4-(1,1,3,3-tetramethylbutyl)phenol

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study similar to EPA Guideline 835.3180 (Degradation in marine sediments) and OECD 309 (Aerobic Degradation in Seawater) without detailed documentation.

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.3180 (Sediment / Water Microcosm Biodegradation Test)

Deviations:

yes

Remarks:

tests were also conducted under anaerobic conditions; aerobic samples were shaken 1 min prior to sampling; incubation under static conditions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Deviations:

yes

Remarks:

no agitation of flasks; samples were incubated with and without aeration in Erlenmeyer flasks

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Molecular weight: 206.0
- Water solubility (mg/L at 20 °C): 12.6
- log Kow: 4.12

Radiolabelling:

no

Oxygen conditions:

aerobic/anaerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): coastal area around Adelaide, Australia; seawater was collected from a jetty St. Kilda beach
- Storage conditions: refrigerator at 4 °C before use
- pH at time of collection: 8.4
- TC: 29 mg/l
- IC: 28 mg/l
- OC: 1 mg/l
- Ammonium-N: 1.7 mg/l
- Nitrate-N: 0.2 mg/l
- Phosphate-P: 0.1 mg/l
- Sulfate: 3100 mg/l

Details on source and properties of sediment:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): coastal area around Adelaide, Australia; sediment was taken from St. Kilda beach
- Storage conditions: refrigerator at 4 °C before use
- Water content of wet sediment: 15 %
- Textural classification (i.e. %sand/silt/clay): 22.1/0.8/3
- pH at time of collection: 9.5
- Organic carbon (%): 0.1
- Total carbon (%): 8.8
- CEC(NH4) (cmol(+)/kg): 2.4
- CaCO3 (%): 72
- Clay (%): 3
- Silt (%): 0.8
- Sand (%): 22.1

Details on inoculum:

No details reported

Duration of test (contact time):

>= 56 - <= 70 d

Initial conc.:

5 µg/L

Based on:

test mat.

Initial conc.:

1 other: µg/g sediment

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment:
* Seawater: 2 L sample in 2.5 L Winchester bottles; bottles (sterilized control and unsterilized sample) were spiked with 4-t-OP at a final
concentration of 5 µg/l
* Marine sediment: spiked with 4-t-OP at a final concentration of 1 µg/g sediment (5g of sediment + 5 ml of seawater)
- Composition of medium:
* Seawater: seawater only
* Marine sediment: 5g of sediment + 5 ml of seawater from Adelaide coast, South Australia, were used to make slurry during all experiments
- Additional substrate: no
- Test temperature:
* Seawater: 20 +/- 3 °C
* Marine sediment: 20 °C
- pH: 8.4 and 9.5 for seawater and sediment, respectively
- pH adjusted: no
- Continuous darkness: no data


TEST SYSTEM
- Culturing apparatus:
* Seawater: 2.5 L Winchester bottles covered with cotton wool bungs
* Marine sediment, aerobic conditions: 100 ml Schott bottles
* Marine sediment, anaerobic conditions: Hungate anaerobic culture tubes (16 x 125 mm)
- Number of culture flasks/experiment (and sampling time for marine sediments): 2
- Method used to create aerobic conditions:
* Seawater: aerated by bubbling air through the test bottles at a rate of approx. 1L/h
* Marine sediment: the small volume of the slurry media in the large bottles plus sufficient headspace ensured aerobic conditions
- Method used to create anaerobic conditions:
* Marine sediment: > Hungate anaerobic culture tubes were placed in an anaerobic incubation chamber filled with nitrogen gas
> The lids of the tubes were loosened to facilitate gas exchange
> Resazurin was added at a concentration of 0.0002 % into two tubes as a redox indicator (colour change from red to colourless)
> Sediment samples were spiked with the test substance after Resazurin turned colourless (after approx. 1 month) and tubes
were tightened after spiking ; incubation under same conditions as aerobic sediment samples


