Environmental Engineering Reference
In-Depth Information
Simulations of the RAMS coupled to the HYPACT model were performed on 19, 20,
21, and 22 May 2009, to check the effect of meteorological processes on the simulation
of pollutant fate and dispersion in Western European and North African areas. For this,
we used three two-way nested domains centered over the Valencia region, as shown in
Figure 7.2a, with horizontal grid sizes of: G1, (grid one) 54 km; G2, 13.5 km; and G3 4.5 km.
The HYPACT model was run using the Lagrangian dispersion scheme with 3-D wind and
turbulence fields provided by the three RAMS outputs. This model was employed to both
simulate pesticide atmospheric dispersion emitted “only” from four different areas around
the Western Mediterranean and analyze the long-, medium-, and short-range transport of
pesticides according to their lifetimes (more than 10 days, less than 8 h, and less than 2 h).
Emission areas were defined as four identical boxes measuring 1 × 1 km 2 and 200 m high
(with their center at 100 m above ground level). Each box was located at a different area:
Orleans (France), Benicarló and Benifaio (Spain), and Agadir (Morocco). The atmospheric
dispersion was simulated as emitting a mass of 1 ton per day at a variable rate for 96 h. The
emission rates were identical for the four sources and were parameterized for each source
as follows: 10% of the total daily emission in the period from 00:00 to 7:00 UTC; 80% of the
total daily emission between 7:00 and 18:00 UTC; and the remaining 10% between 18:00
and 23:59 UTC.
Rough estimates were used for emission rates and temporal evolution because the only
aim of this simulation was to describe the broadness and differences in the fate and spatial
distribution of the pesticides (depending on their lifetimes) in areas around the Western
Mediterranean under typical late-spring meteorological conditions.
To show the fate of persistent pesticides (lifetime longer than 2 days), Figure 7.2b shows
their LRT for the selected period. Shaded colors indicate the spatial distribution of pes-
ticides emitted simultaneously from the four sources 58 h after the start of emissions.
Concentrations correspond to the total mass of pesticide per unit volume within the first
8000 m above ground level.
To show the medium- and short-range transport during the selected time period, Figure
7.2c and 7.2d show the pesticide distribution throughout the Iberian Peninsula and on its
Mediterranean side, respectively. The shaded color indicates the spatial distribution for
pesticides with a lifetime of 8 h, while the contour lines indicate spatial distributions for
pesticides with a lifetime of 2 h. Concentrations correspond to total pesticide mass per unit
volume within the first 2000 m above ground level.
This modeling exercise confirms the importance of pesticides as a global problem. The
amount of pesticides applied in one region changes continuously, as do the meteorologi-
cal conditions and the mixtures applied. Furthermore, a pesticide applied in one region
can affect the air of another region near or far from the application site. In Figure 7.2b,
the application of pesticides with lifetimes of more than 2 days (persistent pesticides) in
Morocco affects the air in Spain, and the application of pesticides in Spain affects the air
of Western countries. (not only France, but also Italy). Therefore, forbidding the use of
certain types of pesticides, especially the persistent ones, should be globally accepted in
both developed and underdeveloped countries because of the potential of these pesticides
to travel far from their emission points, as is shown in Figure 7.2 and also explained in
Section 7.5.3.
On the other hand, the persistent pesticides are not the only ones capable of disturbing
other regions. Figure 7.2c and 7.2d show the effect of applying pesticides with short and
medium lifetimes in areas not so close to the application sites. It has also been pointed out
that the detection of pesticides in mountain areas—without agricultural sites—could be
due to the transport of the pesticides across regions and even across countries.
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