Footprints of Lagrangian flow structures in Eulerian concentration distributions in periodic mixing flows

► Lagrangian flow features have been linked to the spectrum of the mapping matrix. ► Transport barriers result in a block-diagonal structure of the mapping matrix. ► Each block matrix corresponds with either a chaotic sea or a (cluster of) island(s). ► The spectrum of the block matrix reflects the kind of structure (chaos/islands). ► Higher-order periodicity yields a distinct permutation within the block matrix.