The Soil Science Unit continues to provide stable isotope analyses for CRPs, TCPs and for the other FAO/IAEA regular activities. The following table summarises the analytical services provided during 2006.
CRP TC Seib Contract Total
Samples received 3 286 25 2 103 61 5 475
Requested analyses 15N enriched 1 368 25 907 61 2 361
15N nat. ab. 276 0 425 0 701
13C nat. ab. 2 194 0 1 768 0 3 962
18O nat. ab. 0 0 60 0 60
Total 3 838 25 3 160 61 7 084
Measurements carried out 15N enriched 2 590 39 1 497 0 4 126
15N nat. ab. 487 37 747 0 1 271
13C nat. ab. 4 117 0 2 940 0 7 057
18O nat. ab. 0 0 29 1 016 1 045
Total 7 194 76 5 213 1 016 13 499
There is a clear trend of increased requirement for natural abundance measurements of 13C and 18O in the last few years.
13C and 18O at natural abundance were mostly done in duplicates. Overall, the proportion of measurements for 15N enriched, 15N at natural abundance, 13C at natural abundance and 18O at natural abundance were: 30%, 9%, 52% and 8%
respectively.
0 5000 10000 15000 20000 25000
2001 2002 2003 2004 2005 2006
N-15 enriched N-15 nat. ab.
C-13 nat. ab.
O-18 nat. ab
Total number of analyses Total number of measurem.
The annual proficiency test (PT) for the measurement of 15N- and 13C isotopic abundance and total N and C concentration in plant materials
The following is a summary of the annual proficiency test IAEA-SSU-2006-01 on the analysis of three different plant materials for the isotopic abundance of stable isotopes 15N and 13C as well as the total element concentration of nitrogen (N) and carbon (C).
This annual PT is organized and conducted by the SSU. It is free of charge and especially tailored to the needs of agricultural research laboratories in developing Member States working with stable isotopes.
Three plant materials with different 15N- and 13C isotopic abundances and N and C contents were distributed to the participating laboratories in April 2006. The plant test materials were produced by the SSU and the assigned values and associated uncertainties were determined by application of a primary method (Isotope Ratio Mass Spectrometry, IRMS) for 15N- and 13C isotopic abundance determination. Laboratories were requested to analyse the 15N / total N- and/or the 13C / total C- content in the three different plant samples. Additionally a questionnaire on the implemented quality system had to be completed. The deadline was set at the end of October 2006. Eighteen of the 23 laboratories originally registered reported to the IAEA.
Figure 1: Geographical distribution of the laboratories that reported analytical results
Geographical distribution of participants in IAEA-SSU-2006-01 Number of labs (percentage)
8 (44%)Asia Europe
4 (22%)
Latin America
3 (17%) Africa
3 (17%)
Table 1: Summary of applied methods and instrumentation listed per region (OES = optical emission spectrometry, IRMS = isotope ratio mass spectrometry).
Applied methods:
Region Number
of participants
15N by OES
15N by
IRMS Ntotal by
Kjeldahl Ntotal by dry comb.
13C by
IRMS Ctotal by dry comb.
Africa 3 1 2 1 2 2 2
Asia 8 4 4 5 3 4 4
Europe 4 2 2 2 2 2 2
Latin America 3 3 - 3 - - -
TOTAL 18 10 8 11 7 8 8
The results were evaluated by statistical methods for assessing laboratory analytical performance by the ‘z-score test’. The standard deviation for proficiency assessment was set at a value corresponding ‘to the level of performance that the PT-organizer wishes the laboratories to be able to achieve’. Results received the status ‘acceptable’, when the calculated z-score was smaller or equal to the value of ±2 , a ‘warning’ was given, if the z-score was between ±2 and ±3, the results received the status ‘not acceptable’, when the calculated z-score was exceeding the value of ±3. Participants were
given a confidential code letter to assure anonymity and received a short report including the reference values of the three test samples and the ‘z-scores’ of all participants in December 2006. Certificates of participation are provided to all laboratories, a 'successful participation' is only stated to laboratories who showed proficiency in both, the isotope- and the total element concentration for one or both combined analyses. Individual assessments on sources of possible errors and proposed improvements of the applied methods were provided to each participant.
