DEVELOPMENT OF A METHOD FOR ASSESSING THE MOBILITY AND BIOAVAILABILITY OF METALLIC TRACE ELEMENTS IN SOILSPHASE 1: MTE BIOAVAILABILITY MEASUREMENT BY MEANS OF LABORATORY TOXICITY TESTS

Raynald Chassé 1, Gérald Côté 1 , Christian Bastien 1, Louise Deschênes 2 and Marcel Giroux 3

1 Centre d'expertise en analyse environnementale du Québec, ministère de l'Environnement du Québec , Canada; 2 Chaire industrielle CRSNG en assainissement et gestion des sites;3 Institut de recherche et de développement en agroenvironnement (IRDA)

INTRODUCTION

The development of new knowledge on the mobility and bioavailability of metallic trace elements (MTE) has a direct impact on the management of contaminated land and on the development of waste materials. The purpose of this project was to develop and test a method for assessing the mobility and bioavailability of MTEs in soils. Three approaches were tested in the first phase of the project. The first involved perfecting a chemical measure of MTE mobility based on a comparison of various documented analysis protocols. The results of this process were compared with on-site MTE flow measures. The other two approaches involved measuring MTE bioavailability using different trophic levels and different exposure paths.

RESULTS

CONCLUSION

MATERIALS AND METHODS

Two Soils : - Loam- Clay loam

One contaminant : Copper

Two levels of contamination : - 1500 mg/kg of Cu (dry weight)- 2500 mg/kg of Cu (dry weight)

Soil treatments: - liquid/solid copper sulphate contamination - sieved on 4 mm - dried at room temperature (10% humidity) - stored in plastic hermetic bag at 4°C - aquatic tests with water leachate of two soils

Three organisms : - Earthworm (Eisenia andrei)- Barley (Hordeum vulgare)- Daphnid (Daphnia magna)

Acute tests :- 14 days lethality test with earthworm- 48 hours lethality test with daphnid

Chronic tests :- 56 days reproduction test with earthworm- 72 hours avoidance test with earthworm- 10-21 days reproduction test with daphnid- 7-14 days germination and growth test with barley

Test development :

- study of the relative sensitivity of all tests- comparison between earthworm chronic tests (reproduction and avoidance) and earthworm acute test (lethality)- comparison of sensitivity of the toxic response for barley germination and growth after 7 days and 14 days exposure- comparison between daphnid chronic test (reproduction) and daphnid acute test (lethality)- comparison of sensitivity of the toxic response for daphnid reproduction test after 10 days and 21 days exposure

SOILS CHARACTERISTICS EARTHWORM TESTS

DAPHNID TESTS

BARLEY TESTS

DISCUSSION

Granulometry analysis, cationic exchange capacity and organic matter content in the two study soils

Soil

Loam

Clay loam

% Sand % Silt % Clay CECmeq/100g

% O.M.

26

11

47

43

27

46

16,53

24,59

4,3

6,95

IC50 wetweight(mg/kg)

963(916 - 1014)

stimulation of25%

Soil

Loam

Clay loam

EC50 germination7 d and 14 d

(mg/kg)

no effect

no effect

IC50 stemelongation

(mg/kg)

970 (910 -1041) (14d)877 (720 - 1027) (7d)

>137318% inh. in 1373 (14 d)37% inh. in 1373 (7 d)

IC50 rootselongation

(mg/kg)

333 (282 - 384) (14 d)478 (405 - 527) (7 d)

>137344% inh. in 1373 (14 d)

Stem length/roots length ration

2.02 at 430 mg/kg2.64 at 630 mg/kg

1.08 at 470 mg/kg1.56 at 690 mg/kg

IC50 wetweight(mg/kg)

1148(1080 - 1218)

stimulation of 3%

Germination and growth test results with barley (Hordeum vulgare), for 7 and 14 days Values in parenthesis are C.I. at 95%

Concentrations-responses curve for lethality test with earthworm in loam

OBJECTIVE

To compare different toxicity tests to develop a sensitive tool for the risk assessment of different type of soils and amendments (pig slurry, sewage sludge, biosolids, contaminated soils, ash).

