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Biodegradation in soil

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Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Principles of method if other than guideline:
Static soil microcosm incubation test according to the general principles of OECD guideline 307: based on measurement of residual unaltered compounds, no mineralisation test.
GLP compliance:
no
Test type:
laboratory
Specific details on test material used for the study:
14 PAH were tested in this study ranging from naphthalene to indeno[1,2,3-cd]pyrene (two- to six-ring PAH). Eight compounds among them are relevant as constituents of pitch, coal tar, high-temp (CTPht). These are covered in this study record.

The following polycyclic aromatic compounds are relevant constituent of CTPht. They were purchased from Aldrich Chemical Co. Inc., Milwaukee, WI, USA or from The Foxboro Co., North Haven, CT, USA (benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene).

Initial soil concentrations [mg/kg]
Compound CAS no. Kidman loam McLaurin soil
(No. #1) (No. #2)
========================================================================
Phenanthrene 85-01-8 902 893
Fluoranthene 206-44-0 883 913
Pyrene 129-00-0 686 697
Chrysene 218-01-9 100 105
Benz[a]anthracene 56-55-3 107 99
Benzo[b]fluoranthene 205-99-2 39 37
Benzo[a]pyrene 50-32-8 33 33
Indeno[1,2,3-cd]pyrene 193-39-5 8 9
========================================================================

Note: Other 2- to 6-ring PAHs were also examined, but are not shown here, as they are not relevant for pitch, coa tar, high-temp. These substances are naphthalene, 1-methylnaphthalene, anthracene, 7,12-dimethylbenzanthracene, dibenz[a,h]anthracene, and dibenzo[a,i]pyrene.
Radiolabelling:
no
Oxygen conditions:
aerobic
Soil classification:
not specified
Year:
1990
Soil no.:
#1
Soil type:
sandy loam
% Org. C:
0.5
pH:
7.9
CEC:
10.1 meq/100 g soil d.w.
Soil no.:
#2
Soil type:
sandy loam
% Org. C:
1.1
pH:
4.8
CEC:
4.4 meq/100 g soil d.w.
Details on soil characteristics:
SOIL TYPES:
Two types of non-acclimated soil were used:
No. #1: Kidman sandy loam (Calciaquoll/Utah) and
No. #2: McLaurin sandy loam (Paleudult/Mississippi)
Soil of the top 15-cm zone was used.

SOIL PROPERTIES of top 15-cm zone:
- #1: Kidman sandy loam (Calciaquoll/Utah)
Microbial colonisation: 6.7 x 10E6 bacterial CF/g soil; 1.9 x 10E4 fungal CF/g soil (CF = colony forming units)
Electrical conductivity (EC): 0.2 dS/m
Moisture: 16.3 %
- #2: McLaurin sandy loam (Paleudult/Mississippi)
Microbial colonisation: 1.1 x 10E5 bacterial CF/g soil; 5.3 x 10E4 fungal CF/g soil (CF = colony forming units)
Electrical conductivity (EC): 0.09 dS/m
Moisture: 12.4 %
- Pesticide use history at the collection sites: no data
- Collection procedures: no data
- Sampling depth (cm): Soil of the top 15-cm zone was used.
- Storage conditions: no data
- Storage length: no data
- Soil preparation: Air dried, 2 mm sieved

(CF = colony forming units)
Soil No.:
#1
Duration:
196 d
Soil No.:
#2
Duration:
105 d
Soil No.:
#1
Initial conc.:
902 mg/kg soil d.w.
Based on:
test mat.
Remarks:
phenanthrene
Soil No.:
#1
Initial conc.:
883 mg/kg soil d.w.
Based on:
test mat.
Remarks:
fluoranthene
Soil No.:
#1
Initial conc.:
686 mg/kg soil d.w.
Based on:
test mat.
Remarks:
pyrene
Soil No.:
#1
Initial conc.:
100 mg/kg soil d.w.
Based on:
test mat.
Remarks:
chrysene
Soil No.:
#1
Initial conc.:
107 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benz[a]anthracene
Soil No.:
#1
Initial conc.:
39 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benzo[b]fluoranthene
Soil No.:
#1
Initial conc.:
33 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benzo[a]pyrene
Soil No.:
#1
Initial conc.:
8 mg/kg soil d.w.
Based on:
test mat.
Remarks:
indeno[1,2,3-cd]pyrene
Soil No.:
#2
Initial conc.:
893 mg/kg soil d.w.
Based on:
test mat.
Remarks:
phenanthrene
Soil No.:
#2
Initial conc.:
913 mg/kg soil d.w.
Based on:
test mat.
Remarks:
fluoranthene
Soil No.:
#2
Initial conc.:
697 mg/kg soil d.w.
Based on:
test mat.
Remarks:
pyrene
Soil No.:
#2
Initial conc.:
105 mg/kg soil d.w.
Based on:
test mat.
Remarks:
chrysene
Soil No.:
#2
Initial conc.:
99 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benz[a]anthracene
Soil No.:
#2
Initial conc.:
37 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benzo[b]fluoranthene
Soil No.:
#2
Initial conc.:
33 mg/kg soil d.w.
Based on:
test mat.
Remarks:
benzo[a]pyrene
Soil No.:
#2
Initial conc.:
9 mg/kg soil d.w.
Based on:
test mat.
Remarks:
indeno[1,2,3-cd]pyrene
Parameter followed for biodegradation estimation:
test mat. analysis
Soil No.:
#1
Temp.:
20 °C
Humidity:
>= 60 % of water holding capacity
Microbial biomass:
soil plate counts: bacteria 6.7E6 / fungi 1.9E4 cfu/g soil
Soil No.:
#2
Temp.:
20 °C
Humidity:
>= 60 % of water holding capacity
Microbial biomass:
soil plate counts: bacteria 1.1E5 / fungi 5.3E4 cfu/g soil
Details on experimental conditions:
STATIC SOIL INCUBATION TEST

EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): one week, temperature not specified
- Soil condition: dry, non-acclimated
- Soil (g/replicate): 40
- No. of replication controls: 1 (abiotic controls - reactors treated with 2% solution of mercuric chloride)
- No. of replication treatments: 3
- Test apparatus (Type/material/volume): 500 mL glass beakers
- If no traps were used, is the system closed/open: beakers were covered with polyethylene film

Test material application
- Application method (e.g. applied on surface, homogeneous mixing etc.): test materials dissolved in dichloromethane were mixed with the soil
- Is the co-solvent evaporated: yes, for 24 h
- Soil conditions: after evaporation of the solvent, water was added to adjust soil moisture to -33 J/kg matric potential (>= 60 % water holding capacity)

Experimental conditions
- Incubation temperature: 20 °C
- Moisture maintenance method: periodic addition of water
- Continuous darkness: Yes

OXYGEN CONDITIONS (delete elements as appropriate)
- Method used to create the aerobic conditions: the polyethylene film covers of the test vessels (beakers) are permeable to oxygen

SAMPLING DETAILS
- Sampling scedule: soil # 1: 0, 42, 84, 140, and 196 d
soil # 2: 0, 25, 70, and 105 d
both soils: 0, 14, 28, and 56 d (phenanthrene and 7,12-dimethylbenzanthracene)
- Sampling method for soil samples: complete test vessels were used for analysis
- Method of collection of CO2 and volatile organic compounds: not measured (release of volatiles was determined in a pretest over 48 h)
Key result
Soil No.:
#1
DT50:
16 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material phenanthrene; 95% CI: 13-18 d
Key result
Soil No.:
#1
DT50:
377 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material fluoranthene: 95% CI: 277-578 d
Key result
Soil No.:
#1
DT50:
260 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material pyrene; 95% CI: 193-408
Key result
Soil No.:
#1
DT50:
371 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material chrysene; 95% CI: 289-533 d
Key result
Soil No.:
#1
DT50:
261 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benz[a]anthracene; 95% CI: 210-347 d
Key result
Soil No.:
#1
DT50:
294 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[b]fluoranthene; 95% CI: 231-385 d
Key result
Soil No.:
#1
DT50:
309 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[a]pyrene; 95% CI: 239-462 d
Key result
Soil No.:
#1
DT50:
288 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material indeno[1,2,3-cd]pyrene; 95% CI: 224-408 d
Key result
Soil No.:
#2
DT50:
35 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material phenanthrene; 95% CI: 27-53 d
Key result
Soil No.:
#2
DT50:
268 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material fluoranthene; 95% CI: 173-630
Key result
Soil No.:
#2
DT50:
199 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material pyrene; 95% CI: 131-408 d
Key result
Soil No.:
#2
DT50:
387 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material chrysene; 95% CI: 257-866 d
Key result
Soil No.:
#2
DT50:
162 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benz[a]anthracene; 95% CI: 131-217 d
Key result
Soil No.:
#2
DT50:
211 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[b]fluoranthene; 95% CI: 169-277 d
Key result
Soil No.:
#2
DT50:
229 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[a]pyrene; 95% CI: 178-315
Key result
Soil No.:
#2
DT50:
289 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material indeno[1,2,3-cd]pyrene; 95% CI: 224-408
Transformation products:
not measured
Evaporation of parent compound:
no
Volatile metabolites:
not measured
Residues:
yes
Remarks:
residual test materials

Abiotic removal was measured in separate tests prior to the determination of biodegradation.

 

 

Abiotic removal [%]

 

Kilman sandy loam

(soil #1)

McLaurin sandy loam

(soil #2)

Phenanthrene

17.4*

14.2*

Fluoranthene

0

3.1

Pyrene

4.4

3.2

Chrysene

5.9

3.2

Benz[a]anthracene

2.5

1.6

Benzo[b]fluoranthene

8.0

8.4

Benzo[a]pyrene

7.3

8.3

Indeno[1,2,3 -cd]pyrene

13.5

11.5

 

Statistical analysis indicated that abiotic degradation was significant only for 2- and 3-ring compounds (labelled by an asterisk).

The losses were statistically insignificant for those PAH that contained greater than 3 rings (no label).

