Research Areas > Contaminants > Trace Metals Deposition

Project: Atmospheric Deposition of Trace Metals

Background and Objectives

Atmospheric deposition has been shown to be a large source of pollutants to water bodies such as the Great Lakes and the Chesapeake Bay. However, while southern California has a high potential for impacts owing to poor air quality, little attention has been focused on atmospheric pollution sources to coastal waters in this region. Despite stringent controls on point source pollutant discharges, more than three dozen water bodies in this region fail to meet water quality standards for trace metals, indicating the need to investigate nonpoint pollution sources such as atmospheric deposition.

The goal of this study was to provide empirical data on dry deposition rates of trace metals in coastal areas of southern California.

Status

This study was initiated in 2002 and completed in 2007.

Methods

The focus of these studies was on chromium, copper, lead, nickel and zinc. A number of different techniques were used to estimate atmospheric dry deposition rates of these metals, including

• Direct measurements of dry deposition to surrogate surfaces.
• Inferential method (size segregated atmospheric concentration measurements modeled particle deposition velocities).

Findings

• Dry deposition to watershed land surfaces is substantial in coastal waterbodies of southern California, representing a potentially large source of trace metals to stormwater runoff. Atmospheric deposition potentially contributes as much as 50-100% of trace metals to stormwater runoff in highly impervious, urban catchments.

• Proximity to urban areas, and in particular busy roadways, significantly increases dry deposition rates.

• Along the coast, atmospheric deposition of lead has dramatically decreased over the past thirty years. Over the same time period, atmospheric deposition of copper and zinc have increased along the coast near the Los Angeles Harbor and the San Diego Bay.

Partners

University of California, Los Angeles, Institute of the Environment