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. |