  Lambda Boo stars are predominately A-type stars with solar abundant C, N, O,
and S, but up to 2 dex underabundances of refractory elements. The stars'
unusual surface abundances could be due to a selective accretion of volatile
gas over dust. It has been proposed that there is a correlation between the
Lambda Boo phenomenon and IR-excesses which are the result of a debris disk or
interstellar medium (ISM) interaction providing the accreting material. We
observe 70 or 100 and 160 $\mu$m excess emission around 9 confirmed Lambda Boo
stars with the Herschel Space Observatory, to differentiate whether the dust
emission is from a debris disk or an ISM bow wave. We find that 3/9 stars
observed host well resolved debris disks. While the remaining 6/9 are not
resolved, they are inconsistent with an ISM bow wave based on the dust emission
being more compact for its temperature and predicted bow wave models produce
hotter emission than what is observed. We find the incidence of bright
IR-excesses around Lambda Boo stars is higher than normal A-stars. To explain
this given our observations, we explore Poynting-Robertson (PR) drag as a
mechanism of accretion from a debris disk but find it insufficient. As an
alternative, we propose the correlation is due to higher dynamical activity in
the disks currently underway. Large impacts of planetesimals or a higher influx
of comets could provide enough volatile gas for accretion. Further study on the
transport of circumstellar material in relation to the abundance anomalies are
required to explain the phenomenon through external accretion.
