Using Trees to Monitor Subsurface Pollution Stefan Trapp stt@env.dtu.dk with help of Charlotte N. Legind, Morten Larsen, Antonio Franco, Joel Burken, Jirina Machackova, Arno Rein and Ulrich Gosewinkel Karlson Overall Objectives In the next 35 minutes I wish to present a cost-effective and non-invasive technique for site evaluation show examples for the use of trees to delineate subsurface pollution introduce tree growth as method for historical evaluation show some nice paintings of my talented daughters Dep. Environmental Engineering at the Technical University of Denmark Table of Contents Tree Core Sampling Trees to monitor subsurface pollution 1 Method description 2 Results from several sites 3 Conclusions and Outlook Traditional bore hole drilling requires heavy equipment is time consuming is expensive has limited sampling number Tree core sampling is rapid is inexpensive (is fun) allows many samples (if you have a strong Post Doc) 1
The Method Wood is sampled with a driller Wood samples are analyzed with common methods Chemical residues in wood indicate sub-surface contamination Why Trees? trees root into groundwater trees transport water upwards wood adsorbs compounds each tree is a combination of well, pump and passive sampler Tree core sampling Analysis of wood Transocation upwards in the xylem Sorption to wood K Wood = C Wood / C w Dettenmaier et al. 29 log K Wood =.27 +.63 log K OW (oak) log K Wood =.28 +.67 log K OW (willow) Concentration in xylem sap TSCF = Concentration in (ground)water Lignin is a good sorbent for lipophilic chemicals! Which compounds accumulate in wood? Lipophilic compounds (high log Kow) adsorb to soil organic matter and are not present in soil solution Polar compounds do not adsorb to wood Volatile compounds (high vapour pressure) escape to air Often compounds are metabolised by root zone bacteria or plant enzymes Medium lipophilic, persistent and non-volatile compounds should be translocated upwards and accumulate in wood of trees. Promising indicator compounds Many herbicides & other pesticides PCE, TCE and its metabolite DCE and TCAA (but not VC) naphthalene as only PAH RDX and TNT (explosives) BTEX? and heavy metals, such as copper and cadmium 2
Overview of field sites Results from field sites Czech Republik Hradcany, former USSR-air base; jet fuel (BTEX, alkanes) SAP, carcasses disposal plant; PCE (TCE, DCE) Denmark Glostrup, former rain water lagoon; TCE + BTEX Axelved, former petrol station; diesel & gasoline Vassingerød, former asphalt works; diesel and PAH Søllerød, former gas works; CN, PAH and BTX Esrom forest; As Cu Cr Møringa (Norway); mainly heavy metals Field site in Czech Republik: Hradcany (former Russian military airport) Hradcany (former military airport jet fuel) Hradcany airport Pollution: jet fuel Pure jet fuel 3
Remediation by venting and biostimulation Sampling at Hradcany Tree cores from 24 trees were taken at areas with varying contamination and analyzed for BTEX, light PAH and alkanes. Joel Burken, Missouri Example result from Hradcany Campaign at Hradcany BTX and alkanes were found in low concentration, and there was no relation to concentration in groundwater Compounds in wood were probably airborn Conclusion: it was not possible to use BTX or alkanes as indicator compounds for jet fuel. What does this tell us? Nothing! The reason for failure is unknown. Perhaps rapid metabolism in the root zone, or too deep pollution (6-8 m). We will try again with benzene in Zeitz. Field site SAP in CZ Carcasse recycling site SAP (CZ) Perchlorethene used from 1963 to 1988 Estimated spill: 15-25 t PCE and degradation products 4
