Pentapotassium bis(peroxymonosulphate) bis(sulphate)

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

some minor deficiencies in the reporting

Principles of method if other than guideline:

In the report no guideline is indicated.
Oxone® was applied to three different soil types at an initial concentration of 100 ppm. The soil samples were incubated for 1 and 24 hours and then centrifuged for approximately 20 minutes at max speed. The supernatant was decanted and titrated for Oxone® with a DPD (N,N-diethyl-1,4-phenylenediamine sulphate) method. The solid soil residues were washed with demineralised water. After a further centrifugation, these samples were also titrated with the DPD method. In addition to each set of treated samples, a blank was analysed in accordance with the above procedure, however without test substance.

GLP compliance:

not specified

Test type:

laboratory

Radiolabelling:

no

Oxygen conditions:

aerobic

Soil no.:

#1

Soil type:

other: Drummer #7

% Clay:

33

% Silt:

43

% Sand:

24

pH:

6

CEC:

32.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Soil no.:

#2

Soil type:

other: Hildago

% Clay:

26

% Silt:

43

% Sand:

24

pH:

>= 7.81 - <= 8.32

CEC:

14.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Soil no.:

#3

Soil type:

other: Wildlife soil

% Clay:

7

% Silt:

20

% Sand:

73

% Org. C:

0.6

pH:

>= 5.4 - <= 6.1

CEC:

5.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.49

Details on soil characteristics:

PROPERTIES OF THE SOILS
- Moisture:
#1: Wildlife Int. Topsoil; moisture: n.d.
#2: Drummer 7, 2004-073; moisture: 24.12 %
#3: Hidalgo 5S, 2005, 2004-025; moisture: 12.59 %

More details on the soil characteristics are given in table 7.2.1/01-1, which is presented under "Any other information on materials and methods incl. tables"

Initial conc.:

100 ppm

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Soil No.:

#1

Humidity:

not indicated

Soil No.:

#2

Humidity:

24.12%

Soil No.:

#3

Humidity:

12.59%

Details on experimental conditions:

Oxone® was applied to three different soil types at an initial concentration of 100 ppm. The soil samples were incubated for 1 and 24 hours and then centrifuged for approximately 20 minutes at max speed. The supernatant was decanted and titrated for Oxone® with a DPD (N,N-diethyl-1,4-phenylenediamine sulphate) method. The solid soil residues were washed with demineralised water. After a further centrifugation, these samples were also titrated with the DPD method. In addition to each set of treated samples, a blank was analysed in accordance with the above procedure, however without test substance.

Soil No.:

#1

DT50:

10.4 min

Type:

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

Temp.:

ca. 22 °C

Soil No.:

#2

DT50:

11.3 min

Type:

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

Temp.:

ca. 22 °C

Soil No.:

#3

DT50:

9.9 min

Type:

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

Temp.:

ca. 22 °C

Transformation products:

not measured

Calculations

The degradation rate of Oxone® in soil was calculated on basis of a first-order degradation equation:

Ct = C0 × exp (ln2 * t /DT50)

where Ct = concentration of chemical at time t [ppm]

C0 = concentration of chemical at time 0 [ppm]

t = elapsed time [hr]

DT50 = half-life [hr]

Concentration-time data

The concentrations of Oxone® in the different soil samples after 1 and 24 hours of incubation are presented in figures 7.2.1/01-1 to 7.2.1/01-3, see the attached document under "Overall remarks, attachments".

The concentration of Oxone® in soil after one hour of incubation was approximately 1.8 ppm in Wildlife Int. Topsoil, 2.5 ppm in Drummer #7 soil and 1.5 ppm in Hidalgo soil. The Oxone® concentrations in the respective blanks were in the same range. The results from the one hour wash did not indicate that there was any remaining Oxone® in the soil.

Degradation rate, DT50

The measured concentration of Oxone® in soil after 1 hour of incubation does not appear to be different from the blank control values which implies that the product has essentially completely degraded by this time: C0 = 100 ppm (initial test concentration was 100 ppm) Ct = 1.8 ppm (Wildlife Intl Topsoil) Ct = 2.5 ppm (Drummer soil) Ct = 1.5 ppm (Hidalgo soil) The range of observed concentrations of Oxone® in soil at 1 hour correspond to the following DT50 values:

Soil	DT50 [hr]	DT50 [min]
Wildlife Intl Topsoil	0.173	10.4
Drummer soil	0.188	11.3
Hidalgo soil	0.165	9.9
Average:	-	10.5

The actual DT50 of Oxone® in soil is likely to be even shorter than 11 minutes. However, no experimental data were collected for time points shorter than 1 hours to permit a more accurate estimate of DT50 in soil.

Conclusions:

Oxone® decomposes rapidly in soil by getting into contact with organic substances present in the soil. DT50 values were found to be < 11 minutes.

The applicant believes that the above studies are sufficient for this data point, as KMPS is not applied directly to the soil and therefore is not likely to reach the soil compartment. If a small amount reaches the soil compartment, KMPS will rapidly decompose. The pathway for degradation in soil is similar to water in that KMPS either hydrolyses or disproportionates to bisulphate and hydrogen peroxide or oxygen. As stated above, in recent studies, the only sulphur-containing anions observed were the sulphate and bisulphate equilibrium pair.

Executive summary:

Materials and methods

Oxone® was applied to three different soil types at an initial concentration of 100 ppm. The soil samples were incubated for 1 and 24 hours and then centrifuged for approximately 20 minutes at max speed. The supernatant was decanted and titrated for Oxone® with a DPD (N,N-diethyl-1,4-phenylenediamine sulphate) method. The solid soil residues were washed with demineralised water. After a further centrifugation, these samples were also titrated with the DPD method. In addition to each set of treated samples, a blank was analysed in accordance with the above procedure, however without test substance.

 

Results and discussion

The initial nominal concentration Oxone® in soil was approximately 100 ppm. After one hour of incubation, the concentration of Oxone® in soil had decreased to approximately 1.8 ppm in Wildlife Int. Topsoil, 2.5 ppm in Drummer #7 soil and 1.5 ppm in Hidalgo soil. These concentrations are within 0.5 ppm or less of its respective blank that was not treated with Oxone®. Consequently, it can be concluded from the results that after one hour of incubation there is no measurable Oxone® present in the sample.

Description of key information

Oxone® decomposes rapidly in soil by getting into contact with organic substances present in the soil. DT50 values were found to be < 11 minutes.

Key value for chemical safety assessment

Half-life in soil:

11 min

at the temperature of:

22 °C

Additional information

Oxone® was applied to three different soil types at an initial concentration of 100 ppm. The soil samples were incubated for 1 and 24 hours and then centrifuged for approximately 20 minutes at max speed. The supernatant was decanted and titrated for Oxone® with a DPD (N,N-diethyl-1,4-phenylenediamine sulphate) method. The solid soil residues were washed with demineralised water. After a further centrifugation, these samples were also titrated with the DPD method. In addition to each set of treated samples, a blank was analysed in accordance with the above procedure, however without test substance.

The initial nominal concentration Oxone® in soil was approximately 100 ppm. After one hour of incubation, the concentration of Oxone® in soil had decreased to approximately 1.8 ppm in Wildlife Int. Topsoil, 2.5 ppm in Drummer #7 soil and 1.5 ppm in Hidalgo soil. These concentrations are within 0.5 ppm or less of its respective blank that was not treated with Oxone®. Consequently, it can be concluded from the results that after one hour of incubation there is no measurable Oxone® present in the sample.