SAMPLING
- Sampling frequency:
* Seawater: Days 0, 1, 2, 4, 7, 13, 21, 28, 35, 42, 49, and 56
* Marine sediment: Days 0, 1, 3, and 7, and then weekly until 70 d
- Sampling method:
* Seawater: aliquots of 100 ml were taken at each sampling day
* Marine sediment (aerobic and anaerobic): two bottles/tubes from every treatment were sacrificed at each sampling day


CONTROL AND BLANK SYSTEM
- Abiotic sterile control:
* Seawater: sterilized by autoclaving 3 x within 3d
* Marine sediments: sterilized by autoclaving 3 x within 3d

Test performance:

No unusual observations during test or any other information affecting results

% Degr.:

ca. 99

Parameter:

test mat. analysis

Sampling time:

42 d

Remarks on result:

other: Aerobic degradation in seawater; seawater bubbled with air

% Degr.:

ca. 98

Parameter:

test mat. analysis

Sampling time:

49 d

Remarks on result:

other: Aerobic degradation in seawater without air bubbling

% Degr.:

ca. 98

Parameter:

test mat. analysis

Sampling time:

42 d

Remarks on result:

other: Aerobic degradation in marine sediment

% Degr.:

0

Parameter:

test mat. analysis

Sampling time:

70 d

Remarks on result:

other: Anaerobic degradation in marine sediment

Compartment:

water

DT50:

60 d

Type:

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

Remarks on result:

other: Aerobic degradation in seawater without air-bubbling

Compartment:

sediment

DT50:

> 20 d

Type:

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

Remarks on result:

other: aerobic conditions

Transformation products:

not measured

Details on transformation products:

Not applicable

Evaporation of parent compound:

yes

Volatile metabolites:

not measured

Residues:

yes

Details on results:

AEROBIC DEGRADATION IN SEAWATER:
- A significant loss was observed in the sterile seawater first 13 d for 4-t-OP.
- After this initial loss, the concentration in the sterile seawater remained stable with little change.
- A comparison of sterile and nonsterile treatments showed that following the initial abiotic loss, biodegradation was mainly responsible for the further loss in nonsterile seawater.
- After 42 days the concentration of 4-t-OP reached 0.03 µg/l.
- The experiment demonstrates that 4-t-OP can be degraded by aerobes in seawater once the microorganisms in the water became acclimated to the chemical.
- The rapid loss of 4-t-OP in seawater shortly following treatment was caused by abiotic processes such as volatilization (shaking and airing in the experiment) because there were parallel losses in the sterile and nonsterile seawater.
- Sorption on glassware may also account for some of the loss because 4-t-OP is highly hydrophobic and can adsorb onto solid phase.
- The rapid loss in the seawater is believed to be caused mainly by initial volatilization due to air bubbling and sorption on glassware and later biodegradation.
- This is also supported by further experiments on 4-t-OP which showed much smaller loss of 4-t-OP in sterile seawater without shaking or air bubbling.

Results with reference substance:

Not applicable

Validity criteria fulfilled:

not applicable

Conclusions:

This study demonstrates that 4-tert-Octylphenol is degraded under aerobic conditions in seawater and marine sediments, but seems to be persistent in marine sediments under anaerobic conditions.

Executive summary:

The degradation of 4-tert-Octylphenol was studied similar to the methods laid down in EPA Guideline OPPTS 835.3180 at initial concentrations of 5 µg/l and 1µg/g in seawater and marine sediments, respectively, for 56 (saltwater) and 70 days (marine sediments) at 20 °C under aerobic (> seawater and sediment) and anaerobic (> sediment only) conditions. The degradation of the test substance was followed by HPLC.

A significant loss was observed in seawater in the first 13 days for 4-tert-Octylphenol in the sterile control. After this initial loss, the concentration of in the sterile seawater remained stable with little change. A comparison of sterile and non-sterile treatments showed that following the initial abiotic loss due to volatilization and adsorption to glass surfaces of the incubation flasks, biodegradation was mainly responsible for the further loss in non-sterile seawater.

