Corresponding author. Department of Basic Sciences and Environment, Faculty
of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg
C, Denmark. Tel.: þ45 3533 2420; fax: þ45 3533 2398.
E-mail address: jje@life.ku.dk (J.K. Jensen).
1 Current address: NIRAS, Sortemosevej 2, DK-3450 Alleroed, Denmark