions due dissociation causes water pH to become more acidic - this is why pH drops as CO2 dissolves in water)
2. H2CO3 ⇄ HCO3– + H+
3a. Carbonate ions combine with sediments/ calcium on the ocean floor to form calcium carbonate; compacts over time (lithification) to form limestone
3b. Aquatic organisms (molluscs and corals) absorb carbonate ions and combine them with calcium ions to form calcium carbonate to create exoskeletons and shells
Methane in the Carbon Cycle
-Methanogens produce methane as a metabolic byproduct in ANAEROBIC conditions (wetlands - swamps/ marshes, marine sediments - muds in lake beds etc., digestive tracts of ruminants - cows, sheep, goats)
-Methane diffuses into atmosphere or accumulates underground (when organic matter is buried in anoxic conditions, methane deposits form natural gas)
-Methane in the atmosphere is oxidized to form carbon dioxide and water:
CH4 + 2 O2 → CO2 + 2 H2O
Formation of PEAT
In most soils, saprotrophs (bacteria/ fungi) break down dead organisms/ leaves etc. and return their nutrients to the soil (nutrient cycling). This decomposition is an AEROBIC process (it requires oxygen).
Waterlogged soils create anaerobic conditions. Anaerobic respiration in these soils creates organic acids.
Saprotrophs are inhibited by acidic conditions, so organic matter is not fully decomposed and carbon-rich molecules remain in the soil forming PEAT
Formation of Oil/ Natural Gas/ Coal
Over time, sediments are deposited over the peat, compacting it.
As the peat is buried deeper and deeper in the Earth, heat and pressure remove moisture, force out impurities, and cause a chemical transformation of the carbon compounds into coal
In oceans, sediments form on top of decaying organic matter, creating anoxic conditions (organic matter is only partially decomposed)
As more sediments form on top of this matter, heat and pressure create hydrocarbons, which form oil and gas
Oil and gas move out of the source rock and form deposits in the surrounding porous rocks
Short/ Long Wavelength Radiation and the Greenhouse Effect
ncoming radiation from the sun is short-wave ultraviolet radiation (passes through greenhouse gases)
Short-wave radiation is absorbed or converted to long-wave radiation on Earth’s surface
Long-wave radiation (infrared radiation/ IR/ heat) cannot pass back through greenhouse gases and is reflected back toward Earth/ absorbed by greenhouse gases (warms!)
Some of the radiation is reflected by the Earth’s surface back into space
