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Why are rocks, sand, and dirt considered pollutants?
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It can seem surprising that rocks, sand, and dirt are considered pollutants, since these materials are part of the natural environment. However, as with many other things, it is the amount that counts. Natural systems are not adapted to receiving these materials, and the nutrients and toxins they carry, in the amounts associated with some human activities. “Rocks, sand and dirt” have been included in the federal Clean Water Act’s definition of pollutant since its initial enactment in 1972, and are part of Maine’s law. Discharge of these materials can have serious adverse impacts on surface water quality and on the biological communities that inhabit our surface waters.
These pollutants carry nutrients to our waters and feed the algal growth that chokes some of our lakes. Maine’s 1994 water quality assessment report describes over 225,000 acres of lakes as not in attainment of water quality standards due to organic and nutrient enrichment. The enrichment comes, wholly or in part, from the eroded soil washing into the lakes. An additional 42,000 acres of lakes not in attainment were directly affected by siltation.
Also, siltation in small streams reduces habitat required for fish spawning, and available for other aquatic life. This happens in two ways. Although fish and other forms of aquatic life encounter these materials every day, they are not adapted to encountering large or continuous amounts. Sand and dirt act as abrasives, damaging soft tissues such as gills. Sand and dirt also cover and clog the porous substrate in streams. This destroys habitat important for the support of small aquatic life forms, and for the protection of eggs. It also inhibits the flow of water necessary to keep the habitat aerated. Adverse effects are long term, impairing the habitat long after the visual presence of the silt in the water is gone.
Why are man-made sand beaches bad for a lake?
Some of Maine’s lakes have natural sand beaches. They were created over time by geology and water movement. Plants and animals have adapted to these environments, and the beach areas are stable.
However, a load of sand dropped at the edge of a lake is a form of pollution and the combined effect of many beaches can harm the lake. Sand can be a significant source of phosphorus, a nutrient that contributes to algal blooms. Sand can also cover critical edge habitat, suffocating freshwater clams and mussels and eliminating fish breeding areas.
An artificial beach rarely stays put. Water and waves wash away the sand. Without continual new additions of sand the beach will disappear. As more sand is added to replenish the beach, the sand gradually spreads out over the bottom of the lake, smothering more and more habitat.
This article is an exerpt from Maine DEP website.
 

 

 

 

 

 

 

   
 
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