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Biodegradation in soil

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Endpoint:
biodegradation in soil, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
unsuitable test system
Qualifier:
no guideline available
Principles of method if other than guideline:
An organism capable of growth on pyridine was isolated from soil by enrichment culture techniques and identified as Micrococcus luteus. This organism was then exposed to substituted monoaminopyridines. Degradation of substituted pyridines was measured as the decrease in absorbance at an appropriate wavelength in the UV, and samples were periodically scanned from 300 to 200 nm to detect the formation of UV-absorbing intermediates.
GLP compliance:
not specified
Test type:
laboratory
Radiolabelling:
no
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Remarks:
Chalmers silt loam soil.
Year:
1985
Soil no.:
#1
Soil type:
silt loam
Details on soil characteristics:
Not specified.
Parameter followed for biodegradation estimation:
other: decrease in absorbance at an appropriate wavelength in the UV.
Soil No.:
#1
Temp.:
24ºC
Details on experimental conditions:
EXPERIMENTAL DESIGN:
- A Chalmers silt loam soil, not previously exposed to pyridine, was used as an inoculum for enrichment cultures. The medium contained basal salts (10), yeast extract (150 mg/L), and pyridine (0.01 M). The soil was perfused with pyridine enrichment medium in a rotary perfusion device. Perfusion of the soil resulted in enrichment of a gram-positive, aerobic, furazolidone-resistant coccus which was identified as a Micrococcus luteus. Cells were maintained on pyridine agar slants at 4°C. Growth was measured as optical density at 540 nm and expressed as cell density (dry weight) based on standard curves. Measurement at 540 nm avoided interference from a soluble yellow pigment produced by M. luteus when grown on pyridine.
- In the following experiments, cells were cultured in the above salts medium with yeast extract and various carbon sources at 24°C.
- Degradation of pyridine derivatives by washed cells was measured in cell extracts and suspensions of succinate- and pyridine-grown cells. Substrate solutions contained 4 mM formate, formamide, or pyridine derivatives in 33 mM phosphate buffer (pH 7). Buffered substrate solution (40 ml) was used for suspension of 12 mg (dry weight) of pyridine- or succinate-grown cells or was mixed with cell extract (2.5 mg protein) from pyridine- or succinate-grown cells. Samples were incubated at 24°C, agitated vigorously every 5 min with a Pasteur pipette, and sampled for pyridine over a 120-min period.
- Degradation of pyridine derivatives was measured in reaction mixtures containing cell extract (0.25 mg of protein), phosphate buffer (100 μmol; pH 7), 2-, 3-, 4-, or 3-hydroxypyridines (1μmol) with or without NAD(P) (1μmol), NAD(P)H (1μmol), flavin adenine dinucleotide (1 ,umol), or flavin mononucleotide (1 μmol) in a total volume of 3 ml. Pyridine derivatives were measured by UV spectrophotometry.
Key result
Soil No.:
#1
% Degr.:
0
Parameter:
other: UV absorbance.
Sampling time:
120 min
Transformation products:
no
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
M. luteus was unable to grow at the expense of any of the substituted pyridines tested. Some compounds, like 2-aminopyridines, appeared to be toxic to M. luteus and abolished the small amount of growth produced by yeast extract (150 mg/L) present in all treatments. Analysis of pyridine derivatives in cultures showed no difference between inoculated and uninoculated treatments.

Table 1. Permeability of M. luteus to substituted pyridines.

Substituent

Position of substituent(s)

None (pyridine)

9.5

-NH2

2

4.1

-NH2

2, 6

2.4

ª R values corrected for interstitial volume by determining uptake for high molecular-weight dextran.

Conclusions:
Under test conditions, no biodegradation was observed. Furthermore, it appeared to be toxic to M. luteus. Therefore, the test item is not biodegradable in soil.
Executive summary:

An organism capable of growth on pyridine was isolated from soil by enrichment culture techniques and identified as Micrococcus luteus. This organism was then exposed to substituted monoaminopyridines. Degradation of substituted pyridines was measured as the decrease in absorbance at an appropriate wavelength in the UV, and samples were periodically scanned from 300 to 200 nm to detect the formation of UV-absorbing intermediates. M. luteus was unable to grow at the expense of any of the substituted pyridines tested. Some compounds, like 2-aminopyridines, appeared to be toxic to M. luteus and abolished the small amount of growth produced by yeast extract (150 mg/L) present in all treatments. Analysis of pyridine derivatives in cultures showed no difference between inoculated and uninoculated treatments. Therefore, the test item is not biodegradable in soil.

Endpoint:
biodegradation in soil, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline available
Principles of method if other than guideline:
The procedure used to determine the susceptibility of pyridine compounds to degradation by a mixed population of soil micro-organisms was similar to that used by Alexander and Lustigman (1966) for substituted benzenes (see attached background material); these authors discussed the limitations of the techniques employed.
GLP compliance:
not specified
Test type:
laboratory
Specific details on test material used for the study:
- Identification: no. 26
- Source: Aldrich Chemical Co., Wisconsin, U.S.A. / Fluka A.G., Chemische Fabrik, Switzerland.
Radiolabelling:
no
Oxygen conditions:
aerobic/anaerobic
Soil classification:
not specified
Remarks:
fertile garden soil
Year:
1971
Soil no.:
#1
Soil type:
other: fertile garden soil
pH:
7
Details on soil characteristics:
Not specified.
Soil No.:
#1
Duration:
256 d
Soil No.:
#1
Initial conc.:
1 other: mM
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: UV absorbance
Soil No.:
#1
Temp.:
25 ºC
Details on experimental conditions:
EXPERIMENTAL DESIGN
- Soil (g/replicate): 0.5% aqueous suspension
- Test apparatus (Type/material/volume): 100 x 15 mm diam. culture tubes.
- If no traps were used, is the system closed/open: For aerobic conditions, loosely capped tubes contained 5 ml (open) and for anaerobic conditions, tightly closed tubes contained 11.5 ml (closed).

