title: Quantification of the overall measurement uncertainty associated with the passive moss biomonitoring technique: Sample collection and processing.
abstract: In this study we examined 6080 data gathered by our research group during more than 20 years of research on the moss biomonitoring technique, in order to quantify the variability generated by different aspects of the protocol and to calculate the overall measurement uncertainty associated with the technique. The median variance of the concentrations of different pollutants measured in moss tissues attributed to the different methodological aspects was high, reaching values of 2851 (ng·g-1)2for Cd (sample treatment), 35.1 (μg·g-1)2for Cu (sample treatment), 861.7 (ng·g-1)2and for Hg (material selection). These variances correspond to standard deviations that constitute 67, 126 and 59% the regional background levels of these elements in the study region. The overall measurement uncertainty associated with the worst experimental protocol (5 subsamples, refrigerated, washed, 5 × 5 m size of the sampling area and once a year sampling) was between 2 and 6 times higher than that associated with the optimal protocol (30 subsamples, dried, unwashed, 20 × 20 m size of the sampling area and once a week sampling), and between 1.5 and 7 times higher than that associated with the standardized protocol (30 subsamples and once a year sampling). The overall measurement uncertainty associated with the standardized protocol could generate variations of between 14 and 47% in the regional background levels of Cd, Cu, Hg, Pb and Zn in the study area and much higher levels of variation in polluted sampling sites. We demonstrated that although the overall measurement uncertainty of the technique is still high, it can be reduced by using already well defined aspects of the protocol. Further standardization of the protocol together with application of the information on the overall measurement uncertainty would improve the reliability and comparability of the results of different biomonitoring studies, thus extending use of the technique beyond the context of scientific research.
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain. Electronic address: bfjaboal@usc.es.
authors.forename: J R
authors.initials: JR
authors.lastname: Aboal
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: M T
authors.initials: MT
authors.lastname: Boquete
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Carballeira
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Casanova
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Debén
authors.affiliation: Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Fernández
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000378:metabolism; D000397:Air Pollution / Q000706:statistics & numerical data*; D044002:Bryophyta / Q000378:metabolism*; D004784:Environmental Monitoring / Q000379:methods*; D007221:Industry; D019216:Metals, Heavy / Q000032:analysis* / Q000378:metabolism; D052638:Particulate Matter / Q000032:analysis; D015203:Reproducibility of Results; D013030:Spain; D013048:Specimen Handling; D014131:Trace Elements / Q000032:analysis; D035501:Uncertainty
chemical_list: D000393:Air Pollutants; D019216:Metals, Heavy; D052638:Particulate Matter; D014131:Trace Elements
keywords: Atmospheric inputs; Heavy metals and metalloids; Protocol standardization; Variance