Curt D. Storlazzi
Renee K. Takesue
2019
<p><span>Runoff of sediment and other contaminants from developed watersheds threatens <a title="Learn more about Coastal Ecosystem" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coastal-ecosystem" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coastal-ecosystem">coastal ecosystems</a> and services. A sediment geochemical sourcing study was undertaken on a sediment-impacted <a title="Learn more about coral reef" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coral-reef" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coral-reef">coral reef</a> flat to identify terrestrial sediment sources and how these changed over time. Geochemical signatures were identified for watershed soils that formed on Hawaiian basaltic and alkalic lavas using relatively immobile compatible (Ni, Sc) and incompatible (Nb, <a title="Learn more about rare earth elements" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/rare-earth-elements" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/rare-earth-elements">REE</a>, Th) elements quantified by ICP-MS in total decompositions of the fine fraction of surface soils. Some soils also contained ash from late-erupting <a title="Learn more about cones (volcanoes)" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cones-volcanoes" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cones-volcanoes">cinder cones</a>that added alkalic geochemical signatures, resulting in distinctive mixed signatures near these geologic features. Sediment was collected in Pelekane Bay using <a title="Learn more about sediment trap" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/sediment-trap" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/sediment-trap">sediment traps</a>during winter 2010–2011 and a <a title="Learn more about sediment core" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/sediment-core" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/sediment-core">sediment core</a> in order to geochemically source runoff entering the bay. Geochemical signatures in trapped sediment showed that runoff predominantly originated from the lower watershed along a highway corridor rather than from the upper watershed or areas with alkalic lavas. Soil in the highway corridor also contained Zn above levels of concern for <a title="Learn more about aquatic organism" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/aquatic-organism" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/aquatic-organism">aquatic organisms</a> and anthropogenic Pb, indications that runoff <a title="Learn more about control measure" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/control-measure" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/control-measure">control measures</a> could reduce the exposure of the reef community to potentially <a title="Learn more about toxic metal" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/toxic-metal" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/toxic-metal">toxic metals</a> and other road-associated contaminants. The upper portion of a 60-yr long sediment record from Pelekane Bay was disturbed by tsunamigenic waves from the Tohoku <a title="Learn more about Earthquake" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/earthquake" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/earthquake">earthquake</a>, and the remainder was likely subject to mixing by winter waves that averaged out geochemical variations. On average, watershed regions with basaltic soils were the predominant source of runoff to the bay over the past 60 years. By linking sediment runoff to geographic regions or features in watersheds, geochemical sourcing can provide insights that allow resource managers to direct runoff mitigation and </span><a title="Learn more about Soil Conservation" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/soil-conservation" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/soil-conservation">soil conservation</a><span> efforts to areas where they will be most effective.</span></p>
application/pdf
10.1016/j.scitotenv.2018.08.282
en
Elsevier
Geochemical sourcing of runoff from a young volcanic watershed to an impacted coral reef in Pelekane Bay, Hawaii
article