Aerobic degradation of 4-tert-Octylphenol in seawater and marine sediments was relatively slow with half-lives of 60 d and > 20 d, respectively, based on first-order reaction kinetics. Approximately 98 % of the test substance have been degraded in seawater under aerobic conditions within 49 days.

No degradation could be observed in marine sediments under anaerobic conditions after 70 days of incubation at 20 °C.

In summary, this study demonstrates that 4-tert-Octylphenol is degraded under aerobic conditions in seawater and marine sediments, but seems to be persistent in marine sediments under anaerobic conditions. Therefore, it can be concluded that 4-tert-Octylphenol is likely to be persistent and may accumulate in anoxic marine sediments.

Reference 2

Endpoint:

biodegradation in water and sediment: simulation tests

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Documentation insufficient for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Media:
Minimum mineral salts medium (MMO), prepared in sterile MilliQ water, was used to incubate the Sphingomonas sp. strain after addition of the desired amount of OP (4-(tert-octyl)phenol, 97%). Luria Bertani (LB) medium was used to culture the Sphingomonas sp. strain to obtain high cell densities, to enumerate culture densities and to assess the purity of the cultures. Fifteen g agar-agar per liter was added to make plates. A 10-fold dilution series of cultures was made (sterile physiological solution; 0.85% NaCl in MilliQ water), and 100 l of each dilution was surface plated on LB-agar for enumeration purposes. Liquid cultures and plates were incubated at 28 +/- 2 °C.

Determination of OP degradation and formation of intermediates:
Two series of Erlenmeyer flasks were simultaneously inoculated with 2 ml of a 12 days old Sphingomonas sp. culture. In the first series, 8 Erlenmeyer flasks in duplicate contained MMO-medium, OP and 2.6 g/l sodium acetate from the beginning of the incubation period. For the second series, the sodium acetate was added to the remaining 4 flasks (duplicate) on day 9 of the incubation period. Every 2 to 3 days, two flasks of each series were sacrificed. Both duplicates were sampled (1 ml) for bacterial growth determination (OD550). Afterwards, the entire content of one flask (including the plastic tip used to take the 1-ml sample) was used for extraction and OP analysis, and the second for further analysis of COD and degradation intermediates. The diethyl ether extracts were screened for degradation intermediates using GC-MS.

Removal of OP in resting cell culture:
Resting cells of the Sphingomonas sp. strain were cultured in LB-medium (rotary shaker at 40 to 50 rpm; 28 +/- 2 °C) for 1 week until a plateau in the OD610 was obtained. This culture was centrifuged three times (5 min at 5,000 x g), decanted and resuspended with MMO-medium. The culture (1.6 x 10^9 CFU/ml; 1.04 g VSS/l) was divided into 5 aliquots of 50 ml to which ~ 680 mg OP/L was added (100 ml Erlenmeyer flasks). At day 2, 4, 7 and 9 a flask was sacrificed for OD550 measurements and diethyl ether extraction for intermediates. At day 9 the fifth flask was used for OP analysis.

OP analysis:
OP was extracted from samples by an exhaustive steam distillation-extraction technique with cyclohexane. OP present in the collected extracts was determined by HPLC.

Extraction and determination of degradation products:
The culture medium was extracted using a mixture of 1 ml of 1/1 sulfuric acidwater (95 to 96%; VEL), ~0.8 g of NaCl (VEL), and 2 ml of diethyl ether (VEL). This mixture was vortexed for 15 min and centrifuged for 5 min at 3,000 g. About 1.5 ml of the diethyl ether layer was transferred to a test tube and dried with 0.5 g of anhydrous sodium sulfate (VEL). These diethyl ether extracts were analyzed with GC-MS to screen for degradation intermediates of OP.

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: bacterial culture of Sphingomonas sp.

Duration of test (contact time):

19 d

Initial conc.:

ca. 680 mg/L

Based on:

test mat.

