193
Photoinduced and Microbial Generation of Hydrogen Peroxide
by increasing the concentration of the catalase enzyme. The diurnal periodicity of
catalase activity matched the diurnal changes of H 2 O 2 (Clark et al. 2008; Angel et
al. 1999). The effects of H 2 O 2 and peroxides can be particularly important during
the summer season when their levels are higher. Moreover, ozone hole events in
Antarctic waters may greatly increase photodegradation processes that can generate reactive free radicals and peroxides, with a damaging influence on biogeochemical cycles in Antarctic waters (Diffey 1991; Smith et al. 1992; Randall et al. 2005).
6.4 Impacts of H 2 O 2 on Microbial Quality of Recreational
Bathing Waters
Microbial water quality is assessed from the concentration of fecal indicator bacteria
(FIB) because of their adverse health effects (Cabelli et al. 1979; US Environmental
Protection Agency 2000; Wade et al. 2003. Frequent FIB contamination episodes in
the surf zone resulted in multiple beach closures in the USA (Boehm et al. 2002). It is
shown that elevated levels of H 2 O 2 , ROOH, superoxide (O 2
•− ) and hydroxyl radical,
photolytically produced, can cause damage and cell lysis in microorganisms. This
may result into high FIB mortality in recreational bathing waters (Gonzalez-Flecha
and Demple 1997; Weinbauer and Suttle 1999; Mitchell and Chamberlin 1975; Clark
et al. 2008). It is estimated that approximately ~100 nM of H 2 O 2 can cause oxidative
stress to bacteria in waters (Angel et al. 1999). Diurnal cycles of FIB mortality in the
surf zone (Clark et al. 2008; Boehm et al. 2002), which well resemble the diurnal
cycle of H 2 O 2 , suggest that the FIB mortality may be linked to the photoinduced generation of H 2 O 2 and ROOH in sunlit surface waters.
7 Role of H 2 O 2 in the Origin of Autochthonous DOM
and of other Oxidising Agents
H 2 O 2 can contribute to the production of autochthonous DOM by different important processes. First, it is involved in the photosysthesis process that is a major
source of organic matter (e.g. algae) (Mostofa et al. 2009a, b). The photoinduced
and microbial assimilation of organic matter, including algae, can produce autochthonous DOM in natural waters (Mostofa et al. 2009b; Fu et al. 2010; Harvey
et al. 1995; Carrillo et al. 2002; Coble 2007; Yamashita and Tanoue 2004;
Yamashita and Tanoue 2008). Coherently, a correlation has been observed between
production of organic carbon and concentration of photolytically formed H 2 O 2
(Anesio et al. 2005). The autochthonous production of DOM (Mostofa et al. 2005;
Yoshioka et al. 2002) is typically observed during the summer season, and a major
DOM component that is produced is autochthonous fulvic acid, often termed
sedimentary fulvic acid (Hayase and Tsubota 1985). Other produced compounds
include marine humic substances (Coble 1996, 2007), carbohydrates and unknown
Photoinduced and Microbial Generation of Hydrogen Peroxide
by increasing the concentration of the catalase enzyme. The diurnal periodicity of
catalase activity matched the diurnal changes of H 2 O 2 (Clark et al. 2008; Angel et
al. 1999). The effects of H 2 O 2 and peroxides can be particularly important during
the summer season when their levels are higher. Moreover, ozone hole events in
Antarctic waters may greatly increase photodegradation processes that can generate reactive free radicals and peroxides, with a damaging influence on biogeochemical cycles in Antarctic waters (Diffey 1991; Smith et al. 1992; Randall et al. 2005).
6.4 Impacts of H 2 O 2 on Microbial Quality of Recreational
Bathing Waters
Microbial water quality is assessed from the concentration of fecal indicator bacteria
(FIB) because of their adverse health effects (Cabelli et al. 1979; US Environmental
Protection Agency 2000; Wade et al. 2003. Frequent FIB contamination episodes in
the surf zone resulted in multiple beach closures in the USA (Boehm et al. 2002). It is
shown that elevated levels of H 2 O 2 , ROOH, superoxide (O 2
•− ) and hydroxyl radical,
photolytically produced, can cause damage and cell lysis in microorganisms. This
may result into high FIB mortality in recreational bathing waters (Gonzalez-Flecha
and Demple 1997; Weinbauer and Suttle 1999; Mitchell and Chamberlin 1975; Clark
et al. 2008). It is estimated that approximately ~100 nM of H 2 O 2 can cause oxidative
stress to bacteria in waters (Angel et al. 1999). Diurnal cycles of FIB mortality in the
surf zone (Clark et al. 2008; Boehm et al. 2002), which well resemble the diurnal
cycle of H 2 O 2 , suggest that the FIB mortality may be linked to the photoinduced generation of H 2 O 2 and ROOH in sunlit surface waters.
7 Role of H 2 O 2 in the Origin of Autochthonous DOM
and of other Oxidising Agents
H 2 O 2 can contribute to the production of autochthonous DOM by different important processes. First, it is involved in the photosysthesis process that is a major
source of organic matter (e.g. algae) (Mostofa et al. 2009a, b). The photoinduced
and microbial assimilation of organic matter, including algae, can produce autochthonous DOM in natural waters (Mostofa et al. 2009b; Fu et al. 2010; Harvey
et al. 1995; Carrillo et al. 2002; Coble 2007; Yamashita and Tanoue 2004;
Yamashita and Tanoue 2008). Coherently, a correlation has been observed between
production of organic carbon and concentration of photolytically formed H 2 O 2
(Anesio et al. 2005). The autochthonous production of DOM (Mostofa et al. 2005;
Yoshioka et al. 2002) is typically observed during the summer season, and a major
DOM component that is produced is autochthonous fulvic acid, often termed
sedimentary fulvic acid (Hayase and Tsubota 1985). Other produced compounds
include marine humic substances (Coble 1996, 2007), carbohydrates and unknown