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

Bark flakes were sampled in a biomonitoring survey throughout The Neth erlands. Tree species used were oak (65 samples) and 'non-oak' (58 sam ples) (poplar, elm, willow). Bark elemental analysis was carried out f or 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 we re determined. Further variables introduced into the data-set were DIS T (closest distance to sea water) and the dummy variably OAK (tree spe cies). Straightforward multivariate correlation analysis was performed to check the effects on bark metal retention of the non-metal polluta nts SO4, NH4 and NO3, and of bark acidity. The OAK variable served to identify species-specific metal and non-metal pollutant behaviour. The DIST variable was used to visualize geography(source)-related variati ons in bark metal and non-metal pollutant concentrations, and to accou nt for the non-random distribution of OAK and non-OAK tree species. Th e results indicate that the non-oak and oak bark samples may be combin ed to form 123 samples containing data-set for As, Br, Cd, Ce, Co, Fe, La, Na, Sc, Sm, Tn, Zn, NH4, NO4, SO4 and acidity, but not for Rb, Cs , Se, K, Ni, Pb and Sb (species-specific) and for Ca and Hg (H+-depend ent). In the presented data-set, bark sulphate, ammonia and nitrate co uld not be shown to significantly affect bark metal retention.