% Degr.:

94

Parameter:

test mat. analysis

Sampling time:

19 d

Remarks on result:

other: first test series with sodium acetate added at the beginning of the incubation period

% Degr.:

99.5

Parameter:

test mat. analysis

Sampling time:

19 d

Remarks on result:

other: Addition of sodium acetate at day 9 of incubation

% Degr.:

ca. 64

Parameter:

test mat. analysis

Sampling time:

9 d

Remarks on result:

other: degradation in resting cell cultures; same range as for the other experiments

Transformation products:

yes

No.:

#1

Validity criteria fulfilled:

not applicable

Conclusions:

OP could be degraded by a culture of a Sphingomonas sp. The results suggest that oxidized branched alkyl chains are rather resistant to biodegradation although further metabolism might be plausible as indicated by the CODs, OP and degradation intermediate measurements.

Executive summary:

Degradation of branched octylphenol was studied in a bacterial culture of a Sphingomonas sp. strain. The aerobic microbiological transformation of octylphenol was examined with and without the addition of the easily assimilable sodium acetate.

Octylphenol was degraded to 94.5 % and 99 % with and without the addition of sodium acetate, respectively. In both cases the formation of the metabolite 2,4,4-trimethyl-2-pentanol, representing the intact alkyl chain as a tertiary alcohol, was observed. Since the octylphenol degradation rate was not affected by the presence of acetate, this strain did not show any diauxic metabolic behaviour when incubated with octylphenol and sodium acetate as the sources of carbon and energy.

Reference 3

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: Similar to EPA Guideline OPPTS 835.5154 and OECD 309 without detailed documentation.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Deviations:

yes

Remarks:

Tests were conducted without sediment added to the river water samples; only one concentration was tested; no reference substance

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.5154 (Anaerobic Biodegradability in the Subsurface)

Version / remarks:

experiments with bed sediments

Deviations:

yes

Remarks:

sampling of bed sediments and storage not under anaerobic conditions; slurry: 10 g sediment (dry weight) and 20 ml non-sterile river water; no simulation of sulfate reducing conditions

GLP compliance:

no

Radiolabelling:

yes

Oxygen conditions:

aerobic/anaerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

- Details on collection: * Sampling sites:
> Aire River near Shipley (national grid reference (NGR) SE138 379)
> Fleet Weir (NGR SE379 288)
> Calder River at Brighthouse (NGR SE155222)
> Methley Bridge (NGR SE405 207)
> Thames River near Wallingford (NGR SU 614 903) and at Sonning (NGR SU755 758)
* 2 - 5 cm below surface in 1 L polypropylene flasks
* Distance to river banks: approx. 2 m
- Pretreatment: 0.45 µm filtration
- Storage conditions: not reported
- Storage length: not reported
- Temperature (°C) at time of collection: not reported
- pH at time of collection: see table 1
- Electrical conductivity: measured but results only reported for Calder River (see table 2)
- Dissolved organic carbon (%): see table 1
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): see table 1
- Water filtered: yes (for DOC analyses only)
- Type and size of filter used, if any: 0.45 µm

Details on source and properties of sediment:

- Details on collection: * Sampling sites:
> Aire River near Shipley (national grid reference (NGR) SE138 379)
> Calder River at Brighthouse (NGR SE155222)
> Thames River near Wallingford (NGR SU 614 903) and at Sonning (NGR SU755 758)
* Sampling: skimming off top 2 - 5 cm of bed material with wide-neck 1L flasks
* Distance to river banks: approx. 2 m
- Storage conditions: sediment saturated with river water at 4 °C
- Storage length: up to 5 days; excess river water was then removed, leaving a sediment-water slurry

Details on inoculum:

No details reported

Duration of test (contact time):

>= 24 - <= 83 d

Initial conc.:

100 other: µg/l river water

Based on:

test mat.

