Biogeochemical cycles (The Physical environment)

The three Biogeochemical cycles

The carbon cycle, nitrogen cycle, phosphorous cycle

Reservoirs of carbon and their forms

The atmosphere- C02, methane,

The hydrosphere- carbonic acid, hydrogen carbonate ions

lithosphere-carbonate rocks eg limestone

biosphere- all biological molecules eg lipids, proteins, DNA

Carbon cycle photosynthesis

Photosynthesis- plants absorbing c02 from atmosphere and h20 then convert to glucose which gets stored in their biomass. A form of carbon sequestration

Carbon cycle respiration

Respiration- aerobic (with oxygen) anaerobic (without oxygen), they both release energy from biological molecules such as carbohydrates to power an organisms metabolism. Aerobic releases more energy than anaerobic. Aerobic releases c02 into the atmosphere but aneroid releases methane

Carbon cycle water bodies

C02 dissolved into wster to form carbonic acid which breaks down into a bicarbonate ion and a hydrogen ion which increases the acidity of the ocean, this is reversible so c02 can reform and exsolve out of water bodies returning to the atmosphere

Carbon dioxide food chains/webs

Plants use sunlight to synthesis carbohydrates and store in their biomass, when eaten by herbivores the carbon is transferred and transferred again if eaten by a predator. Decomposers break down waste returning the carbon contained within back into the atmosphere

The carbon cycle processes

Photosynthesis, respiration, water bodies, food chains/webs

Define fossilisation

The formation of long term carbon stores such as fossil fuels and carbonate rocks

Human activities effecting the carbon cycle

Deforestation- reduces photosynthesis slowing rate of carbon sequestration from atmosphere into biomass, wood harvested can then be burned to release the c02 into the atmosphere

Shipping- release oil and heavy metals into the ocean polluting water and killing photosynthesising organisms reduces volume of carbon dioxide they can take up

Agriculture- soil can be aerated ploughing and installing drainage systems to prevent flooding encouraging aerobic respiration

Creating anaerobic sites such and landfill

Fixing human created problems (carbon)

Place carbon sinks/stores under protected designated areas eg SSSIs or NNRs banning any damaging activities, reducing reliance on fossil fuels like using HEP/solar/wind power

Recycling, utilising principles of the circular economy to reduce the volume of waste sent to landfills reducing the the volume of methane released

Define Biogeochemical cycles

Processes allowing the cycle of essential nutrients through biotic and abiotic components of the earth

Aerobic respiration

Respiration with oxygen releasing more energy snd carbon dioxide

Anaerobic respiration

Respiration without oxygen releasing less energy and methane

Carbonic acid

Formed when c02 dissolved into water contributing to ocean acidity

Food chains/webs

Transfer of carbon through the consumption and decomposition of organisms in ecosystems

Combustion

The process of burning a fuel source to release energy

Carbon sinks/stores

Natural/artificial reservoirs that accumulate and store carbon compounds

Which reservoir does Carbon Capture storage happen in

The lithosphere

Which reservoir does carbon sequestration happen in

The biosphere

Nitrogen reservoirs and forms

Atmosphere- nitrogen gas, nitrous oxide gases

Hydrosphere- dissolved nitrates, ammonium ions

Lithosphere- nitrates, nitrites, ammonium compounds in the soil

Biosphere- genetic material eg DNA and proteins

Roles of microorganisms in the nitrogen cycle

Decomposition- breakdown of DOM to release ammonia/ ammonium ions into the soil

Nitrogen fixation- converting nitrogen gas into a more usable form by breaking the triple bond and releasing the 2 nitrogen atoms

Nitrification- where they convert ammonium ions into nitro gates and then nitrates in a series of oxidation reactions in the soil Nitrogen fixation

Denitrification- converting nitrates in the soil to nitrates in the soil to nitrogen gas which gets released into the atmosphere

Nitrogen fixation

When nitrogen gas is converted into any other usable for eg nitrates/ammonium. Cannot be used by living organisms as they don’t have the enzyme to break the triple bond but there are bacterial species that do known as nitrogen fixers as they convert it into a form that organisms can use to make DNA and proteins

Nitrogen fixation processes -Haber process

Artificial process used to make the inorganic fertilisers in agriculture. Nitrogen and hydrogen are brought together in high temps and pressures by combustion of fossil fuels to form ammonia -not sustainable but can increase soil fertility

Name the nitrogen fixation processes

Haber process, ionisation, fixation by soil bacteria, fixation in legumes

Nitrogen fixation processes - fixation in legumes

Pea/bean plants that form a symbiotic relationship with nitrogen fixation bacteria species that live in root nodules. The bacteria have the enzyme nitrogenase which hydrolyses the triple bond in nitrogen gas and give the products to the plant. In return the plant provides bacteria with sugars made in photosynthesis eg sucrose

Nitrogen fixation processes -Ionisation

When lightning causes oxygen and nitrogen in the atmosphere to fuse and create oxides of nitrogen which happens due to the high energy of the lighting which makes the reaction take place