 

 

Half-lives of biodegradation
[days (95% CI)]

 

Kilman sandy loam

(soil #1)

McLaurin sandy loam

(soil #2)

Phenanthrene

16 (13-18)

35 (27-53)

Fluoranthene

377 (277-578)

268 (173-630)

Pyrene

260 (193-408)

199 (131-408)

Chrysene

371 (289-533)

387 (257-866)

Benz[a]anthracene

261 (210-347)

162 (131-217)

Benzo[b]fluoranthene

294 (231-385)

211 (169-277)

Benzo[a]pyrene

309 (239-462)

229 (178-315)

Indeno[1,2,3 -cd]pyrene

288 (224-408)

289 (224-408)

 

The estimated amount biologically degraded was

= mass added - (volatilised mass + abiotic loss of mass + mass of soil residue).

 

The measured biological degradation rates of PAHs were not statistically different between the two soils studied. The kinetic calculations resulting in first order rate constants and half-lives gave r² values ranging from 0.71 - 0.95 and 0.57 - 0.93 for the Kidman and McLaurin soils, respectively.

Conclusions:
In a study similar to OECD TG 307 (Aerobic and Anaerobic Transformation in Soil), the aerobic degradation rate constants and resulting half-lives of 14 PAH were investigated in two different soils. Results can be considered to be acceptable estimates for two- to three-ringed PAHs. For the four- and five-ring PAHs, the half-lives estimated were longer than the study duration, which indicates that these values are quite uncertain (confirmed by large 95% confidence intervals for many of these PAHs). Due to the nature of these recalcitrant PAHs, the values presented must be considered to be best available estimates.
Eight of the PAH in this study (phenanthrene, fluoranthene, pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene, benzo[a]pyrene, and indeno[1,2,3-cd]pyrene) are relevant constituents of pitch, coal tar, high-temp. Half-lives determined range from 16 / 35 days (phenanthrene) to 371 / 387 days (chrysene) (soil #1 / #2, respectively).
Endpoint:
biodegradation in soil: simulation testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source test materials are individual polycyclic aromatic hydrocarbons ranging from two- to six-ring PAH. Depending on size/molecular weight and state of condensation, physico-chemical and environmental properties can be different. The target substance pitch, coal tar, high-temp. is composed of a broad range of PAH differing in size and degree of condensation.
The ability of CTPht to biodegrade in soil will be determined by the range of PAH that constitute its composition. Several of the source substances are major constituents of CTPht. Therefore, results obtained from biodegradation studies in soil with these compounds can be used in order to characterise the soil biodegradation potential of CTPht.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemicals are individual PAH. These include major constituents of CTPht. The specific analytical purity of individual chemicals is not reported in the publication. But they are obtained from commercial sources (Aldrich Chemical Co. Inc., Milwaukee, WI and The Foxboro Co. North Haven, CT), and they are considered to be of adequate purity for the purpose of the study. Tests have been performed with individual PAH and the test results reported relate to the individual test substances.
The target material pitch, coal tar, high-temp. (CTPht) is a UVCB substance. It is the product (residue) of the oxygen free high-temperature distillation of coal tar and consists of a complex mixture of polycyclic aromatic hydrocarbons, predominantly of highly condensed aromatic ring systems forming an inert matrix. In this matrix, individual PAH with a lower degree of condensation are included. This fraction is small (only ca. 20 % of the substance will evaporate at a distillation temperature up to 500 °C) and comprises polycyclic aromatic hydrocarbons with predominantly four and five, up to six annulated rings. Concentration is between ca. 0.02 and ca. 1.1 % (maximum 1.5 %). Water solubility of the substance is very low (ca. 0.24 mg dissolved C/L at a loading of 1000 mg substance/L or 1.3 µg/L sum of EPA PAH at a loading of 100 mg substance/L). Obviously, individual PAH will dissolved only at concentrations below their maximum water solubility.