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

Experimental conditions (in addition to defined fields)
- Continuous darkness: Yes

SAMPLING DETAILS
- Sampling intervals: approximately 2, 4, 8, 16, 32, 64, 128, 160 and 256 days.
Key result
Soil No.:
#1
% Degr.:
< 1
Parameter:
other: UV absorption.
Sampling time:
96 d
Transformation products:
not specified
Remarks:
Some times as peaks disappeared new ones appeared, due to the formation of decomposition products.
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
No decomposition of the test item occured after 96 days, either in aerobic or anaerobic conditions.

Table 1. Degradation and Phytotoxicity of Pyridines.

Number

Chemical

Decomposition

Phytotoxicity range

Aerobic

(days)

Anaerobic

(days)

25

2-aminopyridine

> 96

> 96

< 2.0 – 4.0

38

Pyridine

> 66 < 170

> 32 < 66

< 0.9 – 1.9

 

Conclusions:
No decomposition of the test item occured after 96 days under test conditions, either in aerobic or anaerobic conditions. Therefore, it is not biodegradable in soil.
Executive summary:

A study on the persistence of substituted pyridines in soil was performed according to a method by Alexander and Lustigman (1966). Persistence was measured in enrichment cultures by testing 1 mM solutions of test item in an aqueous suspension of 0.5 % fertile garden soils, 20 parts/10^6 each of Difco yeast extract, Oxoid peptone and glucose, 4 parts/10^6 (NH4)2SO4 and 180 parts/10^6KH2PO4 adjusted to pH 7.0 with KOH. These suspensions were incubated in 100 x 15 mm diam. culture tubes - for aerobic conditions, loosely capped tubes contained 5 ml and for anaerobic conditions, tightly closed tubes contained 11.5 ml. At intervals of approximately 2, 4, 8, 16, 32, 64, 128, 160 and 256 days, 1 ml samples were suitably diluted, filtered through No. 42 Whatman paper to remove suspended matter and the absorption spectra recorded from 210 to 330 run. The spectra were compared with those of similar suspensions to which 200 parts/10^6 HgCl2 had been added to suppress microbial activity. The number of days incubation required for disappearance of characteristic peaks was given as a result. No decomposition of the test item occured after 96 days under test conditions, either in aerobic or anaerobic conditions. Therefore, it is not biodegradable in soil.

Endpoint:
biodegradation in soil, other
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline available
GLP compliance:
not specified
Conclusions:
According to the Handbook of Environmental data on organic chemicals (peer reviewed handbook data), of 17 mg/kg incubated in soil at pH 7 and 28ºC, < 1% degraded within 30 d, as evidenced via the release of inorganic nitrogen. Therefore, the test item is not biodegradable in soil.
Executive summary:

According to the Handbook of Environmental data on organic chemicals (peer reviewed handbook data), of 17 mg/kg incubated in soil at pH 7 and 28ºC, < 1% degraded within 30 d, as evidenced via the release of inorganic nitrogen. Therefore, the test item is not biodegradable in soil.

Description of key information

Weight of evidence: Based on results from available studies meeting genereally accepted scientific principles and peer reviewed handbook data, the test item is not biodegradable in soil.

Key value for chemical safety assessment

Additional information

The following information was available for the test item:

- An organism capable of growth on pyridine was isolated from soil by enrichment culture techniques and identified as Micrococcus luteus. This organism was then exposed to the test item, and its degradation was measured as the decrease in UV absorbance at an appropriate wavelength. The test item was not degraded by M. luteus, and appeared to have an inhibitory effect. Therefore, the test item is not biodegradable in soil.

- A study on the persistence of the test item in soil was performed according to a method by Alexander and Lustigman (1966). Persistence was measured in enrichment cultures by testing 1 mM solutions of test item in an aqueous suspension of 0.5 % fertile garden soils, 20 parts/10^6 each of Difco yeast extract, Oxoid peptone and glucose, 4 parts/10^6 (NH4)2SO4and 180 parts/10^6KH2PO4adjusted to pH 7.0 with KOH. These suspensions were incubated in 100 x 15 mm diam. culture tubes - for aerobic conditions, loosely capped tubes contained 5 ml and for anaerobic conditions, tightly closed tubes contained 11.5 ml. At intervals of approximately 2, 4, 8, 16, 32, 64, 128, 160 and 256 days, 1 ml samples were suitably diluted, filtered through No. 42 Whatman paper to remove suspended matter and the absorption spectra recorded from 210 to 330 run. The spectra were compared with those of similar suspensions to which 200 parts/10^6 HgCl2had been added to suppress microbial activity. The number of days incubation required for disappearance of characteristic peaks was given as a result.No decomposition of the test item occured after 96 days under test conditions, either in aerobic or anaerobic conditions. Therefore, it is not biodegradable in soil.

- According to the Handbook of Environmental data on organic chemicals (peer reviewed handbook data), of 17 mg/kg incubated in soil at pH 7 and 28ºC, < 1% degraded within 30 d, as evidenced via the release of inorganic nitrogen. Therefore, the test item is not biodegradable in soil.