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A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, [1] [2] but is also used to refer to minor elements in the composition of a rock, or other chemical substance. In nutrition, trace elements are classified into two groups: essential trace elements, and non-essential trace ...
A trace is usually indicated by a capital letter "T" or the word "trace" in place of a numerical amount of accumulation. [1] A trace measurement is not usually considered equivalent to any numerical value, and so adding together several trace amounts (for example, when computing monthly totals) will still be considered equal to a trace in most ...
Trace metals are the metals subset of trace elements; that is, metals normally present in small but measurable amounts in animal and plant cells and tissues. Some of these trace metals are a necessary part of nutrition and physiology. Some biometals are trace metals. Ingestion of, or exposure to, excessive quantities can be toxic.
Phosphorus occurs in amounts of about 2/3 of calcium, and makes up about 1% of a person's body weight. [10] The other major minerals (potassium, sodium, chlorine, sulfur and magnesium) make up only about 0.85% of the weight of the body. Together these eleven chemical elements (H, C, N, O, Ca, P, K, Na, Cl, S, Mg) make up 99.85% of the body.
The remaining elements are trace elements, of which more than a dozen are thought on the basis of good evidence to be necessary for life. [1] All of the mass of the trace elements put together (less than 10 grams for a human body) do not add up to the body mass of magnesium, the least common of the 11 non-trace elements.
Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere.Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere (not including water vapor).
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Trace amounts of methane, at the level of several ppb, were first reported in Mars's atmosphere by a team at the NASA Goddard Space Flight Center in 2003. [176] [177] Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal. [178]
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