3. ANALOGUE APPROACH JUSTIFICATION
Properties of the target substance CTPht regarding behaviour and fate in the environment will be determined by the properties of the PAH that are constituents of CTPht. Under environmental conditions or during processing of the target substance, environmentally available (volatile or water soluble) components of CTPht can be released. These will be predominantly four- to six-ring PAH (see above). They will be distributed in the environment and may also undergo biodegradation in soil.
Eight of these PAH (one three-ring, four four-ring and three five- and six-ring PAH) are included within the set of source substances. Biodegradation properties of these PAH in soil considered together will be specific for the environmental behaviour of CTPht. Therefore, it is justified to use date determined for individual PAH that are constituents of CTPht to characterise the environmental behaviour (biodegradation in soil) of pitch, coal tar, high-temp. (CTPht) itself.
Reason / purpose for cross-reference:
read-across source
Principles of method if other than guideline:
Read-across to preceding entry:
Source test material: polycyclic aromatic hydrocarbons (PAH), generic mixture;
Reference: Park et al. 1990
Key result
Soil No.:
#1
DT50:
16 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material phenanthrene; 95% CI: 13-18 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
377 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material fluoranthene: 95% CI: 277-578 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
260 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material pyrene; 95% CI: 193-408
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
371 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material chrysene; 95% CI: 289-533 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
261 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benz[a]anthracene; 95% CI: 210-347 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
294 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[b]fluoranthene; 95% CI: 231-385 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
309 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[a]pyrene; 95% CI: 239-462 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#1
DT50:
288 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material indeno[1,2,3-cd]pyrene; 95% CI: 224-408 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
35 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material phenanthrene; 95% CI: 27-53 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
268 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material fluoranthene; 95% CI: 173-630
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
199 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material pyrene; 95% CI: 131-408 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
387 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material chrysene; 95% CI: 257-866 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
162 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benz[a]anthracene; 95% CI: 131-217 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
211 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[b]fluoranthene; 95% CI: 169-277 d
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
229 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material benzo[a]pyrene; 95% CI: 178-315
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Key result
Soil No.:
#2
DT50:
289 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: test material indeno[1,2,3-cd]pyrene; 95% CI: 224-408
Remarks:
the test result of the source substance is adopted as weight of evidence for the target substance CTPht
Transformation products:
not measured
Conclusions:
In a study similar to OECD TG 307 (Aerobic and Anaerobic Transformation in Soil), the aerobic degradation rate constants and resulting half-lives of 14 PAH were investigated in two different soils. Results can be considered to be acceptable estimates for two- to three-ringed PAHs. For the four- and five-ringed PAHs, the half-lives estimated were longer than the study duration, which indicates that these values are quite uncertain (confirmed by large 95% confidence intervals for many of these PAHs). Due to the nature of these recalcitrant PAHs, the values presented must be considered to be best available estimates.
Eight of the PAH in this study (phenanthrene, fluoranthene, pyrene, chrysen, benz[a]anthracene, benzo[b]fluoranthene, benzo[a]pyrene, and indeno[1,2,3-cd]pyrene) are relevant constituents of pitch, coal tar, high-temp. Half-lives determined range from 16 / 35 days (phenanthrene) to 371 / 387 days (chrysene) (soil #1 / #2, respectively).
The test results of the source substances (range of half-lives from 16/35 d (phenanthrene) to 371/387 d (chrysene)) are adopted as weight of evidence for the target substance pitch, coal tar, high-temp.
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted prior to the release of OECD TG 307. It was performed as static soil microcosm incubation test following the general principles of OECD guideline 307. Results (half-lives) are based on measurements of residual unaltered parent compounds, no mineralisation test. Test materials are 14 PAHs. They were applied as components of a predominantly domestic sewage sludge. In addition, one soil type (no history of sludge application) was spiked with a PAH standard.
GLP compliance:
not specified
Test type:
laboratory
Specific details on test material used for the study:
14 PAH were tested in this study ranging from naphthalene to coronene (two- to seven-ring PAH). Eight compounds among them are relevant as constituents of pitch, coal tar, high-temp (CTPht). These are covered in this study record.

Compound CAS no.

Phenanthrene 85-01-8
Fluoranthene 206-44-0
Pyrene 129-00-0
Chrysene / Benz[a]anthracene 218-01-9 / 56-55-3
Benzo[b]fluoranthene 205-99-2
Benzo[a]pyrene 50-32-8
Benzo[ghi]perylene 191-24-2
Radiolabelling:
no
Oxygen conditions:
aerobic
Soil classification:
not specified
Year:
1993
Soil no.:
#1
Soil type:
sandy clay loam
% Clay:
20
% Silt:
24
% Sand:
50
% Org. C:
6.04
pH:
6.6
CEC:
2.59 meq/100 g soil d.w.
Soil no.:
#2
Soil type:
sandy clay loam
% Clay:
20
% Silt:
15
% Sand:
57
% Org. C:
8.11
pH:
6.1
CEC:
1.68 meq/100 g soil d.w.
Soil no.:
#3
Soil type:
other: forest soil
% Org. C:
58
pH:
2.9
CEC:
8.53 meq/100 g soil d.w.
Soil no.:
#4
Soil type:
sandy loam
% Clay:
11
% Silt:
23
% Sand:
57
% Org. C:
9.3
pH:
6.4
CEC:
2.91 meq/100 g soil d.w.
Details on soil characteristics:
SOIL TYPES
Four types of soil were used:
- No. #1: AS1 = rural agricultural soil, no previous sludge application
- No. #2: AS2 = rural agricultural soil that has received at least 10 separate surface applications of sewage sludge over the past 10 years, totalling about 95 t (dry weight) per hectare
- No. #3: FS = rural coniferous forest soil
-No. #4: RS = roadside soil (from the side of a major road)
AS1 and AS2 came from adjacent fields.

