L-Aspartic acid, N,N'-1,2-ethanediylbis-, sodium salt (1:3)

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

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:

Soil samples were incubated with the test substance and basal and substrate-induced respiration, enzyme activity and potentially mineralizable nitrogen were measured; community level physiological profiles were also determined.

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Vapour pressure: 0.00017 Pa at 25°C
- Henry's law constant (for volatile substances): no data
- Water solubility (under test conditions): ca. 150 mg/L at 25°C and pH 7
- Solubility in organic solvents:
- log Pow: <-1.4
- pKa: no data
- Base or acid catalysis of test material: no data
- log Koc: 1.778
- UV absorption: no data
- Stability of test material at room temperature: stable
- pH dependance on stability: no data

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 1.0 g/kg dw soil
- Sampling method: using MOM-type Rhizons to extract the soil solution free of microbial and colloid contamination.
- Sample storage conditions before analysis: no data

Rate of degradation of EDDS assessed over 3 weeks

Vehicle:

not specified

Details on preparation and application of test substrate:

no data

Test organisms (inoculum):

soil

Total exposure duration:

3 d

Remarks:

for respiration studies

Test temperature:

no data

Moisture:

no data for enzyme studies
60% for respiration studies

Details on test conditions:

TEST SYSTEM
- Testing facility: greenhouse
- Test container (type, material, size): 350 cm3 plastic pots
- Amount of soil: 250 g dry weight
- No. of replicates per concentration: 4
- No. of replicates per control: no 4
- No. of replicates per vehicle control: no data

SOIL INCUBATION
- Method: series of individual subsamples

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): 43.37 N; 2.82 W (Larrauri, Spain)
- History of site: no data
- Vegetation cover: natural grassland
- Treatments with pesticides or fertilizers: no data
- Accidental contamination: no data
- Depth of sampling: 20 cm
- Soil texture
- % sand: 15.7 (coarse); 36.3 (fine)
- % silt: 24.4
- % clay: 23.7
- Soil taxonomic classification: no data
- Soil classification system: no data
- pH (in water): 6.9
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight): no data
- Maximum water holding capacity (in % dry weigth): 35.5 (at 33 kPa)
- Cation exchange capacity (mmol/kg): no data
- Pretreatment of soil: air-dried for 24 h before sieving through a 2 mm sieve
- Storage (condition, duration): 4 degrees C
- Initial microbial biomass as % of total organic C: no data
-C/N: 13

DETAILS OF PREINCUBATION OF SOIL (if any): no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : dehydrogenase, acid phosphatase, ¿-glucosidase, and arylsulphatase; mineralizable nitrogen; substrate-induced respiration; metabolic quotients (qCO2; calculated as the ratio between the values of basal respiration and substrate-induced respiration); community level physiological profiles (assessed using Biolog EcoPlates)

VEHICLE CONTROL PERFORMED: no data

RANGE-FINDING STUDY
- Test concentrations: no data

Nominal and measured concentrations:

1.0 g/kg dw soil

Reference substance (positive control):

no

Key result

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

ca. 1 g/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

respiration rate

Details on results:

The addition of EDDS to the soil sample did not result in any statistically significant differences in the activity of the enzymes dehydrogenase, acid phosphatase, glucosidase and arylsulphatase (see Table 1). The potentially mineralizable nitrogen was unchanged compared to control samples, indicating that EDDS did not affect the biological activity of the soil (Table 1).

Although the test substance caused a small, but significant inhibition of soil basal respiration, it did not affect substrate-induced respiration. Due to the decrease in soil basal respiration, a significant decrease in the qCO2 was evident in the presence of the test substance (Figure 1; attached).

In the test for functional diversity of the soil microflora, EDDS caused a significant increase in species richness and Shannon's diversity (total number of species present), but showed no effects on Shannon's evenness or average well colour development (AWCD) (see Table 2).

