Bio 346 - Freshwater Eco. (Chpt 27) --> Acidification of Waterways Flashcards
Aquatic acidification
Decrease in the acid neutralizing capacity (ANC) of waterways
What are the leading 2 influences of aquatic acidification?
- Industrial
2. Mining
What determines how systems respond to acidification??
Geology of waterways
What causes specie loss or change in abundance?
H+ deposits directly on water surfaces and the indirect effects of high H+ [ ] on catchment soils and vegetation
What do high levels of H+ [ ] lead to?
Release of metals from soils and their subsequent stream transport to the receiving lakes and wetlands
- Can be harmful to humans/wildlife who are drinking the water
What are 3 ways that people are indirectly affected by the death of natural resources?
- Loss of desirable fish or invertebrate species
- Loss of forests
- Irreparable damage
What do buffered drainage basins do?
Help to resist acidification
What 2 chemicals are released during combustion of coal, oil and gas?
- Sulphur dioxide
2. Nitrogen oxides
What is an example of long distance transport?
Atmospheric residence
- can travel up to 400km in a day
What is en example of wet deposits?
Rain or snow containing compounds
What is an example of dry deposits?
Aerosol or gases
- Hard to accurately determine
What is the pH of normal rain compared to acid rain?
Normal rain = 5.5-6
Acid rain = 4 or lower
What causes the pH to drop in rainfall?
heavy human impact
What is the cause of H2CO3 in the atmosphere?
Volcanic sources
What NH3 is released, what does it produce? And what does it do?
Produces OH that neutralizes atmospheric H+
What 3 things is aerosols made from?
- Ammonia (NH3)
- Sulphuric acid (H2SO4)
- Nitric acid (HNO3)
What does the reaction of aerosols consume?
H+
What was the cause of the doubling of emissions of SO2 and NOx in the 20th century?
Burning coal and fuel oil for electricity
Where does NOx come from?
Internal combustion engines (fossil fuels)
What type of lakes are most sensitive to acidification?
3 things
- Transparent
- Low salinity
- Low acid neutralizing capability
What does chemical sensitivity indicate?
That a small amount of acid produces a large decrease in pH
What does ecological sensitivity indicate?
That small addition of acid will result in biological changes
A small change in what, can make a huge effect on acidification?
pH
- Most sensitive with a ph between 5-7
What happens to the sulphur and nitrogen oxide deposition rates as distance increases?
Decreases
Paleolimnology
Studies the relationship between algal communities in sediments and pH have been developed to hindmost pH
What 2 factors influence the decrease in pH?
- Geology
2. Deposition rates
What 4 things is susceptibility to acidification affected by?
- Ability of catchment soils and rock to neutralize acids
- Lake morphology and catchment attributes
- Organic acids in runoff
- Neutralizing agents and precesses in the system
What does ANC stand for?
Acid neutralizing capacity
High ANC
Large fraction of catchment covered by easily weathered rocks and soil
Low ANC
Glaciated areas with highly insoluble bedrock
What can increase ANC?
Calcareous drift from glaciers
When surface soils are of igneous origins (low ANC), what 3 things are susceptibility determined by?
- Lake morphometry
- Catchment attributes
- Atmospheric dust (CaCO3)
What are 3 risks of headwater lakes?
- Small catchment
- Thin soils
- Precipitation reaches lake directly
What 3 things can predict pH?
- Elevation
- Lake morphometry
- Catchment attributes
What do wetlands release?
Acids
What can microbes do?
Neutralize SO2 by processing them
If H+ input is large and CaCO3 supply is limited, what happens to fraction of HCO3 when CO2 and pH decreases?
The increase fraction of HCO3 is lost
How can you remove H+?
In a process of dissolving the aluminum hydroxides, oxides and SiO2 contained in the clay minerals produced during the breakdown of weathered silicates
Soil produced from igneous rocks can see as a buffer and protect the outflowing rivers and the receiving lakes and wetlands is a function of: (3 things)
- The abundance of silicate and clay minerals to be weathered
- The extent to which negative charged clay particles in soil and sediment are associated with base cations such as Ca+, Mg2+ or NH4+ and Al3+ available to exchange places with the incoming H+
- The thickness of the soil or more correctly, the overburden and flow path contact time that the water has with the soil
What is the most important factor in determining buffering capacity?
