ELSEVIER The Science of the Total Environment 180(1996) 107-l 16 the Science of the Total Environment A.hs.d..dJ.w.d~sd..unTm...-b ,.lolluFMlml..dl!3Y.Mb Assessing the quality of biomonitoring via signal-to-noise ratio analysis H.Th. Wolterbeek*, P. Bode, T.G. Verburg Interfaculty Reactor Institute, Derfr University of Technology, Mekelweg IS. 2629 JB Derfr, The Netherlands Received20 June 1995; accepted 24 August 1995 Abstract The analysis of the signal-to-noise ratio of a survey is introduced asa means to assess the quality of a survey.Here, the surveysignal is definedasthe surveyvariance, and the surveynoise is determined by measurement of the local variance (variance per site). The signal-to-noise ratio, and thus the quality of the survey,can be improved by factor analysis aidedprocessing of the data. This is illustratedby processing data from variousbiomonitoringprograms on trace element air pollution. Clean-up of the data-set, in which a bias-introducing contribution isremoved (for example, the soil factor) or source profile isolation, in which attention is focussed on a single source, yield strikingly different indications of the quality (or suitability) of the biomonitoringspecies whencompared with the indications obtained from the originaldataset. Theapproach presented herestresses that the quality of a survey largelydepends on the deci- sions takenwith respect to the selection of the biomonitor material;these decisions should be based on optimization of the signal-to-noise ratio rather than on minimizationof the noise only. Keywords: Biomonitoring; Quality; Signal-to-noise ratio; Local variance;Surveyvariance; Mosses; Lichens; Tree bark 1. Introduction Biomonitoring is the use of the properties of an organism to obtain information on certain aspects of the biosphere. When multi-parameter analysis is applied, especially in large-scale surveys, the infor- mation which is obtained may consist of many thousands of data points [l- 121, which can be processed in a variety of mathematical routines to permit a condensed and strongly-smoothed pre- sentation of results and conclusions. However, al- * Corresponding author. though reports on larger-scale biomonitoring are ‘easy-to-read’ and often include far-reaching inter- pretations, it is not possible to obtain an insight into the real meaningfulness or ‘quality’ of the sur- vey performed. Defining quality as the degree of excellence in which requirements (or goals) are met, the necessi- ty arises to establish a means to assess this degree of excellence by measurement and/or evaluation. In this paper a method is presented for assessing the quality of a biomonitoring survey, and for the quality of the biomonitoring species. The ap- proach is illustrated through an evaluation of re- 0048-9697/96/.$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDI0048-9697(95)04944-V