ASSESSING THE QUALITY OF BIOMONITORING VIA SIGNAL-TO-NOISE RATIO ANALYSIS

The analysis of the signal-to-noise ratio of a survey is introduced as a means to assess the quality of a survey. Here, the survey signal is defined as the survey variance, and the survey noise 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 fa ctor analysis aided processing of the data. This is illustrated by pro cessing data from various biomonitoring programs on trace element air pollution. Clean-up of the data-set, in which a bias-introducing contr ibution is removed (for example, the soil factor) or source profile is olation, in which attention is focussed on a single source, yield stri kingly different indications of the quality (or suitability) of the bi omonitoring species when compared with the indications obtained from t he original dataset. The approach presented here stresses that the qua lity of a survey largely depends on the decisions taken with respect t o the selection of the biomonitor material; these decisions should be based on optimization of the signal-to-noise ratio rather than on mini mization of the noise only.