Initial conc.:

600 other: µg/kg sediment

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: * River water: 30 ml
* Bed sediment: 10 g dry weight + 20 ml nonsterile river water
- Composition of medium: not applicable
- Additional substrate: not applicable
- Test temperature: 20 °C
- pH: see tables 1 and 2
- pH adjusted: no
- Continuous darkness: no data
- Other: * Bed sediment samples: the tubes containing bed sediment and OP were placed on an orbital shaker and shaken for 1 h to mix the
chemical evenly into the bed sediment

TEST SYSTEM
- Culturing apparatus: * River water experiments: 125 ml polytetraflouroethylene (PTFE) conical flasks
* Bed sediments: PTFE centrifuge tubes
- Number of culture flasks/treatment: triplicate
- Method used to create aerobic conditions: no data
- Method used to create anaerobic conditions (bed sediments only):
* The tubes (with loose tops) were placed in in 2.5 L anaerobic jars (Merck, Darmstadt, Germany) with AnaeroGen (Oxord, Basingstroke,
Hants, UK) packs to remove the oxygen
* Anaerotest strips to confirm anoxic conditions


SAMPLING
- Sampling frequency: * River water experiments: weekly intervals
* Bed sediments: 0, 28, 50, and 83 day
- Sampling method: * River water experiments:
> Drawning 1 ml of methanol in a 2-ml plastic syringe with hypodermic needle before withdrawing a
further 1 ml of sample from from the conical flask into the syringe
> The syringe was then inverted to mix thoroughly the methanol and aqueous sample before discharging into a second
open syringe, which was connected to a 0.45 µm PTFE filter (Gelman, Gelman Sciences, Ann Arbor, MI, USA)
> The sample was then filtered into a glass HPLC vial, which was capped with a PTFE-lined rubber septa
* Bed sediments:
> Tubes to be sacrificed were removed from the anaerobic jars and centrifuged for 20 min at 4,749 g
> Tubes were weighed before removing by Pasteur pipette as much of the aqueous phase as possible (assumption: 1g = 1 ml)
> Equivalent volume of methanol was added to the tubes
- Sample storage before analysis: * River water: > PTFE capped HPLC vials at 4 °C for one week


CONTROL AND BLANK SYSTEM
- Abiotic sterile control: * River water experiments: samples autoclaved for 30 min.
* Bed sediments (Aire, Calder, or Thames; single tubes): autoclaved twice (for 30 min)

Test performance:

No unusual observations during test or any other information affecting results

% Degr.:

0

Parameter:

test mat. analysis

Sampling time:

83 d

Remarks on result:

other: anaerobic bed sediment samples

Compartment:

water

DT50:

>= 13 - <= 23 d

Type:

zero order

Remarks on result:

other: samples taken from the Aire, Calder, and Thames river

Compartment:

water

DT50:

>= 8 - <= 13 d

Type:

zero order

Remarks on result:

other: Calder River: more urban and rural reaches

Compartment:

water

DT50:

>= 8 - <= 50 d

Type:

zero order

Remarks on result:

other: overall range for all river water samples

Transformation products:

not measured

Details on transformation products:

Not applicable

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

yes

Details on results:

INFLUENCE OF METHANOLIC SOLUTION OF OP ON DEGRADATION RATE
No significant differences in Thames River water samples with no methanol and those with 0.4 and 0.04 % methanol
=> The presence of small quantities of methanol did not affect the rate at which OP was degraded by the river microorganisms


INFLUENCE OF FLASK AGITATION ON BIODEGRADATION RATES IN MICROCOSMS
- Original water sample: 2.1 x 105 cfu/ml culturable organisms (SD 2 x 104)
- After static incubation over 21 d with 100 µg/l: 4.2 x 106 cfu/ml culturable organisms (SD 2 x 106)
- After incubation over 21 d with 100 µg/l with agitation: 5.9 x 106 cfu/ml culturable organisms (SD 4 x 106)
- However, colony diversity decreased over the 21 d incubation period
=> No significant difference of shaking over static incubation with degradation rate of OP