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Statistically significant differences of P<0.05 or lower were reported

Table 1 - effect of EDDS on soil enzyme activities and potentially mineralizable nitrogen

	mg iodo-nitrotetrazolium formazane/kg dry wt soil/h   Dehydrogenase	mg p-nitrophenol/kg dry wt soil/h     Arylsulphatase  Glucosidase        Acid phosphatase			mg N-NH3/kg dry wt soil   Potentially mineralizable N
Control	448.3 ± 20.1	202.3 ± 16.8	227.8 ± 6.0	1070.0 ± 52.6	8.1 ± 0.3
EDDS	420.1 ± 56.8	204.5 ± 11.7	242.1 ± 3.5	1168.8 ± 64.1	9.0 ± 1.2

Table 2. Effect of EDDS on the AWCD and diversity indexes calculated from Biolog EcoPlate; absorbance data at an incubation time of 48 h

	AWCD	S	H	J
Control	0.49±0.08	15.67±1.20	2.64±0.0	0.67±0.00
EDDS	0.62±0.08	19.67±1.20	2.85±0.0	0.66±0.00

AWCD; average well colour development; S; richness; H; Shannon's diversity index; J: Shannon's evenness index

Validity criteria fulfilled:

yes

Conclusions:

In a study using several endpoints to measure toxicity to soil micro-organisms, EDDS at 1.0 g/kg dw soil for 3 days (considered the study NOEC) did not affect substrate-induced respiration (used as an indicator of potential biomass activity) or the activity of four enzymes (considered important for the breakdown of organic matter), although it did cause a significant inhibition of soil basal respiration.

Executive summary:

Ethylenediamine disuccinate (EDDS) was studied for its effects on soil micro-organisms (microbial biomass, activity and diversity and community structure), using soil samples from a natural grassland in Larrauri, Northern Spain.

After the addition of 1.0 g EDDS/kg dw soil, basal respiration (as an indicator of overall microbial activity) was measured and compared to substrate-induced respiration (as a measure of potentially active biomass) after the addition of glucose. Metabolic quotient (qCO2) was then calculated as the ratio of these two measurements to determine the effect of the test substance on the soil ecosystem. The activity of dehydrogenase, acid phosphatase, glucosidase, and arylsulphatase were analyzed as representatives of four different classes of enzymes important for the breakdown of organic matter. Potentially mineralizable nitrogen was also measured as an indicator of the biological soil activity. Finally, substrate profiles were assessed to determine the functional diversity of the soil microflora.

Basal respiration was reduced slightly (by about 10%), whilst substrate-induced respiration was unaffected by the addition of the test substance. The qCO2 was significantly reduced compared to the control value, indicating development of the ecosystem. There were no significant changes in enzyme activities or potentially mineralizable nitrogen when compared to the controls. Functional diversity was actually increased by the presence of EDDS.

In conclusion, 1 g EDDS/kg dw soil had no significant detrimental effect on the soil microflora; this value is considered the study 3-d NOEC.

[Information on EDDS is considered relevant to use for understanding the potential effects of trisodium EDDS on microbial toxicity, and is acceptable for using as read-across information.]

Description of key information

In a study using several endpoints to measure toxicity to soil micro-organisms, EDDS at 1.0 g/kg dw soil for 3 days (considered the study NOEC) did not affect substrate-induced respiration (used as an indicator of potential biomass activity) or the activity of four enzymes (considered important for the breakdown of organic matter), although it did cause a significant inhibition of soil basal respiration

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw

Additional information

Ethylenediamine disuccinate (EDDS) was studied for its effects on soil micro-organisms (microbial biomass, activity and diversity and community structure), using soil samples from a natural grassland in Larrauri, Northern Spain.

After the addition of 1.0 g EDDS/kg dw soil, basal respiration (as an indicator of overall microbial activity) was measured and compared to substrate-induced respiration (as a measure of potentially active biomass) after the addition of glucose. Metabolic quotient (qCO2) was then calculated as the ratio of these two measurements to determine the effect of the test substance on the soil ecosystem. The activity of dehydrogenase, acid phosphatase, glucosidase, and arylsulphatase were analyzed as representatives of four different classes of enzymes important for the breakdown of organic matter. Potentially mineralizable nitrogen was also measured as an indicator of the biological soil activity. Finally, substrate profiles were assessed to determine the functional diversity of the soil microflora.

Basal respiration was reduced slightly (by about 10%), whilst substrate-induced respiration was unaffected by the addition of the test substance. The qCO2 was significantly reduced compared to the control value, indicating development of the ecosystem. There were no significant changes in enzyme activities or potentially mineralizable nitrogen when compared to the controls. Functional diversity was actually increased by the presence of EDDS. In conclusion, 1 g EDDS/kg dw soil had no significant detrimental effect on the soil microflora; this value is considered the study 3 -d NOEC (Epelde et al. 2008).

[Information on EDDS is considered relevant to use for understanding the potential effects of trisodium EDDS on microbial toxicity, and is acceptable for using as read-across information.]