Wildlife General - 6 of 8
Wildlife General FAQs - 8 Found
Understanding our fragile environment often begins with recognition of the importance of certain elements, such as zinc and iron, in relation to animals and plants. This recognition is well deserved because these essential elements are necessary for the life or health of an organism. Some elements such as carbon, hydrogen, oxygen, magnesium, potassium, and phosphorus are required in relatively large amounts by organisms. However, others are required in smaller quantities; these are referred to as trace elements. At the same time, if these or other elements occur in quantities great enough, toxicity can result. An element, or any substance, that occurs in the environment and contains concentrations above what are considered to be safe may be considered a contaminant. When contaminants occur at levels that are potentially harmful to organisms, they are labeled as hazards. Often the quantitative difference between essential amounts and toxic concentrations of these elements is very small. For example, the trace element selenium is required at a level of no less than 0.4 parts per million in the diet of cattle but can be toxic at levels greater than approximately 4 parts per million.
There are 16 essential elements to all animals and plants: Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Sodium (Na), Magnesium (Mg), Phosphorus (P), Sulfur (S), Chlorine (Cl), Potassium (K), Calcium (Ca), Manganese (Mn), Iron (Fe), Copper (Cu), Zinc (Zn), and Selenium (Se).
Trace essential elements such as fluorine, copper, selenium, molybdenum, and others can be hazardous to living organisms if present at high levels. Nonessential heavy metals such as arsenic, lead, mercury, cadmium, chromium are usually toxic to organisms as much lower levels than trace essential elements. Depending on the association that these nonessential elements may form with natural geologic materials such as organic matter, other elements or minerals, and adsorbers (such as clays), these elements can range from being safe to being extremely toxic.
Because of growing public concern about the environmental contamination, it is becoming increasingly important to better understand both the natural and human processes that control the movement of elements at the earth's surface. Elements can be quite mobile in water, and the majority of our environmental problems are ultimately associated with the contamination of surface and ground water.
When water comes into contact with rocks and soils, some of the minerals and organic substances dissolve and enter the natural waters. Forests and grasslands generally contribute only small amounts of these dissolved substances. However, it is possible for an area to contain unusually high concentrations of minerals, thereby depositing them to the waterways. For example, swamps and marshes often produce acidic and colored water. Other areas that contributed natural pollutants to water are those containing rocks with sulfide minerals, particularly pyrite.
Inorganic substances are cycled naturally through our environment at concentrations that usually do not adversely affect plants and animals. However, the combination of some natural processes with human activities can increase these substances to harmful or toxic levels. Therefore, toxic substances may have both natural and human sources.
Natural sources of toxic substance include rocks, volcanoes, sediments, and soils. Human activities that add toxic substances to the environment include smelting, manufacturing, refining, chemical processing, fertilizer application, irrigation, and waste disposal.
A large concentration of a substance commonly identifies a source of pollution but may not necessarily indicate a problem. In addition to the concentration, other characteristics of the substance must be considered. These characteristics include the amount of the substance released, the rate of release, its availability to organisms, and its residence time in a particular ecosystem.
Learn More: Circular 1105: Understanding Our Fragile Environment