Chapter 12 - Global biogeochemical cycles and their alterations by humans (CHAPTER + SLIDES) Flashcards
(24 cards)
What is biogeochemistry?
The science that studies the biotic controls on environmental chemistry and the geochemical control of ecosystem structure and function.
What is the phosphorus cycle?
A biogeochemical cycle that is largely geological, involving the movement of phosphorus through rocks, soils, water, and organisms, with major flows often bound in sediments.
What is the nitrogen cycle?
A biogeochemical cycle that is heavily influenced by biological processes, involving the transformation of nitrogen between various chemical forms by microorganisms and other organisms.
What is denitrification?
The microbial process of converting nitrate (NO₃⁻) into molecular nitrogen gas (N₂), releasing it back into the atmosphere.
What is Net Primary Productivity (NPP)?
The rate at which primary producers (like plants) accumulate biomass, representing the net amount of carbon fixed through photosynthesis minus the carbon respired by the producers.
What is Net Ecosystem Production (NEP)?
The balance between net primary productivity and heterotrophic respiration, representing the net accumulation or loss of carbon in an ecosystem.
What is a carbon sink?
A natural or artificial reservoir that accumulates and stores carbon-containing chemical compounds, thus removing carbon from the atmosphere.
What is ocean acidification?
The decrease in the pH of the Earth’s oceans, caused by the uptake of atmospheric carbon dioxide.
What is methanogenesis?
The biological production of methane (CH₄) by microorganisms called methanogens, typically occurring in anaerobic (oxygen-free) environments.
What is radiative forcing?
The difference between the incoming solar energy absorbed by the Earth and the energy radiated back to space, a measure of how a factor influences the energy balance of the Earth-atmosphere system.
What is Nitrous Oxide (N₂O)?
A potent greenhouse gas and ozone-depleting substance, produced through various biological and anthropogenic processes in the nitrogen cycle.
What is eutrophication?
The excessive enrichment of water bodies with nutrients, primarily nitrogen and phosphorus, leading to increased algal growth, oxygen depletion, and harm to aquatic ecosystems.
What is the Haber-Bosch Process?
An industrial process for producing synthetic ammonia (NH₃) from nitrogen and hydrogen, a key component in the production of synthetic nitrogen fertilizer.
What are Net Anthropogenic Nitrogen Inputs (NANI)?
The total amount of biologically available nitrogen entering a region or watershed due to human activities, such as fertilizer use, atmospheric deposition, and food/feed trade.
What is a feedback loop?
A process within a system where the output of the system influences the input, either amplifying (positive feedback) or dampening (negative feedback) the initial change.
Why is the phosphorus cycle considered more geological and the nitrogen cycle more biologically mediated?
The phosphorus cycle is considered more geological because its major flows involve the weathering of rocks and the movement of sediments in rivers and oceans. The nitrogen cycle is more biologically mediated due to the crucial role of microorganisms in transforming nitrogen between different chemical forms through processes like nitrogen fixation and denitrification.
What are two major human activities that have accelerated the phosphorus cycle?
The mining of phosphorus for fertilizer and the increased flow of phosphorus-containing dust through the atmosphere due to desertification.
How has human activity increased the atmospheric concentration of carbon dioxide over the past 200 years?
Through the combustion of fossil fuels (coal, oil, and natural gas) and deforestation, which releases carbon stored in biomass and soils.
What is the role of oceans and terrestrial ecosystems in the global carbon dioxide cycle?
Oceans and terrestrial ecosystems act as carbon sinks, absorbing a significant portion of the atmospheric carbon dioxide released by human activities, thereby slowing the rate of increase in atmospheric CO₂ concentrations.
Why is the ocean sink for atmospheric carbon dioxide considered temporary?
Because the absorbed CO₂ eventually makes its way into deep ocean waters, which slowly circulate and eventually return to the surface, where some of the CO₂ can be released back into the atmosphere over centuries.
How does the uptake of carbon dioxide by oceans affect ocean chemistry?
It leads to ocean acidification because dissolved CO₂ forms carbonic acid, which lowers the pH of the seawater.
Explain why coastal wetlands release less methane to the atmosphere than freshwater wetlands.
Coastal wetlands release less methane than freshwater wetlands because seawater has a much higher concentration of sulfate. Bacteria that use sulfate in their respiration outcompete methane-producing bacteria for organic matter, leading to less methane production.
What was a major historical event that significantly altered the global nitrogen cycle?
The invention of synthetic nitrogen fertilizer through the Haber-Bosch process in 1909 significantly altered the global nitrogen cycle by creating a massive new source of biologically available nitrogen for agriculture.
Besides synthetic fertilizer production, what is another human activity that contributes to the creation of biologically available nitrogen?
The burning of fossil fuels, which catalyzes the reaction between atmospheric nitrogen and oxygen to produce nitrogen oxide gases.
