In the Metals Prep/Analysis lab, scientists analyze water, wastewater, soil, sediment and sludge for metals. While some metals are essential nutrients and are acceptable at low concentrations (e.g., calcium, magnesium and zinc), they may be harmful at high concentrations. Other metals (e.g., arsenic, lead and mercury) are toxic even at low concentrations. Results of the analyses are compared to regulatory limits set by the Environmental Protection Agency, the Washington State Department of Ecology, and the City of Tacoma. By studying these metals, sources of contaminants can be identified, contained and monitored to prevent their impact on the environment.

In this lab:

• Samples are "digested" for analysis. Acid, heat and pressure are added to a sample until the metals are dissolved and can be analyzed.
• Concentrations of metals in soil and water are determined and evaluated to see if they exceed regulatory levels.
• Specific metals in samples are identified to trace the origin of pollutants, including “nonpoint” sources of metals, such as automobiles, household chemicals or airborne dust.  

For example:

In 2006, elevated mercury concentrations were detected in downtown Tacoma stormwater outfalls (discharge points). By doing source tracking from the original outfall and working upstream, a one-block area was identified that contained elevated mercury concentrations in the stormwater runoff.  After cleaning all of the catch basins and storm sewer pipes in the one-block area, the mercury concentrations dropped significantly. City scientists speculated that sometime last century, when mercury thermometer use was common, one had been dropped into a catch basin. The thermometer then slowly released mercury during each storm event.