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Phyto-Screening und Dendro-chemical Forensics

Innovative Methods for Assessing and Age-Dating of
Contaminant Impacts in Soil and Groundwater

1. PHYTO-SCREENING:
Assessment of Underground Pollution by Analysis of Wood Samples

Because trees uptake pollutants to which they are exposed, they can be used as indicators for pollutant releases in their vicinity. Soil and groundwater contaminants are uptaken and transported by sap in the outermost wood rings. These can easily be micro-sampled and analyzed for the sap enriched contaminants.

This method allows to qualitatively and semi-quantitatively identify or exclude the presence of underground contaminants as there are:

– Chlorinated Hydrocarbons (PCE, TCE, 1,2-CDE etc.)
– Aromatic Hydrocarbons (BTEX, Naphthalene)
– Heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn …)
– Arsenic

The method is currently checked for PAH, PCB and other organic compounds.

The correlation coefficient between tree and underground contamination is respectable (above 0.9). Whenever a site is properly vegetated, Phyto-Screening can be used for:

a rapid identification or exclusion of contamination (qualitative, semi-quantitative),
clarifying contaminant distribution by low cost raster measurements,
identification of release spots
delineation and monitoring of plumes

2. DENDRO-CHEMICAL FORENSICS:
Exact Age-Dating of Environmental Impacts by Multi-Element-Anbalysis of Wood Cores from Trees

Dendrochronological-chemical analyses is a newly invented powerful method because of its ability to use trees as proxy-recorders to identify when contaminants impacted the underground to affect the root ball. Since trees uptake elements essential for their growths such as Ca, Mg, Fe etc. they also uptake pollutants and tracers of pollutant compounds (such as Cl from chlorinated hydrocarbons or P, Cl and S from Fuel Hydrocarbons) which they are exposed to in the underground/rhizospehre. Such elements are built in and fixed to the wood cells during annual growths.

Due to that, the cores sampled from trees old enough and present within a pollutant plume, help to age- date the release, an essential information such as for liabilities.

The crucial data (33 elements, Manganese to Bismuth) are gained by Energy Dispersive X-Ray Fluorescence all over the sampled wood core from its oldest to its latest ring with X-Ray-beams every 50 μm. This allows age-dating by a precision one year.

Dendrochronological chemistry on tree cores has been conducted for forensic investigations dozens of sites (U.S.A., Canada, Germany, Portugal). Approximately one third of these cases had been tested as for already known contaminant releases.

In a litigated case study the dating of release and spread of a chlorinated solvent plume by ED-XRF- Linescanning of a tree core was precisely corroborated by technical documents on leak and repair activity.

: Chlorine concentration in wood core over more than 30 years. According to the multi-element analysis there are two synchronous anomalies (1984/84 and 2000) of Chlorine and Sulfur (indicators for fuel releases) and several mono-elemental anomalies (1986/86, 193/94, 1998 and 2004) of Chlorine (indicator for chlorinated hydrocarbons).

Dendro-chemical age-dating is a very reliable tool for attributing polluters to environmental impacts. HPC-office in Frankfurt conducted the first German Dendro-Forensik investigation (incl. age-dating) in 2009 followed by another three successful projects up to the end of 2010.

Phyto-Screening und Dendro-Chemical Forensics are approved investigation methods, that meet the standards of the state-of-the-art of science and technology. The methods are extremely environmentally friendly and can even be used in areas difficult to access. The trees are not damaged.

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