Biogeochemical cycles Flashcards
What is bio-geochemistry?
study of how living organisms, geological
processes, and chemical interactions drive the cycling of elements in
the Earth’s systems.
What is the comparison of % N, O and CH4 on earth, venus and mars?
N: E= 78 V= 3.5 M= 2.7
O: E= 21 V=trace M=0.13
CH4: E=0.002 V= 0 M= 0
What is a cycle?
a series of changes that comes back to the starting point and can be repeated
What is the difference between an open and closed system?
open= parts can be lost
closed= nothing added or lost
What can we assume when there is a slow rate of change in a system?
steady state- equilibrium
How have humans changed the carbon and nitrogen cycle?
burning fossil fuels
fertiliser application
What is a flux?
the movement of matter or energy from one reservoir to another
What evidence is there that earth hasn’t always been in equilibrium?
banded iron formation that only occurred up until 1.8 billion years ago with alternating layers showing high and low oxygen conditions
What was CO2 ppm like when there was a lack of biological life?
6000
How does the keeling curve show seasonality?
The peaks and troughs on the graph (ignoring general increasing trend) are due to the seasons reducing photosynthetic and thus carbon uptake in NH
What is carbon sequestration?
the removal of carbon from the atmosphere and storage
What is the distribution of carbon between the biosphere, atmosphere and hydrosphere?
50% atmo
25% both bio and hydro
What is BIFoR face facility?
decadal experiment to study the response of a mature temperate deciduous forest ecosystem to elevated CO2
What is the infrastructure at BIFoR?
3 no-infrastructure controls (ambient air);
3 ambient-air FACE rings &
3 treatments of +150 ppmv CO2
Will increasing CO2 increase carbon storage?
More CO2 will enter bio by photosynthesis but in autumn trees which have made more leave will all fall to ground decay and release CO2 back into atmo
How is the best way that plants can lead to increased CO2 storage?
If when photosynthesising more due to increased CO2 levels they transfer it to the soil where it will stay for longer
What factors need to be considered when asking if trees can keep pace with CO2 emissions?
Maturity
Climate
Nutrient availability
Water availability
Species
Soil type
Sunlight
How long does anthropogenic CO2 stay in the atmo?
around 200 years to enter the ocean
What is the majority of nitrogen in the terrestrial ecosystem like?
biologically unavailable (geo and atmo)
How much of N is available?
1%
What is the difference between reactive and non-reactive nitrogen?
Reactive (Nr) = inorganic reduced N (ammonia) and inorganic oxidised forms (NOx) and organic compounds (Urea)
What have humans done to reactive nitrogen availability?
roughly doubled
What are the key processes in the nitrogen cycle?
Fixation
Mineralisation
Immobilisation
Plant uptake
Nitrification
Denitrification
What happens with nitrogen fixation?
input N2 to NH3
What happens with nitrogen mineralisation?
breakdown organic matter to NH3
What happens with nitrogen Immobalisation?
microbial uptake
What happens with nitrification?
Conversion NH3 to NO3-
What happens with denitrification?
NO3- to N2
What are riparian buffers?
Riparian- adjacent/ on bank of water body or stream
Buffer- reduction impact of surrounding land use
Where are riparian buffers commonly used?
agricultural areas
Diffuse pollution
What will happen to redox over a landscape?
Will high O2 area that will transition to a hypoxic area found near water body
Mottled zone in the middle (dominated by drying and flooding)
What is the land like above the redox boundary?
oxic with occasional flooding and O2 ingress
What will happen in the soil as you approach the redox boundary?
reduction in oxygen so more limiting for microorganisms as soil becomes hypoxic
What will the hypoxia zone be like?
Some respiration
Denitrification
Nitrification slowdown
What conditions can facultative anaerobes be in?
more diverse conditions can use O or other sources but prefer O as more efficient
What conditions can oligate anaerobes survive in?
Need anoxic (no oxygen)
What is the unit for redox potential?
mV- millivolts
What are the general redox potentials for varying oxidised and reduced soils?
Well oxidised soils= +700 - +500
Moderately reduced soils= +400 - +200
Reduced soils= +100 to -100
Highly reduced soils= -100 to -300
