oahu soil & sediment as
TRANSCRIPT
Distribution & Abundance of Arsenic (As) in the Soils &
Sediments of Oʻahu, Hawaiʻi
Michael S. Tomlinson, Eric H. De Carlo, Sara Thomas, & Laura E. deGelleke
Oʻahu, Hawaiʻi
Oʻahu
Hawaiʻi
Maui
Kauaʻi
Molokaʻi
Lānaʻi
Kahoʻolawe
Niʻihau
Ordnance Reef Remedial Investigation
Diamond Head
Honolulu Barbers Point
Kaʻena Point
Kahuku Point
Makapuʻu Point
Kailua
Kāneʻohe
Māmala Bay
Waiʻanae
Anomalous [As] were seen in bed sediments during USGS NAWQA Study
A = Agriculture
F = Forested
U = Urban
M = Mixed
Where does the arsenic come from?
Possibly iron & zinc micronutrient fertilizer from silver mine tailings used by nurseries to green-up plants (Human Health Risk Assessment for Long-term Residential Use of Ironite® Lawn and Garden Nutrient Supplement - ADEQ, 1998)
Conclusions
• As occurs in nearshore Oʻahu sediments
• NMDS indicates a loose association with terrestrial elements (probably from runoff)
• As occurs in some NAWQA stream sediments associated with agriculture
• PCA of NAWQA sediments indicate a loose association with petrogenic elements but not anthropogenic elements
• HIDoH data show elevated [As] but the distribution is spotty
Conclusions (continued)
• Some As may be associated with past sugarcane and/or pineapple agriculture (arsenical pesticides – ceased late 1940s, super-phosphate fertilizers, etc.)
• The highest [As] on Oʻahu, however, are found in mixed land use/forested areas
• Arsenical pesticides & micronutrient fertilizers (e.g., Ironite®) used in nurseries may explain some As
• And, finally …
Yes, arsenic occurs naturally in Arizona, however, do not totally discount
anthropogenic sources
Photo taken in Flagstaff Sam’s Club