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Ecotoxicological information

Toxicity to terrestrial plants

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Administrative data

Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2006-07-11 - 2006-08-01
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions

Data source

Reference
Reference Type:
secondary source
Title:
Unnamed
Year:
2006
Report date:
2006

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: Test for Measuring Emergence and Growth of Terrestrial Plants Exposed to Contaminants in Soil. Report EPS 1/RM/45, February 2005, Environment Canada
Principles of method if other than guideline:
Study conducted according to Environment Canada test method.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
Reference substance 001

Sampling and analysis

Analytical monitoring:
yes

Test substrate

Vehicle:
no
Details on preparation and application of test substrate:
The artificial control soil (AS) was formulated in the laboratory by mixing the ingredients in their dry form, then gradually hydrating with deionized water, and mixing further until the soil was visibly uniform in colour and texture. The ingredients of AS were 70% silica sand (No. 200, Barco 71; Barnes Environmental International, Waterdown, ON), 20% kaolinite clay (Tuckers Pottery Supplies, Richmond Hill, ON), 10% Sphagnum peat (Horticulture Department, University of Guelph, Guelph, ON), and calcium carbonate (10-30 g per 1 kg peat). A 12 kg batch of AS was formulated on a dry weight basis by adding 7 kg of sand, 2 kg of kaolinite clay, 1 kg of sieved (2 mm) peat, approximately 30 g of CaCO3 (sieved), and 2 L of deionized water. The amount of calcium carbonate required to achieve a soil pH in the range of 6-7.5, depended on the nature (i.e., acidity) of the Sphagnum peat and the silica sand. Each time a new bag of either of these ingredients was used, it was necessary to adjust the amount of CaCO3 used in each batch of formulated soil.
Artificial soil is low in the nutrients required by some plants for growth. For testing purposes, plant test units containing artificial soil are formulated and irrigated with a dilute nutrient solution. The nutrient solution used is a 20-8-20 (N:P:K) formulation (Plant Products Company Ltd., 314 Orenda Road, Brampton, ON L6T 1G1) recommended by the Department of Plant Agriculture, University of Guelph. At the Stantec laboratory, a nutrient solution is made out of the powdered formulation to a concentration of 1 g/L. When preparing artificial soil for testing on Day 0 the soil is hydrated to a standard moisture content with nutrient solution at 1 g/L. For irrigating the plant tests (Day 7 – end of test), a half-strength nutrient solution is used (0.5 g/L) and the artificial soil treatments are misted with nutrient solution when necessary.

Test organisms

open allclose all
Species:
other: Medicago sativa
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
Alfalfa
Species:
Hordeum vulgare
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
Barley
Species:
other: Elymus lanceolatus
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
Northern wheatgrass

Study design

Test type:
other: early seedling emergence and growth test
Study type:
laboratory study
Substrate type:
artificial soil
Limit test:
no
Total exposure duration:
14 d
Remarks:
21 d

Test conditions

Test temperature:
24/16 ± 3°C (day/night)
pH:
Soil pH ranged from 6.19 to 7.64 for the beginning of all tests and from 3.92 to 7.40 for the end of all tests.
Moisture:
Soil moisture content of all treatments in all tests was independent of DEG concentrations and ranged from 59 to116% of the soil water holding capacity (WHC) for the beginning of all tests and from 44 to 91% of the soil WHC for the end of the invertebrate tests.
Details on test conditions:
Test unit (chamber): 1-L polypropylene container
Amount of soil: 500 g wet wt.
Photoperiod (h): 16 light : 8 dark
Lighting (Type & Intensity): Full spectrum Durotest or Vita Lights; 200-400 μmoles/(m2·s)
Number of replicate test units per treatment: 6-3
Number of organisms per test unit: 10-5
Nominal and measured concentrations:
0, 200, 400, 800, 1600, 3200, 6400, 9600, 12800, 25600 mg/kg
The recovery of DEG from the beginning of the range-finding tests was good and ranged from 75 to 90%. DEG recovery on Day 0 of the northern
wheatgrass test was similar among all but the lowest (200 mg/kg) treatments and ranged from 85 to 102%. The recovery in the lowest treatment was below the detection limit. There was evidence of loss of DEG from soil over time; measurable concentrations of DEG were only detected in the highest concentration (25600 mg/kg) at Days 7 and 21 of the test. In addition, the % DEG recovery in these concentrations also decreased over time with 102, 74 and 63% recovery at Days 0, 7 and 21, respectively.

Results and discussion

Effect concentrationsopen allclose all
Species:
other: Elymus lanceolatus
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
20 077 mg/kg soil dw
Basis for effect:
seedling emergence
Key result
Species:
other: Elymus lanceolatus
Duration:
21 d
Dose descriptor:
other: IC50
Effect conc.:
1 471 mg/kg soil dw
Basis for effect:
other: shoot dry mass
Species:
other: Elymus lanceolatus
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
818 mg/kg soil dw
Basis for effect:
growth
Remarks:
shoot dry mass
Species:
other: Medicago sativa
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
18 102 mg/kg soil dw
Basis for effect:
seedling emergence
Species:
other: Medicago sativa
Duration:
21 d
Dose descriptor:
other: IC50
Effect conc.:
3 041 mg/kg soil dw
Basis for effect:
growth
Remarks:
root dry mass
Species:
other: Medicago sativa
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
1 297 mg/kg soil dw
Basis for effect:
growth
Remarks:
root dry mass
Species:
Hordeum vulgare
Duration:
14 d
Dose descriptor:
other: IC50
Effect conc.:
1 779 mg/kg soil dw
Basis for effect:
growth
Remarks:
shoot dry mass
Species:
Hordeum vulgare
Duration:
14 d
Dose descriptor:
other: IC25
Effect conc.:
419 mg/kg soil dw
Basis for effect:
growth
Remarks:
shoot dry mass
Details on results:
Alfalfa:
Alfalfa emergence was affected adversely following exposure to DEG at the highest concentration only resulting in an EC50 of 18,102 mg/kg. Seedling growth responded to DEG exposure in a concentration-dependent manner generally following a sigmoidal curve. It should be noted, however, that there was an slight increase in root dry mass at two intermediate concentrations (800 and 1600 mg/kg) relative to root mass in the control and lowest two DEG treatments. This response was also observed in the shoot mass data set but it was not as pronounced. Because of the unusual response pattern, no linear or non-linear regression curves could be fitted to the root mass data set. Therefore, in order to estimate an IC50 and IC25 from the root mass data set, regression procedures were applied to the data with the control and 200 and 400 mg/kg data removed. The ICps for the other growth metrics were estimated with full data sets. IC50s were very similar among endpoints and ranged from 3041 to 3254 mg/kg for root and shoot dry mass, respectively.
Barley:
There was no effect on seedling emergence of exposure of barley to DEG. Seedling growth responded to DEG exposure in a concentration-dependent manner and the concentrationresponse pattern, in general, followed a sigmoidal toxicity curve. The IC50s ranged from 1779 to 17685 mg/kg for shoot dry mass and shoot length endpoints, respectively.
Northern wheatgrass:
Northern wheatgrass emergence was adversely affected following exposure to DEG resulting in an EC50 of 20,077 mg/kg. Seedling growth responded to DEG exposure in a concentrationdependent manner and the concentration-response pattern in general followed a sigmoidal toxicity curve. The IC50s ranged from 1471 to 3828 mg/kg for shoot dry mass and shoot length endpoints, respectively.

Applicant's summary and conclusion