Ammonification

The formation of ammonium ions carried out by bacteria in the soil using DOM eg leaf litter. This processes is essential in increasing soil fertility as nitrates are the easiest form of nitrogen for plants to absorb through their roots, the bacteria are aerobic so require oxygen in order to complete the process so aerated and well drained soils are needed

Simple 3 steps: ammonium ions are oxidised into nitrites and those are oxidised into nitrates

Nitrogen fixation processes -fixation by bacteria

Free living bacterial species naturally found in soil that have the enzyme to break the triple bond in nitrogen gas so they can utilise the nitrogen to build their DNA and proteins

Nitrification

A process that used ammonium ions carried out by nitrifying bacteria in the soil that converts the ammonium ions into nitrites in a series of oxidation reactions

Denitrification

Denitrifying bacteria convert nitrates in the soil to nitrogen and nitrous oxide gases in the atmosphere, happens in anaerobic soils reducing soil fertility especially if soils are compacted or waterlogged

Name that human impacts on the nitrogen cycle

Ploughing and installing water drainage systems, Inorganic fertilisers, fossil fuels

Human impacts on nitrogen cycle -fossil fuels

Combustion of fossil fuels in vehicle engines involves high temps in the engine causing nitrogen and oxygen to bond and create nitrous oxide gases which are released into the exhaust gases

Human impacts on nitrogen cycle -ploughing and wster drainage

increase the aeration of the soil encouraging nitrification. But using heavy machinery/livestock will compact soil increasing flood risk and rates of denitrification

Human impacts nitrogen cycle -inorganic fertilisers

release large volumes of nitrates into the soil at once which plants can’t absorb all at once which then increases nitrous oxide gases in the atmosphere. Increase of nutrients in the water can cause algal blooms on the surface blocking sunlight from reaching submerged plants which then die and take oxygen out of the water by increasing number of aerobic decomposing bacteria -eutrophication

Methods to increase the sustainability of the nitrogen cycle

Reducing reliance of fossil fuels, manage agricultural practices

Methods to increase the sustainability of the nitrogen cycle -reduce fossil fuels

Helps reduce the volume of nitrogen oxide gases into the atmosphere, instead use electric or hydrogen powered cars and switching to renewable energy sources for electricity generation as well as utilising clean up techniques to prevent nitrous oxide release from cars/exhaust gases such as a catalytic converter

Methods to increase the sustainability of the nitrogen cycle -agricultural practices

To recuse reliance on inorganic fertilisers to increase soil fertility eg using organic fertilisers such as manure which decompose to release nitrogen more slowly reducing chance of leaching.

Cultivating leguminous crops as they don’t require inorganic fertilisers to gain nitrogen.

Minimal use of pesticides so that soil biota aren’t harmed

Bond found in nitrogen gas

Triple covalent bond

What is an enzyme

Biological catalyst that speeds up the rate of reaction

How does the phosphorous cycle differ to the other cycles

It does not have a gaseous form so will not be found in the atmosphere reservoir

The phosphorous cycle reservoirs and forms

Hydrosphere- dissolved phosphate ions

Lithosphere- phosphates in the soil and phosphorus rich rocks

Biosphere- bones, DNA, cell membranes

Name the phosphorus cycle processes

Erosion and weathering, food chains/webs, pH

Phosphorus cycle processes -erosion and weathering

Releases phosphorous from rocks but can cause leaching into nearby water bodies due to soil erosion, it can then undergo sedimentation and form rocks on the ocean bottom. If it was dissolved in the soil it could be absorbed by plant roots and then used to make biological molecules. Although plant roots are ineffective at absorbing phosphorous so could end up leaching from the soil back into water bodies.

Phosphorus cycle processes -food webs

Once plants have taken up phosphorus they can get eaten and it will transferred to the consumer. Once that organism produces waste or die then it will be decomposed by soil biota eg bacteria/fungi which releases it back into the soil and it can then be re-absorbed by other plants

Phosphorus cycle processes -pH

Soil pH can impact the solubility of phosphate ions and therefore the ease at which plants can absorb them, increased acidity increase the solubility which can lead to an increased risk of leaching and running off into nearby water bodies. Alkaline conditions decrease solubility and the ability for root absorption

Management strategies for the phosphorous cycle

Sustainability- reduce the amount of mined deposits bc the volume is depleting quickly and instead use organic fertilisers sub as manure or add mycorrhizal fungi to the soil which forms a symbiotic relationship with crop roots

Human activities affecting processes in the phosphorous cycle -extraction

Large amounts of phosphorous are extracted by mining deposits for eg. Guano which is the accumulation of bird waste and is rich in phosphorus. It’s then used I. The manufacture of inorganic fertilisers which are then spread onto fields. This mobilises phosphorous at a faster rate than natural which increase the liklihood of eutrophication

Why is the phosphorous cycle a limiting factor

The element is in the shortest supply