efficacy is most likely due to soil manipulation which leads
to the homogenization of the soil matrix. In addition,
soil manipulation offers the possibility to thoroughly mix it
and to apply the different bioremediation treatments
(biostimulation, bioaugmentation, etc.) in a control manner.
Indeed, ex situ treatments allow to control the principal
parameters that are regulating the activity of pesticidedegrading community such as degree of aeration, water
saturation, and nutrient supply. Ex situ treatment is applied
to treat punctual pollutions of soil due to accidental cause or
to treat high-level spots of contamination in a contaminated
site. Recently, it was suggested that following ex situ
treatments, treated soil can be used to construct a new soil
profile at the polluted site, named Technosol, made of
treated soil, recycled waste, and industrial by-products
(Sere et al. 2008; WRB IWG 2006). Mainly applied to
treat PAHs and heavy metal contamination, it was shown
that the abundance and the activity of N-cycling microbial
guilds in Technosols were in the same range as in the other
terrestrial ecosystems suggesting that construction of
Technosols is a promising technology for the restoration of
degraded lands and recycling of industrial wastes (Hafeez
et al. 2012). It has to be noticed that during the past two
decades, on-farm bioremediation devices designed to
effluents of pesticides have been developed and are now on
the market being recognized by the authorities as one of the
solution to treat pesticides effluents (for review, see De
Wilde et al. 2007).
Although bioremediation strategies are considered as
potentially simple and economically and environmentally
friendly, their effectiveness must be monitored. Monitoring
should be part of the bioremediation process (Megharaj et al.
2011). Usually it includes: (i) chemical analyses of the soil
under treatment to monitor pollutant dissipation and search
for possible metabolites formed during the process and (ii)
ecotoxicological analyses to test the impact of the treatment
on soil living organisms. Recently, several studies also
proposed to monitor the abundance and activity of
pollutant-degrading populations which are actively involved
in the bioremediation process but also to estimate the impact
of the bioremediation treatment on the overall soil biodiversity and, more particularly, on microbial diversity driving
important soil ecosystemic services (Petric et al. 2011).
A Study Case of Soil Bioremediation
Since its discovery in the early 1950s, the herbicide atrazine
belonging to the s-triazine family has largely been used in
Americas and in European countries to control the development of broadleaf weeds in corn crop. Almost ten years ago,
the use of atrazine was ban by the European Commission
(2004/248/EC) mainly in reason of the detection of atrazine
and of its main metabolites in water resources found in
higher amount than the authorized concentration (i.e.,
0.1 μg∙L
À1 , according to water framework directive
91/414/EC). It is noteworthy that atrazine still remains in
use in Americas where the US Environmental Protection
Agency (EPA) approved its continued use and in many
other countries worldwide. In France, atrazine was ban by
the French government in year 2003 after the observation of
widespread water pollution. Indeed, the French Agency for
the Environment (IFEN) reported the detection of atrazine
and its dealkylated metabolites in most of surface and
groundwater analyzed even 3 years after its ban (Annual
report of IFEN, 2006). Recent report on surface water
quality reports that almost ten years after atrazine ban, this
herbicide remains detected in 12 % of surface water
analyzed being the fifth pesticide the most frequently
detected. More disturbing desethyl-atrazine, one metabolite
of the atrazine, is found in 33 % of water resources in France,
being the second metabolite the most frequently found after
AMPA, resulting from partial glyphosate transformation
(Report 2013 with data obtained in 2011, French Ministry
of the Environment). Also, next to bioremediation studies
carried out on sites contaminated with petroleum residues,
atrazine is likely the pesticide for which many bioremediation techniques have been proposed and tested. In most of
the cases, these reports proposed prototype for atrazine
bioremediation tested under laboratory conditions using
both biostimulation and bioaugmentation approaches.
• Biostimulation approach for atrazine bioremediation
It has been shown that the occurrence of the phenomenon
of accelerated degradation for atrazine occurred only
under certain conditions of soil pH, the lower limit
value falling to 6.5 (Houot et al. 2000). In acidic soils, it
has been shown that liming allows stimulating atrazinedegrading-microbial community which cannot be
expressed at low pH in the unmodified soil. In several
soils, it has been shown that liming alone is not enhancing
atrazine degradation and must be associated with the
inoculation of an atrazine-degrading population to be
successful (Rousseaux et al. 2003). Demonstration that
environmental conditions rather than the presence of
microbial agents may be detrimental to the degradation
of atrazine was provided by another study reporting that
application of dairy effluent stimulated the activity of
atrazine-degrading bacterial community native soil of a
maize field (Topp et al. 1996). From this point of view,
it has been shown that not all the organic substrates are
promoting atrazine-degrading activity in soil (Barriuso
et al. 1997). Several of them like straw, manure, and
compost produce a two-step response on atrazinedegrading-microbial community: one could observe in
the early stages, immediately following the addition of
organic matter, an initial phase of stimulation of atrazine
degradation followed by a second stage during which
atrazine degradation is then slowed down, most likely
700
J.-C. Bertrand et al.
to the homogenization of the soil matrix. In addition,
soil manipulation offers the possibility to thoroughly mix it
and to apply the different bioremediation treatments
(biostimulation, bioaugmentation, etc.) in a control manner.
