141
Photoinduced and Microbial Generation of Hydrogen Peroxide
Despite the universal and unique functions that H 2 O 2 and ROOH may play in
water ecosystems, their roles on some key biogeochemical functions in natural
waters have hardly been investigated. This chapter will provide a general overview
on the biogeochemical functions of H 2 O 2 and ROOH, their production mechanisms and the controlling factors for formation and decay, as well as their significance and impact in natural waters.
1.1 Hydrogen Peroxide and its Biogeochemical Functions
Hydrogen peroxide (H 2 O 2 ) is a simple chemical compound (H–O–O–H) that
appears like water (H–O–H) in its chemical formula, with an additional oxygen
atom. Hydrogen peroxide can undergo dismutation into water and oxygen:
H 2 O 2 is a universal constituent of the hydrosphere and occurs in freshwater,
seawater, mineral water, rain, dew, cloud, snow, air, and in all living organisms.
H 2 O 2 also finds effective application in experiments as well as in treatment processes. It acts as an useful indicator for a variety of photoinduced, biological and
abiotic processes in the aquatic environment.
The various biogeochemical functions of H 2 O 2 can be classified as follows:
(i) H 2 O 2 is the most stable reactive oxygen species (ROS) and is used as an indicator of photoinduced activity, because it is for instance photolytically generated
through irradiation of various dissolved organic matter (DOM) components in natural waters (Cooper and Zika 1983; Zika et al. 1985a, b; Mostofa and Sakugawa
2009; Obernosterer et al. 2001; Fujiwara et al. 1993; Moore et al. 1993; Scully et
al. 1996). (ii) H 2 O 2 and its precursor superoxide (O 2
•−
) can be both oxidising and
reducing agents and are, therefore, potentially important for a number of redox
reactions in natural waters (Moffett and Zika 1987a, b; Petasne and Zika 1987;
Moffett and Zafiriou 1990; Zafiriou 1990; Zepp et al. 1992; Zafiriou et al. 1998;
Voelker et al. 2000; Jeong and Yoon 2005). (iii) H 2 O 2 is a natural tracer of the
surface-water mixing zone or of stratification processes in lake and marine environments (Johnson et al. 1989; Sikorsky and Zika 1993a, b; Sarthou et al. 1997;
Scully and Vincent 1997). (iv) H 2 O 2 is an indicator of the photodegradation of
dissolved organic matter (DOM) and of organic pollutants in surface natural waters (Gao and Zepp 1998; Westerhoff et al. 1999; Southworth and Voelker
2003). (v) H 2 O 2 is involved in oxidative stress in biota/living cells, because of its
elevated reactivity by both oxidation and reduction (Berlett and Stadtman 1997;
Paradies et al. 2000; Blokhina et al. 2003; Richard et al. 2007). (vi) H 2 O 2 can be
helpful in the identification of biological activity, in particular in coastal waters
where higher biological activity with rapid decay of H 2 O 2 is commonly observed
compared to the open oceans (Fujiwara et al. 1993; Moffett and Zafiriou 1990;
Cooper and Zepp 1990; Petasne and Zika 1997). (vii) H 2 O 2 is a useful tracer of
the vertical advection transport or the convective overturn, which is usually caused
2H 2 O 2 → 2H 2 O + O 2
Photoinduced and Microbial Generation of Hydrogen Peroxide
Despite the universal and unique functions that H 2 O 2 and ROOH may play in
water ecosystems, their roles on some key biogeochemical functions in natural
waters have hardly been investigated. This chapter will provide a general overview
on the biogeochemical functions of H 2 O 2 and ROOH, their production mechanisms and the controlling factors for formation and decay, as well as their significance and impact in natural waters.
1.1 Hydrogen Peroxide and its Biogeochemical Functions
Hydrogen peroxide (H 2 O 2 ) is a simple chemical compound (H–O–O–H) that
appears like water (H–O–H) in its chemical formula, with an additional oxygen
atom. Hydrogen peroxide can undergo dismutation into water and oxygen:
H 2 O 2 is a universal constituent of the hydrosphere and occurs in freshwater,
seawater, mineral water, rain, dew, cloud, snow, air, and in all living organisms.
H 2 O 2 also finds effective application in experiments as well as in treatment processes. It acts as an useful indicator for a variety of photoinduced, biological and
abiotic processes in the aquatic environment.
The various biogeochemical functions of H 2 O 2 can be classified as follows:
(i) H 2 O 2 is the most stable reactive oxygen species (ROS) and is used as an indicator of photoinduced activity, because it is for instance photolytically generated
through irradiation of various dissolved organic matter (DOM) components in natural waters (Cooper and Zika 1983; Zika et al. 1985a, b; Mostofa and Sakugawa
2009; Obernosterer et al. 2001; Fujiwara et al. 1993; Moore et al. 1993; Scully et
al. 1996). (ii) H 2 O 2 and its precursor superoxide (O 2
•−
) can be both oxidising and
reducing agents and are, therefore, potentially important for a number of redox
reactions in natural waters (Moffett and Zika 1987a, b; Petasne and Zika 1987;
Moffett and Zafiriou 1990; Zafiriou 1990; Zepp et al. 1992; Zafiriou et al. 1998;
Voelker et al. 2000; Jeong and Yoon 2005). (iii) H 2 O 2 is a natural tracer of the
surface-water mixing zone or of stratification processes in lake and marine environments (Johnson et al. 1989; Sikorsky and Zika 1993a, b; Sarthou et al. 1997;
Scully and Vincent 1997). (iv) H 2 O 2 is an indicator of the photodegradation of
dissolved organic matter (DOM) and of organic pollutants in surface natural waters (Gao and Zepp 1998; Westerhoff et al. 1999; Southworth and Voelker
2003). (v) H 2 O 2 is involved in oxidative stress in biota/living cells, because of its
elevated reactivity by both oxidation and reduction (Berlett and Stadtman 1997;
Paradies et al. 2000; Blokhina et al. 2003; Richard et al. 2007). (vi) H 2 O 2 can be
helpful in the identification of biological activity, in particular in coastal waters
where higher biological activity with rapid decay of H 2 O 2 is commonly observed
compared to the open oceans (Fujiwara et al. 1993; Moffett and Zafiriou 1990;
Cooper and Zepp 1990; Petasne and Zika 1997). (vii) H 2 O 2 is a useful tracer of
the vertical advection transport or the convective overturn, which is usually caused
2H 2 O 2 → 2H 2 O + O 2