Pesticide Residues in the Atmosphere - Pesticides: Evaluation of Environmental Pollution - page 217

Unsworth et al. 1999; Bidleman et al. 2006; Hageman et al. 2006). Fewer studies have focused
on pesticides in fog and snow (e.g., Hageman et al. 2006).
Except for persistent pesticides, the highest pesticide concentration, both in air and in
rainwater, will generally be located in the immediate surroundings of the application area.
In this respect, however, one must always keep in mind the importance not only of the
meteorology (wind direction, wind speed, etc.), which can help distribute or dissipate the
pesticide, but also of the physicochemical properties of the pesticide itself.
Moreover, studies on pesticides in the atmosphere indicate a seasonal behavior related
to application periods and use patterns in areas within tens of kilometers of the sam-
pling sites. This implies limited local transport (Scheyer et al. 2007b; Coupe et al. 2000).
LRT is observed mainly in the case of persistent compounds, such as a large number of
organochlorines.
The agricultural use of pesticides is well documented. By contrast, the urban use of pesti-
cides, for example, their applications in houses, gardens, cemeteries, roadways, or industrial
settings, are poorly documented. As a result, comparisons between urban and rural pesticide
monitoring are usually complicated. In many cases, the distribution between air and
precipitation in urban and rural areas is quite different. Most studies point to higher pesticide
concentrations on agricultural or rural sites than in urban areas, as expected. Apart from this,
there are also differences in the pesticides detected, except on urban sites close to the agricul-
tural areas where the same pesticides are usually detected for both rural and urban sites (e.g.,
Peck and Hornbuckle 2005; Chevreuil et al. 1996; Shummer et al. 2010; see Tables 7.2 and 7.3).
The fate, behavior, and transport of pesticides in the atmosphere are strongly affected
by the distribution of the compounds in the different phases: air, water, and particles. As
commented in the Introduction section, a great number of pesticides can undergo photo-
chemical transformations in relation to the presence and concentration of other pollutants,
such as ozone or VOCs, which are typically present in higher concentrations on urban
sites. The partitioning between the different phases of the atmosphere has an important
influence on the removal rate and the LRT or medium-range transport of the pesticides
(Schummer et al. 2010; Shen et al. 2005).
The presence of pesticides in urban air and rainwater is strongly related to atmospheric
transport from rural areas of significant agricultural importance. The persistent pesti-
cides, for example, the organochlorine pesticides, dacthal, and triazines (atrazine, cyani-
zine, etc.), represent a special case because of their well-known potential to undergo LRT
(Wania et al. 2005; Yao et al. 2008; Daly et al. 2007; Chevreuil et al. 1996).
7.4.1 Pesticides in the Air
Air samples are collected with high-volume samplers or passive samplers. The particle
phase and the gas phase can or cannot be sampled together, depending on the study.
The most used system for the gas phase is Amberlite XAD TM adsorbent resins (XAD-2).
Some studies used polyurethane foam cartridges (PUF) with XAD-2 or XAD-4 resin. The
particle phase is usually sampled on glass fiber filters. For active sampling, the sampling
time is usually 24 h. The treatment and analysis methods change from one study to another.
Depending on the compounds, Gas chromatography coupled with Mass spectrometry
(GC-MS) or Liquid chromatography coupled with mass spectrometry (LC-MS) can be cho-
sen for the analysis. Sampling sites and the period of the year are very important factors
to be considered because they can determine significant differences in the concentration
levels detected (e.g., Scheyer et al. 2007a; Yao et al. 2008). A more detailed review of the air
sampling methods used for pesticides can be found in Yusà et al. (2009).