SOIL COLLECTION AND STORAGE
- Geographic location: Lancaster area, not further specified
- Pesticide use history at the collection site: no data
- Collection procedures: no data
- Sampling depth (cm): 0 - 15 cm
- Soil preparation (e.g., 2 mm sieved; air dried etc.): soils were partially dried until they could be sieved through a 2-mm mesh size

SEWAGE SLUDGE COLLECTION AND STORAGE
- Geographical location: sewage treatment plant serving Lancaster, an urban/light industrial catchment
- Location in sewage treatment plant: primary settlement beds; the sludge had been anaerobically digested
- Collection procedures: no data
- Consistency: only 5 % of the sludge was dry matter, of which 56 % was organic matter
Soil No.:
#1
Duration:
205 d
Soil No.:
#2
Duration:
205 d
Soil No.:
#3
Duration:
205 d
Soil No.:
#4
Duration:
205 d
Soil No.:
#1
Initial conc.:
other: see Table below under 'Any other information on materials and method incl. tables'
Soil No.:
#2
Initial conc.:
other: see Table below under 'Any other information on materials and method incl. tables'
Soil No.:
#3
Initial conc.:
other: see Table below under 'Any other information on materials and method incl. tables'
Soil No.:
#4
Initial conc.:
other: see Table below under 'Any other information on materials and method incl. tables'
Parameter followed for biodegradation estimation:
test mat. analysis
Soil No.:
#1
Temp.:
20 -30 °C
Microbial biomass:
no data
Soil No.:
#2
Temp.:
20 to 30 °C
Microbial biomass:
no data
Soil No.:
#3
Temp.:
20 - 30 °C
Microbial biomass:
no data
Soil No.:
#4
Temp.:
20 - 30 °C
Microbial biomass:
no data
Details on experimental conditions:
EXPERIMENTAL DESIGN
Test materials were added to the soil either in form of sewage sludge that contained PAH, or the soil was spiked with a PAH standard in dichloromethane (DCM) (see below)
- Soil condition: air dried and sieved
- Soil (g/replicate): 500 g dw except for FS soil (soil #3), here only 150 g dw were used due to high moisture content and low bulk density of the soil
- Control conditions, if used: untreated and sterile soil (irradiation by 32.2 kGy, amended sludge was also irradiated, and addition of sodium azide (1% weight) for complete sterilisation).
- No. of replication controls, if used: no data
- No. of replication treatments: no data
- Test apparatus (Type/material/volume): glass jars 20 cm tall and 9 cm in diameter
- Moisture content: all soils were watered with distilled/deionised water to provide a moisture content of 25 to 30 %, except soil #3 (FS, forest soil) with a moisture content of 60 %.
- Details of traps for CO2 and organic volatile, if any: no traps used
- If no traps were used, is the system closed/open: closed, jars were covered with polyethylene film to prevent excessive moisture loss and and encourage free entry of oxygen.
- Identity and concentration of co-solvent: see below
- Storage of test vessels: microcosms were placed in a greenhouse, where the temperature ranged from 20 to 30 °C over the duration of the experiment (205 d).

Test material application
Sewage sludge (source of PAH)
- Soils treated: all soils (#1 to #4) were amended with sewage sludge
- Amount of sludge per treatment: sludge was applied to the soils in measured liquid quantities to represent a sludge application rate of approx. 85 t (dry weight) per hectare.
- Application method: the soil material was thoroughly mixed after application of sludge; the sludge-amended soils required drying after application and were subsequently disaggregated.
Spiking with PAH standard
- Soils treated: only soil #1 (AS1, rural agricultural soil, no previous sludge application) was treated
- Volume of test solution used/treatment: no data
- Application method (e.g. applied on surface, homogeneous mixing etc.): the PAH standard was diluted in 100 g of DCM and applied over the soil followed by thorough mixing. The DCM was immediatly allowed to evaporate, and the soil was mixed again. Even spiking of the soil was thus achieved.
- Is the co-solvent evaporated: yes

Any indication of the test material adsorbing to the walls of the test apparatus: no data

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: soils were watered when necessary.
- Continuous darkness: no

OXYGEN CONDITIONS (delete elements as appropriate)
- Methods used to create/maintain the aerobic conditions: when soil samples were taken (see below), the soils were mixed to ensure good aeration

SAMPLING DETAILS
- Sampling intervals: after 0, 16, 21, 38, 66, 120, and 205 days
- Sampling method for soil samples: no data, sample size approx. 10 g
- Sterility check, if sterile controls are used: no data
- Sample storage before analysis: no data
Key result
Soil No.:
#1
DT50:
108 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material phenanthrene, applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
110 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material fluoranthene, applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
285 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material pyrene;applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
199 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benz[a]anthracene/chrysene, applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
135 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 20 °C
Remarks on result:
other: test material benzo[b]fluoranthene, applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
120 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benzo[a]pyrene, applied as ingredient of sewage sludge
Key result
Soil No.:
#1
DT50:
460 d
Type:
zero order
Temp.:
20 - 30 °C
Remarks on result:
other: test material benzo[ghi]perylene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
192 d
Type:
zero order
Temp.:
20 - 30 °C
Remarks on result:
other: test material phenanthrene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
184 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material fluoranthene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
167 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material pyrene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
106
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benz[a]anthracene/chrysene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
113 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benzo[b]fluoranthene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
270 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benzo[a]pyrene, applied as ingredient of sewage sludge
Key result
Soil No.:
#2
DT50:
365 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: test material benzo[ghi]perylene, applied as ingredient of sewage sludge
Transformation products:
not specified
Evaporation of parent compound:
no
Remarks:
for both soil types and all test materials relevant for CTPht, abiotic loss was not significantly different from zero loss except for phenanthrene in soil #2. Here, abiotic loss was 47 % over the period of the experiment.
Details on results:
TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): no data reported

