Nitrogen Flashcards
What pollutants mainly contribute to nitrogen deposition
ammonia and nitrogen oxides
How is atmospheric NOx transformed
Range of secondary pollutants
- nitric acid (HNO3)
- nitrates (NO3)
- organic compounds eg peroxyacetyl nitrate (PAN)
NH3 is transformed into ammonium (NH4+)
How can primary and secondary pollutants be removed?
By wet deposition (scavenging of gases and aerosols by ppt) and by dry deposition (direct turbulent deposition of gases and aerosols)
Which layers of the earths atmosphere are pollutants emitting into?
The lowest 2. the stratosphere and the troposphere (lower). They act as a major channel for the transfer of pollutants from one place to another
What can tell us about past S and N deposition
Ice cores in Greenland can tell us about N. hemisphere s historical pollutant levels.
S was rising in late 20th C then have a later N increase as we moved from coal to N rich oil and gas. Slight loweing of S and N in recent years
Where does most SO2 come from
power stations- now switching to less S rich
Where does most NOx come from
Road transport - impurities in fuel come from incomplete combustion - now new regulations and frequent MOTs
How does rain get its pH
Balancing acidic (oxides of S and N) compounds and alkaline (NH3 and alkaline material in the windblown in soil dust)
What is the orographic effect
Can be an important method for delivery pollutants to the uplands. In uplands it is cold, things grow slowly, and the shape of the landscape exacerbates the whole system
- Orographic cloud- cloud water droplets absorb gaseous pollutants from air currents
- ppt enriched in pollutant content
Winds push the pollutants from Manchester to the Pennines transforming the pollutants as they go. Warm, moist, pollutant-laden air goes over the Pennines, it cools and rises then empties. Adds pollutants to the nutrient poor system.
What communities are most at risk from N deposition
Nutrient-poor communities that are rich in bryophytes and where spp richness of comprised of slow-growing spp. Lots of plants and mosses die with N. In Edale just see peat, so much pollution has destroyed the mosses. The surface has lost stability and blown away.
How can N affect mosses
Too much N can change morphology often leading to sparser mats that are desiccation prone and less efficient at suppressing competitors. Photosynthesis can be compromised along with membrane integrity and sexual reproduction may also be suppressed (incr acidity with N)
Mosses play an important role in nutrient cycling and immobilisation of N in some habitats (eg bogs and heathlands) trap reactive N deposition preventing it from leaching into the water and making it unavailable for higher plants. However the ability to sequester N depends on the N load and systems can soon be saturated
Critical load definition
denotes the atmospheric loads of particular air pollutants. It indicates the amount of a given substance per defined unit of area and time that can be introduced into an ecosystem without bringing about environmental damage in the long term according to present knowledge
In 1997 CL for acidification was exceeded by 71% of UK ecosystems. Now below 50% (2010)
1997 CL for eutrophication was exceeded by 25% of UK 1x1km2 with sensitive grasslands and a little over 50% by heathlands- expected to decline
Target load definition
AMount of pollution deemed achievable and politically acceptable when other factors (such as ethics, scientific uncertainties, and social and economic effect) are balanced with environmental conditions
How can we solve lake acidification
Add lime (calcium carbonate and calcium hydroxide) to lakes. It is very expensive, needs to be repeated every 3-6 years, remote lakes are inaccessible, large pieces of lime dissolve slowly, and can’t do anything for soil acidification
Draw the nitrogen cycle
POP
