Environmental Engineering Reference
In-Depth Information
Distribution
Transport &
dispersion
Photodegradation
Transport &
dispersion
Regional
Mesoscale
Long-range
Pest (part)
Pest (aq)
Pest (gas)
Indirect
reaction with
other pollutants
Direct:
photolysis
Primary products
Other
Pollutants:
Photooxidants
Sprays
VOCs
NO
x
O
OH radicals
Deposition
Spray drift
OH radicals
NO
x
O
3
dry
Wet
Volatilization from soil
Secondary products
Pest application
Volatilization from plants
Wash-off
Runoff (surface waters)
Sorption on soil
Chemical
degradation
Microbiological
degradation
Leaching
(groundwaters)
FIGURE 7.1
Scheme of the processes that can affect pesticide entry, dispersion, and interaction with other pollutants in the
environment.
In the following sections, some of the ways in which pesticides enter the atmosphere are
briefly described.
7.3.1 Entry During Application
In conventional agriculture, one of the most common ways to apply pesticides is by using
sprayers; in some cases, spraying is done from aircrafts; in other cases, spraying is done
manually by workers who use different kinds of equipment filled with the pesticide. With
these sprayers, the formulated pesticides, together with some carrier liquid, usually water,
are converted into droplets. Droplets can have different sizes, depending on the type of
equipment used. Larger droplets are less susceptible to spray drift than smaller ones, but
they require more carrier liquid per unit of land covered. In order to minimize losses due
to spray drift, sprayer application systems are designed to dispense a coarse droplet spec-
trum, whereby droplets can settle and make rapid contact with the surfaces they find (land
surface or leaves). Nevertheless, although the equipment nozzles are carefully designed to
optimize the droplet size, a fraction of the pesticide applied will always be lost and passed
into the air. This fraction of the applied pesticide may have the potential to cause nontar-
get crop damage as well as pose risks to human health and more sensitive ecosystems
(Ramaprasad et al. 2004).
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