Acid neutralizing capacity of water
What happens when the supply of acid actions exceed the base cations?
ANC less than 0 and waterways will be strongly acidic with pH below 5.5
What happens when microbes oxidize reduce sulphur and N compounds?
You get a reduction in ANC
How can acid deposition in bogs be neutralized?
2 things
- By the uptake of plants
2. Microbial reduction
What does aeration of previously anoxic soils allow?
Microbes to oxidize sulphur
What has a negative short term effect on pH and alkalinity?
Seasonal reduction in cation outputs from still frozen soils during spring melt of acidic snow
What does anoxia increase?
ANC
- but effect is lost when toxic conditions return
What 2 things can come from permanent gains in ANC?
- Loss of SO4 and NO3
2. Uptake by forest vegetation
What has a positive short term effect on ANC?
Periodic patterns of summer anoxia in lakes or wetlands
What does the accumulation of terrestrial vegetation remove?
Significant amounts of base cations in the production of aboveground biomass
- Thereby, adding to the acidification potential
What does NH3 uptake by plants result in?
Soil acidification
- Unless its offset by denitrification
Is Al solubility high or low in non-acidified systems?
Very low
Al solubility does what at low pH?
Increases
What does a large scatter of data indicate with regarding pH and Al [ ]?
That pH alone does not determine [Al]
Where is Al most abundant?
In the earths crust
What are 2 important determinants of Al solubility?
- Dissolved organic matter (DOM)
2. pH
What happens to pH and DOC as the reactive Al increases?
They both decrease
What happens to pH as transparency increases?
Decreases
- Which is an increase in H+
What is the domino effect with an increase in penetration of light?
- Reduced near-surface heating
- Increase in depth of thermocline
- Increase in depth where photosynthesis is possible
- Increases Uv penetration depth
What does lower primary production affect?
Transparency
What are 4 stressors of acidification?
- Al [ ]
- seasonal changes in DOC
- Fod predation
- Competition
What happens to biodiversity when pH is below 6?
Decreases
What is the main way biological systems are effected?
Solubility of heavy metals
What happens when you have more zooplankton at a higher pH?
Increase in species richness
What 2 things does acidification have little effect on?
- Microbes
2. Sediment
At what pH is the development one extensive algal mats?
5.6
What are phytoplankton sensitive to? (2 things)
- Al
2. Addition on H+
What size of species is more sensitive to acidification?
Large zooplankton
What species are sensitive to low pH?
Benthic macro-invertebrates
- Experience problems with gardening of the exoskeleton
What is a consequence for higher levels in the food chain?
Loss of biodiversity
What kind of environment has the greatest reducing effect on fish and birds? (3 things)
- Low alkalinity
- High elevation
- Low buffering capacity
What happens to community structure when acidification occurs?
Gradual decrease
- Different species have different tolerances
What does pH lower?
Prey abundance
What does low pH in boreal lakes (typically highly oligotrophic) display? (3 things)
- Variability in water colour
- Trophic status
- Contaminant loads
What are reproductive losses due to? (4 things)
- Failed spawning
- Failed egg maturation
- Death of recently hatched larvae
- Lack of food
Negative effects with low pH?
Low pH waters have high [Al]
Temporary recovery can come from what?
Liming
What does liming do?
Initially is neutralizes acids and precipitates Al
- The remainder buffers against acids
What are 3 negative effects on liming?
- Protection is only temporary
- Expensive
- Increases pH and ANC compared to other similar systems
What are 5 environmental effects of liming?
- Reduced clarity
- Reduced mixing depth
- Reduction in eutrophic zone
- Reduction in benthic algae
- Change in food web structure following reproduction of fish eating (piscivorous) fish species
What is rate of recovery a function of? (2 things)
- Dispersal ability
2. Reproductive strategy
What is the long term solution to reduce acidification?
Reduction in emissions
What are 3 effects of reductions in sulphur emissions observed by?
Variability in…
- Historic deposition
- Soil buffering
- Hydrology