254
K. M. G. Mostofa et al.
otherwise recalcitrant to biological and chemical degradation in natural waters
(Zepp et al. 1987; Miller and Chin 2002; Haag and Yao 1992; Vione et al.
2009; Grannas et al. 2006; Pullin et al. 2004; Draper and Crosby 1984; Ollis
et al. 1991; Sun and Pignatello 1993; Zimbron and Reardon 2005).
(ii) Degradation of organic pollutants or DOM in natural waters (Brezonik and
Fulkerson-Brekken 1998; Southworth and Voelker 2003; White et al. 2003;
Westerhoff et al. 1999; Goldstone et al. 2002; Kang et al. 2000; Gao and
Zepp 1998; Arslan et al. 1999; Katsumata et al. 2006; Muñoz et al. 2006;
Farias et al. 2010). Suwannee River Fulvic Acid (SRFA) can produce H 2 O 2 ,
which can give HO
• by direct photolysis or through the Fenton reactions
(Fig. 9) (Southworth and Voelker 2003). The Fenton process can also be
exploited from a technological point of view. Recently, a new pilot-plant
solar reactor for the photo-Fenton treatment of waters containing toxic
organic substances has been developed. In this reactor, the combined photoinduced and thermal effects of sunlight can degrade 98.2 % of the initial
pollutant, for a reaction time of 180 min and a relatively low iron concentration (Farias et al. 2010).
(iii) A great interest is presently devoted to the utilization of HO
• in the Advanced
Oxidation Technology (AOT) for treatment of sewerage or industrial effluents,
as a help to achieve sustainable development (Safazadeh-Amiri et al. 1996,
1997; Arslan et al. 2000; Venkatadri and Peters 1993).
(iv) The cycling of metals occurs through various redox chemical reactions in
natural waters, to which HO
• gives a contribution (Faust 1994; Voelker et al.
1997; Jeong and Yoon 2005; Faust and Zepp 1993; Kwan and Voelker 2002;
Emmenegger et al. 2001).
(v) Photoinduced generation of HO
• upon nitrite and nitrate photolysis in natural
waters can cause hydroxylation, nitration and nitrosation reactions of many
aromatic compounds or organic contaminants (Matykiewiczová et al. 2007;
Torrents et al. 1997; Vione et al. 2003a, b, 2004). Some of the reaction intermediates are mutagenic or carcinogenic and are, therefore, of immense environmental concern in the water bodies.
(vi) The HO
• radical is for instance involved in the ultrasonically induced oxidation of arsenite, which plays a key role in the conversion of As(III) in aqueous
media and may be applicable as a pretreatment step for the removal of arsenic
from water (Xu et al. 2005).
6 Impact of Free Radicals on Biota (Proteins and Living
Cells) and Plants
Free radicals are an unavoidable by-product in biological systems and can
arise from foods containing unnecessary fat, smoking, alcohol, H 2 O 2 , ozone,
toxins including the carcinogenic ones, ionization, environmental pollutants
K. M. G. Mostofa et al.
otherwise recalcitrant to biological and chemical degradation in natural waters
(Zepp et al. 1987; Miller and Chin 2002; Haag and Yao 1992; Vione et al.
2009; Grannas et al. 2006; Pullin et al. 2004; Draper and Crosby 1984; Ollis
et al. 1991; Sun and Pignatello 1993; Zimbron and Reardon 2005).
(ii) Degradation of organic pollutants or DOM in natural waters (Brezonik and
Fulkerson-Brekken 1998; Southworth and Voelker 2003; White et al. 2003;
Westerhoff et al. 1999; Goldstone et al. 2002; Kang et al. 2000; Gao and
Zepp 1998; Arslan et al. 1999; Katsumata et al. 2006; Muñoz et al. 2006;
Farias et al. 2010). Suwannee River Fulvic Acid (SRFA) can produce H 2 O 2 ,
which can give HO
• by direct photolysis or through the Fenton reactions
(Fig. 9) (Southworth and Voelker 2003). The Fenton process can also be
exploited from a technological point of view. Recently, a new pilot-plant
solar reactor for the photo-Fenton treatment of waters containing toxic
organic substances has been developed. In this reactor, the combined photoinduced and thermal effects of sunlight can degrade 98.2 % of the initial
pollutant, for a reaction time of 180 min and a relatively low iron concentration (Farias et al. 2010).
(iii) A great interest is presently devoted to the utilization of HO
• in the Advanced
Oxidation Technology (AOT) for treatment of sewerage or industrial effluents,
as a help to achieve sustainable development (Safazadeh-Amiri et al. 1996,
1997; Arslan et al. 2000; Venkatadri and Peters 1993).
(iv) The cycling of metals occurs through various redox chemical reactions in
natural waters, to which HO
• gives a contribution (Faust 1994; Voelker et al.
1997; Jeong and Yoon 2005; Faust and Zepp 1993; Kwan and Voelker 2002;
Emmenegger et al. 2001).
(v) Photoinduced generation of HO
• upon nitrite and nitrate photolysis in natural
waters can cause hydroxylation, nitration and nitrosation reactions of many
aromatic compounds or organic contaminants (Matykiewiczová et al. 2007;
Torrents et al. 1997; Vione et al. 2003a, b, 2004). Some of the reaction intermediates are mutagenic or carcinogenic and are, therefore, of immense environmental concern in the water bodies.
(vi) The HO
• radical is for instance involved in the ultrasonically induced oxidation of arsenite, which plays a key role in the conversion of As(III) in aqueous
media and may be applicable as a pretreatment step for the removal of arsenic
from water (Xu et al. 2005).
6 Impact of Free Radicals on Biota (Proteins and Living
Cells) and Plants
Free radicals are an unavoidable by-product in biological systems and can
arise from foods containing unnecessary fat, smoking, alcohol, H 2 O 2 , ozone,
toxins including the carcinogenic ones, ionization, environmental pollutants