Boden-Atmosphäre Austausch persistenter organischer Schadstoffe: Bestimmung von Konzentrationsgradienten mit Passivsammlern
Zusammenfassung der Projektergebnisse
The three investigated sites were very comparable rural locations and indicate similar PAH concentrations in gas phase and deposition rates. Differences among the soil profiles are mainly due to the varying land use with agricultural soils being mixed regularly. Additionally, stable distribution patterns of all U.S. EPA Priority PAHs were observed for the different sites and soil horizons. Passive sampling in soils includes some uncertainties, particularly with respect to equilibration times exceeding the predefined timescales. Therefore, a precise measurement of sorption coefficients in soil profiles in the respective concentration range is needed in order to determine concentrations in aqueous or gas phase in the soil. In contrast, the quantitative use of passive samplers for atmospheric PAHs was verified by an extensive method-validation combining active and passive sampling as well as a numerical modelling approach. Seasonal monitorings show higher concentrations in the atmosphere during the cold season. Stable distribution patterns of representative PAHs for the different study sites were determined not only within soil samples but also for the atmosphere. Concentration gradients of PAHs in the gas phase and across the soil-atmosphere interface confirm continuous uptake of PAHs into soils. Only for short time periods during summer, temporal revolatilization from soil was determined for semi-volatile PAHs (up to Pyr) at all stations and for both years. Particle bound deposition was determined as the main input pathway of PAHs from the atmosphere into the soils. Therefore, the overall flux direction remains constant throughout the year, illustrating net deposition.
