Comparabilty of analytical data proved by ringtests and standard measurements during the 2nd German Soil Survey

Transcription

1 Comparabilty of analytical data proved by ringtests and standard measurements during the 2nd German Soil Survey Nils König (1),Uwe Blum (2); Egbert Schönfelder (1) (1) Northwest German Forest Research Station, (2) Bayrische Landesanstalt für Wald und Forstwirtschaft, Freising, Germany

2 1. Introduction 2. Quality control program of the 2nd German Soil Survey (BZE II) 3. Evaluation of the standard material measurements and the ring test result of all labs 4. Results 5. Conclusions

3 1. Introduction In Germany the experience of the work of the expert commission for Forestry Analysis during the last years together with the Working Group QA/QC in Labs within ICP Forests led to a specific quality control program for the 2nd German soil survey (BZE II), which has been running from NW-FVA Northwest German Forest Research Station

4 2. Quality control program of the 2nd German Soil Survey (BZE II) - the use of harmonized, well-defined and documented analytical methods for each parameter, published in the German Handbook of Forestry Analysis (reference methods) - a ring test program with annual ring tests (3 soil and 2 humus) before and during the survey; the participation and the requalifying after each ring test was mandatory - mandatory measurement of specially produced standard material for each parameter during the survey; measurement of the control standards all 20 samples; mandatory recording of the results in control charts

5 - participating laboratories (sometimes for only some parameters): 13 - problems: not all labs have sent the data of the standard material measurements

6 3. Evaluation of the standard material measurements and the ring test result of all labs 1. Variation within the labs: standard deviation for each parameter (measurement of the standard materials) 2. Variation between the labs: - comparison of the results of the standard material measurements - Comparison of the ring test results

7 3. Evaluation of the standard material measurements and the ring test result of all labs for each parameter 3 graphs are shown: 1. all single values of the standard material from all labs over time 2. mean for each lab with standard deviation and signifikant trend over time 3. mean of the z-score of all ring test samples results for each lab

8 all single values of the standard material from all labs over time +/- 10 % of mean +/- 20 % of mean Red dots: results of the ring tests of the labs labs

9 mean lab 3 mean for each lab with standard deviation and signifikant trend over time significant trend over time (from green to red) mean all lab Standard deviation Number of measured standard material samples

10 Z-score = (mean lab mean tot ) / SD tot (the Z-score shows the dimension of the deviation of the mean of a lab from the mean of all labs as a function of the variation among the labs) Standard deviation mean of the z-scores of all ring test samples results for each lab mean deviantion from mean +/- 20 % mean deviantion from mean +/- 10 % mean of the Z-scores of lab 08 without (blue) and with (red) outliers Number of measured ring test samples of lab 11 without (blue) and with (red) outliers

11 4. Results

12 4. Results Variation within the laboratories: standard deviation for each parameter (measurement of the standard materials) (%) exchang. elements ph

13 Corg, TN Aqua regia extract. elements

14 Particle size

15 total elements reactive Fe,Al

16 Variation between the laboratories: comparison of the measurements of the standard materials and the ring test 7 examples

17 example 1: C (total carbon)

18 example 2: Ca (exchangeable)

19 example 3: Ca (aqua regia extractable)

20 example 4: Zn (aqua regia extractable)

21 example 5: ph (H 2 O)

22 example 6: K (aqua regia extractable)

23 example 7: Mn (exchangable)

24 5. Conclusions: Comparability of the analytical results of the 2nd German Soil Survey between labs and over time parameter group mean variation of the means (standard m.) total C, N +/- 10 % +/- 5 % mean variation of the deviation of the mean (ring tests) ph (H + ) +/- 20 % +/ % exchangable +/- 10 % +/- 15 % Na aqua regia extractable +/ % +/- 15 % K, Na total +/ % +/- 15 % reactive Fe, Al +/- 10 % +/- 15 % parameters not comparable