Airborne organic micropollutant concentrations in mosses and humus as indicators for local versus long-range sources

Abstract

The concentrations of HCB, PCB, and PAH in epiphytic mosses (Hylocomium splendens and Pleurozium schreberi) and forest humus were used to study the atmospheric exposure of conferous forests in a region in central Sweden. Air concentrations of HCB and PCB were monitored around an expected source. Moss contamination was used as a short-term exposure indicator, and humus contamination was assumed to indicate long-term exposure to HCB, PCB, and PAH.The level of HCB in mosses (0.4-1.7 ng/g, by dry weight, DW) complied well with background values. The levels of PCB measured as a sum of 7 identified PCB-congeners varied between 2-28 ng/g DW, with the highest levels in moss from the western part of the region, and decreasing concentrations from west to east. Around an expected PCB source in the southeastern part of the region the concentrations of PCB declined with increasing distance from the source area. The identified PAH concentrations in mosses varied between 39 and 730 ng/g DW. The PAH content in the mosses consisted mainly of nonvolatile PAH while the more volatile PAH were below the detection limit. The levels of HCB in humus were slightly more than in mosses (0.4-3.3 ng/g DW), and complied well with the background values. Sum PCB in the humus varied between 2 and 28 ng/g DW. The PAH in the humus were mainly nonvolatile PAH. The PAH concentrations in humus varied between 99 and 2600 ng/g DW. The air concentrations of PCB around the expected source (radius <1.5 km) were higher than background levels, and most likely caused the raised levels of PCB measured in the moss nearby.