COMPARISON OF BIODEGRADATION POTENTIALS BETWEEN THE RIVERS
- Conditions in the experiments (100µg/l OP, 20 °C) mimic the conditions of high alkylphenol contamination in summer
- Very slight decline in concentration was observed in the sterile control flasks, possibly linked to sorption to suspended sediments
- OP was biodegraded in all the river water samples taken from the Aire, Calder and Thames rivers, with estimated half-lives ranging from 13-23 d (calculated on zero-order reaction; in the majority of the cases this gave the best fit; however, in some cases a better fit was achieved using a first-order reaction (see table 1))
- All of the water samples spiked with OP showed an almost 10-fold increase in number of culturable organisms; the counts of the original water samples to which OP had not been added had remained the same or declined slightly after 35 d at 20 °C
- Half-life for OP could not be predicted on the basis of number of viable bacteria present (r² of 0.07 for Thames River and 0.045 for Calder River samples) or the quantity of DOC present (r² of 0.59 for Thames River and 0.31 for Calder River samples)


COMPARISON OF BIODEGRADATION POTENTIAL ALONG THE SAME RIVER (CALDER RIVER)
- The furthest upstream sample was taken from Cragg Brook: free from either industrial or domestic sewage; higher DOC content is likely to reflect a humic acid content from the local moors; 10 times less bacteria compared with the other downstream sampling points
- Sowerby Bridge, Brighouse, and Methley Bridge: sampling points successively downstream of Cragg Brook where the Calder River receives successive inputs of sewage and industrial effluents (increase of conductivity along the river; see table 2)
- Most rapid degradation of OP was observed with the samples from Sowerby Bridge and Brighouse (half-lives of 8 d), followed by Methley Bridge (half-life of 13 d); in contrast, the sample from the upland stream of Cragg Brook showed little potential to degrade OP over the 26-d incubation period


THE INFLUENCE OF OP CONCENTRATION ON BIODEGRADATION RATE
- Little difference in degradation rates between 20, 50, 75, and 100 µg/l
- Half-lives: 12 to 18 d (calculated on basis if first-order reaction)
- Concentration of 0.5 µg/l: neither zero-order nor first-order reaction kinetics gave a very good fit, but OP is clearly not more persistent at low concentrations


MINERALIZATION OF THE PHENYL GROUP OF OP
- Over a 56 d incubation period 25 % of the 14C-labeled OP phenyl group was mineralized in Calder River samples
- However, there was little evidence of mineralization by the Aire and Thames river samples

Results with reference substance:

Not applicable

Table 1: Summary of river characteristics and estimated hal-lives as zero-order (ZO) or first-order (FO) with 95 % confidence limits for river samples from the Thames River at Wallingford (W), Sonning (S), the Aire River at Fleet Weir (F), Shipley (S), and the Calder River at Methley Bridge (M), Sowerby Bridge (Sb), and Brighouse (B); all based onicubations at 20 °C and spiked with 100 µg/l

