Environmental Engineering Reference
In-Depth Information
6.1 Acid Rain
H
2
O
2
and ROOH compounds are key components in the conversion of dissolved
sulfur dioxide (SO
2
) to sulfate (SO
4
2
−
) or sulfuric acid (H
2
SO
4
) in atmospheric
clouds (Sakugawa et al.
1990
; Zuo and Hoigné
1993
). Sulfuric acid (SO
4
2
−
) can
be formed in cloud drops by reaction of HSO
3
−
with H
2
O
2
(Eq.
3.7
) and is a
major contributor to acid precipitation to the earth surface.
6.2 Inhibition of Photosynthetic Electron Transport in Cells
of Cyanobacteria
H
2
O
2
can control a large number of stages of cell metabolism, including those
involved in the induction of programmed cell death (Samuilov et al.
2001
). H
2
O
2
can inhibit growth at concentrations as low as 10
−
5
-10
−
4
M under the conditions
of a dialysis culture (Samuilov et al.
2001
). H
2
O
2
can inhibit the photosynthetic
electron transport in cells of cyanobacteria (Samuilov et al.
2001
,
2004
). It can
also destroy the function of the oxygen-evolving complex (OEC) in some chlo-
roplasts and photosystem II preparations, causing release of manganese from the
cyanobacterial cells, which inhibits the OEC activity.
6.3 Impact of H
2
O
2
on Bacterial Growth in Aquatic
Ecosystems
Bacterial growth has a seasonal variability, reaching the maximum in spring to
early summer and greatly decreasing in summer, e.g. when water temperature in
lakes becomes higher than 25.5 °C (Zhao et al.
2003
). Sunlight inactivates bacte-
ria in seawater (Fujioka et al.
1981
), which suggests that some photoinduced pro-
cesses may be involved. The bacterial abundance is commonly affected by water
temperature (Zhao et al.
2003
; Darakas
2002
), but the latter is directly connected
with solar radiation that can generate strong oxidizing agents such as peroxides
(H
2
O
2
and ROOH), O
2
• -
and HO
•
. These reactive species can reduce the activity
of the catalase, peroxidase and superoxide dismutase enzymes present in bacterial
cells, DOM, algae and phytoplankton. Bacterial cells protect themselves from the
oxidizing species (H
2
O
2
, O
2
• -
and HO
•
) by adjusting the level of their enzymes
(Chance et al.
1979
). An experimental study conducted on marine invertebrates
suggests that H
2
O
2
-scavenging enzymes can protect against external photodynamic
effects and internal respiratory by-products (Dykens
1984
). It can be assumed that
the activity of the enzymes in dealing with the external effects would decrease their
ability to scavenge the internal by-products, with harmful effects for the organisms.
Low levels of H
2
O
2
(~100 nM) affect oxidative stress to bacteria in coastal waters
