Splitting of the strongest absorption lines with a lower-level excitation potential \chi _ { low } < 1 eV has been detected for the first time in the optical spectra of the post-AGB star V354 Lac obtained with a spectral resolution R = 60000 at the 6-m telescope BTA .
Analysis of the kinematics shows that the short-wavelength component of the split line originates in the star ’ s thick gas–dust envelope .
Disregarding the splitting of strong lines when the chemical composition is calculated leads to overestimated excess of s-process elements ( Ba , La , Ce , Nd ) in the stellar atmosphere .
The profiles of strong absorption lines have been found to be variable .
The available radial-velocity data suggest the absence of any trend in the velocity field in the atmosphere and circumstellar envelope of V354 Lac over 15 years of its observations .