Assessment of Trace Element Contamination in Streambed Sediment and Spatial Associations in Palolo Valley Watershed, Honolulu, Oʻahu, Hawaiʻi

Abstract

Trace elements in streambed sediment (<63 micrometers) of Palolo, Pukele, and Waiomao Streams (Palolo Valley Watershed, Honolulu, Hawaii) were investigated. Based on weak hydrochloric acid leaching (0.5 molarity), total digestions, sequential extractions, concentration enrichment ratios, sediment quality guideline comparisons, and national stream comparisons, there was significant lead contamination in Palolo Stream and some concern for copper, nickel, and zinc. Pukele Stream had intermediate trace element contamination, while Waiomao Stream was largely uncontaminated. Palolo Stream had significantly greater concentrations of trace elements than Pukele Stream, and both streams were significantly greater than Waiomao Stream. Since sediment in Palolo Steam was significantly contaminated with trace elements, the biological integrity of Palolo Stream and downstream systems could be impaired. There were great differences in urbanization related to population, storm drains, streets, and vehicle numbers in the sub-basins. These land use characteristics could contribute to the observed differences among trace elements concentrations in streambed sediment.