Acid deposition Flashcards
What is acid deposition? What are the two types?
- The process in which acidic substances leave the atmosphere and is deposited on earth
- All types of acid precipitation
- Dry deposition (acidic gases and solid particles)
- Wet deposition (acid rain, fog, snow)
What is the pH of natural unpolluted rainwater and why?
- 5.6
- Water is naturally acidic because of the presence of CO2 in the atmosphere. It reacts with water to form carbonic acid (H2CO3)
How does acid rain form and what is its pH?
- pH less than 5.6
- Formed when acidic gases such as e.g. SO2 and nitrogen oxides, dissolve in water in atmosphere
- This produces sulfuric acid and nitric acid
How is nitrogen monoxide formed and the equation? 1. Nitrogen reaction
- Either during lightning storms by the reaction of N2 and O2
- OR by the reactions in internal combustion engines
- N2 + O2 –> 2NO* (free radical)
What reduces the level of the emissions of nitrogen monoxide?
- Catalytic converter in vehicle exhaust systems
What reaction does nitrogen oxide undergo in the atmosphere? What is the equation? 2. Nitrogen reaction
- Further oxidation to produce nitrogen dioxide
- 2NO* + O2 –> 2NO2
What reaction does nitrogen dioxide undergo with water? 3. Nitrogen reaction and 4. Nitrogen reaction
- Reacts to form nitric and nitrous acid
- 2NO2* + H2O –> HNO3 + HNO2
- 4NO2* + 2H2O + O2 –> 4HNO3
How is sulfur dioxide formed and the equation? 1. Sulfur reaction
- Occurs naturally in the atmosphere, released during volcanic eruptions, when coal and oil are combusted in power stations
- Oxidised during the combustion
- S + O2 –> SO2
What reaction does SO2 undergo? 2. Sulfur reaction
- Photochemical oxidation when water and SO2 react in the atmosphere
- Catalysed by soot and metallic particles
- 2SO2 + O2 –> 2SO3
What reaction does sulfur dioxide and sulfur trioxide undergo? 3. Sulfur reaction
- React to form sulfurous and sulfuric acid
- SO2 + H2O –> H2SO3
- SO3 + H2O –> H2SO4
What happens in dry deposition?
- Acidic particles and gases fall to the group via dust and smoke
- Does NOT happen through precipitation
- Washed into streams, lakes, rivers
- Causes harm to biological systems
What are 5 effects of acid rain on the environment?
- Enter aquatic ecosystems directly or as run-off
- pH < 5.5 fish cannot survive
- (Al3+) effect fish’s gills, limited O2 uptake
- Loss of species, knock-on effect through food chain, reduce biodiversity in lakes
- Acid removes essential plant nutrients from soil
What are 2 effects of acid rain on buildings?
- Statues and other architectural structures made of limestone or marble (CaCO3) which reacts with sulfuric and nitric acid, erode away
- Structures with iron, steel or aluminum also damaged, increases rate of rusting (greater ion concentration)
What effect does acid deposition have on human health?
- Can affect mucous membranes and lungs, cause irritation and enhance symptoms of asthma
How can acid deposition be reduced?
- By pre-combustion and post-combustion methods
