CENAM (Mexico) and JSI (Slovenia) successfully finished a key comparison CCQM-K127 in Category 13 (sediments, soils, ores, and particulates). Two soil samples were used in CCQM-K127 representing a non-contaminated soil with low concentrations of elements As, Cd, Fe, Pb and Mn, and a contaminated soil with higher concentration of elements As, Cd, Fe and Pb.
Non-contaminated soils contain trace and major elements at levels representing geochemical background of the region. The main sources of elements as contaminants/pollutants in soils are mining and smelting activities, fossil fuel combustion, agricultural practices, industrial activities and waste disposal. Contaminated/polluted sites are of great concern and represent serious environmental, health and economic problems. Characterization and identification of contaminated land is the first step in risk assessment and remediation activities. It is well known that soil is a complex matrix with huge variation locally and worldwide.
According to the IAWG´s five year plan, it is recommended to have a key comparison under the measurement service category of soils and sediments for the year 2015. Currently 13 NMI has claimed Calibration and Measurement Capabilities (CMCs) in Category 13 (sediments, soils, ores, and particulates): 29 CMCs in soil and 96 CMCs in sediments. In this regard this is a follow-up comparison in the category 13; wherein three key comparisons have been carried out during the years 2000 (CCQM-K13), 2003 (CCQM-K28) and 2004 (CCQM-K44). Since it is important to update the capabilities of NMIs in this category. CENAM and JSI proposed a key comparison in this category and a pilot study in parallel. The proposed study was agreed by IAWG members, where two soils samples were used in both CCQM-K127 representing a non-contaminated soil with low contents of elements (Arsenic, Cadmium, Iron, Lead and Manganese), and a contaminated soil with much higher content of selected elements (Arsenic, Cadmium, Iron and Lead). This broadens the scope and a degree of complexity of earlier measurements in this field. National metrology institutes (NMIs)/designate institutes (DIs) should, therefore, demonstrate their measurement capabilities of trace and major elements in a wide concentration ranges, representing background/reference sites as well as highly contaminated soils by their available analytical methods. This facilitated to investigate the core capabilities of participants to measure the mass fraction of tested elements in soil and therefore to claim their CMCs as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA).
In total, 19 institutes (NMIs/Dis) participated in the Key Comparison and the reported results of the key comparison were from 18 institutes (NMIs/DIs); 151 measurements were reported for CCQM-K127. The analytical techniques selected by the participant institutes were ICP-MS, ICP-OES, FAAS, ET-AAS and INAA (k0-method of INAA); the sample preparation methods used were based on microwave assisted digestion, except when it was used INAA.
After discussions it agreed to use the Median as KCRV and the MMADe as u(xKCRV). Generally most of the results of the participants were found consistent for all measurements according to their equivalence statements, excepting some extreme values, which were identified with value of di/U(di) higher than 1. This key comparison is a mean of providing evidence for practical demonstration of a CCQM comparison Calibration and Measurement Capabilities (CMCs) claims for contaminant and others elements, in low and medium content levels in non-contaminated and contaminated matrices described in category 13.