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King County Freshwater Trace Metal Monitoring Program

The measurement of trace metals in the sediments and surface waters is a useful indicator of the health of the waters and the effectiveness of pollution prevention efforts. Water samples were collected from a portion of the King County streams and analyzed for trace metals quarterly through 2008 ( King County Sampling and Analysis Plan Ambient Streams and Rivers, 2002 ). Trace metals (total and dissolved) that were analyzed on a routine basis are listed in Table 1. Metals were eliminated from the program in 2009.

Metals analyzed as well as the analytical methods used have changed over time. The analytical method changed as technological improvements were made at the King County Environmental Laboratory resulting in a decrease in the minimum detection limit as shown in Table 2. For most metals, only the most recent period, since the implementation of the ICP-MS method and the lowered detection limits, can be used to determine whether the trace metal concentrations meet State standards.

Table 1. Metals Analyzed in Quarterly Samples from Ambient Stream Sites.


Metal Total Dissolved
Aluminum ICP-MS
Arsenic ICP-MS
Barium ICP-MS ICP-MS
Beryllium ICP-MS
Calcium ICP-MS
Cadmium ICP-MS
Chromium ICP-MS
Cobalt ICP-MS
Copper ICP-MS
Hardness Calculated ICPMS
Iron ICP-MS
Lead ICP-MS
Molybdenum ICP-MS ICP-MS
Mercury CVAA-UL CVAF-UL
Nickel ICP-MS
Selenium, Total, ICP-MS
Thallium ICP-MS
Vanadium ICP-MS ICP-MS
Zinc ICP-MS ICP-MS

Table 2. Period of Record and Limits of Detection for Various Trace Metals and Analytical Methods. (ug/L). Click to enlarge

Why do we sample metals?

Excess metal levels in surface water can be detrimental to aquatic organisms and may pose a health risk to humans. Living organisms require trace amounts of some metals, including cobalt, copper, iron, manganese, molybdenum, vanadium, strontium, and zinc. Metals that are non-essential to living organisms such as lead, cadmium, mercury, arsenic, barium, and chromium, may pose great health risks.

Risks to Aquatic Organisms –

Slightly elevated metal levels in natural waters may cause sublethal effects in aquatic organisms such as a change in tissues; suppression of growth and development; poor swimming performance; changes in circulation; change in enzyme activity and blood chemistry; and changes in reproduction.

Phytoplankton and zooplankton often assimilate available metals quickly because of their high surface area to volume ratio. The ability of fish and invertebrates to adsorb metals is largely dependent on the physical and chemical characteristics of the metal.

Risks to Human Health –

The following list outlines the health risks associated with these non-essential metals.

  • Arsenic: Arsenic ingestion can cause severe toxicity through ingestion of contaminated food and water. Ingestion causes vomiting, diarrhea, and cardiac abnormalities (Viessman and Hammer, 1985).
  • Cadmium: Cadmium may interfere with the metallothionein's ability to regulate zinc and copper concentrations in the body. Metallothionein is a protein that binds to excess essential metals to render them unavailable. When cadmium induces metallothionein activity; it binds to copper and zinc, disrupting the homeostasis levels (Kennish, 1992).
  • Chromium: The presence of abundant chromium anions in the water is generally a result of industrial waste. The chronic adverse health effects are respiratory and dermatologic (Viessman and Hammer, 1985).
  • Lead: Because of size and charge similarities, lead can substitute for calcium and become incorporated into bone. Children are especially susceptible to lead because developing skeletal systems require substantial calcium. Lead that is stored in bone is not harmful, but if high levels of calcium are ingested later, the lead in the bone may be replaced by calcium and mobilized. Once free in the system, lead may cause nephrotoxicity, neurotoxicity, and hypertension.
  • Mercury: Mercury poses a great risk to humans, especially in the form of methylmercury. When mercury enters water it is often transformed by microorganisms into the toxic methyl-mercury form. Chronic poisoning is usually a result of industrial exposure or a diet consisting of contaminated fish. Chronic poisoning may cause liver damage, neural damage, and teratogenesis (USEPA, 1987).