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12/14/2017
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Recommended maximum concentrations for inorganic constituents in water

Note: Drinking water limits are based on U.S. Environmental Protection Agency primary and secondary standards for public water supplies ( http://www.epa.gov/safewater/mcl.html). Stock water and irrigation water recommendations are from U.S. Department of Agriculture Natural Resources Conservation Service water-quality guidelines. The guidelines are general and may vary depending on specific applications. Irrigation guidelines are based on continuous irrigation. (mg/L = milligrams per liter, ug/L = micrograms per liter).

Commonly occurring metals and other constituents
Constituent Drinking water limits (mg/L) Stock water limits (mg/L) Irrigation water limits (mg/L)
Calcium (Ca) --- --- ---
Magnesium (Mg) --- 2,000 ---
Sodium (Na) --- 2,000 See SAR
Potassium (K) --- --- ---
Iron (Fe) 0.3 [a][s] --- ---
Manganese (Mn) 0.05 [a][s] --- 2.0
Silica (SiO2) --- --- ---
Bicarbonate (HCO3) --- --- ---
Carbonate (CO3) --- --- ---
Chloride (Cl) 250 [a][s] 1,500 ---
Sulfate (SO4) 250 [a][s] 1,500 [b]
Nitrate (NO3 as N) 10 [p] 100 ---
Fluoride (F) 4 [p] 2 ---
Phosphate (as P) --- --- ---
Total dissolved solids 500 [a][s] 5,000 2,000 [c]
Specific conductance --- --- 2,500 [c]
pH 6.5 - 8.5 [a][s] --- 4.5 - 9.0
Total hardness --- --- ---
Total alkalinity --- --- ---
Sodium Adsorption Ratio --- --- 8-18[d]
Trace metals
Trace Metal Drinking water limits (ug/L) Stock water limits (ug/L) Irrigation water limits (ug/L)
Aluminum (Al) 50-200 [a][s] --- 1,000
Antimony (Sb) 6 [p] --- ---
Arsenic (As) 10 [p] 50 100
Barium (Ba) 2,000 [p] --- ---
Boron (B) --- --- See Boron
Bromide (Br) --- --- ---
Cadmium (Cd) 5 [p] 10 5
Chromium (Cr) 100 [p] 1,000 100
Cobalt (Co) --- 1,000 50
Copper (Cu) 1,300 [p] 500 200
Lead (Pb) 15 [p] 50 5,000
Lithium (Li) --- --- 2,500
Molybdenum (Mo) --- --- 5
Nickel (Ni) --- --- 200
Phosphate (P) --- --- ---
Selenium (Se) 50 [p] 50 20
Silver (Ag) 100 [a][s] --- ---
Strontium (Sr) --- --- ---
Titanium (Ti) --- --- ---
Uranium (U) 30 [p] --- ---
Vanadium (V) --- --- ---
Zinc (Zn) 5,000 [a][s] 24,000 2,000
Zirconium (Zr) --- --- ---

Footnotes:

--- There is currently no standard for this constituent.
[a] This standard is based on aesthetic quality of water (i.e. odor, color, etc.) and is not a health standard.
[b] High concentrations of sulfate may restrict calcium uptake by crops.
[c] Varies with crop; generally dissolved solids should be less than 2,000 mg/L (equivalent to specific conductance of about 2000 to 3000 micromhos/cm).
[d] Dependent upon other variables such as type of clay in soil and salt content of water. (See SAR)
[p] U.S. Environmental Protection Agency maximum contaminant level or action level: revised October 13, 1999.
[s] U.S. Environmental Protection Agency secondary contaminant level: revised October 13, 1999.
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