Embed Size (px)
Citation preview
1
Progress in Phytoscreening
Stefan Trapp
with help by Arno Rein, Mette Algreen and Ulrich Gosewinkel Karlson
Dep. Environmental Engineering at the Technical University of Denmark
Overall Objectives
In the next 15 minutes I wish to introduce a rapid, cost-effective and non-invasive technique for site evaluation, show examples for the use of trees to delineate subsurface pollution, present progress and answer questions.
► Trees take up and translocate (soluble and persistent) pollutants. ► Analyzing tree core samples allows to detect sub-surface contamination. ► Toxics in soil- and groundwater can lead to permanent effects on plants. Reduced size of tree rings and inorganic metabolites can trace historical extent of plumes = dendrochronology.
Conceptual and methodological approach
Tree core sampling Analysis of wood
Why Trees?
► Some trees root > 10 m deep
(average rooting depth 3-7 m)
► Trees are permanent and frequent on
brownfields
► wood adsorbs compounds
each tree is a combination of
● well,
● pump and
● passive sampler
The outer 5 cm is sampled (bark is thrown away)
The borer (Suunto, ca. 100 Euro)
2
The tree one year after: the wound has healed completely
Perchlorethene used from 1963 to 1988
Estimated spill: 150-250 t
Example: Field site SAP in CZ Plume distribution based on groundwater wells
GW is blue dots HJ and trees is colored bullets A1..A27
3
Plume distribution based on tree core sampling Comparison of methods
Groundwater sampling
24 wells 3 weeks to 10 years
Tree sampling
40 samples 4 hours
Larsen et al. (2008), Environ. Sci. Technol. 42, 1711–1717
0
100
200
300
400
500
0
100
200
300
400
500
1
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
0
100
200
300
400
500
Natural attenuation:
Concentrations of TCE and Cis DCE (mg/kg) Wetland sampling
at SAP site
Later, PCE and TCE from
a second plume were
found, stretching into a
swamp area.
This plume remained
undetected for a decade
because heavy equipment
(blue) couldn't be used in
that area - but
tree coring could.
Wittlingerova et al. 2013
Summary
Tree core sampling is a cheap and successful method to
determine PCE and TCE plumes in shallow groundwater
and to monitor natural attenuation.
Get your own short guide to vegetation sampling at
www.env.dtu.dk/homepages/stt/
When to sample?
It was always assumed that summer is the best time - but no!
Autumn gave highest response.
Wittlingerova et al. 2013 Environ. Sci. Pollut. Res. 20:834–847
Sampling over 12 months
dotted line: GW level
blue line: GW
green line: tree
4
Phytoscreening for Heavy Metals
Why heavy metals?
● Heavy metals are a problem with high relevance in (urban) soils.
● Heavy metals are persistent and non-volatile and we know they are
taken up into plants.
● We have the equipment to analyze heavy metals in our labs.
Disadvantage: Heavy metals are "natural" elements and will occur at a
certain background level in all soils and plants.
Research project TIMBRE and PhD Mette Algreen started in 2011.
Test and Reference Sites
HIGH polluted
Valby slam basin
LOW polluted
Former steel works
NOT polluted
Reference sites
Results unit mg/kg in wood
1) Sig. difference to reference only for
highly polluted soils (site 1)
2) Uptake is tree specific (willows are
better but don't grow everywhere)
3) No false positives - few false
negatives
Not sure whether I can recommend
this at this stage.
Algreen et al. Environ Sci Pollut Res
submitted
Relation of heavy metals in soil and wood
Heavy metals are "natural" elements and will occur at a certain background
level in all soils and plants. Essential metals (Cu, Zn) are regulated
enzymatically. Signal in trees only at HIGH soil concentration!
Principles of heavy metal transfer into plants
McLaughlin et al. 2011
F A Q Phytoscreening with tree coring
How deep? Typical tree roots 3 – 7 m but response down to >18 m
(Sørek et al. 2008).
Which trees? For organics little difference. Willows for HM.
Which compounds? PCE, TCE and chlorinated solvents
BTEX, MTBE, heavy metals under investigation.
Can I calculate GW concentration from tree core? No
we found rank correlation but no linear relation.
Do I need allowance to make small holes into trees? Yes.
Is the tree damaged? No. It’s a forestry standard method.
Where can I get more information? Download our “guide”:
http://www.ufz.de/task/index.php?de=19258
German and English guidelines
5
http://www.task.ufz.de/index.php?de=19258
F A Q Application of phytoscreening
So what is phytoscreening useful for?
We do recommend it for
- prescreening to use sophisticated methods more efficiently
- (pre-)screening of large areas to find the source or plume
- shallow aquifers
- areas where heavy equipment is useless (wetlands, swamps,
urban gardens, backyards)
- areas were bore holes are risky (e.g., military areas, urban
areas)
- for low budget projects (private owners, communes, investors)
And yes, the method is available on the market.
A small estimation of costs
Area: 100 x 100 m = 1 ha
Sampling: Every 10 m a tree gives 100 trees
Time needed: Sampling about 2 days, 1 expert + 1 strong person (32 h)
Evaluation of results + report 3 days (28 h)
Equipment: ca 100 €
Lab costs: duplicates, 200 x 50 € = 10 000 €
Sum costs:
60 h x 120 € + 10 000 € = 17 200 € plus my 5000 € profit = 22 200 € + tax
for a medium-sized site with trees (1 ha)
Danish costs.
The traditional engineer makes many
bore holes to find sub-surface pollution
Conclusions
But the clever engineer
samples trees
End of “Tree core sampling”
Acknowledgements
This work was funded by the European Commission, project
TIMBRE.
I wish to thank my project partners, my kollegas and my enthusiastic
students at DTU.
Thank you so much for your attention.
Tusind tak!
Questions?
Frequent mistake: sampling of very
hard trees (here Acer sp. = ahorn) [email protected]
