Biogeochemical Flows (module 4) Flashcards
Identify the four steps of the Nitrogen Cycle, and list the three processes through which Nitrogen is “fixed” into a reactive form that can be used by organisms
3 processes - Atmospheric, Biological, and Industrial fixation
4 steps - Nitrogen fixation (conversion of atmospheric nitrogen into ammonia a form that plants and organisms can use, lightning coverts N2 to NO3)
- Decomposition (microbes break down matter and release NH4)
- Nitrification (conversion of ammonium into nitrite then to nitrate)
- Denitrification (conversion of nitrate and nitrite back into atmospheric nitrogen or nitrous oxygen by denitrifying bacteria, returns nitrogen back into the atmosphere)
Explain why the Phosphorous cycle is the “slowest” of all the matter cycles
- Limited availability in the environment
- Low solubility in water (limits its mobility and availability for uptake by plants)
- Limited biological fixation
Give an example of how human activities can alter the Phosphorous and Nitrogen biogeochemical cycles
- Industrial and intentional biological fixation of nitrogen (through planting N-fixing crops) increases the amount of reactive nitrogen in the environment
- Mining of phosphorous speeds up the release of phosphorous in the environment
- N and P from farmland runoff or industrial and municipal sewage and wastewater dischargers - associated with widespread and expanding eutrophication of freshwaters and coastal zones
Identify the control variables and planetary boundaries for biogeochemical flows
- P global: phosphorus flow from freshwater systems into the ocean - 11 Tg P/year (22)
- P regional: P flow from fertilizers to erodible soils - 6.2 (14)
- N global: Industrial and intentional biological fixation of Nitrogen - 62 Tg N/yr (150)
Describe at least three of the environment effects of excess Nitrogen in the environment
- Eutrophication
- Air pollution (nitrogen released into the air from various sources including cars, industrial processes, and agriculture activities contribute to air pollution)
- Biodiversity loss (excess nitrogen can alter soil chemistry and nutrient recycling, leading to changes in plant community and decline in biodiversity)
Define and explain the process of eutrophication
- Excess of nutrients in a lake or other body of water due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen
1. fertilizer runoff
2. algae blooms due to presence of nutrients
3. bacteria use oxygen to break down the algae
4. fish suffocate due to lack of oxygen
List two control measures that can reduce the amount of P and N entering waterways, and one action that you can take to reduce your individual N footprint
- Decrease nutrient inputs
- Precision farming techniques (optimize the use of fertilizers)
- Erosion control measures
- Manure Management
- Watershed Management
- Eating less beef
- Driving less
- Using less electricity
- Reducing food waste
Describe the factors that lead to the formation of the Dead Zone in the Gulf of Mexico every summer
- During the spring, freshwater runoff from the Mississippi River creates a barrier layer in the gulf, cutting off the saltier water from below from contact with oxygen in the air
- Nitrogen and phosphorus from fertilizer and sewage in the freshwater layer ignite huge algae blooms. When the algae die they sink into the saltier water below and decompose using up the oxygen in the deeper water
- Starved off oxygen the deeper water becomes a dead zone. Fish avoid this area for die in massive numbers. Winter brings respite but spring restarts the cycle
N-cycle Interventions
- Controlling nitrate emissions from fossil-fuel combustion
- Increasing nitrogen-uptake efficiency of crops
- Improved animal-management strategies
- Increase the access of people living in cities to sewage treatment
Anthropogenic Sources of Eutrophication
- Municipal sewage
- Agricultural fertilizers
- Livestock waste
- Stormwater drainage
- Aquaculture
