Lichens and industrial pollution - Ecology of Industrial Pollution - page 56

All trunks LAN including oak

30

R 2 = 0.507 ± SE

20

10

b

a

0

-10

c

-20

-30

-40

0 1 2 3 4

NH 3 concentration (

5 6 7 8

g m -3 )

µ

Figure 3.4. Relationship between the abundance of sensitive lichens (L AN index) on tree
trunks and NH 3 concentrations across the UK. The 95% confidence limits of the
regression line are shown (Sutton et al. 2009 ) . Figure 3.4 was originally published as
Fig. 6.5. in Sutton, M. A., Wolseley, P. A., Leith, I. D., Van Dijk, N., Tang, Y. S., James, P. W.,
Theobald, M. R. & Whitfield, C. ( 2009 ) 'Estimation of the ammonia critical level for
epiphytic lichens based on observations at farm, landscape and national scales' in
Sutton, M., Reis, S. & Baker, M. H. (eds.), Atmospheric Ammonia Detecting Emission Changes
and Environmental Impacts, p. 80. Netherlands, Springer. # 2009 Springer Science þ

Business Media B. V. Reproduced with kind permission of Springer Science and
Business Media.

background concentrations. Through this research, a revised long-term critical
level of 1 m gm 3 NH 3 has been proposed at an Expert Workshop held under
the UNECE Convention on Long-range Transboundary Air Pollution (WG1 2006 )
to protect epiphytic lichen communities and bryophytes. It has now been
adopted, and the new text will soon be inserted into 'the Mapping Manual',
the standard reference (UNECE 2004 ). However, whilst it is believed the critical
level would be protective over a period of several years, the long-term conse-
quences (20 30 years) are far less certain (Sutton et al. 2009 ) .
Nitric acid (HNO 3 ) and ozone (O 3 ), secondary products of photochemical
reactions of nitrogen oxides (NO x ) and volatile organic compounds, are impor-
tant pollutants in regions with large outputs from petrol combustion (Riddell