Mosses are useful, ubiquitous accumulation biomonitors and as such can be used for biomonitoring surveys. However, the biomonitoring of atmospheric pollution can be compromised in urban contexts if the targeted biomonitors are regularly disturbed, irregularly distributed, or are difficult to access. Here, we test the hypothesis that cemeteries are appropriate moss sampling sites for the evaluation of air pollution in urban areas. We sampled mosses growing on gravestones in 21 urban and peri-urban cemeteries in the Paris metropolitan area. We focused on Grimmia pulvinata (Hedwig) Smith, a species abundantly found in all studied cemeteries and very common in Europe. The concentration of Al, As, Br, Ca, Ce, Cl, Cr, Cu, Fe, K, Mn, Ni, V, P, Pb, Rb, S, Sr, Ti, and Zn was determined by a total reflection X-ray fluorescence technique coupled with a slurry sampling method (slurry-TXRF). This method avoids a digestion step, reduces the risk of sample contamination, and works even at low sample quantities. Elemental markers of road traffic indicated that the highest polluted cemeteries were located near the highly frequented Parisian ring road and under the influence of prevailing winds. The sites with the lowest pollution were found not only in the peri-urban cemeteries, adjoining forest or farming landscapes, but also in the large and relatively wooded cemeteries located in the center of Paris.Our results suggest that (1) slurry-TXRF might be successfully used with moss material, (2) G. pulvinata might be a good biomonitor of trace metals air pollution in urban context, and (3) cemetery moss sampling could be a useful complement for monitoring urban areas. Graphical abstract We tested the hypothesis that cemeteries are appropriate moss sampling sites for the evaluation of air pollution in urban areas. We sampled 110 moss cushions (Grimmia pulvinata) growing on gravestones in 21 urban and peri-urban cemeteries in the Paris metropolitan area. The concentration of 20 elements in mosses was determined by a total reflection X-ray fluorescence technique coupled with a slurry sampling method. Statistical analysis revealed that: - Urbanized Parisian areas crossed by traffic roads have the highest polluted cemeteries with a strong influence of main wind direction on the distribution of air pollutants - As expected, small cemeteries with low tree density were heavily polluted - Less obvious, large green spaces such as large cemeteries (Père Lachaise, Montmartre, Montparnasse) in the center of a dense metropolis like Paris present the same level of atmospheric trace metal pollution as cemeteries in less urbanized areas or nearing a very large forest.This suggests that even in densely urbanized areas, there is more spatial variability in pollution distribution than usually assumed and that large urban areas with low traffic and green filters such as trees are likely to intercept air pollutants.

L'evaluation des risques pour la sante et l'environnement lies a differents types d'exposition tels que la pollution de l'air, necessite d'elargir les activites de surveillance de l'environnement. En milieu urbain, le trafic automobile devient la principale source d'emission de polluants entrainant dans les periodes de fort ensoleillement l'elevation des niveaux l'ozone qui peuvent quelquefois depasser les valeurs reglementaires. Il est donc important de connaitre sa distribution au niveau d'une agglomeration. L'utilisation d'un bioindicateur vegetal, le tabac Bel-W3, particulierement sensible a l'ozone, a permis d'etudier et de realiser la cartographie des differents niveaux d'ozone en juin, juillet et aout 1996 sur la Communaute Urbaine du Grand Nancy. En juin, periode caracteristique d'ensoleillement prolonge accompagnee d'un trafic urbain dense, l'etude cartographique montre une repartition concentrique autour du noyau urbain. La presence d'ozone la plus elevee se rencontre a la peripherie de l'agglomeration, particulierement au nord-est de Nancy-ville, ou le panache de pollution de la ville se deplace sous l'influence des vents dominants, et a l'ouest ou le relief accentue favorise l'accumulation de polluants.