Comparison of Spider Web and Moss Bag Biomonitoring to Detect Sources of Airborne Trace Elements

Atmospheric particulate matter has become a major issue in urban areas from both a health and an environmental perspective. In this context, biomonitoring methods are a potential complement to classical monitoring methods like impactor samplers, being spatially limited due to higher costs. Monitoring using spider webs is compared with the more common moss bag technique in this study, focusing on mass fractions and ratios of elements and the applicability for source identification. Spider webs and moss bags withHypnum cupressiformewere sampled at the same 15 locations with different types of traffic in the city of Jena, Germany. In the samples, mass fractions of 35 elements, mainly trace metals, were determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) after aqua regia digestion. Significantly higher mass fractions in spider webs than in moss bags were found, even after a much shorter exposure period, and could not be ascribed completely to a diluting effect by the biological material in the samples. Different mechanisms of particle retention by the two materials are therefore assumed. More significant correlations between elements have been found for the spider web dataset. Those patterns allow for an identification of different sources of particulate matter (e.g. geogenic dust, brake wear), while correlations between elements in the moss bags show a rather general anthropogenic influence. Therefore, it is recommended to use spider webs for the short-term detection of local sources while moss bag biomonitoring is a good tool to show a broader, long-term anthropogenic influence.