Eisenia fetida as a bioindicator of arsenic rich soils in Hawaii

Russell Auwae

Sponsors: Dr. Theodore Radovich and Dr. Nguyen HueSponsors: Dr. Theodore Radovich and Dr. Nguyen Hue

University of Hawaii at Manoa, Department of Tropical Plant and Soil Sciences (TPSS)

IS 489: Environmental Practicum

12/08/10

Background: Arsenic Accumulation

High concentrations of arsenic on abandoned sugarcane lands

– Arsenic-based herbicides used for weed control during the

1920s to 1950s

– Converted to residential and commercial areas

Adverse Health Effects:Adverse Health Effects:

– Skin lesions and hardenings

– Cancers

– Neurological disorders

Study Site: Kea’au, HI

-Proposed hotel site

-New housing

-New schools

Questions

Bioaccessibility and Chemical Behavior:

– What is the bioaccessible amount of arsenic in the soils?

• Bioaccessible- amount available for absorption by the body

– Does arsenic affect earthworm (Eisenia fetida)

performance (mortality/survival/growth)?performance (mortality/survival/growth)?

Hypothesis

• There will be higher bioaccessible arsenic in Kea’au soil than

Waimanalo soil.

• Earthworm performance will decrease with increasing

amounts of arsenic.

Objectives

Measure the:

• Performance (mortality/survival/growth) rate

• Bioaccessible arsenic in the soils

Setup of Treatments

• 600g of soil per pot:

– Treatment 1: 100% Waimanalo

– Treatment 2: 75% Waimanalo + 25% Kea’au

– Treatment 3: 50/50 Waimanalo + Kea’au

– Treatment 4: 75% Kea’au + 25% Waimanalo – Treatment 4: 75% Kea’au + 25% Waimanalo

– Treatment 5: 100% Kea’au

• Three replicates per treatment type

• Eight earthworms per pot

Pictures

Lab Analysis

• Weighed with a balance

• Measured bioaccessible arsenic with an inductively coupled

plasma spectrometer (ICP)

Results

Number of Trials Waimanalo (g) Kea'au (g) Estimated Total As (mg/kg) Bioaccessible As (mg/kg) Initial EW (g) 2 wks EW (g) 4 wks EW (g) 6 wks EW (g)

1 600 0 20 1.45 2.1 2.2 3.4 3.4

2 450 150 90 3.04 2.2 3.0 4.4 4.2

3 300 300 160 5.87 2.3 4.0 5.2 5.1

4 150 450 230 6.33 2.0 4.5 5.4 5.4

5 0 600 300 6.86 2.1 4.4 5.4 6.0

6 600 0 20 1.13 1.6 2.5 3.9 4.46 600 0 20 1.13 1.6 2.5 3.9 4.4

7 450 150 90 2.34 1.9 4.0 5.8 6.0

8 300 300 160 4.70 2.4 5.4 6.1 5.8

9 150 450 230 4.95 1.7 3.5 5.0 4.9

10 0 600 300 8.17 1.7 3.6 4.6 4.2

11 600 0 20 1.22 1.6 4.4 5.5 5.1

12 450 150 90 3.53 1.4 3.7 4.5 4.4

13 300 300 160 5.64 1.9 4.6 5.6 4.9

14 150 450 230 6.76 1.7 4.4 5.4 5.0

15 0 600 300 9.44 1.8 4.9 6.1 6.1

ResultsR

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Bioaccessible As (mg/kg)

Caveat

• Bioaccessible arsenic exceeds daily exposure of 0.004-0.007 mg/kg per day

• Serious threat to:

– Residents

– Workers

– Schools– Schools

– Civic centers

• Solutions:

– Wear protective gear (gloves, long-sleeve clothing, safety glasses, or dust masks)

– Plant grass over exposed soil

– Keep children from playing in contaminated soil

– Wash hands and face after working or playing

– Wash fruits and vegetables

Conclusion

• Bioaccessible arsenic ranged from 1.13-9.44 mg/kg

• Growth of Eisenia fetida peaked at about 2 mg/kg of

bioaccessible arsenic

• Evidence of a hormetic effect

– Favorable biological responses to low doses of a toxin or – Favorable biological responses to low doses of a toxin or

stressor

Further Research

• Do endogeic and/or anecic earthworms respond differently to

arsenic contaminated soils?

• Does different arsenic concentrations affect the earthworm

reproduction?

• How much arsenic accumulated in the earthworms? • How much arsenic accumulated in the earthworms?

• Economical ways of soil remediation

– Excavation

– Phytoremediation

Acknowledgements

• Dr. Theodore Radovich

• Dr. Nguyen Hue

• Dr. John Cusick