The combined analysis 15N / total N was analysed correctly by 61 percent of the participating laboratories (Fig. 2). The number of laboratories also analyzing 13C / total C increased from 5 to 8 compared to the previous year. As noted below the 13C / total C results still indicate some analytical weakness in half (50%) the participating laboratories (Fig. 3).
acceptable 11 (61%) warning
2 (11%) not acceptable
5 (28%)
Figure 2. Overall performance on the combined analysis of 15N / total N
acceptable 4 (50 %) warning
1 (12.5%) not acceptable
3 (37.5%)
Figure 3. Overall performance on the combined analysis of 13C / total C
The results of the PT demonstrate that initial appropriate steps towards quality assurance and quality control implementation had been taken by most participating laboratories.
Publications
An updated list of articles from SWMCN staff published in scientific journals and conference proceedings is available on our SWMN Section website at the URL http://www.iaea.org/programmes/nafa/d1/public/d1_pbl_1.html
Publications/Proceedings of Symposia and Seminars
IAEA Proceedings Series STI/PUB/1285. Management Practices for Improving Sustainable Crop Production in Tropical Acid Soils. Results of a Coordinated Research Project organized by the Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture (2006). IAEA, Vienna, Austria.
This is a priced IAEA publication. Paper copies cost 55 Euros. Instructions for ordering can be found on the webpage http://www-pub.iaea.org/
Papers in Scientific Journals and Conference Proceedings
Fulajtar, E., Mabit, L., Bernard, C. (2006). Assessing erosion-sedimentation processes and efficiency of soil conservation practices using radio-isotope techniques. In: Abstracts of the International Sediment Initiative Conference (ISIC). pp. 79-80 + CD-ROM. UNESCO Chair in Water Resources. 12-15 November 2006, Khartoum, Sudan.
Mabit, L., Bernard, C. and Laverdière, M.R. (2007). Assessment of erosion in the Boyer River watershed (Canada) using a GIS oriented sampling strategy and 137Cs measurements. CATENA (In press).
Mabit, L., Bernard, C. and Laverdière, M.R. (2007). Water erosion measurement at the watershed level by the Cs137 method. (Étude de la dégradation des sols par l’érosion hydrique à l’échelle des bassins versants en utilisant la méthode du Cs137). Agrosolution (In press).
Mabit, L. and Fulajtar, E. (2007). The use of 137Cs to assess soil erosion and sedimentation processes: advantages and limitations. In: Book of the extended Synopses of the International Conference on Environmental Radioactivity: From Measurements and Assessments to Regulation. IAEA Publication. IAEA-CN-145. Pages 338-339.
Mabit, L., Li, L., Toloza, A., Bernard, C. (2007) - Soil erosion processes and soil quality variability evaluated using fallout radionuclides. In: Geophysical Research Abstracts (CD-ROM), Volume 9, European Geosciences Union - General Assembly 2007, ISSN: 1029-7006. Abstract EGU2007-A-01090. pdf, 2 pages.
http://www.cosis.net/abstracts/EGU2007/01090/EGU2007-J-01090.pdf
Websites
Soil and Water Management and Crop Nutrition Section:
http://www-naweb.iaea.org/nafa/swmn/index.html
Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture:
http://www-naweb.iaea.org/nafa/index.html
FAO website: http://www.fao.org/waicent/FAOINFO/AGRICULT/Default.htm FAO/AGL (Land and Water Development Division):
http://www.fao.org/ag/agl/default.stm
The Soils Newsletter is prepared twice per year by the Soil and Water Management & Crop Nutrition Section, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture and FAO/IAEA Agriculture and Biotechnology Laboratory, Seibersdorf.
International Atomic Energy Agency
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A-1400 Wien, Austria July 2007