45
biodegradation process. Atrazine was found to adsorb to humic acids and clays and
to the various interrelated physical and chemical mechanisms of soil (MoreauKervévan and Mouvet 1998). Nitrogen compounds have been shown to have negative effect on atrazine degradation by numerous bacterial strains tested in pure
cultures and in soil (Alvey and Crowley 1995; Entry et al. 1993; Garces et al. 2007).
However, Agrobacterium radiobacter J14a (Bichat et al. 1999) and Arthrobacter sp.
SC-JAK2 (Rajendran et al. 2018, 2019) are not influenced by the simultaneous presence of ammonium, nitrate, and urea in the growth medium. Atrazine-degrading
enzymes are inducible in resting cells, if cells are acclimated in media containing
growth-limiting nitrogen source, atrazine, or a pathway metabolite. However, their
presence in media containing other nitrogen sources did not stimulate the atrazine
degradation indicating that these microorganisms prefer the other nitrogen sources
for their growth and metabolism. Low atrazine biodegradation is mainly attributed
to its low water solubility and migration to soil pores inaccessible to microorganisms. Although addition of surfactants enhances their solubility, they inhibit the
microbial activity. Atrazine mineralization rate increases with the increase of water
content up to 40% of field capacity. Mineralization was proportional to the organic
matter content of the soils and oxygen content. Atrazine mineralization was found
to be much slower under denitrifying conditions (Nair and Schnoor 1994). In spite
of the presence of significant populations of native atrazine-degrading microorganisms, their ability to significantly degrade the atrazine under complex environmental conditions appears to be limited.
2.4 Nanotechnology in Removal of S-Triazine Pesticides
Nanoscale materials are of significant research interest over the past several years
because of their improved properties when compared to their bulk form.
Nanomaterials including silver, titanium dioxide, and zinc oxide were used as photocatalysts for the heterogeneous degradation of pesticides. Zero-valent metals have
been extensively researched for their usage in environmental remediation due to the
strong reductive activity. Iron-based nanomaterials have obtained considerable
attention in environmental remediation due to their high specific surface area, superparamagnetism, non-toxic and economic characteristics, and abundance. There is a
concern on the usage of most nanomaterials intended for environmental application
due to their toxicological effects on different biological systems. At present, only
iron nanoparticles are considered to be safe for the environmental usage and bioremediation purpose. Some of the nanoparticles developed for s-triazine pesticide
degradation or removal are presented in Table 2.3.
2 Biodegradation and Bioremediation of S-Triazine Herbicides
biodegradation process. Atrazine was found to adsorb to humic acids and clays and
to the various interrelated physical and chemical mechanisms of soil (MoreauKervévan and Mouvet 1998). Nitrogen compounds have been shown to have negative effect on atrazine degradation by numerous bacterial strains tested in pure
cultures and in soil (Alvey and Crowley 1995; Entry et al. 1993; Garces et al. 2007).
However, Agrobacterium radiobacter J14a (Bichat et al. 1999) and Arthrobacter sp.
SC-JAK2 (Rajendran et al. 2018, 2019) are not influenced by the simultaneous presence of ammonium, nitrate, and urea in the growth medium. Atrazine-degrading
enzymes are inducible in resting cells, if cells are acclimated in media containing
growth-limiting nitrogen source, atrazine, or a pathway metabolite. However, their
presence in media containing other nitrogen sources did not stimulate the atrazine
degradation indicating that these microorganisms prefer the other nitrogen sources
for their growth and metabolism. Low atrazine biodegradation is mainly attributed
to its low water solubility and migration to soil pores inaccessible to microorganisms. Although addition of surfactants enhances their solubility, they inhibit the
microbial activity. Atrazine mineralization rate increases with the increase of water
content up to 40% of field capacity. Mineralization was proportional to the organic
matter content of the soils and oxygen content. Atrazine mineralization was found
to be much slower under denitrifying conditions (Nair and Schnoor 1994). In spite
of the presence of significant populations of native atrazine-degrading microorganisms, their ability to significantly degrade the atrazine under complex environmental conditions appears to be limited.
2.4 Nanotechnology in Removal of S-Triazine Pesticides
Nanoscale materials are of significant research interest over the past several years
because of their improved properties when compared to their bulk form.
Nanomaterials including silver, titanium dioxide, and zinc oxide were used as photocatalysts for the heterogeneous degradation of pesticides. Zero-valent metals have
been extensively researched for their usage in environmental remediation due to the
strong reductive activity. Iron-based nanomaterials have obtained considerable
attention in environmental remediation due to their high specific surface area, superparamagnetism, non-toxic and economic characteristics, and abundance. There is a
concern on the usage of most nanomaterials intended for environmental application
due to their toxicological effects on different biological systems. At present, only
iron nanoparticles are considered to be safe for the environmental usage and bioremediation purpose. Some of the nanoparticles developed for s-triazine pesticide
degradation or removal are presented in Table 2.3.
2 Biodegradation and Bioremediation of S-Triazine Herbicides