42
soils from Kochia scoparia and maize plants showed to accelerate mineralization of
atrazine (Perkovich et al. 1996; Piutti et al. 2002). Wang et al. (2012) used a hydroponic system to evaluate the potential of three emergent hydrophytes, Iris pseudacorus, Lythrum salicaria, and Acorus calamus for atrazine removal and uptake.
Schmidt et al. (2008) studied the biconversion of [
14
C] atrazine to hydroxyatrazine
and dealkylated products (de-ethyl-, deisopropyl- and de-ethyl- deisopropylatrazine)
in heteroirophic cell-suspension cultures of soyabean (Giycine max L. Merr), carrot
(Daucus caroia), purple foxglove (Digitalis purpurea), corn cockle (Agrostemma
githago), wheat (Tritician aestivum), and thorn-apple (Datura stramonium).
2.2.4 Abiotic Degradation of S-Triazine Herbicides
Several physicochemical methods are proposed for cleaning of atrazine from contaminated soils, water, and wastewater. These techniques include incineration,
reverse osmosis, electrodialysis, thermal absorption, ultraviolet, peroxides, and
metal oxides. Various adsorbents including hypercrosslinked polymers (Streat and
Horner 2000), zeolites, and organoclays (Bottero et al. 1994) have been studied for
the removal of atrazine. Chemical methods used for atrazine degradation are photolysis, hydrolysis, dehalogenation, and oxygenation. Chemical hydrolysis of atrazine produces hydroxyatrazine in strongly acidic or basic solutions. These
technologies are expensive and also release toxic by-products, which require further
treatments. Atrazine degradation is negligible by sunlight, i.e. direct photolysis and
result in the formation of hydroxyatrazine and dealkylated products of hydroxyatrazine. Photosensitisers such as dissolved organic carbon and nitrate absorb and transfer light energy (indirect photolysis) to catalyse the degradation of atrazine to form
cyanuric acid (Cessna 2008). Corrosive and toxic gases are formed during the incineration process according to the component of the pesticide incinerated. For example, pesticides containing chlorine can produce hydrochloric acid, and
nitrogen-containing pesticides can produce nitrogen oxide and nitrogen dioxide
during incineration. All the above gases are acidic and corrosive. These toxic
exhaust gases are to be treated before letting it out to the environment.
2.3 Bioremediation
Bioremediation refers to the process of detoxifying the contaminated environments
using microorganisms, plants, or their enzymes. This includes partial or complete
transformation (mineralisation) of the pollutant via biodegradation process.
Bioremediation is carried out by adding an enriched microbial culture capable of
degrading the pollutant or by stimulating the native xenobiotic degrading bacteria.
The major advantages of bioremediation process are that it is environment friendly
and cost-effective. Benoit et al. (1998) reported the immobilisation of atrazine by
K. Rajendran et al.
soils from Kochia scoparia and maize plants showed to accelerate mineralization of
atrazine (Perkovich et al. 1996; Piutti et al. 2002). Wang et al. (2012) used a hydroponic system to evaluate the potential of three emergent hydrophytes, Iris pseudacorus, Lythrum salicaria, and Acorus calamus for atrazine removal and uptake.
Schmidt et al. (2008) studied the biconversion of [
14
C] atrazine to hydroxyatrazine
and dealkylated products (de-ethyl-, deisopropyl- and de-ethyl- deisopropylatrazine)
in heteroirophic cell-suspension cultures of soyabean (Giycine max L. Merr), carrot
(Daucus caroia), purple foxglove (Digitalis purpurea), corn cockle (Agrostemma
githago), wheat (Tritician aestivum), and thorn-apple (Datura stramonium).
2.2.4 Abiotic Degradation of S-Triazine Herbicides
Several physicochemical methods are proposed for cleaning of atrazine from contaminated soils, water, and wastewater. These techniques include incineration,
reverse osmosis, electrodialysis, thermal absorption, ultraviolet, peroxides, and
metal oxides. Various adsorbents including hypercrosslinked polymers (Streat and
Horner 2000), zeolites, and organoclays (Bottero et al. 1994) have been studied for
the removal of atrazine. Chemical methods used for atrazine degradation are photolysis, hydrolysis, dehalogenation, and oxygenation. Chemical hydrolysis of atrazine produces hydroxyatrazine in strongly acidic or basic solutions. These
technologies are expensive and also release toxic by-products, which require further
treatments. Atrazine degradation is negligible by sunlight, i.e. direct photolysis and
result in the formation of hydroxyatrazine and dealkylated products of hydroxyatrazine. Photosensitisers such as dissolved organic carbon and nitrate absorb and transfer light energy (indirect photolysis) to catalyse the degradation of atrazine to form
cyanuric acid (Cessna 2008). Corrosive and toxic gases are formed during the incineration process according to the component of the pesticide incinerated. For example, pesticides containing chlorine can produce hydrochloric acid, and
nitrogen-containing pesticides can produce nitrogen oxide and nitrogen dioxide
during incineration. All the above gases are acidic and corrosive. These toxic
exhaust gases are to be treated before letting it out to the environment.
2.3 Bioremediation
Bioremediation refers to the process of detoxifying the contaminated environments
using microorganisms, plants, or their enzymes. This includes partial or complete
transformation (mineralisation) of the pollutant via biodegradation process.
Bioremediation is carried out by adding an enriched microbial culture capable of
degrading the pollutant or by stimulating the native xenobiotic degrading bacteria.
The major advantages of bioremediation process are that it is environment friendly
and cost-effective. Benoit et al. (1998) reported the immobilisation of atrazine by
K. Rajendran et al.