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EC number: 208-901-2
CAS number: 546-46-3
(96h) LC50 0.4 mg/L (r-a from zinc metal)
on toxicity of trizinc dicitrate (CAS 546-46-3) to fish are available. A
96 h fish study is available for the parent acid of trizinc dicitrate,
citric acid 77-92 -9 with Leuciscus idus idus, showing the low acute
toxicity of the parent acid (96 h LC50 440 mg/L, Juhnke and Ludemann
1978, rel. 2).
dicitrate in solution is expected to behave similarly as citric acid and
zinc added into solution separately. The toxicity of citric acid 77-92-9
to D. magna is negligible, while the toxicity of zinc ion to
Oncorhynchus mykiss has been reported to be a 97 h LC50 value of 0.136
mg/L (WHO 1996, cited in Zinc metal RAR 2008); therefore the toxicity of
trizinc dicitrate 546-46-3 is going to be driven by the zinc counterion
and the assessment of this substance should be based on the toxicity of
toxicity of zinc to aquatic organisms has been reviewed in the Zinc
metal RAR (2008). The
authors of the Zinc metal RAR (2008) have reviewed all of the studies
available for zinc metal at the time and selected reliable studies. The
reliable studies in the zinc metal RAR (2008) report a range of LC50 for
fish in the range of 0.136 to 7.8 mg/L (as dissolved zinc).
taking into consideration the LC50 of zinc ions and neglecting the
citric acid LC50, the 96 h LC50 for Trizinc dicitrate with O. mykiss is
h LC50 for Zinc is 0.136 mg/L (Zinc RAR 2008), which is equivalent to a
96 h LC50 value of 0.163 * 2.93 = 0.4 mg/L of Trizinc dicitrate.
MW(trizinc dicitrate)/MW(zinc*3) = 574.37/(65.38*3) = 2.93]
known that abiotic factors can greatly influence the toxicity of Zn and
therefore the toxicity of trizinc dicitrate to aquatic species. For the
purpose of this assessment some specific factors can be singled out.
the most studied and important parameter. With increasing hardness Zn
becomes less bioavailable and thus less toxic because the zinc ions form
insoluble complexes with Ca and Mg ions. In a chronic study by
Paulauskis and Winner (1988) with D. magnait was demonstrated that by
increasing the total water hardness as CaCO3 y 50 to 200 mg/L, the NOEC
for reproduction increased 6 -fold, i.e. a decrease in toxicity. The
NOEC for survival was less affected
to hardness, with increasing pH the toxicity of Zn towards aquatic
organisms decreases since Zn becomes less bioavailable by binding to H+
ions. In a study from De Schamphelaere et al. (2003) it was demonstrated
that pH changed the toxicity to invertebrates by a factor of 3 to 4 with
D. magna, by a factor of 2 to 3 with rainbow trout Oncorhynchus mykiss,
and by a factor of >20 with the algae Pseudokirchneriella subcapitata.
However a clear relationship between toxicity and pH could not be
established with the exception of algae (Zinc metal RAR 2008).
background concentration of Zn will influence the test organism's
sucsceptibility to the metal. Higher background concentrations of zinc
ensure that the animals are more tolerant to zinc, and therefore a
decrease in toxicity is observed (e.g. Muyssen and Janssen, 2000 with D.
factors affecting the bioavailability and thus the ecotoxicity of Zn to
aquatic organisms are the DOC concentration (by Zn binding with the
organic carbon, Zinc metal RAR 2008) and alkalinity (by Zn binding with
the carbonates, Zinc metal RAR 2008).
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