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We report our new spectropolarimetric observations for 67P dust over4,000--9,000 Angstrom using the ESO/Very Large Telescope in January--March 2016(phase angle ranging $\sim$26--5 deg) to constrain the properties of the dustparticles of 67P and therefrom diagnose the dust environment of its coma andnear-surface layer at around the end of the Southern summer of the comet. Weexamined the optical behaviours of the dust, which, together with Rosettacolour data, were used to search for dust evolution with cometocentricdistance. Modelling was also conducted to identify the dust attributescompatible with the results. The spectral dependence of the polarisation degreeof 67P dust is flatter than found in other dynamical groups of comets insimilar observing geometry. The depth of its negative polarisation branchappears to be a bit shallower than in long-period comets and might be gettingshallower as 67P repeats its apparitions. Its dust colour shows a change inslope around 5,500 Angstrom, (17.3 $\pm$ 1.4) and (10.9 $\pm$ 0.6) % (1,000Angstrom)$^{\rm -1}$ for shortward and longward of the wavelength,respectively, which are slightly redder but broadly consistent with the averageof Jupiter-Family comets. Observations of 67P dust in this study can beattributed to dust agglomerates of $\sim$100 $\mu$m in size detected by Rosettain early 2016. A porosity of 60 % shows the best match with our polarimetricresults, yielding a dust density of $\sim$770 kg m$^{\rm -3}$. Compilation ofRosetta and our data indicates the dust's reddening with increasing nucleusdistance, which may be driven by water-ice sublimation as the dust moves out ofthe nucleus. We estimate the possible volume fraction of water ice in theinitially ejected dust as $\sim$6 % (i.e. the refractory-to-ice volume ratio of$\sim$14).

VLT spectropolarimetry of comet 67P: Dust environment around the end of its intense Southern summer