  We present a 3-mm and 1.3-cm spectral line survey conducted with the Mopra
22-m and Parkes 64-m radio telescopes of a sample of 40 cold dust cores,
previously observed with BLAST, including both starless and proto-stellar
sources. 20 objects were also mapped using molecular tracers of dense gas. To
trace the dense gas we used the molecular species NH3, N2H+, HNC, HCO+, H13CO+,
HCN and H13CN, where some of them trace the more quiescent gas, while others
are sensitive to more dynamical processes. The selected cores have a wide
variety of morphological types and also show physical and chemical variations,
which may be associated to different evolutionary phases. We find evidence of
systematic motions in both starless and proto-stellar cores and we detect line
wings in many of the proto-stellar cores. Our observations probe linear
distances in the sources >~0.1pc, and are thus sensitive mainly to molecular
gas in the envelope of the cores. In this region we do find that, for example,
the radial profile of the N2H+(1-0) emission falls off more quickly than that
of C-bearing molecules such as HNC(1-0), HCO+(1-0) and HCN(1-0). We also
analyze the correlation between several physical and chemical parameters and
the dynamics of the cores. Depending on the assumptions made to estimate the
virial mass, we find that many starless cores have masses below the
self-gravitating threshold, whereas most of the proto-stellar cores have masses
which are near or above the self-gravitating critical value. An analysis of the
median properties of the starless and proto-stellar cores suggests that the
transition from the pre- to the proto-stellar phase is relatively fast, leaving
the core envelopes with almost unchanged physical parameters.
