title: How to Determine the Environmental Exposure of PAHs Originating from Biochar.
abstract: Biochars are obtained by pyrolyzing biomass materials and are increasingly used within the agricultural sector. Owing to the production process, biochars can contain polycyclic aromatic hydrocarbons (PAHs) in the high mg/kg range, which makes the determination of the environmental exposure of PAHs originating from biochars relevant. However, PAH sorption to biochar is characterized by very high (10(4)-10(6) L/kg) or extreme distribution coefficients (KD) (>10(6) L/kg), which makes the determination of exposure scientifically and technically challenging. Cyclodextrin extractions, sorptive bioaccessibility extractions, Tenax extractions, contaminant traps, and equilibrium sampling were assessed and selected methods used for the determination of bioavailability parameters for PAHs in two model biochars. Results showed that: (1) the KD values of typically 10(6)-10(9) L/kg made the biochars often act as sinks, rather than sources, of PAHs. (2) Equilibrium sampling yielded freely dissolved concentrations (pg-ng/L range) that were below or near environmental background levels. (3) None of the methods were found to be suitable for the direct measurement of the readily desorbing fractions of PAHs (i.e., bioacessibility) in the two biochars. (4) The contaminant-trap method yielded desorption-resistant PAH fractions of typically 90-100%, implying bioaccessibility in the high μg/kg to low mg/kg range.
authors.affiliation: Department of Environmental Engineering, DTU Environment, Technical University of Denmark , Miljøvej Bld. 113, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Philipp
authors.initials: P
authors.lastname: Mayer
authors.affiliation: Agroscope ISS , Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Isabel
authors.initials: I
authors.lastname: Hilber
authors.affiliation: Department of Environmental Science, Aarhus University , Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors.forename: Varvara
authors.initials: V
authors.lastname: Gouliarmou
authors.affiliation: Department of Environmental Engineering, Norwegian Geotechnical Institute NGI , P.O. Box 3930 Ullevål Stadion, N-0806, Oslo, Norway.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Hale
authors.affiliation: Department of Environmental Engineering, Norwegian Geotechnical Institute NGI , P.O. Box 3930 Ullevål Stadion, N-0806, Oslo, Norway.|Department of Environmental Sciences (IMV), Norwegian University of Life Sciences (NMBU) , P.O. Box 5003, NO-1432 Ås, Norway.|Department of Applied Environmental Sciences (ITM), Stockholm University , 10691 Stockholm, Sweden.
authors.forename: Gerard
authors.initials: G
authors.lastname: Cornelissen
authors.affiliation: Agroscope ISS , Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bucheli
mesh_terms: D001682:Biological Availability; D018533:Biomass; D002606:Charcoal / Q000737:chemistry*; D004781:Environmental Exposure; D006801:Humans; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; C540010:biochar; D002606:Charcoal