Ambient Air Pollution Flashcards
What is Acid Rain?
Precipitation that is significantly more acidic than natural rain.
Why does it drive acidity?
Presence of dissolved atmospheric CO2, forming carbonic acid, H2CO3, which ionises releasing a H+, reducing the pH of the system
What are the two dominant acids in acid rain?
Sulfur Dioxide and Nitrogen Oxides as primary pollutants and Sulfuric acid and nitric acid as secondary.
How do both of these form?
Secondary pollutants through reactions with O2, travelling downwind from their source.
What is the pathway of sulfuric acid from SO2?
Emission from coal/oil combustion in power plants, SO2 reacts with O2 and H2O forming sulfuric acid, this reacts with other aerosols which then precipitates
What is the reaction of SO2-H2SO4?
SO2 oxidised to sulfur trioxide(SO3) by O2, (2SO2 + O2 –> 2SO3, which then reacts with water vapor forming sulfuric acid.
What is the pathway of nitric acid formation from Nox?
Emission from combustion, NO2 oxidation to NO3 then reaction with water vapor forming HNO3, reaction with acidic aerosols, then precipitation…
What does the impact of acid rain on biota largely depend on?
Composition of surrounding soil and bedrock.
What are examples?
f bedrock is limestone/chalk, acid can be neutralised by CaCO3, a base reacting with acid, forming bicarbonate ions, dissolving the rock.
What soil properties determine acid rain impact?
Buffering capacity, Ca availability, nutrient availability, and metal mobilization.
How does acid rain impact plant-life?
Through lowering of pH, cations like K, Ca and Mg exchange with H+ and the ions are leached.
How does acid rain leach nutrients?
Reacts with cations like Ca2, Mg2 and K2, dissolving from soil matrix, depleting the soil.
What is a study demonstrating this acid rain leaching nutrients?
Ibrahim et al., 2024
How does it exacerbate aluminium toxicity?
Mobilizes Al, which is toxic to plant roots, impairing water/nutrient assimilation capacity.
How can this impact water bodies?
Lakes relying on land-runoff for calcium may become threatened if dependent on calcium, thus impacting species composition and ecosystem function.
Why is calcium important for organisms?
Roles in vital physiological functions, essential for CACO3 in shells, skeletons, and eggshells
What is the concept of critical load?
Recognition that different levels of risk from acid rain are faced in different regions.
How can acidification reduce plants ability to grow?
Decreased productivity in lakes and streams means amount of DOC has declined.
What effects does declining DOC have?
Absorbs UV, thus allowing more UV penetration into lower layers of the lake.
Why does UV scattering changes impact organisms?
Positively by reducing DNA damage and impaired photosynthesis risk, or negatively by loss of contro of algal blooms and regulation of abundance/composition of phytoplankton communities.