Bioaccessible arsenic in soils of the island of Hawaii

Abstract

The body of work contained in this dissertation was designed to further our understanding of bioaccessible arsenic in iron-rich, volcanic-derived soils of the Island of Hawaii. The work is driven by three primary research objectives, corresponding to the three chapters of this dissertation. The first is the study of the areal and vertical extent, mobility and bioaccessibility of arsenic in soils of the eastern portion of the Island of Hawaii. Elevated soil arsenic was discovered in this region several years ago, the result of historical arsenical herbicide use on sugar cane. Understanding the extent of arsenic contamination, and its associated mobility and bioaccessibility was deemed critical to our understanding of potential human direct contact hazards and risks to aquifer water quality. The second objective was to understand how arsenic contaminant levels and various soil properties affect the degree of arsenic bioaccessibility. This type of research had previously been performed for various soil types in North America and Australia, but never for volcanic-derived Andisols prevalent on the Island of Hawaii. The final objective was to investigate in-situ remediation technologies for reducing arsenic bioaccessibility in soils, by way of iron amendments designed to bind arsenic, making it less bioaccessible.