1. 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
2. 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
4. 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)?
5. 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
6. 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
11. 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
12. 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
13. 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