Product of Semi-Dry Absorption method of Flue Gas Desulphurization (SDA Product)

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14.03.2022 - 10.10.2022

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Version / remarks:

2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

1

Reference substance name:

SDA Product (desulphurization of exhaust gases by semi-dry absorption method from the coal fired power plants)

EC Number:

931-259-6

Molecular formula:

Not available

IUPAC Name:

SDA Product (desulphurization of exhaust gases by semi-dry absorption method from the coal fired power plants)

Test material form:

solid: bulk

Details on test material:

Boundary composition of the test material to cover all member of JS. The analysis of the test material will be performed prior the testing and the exact composition of the test material will be included in study reports:
Calcium sulfate (CAS 7778-18-9) 1-79%
Calcium sulfite hemihydrate (CAS 29501-28-8) 1-75%
Calcium carbonate (CAS 471-34-1) 1-45%
Calcium dihydroxide (CAS 1305-62-0) 0-35%
Calcium dichloride dihydrate (CAS 10035-04-8) 0-35%
Calcium difluoride (CAS 7789-75-5) 0-5%

Sampling and analysis

Analytical monitoring:

yes

Remarks:

The result of total nitrogen analysis in the test substance was provided by the Sponsor, Certificate of Analysis is attached as Appendix VII of study repor Nitrate content was analysed in soil extracts on days 0, 7 and 28 using a spectrophotometric assay.

Details on sampling:

Analysis of soil samples
The amount of nitrate formed in each treated and control replicate was determined at each sampling time, day 0, day 7 and day 28.

Nitrate was extracted from soil by shaking soil samples with 0.1 M potassium chloride solution in the 100 ml glass bottle at a ratio 1:5 (the fresh equivalent of 10 g dry soil to 50 ml 0.1M KCl). The soil suspensions were shaken at about 270 rpm for one hour. The extracts were purified, initially centrifuged at about 3500 rpm for 10 min and then filtered using a 0.45 µm membrane filter. Extraction blanks (extractant without soil) were included to check for impurities during the extraction procedure. The clear extracts were analysed immediately for nitrate concentration using UV-light spectrophotometric technique6, which is suitable for liquid samples with low content of dissolved organic compounds. Each extract was measured in two aliquots for each wavelength. Results are presented as the content of nitrogen in the form of nitrate (designated as NO3--N).

Calibration standards in the range 0.5 – 5.0 mg NO3--N /l were prepared according to the calculation sheet (Appendix VIII) to obtain the calibration curve. A portion of 20 ml of each calibration standard, blank or sample, was treated with 0.4 ml 1N HCl. The absorbance of the solution was recorded at two wavelengths; 220 nm (absorbance of nitrate ion) and 275 nm (interference control) using UV-VIS spectrophotometer (BK-S380, Biobase, CN). Soil extracts with detected absorbance out of the range of calibration standards were diluted by a suitable dilution factor, and the dilution was taken into account during the calculation of nitrate concentration.


- Sample storage conditions before analysis:
if standard soil is used, soils may be stored in the dark at 4 ± 2 °C for a maximum of three months. During the storage of soils, aerobic conditions must be ensured. If soils are collected from areas where they are frozen for at least three months per year, storage for six months at minus 18°C to minus 22°C can be considered. The microbial biomass of stored soils is measured prior to each experiment and the carbon in the biomass should be at least 1 % of the total soil organic carbon content.

Test substrate

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate:
A standard LUFA soil, type 2.3 was used for the experiment.
Supplier: LUFA Speyer, Speyer, Germany
Batch: Sp 2.3 0322

- sand content: sandy loam according to USDA (sand content 59.5±0.7%)
- pH (in 0.01M CaCl2) was 5.9±0.4
- organic carbon content: 0.64 ± 0.07%
- soil microbial carbon was 183±3.9 mg C/kg dry soil and represented 2.9% of total soil organic carbon.

The soil was amended with fine lucerne powder (100% Medicago sativa, supplier: ManuTea.cz, CZ) at the beginning of the preincubation.
Organic carbon content and total nitrogen were determined at the i2L Research Europe s.r.o. laboratory. Organic carbon analysed by loss on ignition was 46.4±0.1% C. Total nitrogen was measured in the solution after the Kjeldahl procedure (wet digestion of soil sample with a strong acid) using a standard ammonia ion selective electrode. Total nitrogen content was 3.78±0.02% N. The C/N ratio of lucerne powder was 12.3.
The lucerne-soil ratio used for the test was 5 g of lucerne per kilogram of soil (dry weight).





APPLICATION OF TEST SUBSTANCE TO SOIL
The soil is divided into 6 portions of equal weight. Five of the samples are mixed with the test substance, and the sixth sample is homogenized without the chemical.

Each sample will be divided into 3 replicates for both treatments and control. Care is taken to ensure homogenous distribution of the test substance in the treated soil samples. During mixing, compacting or balling of the soil are avoided.


VEHICLE:
- Chemical name of vehicle: deionised water

- Concentration of vehicle in test medium (stock solution and final test solution):
The moisture content of soil samples was maintained at about 55 % of the maximum water holding capacity of the soil. The moisture was checked gravimetrically twice a week, and deionised water was added as needed.