Abiotic losses

 

Abiotic loss of PAH from soils were determined using the sterilised soil samples (treated by irradiation and sodium azide) assuming a linear rate of loss. Results are presented in the following table

 

Table 1: Estimated abiotic losses (percentage of losses and loss rates in µg/kg dw/day) from irradiated/sodium azide-treated soils over the whole experimental period (Table 3 of publication)

 

 

AS1

AS2

FS

RS

Spiked soil

Compound

%

Rate

%

Rate

%

Rate

%

Rate

%

Naphthalene

99*

0.1207

86*

0.1114

100*

1.0150

75*

0.3650

100

Acenaphthene/Fluorene

34*

0.1347

44*

0.0661

56*

0.4550

77*

0.6100

91

Phenanthrene

0

0.0000

47*

0.5214

34*

0.6950

24*

0.2450

73

Anthracene

12*

0.0181

18*

0.0100

32*

0.2160

17*

0.0650

71

Fluoranthene

0

0.000

6.3

0.1350

20*

0.8800

5.5

0.3400

34

Pyrene

0

0.000

0

0.0000

3.4

0.0550

13

0.2450

65

Benz[a]anthracene/Chrysene

0

0.000

3.7

0.0150

3

0.0350

13

0.1150

11

Benzo[b]fluoranthene

0

0.000

0

0.0000

0

0.0000

5.9

0.0500

0.3

Benzo[k]fluoranthene

14

0.0181

13

0.0300

0

0.0000

0

0.0000

0

Benzo[a]pyrene

8.2

0.0400

5.9

0.0300

1.3

0.0110

0.9

0.0100

11.9

Benzo[ghi]perylene

0

0.0000

11

0.0750

1.3

0.0100

4.5

0.0950

0

Coronene

0

0.0000

0

0.0000

0

0.0000

1.4

0.0050

11.9

AS1 = rural agricultural soil, no previous sludge application

AS2 = rural agricultural soil

FS = rural coniferous forest soil

RS = roadside soil

* Significantly different from zero Loss (0.05)

 

Compound structure strongly influences abiotic losses. The lower-molecular weight PAH with fewer than four rings all appear to be susceptible to non-biological degradation mechanisms. Losses of these compounds were collectively significantly different from zero loss (p = 0.05).

 

Biodegradation (including losses by non-biological processes) for sludge-amended and for spiked soils

 

Losses of PAH due to combined biological and non-biological mechanisms were estimated from sludge-amended soil samples. Significant losses of the higher-molecular-weight PAH occurred, probably due to biological processes. However, it is possible that some PAH are strongly associated with the soil humus and become much less readily extracted.

 

Losses were modelled by linear or first-order regression methods. Half-lives were derived from the regression equations given as the best fit.

 

Table 2: Half-lives (days) derived for soils used in the microcosm study (percentage of losses are shown in parentheses) (combined Table 4 and 5 of publication)

 

 

AS1

AS2

FS

RS

 

 

AS1

Compound

Soil

R2

Soil

R2

Soil

R2

Soil

R2

Mean

SD

Spiked soil

R2

Naphthalene

33 (100)

0.72

16 (100)

0.86

14 (95)

0.67*

48 (91)

0.54*

28

16.0

15

0.98

Acenaphthene/Fluorene

74 (86)

0.68

70 (84)

0.88

73 (100)

0.90*

44 (96)

0.94

65

14.3

28

0.99

Phenanthrene

108 (85)

0.88

193 (50)

0.8*

112 (56)

0.63*

83 (94)

0.55*

124

47.8

14

0.996

Anthracene

48 (61)

0.88*

210 (22)

0..34

105 (90)

0.54*

200 (59)

0.98

141

77.9

48

0.96

Fluoranthene

110 (78)

0.88

184 (35)

0.69

143 (60)

0.93

110 (73)

0.6

137

35.1

16

0.95

Pyrene

285 (36)

0.69

167 (49)

0.78

320 (20)

0.57*

127 (57)

0.90*

225

92.4

51

0.68

Benz[a]anthracene/Chrysene

199 (66)

0.68

106 (76)

0.79

313 (34)

0.42*

240 (67)

0.94*

215

86.3

84

0.92

Benzo[b]fluoranthene

135 (90)

0.65

113 (44)

0.63

279 (8)

0.22*

282 (34)

0.93*

202

90.8

334

0.73

Benzo[k]fluoranthene

350 (53)

0.93

143 (57)

0.76*

351 (8)

0.23

359 (30)

0.97*

301

105.2

55

0.62

Benzo[a]pyrene

120 (85)

0.62

270 (18)

