Nearshore Fate of Platinum Group Elements in Los Angeles Basin
Research Idea Scope
The extraordinary number of people and automobiles in metropolitan Los Angeles presents unique opportunities to assess anthropogenic contaminant loadings to the near-shore. Platinum group elements (PGEs: platinum, palladium, and rhodium) have been used in catalytic converters and air pollution control devices in automobiles for about 30 years. Particulate and soluble forms of these metals are transported through the environment, but their distribution and chemical forms are still poorly known. There is evidence, however, that these elements are increasing in the environment, that they are bio-accumulated, and that they pose environmental and health risks. The biological availability and marine environmental distribution of these metals are predominantly related to the chemical form and environmental conditions. As such, we propose to quantify for the first time the environmental loading of PGE in near-shore, dated sediment off LA using state-of-the-art analytical methods and on-shore roadside and fluvial sediments. This will yield a first-ever assessment of PGEs from a heavily urbanized metropolitan center in the U.S. and will provide a gauge of the environmental impact of a society almost wholly reliant on automobiles.
Samples for analyses of PGEs will be collected from appropriate sources in the LA basin and sinks in the offshore. Many cores and grab samples in the USGS repository can be used for analyses of offshore samples. In addition, we will coordinate with local public agencies for samples from the LA stormwater system. Depending on the concentrations of the PGEs, samples will be analyzed without pre-concentration using Induction Coupled Plasma Mass Spectrometry, or if necessary will be pre-concentrated using nickel-sulfide fire-assay techniques. In this latter case, relatively large quantities of sample will be required (15-25 g). We will develop an up-to-date literature review, collect suitable sediment samples for a reconnaissance study, establish geochronology for cores, and determine PGE and contaminant distributions for those samples, including temporal changes by sampling stratigraphically down cores.
Urgency and Payoff
Platinum group metals are an emerging chemical pollution concern. A calculation based on estimated PGE emissions from automobiles and FHWA highway statistics shows that there is up to half a metric ton of platinum that has been distributed over Los Angeles area roadways since the beginning of catalytic converter use in the mid-to-late 1970s. Results from this study can be used to generate a model of how metal-based aquatic contamination is distributed in the environment from roadways in the Los Angeles area, and thus generate a map of how roadways potentially impact the aquatic environment. In addition to providing information relevant to federal water quality and wetlands requirements applicable to the transportation community, data on the distribution of PGEs in the nearshore assists in Marine Spatial Planning efforts, consistent with our nation’s coastal and ocean research priorities as set forth by the U.S. White House Council on Environmental Quality.
Christopher Conaway, U.S. Geological Survey