Reaction mass of calcium dihydroxide and calcium peroxide

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
The biodegradation is relevant to organic substances regardless of the environmental compartment in which this property is investigated. This endpoint is specifically needed for organic substances and less relevant for inorganic substances.
In aqueous solution, the calcium peroxide decomposes into hydrogen peroxide and calcium hydroxide. The hydrogen peroxide will subsequently further decompose into water and oxygen. Furthermore, the calcium hydroxide dissociates when brought into aqueous medium. The different chemical reactions are:
CaO2 + 2 H2O -> Ca2 + + 2 (OH)- + H2O2
H2O2 + H2O -> 2 H2O + O2
Ca(OH)2 -> Ca2 + + 2 OH-
Hydrogen peroxide has a short half-life in natural waters due to the activity of micro-organisms. Furthermore, hydrogen peroxide is continuously formed in the environment and is ubiquitous in fresh- and seawater at natural background concentrations from some micrograms to some tens of microgram per litre. On the other hand, in aqueous medium, calcium (di)hydroxide will be completely dissociated into its ions as the water solubility is relatively high compared to the environmental background concentration of calcium and due to dilution effects. Depending on the properties of the test medium, calcium (di)hydroxide will be strongly neutralised in the initial period after application, by formation of calcium carbonate which will dissociate into calcium and carbonate ions. These ions are naturally ubiquitous in the environment; calcium will be assimilated by species present in the water and is necessary to maintain a good chemical balance in soils, water and plants and carbonate will become part of the carbon cycle.

Transformation products:

yes

No.:

#1

No.:

#2

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study set-up and results are well documented and the study followed acceptable scientific principles.

Principles of method if other than guideline:

Diel changes in the hydrogen peroxide concentration in a northern temperated, oligotrophic lake were studied. Water samples were filtered and dark loss of hydrogen peroxide was studied as a function of time.

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on source and properties of surface water:

Location: Jacks Lake, Ontario, Canada
Calcium concentration: 14 mg Ca2+ per L
pH: 7.2
Phosphorous: 0.012 mg/L
DOC: 6.0 +/- 0.5 mg of C per L

Details on source and properties of sediment:

Not applicable

Details on inoculum:

A sample of lake water was taken and filtered through 64, 12, 5, 1 and 0.45 micrometre mesh sizes. The filtrates were used to study the dark decay of hydrogen peroxide.

Duration of test (contact time):

30 - 120 h

Initial conc.:

0.007 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

Lake water was sample with Erlenmeyer flasks submersed below the surface of the water (10 to 15 cm). Sampled water was filtered through 64, 12, 5, 1 and 0.45 micrometre mesh sizes. The filtrates were used to study the dark decay of hydrogen peroxide over several days or 3 to 4 half-lives.

Test performance:

The dark decay of hydrogen peroxide followed a first-order kinetics. The half-life increased considerably in filtrate of the 1 micrometre filter indicating that the picoplankton was primarily responsible for the biological component of hydrogen peroxide decay.

Compartment:

other: water, material (mass) balance

% Recovery:

100

Compartment:

water

DT50:

7.8 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Unfiltered lake water

Compartment:

water

DT50:

8.6 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Filtrates that passed through 64, 12 and 5 micrometre filters

Compartment:

water

DT50:

31 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Filtrate that passed through the 1 micrometre filter

Compartment:

water

DT50:

24 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Filtrate that passed the 0.45 micrometre filter

Transformation products:

no

Details on transformation products:

Hydrogen peroxide decomposes to water and oxygen.

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

no

Details on results:

No details

Results with reference substance:

Not applicable

Validity criteria fulfilled:

yes

Conclusions:

The half-life for dark decay of hydrogen peroxide in a natural lake water was approximately 8 hours.

Executive summary:

The biodegradation of hydrogen peroxide was tested in samples taken from a northern temperate, oligotrophic lake (Cooper and Lean 1989). The lake water was filtered through 64, 12, 5, 1 and 0.45 micrometre filters. The filtrates were stored in the dark and the hydrogen peroxide concentration was measured in regular intervals. The initial concentration of hydrogen peroxide formed by photochemical processes was approximately 0.007 mg/L (200 nM). The hydrogen peroxide concentration was followed over several days or three to four half-lives. The dark decay of hydrogen peroxide followed first-order kinetics and the resulting half-lives were 7.8 hours for unfiltered lake water, 8.6 hours for filtrates that passed the 64, 12 and 5 micrometre filters, 31 hours for filtrates that passed the 1 micrometre filter and 24 hours for filtrates that passed the 0.45 micrometre filter. It was concluded that the picoplankton (0.2 to 2 micrometre) was primarily responsible for the biological component of hydrogen peroxide decay.

Description of key information

Surface water: The substance is composed of calcium hydroxide and calcium peroxide. Calcium hydroxyde dissociates in calcium ion and hydroxyl ions, so calcium hydroxide will not exist as such in water. Calcium peroxide hydrolyses into calcium hydroxide and hydrogen peroxide. The biodegradation of hydrogen peroxide was assessed in lake water.

 

Surface water (H2O2): Key study. The biodegradation of hydrogen peroxide was tested in samples taken from a northern temperate, oligotrophic lake (Cooper and Lean 1989). The dark decay of hydrogen peroxide followed first-order kinetics and the resulting half-lives were 7.8 hours for unfiltered lake water, 8.6 hours for filtrates that passed the 64, 12 and 5 micrometre filters, 31 hours for filtrates that passed the 1 micrometre filter and 24 hours for filtrates that passed the 0.45 micrometre filter. It was concluded that the picoplankton (0.2 to 2 micrometre) was primarily responsible for the biological component of hydrogen peroxide decay.

 

Sediment. Data waiving (study scientifically not necessary): The reaction mass of calcium dihydroxide and calcium peroxide is an inorganic multi-constituent substance that will not persist in the environment. Abiotic processes such as hydrolysis and dissociation are responsible for the fate of this multi-constituent substance in the environment. The constituent calcium peroxide is hydrolyzed to calcium hydroxide and hydrogen peroxide. The alkaline constituent calcium hydroxide will be neutralized in the environment, while hydrogen peroxide will be degraded by abiotic and biotic processes to oxygen and water.

Additional information

According to the EU risk assessment report for hydrogen peroxide (European Commission 2003) a number of simulation tests on biodegradation are available. Degradation in lake water (Jacks Lake, Ontario) during summer time was studied (Cooper and Lean 1989). The lake was characterised as oligotrophic with a pH value of 7.2, a Ca2+ concentration of 14 mg/L, a mean phosphorous content of 0.012 mg/L and a DOC of 6 mg/L. The initial concentration of hydrogen peroxide in the lake water was 0.003 mg/L. Dark decay of the substance followed first order kinetics and the following half-lives were observed: 7.8 hours for unfiltered water, 8.6 hours for filtered water (5 micrometre), 31 hours for filtered water (1 micrometre) and >24 hours for filtered water (0.45 micrometre). It appeared from the results that the fraction containing pico plankton contained also the major portion of the biological agent degrading hydrogen peroxide. Hydrogen peroxide degradation was also measured in Lake Ontario (Cooper et al. 1989). The half-lives ranged from 14.7 to 21.6 hours. No degradation of hydrogen peroxide over a period of 7 hours was observed when water was filtered through 0.45 micrometre membranes. The dark decay time of hydrogen peroxide was also measured in sea water at room temperature (Johnson et al. 1989). The initial concentration of hydrogen peroxide was between 3 and 5 microgram/L. The degradation rate was 0.13 microgram/L/hour and hydrogen peroxide disappeared after 23 to 39 hours.