Sample	Date	pH	DOC [mg/l]	Count [cfu/ml]	Half-life as ZO [d]	Half-life as FO [d]
Thames (W)	03/03/1996	8.2	ND	2.2 x 10^4	22.0 (11.6)	NA
Thames (W)	05/06/1996	7.9	ND	1.5 x 10^4	18.4 (6.3)	11.0 (3.1)
Thames (W)	15/01/1997	8.1	3.5	1.5 x 10^5	54.0 (24.0)	20.0 (8.0)
Thames (W)	03/06/1998	8.2	3.2	3.2 x 10^4	26.0 (8.9)	18.0 (7.2)
Thames (W)	13/11/1988	8.1	6.1	2.0 x 10^5	11.0 (2.0)	NA
Thames (W)	08/02/1999	7.9	3.6	3.3 x 10^4	21.1 (6.5)	NA
Thames (S)	08/02/1999	8.0	3.1	5.3 x 10^4	15.0 (1.0)	NA
Aire (F)	18/12/1996	7.3	5.6	2.3 x 10^5	71.2 (17.3)	51 (20.2)
Aire (F)	08/02/1999	7.9	5.5	4.0 x 10^5	16.0 (4.5)	NA
Aire (S)	08/02/1999	8.0	3.8	2.1 x 10^5	23.0 (4.0)	NA
Calder (M)	10/12/1996	7.5	6.8	3.5 x 10^4	9.0 (40)	NA
Calder (M)	27/11/1997	7.5	8.1	4.8 x 10^5	13.0 (2.0)	NA
Calder (M)	08/02/1999	7.4	7.4	6.5 x 10^5	19.0 (3.0)	NA
Calder (Sb)	27/11/1997	7.1	4.6	4.1 x 10^5	8.0 (3.3)	NA
Calder (B)	27/11/1997	7.2	5.9	5.1 x 10^4	8.0 (1.5)	NA
Calder (B)	08/02/1999	7.6	4.3	8.3 x 10^4	13.5 (4.5)	8.1 (1.9)
Cragg Brook	27/12/1997	6.7	8.9	1.2 x 10^4	36 (28.0)	NA

 

Table 2: Characteristics of water samples from the Calder River, England, 27/11/1997

Location	pH	DOC	Viable Count [cfu/ml]	Conductivity [µS/cm]
Cragg Brook	6.7	8.9	1.2 x 10^4	159
Sowerby Bridge	7.1	4.6	4.1 x 10^5	232
Brighouse	7.2	5.9	5.1 x 10^5	337
Methley Bridge	7.5	8.1	5.8 x 10^5	763

 

Validity criteria fulfilled:

not applicable

Conclusions:

The results of this study demonstrate that OP could be degraded in river water samples taken from a range of urban and rural reaches with the possible exception being a sample taken from an upland stream. OP degradation rates, calculated as half-lives, varied between different rivers sampled on the same day. Variation was also observed where one river reach was sampled at different times, such as the Thames at Wallingford, where half-lives of 11 to 54 days were recorded. In the Aire and Thames rivers, degradation is likely to be incomplete, leaving by-products containing the phenyl ring. Mineralization of the phenyl group was only observed in the Calder River water sample. The OP biodegradation process will take place throughout the range of concentrations likely to be encountered. OP sorption to suspended and bed sediments will be an important mechanism for removal of OP from the water column (see Johnson (1998), IUCLID section 5.4.1); however, where these sediments are anaerobic, OP is likely to persist and hence accumulate.

Executive summary:

To study octylphenol biodegradation, samples of river water and sediments were taken from the Aire and Calder rivers in the United Kingdom, running through urban/industrial areas, as well as the Thames River running through a more rural area. Using laboratory microcosms (incuabtion of 100 µg/l OP spiked samples at 20 °C), half-lives of 8 to 50 d were obtained for the water samples, with most curves fitting a zero-order reaction.

The Calder River was sampled at four separate points along a 45-km length, encompassing rural to increasingly urban/industrial reaches. Little degradation was observed in the sample from the upland/rural reach, while half-lives of 8 to 13 d were seen in the more urban/industrial reaches.

Mineralization of the phenyl ring, detected by evolution of ¹⁴CO₂ from ring-labeled octylphenol, was only observed in water from the Calder River sample.

Degradation rate was similar for a range of concentrations from 0.3 to 100 µg/l when tested with river water from the Thames River.

No degradation was observed over 83 d when bed sediments were spiked with octylphenol and incubated under anaerobic conditions.

