Uptake of Organic Contaminants from Soil into Vegetables and Fruits - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 402

Fig. 9.11 Demonstration of
the tree core method by one
of the authors
difficult to access with heavy equipment, for example gardens in residential areas
or dense forests. Even better, the effect on trees of the contaminants in a plume is
reflected by the size of tree rings, and dendrochronology can be used to determine
when a plume passed below the tree (Balouet et al. 2007 ).
The potential of this monitoring procedure is large. Tree core sampling as mon-
itoring method was successfully applied for chloroethenes (Gopalakrishnan et al.
2007 ; Vroblesky et al. 1999 ). Larsen et al. ( 2008 ) found a good agreement between
the plume delineation by traditional well drilling and by tree core sampling, but only
monotone (and not linear) relations. The authors could also use the method to mon-
itor Natural Attenuation of a PCE spill. Sorek et al. ( 2008 ) even detected several
before unknown spills in Tel Aviv by a random sampling of trees in the city. But
there are also limitations. Tree core sampling should rather be used for assessing
the presence of contaminants than for determining exact subsurface concentrations.
Because from tree core measurements alone, precise evaluation of subsurface con-
tamination will not be possible, due to varying concentrations in wood (Larsen et al.
2008 ; Sorek et al. 2008 ).
The method could also be successful for some heavy metals such as cadmium
and copper, and it may also work for MTBE, perchlorate and dichlorophenol. For
a number of contaminants the method was not successful, to mention are BTEX,
PAHs (except naphthalene), free and iron complexed cyanide, long-chain alkanes
(generally petroleum products), phenol, monochlorophenol, iron and lead.