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).Straightforward multivariate correlation analysis was performed to check the effects on bark metal retention of the non-metal pollutants 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 variations in bark metal and non-metal pollutant concentrations, and to account for the non-random distribution of OAK and non-OAK tree species.The results indicate that the non-oak and oak bark samples may be combined to form 123 samples containing data-set for As, Br, Cd, Ce, Co, Fe, La, Na, Sc, Sm, Th, 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(+)-dependent). In the presented data-set, bark sulphate, ammonia and nitrate could not be shown to significantly affect bark metal retention.