Description of key information

Johnson et al. (2000) studied octylphenol biodegradation in river water and sediments samples taken from the Aire and Calder rivers in the United Kingdom, running through urban/industrial areas, as well as the Thames River running through a more rural area using laboratory microcosms (incubation of 100 µg/l and 600 µ/kg OP spiked river water samples and sediment samples, respectively, at 20 °C). The degradation of the test substance was followed by HPLC (river water samples) and GC (bed sediments). Methods used were similar to OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test) and EPA OPPTS 835.5154 (Anaerobic Biodegradability in the Subsurface).
In addition, Ying and Kookana (2003) studied the degradation of 4-tert-Octylphenol similar to the methods laid down in EPA Guideline OPPTS 835.3180 at initial concentrations of 5 µg/l and 1µg/g in seawater and marine sediments, respectively, for 56 (saltwater) and 70 days (marine sediments) at 20 °C under aerobic (-> seawater and sediment) and anaerobic (-> sediment only) conditions. The degradation of the test substance was followed by HPLC. 
Besides, Tanghe et al. (2000) measured the aerobic biodegradation of branched octylphenol and the formation of degradation products formed by a Sphingomonas sp. strain isolated from activated sludge with and without the addition of an easily assimilable carbon source (sodium acetate). Octylphenol degradation and the formation of intermediates was determined in minimum mineral salts medium (MMO) as well as in resting cell cultures. The removal of octylphenol was monitored using HPLC, the formation of degradation products was followed by means of GC-MS. 

Additional information

In the laboratory microcosms Johnson et al. (2000) obtained half-lives of 8 to 50 d for the river water samples, with most curves fitting a zero-order reaction. Shorter half-lives were generally seen in more urban and industrialised rather than upland and rural areas, which suggests that some form of acclimation may occur. However, even then, half-lives varied within the river for samples of river water taken at different times, although a similar degradation rate was noted for a range of concentrations from 0.3 to 100 µg/L.

Consequently this work demonstrates that 4-tert-Octylphenol could be degraded in river samples taken from a range of urban and rural reaches (with the possible exception being a sample taken from an upland stream). No degradation was observed over 83 days when bed sediments were spiked with 4-tert-Octylphenol and incubated under anaerobic conditions.

 

Ying and Kookana (2003) observed a significant loss in seawater samples in the first 13 days for 4-tert-Octylphenol in the sterile control. After this initial loss, the concentration of 4 -tert-Octylphenol in the sterile seawater remained stable with little change. A comparison of sterile and non-sterile treatments showed that following the initial abiotic loss due to volatilization and adsorption to glass surfaces of the incubation flasks, biodegradation was mainly responsible for the further loss in non-sterile seawater.

Aerobic degradation of 4-tert-Octylphenol in seawater and marine sediments was relatively slow with half-lives of 60 d and > 20 d, respectively, based on first-order reaction kinetics. Approximately 98 % of the test substance has been degraded in seawater under aerobic conditions within 49 days.

 

No degradation could be observed in marine sediments under anaerobic conditions after 70 days of incubation at 20 °C.

 

In summary, this study demonstrates that 4-tert-Octylphenol is degraded under aerobic conditions in seawater and marine sediments, but seems to be persistent in marine sediments under anaerobic conditions. Therefore, it can be concluded that 4-tert-Octylphenol is likely to be persistent and may accumulate in anoxic marine sediments.

 

 

From the studies conducted by Johnson et al. (2000) and Ying & Kookana (2003) it can be concluded that 4-tert-Octylphenol can be aerobically degraded in freshwater, marine water, and marine sediments. No degradation was observed in freshwater bed sediments and marine sediments under anaerobic conditions.

Tanghe et al. (2000) observed 94.5 % and 99 % degradation of octylphenol with and without the addition of sodium acetate, respectively. In both cases the formation of the metabolite 2,4,4-trimethyl-2-pentanol, representing the intact alkyl chain as a tertiary alcohol, was observed. Since the octylphenol degradation rate was not affected by the presence of acetate, this strain did not show any diauxic metabolic behaviour when incubated with octylphenol and sodium acetate as the sources of carbon and energy.

The formation of 2,2,4-trimethyl-2-pentanol as the most prominent intermediate detected in the Sphingomonas sp. culture in all test series implies that the alkyl side chain may remain intact as a tertiary alcohol after fission of the aromatic ring of the parent compound (octylphenol).