Pesticide Residues in Vegetation - Pesticides: Evaluation of Environmental Pollution - page 303

as bioindicators of the pollution by the organochlorines in air. This study demonstrated
the high power of bioconcentration of this kind of compounds in plants, as compared with
their concentration in air (Granier and Chevreuil 1992).
In recent years, several studies have described the importance of vegetation as a pollut-
ant sink (Holoubek et al. 1999). Plants can adsorb as particles from soil and water and as
volatile compounds from air and suffer atmospheric deposition in their leaves, because of
which plant biomass plays an important role as an indicator of environmental pollution
(Barriada-Pereira et al. 2005).
According to a study about the estimation of the half-lives of pesticides, the degradation
of these compounds in plants is more efficient than in soil but slower than in air. Moreover,
the concentration of pesticides decreases vertically from the cuticle and their concentra-
tion in the cells of the subcuticle is often zero. It is because plants normally metabolize
pesticides, which become water-soluble compounds and other residues that are less toxic
or nontoxic for the plants (Juraske et al. 2008). Because of this, vegetation has been widely
used to mitigate or reduce the negative effects produced by the contaminants in a determi-
nate zone; this process is known as phytoremediation.
Numerous laboratory and field studies have established the importance of aquatic macro-
phytes and their associated phytoremediation processes as a mitigating and mobilizing fac-
tor of the organic contaminants in the environment. More concretely, the roles of those plant
communities have been widely studied for the creation of natural buffer zones designed to
mitigate the impacts of the pesticides associated with waters following runoff and spray
drift from agricultural areas. Moreover, rooted aquatic vegetation can aid in remobilizing
the pollutants from contaminated sediments. To sum up, phytoremediation processes can
mitigate the contaminants from soil, sediment, and water (Armitage et al. 2008).
Most of the compiled studies are focused on the POPs, and experimental studies are
predominant, which are carried out using manipulated plant samples in the laboratory.
There are a few studies about the presence of pesticides in natural vegetation, and those
performed studies are basically focused on the organochlorine pesticides, since they are
the most toxic and persistent ones.
10.2 Methodology
Many studies about pesticides in natural plants worldwide have been compiled, inde-
pendent of the date, sampling method, or analytical method used for the extraction and
determination of pesticide residues. The studies that were carried out in vegetation from
cultivated areas or the experimental studies in which the analyses were realized on the
samples from the plants previously treated with pesticides are not considered.
10.3 Results and Discussion
The data from a total of 636 pesticide concentrations in vegetation samples from 38 coun-
tries around the world have been compiled ( Table 10.1 ). The organochlorine pesticides
are the most studied, particularly dichloro-diphenyl-trichloroethane (DDT), considering