RELATIONS BETWEEN SULPHATE, AMMONIA, NITRATE, ACIDITY AND TRACE ELEMENT CONCENTRATIONS IN TREE BARK IN THE NETHERLANDS

Bark flakes were sampled in a biomonitoring survey throughout The Netherlands. Tree species used were oak (65 samples) and ‘non-oak’ (58 samples) (poplar, elm, willow). Bark elemental analysis was carried out for As, Br, Ca, Cd, Ce, Co, Cr, Cs, Fe, Hg, K, La, Na, Ni, Pb, Rb, Sb, Sc, Se, Sm, Th, and Zn. Furthermore, bark acidity, SO4, NH4 and NO3 were determined. Further variables introduced into the data-set were DIST (closest distance to sea water) and the dummy variably OAK (tree species).