1. Distribution & Abundance of
Arsenic (As) in the Soils &
Sediments of Oʻahu, Hawaiʻi
Michael S. Tomlinson, Eric H. De Carlo,
Sara Thomas, & Laura E. deGelleke

2. Oʻahu, Hawaiʻi
Oʻahu
Hawaiʻi
Maui
Kauaʻi
Molokaʻi
Lānaʻi
Kahoʻolawe
Niʻihau
Ordnance Reef
Remedial
Investigation
Diamond Head
HonoluluBarbers
Point
Kaʻena Point
Kahuku Point
Makapuʻu
Point
Kailua
Kāneʻohe
Māmala Bay
Waiʻanae

3. Ordnance Reef RI –
Where did the As come from?
Nonmetric Multidimensional
Scaling (NMDS)

4. Anomalous [As] were seen in bed
sediments during USGS NAWQA Study
A = Agriculture
F = Forested
U = Urban
M = Mixed

5. Anthropogenic Trace Elements?
???
Arsenical Pesticides (e.g., NaAsO2),
Super-phosphate Fertilizers?

6. Principal Component Analysis

7. Anomalous
[As] were
reported in
soil data
compiled
by HIDoH

8. Arsenic Sources & Transfer

9. Oʻahu Relief, Isohyets, & UHM Samples

10. As & Former Sugarcane Land

11. As & Former/Current Pineapple Land

13. As in Waiakeakua Stream

14. Why is arsenic
in Waiakeakua
Stream?

15. 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)

16. 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

17. 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 …

18. Yes, arsenic occurs naturally in Arizona,
however, do not totally discount
anthropogenic sources
Photo taken in Flagstaff Sam’s Club

19. Mahalo nui loa! Questions?
Mālama i ko mākou ʻāina (Care for our land)