Metals.....

WHAT IS IT?

     Metals are natural and normally present in trace amounts in rivers. Cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), and zinc (Zn) are all elements in the periodic table.

WHY IS IT IMPORTANT?

     Some elements are necessary for normal bodily functions of aquatic organisms. Thus some are needed in the waterway. When the amount of these elements is elevated above the necessary amount, however, they can become harmful. Excess amounts of metals can harm aquatic life by stunting organisms' growth, making them infertile and sometimes killing them outright. More than 1,300 miles of streams and rivers in CO have been damaged by acidic drainage from abandoned mining activities.

For example, literature states that for trout:

     1. Cadmium is nonessential and becomes toxic to trout at concentrations around 1.4 parts per billion.

     2. Copper is essential to aquatic organisms, it is used in cellular metabolism and oxygen transport and is an important part of some enzymes. But too much copper can kill: Trout die when concentrations reach about 20 parts per billion.

     3. Iron is necessary in small amounts, and toxic at levels above a thousand or so parts per billion. The metal is usually indirectly toxic before directly toxic; iron precipitate covers fish spawning habitat and eggs as well as macroinvertebrate habitat.

     4. Lead is nonessential becomes toxic in the 10 to 100 parts per billion range. There is not much research regarding lead toxicity.

     5. Zinc is essential for cell differentiation and growth. It is also used in enzymes and DNA, but becomes toxic at about 50 to 200 parts per billion.

WHAT INFLUENCES IT?

Trace amounts of metals enter waterways through natural rock weathering, but elevated metals enter streams and rivers through:

     1. Natural Sources: Geology and soils naturally can naturally contain elevated levels of certain metals. Hot springs can often bring elevated levels of elements to the surface as well (like sulfur).

     2. Abandoned mines, tailing and waste piles: Mining brings rocks and minerals from deep within the Earth to its surface, and often bringing elevated metals concentrations with it. Once exposed, these rocks and minerals react with rainwater and groundwater and run into local rivers and streams, carrying elevated loads of metal.

     3. Industry by-products: Runoff from industry and factories can contain metals.

     4. Urban runoff (Parking lot runoff, yards, driveways, etc.)

     5. Agricultural runoff

     6. Total Suspended Solids: Total suspended solids can car metals with them as they move downstream. They can then be released downstream. Therefore, if T.S.S. is high, metals have more opportunities to find sites on which to transport themselves.

The amount of metals in a river can be mitigated by the alkalinty of a river.

WHAT HAPPENS AS WE TRAVEL DOWNSTREAM?

An abandoned car partly submerged in the South Platte River near Greeley, CO.