Nutrient Cycling Flashcards
Define ecosystem
A biological community of interacting organisms and their physical environment
In cycles what is a source and sink
Source= flows out of a large store
Sink= Flows into a large store
What is the movement between stores called, and give examples in the water cycle
Flux
Rainfall, Precipitation, Atmospheric Mositure
What is the residence time (turnover time)
The total pool divided by the sum of all the inputs and outputs from the reservoir
Difference between 1-way and 2-way flux and what are they used to calculate
One Way Flux= One direction. Used to calculate the time that is needed to exhaust a pool
Two-Way= Reversible. Used to calculate half-life
In the carbon cycle give examples of pools
Atmosphere, soils, vegetation, oceans, marine biota and sediment
In the carbon cycle give examples of fluxes
Photosynthesis, plant respiration, microbial decomposition. As well as anthopogenic fossil fuel input and changing land use
What is carbon sequestration
storage of carbon in plants, soils, geologic formations, and the ocean.
What is the only 1-way flux in the carbon cycle
The anthropogenic carbon caused by fossil fuels and cement production
This is creating imbalances- the ecosystem can only deal with imbalances to a certain extent
What does the solubility of a gas depend on
Temperature
Pressure
Chemical nature of gas and liquid
Why does the solubility of gas depend on temperature
- As temperature increases, the solubility of gases decreases.
o This is because as temperature increases the gas molecules have more energy, so move around more and are more likely to break free
o A significant impact of global warming, as the decreasing solubility of oxygen in water is affecting aquatic life forms
Why does the solubility of gas depend on pressure
- Solubility is directly proportional to the pressure, at a given temperature= Henry’s Law
Henrys Law Constant= Partial Pressure of Gas/Solubility of Gas
Why does the solubility of gas depend on the chemical nature of the gas and liquid
In a mixture of gases, each gas behaves as it the other gases are not there- each gas dissolves according to its own (partial) pressure (concentration)
Generally, gases are not very soluble in liquids, unless there is a specific chemical reaction
What ions do acids have
Acids have more H+ ions than OH- ions, but it’s a negative logarithmic relationship. So as H+ increases pH decreases
What should the number of H+ ions and OH- Ions add up to
14
Describe the carbonate cycle
- Concentrations of gases in the atmosphere are in equilibrium with that in the seawater
- Carbon dioxide dissolved in water undergoes a chemical reaction with water to produce carbonic acid (these an in equilibrium)
- By acid definition carbonic acid releases H+ ions into the solution. It does this by dissociating negative bicarbonate ions with positive hydrogen ions- these hydrogen ions decrease the oceans pH
- Bicarbonate further dissociates to form carbonate ions and hydrogen ions
- Carbonate then interacts with calcium and magnesium, to form calcium and magnesium carbonate
- Carbonate buffering system
What are the implications of the changing carbonate cycle
Ocean Acidification
What is causing ocean acidification and what are the issues
-The ocean has a pH of 8 (alkaline)
-But because there is more CO2 in the atmosphere the ocean is absorbing more
-Causing the pH to reduce- fallen by 0.1 units since industrial revolution
-Carbonate ions are an important building block of structures such as seashells- calcifying organisms
-Shellfish are dissolving in the sea water
-Effects non-calcifying organisms as well, for example a fish’s ability to detect predators
-But also as it becomes more acidic its capacity to absorb Co2 decreases
-Decreasing the oceans role in moderating climate change
Importance of Nitrogen
- Essential for proteins and nucleic acids
- Limits ecosystem productivity (eutrophication) or agricultural productivity (fertiliser use)
- Part of an enzyme system that regulates oxidation-reduction of organic C in tissues and of Ribulose enzyme that fix CO2 during photosynthesis
- Involved in a lot of biochemical transformations
- Some forms of N are toxic to ecosystems and human health
What anthropogenic activities add nitrogen to the atmosphere
-Crop Production
-Dairy/Meat Production
-Fossil Fuel Use
Key Pools in the nitrogen cycle
- Atmosphere
- Terrestrial biomass
- Soil Organic Matter
- Mineral N pools are small. Plant and microbial uptake are so rapid that little is even available
N2 is present in the atmosphere but this isn’t available to plants- what needs to happen so it is
-N2 is not bioavailable, despite making up 78% of air
-Plants need nitrogen to be fixated in soil
-Nitrogen is converted to ammonium ions in the soil by nitrifying bacteria
-Ammonium ions are then converted to nitrate and nitrite- which is available to plants. This is done within root nodules or nitrogen fixing bacteria in the soil
What is ammonification
When death and decay occurs, the dead items are converted back into ammonium ions
What is denitrification
-Nitrate converted back into nitrogen in the air through nitrifying bacteria
-Natural denitrification occurs during flooding or where there is lack of aeration in the soil- soil environment anaerobic, removing nitrate from the soil
