Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

NaOH is present in the environment as sodium and hydroxyl ions because NaOH is highly water soluble. Both sodium and hydroxyl ions have a wide natural occurrence and may come from many sources so it is not possible to quantitatively measure NaOH in the environment. In a global water monitoring program (UNEP, 1995) pH and sodium concentrations were two of parameters that were monitored in many lakes and rivers. The most important freshwater aquatic ecosystems of the world revealed average annual pH values between 6.5 and 8.3 but lower and higher values have been measured in other aquatic ecosystems. In aquatic ecosystems with dissolved organic acids a pH of less than 4.0 has been measured, while in waters with a high chlorophyll content the bicarbonate assimilation can result in pH values of higher than 9.0 at midday. The global mean pH value is 7.7. Within this range the bicarbonate ion is the most common carbonate species found in natural waters. In streams ( 100 km2) bicarbonate concentrations range from 0 to 350 mg/l, while in major rivers (> 100,000 km2) the concentration ranges from 10 to 170 mg/l. Sodium concentrations in lakes and rivers display strong variability and originate from natural weathering of rock, from atmospheric transport of oceanic inputs and from a wide variety of anthropogenic sources. Sodium concentrations in European rivers range between 1.2 and 574 mg/l.