AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE 23RD INTERNATIONAL SCIENTIFIC CONFERENCE OF YOUNG SCIENTISTS AND SPECIALISTS (AYSS-2019) - Dubna, Russia (15–19 April 2019)] PROCEEDINGS OF THE 23RD INTERNATIONAL SCIENTIFIC CONFERENCE OF YOUNG SCIENTISTS AND SPECIALISTS (AYSS-2019) - Atmospheric deposition studies based on a 20-year period of moss biomonitoring in the vicinity of a lead-zinc plant in Kardzhali, Bulgaria (1995/6-2015/16)