ESS Topic 5.8 - Acid Deposition
5.8 Acid Deposition
5.8.1 Outline the chemistry leading to the formation of acidified precipitations.
• Acid deposition can be either wet or dry:
• Wet deposition - acidic rain, snow, or other precipitation
• Dry deposition - acidic gas or dry particles, not mixed with water
• Pollutants can be classified as either primary or secondary:
• Primary pollutants - those directly emitted by a factory or automobile, such as...
• SO2 - sulfur dioxide
• NO and NO2, usually identified as NOx
• Secondary pollutants - primary pollutants react with other substances in the
atmosphere and create different pollutants, such as...
• H2SO3 - sulfurous acid
• H2SO4 - sulfuric acid
• HNO3 - nitric acid
5.8.2 Describe three possible effects of acid deposition on soil, water and living
organisms.
• Direct effects:
• chlorophyll loss & yellowing of tree leaves and buds → diminished growth
• thinning of cuticle (the waxy coating on needles)
• symbiotic root microbes killed (i.e. Rhizobium spp. and other beneficial fungi)
Toxic
effects:
•
• aluminum (Al) leaches out of soil into streams
• Al disrupts salt, water, and oxygen regulating mechanisms in fish
• Al can also adhere to fish gills, causing suffocation
• lichens sensitive to SO2 gases and used as indicator species
• Nutrient effects:
• soil particles can’t retain Ca, Mg, K, and other nutrients in acidic environment, so
those nutrients are leached out of soil and not available to trees
• dissolved Al ions damage root hairs (the smallest roots, which are the most
effective at absorbing nutrients), so the trees are unable to absorb as many
nutrients
• N-fixing bacteria don’t function as well, so less N is added to soil matrix
• Damage to human infrastructure:
• acid rain dissolves limestone structures, especially buildings and statues
5.8.3 Explain why the effect of acid deposition is regional rather than global.
• Acid precipitation falls back to Earth rather than entering stratospheric jet stream
• most areas are downwind of pollution sources
• Canadian forests damaged by coal-fired power plants in USA
• Scandinavian and German forests damaged by British coal plants
5.8.4 Describe and evaluate pollution management strategies for acid deposition.
• See Table 15.7 on p.298 of the IB ESS 2010 Course Companion
• Replace
• switch to renewable energy sources (reduce fossil fuel use)
• increase energy efficiency (better light bulbs and appliances)
• more public transportation (fewer automobiles on the road)
• use low-sulfur fuels
• Regulate
International School of Tanganyika IBDP ESS 2010-2011
Instructor: Mr Brad Kremer
ESS Topic 5.8 - Acid Deposition
• install ‘scrubbers’ on smokestacks of coal-fired power plants to remove SO2
• catalytic converters installed on automobiles (required by law in the US, Canada,
and Europe)
• Restore
• add lime to acidified lakes and streams
• add lime to forestry plantations (why not natural forests?)
• UN Convention on Long-Range Transboundary Air Pollutants (LRTAP) - 1979;
subsequently amended and modified by US, Canada, and Europe
International School of Tanganyika IBDP ESS 2010-2011
Instructor: Mr Brad Kremer