VALIDATION OF A TWO-PHASE BIOASSAY FOR RISK ASSESSMENT OF CONTAMINATED SOILS

Transcription

1 1 VALIDATION OF A TWO-PHASE BIOASSAY FOR RISK ASSESSMENT OF CONTAMINATED SOILS By: Mariella Siña Supervisors: Staffan Lundstedt Umeå university Torbjörn Johnson Pelagia miljökonsult AB

2 2 Aim Evaluate a Two-phase version of the Daphnia magna immobilization test. Correlation response- contaminant levels Response compared to the standard test (Is the toxicity particle bound or is it water soluble?) Is the toxicity due to the particles themselves or to lipophilic contaminants?

3 3 The Daphnia magna acute toxicity test (ISO 6341) Standard method for toxicity testing of water samples and aqueous leachates of the soil Endpoint: mobility inhibition after 24 hours (EC50) Daphnids hrs old No feeding during the test

4 4 The two-phase version Soil particles are suspended in a water based medium Daphnia magna feeds unselectively on suspended particles over 0.45 μm up to 50 μm When lacking of food they stir the sediments. Daphnia keeps sediments in its gut until new food is provided

5 5 Six soils samples from a wood preservation site Soil sample code Sum 16 US EPA PAHs (mg/kg)*

6 6 Soil Sample Chemical analysis PAHs, oxy-pahs and azaarenes Metals Acute ecotoxicity tests Standard test Two-phase test Tests after Extraction with cyclohexane Aqueous leachate Washed out particles Reapplied soil Extracted particles

7 Chemical Analysis Two-phase test Two-phase test vs. Standard test Tests after Extraction with Cyclohexane 7

8 8 Chemical Analysis Sample Org matter % d.w. Sum 16 US EPA PAHs (mg/kg) Sum oxy-pahs (mg/kg) Sum N PAHs (mg/kg) Sum metals (ug/g dw) The samples represent a wide range of PAHs

9 Total Sum of PAHs (mg/kg) 9 Two-phase Tests Correlation Total Sum of PAHs and EC50 Sample EC50 (g/ml) 1 nd-no toxicity soil sample EC50 (g/ml) EC50 has a moderate negative correlation with the total sum of PAHs and oxy-pahs in the soil

10 Higher negative correlation 2,3,5-Trimethylnaphthalene 1-Methylphenanthrene 2,6-Dimethylnaphthalene Pyrene 1-Methylnaphthalene Fluoranthene Chrysene Biphenyl Acenaphthene Fluorene Phenanthrene Benzo(b)fluoranthene Benzo(a)anthracene Benzo(e)pyrene 2-Methylnaphthalene Acenaphthylene Benzo(k)fluoranthene Perylene Benzo(a)pyrene Dibenz(a,h)anthracene Indeno(c,d)pyrene Benzo(g,h,i)perylene Anthracene Naphthalene Benzofluorenone Cyclopentaphenanthrenone Benzanthrone Benzanthraquinone 2-Methylanthraquinone Naphthacenequinone Benzo[cd]pyrenone 9-Fluorenone 9,10-Anthraquinone 1-Indanone Quinoline Benzo[h]quinoline Carbazole Org content % Zn Cd As Cu Pb Cr 10 Multivariate Analysis PAHs in red Oxy-PAHs in blue Azaarenes in green OM in black Metals in orange SIMCA-P :52:07 (UTC+1) Toxic potential increases

11 % immob. D. magna 11 Two-phase test vs. Standard Test Is the toxicity drawn with the aqueous leachate or stays particle bound? Comparison of responses : two-phase test vs standard test 3 6 Daphnia magna shows no sensitivity to the aqueous leachates two-phase test standard test resuspended particles test

12 12 Toxicity tests after Extraction with Cyclohexane Two-phase test vs Extracted soil test Sample Conc. tested (g/ml) % immobilized daphnids Two-phase test Extracted soil test Soil Soil Is the toxicity due to the particles themselves or to the lipophilic contaminants? The extracted soil exerted no toxicity on Daphnia magna.

13 13 Toxicity tests after Extraction with Cyclohexane Two-phase test vs Reapplied soil test Sample Two-phase test EC50 (g/ml) Reapplied soil EC50 (g/ml) The toxicity reappeared and even increased after reapplication of the extract on the soil.

14 14 CONCLUSIONS EC50 in the two-phase test had a moderate negative correlation with the total amount of PAHs and oxy- PAHs but no correlation with the amount of metals. The multivariate analysis shows EC50 is more negatively correlated with some Oxy-PAHs and azaarenes Daphnia magna showed no sensitivity to the aqueous leachates.

15 15 CONCLUSIONS After extracting lipophilic contaminants with cyclohexane, the extracted particles exerted no toxicity on Daphnia magna, but with the reapplied soil the toxic response was completely recovered. The two-phase variant of the acute toxicity test with Daphnia magna truly exhibits the toxicity of particle bound contaminants.

16 16 Advantages Water leachates underestimate the toxicity of lipophilic compounds Tests of soil suspensions could be a useful compromise in the adaptation of standardized aquatic bioassays Disadvantages The dilution method of the soil suspensions may cause the coarse particles to be left in the bottom Daphnia magna may be less relevant as a representative soil organism Relatively cost effective method

17 17 Recommendations for the use of the method Subsampling and dilution of the soil suspensions should be optimized and standardized. Develop the guidelines on how to interpret the two-phase test results in risk assessments.

18 THANKS! 18