LIS 57 Study Summary

These tables summarize the measurements reported to the QA-SAC for the 57th Laboratory Intercomparison Study. A total of 77 laboratories reported measurements. Some measurements were missing or below the analytical detection limit (DL). N designates the number of reported values above the DL. Target values were provided by the reference laboratory. At the center of each set of N measurements is the Median or accepted target value of the set. Sigmas were estimated from the interquartile ranges and can be used to calculate Z-values. Half of the N measurements are within the 25th to 75th percentiles, which defines the range of Good measurements. Satisfactory measurements fall within the range defined by the Median ± Sigma. The limits for a measurement that Meets Data Quality Objectives are defined on page 4 of the Manual for the GAW Precipitation Chemistry Programme.

 

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Last update: March 30, 2018, 10:28 am

Sample 1 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 70 4.62 4.62 0.05 4.59 4.67 4.57 4.67 4.55 4.69
Conductivity μS/cm 65 21.5 21.7 1.0 20.9 22.3 20.7 22.7 20.2 23.2
Acidity (optional) μeq/L 10 N/A 28.1 6.5 23.4 32.1 21.6 34.6 21.1 35.1
Sulfate as SO42- mg/L 68 2.444 2.465 0.093 2.391 2.515 2.372 2.557 2.292 2.637
Nitrate as NO3- mg/L 71 1.810 1.820 0.048 1.780 1.845 1.772 1.868 1.693 1.947
Ammonium as NH4+ mg/L 70 0.631 0.591 0.025 0.568 0.603 0.566 0.616 0.550 0.632
Fluoride (optional) mg/L 21 0.040 0.038 0.003 0.037 0.041 0.035 0.041 N/A N/A
Chloride mg/L 68 0.779 0.763 0.026 0.743 0.778 0.736 0.789 0.687 0.838
Sodium mg/L 65 0.399 0.406 0.018 0.391 0.415 0.388 0.424 0.366 0.446
Potassium mg/L 64 0.127 0.125 0.010 0.116 0.129 0.115 0.135 0.100 0.150
Calcium mg/L 63 0.333 0.336 0.019 0.321 0.347 0.317 0.355 0.286 0.386
Magnesium mg/L 61 0.099 0.098 0.005 0.095 0.102 0.093 0.103 0.089 0.107

Sample 2 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 70 4.96 4.94 0.06 4.91 4.99 4.88 5.00 4.87 5.01
Conductivity μS/cm 65 11.8 12.3 0.6 11.8 12.6 11.7 12.9 11.5 13.1
Acidity (optional) μeq/L 10 N/A 14.0 6.8 11.6 20.7 7.2 20.7 10.5 17.4
Sulfate as SO42- mg/L 67 1.429 1.438 0.056 1.398 1.474 1.382 1.494 1.338 1.538
Nitrate as NO3- mg/L 71 0.630 0.624 0.028 0.605 0.643 0.596 0.652 0.581 0.667
Ammonium as NH4+ mg/L 70 0.271 0.247 0.015 0.236 0.256 0.232 0.262 0.230 0.264
Fluoride (optional) mg/L 15 0.005 0.005 0.003 0.005 0.010 0.002 0.008 N/A N/A
Chloride mg/L 68 0.791 0.780 0.032 0.754 0.796 0.748 0.811 0.702 0.857
Sodium mg/L 64 0.455 0.465 0.025 0.443 0.476 0.440 0.490 0.419 0.511
Potassium mg/L 64 0.109 0.108 0.011 0.097 0.112 0.097 0.119 0.087 0.129
Calcium mg/L 63 0.166 0.168 0.016 0.156 0.178 0.152 0.184 0.143 0.193
Magnesium mg/L 60 0.076 0.076 0.005 0.073 0.079 0.071 0.081 0.069 0.083

Sample 3 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 70 4.76 4.76 0.04 4.74 4.80 4.72 4.80 4.69 4.83
Conductivity μS/cm 65 20.6 20.8 0.9 20.0 21.2 19.9 21.7 19.4 22.2
Acidity (optional) μeq/L 10 N/A 18.3 8.5 17.1 28.5 9.8 26.8 13.8 22.8
Sulfate as SO42- mg/L 68 1.908 1.917 0.066 1.870 1.960 1.851 1.983 1.783 2.051
Nitrate as NO3- mg/L 71 0.971 0.976 0.028 0.952 0.990 0.948 1.004 0.908 1.044
Ammonium as NH4+ mg/L 70 0.409 0.380 0.024 0.360 0.392 0.356 0.404 0.354 0.406
Fluoride (optional) mg/L 22 0.054 0.051 0.005 0.047 0.054 0.046 0.056 N/A N/A
Chloride mg/L 68 2.015 2.016 0.042 1.977 2.034 1.974 2.058 1.815 2.217
Sodium mg/L 65 1.073 1.106 0.035 1.078 1.125 1.071 1.141 0.996 1.216
Potassium mg/L 63 0.216 0.217 0.013 0.206 0.224 0.204 0.230 0.174 0.260
Calcium mg/L 64 0.268 0.268 0.020 0.258 0.285 0.248 0.288 0.228 0.308
Magnesium mg/L 61 0.119 0.118 0.007 0.113 0.122 0.111 0.125 0.107 0.129