0.9

197 (44)

0.43*

258 (48)

0.92*

211

68.7

112

0.98

Benzo[ghi]perylene

460 (15)

0.75*

365 (20)

0.7

460 (16)

0.83

535 (25)

0.73*

455

69.6

282

0.89

Coronene

2,030 (16)

0.65

603 (14)

0.79

753 (17)

0.55

669 (7)

0.41

1,014

680.3

789

0.68

Sum of PAH

146

0.90

165

0.85*

192

0.79*

177

0.82

170

19.4

124

0.79

 

AS1 = rural agricultural soil, no previous sludge application

AS2 = rural agricultural soil

FS = rural coniferous forest soil

RS = roadside soil

* Linear regression

 

The expected increase in half-life with increasing molecular weight was observed in all the soils. Abiotic loss processes are clearly very important for some of the low-molecular-weight PAH, possibly more important than biodegradation.

 

In the sludge-amended AS2 and the RS soils, sum of PAH concentrations started to fall immediately after sludge application. Reduction in sum of PAH concentrations were not detected in the AS1 and FS soil until 40 to 80 days after application, suggesting that PAH degradation began much more rapidly in the soils with previous exposure to PAH, whereas the other soils required a period of acclimation.

 

The loss of spiked PAH from the AS1 soil were more rapid than the loss of sludge-applied PAH (Table 2). Losses by abiotic processes are higher for spiked PAH than for sludge-applied PAH (Table 1). Overall, the half-life data derived for the spiked PAH are significantly lower than those for all the sludge-applied compounds. PAH spiked to soil are more susceptible to biological and abiotic loss mechanisms and do not mimic the behaviour of sludge-applied PAH compounds. Application of sewage sludge increases the soil adsorption potential, thus higher losses of spiked PAH may be observed in the lower organic matter content of the soil.

Conclusions:
Sewage sludge containing PAH were applied in microcosm studies to four different soils (AS1, AS2, FS, and RS). One of the soils (AS1) was also dirctly spiked using PAH standard in solution. Pretreatment concentrations of PAH were already present in all four soils. FS and RS contained the highest PAH concentrations, while original concentaitons in AS1 and AS2 were much lower. Loss of parent compounds (biodegradation and abiotic losses) was measured over the period of the experiment. From the data, half-lives were calculated using linear of first-order regression models. Equations with the best fit were used to deive the half-lives.
Abiotic losses were considerable for PAH with fewer than four rings with abiotic losses reversly related to size and molecular weight of of the PAH. For four and more ring PAH, abiotic losses were not anymore significantly different from zero loss.
Half-lives determined for three and more ring PAH relevant for pitch, coal tar, high temp. in soil AS1 and AS2 ranged from 48 d (anthracene, soil AF1) to 460 days (benzo[ghi]perylene, soil AS1)
Endpoint:
biodegradation in soil: simulation testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source test materials are individual polycyclic aromatic hydrocarbons ranging from two- to six-ring PAH. Depending on size/molecular weight and state of condensation, physico-chemical and environmental properties can be different. The target substance pitch, coal tar, high-temp. is composed of a broad range of PAH differing in size and degree of condensation.
The ability of CTPht to biodegrade in soil will be determined by the range of PAH that constitute its composition. Several of the source substances are major constituents of CTPht. Therefore, results obtained from biodegradation studies in soil with these compounds can be used in order to characterise the soil biodegradation potential of CTPht.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemicals are individual PAH. These include major constituents of CTPht. PAH were applied by two methods. First, STP sludge containing PAH were mixed with soil. Presence and amount of PAH was determined by analytical verification. Second, a commercial standard solution of PAH was added to soil samples. Both methods guarantee, that individual PAH are present in the experiments. Data were collected for individual PAH and test results reported relate to the individual test substances.
The target material pitch, coal tar, high-temp. (CTPht) is a UVCB substance. It is the product (residue) of the oxygen free high-temperature distillation of coal tar and consists of a complex mixture of polycyclic aromatic hydrocarbons, predominantly of highly condensed aromatic ring systems forming an inert matrix. In this matrix, individual PAH with a lower degree of condensation are included. This fraction is small (only ca. 20 % of the substance will evaporate at a distillation temperature up to 500 °C) and comprises polycyclic aromatic hydrocarbons with predominantly four and five, up to six annulated rings. Concentration is between ca. 0.02 and ca. 1.1 % (maximum 1.5 %). Water solubility of the substance is very low (ca. 0.24 mg dissolved C/L at a loading of 1000 mg substance/L or 1.3 µg/L sum of EPA PAH at a loading of 100 mg substance/L). Obviously, individual PAH will dissolved only at concentrations below their maximum water solubility.

