Vegetation/soil distribution of semivolatile organic compounds in relationto their physicochemical properties

The concentrations (C) of several semivolatile organic compounds (SOCs) in Norway spruce needles (N) and in the local humus horizon (O) of 25 remote A ustrian forest sites were used to calculate an ecosystem-oriented partition coefficient needles/humus horizon (C-N/C-O). Between 66 and 78% of the com pounds' variation of this quotient could be explained by each of the follow ing physicochemical para meters: vapor pressure (p(s)) and the partition co efficients n-octanol/water (K-ow), n-octanol/air (K-OA), and adsorbed/ diss olved in soil (K-oc) of the compounds. This result further underlines the u sefulness of these parameters for predicting the behavior of SOCs in terres trial ecosystems. Compounds with low ps and high K-ow, K-OA, and K-oc show a very low C-N/C-O quotient, which implies a higher accumulation of these c ompounds in the O horizon than in the needles. The role of forest soils as sink for these SOCs is demonstrated. Alternatively, C-N/C-O > 1, due to hig her concentrations in the needles than in the O horizon, have been shown fo r SOCs with comparably high ps and low K-ow, K-OA, and K-oc. In this respec t, the possible role of revolatilization of the more volatile SOCs from soi ls to needles is discussed. In the mineral soil layers below the O horizon, SOCs with lower K-oc and better water solubility tend to be less accumulat ed. However, if all investigated compounds are taken into consideration, ac cumulation in the mineral soil layers showed no general trend in relation t o the selected physicochemical parameters.