Posts Tagged: electrical conductivity

Water Quality Terminology

Along with drought there are also concerns about water quality which has all kinds of weird units that area actually convertible.  Here's a little guide for the principle water quality components and their conversions.

Water Terminology

Common ions in water: calcium (Ca2+), magnesium (Mg2+), sodium (Na1+)

sulfate (SO42-), chloride (Cl-), carbonate (CO32-),                                                    bicarbonate (HCO3-), boron (H3BO3)

Measured as parts per million (ppm) or milligrams per liter (mg/l), which are interchangeable , or milliequivalents per liter (meq/l). A milliequivalent is the ppm of that ion divided by its atomic weight per charge.

                Example: Ca2+ with atomic weight of 40 and a solution concentration of possibly 200 ppm. Ca2+ has two charges per atom, so it has a weight of 20 per charge.     200 ppm divided by 20 = 10 meq of calcium for a liter of water.

Total Dissolved Solids (TDS): measure of total salts in solution in ppm or mg/L

Electrical Conductivity (EC): similar to TDS but analyzed differently.

                Units: deciSiemens/meter(dS/m)=millimhos/centimeter (mmhos/cm)=

                                                1000 micromhos/cm (umhos/cm).

                ConversionTDSEC: 640 ppm=1 dS/m= 1 mmhos/cm=1000 umhos/cm

Hardness: measure of calcium and magnesium in water expressed as ppm CaCO3

pH: measure of how acid or base the solution

Alkalinity: measure of the amount of carbonate and bicarbonate controlling the pH, expressed as ppm CaCO3.

Sodium Adsorption Ratio (SAR): describes the relative sodium hazard of water

                                SAR= (Na)/((Ca+Mg)/2)1/2, all units in meq/l

1.5 feet of water with EC of 1.6 adds 10,000 # of salt per acre

and that same water with 20 mg/l of nutrient will supply 80# of that nutrient/acre

Sea water has ~ 50 dS/m, 20,000 ppm Cl, 10,000 ppm

Irrigation water WATCH OUT- 1,000 ppm TDS, 100 ppm Na/Cl, 1 ppm B

avocado water

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