3. ANALOGUE APPROACH JUSTIFICATION
Properties of the target substance CTPht regarding behaviour and fate in the environment will be determined by the properties of the PAH that are constituents of CTPht. Under environmental conditions or during processing of the target substance, environmentally available (volatile or water soluble) components of CTPht can be released. These will be predominantly four- to six-ring PAH (see above). They will be distributed in the environment and may also undergo biodegradation in soil.
Eight of these PAH (one three-ring, four four-ring and three five- and six-ring PAH) are included within the set of source substances. Biodegradation properties of these PAH in soil considered together will be specific for the environmental behaviour of CTPht. Therefore, it is justified to use date determined for individual PAH that are constituents of CTPht to characterise the environmental behaviour (biodegradation in soil) of pitch, coal tar, high-temp. (CTPht) itself.
Reason / purpose for cross-reference:
read-across source
Principles of method if other than guideline:
Read-across to preceding entry:
Source test material: polycyclic aromatic hydrocarbons (PAH), generic mixture;
Reference: Wild et al. 1993
Key result
Soil No.:
#1
DT50:
>= 106 - <= 460 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 - 30 °C
Remarks on result:
other: range of half-lives of major constituent of pitch,coal tar, high-temp. characterising the soil biodgradation potential of the substance
Remarks:
the test results are adopted as weight of evidence for the target substance CTPht
Transformation products:
not specified

Description of key information

Biodegradation of PAH in soil has been investigated in two studies similar to OECD TG 309. In both studies, dissipation half-lives showed a substantial variance. Eight of the substances examined are constituents of Pitch, coal tar, high-temp. In one study, biodegradation was tested in two different soils, while in the second study four soils were used. Half-lives ranged in the first study from 16 days to 377 days and in the second study from 48 to 535 days. A 90th percentile value is selected as key value for the chemical safety assessment (see below).

Key value for chemical safety assessment

Half-life in soil:
370 d
at the temperature of:
20 °C

Additional information

CTPht is a solid UVCB substance consisting of an inert matrix, in which individual PAH are enclosed. PAH comprise mainly four- and five-ring polycyclic aromatic compounds. Major constituents that are also part of the 16 EPA PAH are phenanthrene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene, Indeno[1,2,3-cd]pyrene and benzo[ghi]perylene with concentrations between approx. 0.3 and 1.1 %. Biodegradation studies in soil (simulation tests) for anthracene oil itself are not available.

Due to the complex composition of CTPht, a distinct half-life in soil for the substance as a whole cannot experimentally be determined. Main components (all PAH) will have their individual half-lives and in combination can be used to specify a soil biodegradation half-life of anthracene oil.

Experimental results for individual PAH (Park et al. 1990, Wild and Jones 1993) show a high variability of half-lives especially when determined in different soils. There is a tendency that soil biodegradation half-lives of PAH increase with growing molecular size and ring-number. But the high variability indicates that there are other important factors that affect soil biodegradation. 14 PAH were used in these studies, eight of them constituents of CTPht that is, one PAH with three annulated aromatic rings (phenanthrene), four PAH comprising four-ring aromatic systems (fluoranthene, benz[a]anthracene, pyrene, and chrysene), and three five- and six-ring PAH (benzo[b]fluoranthene, benzo[a]pyrene, and either indeno(1,2,3-cd)pyrene or benzo[ghi]perylene).

In the study of Wild and Jones, PAH were not directly added to soil as in the study of PARK et al., but applied as components in STP sludge. Biodegradation of test materials was investigated in two different soils (Park et al.; test duration in soil #1 196 days and in soil #2 105 days) or in four different soils (Wild and Jones; test duration uniformly 205 days). The four soils used in the study of Wild and Jones were very different resulting in quite different biodegradation half-lives. Besides other differences, original PAH content in two agricultural soils were quite similar, while PAH concentrations in the two other soils before treatment were distinctly higher. For the following evaluation, only the two agricultural soils with low original PAH burdens are considered.

For components of CTPht, half-lives between 16 days (phenanthrene) and 387 days (chrysene) were determined in the study of Park et al., while in the study of Wild and Jones half-lives ranged from 106 days (benz[a]anthracene / pyrene) to 460 days (benzo[ghi]perylene).

Phenanthrene was best biodegraded in the two different soils of Park et al. with half-lives of 16 and 35 days. Most persistent was chrysene with half-lives of 371 and 387 days. In the study of Wild and Jones, chrysene/benz[a]anthracene (substances not separated during analysis) was biodegraded best (half-lives of 135 and 113 days in soils AS1 and AS2, respectively), while benzo[ghi]perylene was the most persistent PAH (half-lives of 460 and 365 days in soils AS1 and AS2, respectively. The higher half-lives observed in the study of Park et al. in soil #2 bear some uncertainties, as the duration of the tests (105 days) was considerably shorter than the half-lives determined.

The study results clearly indicate that soil biodegradation half-lives of substantial components of CTPht have values far above 120 and 180 days, the P / vP criteria of REACH Regulation, Annex XIII. In order to specify a value for the total of CTPht, the data are combined that have been obtained in the two studies and in four different soils (two soils considered relevant in each study). The approximate 90 percentile of this data set calculated using the QUANTIL.INKL function in MS Excel 2013 is used as key value in the chemical safety assessment (half-life of 370 days). This approach takes into account the broad range of different PAH constituents of CTPht and the high variability of half-lives determined for these substances.