7.10 Metals
Metal is worldwidely used for convenience in our life. On the other hand, it caused
serious problem in the society such as Minamata disease by exposure of organic
mercury (Hg) and Itai-itai disease by exposure of cadmium (Cd). In addition,
utilization of silver nanoparticles (AgNP) as antibacterial agents has become a new
environmental problem recently because of its environmental standard which has not
been regulated yet.
Because heavy metals are typically highly toxic and are not biodegradable, they
can easily remain in aquatic environments.
7.10.1 Cu
Assessment data for Cu by a microcosm test were reported by Dr. Sugiura. It was clear
that the system did not collapse with the addition of 1.2 mg/L of Cu during the stable
stage, although it collapsed with the addition of 0.4 mg/L during the initial stage of
succession. The bioactivity in the microcosm was high in the initial stage and low in
the stable stage of succession, indicating that the excretion amount is also high in the
initial stage and low in the stable stage. The toxicity of Cu was expressed by bonding
with organic matter in the microcosm. According to this, microorganisms survived,
and the system was maintained in the stable stage, even with high concentrations of Cu
being added. Organisms are susceptible to disturbance under high activity conditions,
while they are strong under low activities. It was suggested that the stability of the
system was maintained under coexisting and mutually poor conditions. The m-NOEC
of Cu was estimated to be 0.16 mg/L (Sugiura 2001, 2009).
7.10.2 Zn
The effect of zinc was investigated by Dr. Sugiura, and it was added when microcosm cultivation began (day 0); the populations of microorganisms and amounts of
respiration and production were tracked over time. The amount of production
became larger than that of the control system, but, with the addition of Zn, the
amount of respiration was not observed to change relative to the control system. The
P/R ratio was 1 when 19.2 mg/L of Zn was added and became completely overrespirated in the 153.3 mg/L addition system, and the system collapsed. The
m-NOEC of Zn was estimated to be 2.4 mg/L (Sugiura 2009) (Fig. 7.24).
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K. Murakami et al.
Metal is worldwidely used for convenience in our life. On the other hand, it caused
serious problem in the society such as Minamata disease by exposure of organic
mercury (Hg) and Itai-itai disease by exposure of cadmium (Cd). In addition,
utilization of silver nanoparticles (AgNP) as antibacterial agents has become a new
environmental problem recently because of its environmental standard which has not
been regulated yet.
Because heavy metals are typically highly toxic and are not biodegradable, they
can easily remain in aquatic environments.
7.10.1 Cu
Assessment data for Cu by a microcosm test were reported by Dr. Sugiura. It was clear
that the system did not collapse with the addition of 1.2 mg/L of Cu during the stable
stage, although it collapsed with the addition of 0.4 mg/L during the initial stage of
succession. The bioactivity in the microcosm was high in the initial stage and low in
the stable stage of succession, indicating that the excretion amount is also high in the
initial stage and low in the stable stage. The toxicity of Cu was expressed by bonding
with organic matter in the microcosm. According to this, microorganisms survived,
and the system was maintained in the stable stage, even with high concentrations of Cu
being added. Organisms are susceptible to disturbance under high activity conditions,
while they are strong under low activities. It was suggested that the stability of the
system was maintained under coexisting and mutually poor conditions. The m-NOEC
of Cu was estimated to be 0.16 mg/L (Sugiura 2001, 2009).
7.10.2 Zn
The effect of zinc was investigated by Dr. Sugiura, and it was added when microcosm cultivation began (day 0); the populations of microorganisms and amounts of
respiration and production were tracked over time. The amount of production
became larger than that of the control system, but, with the addition of Zn, the
amount of respiration was not observed to change relative to the control system. The
P/R ratio was 1 when 19.2 mg/L of Zn was added and became completely overrespirated in the 153.3 mg/L addition system, and the system collapsed. The
m-NOEC of Zn was estimated to be 2.4 mg/L (Sugiura 2009) (Fig. 7.24).
114
K. Murakami et al.