Copper concentration

Soil

Loam

Clay loam

dissolved Cu(mg/L)

39

2.4

Total(mg/kg)

Exchangeable(mg/kg)

Soil at 2500mg/kg

2137(2080 - 2210)

2250(2070 - 2270)

Soil at 2500mg/kg

1300

1300

Soil at 1500mg/kg

1253(1220 - 1310)

1373(1290 - 1500)

Soil at 1500mg/kg

797(790 - 800)

783(780 - 7900)

Solubletotal Cu

(mg/L)

42

5

Total, exchangeable (Mehlich III) and soluble (leachate : 1:10 ratio) copper concentration for two soils Values are mean concentrations (min - max)

Soil at 1500 mg/kg

Lethality, avoidance and reproduction tests results with earthworm (Eisenia andrei) in loam and clay loam Values in parenthesis are C.I. at 95 %

Lethality

LC50 7 d(mg/kg)

IC25(mg/kg)

Avoidance Reproduction

LC50 14 d(mg/kg)

IC50(mg/kg)

Soil

1025 (829 - 1383)

> 225015% of mortality

in 2250

919 (765 - 1118)

> 225045% of

mortality in

100% in 85 mg/kg96% in 21 mg/kg

100% in 90 mg/kg60% in 22 mg/kg

14

ND

115

ND

Loam

Clay loam

Percentage

Soils characteristicsNominal and actual copper concentrations were comparable80% to 90% of copper was in exchangeable form (Mehlich III)Soluble copper concentration was low in leachateClay loam have a higher CEC and % of O.M.

Earthworm testsNo significant difference of sensitivity between 7 days and 14 days earthworm lethality testEarthworm chronic tests were very sensitive, more than acute testCritical value of reproduction and avoidance were very low, 10 time lower than LC50 Value of IC25 and level of significant avoidance corresponded to the mean Cu concentration in agricultural Québec soils, Canada

Barley testsNo significant difference of sensitivity between 7 days and 14 days barley germination and growth testRoots elongation was the most sensitive parameter in the germination and growth testStem length /roots length ratio was a good and sensitive parameter in the study of copper toxicity on barleyStem elongation, wet weight and dry weight were less sensitive to copper than roots elongationBarley germination and growth test was relatively sensitive to copper, particularly for roots

Daphnid testsLethality test was very sensitive to copperReproduction test results were very variables and not very accurates21 days reproduction test was more precise than 10 days reproduction testAcute test was more applicable than chronic test for this study with daphnid

Chronic earthworm tests (reproduction and avoidance) were the most sensitive tests for the study of copper toxicityCritical value of reproduction (IC25) and avoidance (100% avoidance) were in the same range of the mean copper concentration presented in agricultural Québec soilsRoots elongation was a very sensitive parameter for copperThe next stage of these project was the validation of our tool of risk assessment with different amended soils

10 d reproduction(percentage)

21 d reproduction(percentage)

Soil

Loam

Clay loam

48 h LC50 lethality(mg/L)

433 (386 - 487) *

920 (750 - 1090) *

100% inh (CL0,1 = 143)-25% inh (CL1 = 193)10% inh (CL5 = 252)

100% inh (CL0,1 = 15)32% inh (CL1 = 39)

100% mortality (CL5 = 90)

21,2% inh (CL0,1 = 143)62,5% inh (CL1 = 193)25,2% inh (CL5 = 252)

75% inh (CL0,1 = 15)37% inh (CL1 = 39)

100% mortality (CL5 = 90)

* I.C. at 95%

Lethality and reproduction test results with daphnid (Daphnia magna)

This study was financially supported by the Programme d'Aide à la Recherche et au Développement en Environnement (PARDE) of the ministère de l'Environnement du Québec

We wish to thank Renée Patenaude from CEAEQ for poster design

0

20

40

60

80

100

120

0 1 10 100 1000 10000

Copper concentration (mg/kg)

% o

f mor

talit

y

7 days

14 days

♦ ♦

IC25 Reproduction

100% avoidance

LC50 lethality

Mean Cu concentration in Québec agricultural soils :

19 mg/kg