This study aims to investigate the changes in atmospheric deposition trends in Bulgaria, studied using the moss biomonitoring technique since 1995. For the first time, a paired (site-wise) comparison was performed after a critical review of the sampling networks and adjusting for location, the distance between the sampling points, and moss species. Data from the 2005/2006 and 2015/2016 moss surveys were chosen as instrumental neutron activation analysis was employed in both to determine the content of 34 elements (Al, As, Ba, Br, Са, Ce, Cl, Со, Cr, Cs, Fe, Hf, I, K, La, Mn, Na, Nd, Ni, Rb, Sb, Sc, Se, Sr, Ta, Tb, Th, Ti, Tm, U, V, W, Yb, Zn). In addition, Cd, Cu, and Pb were determined using complementary analytical methods: inductively coupled plasma atomic emission spectroscopy in 2015/2016 and atomic absorption spectroscopy in 2005/2006. For the subset of 57 routinely sampled locations in Bulgaria, hierarchical clustering on principal components and multiple factor analysis (MFA) were applied to assess the spatial trends in the 10 years elapsed between the surveys, as well as to characterise the origin of the determined elements. Elevation and distance between the sampling points were used as additional variables in the multiple factor analysis plane to ascertain their effect on the overall variance in the datasets. Distribution maps were constructed to illustrate the deposition patterns for the pollutant Pb. The results were consistent with decreased industrial output in the country, increased coal combustion and transport pollution, and construction of roads.

Faculty of Physics and Engineering Paisii Hilendarski University Plovdiv Bulgaria

Faculty of Physics and Engineering Paisii Hilendarski University Plovdiv Bulgaria Agricultural University Plovdiv Bulgaria Sector of Neutron Activation Analysis and Applied Research Division of Nuclear Physics FLNP Joint Institute for Nuclear Research Dubna Russian Federation 141980

Nanotechnology Centre VSB Technical University of Ostrava Ostrava Czech Republic ENET Centre VSB Technical University of Ostrava Ostrava Czech Republic

Sector of Neutron Activation Analysis and Applied Research Division of Nuclear Physics FLNP Joint Institute for Nuclear Research Dubna Russian Federation 141980 Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering Bucharest Romania

Sector of Neutron Activation Analysis and Applied Research Division of Nuclear Physics FLNP Joint Institute for Nuclear Research Dubna Russian Federation 141980 Institute of Environmental Technology VSB Technical University of Ostrava Ostrava Czech Republic

References provided by Crossref.org