Oahu Soil & Sediment As

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    31-Jul-2015
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1. Distribution & Abundance of Arsenic (As) in the Soils & Sediments of Oahu, Hawaii Michael S. Tomlinson, Eric H. De Carlo, Sara Thomas, & Laura E. deGelleke 2. Oahu, Hawaii Oahu Hawaii Maui Kauai Molokai Lnai Kahoolawe Niihau Ordnance Reef Remedial Investigation Diamond Head HonoluluBarbers Point Kaena Point Kahuku Point Makapuu Point Kailua Kneohe Mmala Bay Waianae 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. Oahu Relief, Isohyets, & UHM Samples 10. As & Former Sugarcane Land 11. As & Former/Current Pineapple Land 12. As in Waiakeakua Stream 13. Why is arsenic in Waiakeakua Stream? 14. 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) 15. Conclusions As occurs in nearshore Oahu 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 16. 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 Oahu, 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 17. Yes, arsenic occurs naturally in Arizona, however, do not totally discount anthropogenic sources Photo taken in Flagstaff Sams Club 18. Mahalo nui loa! Questions? Mlama i ko mkou ina (Care for our land)