Environmental Engineering Reference
In-Depth Information
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 mecha-
nisms and the controlling factors for formation and decay, as well as their signifi-
cance 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:
2H 2 O 2 2H 2 O + O 2
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 pro-
cesses. 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:
(iii) H 2 O 2 is the most stable reactive oxygen species (ROS) and is used as an indi-
cator of photoinduced activity, because it is for instance photolytically generated
through irradiation of various dissolved organic matter (DOM) components in nat-
ural 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 ). (iii) 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 envi-
ronments (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 natu-
ral 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 ). (vii) 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
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