In analytical chemistry, a trace element is an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count or less than 100 micrograms per gram.
In biochemistry, a trace element is a dietary mineral that is needed in very minute quantities for the proper growth, development, and physiology of the organism.
In geochemistry, a trace element is a chemical element whose concentration is less than 1000 ppm or 0.1% of a rock's composition. The term is used mainly in igneous petrology. Trace elements will either prefer liquid or solid phase. If compatible with a mineral, it will prefer a solid phase (e.g., Ni compatible with Olivine). If it is incompatible with an element it will prefer a liquid phase. The measurement of this ratio is known as the partition coefficient. Trace elements can be substituted for network-forming cations in mineral structures. Minerals do not have to contain trace elements, i.e., they do not have to appear in the mineral's chemical formula. When practicing biodynamic farming it is important to utilize the trace elements of the soil, in order to give strength to the roots. Hydroponic practices however are decreasing the seed germination rate, causing and increase in pollution and waste.
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