Environmental Pollution 76 (1992) 15-18 Active biomonitoring of polycyclic aromatic hydrocarbons by means of mosses J. W. M. Wegener, M. J. M. van Schaik & H. Aiking Institute.fi~r Environmental Studies, Free University, De Boelelaan 1115, 1081 HV Amsterdam, The Netherlands (Received 30 October 1990; revised version received 29 May 1991; accepted 3 June 1991) Spherical bags, packed with 20 g of peat moss (Sphagnum spp.), were exposed to ambient air at a distance of 1 km from a plant manufacturing electrodes for the production of aluminium, near Rotterdam, The Netherlands. In these bags, the concentrations of six polycyclic aromatic hydrocarbons were determined, and compared with the concentrations in moss bags that had been exposed in relatively clean areas. From the results it can be concluded that, in addition to their useful application for biomonitoring of heavy metals, mosses can be applied in active biomonitoring of polycyclic aromatic hydrocarbons in ambient air. INTRODUCTION PAHs Polycyclic aromatic hydrocarbons (PAHs) form a large group of organic compounds, characterized by the presence of two or more condensed aromatic rings. A number of PAHs are proven or suspected carcinogens (IARC, 1983). As a result, PAHs are considered human health hazards. Apart from a relatively small contribution of natural sources, such as forest fires and volcanic activity, PAHs emissions to the environment result mainly from human activities. These sources include aluminium production, coke production from coal, wood preservation and combustion of fossil fuels (traffic, domestic heating, electricity production). Mosses as biomonitors As early as 1950, moss was used for the measurement of industrially emitted fluorine in ambient air (MacIntyre et al., 1952). In the late 1960s, the first observations were made on the use of mosses as biomonitors for air deposition of metals (Riihling & Tyler, 1968, 1971; Goodman & Roberts, 1971). Due to their large surface area, cation-exchange properties, and the fact that they derive their water and nutrients almost exclusively from air, mosses are excellent monitors for the deposition of metals from air. Environ. Pollut. 0269-7491/92/$05.00 © 1992 Elsevier Science Publishers Ltd, England. Printed in Great Britain 15 It can be argued that the same properties make mosses suitable as monitors for air deposition of organic micropollutants as well. In this case, cation-exchange properties are not of importance, but instead the capacity to absorb large organic molecules is the key parameter. The first applications of mosses as monitors of the deposition of organic micropoilutants were made in the early 1980s (Thomas & Herrmann, 1980). Most of the work concentrated on the deposition of organochlorine compounds, such as pesticides and polychlorobiphenyls (PCBs). However, in some studies a few PAHs were studied as well. In Table 1, an overview of the literature on biomonitoring of PAHs by means of mosses is given. In the aforementioned studies naturally occurring mosses were collected from tree-trunks or ground surfaces (passive biomonitoring). In our study, however, mosses collected from a clean area (Ireland) have been exposed to ambient air in the form of spherical bags (active biomonitoring). In this kind of biomonitoring, the selection of the locations is not restricted by the condition of natural occurrence of mosses. Moreover, the time of exposure can be well-defined. In the present study, moss bags were exposed to ambient air at a distance of 1 km from a plant manufacturing electrodes for the production of alum- inium, leeward with respect to the prevailing wind direction. The plant is located in the Botlek area, a highly industrialized area west of Rotterdam, in the Province of South-Holland, The Netherlands. For reference pur- poses, moss bags have been exposed at three relatively clean areas (rural locations) in the Province of South- Holland (Alblasserwaard, Krimpenerwaard and Vijf- herenlanden). The PAHs under investigation corn-