LIS 55 Study Summary

These tables summarize the measurements reported to the QA-SAC for the 55th 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: December 22, 2016, 9:40 am

Sample 1 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 66 5.50 5.30 0.09 5.25 5.37 5.21 5.39 5.23 5.37
Conductivity μS/cm 62 21.2 21.8 0.5 21.4 22.2 21.3 22.3 20.3 23.3
Acidity (optional) μeq/L 9 N/A 5.2 5.7 4.3 12.0 0.0 10.9 3.9 6.5
Sulfate as SO42- mg/L 67 2.656 2.674 0.080 2.631 2.740 2.594 2.754 2.487 2.861
Nitrate as NO3- mg/L 71 1.697 1.687 0.060 1.640 1.722 1.627 1.747 1.569 1.805
Ammonium as NH4+ mg/L 70 0.715 0.693 0.032 0.669 0.712 0.661 0.725 0.645 0.741
Fluoride (optional) mg/L 20 0.039 0.036 0.007 0.031 0.040 0.029 0.042 N/A N/A
Chloride mg/L 68 2.238 2.249 0.066 2.201 2.290 2.182 2.315 2.024 2.473
Sodium mg/L 66 1.383 1.412 0.046 1.376 1.438 1.366 1.457 1.271 1.552
Potassium mg/L 65 0.289 0.286 0.017 0.273 0.296 0.269 0.303 0.229 0.343
Calcium mg/L 66 0.454 0.454 0.025 0.435 0.468 0.429 0.478 0.386 0.521
Magnesium mg/L 63 0.202 0.202 0.008 0.195 0.206 0.194 0.210 0.182 0.222

Sample 2 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 66 5.18 5.18 0.11 5.11 5.26 5.07 5.29 5.11 5.25
Conductivity μS/cm 62 4.9 5.3 0.3 5.0 5.5 5.0 5.6 5.0 5.6
Acidity (optional) μeq/L 9 N/A 6.9 5.6 5.8 13.4 1.3 12.5 5.2 8.6
Sulfate as SO42- mg/L 65 0.455 0.460 0.025 0.448 0.482 0.435 0.485 0.428 0.492
Nitrate as NO3- mg/L 69 0.540 0.540 0.028 0.516 0.553 0.512 0.568 0.503 0.577
Ammonium as NH4+ mg/L 69 0.157 0.155 0.016 0.146 0.168 0.139 0.171 0.145 0.165
Fluoride (optional) mg/L 20 0.025 0.023 0.006 0.020 0.028 0.017 0.029 N/A N/A
Chloride mg/L 56 0.059 0.062 0.009 0.057 0.069 0.053 0.070 0.056 0.067
Sodium mg/L 50 0.031 0.030 0.006 0.025 0.034 0.024 0.036 0.027 0.033
Potassium mg/L 45 0.015 0.015 0.006 0.012 0.020 0.009 0.021 0.012 0.018
Calcium mg/L 56 0.076 0.073 0.013 0.064 0.081 0.060 0.086 0.063 0.083
Magnesium mg/L 47 0.015 0.016 0.002 0.014 0.018 0.014 0.018 0.015 0.017

Sample 3 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 66 4.67 4.70 0.07 4.63 4.73 4.63 4.77 4.63 4.77
Conductivity μS/cm 62 21.6 21.6 0.7 21.0 22.0 20.9 22.3 20.1 23.1
Acidity (optional) μeq/L 10 N/A 23.4 6.9 19.2 28.5 16.5 30.3 17.6 29.2
Sulfate as SO42- mg/L 67 2.343 2.366 0.071 2.334 2.430 2.295 2.437 2.201 2.531
Nitrate as NO3- mg/L 71 1.215 1.207 0.054 1.156 1.230 1.153 1.261 1.123 1.291
Ammonium as NH4+ mg/L 70 0.444 0.435 0.019 0.419 0.445 0.416 0.453 0.405 0.464
Fluoride (optional) mg/L 20 0.020 0.019 0.007 0.013 0.023 0.012 0.025 N/A N/A
Chloride mg/L 68 1.567 1.572 0.060 1.524 1.604 1.512 1.631 1.415 1.728
Sodium mg/L 66 0.978 1.005 0.042 0.978 1.034 0.963 1.047 0.905 1.105
Potassium mg/L 65 0.176 0.176 0.010 0.170 0.183 0.166 0.186 0.141 0.211
Calcium mg/L 65 0.227 0.229 0.021 0.209 0.237 0.208 0.250 0.195 0.263
Magnesium mg/L 63 0.117 0.118 0.006 0.112 0.121 0.112 0.124 0.107 0.129