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Factors for calculated carbon dioxide concentrations in
water with known
pH, temperature and alkalinity measurements.
For example, if the water measurements are as follows:
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Temperature = 25° C
pH = 6.8
KH = 50 mg/L |
The multiplicative value to use for a pH of 6.8 and Temperature
of 25°C = 0.313
(see
chart below)
KH x Chart Value = mg/L CO2
example: 50 x 0.313 = 15.65 mg/L CO2
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Temperatures
( ° Centigrade)
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| pH |
5 |
10 |
15 |
20 |
25 |
30 |
35 |
| 6.0 |
2.915 |
2.539 |
2.315 |
2.112 |
1.970 |
1.882 |
1.839 |
| 6.2 |
1.839 |
1.602 |
1.460 |
1.333 |
1.244 |
1.187 |
1.160 |
| 6.4 |
1.160 |
1.010 |
0.921 |
0.841 |
0.784 |
0.749 |
0.732 |
| 6.6 |
0.732 |
0.637 |
0.582 |
0.531 |
0.495 |
0.473 |
0.462 |
| 6.8 |
0.462 |
0.402 |
0.367 |
0.335 |
0.313 |
0.298 |
0.291 |
| 7.0 |
0.291 |
0.254 |
0.232 |
0.211 |
0.197 |
0.188 |
0.184 |
| 7.2 |
0.184 |
0.160 |
0.146 |
0.133 |
0.124 |
0.119 |
0.116 |
| 7.4 |
0.116 |
0.101 |
0.092 |
0.084 |
0.078 |
0.075 |
0.073 |
| 7.6 |
0.073 |
0.64 |
0.058 |
0.053 |
0.050 |
0.047 |
0.046 |
| 7.8 |
1.046 |
0.040 |
0.037 |
0.034 |
0.031 |
0.030 |
0.030 |
| 8.0 |
0.029 |
0.025 |
0.023 |
0.021 |
0.020 |
0.019 |
0.018 |
| 8.2 |
0.018 |
0.016 |
0.015 |
0.013 |
0.012 |
0.012 |
0.011 |
| 8.2 |
0.012 |
0.010 |
0.009 |
0.008 |
0.008 |
0.008 |
0.007 |
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Factors
should be multiplied by total alkalinity (mg/L) to get
carbon dioxide (mg/L). For practical purposes, CO2
concentrations are negligible above pH = 8.4
Tucker (1984)
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