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  2. Total dissolved solids - Wikipedia

    en.wikipedia.org/wiki/Total_dissolved_solids

    When measuring water treated with water softeners, high levels of total dissolved solids do not correlate to hard water, as water softeners do not reduce TDS; rather, they replace magnesium and calcium ions, which cause hard water, with an equal charge of sodium or potassium ions, e.g. Ca 2+ ⇌ 2 Na +, leaving overall TDS unchanged [9] or even ...

  3. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...

  4. Hoagland solution - Wikipedia

    en.wikipedia.org/wiki/Hoagland_solution

    The artificial solution described by Dennis Hoagland in 1933, [1] known as Hoagland solution (0), has been modified several times, mainly to add ferric chelates to keep iron effectively in solution, [6] and to optimize the composition and concentration of other trace elements, some of which are not generally credited with a function in plant nutrition. [7]

  5. Biomass (ecology) - Wikipedia

    en.wikipedia.org/wiki/Biomass_(ecology)

    This translates to about 426 gC/m 2 /yr for land production (excluding areas with permanent ice cover), and 140 gC/m 2 /yr for the oceans. However, there is a much more significant difference in standing stocks—while accounting for almost half of total annual production, oceanic autotrophs account for only about 0.2% of the total biomass.

  6. Nutrient cycle - Wikipedia

    en.wikipedia.org/wiki/Nutrient_cycle

    A simplified food web illustrating a three-trophic food chain (producers-herbivores-carnivores) linked to decomposers. The movement of mineral nutrients through the food chain, into the mineral nutrient pool, and back into the trophic system illustrates ecological recycling. The movement of energy, in contrast, is unidirectional and noncyclic.

  7. Drinking water quality standards - Wikipedia

    en.wikipedia.org/wiki/Drinking_water_quality...

    A parametric value in this context is most commonly the concentration of a substance, e.g. 30 mg/L of iron. It may also be a count such as 500 E. coli per litre or a statistical value such as the average concentration of copper is 2 mg/L.

  8. Food chain - Wikipedia

    en.wikipedia.org/wiki/Food_chain

    Food chain in a Swedish lake. Osprey feed on northern pike, which in turn feed on perch which eat bleak which eat crustaceans.. A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as earthworms and woodlice ...

  9. Iron deficiency - Wikipedia

    en.wikipedia.org/wiki/Iron_deficiency

    Iron deficiency, or sideropenia, is the state in which a body lacks enough iron to supply its needs. Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key component of the hemoglobin protein, acting as a transport medium for electrons within the cells in the form of cytochromes, and facilitating oxygen ...