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For various industrial areas "emission cadastral maps" have been devised which 
are charted from information on aerial photographs and remote serSor imagery. 
For the Frankfurt area, West Germany, (Schneider, 1972) distinguished four types 
of emittants :- 
( i) emission from large industrial plants, with an exhaust 
of more than 9 kilograms of S05 per hour - point sources 
( ii) emission of other manufacturing plants, with an exhaust 
of between 0.5 and 8 kilograms of SO, per hour - point sources 
2 p 
(iii) emission from private heating - areal sources 
( iv) emission from traffic vehicles - linear sources 
Murtha used Landsat imagery to detect damage caused by sulphur dioxide fumes in 
an extensive forest area in Canada. Tbe vegetation damage was most obvious on 
Band 5 as exposed areas or dry dead foliage have the highest spectral reflectance 
in the red spectral région and also the chlorophyll of green healthy vegetation 
absorbs in this region, so these areas appear dark. Thus the contrast between 
healthy and damaged zones is greatest on Band 5. In conclusion, satellite 
data should provide a simple means of mapping and monitoring large forest areas 
affected by severe sulphur dioxide fume damage, provided sufficient time has 
elapsed for the damaged forest region to take on the characteristics of the air 
pollutant damage. 
2.5 Lead Pollution 
Tetraethyl lead is added to petrol for reasons of efficiency, but it is an 
environmental pollutant. Vegetation near busy roads may contain as much as 
500 ppm (by weight) of lead and as such is unsuitable for fodder. However, 
the pollution seldom stretches far from the road and damage to crops has only 
rarely been reported. No specific remote sensing studies have been reported 
on the detection or menitoring of lead pollution. 
2.4 Photochemical Smog 
Photochemical smogs iesult from the presence of large numbers of petrol engines 
producing exhaust gases. When a temperature inversion occurs the pollutants are 
trapped in high concentrations near the ground. Under conditions of high light 
intensity, ozone and peroxacetyl nitrates (PAN) are produced. It is a serious 
problem in many paris of the world. California is the region most often quoted 
as being affected, but it can occur anywhere under the correct conditions. It 
has been reported in many parts of the USA, in Japan, Australia and occasionally 
in Europe, such as The Netherlands and S.E. England. 
Ground level concentrations of ozone over 5 pphm will cause damage tc plants, 
under pollution conditions, levels can reach 40 pphm in summer and autum. 
Pollutant effects include glazing and flecking on the upper surface of the leaves. 
The guard cells of the stomatal system rapidly close, reducing the intake of 
carbon dioxide, thus lowering yield. In very high levels of ozone the guard 
cells collapse and gape open. The semi-permeable membrane of the cell is 
affected, allowing leakage of the cell constituents. Necrosis of plants and 
defoliation of pine trees is common at these high levels. PAN is a very strong 
oxidant with drastic effects on the enzyme systems of the plant proteins, causing 
the denaturing of the cell membrance and collapse of the cell wall allowing the 
cell constituents to escape through protein holes. 
Miller, et al (1969), Heller (1969, 1971), Wert (1969), Weber and Polcyn (1972) 
have reported on the effects of oxidant air pollution on ponderosa pine foliage 
in the Los Angeles, USA area and how the foliar damage can be evaluated on colour 
films. The symptoms most useful in identifying affected pines were colour, low 
density and shortness of needles and high frequency of bare branches. Munsell 
colour notations made both on the ground and on colour films identified healthy 
foliage as a green-yellow hue(2.5 GY) and affected foliage as yellow (10 Y to