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Environmental fate & pathways

Additional information on environmental fate and behaviour

Administrative data

Endpoint:
additional information on environmental fate and behaviour
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
June 2008-
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non-guideline compliant experimenta study

Data source

Reference
Reference Type:
publication
Title:
Resuspension behaviour of aluminium treated lake sediments: effects of ageing and pH
Author:
Egemose S, Wauer G, Kleeberg A
Year:
2009
Bibliographic source:
Hydrobiologia 636:203–217

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Behaviour of aluminium in aquatic environment was studied in laboratory by adding Al2(SO3)4 to sediment core samples simultaneously with fresh suspended particulate matter to mimic sedimentation of lake water. Behaviour of Al was monitored for 4 months in undisturbed and disturbed (resuspension) conditions. Also, influence of pH on dissolved Al concentrations was studied.
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
sediment containing aluminium
IUPAC Name:
sediment containing aluminium
Details on test material:
Lake Möllen, NE Germany, is a shallow polymictic hard water lake (alkalinity 2.73 ± 0.95 mmol l-1). Due to a constantly high external phosphorous (P) load the lake was polytrophic in recent years. The lake was treated by aluminium sulphate Al2(SO4)3 to precipitate P in the water column and to prevent internal P loading.

Results and discussion

Any other information on results incl. tables

Experimental Al application (4.8 g m-2) resulted in a 1-cm thick Al layer on the sediment surface of the treated cores. The content of particulate Al equalled that of control after 4 months, while concentrations of dissolved Al equalled the control after two weeks. Biofilm was found to have a stabilizing effect on resuspension of Al. This maybe because Al floc structure may become better crystallized, or floc aged for 2–4 months may have surface areas matching more crystallized Al forms, or Al flocs may become stabilized and successive incorporated in the biofilm or Al may form complexes with humic matter which can further enhanced the stabilization.In general, added Al undergoes hydrolysis and polymerisation leading to size growth and agglutination of the floc stabilizing the sediment surface. This process is disordered by increasing pH. An elevated pH leads to higher dissolved Al concentrations, as Al(OH)3 only dominates at pH 6–8 whereas higher pH leads to dissolution of the floc.

Applicant's summary and conclusion

Conclusions:
In shallow Al-treated lakes prone to resuspension, the Al floc is very mobile and easy to resuspend during the first days and weeks after treatment and could potentially be relocated in the lake. With ageing the floc stability increases within 2–4 months to the same level as natural lake sediment depending on the biofilm extension.
Executive summary:

Behaviour of aluminium in aquatic environment was studied in laboratory in non-GLP, non-guideline study. Al2(SO3)4 was added to intact sediment core samples simultaneously with fresh suspended particulate matter to mimic sedimentation of lake water. This mixture was gently added to the cores without disturbing the sediment surface. Two cores were left as control cores not treated with Al. An open erosion chamber (microcosm) was used for determining resuspension and lake water was continuously pumped through it by a peristaltic pump. Concentrations of dissolved Al and particulate Al were determined. The content of particulate Al equalled that of control after 4 months, while concentrations of dissolved Al equalled the control after two weeks. Biofilm was found to have a stabilizing effect on resuspension of Al. Even though Al was mobile and easy to resuspend during the first days and weeks after treatment the floc stability increases within 2–4 months to the same level as natural lake sediment.