Test organisms

Test organisms (inoculum):

other: standard LUFA soil, type 2.3

Study design

Total exposure duration:

28 d

Test conditions

Test temperature:

mean 20.3°C (recommended 20+/-2°C)

Moisture:

55% (recommended 40-60 +/- 5%)

Organic carbon content (% dry weight):

0.64

Nitrogen content (% dry weight):

0.08

Details on test conditions:

TEST SYSTEM
- Testing facility: i2L Research Europe s.r.o., Lipová 1789/9, 370 05 České Budějovice, Czech Republic

- Test container (type, material, size): 100 ml reagent glass bottle with a cotton plug
- Amount of soil: contained an equivalent of 10 g dry soil
- No. of replicates per concentration: 3
- No. of replicates per control: 3

SOIL INCUBATION
- Method: series of individual subsamples
Soils were incubated as a series of individual soil subsamples under aerobic conditions.
Each treated and untreated bulk soil was divided into nine subsamples (three per each sampling time).
Each subsample was incubated in a 100 ml reagent glass bottle and contained an equivalent of 10 g dry soil.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
A standard LUFA soil, type 2.3 was used for the experiment. Supplier: LUFA Speyer, Speyer, Germany; Batch: Sp 2.3 0322
The soil had not been fertilised for more than 5 years prior to the collection.
The soil was identified as sandy loam according to USDA (sand content 59.5±0.7%);
it contained 0.64±0.07% organic carbon and 0.08±0.02% total nitrogen. The soil pH (in 0.01M CaCl2) was 5.9±0.4.

- Maximum water holding capacity (in % dry weigth): 35.4 +/- 2.3 %
- Cation exchange capacity: 5.7 +/- 0.5 meq/100g

- Pretreatment of soil:
The soil was moist sieved to a particle size less than or equal to 2 mm and stored indoors by supplier since the sampling day (18.1.2022).


- Storage (condition, duration): The soil was delivered in a fresh state and was stored field moist under datalogger surveillance before the start of the test: initially refrigerated (8.-15.2.2022, mean temperature 7.4°C, min.6.5°C, max. 8.8°C), then frozen for about three months due to delayed start of the experiment (15.2.-6.5.2022, mean temperature -23.4°C, min. -28.1°C, max. -14.8°C) and then allowed to adjust again to above-zero temperature (6.-27.5.2022, mean temperature 5.0°C, min. 4.1°C, max. 7.1°C; Appendix II of report)

- Initial microbial biomass as % of total organic C: Soil microbial carbon was 183±3.9 mg C/kg dry soil and represented 2.9% of total soil organic carbon.

DETAILS OF PREINCUBATION OF SOIL (if any):
Preincubation
The soil was allowed to adjust to similar conditions used in the test during the preincubation period which lasted for 17 days (27.5.-13.6.2022). The temperature during the preincubation was controlled by datalogger, mean temperature was 20.7°C, min. 19.3°C, max. 21.7°C. The soil moisture content of the soil during preincubation was adjusted to 55% of the maximum water holding capacity using deionised water and checked regularly (at least twice a week) to prevent water loss.
Substrate amendment
The soil was amended with fine lucerne powder (100% Medicago sativa, supplier: ManuTea.cz, CZ) at the beginning of the preincubation. Organic carbon content and total nitrogen were determined at the i2L Research Europe s.r.o. laboratory. Organic carbon analysed by loss on ignition4 was 46.4±0.1% C. Total nitrogen was measured in the solution after the Kjeldahl procedure5 (wet digestion of soil sample with a strong acid) using a standard ammonia ion selective electrode. Total nitrogen content was 3.78±0.02% N. The C/N ratio of lucerne powder was 12.3. For details on the procedures used for determination of organic carbon and nitrogen content in lucerne powder, see Appendices X and XI.
The lucerne-soil ratio used for the test was 5 g of lucerne per kilogram of soil (dry weight).


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : nitrate formation at 7 and 28d

Nominal and measured concentrations:

The nitrogen transformation test was conducted at five rates with the highest rate at 10 g of product/kg dry soil and a dilution step of 3 and untreated soil as control.

Results and discussion

Effect concentrations

Key result

Duration:

28 d

Dose descriptor:

EC50

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Remarks on result:

not determinable

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The variation in nitrate concentration less than +/-15%

Executive summary:

A laboratory study was conducted to investigate the long-term effects of SDA PRODUKT ODSÍŘENÍ T700, after a single exposure, on nitrogen transformation activity of soil microorganisms. The study followed the OECD Guideline for the testing of chemicals - Test No. 216: Soil Microorganisms: Nitrogen Transformation Test. The study was conducted at i2L Research Europe s.r.o. in České Budějovice, Czech Republic.

Standard soil was amended with lucerne powder as a source of energy and nutrients for the microbial community prior to the test. The test substance was applied to the soil at five rates with dilution step 3 with the highest rate at 10 g of product/kg dry soil. Soil with the test substance was incubated over 28 days at 20°C. Nitrate formation over the incubation period was determined. Nitrate content was analysed in soil extracts on days 0, 7 and 28 using a spectrophotometric assay.

None of the tested application rates of the product to the soil caused inhibition of nitrogen transformation compared to untreated control soil. Therefore, the effective concentration value EC₅₀ was not defined. On the opposite, each product addition caused stimulation of nitrate formation in soil over the 28-day incubation period; the higher the product addition in the tested range, the higher the stimulation. The highest application rate 10 g product/ kg dry soil increased nitrate formation by 95.2% as compared to untreated soil. Product addition also increased soil pH.