Indeed, ex situ treatments allow to control the principal
parameters that are regulating the activity of pesticidedegrading community such as degree of aeration, water
saturation, and nutrient supply. Ex situ treatment is applied
to treat punctual pollutions of soil due to accidental cause or
to treat high-level spots of contamination in a contaminated
site. Recently, it was suggested that following ex situ
treatments, treated soil can be used to construct a new soil
profile at the polluted site, named Technosol, made of
treated soil, recycled waste, and industrial by-products
(Sere et al. 2008; WRB IWG 2006). Mainly applied to
treat PAHs and heavy metal contamination, it was shown
that the abundance and the activity of N-cycling microbial
guilds in Technosols were in the same range as in the other
terrestrial ecosystems suggesting that construction of
Technosols is a promising technology for the restoration of
degraded lands and recycling of industrial wastes (Hafeez
et al. 2012). It has to be noticed that during the past two
decades, on-farm bioremediation devices designed to
effluents of pesticides have been developed and are now on
the market being recognized by the authorities as one of the
solution to treat pesticides effluents (for review, see De
Wilde et al. 2007).
Although bioremediation strategies are considered as
potentially simple and economically and environmentally
friendly, their effectiveness must be monitored. Monitoring
should be part of the bioremediation process (Megharaj et al.
2011). Usually it includes: (i) chemical analyses of the soil
under treatment to monitor pollutant dissipation and search
for possible metabolites formed during the process and (ii)
ecotoxicological analyses to test the impact of the treatment
on soil living organisms. Recently, several studies also
proposed to monitor the abundance and activity of
pollutant-degrading populations which are actively involved
in the bioremediation process but also to estimate the impact
of the bioremediation treatment on the overall soil biodiversity and, more particularly, on microbial diversity driving
important soil ecosystemic services (Petric et al. 2011).
A Study Case of Soil Bioremediation
Since its discovery in the early 1950s, the herbicide atrazine
belonging to the s-triazine family has largely been used in
Americas and in European countries to control the development of broadleaf weeds in corn crop. Almost ten years ago,
the use of atrazine was ban by the European Commission
(2004/248/EC) mainly in reason of the detection of atrazine
and of its main metabolites in water resources found in
higher amount than the authorized concentration (i.e.,
0.1 μg∙L
À1 , according to water framework directive
91/414/EC). It is noteworthy that atrazine still remains in
use in Americas where the US Environmental Protection
Agency (EPA) approved its continued use and in many
other countries worldwide. In France, atrazine was ban by
the French government in year 2003 after the observation of
widespread water pollution. Indeed, the French Agency for
the Environment (IFEN) reported the detection of atrazine
and its dealkylated metabolites in most of surface and
groundwater analyzed even 3 years after its ban (Annual
report of IFEN, 2006). Recent report on surface water
quality reports that almost ten years after atrazine ban, this
herbicide remains detected in 12 % of surface water
analyzed being the fifth pesticide the most frequently
detected. More disturbing desethyl-atrazine, one metabolite
of the atrazine, is found in 33 % of water resources in France,
being the second metabolite the most frequently found after
AMPA, resulting from partial glyphosate transformation
(Report 2013 with data obtained in 2011, French Ministry
of the Environment). Also, next to bioremediation studies
carried out on sites contaminated with petroleum residues,
atrazine is likely the pesticide for which many bioremediation techniques have been proposed and tested. In most of
the cases, these reports proposed prototype for atrazine
bioremediation tested under laboratory conditions using
both biostimulation and bioaugmentation approaches.
• Biostimulation approach for atrazine bioremediation
It has been shown that the occurrence of the phenomenon
of accelerated degradation for atrazine occurred only
under certain conditions of soil pH, the lower limit
value falling to 6.5 (Houot et al. 2000). In acidic soils, it
has been shown that liming allows stimulating atrazinedegrading-microbial community which cannot be
expressed at low pH in the unmodified soil. In several
soils, it has been shown that liming alone is not enhancing
atrazine degradation and must be associated with the
inoculation of an atrazine-degrading population to be
successful (Rousseaux et al. 2003). Demonstration that
environmental conditions rather than the presence of
microbial agents may be detrimental to the degradation
of atrazine was provided by another study reporting that
application of dairy effluent stimulated the activity of
atrazine-degrading bacterial community native soil of a
maize field (Topp et al. 1996). From this point of view,
it has been shown that not all the organic substrates are
promoting atrazine-degrading activity in soil (Barriuso
et al. 1997). Several of them like straw, manure, and
compost produce a two-step response on atrazinedegrading-microbial community: one could observe in
the early stages, immediately following the addition of
organic matter, an initial phase of stimulation of atrazine
degradation followed by a second stage during which
atrazine degradation is then slowed down, most likely
700
J.-C. Bertrand et al.