SODIUM CARBONATE CAS N°: 497-19-8 - UNEP Chemicals

OECD SIDS SODIUM CARBONATE
the protection of fish should be between 6 and 9. In section 2.1 it has been mentioned that the 10 th -
percentile and the 90 th -percentile of the bicarbonate concentrations of 77 rivers were 20 and 195
mg/l, respectively. If it is assumed that only bicarbonate is responsible for the buffer capacity of the
ecosystem and if it is assumed that an increase of the pH to a value of 9.0 would be the maximum
accepted value then the acceptable anthropogenic addition of sodium carbonate would be 2.7 and 17
mg/l for bicarbonate concentrations of 20 and 195 mg/l, respectively (see Table 1). This gives an
indication of the order of magnitude of the acceptable amount of sodium carbonate which could be
discharged to an aquatic ecosystem if there was an emission of a pure sodium carbonate solution.
Sodium carbonate concentrations of 2.7 and 17 mg/l are equivalent with the sodium concentrations
of 1.2 and 7.4 mg/l. Sodium concentrations of 1.2 to 7.4 have no effect on aquatic organisms
because sodium has a low toxicity for aquatic organisms. Reconstituted water of toxicity tests
contains for example sodium concentrations which range between 3.3 and 105 mg/l (ASTM, 1996).
Individual aquatic ecosystems are characterized by a specific pH and bicarbonate concentration and
the organisms of the ecosystem are adapted to these specific natural conditions. Based on the
natural pH and bicarbonate concentration of waters, organisms will have different optimum
conditions, ranging from poorly buffered waters with a pH of 6 or less to very hard waters with pH
values up to 9 (Bloemendaal et al., 1988). Beause the natural pH, bicarbonate and also the sodium
concentration (and their fluctuations in time) varies significantly between aquatic ecosystems, it is
not considered useful to derive a generic PNEC or PNECadded.
To assess the potential environmental effect of an sodium carbonate discharge, the increase in
sodium, bicarbonate and pH should be compared with the natural values and their fluctuations and
based on this comparison it should be assessed if the anthropogenic addition is acceptable.
4.2 Terrestrial effects
Toxicity tests which determined the effect of sodium carbonate on terrestrial organisms are not
available. Significant exposure to the terrestrial environment is not expected and for this reason
there is no need to perform a toxicity test with terrestrial organisms. The results of the tests will
depend strongly on the buffer capacity of the soil and can probably be predicted based on the buffer
capacity of the soil. Furthermore, carbonates are natural components of soil minerals.
4.3 Other environmental effects
No other environmental effects are expected.
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