Environmental Engineering Reference
In-Depth Information
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 gener-
ate reactive free radicals and peroxides, with a damaging influence on biogeochem-
ical 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 gen-
eration 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 impor-
tant 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 autoch-
thonous 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
