Assuming the sample was drawn from an irrigation well or canal, convert the ppm measurement to mg/L and meq/L. Mg/L = meq/L × equivalent weight (see table) Equivalent weights of selected ions ConstituentĪ water chemistry report from a commercial lab shows that the sulfate concentration of a sample is 24 ppm.
However, brines are not considered in detail here, as they are never suitable as irrigation water.)Ĭoncentration data reported in milligrams per liter (mg/L) can be converted to milliequivalents per liter (meq/L), and vice versa. (For brines and other waters of extremely high salinity, it is necessary to account for the higher-than-unity solution density. That's because, except for highly saline water, the density of water is very close to 1.00 kilograms per liter. Similarly, parts per billion (ppb) is defined as follows: ppbĮquating the units of mass per kilogram and mass per liter is appropriate for a dilute solution such as irrigation water.
The ppm unit can be thought of as milligrams of solute per million milligrams of solution (water), or as milligrams of solute per kilogram of solution: ppm (One example is the SAR, described in detail later in this tutorial.)Ī laboratory also may report concentrations of constituents in parts per million (ppm) or parts per billion (ppb). The latter type of measure - milliequivalents per liter - is the preferred reporting method if you need to check the quality of a water analysis or to calculate certain water quality parameters that involve electrochemistry. The former unit is useful when you need to evaluate the total mass or the "mass concentration" (i.e., milligrams per liter) of particular constituents. When reporting the concentrations of elemental ions and dissolved molecules, a commercial laboratory typically will report the results in milligrams per liter or milliequivalents per liter, or both. Fundamentals Reporting the concentrations of ions and molecules
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