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Environmental fate & pathways

Biodegradation in soil

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Administrative data

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:
other: Study based on accepted scientific principles, well documented, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Fate of PAH compounds in two soil types: influence of volatilization, abiotic loss and biological activity.
Author:
Park KS, Sims RC, Dupont RR, Doucette WJ, Matthews JE
Year:
1990
Bibliographic source:
Environ. Toxicol. Chem., 9, 187-195 (1990)

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Principles of method if other than guideline:
Method: Static soil incubation test: Determination of volatilization and biodegradation in closed bottle tests / comparative study including various PAH (see below)
GLP compliance:
not specified
Test type:
laboratory

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): anthracene
- Source: Aldrich Chemical Co.
Radiolabelling:
no

Study design

Oxygen conditions:
aerobic
Soil classification:
not specified
Soil propertiesopen allclose all
Soil no.:
#1
Soil type:
other: Kidman sandy loam
% Org. C:
0.5
pH:
7.9
CEC:
10.1 meq/100 g soil d.w.
Soil no.:
#2
Soil type:
other: McLaurin sandy loam
% Org. C:
1.1
pH:
4.8
CEC:
4.4 meq/100 g soil d.w.
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: Kidman sandy loam(Calciaquoll, Utah) / McLaurin sandy loam (Paleudult, Mississippi)
- Sampling depth (cm): 0 - 0.15 cm
- Soil preparation: 2 mm sieved; air dried

PROPERTIES OF THE SOILS (in addition to defined fields)
- Moisture at 1/3 atm (%): 16.3 (Kidman) / 12.4 (McLaurin)
- Bulk density (g/cm3): no data
- microbial colonisation: 1# Kidman 6.7 x10^6 bacterial CF/g soil; 1.9 x10^4 fungal CF/g soil
2# Mc Laurin 6.7 x10^6 bacterial CF/g soil; 1.9 x10^4 fungal CF/g soil
Duration of test (contact time)open allclose all
Soil No.:
#1
Duration:
196 d
Soil No.:
#2
Duration:
105 d
Initial test substance concentrationopen allclose all
Soil No.:
#1
Initial conc.:
210 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#2
Initial conc.:
199 mg/kg soil d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
Experimental conditions
Humidity:
16.3 other: -1/3 bar
Details on experimental conditions:
Static soil incubation test:

1. PRELIMINARY EXPERIMENTS:
VOLITILISATION TEST
- Soil condition: air dried, sieved
- Soil amount: 200 g dw per test, moistened
- Soil preincubation conditions: 1 week before start, 25 °C, moistened
- Moisture: >=60 % of water holding capacity (soil water matric potential: -33 J/kg)

VOLITILISATION procedure
- Test apparatus: 500 mL Erlenmeyer flask
- Soil amount: 200 g dw, moistened (loss of water checked and compensated for by daily weight control)
- Control conditions: 1. poisoned with 2 % HgCl2 to evaluate abiotic loss
2. soil only
- Test flask soil with single PAH
- Temperature: 25 °C
- Duration: 48 h
- Details of traps for CO2 and organic volatile: Tenax sorbent tube with methanol as carrier solvent
Purge rate: 200 mL/min
- Soil sampling: 20 g dw were withdrawn at 0, 8, 24, and 48 h and analysed for PAH by HPLC after methanol extraction.


2. EXPERIMENTAL DESIGN: MAIN TEST
- Soil preincubation conditions: 1 week before start, 25 °C, moistened
- Moisture: >=60 % of water holding capacity (soil water matric potential: -33 J/kg)
- Soil condition: air dried, sieved
- Soil (g/replicate): 40 g dw
- Control conditions: 1 per time point, poisoned with 2 % HgCl2 to evaluate abiotic loss
- No. of replication controls: 3 per time point
- No. of replication treatments: 3 per time point
- Test apparatus (Type/material/volume): 500 mL Erlenmeyer flask, covered with polyethylene film
- Details of traps for CO2: none
- If no traps were used, is the system: open

Test material application
- Volume of test solution used/treatment: no data, dissolved in dichloromathane
- Is the co-solvent evaporated: yes

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: weight control
- Continuous darkness: Yes

3. OXYGEN CONDITIONS
- Methods used to create the an/aerobic conditions: open system

4. SAMPLING DETAILS
- Sampling intervals: Kidman soil 0, 42, 84, 140, and 196 d
McLaurin soil 0, 35, 70, 105
- Sampling method for soil samples: one flask per time interval

Results and discussion

Half-life / dissipation time of parent compoundopen allclose all
Soil No.:
#1
DT50:
134 d
Type:
not specified
Remarks on result:
other: average with CI 106 - 182 d
Soil No.:
#2
DT50:
50 d
Type:
not specified
Remarks on result:
other: average with CI 42 - 61
Transformation products:
no
Evaporation of parent compound:
yes
Volatile metabolites:
no
Residues:
yes
Details on results:
Statistical analysis indicated that abiotic degradation was significant for 2- and 3-ring compounds.
The losses were statistically insignificant for the those PAH that contained greater than 3 rings.
Cumulative volatile mass (Park et al. 1990, p. 192)
for naphthalene approx. 30 % from both soils after 48 h,
for 1-methylnaphthalene approx. 15 % (Kidman loam) and approx. 27 % (McLaurin loam) after 48 h,
for all remaining PAH <0.1 % or undetectable from both soils.

Any other information on results incl. tables

BIODEGRADATION

The estimated amounts of biologically degraded PAHs were:

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

Half-lives of biodegradation [days] in brackets:

95-% Confidence Intervals

    

Kilman sandy loam

McLaurin sandy loam

Naphthalene

2.1 [1.7-2.7]

2.2 [1.7-3.4]

1-Methylnaphthalene

1.7 [1.4-2.1]

2.2 [1.6-3.2]

Anthracene

134 [106-182]

50 [42-61]

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 [217]

7,12-Dimethyl-benz[a]anthracene

20 [18-24]

28 [21-41]

Benzo[b]fluoranthene

294 [231-385]

211 [169-277]

Benzo(a)pyrene

309 [239-462

229 [178-315

Dibenz[a,h]anthracene

361 [267-533]]

420 [267-990]

Dibenzo[a,i]pyrene

361 [277-533]

232 [178-330]

Indeno[1,2,3-c,d]-pyrene 193-39-5

288 [224-408]

289 [224-408]

The disappearance of the parent compounds was similar in both soils. The biological degradation of the 2-ring compounds was very rapid, and of 3-ring compounds, too, in particular of phenanthrene which exhibited a more extensive removal than anthracene. 4- and 5-ring PAH were more resistant with half-lives of 100 to 400 days. An exception was 7,12-dimethylbenzanthracene with an average half-life of 24 days.

Applicant's summary and conclusion