Spent liquor from alkaline pulping and bleaching containing spent inorganic process chemicals and dissolved organic substances originating from the cellulosic raw material.

Toxicity to aquatic algae and cyanobacteria

Description of key information

- EC50 (72 h) value for Pseudokirchneriella subcapitata 38.2 mg/l (dwt.)  (72.4 mg/l (wwt.)) (growth rate) (OECD 201 and EU Method C.3)
- EC50 (72 h) value for Pseudokirchneriella subcapitata 75 mg/l (dwt.) (143 mg/l (wwt.) (growth rate) (OECD 201)
- NOEC (72 h) value for Pseudokirchneriella subcapitata 6.3 mg/l (dwt.) (12 mg/l (wwt.)) (growth rate) ( (OECD 201 and EU Method C.3)
- NOELr (72 h) value for Pseudokirchneriella subcapitata 2.6 mg/l (dwt.) (5 mg/l (wwt.))(growth rate) (OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

38.2 mg/L

EC10 or NOEC for freshwater algae:

2.6 mg/L

Additional information

Black liquor was toxic to aquatic algae that were to most sensitive organisms to Black liquor among the tested ones. The study results with lower reliability ranking supported the findings cited below (72h-EC50 from ca. 45 to 154 mg/l (wwt.)).

Due to the possible discolouring of the test media with Black liquor there is a risk of a false positive result in algae test, where algal growth depends on unlimited light penetration into the media. However, the risk of a false positive result in the referred results is considered to be low.

Algae:

EC50 (72 h) values for Pseudokirchneriella subcapitata were 38.2 mg/l and 75 mg/l (dwt.) (growth rate) (n=2).

NOEC (72 h) values for Pseudokirchneriella subcapitata were 6.3 mg/l and 2.6 mg/l (dwt.) (growth rate (n=2).