<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nabais, C</style></author><author><style face="normal" font="default" size="100%">Freitas, H</style></author><author><style face="normal" font="default" size="100%">Hagemeyer, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Dendroanalysis: a tool for biomonitoring environmental pollution?</style></title><secondary-title><style face="normal" font="default" size="100%">The Science of the total environment</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">biomonitoring</style></keyword><keyword><style  face="normal" font="default" size="100%">Dendroanalysis</style></keyword><keyword><style  face="normal" font="default" size="100%">Heavy metals</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">232</style></volume><pages><style face="normal" font="default" size="100%">33-37</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Trees of temperate regions usually form visible annual growth rings, which can be dated accurately. It is therefore possible to collect wood samples of different age and analyse their heavy metals content in order to get a chronological record of trace elements pollution in the tree's environment. This method of retrospective biomonitoring was called dendroanalysis. A basic assumption of dendroanalysis is the stability of the mineral distribution patterns, i.e. once the elements are stored, no significant mobility should occur. Additionally, neighbouring trees growing in the same environment should show similar radial element patterns. While some studies presented good correlations between radial distributions of heavy metals in tree rings and temporal records of pollution from industry or traffic, others failed in using dendroanalysis as a chronological record of pollution. Probably some elements can move at a certain rate in radial direction through the ray parenchyma cells. In this way the radial element distributions are subsequently changed. Growth rates of tree rings can also influence the concentrations of elements in wood. During periods of slow growth higher concentrations of elements can be found in the wood. Therefore, radial distribution patterns of heavy metals in tree rings should be used with caution as a tool for retrospective biomonitoring of environmental pollution.</style></abstract><accession-num><style face="normal" font="default" size="100%">10474259</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nabais, C</style></author><author><style face="normal" font="default" size="100%">Freitas, H</style></author><author><style face="normal" font="default" size="100%">Hagemeyer, J</style></author><author><style face="normal" font="default" size="100%">Breckle, S W</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Radial distribution of Ni in stemwood of Quercus ilex L. trees grown on serpentine and sandy loam (umbric leptosol) soils of NE-Portugal</style></title><secondary-title><style face="normal" font="default" size="100%">Plant and soil</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">dendrochemistry</style></keyword><keyword><style  face="normal" font="default" size="100%">Nickel</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">serpentine</style></keyword><keyword><style  face="normal" font="default" size="100%">tree rings</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><volume><style face="normal" font="default" size="100%">183</style></volume><pages><style face="normal" font="default" size="100%">181-185</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Concentrations of Ni were determined in xylem and phloem of Quercus ilex trees growing on serpentine and sandy loam soils of northeast Portugal. Radial distribution patterns of Ni in stemwood were compared to variations in annual growth increments of the trees. Concentrations of Ni in xylem and phloem were higher in Q. ilex from serpentine soil, when compared with Q. ilex of a sandy loam soil. The radial distributions of Ni showed large variations among the trees, although they all grew in the same area within a short distance from each other. These differences can be caused by small-scale spatial variations in the soil. Therefore, the use of such radial Ni distributions for a retrospective biomonitoring of the Ni pollution of larger areas appears questionable.</style></abstract></record></records></xml>