Environmental Assessment
Volume B-4.1
Mine
Flora
Ambatovy Project
159
January 2006
Impact assessments were conducted for the period of construction through
operation and the closure phase. It is assumed that maximum impacts will occur
during the construction period and through operation, particularly during
construction and the initial stages of operation when direct loss of azonal and
transitional habitats will be greatest.
Effects of Air Emissions
Fugitive dust (total suspended solids) and dispersion of sulphur dioxide (SO
2
)
and nitrogen oxides (NO
X
) were modelled for the mine site based on emissions
derived from diesel-fired generators and mine fleet vehicles, and dust generated
by mine vehicles as well (Climate and Air Quality, Volume B, Section 3.4).
Emissions of SO
2
and NO
X
were evaluated in the context of World Health
Organization (WHO) guidelines for ecological effects on terrestrial vegetation.
These guidelines are more stringent that air quality guidelines for human health
because studies have shown that effects on vegetation from certain pollutants
occur at lower concentrations (WHO 2000). A guideline value for dust is not
provided by WHO or the World Bank. Thus, a qualitative assessment on the
effects of dust on vegetation based on relevant literature has been provided.
Guideline values for assessing the long-term ecological effects of SO
2
and NO
X
on terrestrial vegetation are provided in Table 4.1-3. The low end of the range
for SO
2
(10 micrograms/m
3
) has been established for lichens when visible effects
are first observed. The mid-range is applicable to natural forest vegetation
(20 micrograms/m
3
) while the high end is defined for agricultural crops
(30 micrograms/m
3
).
These guidelines are supported by research and data emanating from Europe.
Therefore, there is some uncertainty as to their applicability to the project area.
Adverse affects might occur below the stated guideline values. However, in the
absence of data from the tropics and Madagascar, these guidelines represent the
best available information.
Table 4.1-3 World Health Organization Guideline Values for the Effects of
Individual Substances on Terrestrial Vegetation
Substance
Guideline Concentration Value
Averaging Time
SO
2
10 to 30 micrograms/m
3
annual
NO
X
30 micrograms/m
3
annual
Source: WHO (2000).