Plume 25 based on GW wells (sum of chloroethenes) Sampling at SAP Ulrich Gosewinkel Charlotte Legind Morten Larsen Tree core sampling at SAP: 4 samples in 4 hours 5 4 3 2 1 Concentration of PCE g/kg Natural attenuation: Concentrations of TCE and Cis-DCE (mg/kg) 5 6 4 6 5 4 3 5 4 3 2 3 2 1 6 5 4 3 2 1 6 5 4 3 2 1 2 1 6 5 4 3 2 1 6 5 6 4 5 3 4 2 3 1 2 1 1 6 5 4 3 2 1 6 5 4 6 3 5 2 4 1 3 2 1 6 5 4 3 2 1 6 5 4 3 2 1 6 5 4 3 2 6 1 5 4 3 2 1 6 5 4 3 2 1 6 5 4 3 2 1 6 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 1 4 5 3 4 2 5 3 1 4 2 3 1 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 Comparison of methods Conclusions from SAP site Tree core sampling is a cheap and successful method to determine PCE and TCE plumes in shallow groundwater and to monitor natural attenuation. Groundwater sampling 24 wells 3 weeks Tree sampling 4 samples 4 hours Env. Sci Technol. 28 5
Former gas works Søllerød Gasworks in Holte Pollution: Iron Cyanides Free and complexed cyanide 1951 21 Gaswerk Holte in Søllerød Phytoremediation and public park Composition of gas works waste Typically Laboratory tests Willow tree transpiration test Iron cyanide Fe x CN y up to 5 g/kg PAH up to 1 mg/kg Sulphur up to 5% Evil substrate! 6
Lab results Uptake of free cyanide HCN into trees Toxicity Free cyanide toxic at > 2 mg/l. Iron cyanide is quite nontoxic to plants. PAH ( 16 mg/kg soil) are non-toxic, too. Trees dead No cyanide in living trees: Trees exposed to > 2 mg CN/L die! Uptake of iron cyanide - Fe(CN 6 ) 3- Uptake of iron from Fe(CN) 6 4-15 C (mg CN/kg) 2 15 1 5 C (mg Fe/kg) 125 1 75 5 25 Root Stem Leaf Solution, final 1 mg/l 5 mg/l 1 mg/l Root Stem Leaf mg/l 5 mg/l 1 mg/l Increase of total CN in exposed trees in lab Significant increase of Fe in exposed trees in lab Field sampling campaign in 26 Map of Contamination Holte gas works In 26, trees at the former gas works were sampled for free CN, complexed CN (= iron CN) and iron (Fe). Cyanide was still present in soil and groundwater. 7
Total cyanide, Holte gas works Iron, Holte gas works 1. 1 C (mg/kg) 1. 1. 1. C (mg/kg) 1 1 1.1. 1 2 3 4 5 6 7 8 9 1 Sampling point 1 1 2 3 4 5 6 7 8 9 1 Sampling point Leaves Stem Soil Leaves Stem Soil No (cor)relation between CN in soil and leaves or stem No (cor)relation between iron in soil and stem or leaves and the iron cyanide Summary of findings gas works Holte Cyanide or iron as indicator for gas works waste? In lab: no accumulation of free CN in living trees In lab: accumulation of total CN and iron in trees Outdoor: no relation between iron and total CN in soil and plants Conclusion: A field observation This gas works waste was deposited > 3 years ago. Still no plants grow on it. The waste is toxic due to its low ph. Neither free CN, nor total CN nor iron can be used as indicator for gas works waste! S H 2 SO 4 ph 2 The lack of vegetation or reduced growth may also be used as obvious tracer for gas works waste. Results from Louise Andresen Low ph (< 2) kills the plants. At ph > 3.3 first plants can grow. After liming, all tested species could grow in this gas works waste. 8
The growth of trees 1 Dendrochronology as indicator for subsurface pollution 1 Tree rings (dendrochronology) 2 Tree height Hypothesis When subsurface contaminants pass below a tree, it grows worse. This can be seen at the thickness of the tree rings. Results by Jean-Christophe Balouet et al. (27) (Orrouy, France) look promising. We plan to test the method at the SAP site. Tree height measurements winter 25 Tree height at phytorem sites in DK Method former tank station former asphalt works Height measurement with a telescopic bar Average distance between trees.5 m Comparison to chemical data from student excursions and maps Ulrich Reiter, ETHZ Axelved: gasoline & diesel Vassingerød: diesel & PAH Correlation between tree height and soil contamination in Axelved 25 Not significant! Tree height at asphalt works Vassingerød N R 2 <.1 Compaction and former buildings seem to impact tree growth (not contamination with PAH and oil) 9
Our next campaigns This year (29) we will test the feasibility of the tree core method or other vegetation sampling for heavy metals at fields sites in DK and in Norway (Møringa). Conclusions Tree core sampling successful Method tested successfully in the field: Chlorinated solvents: PCE, TCE and DCE (not VC) Method probably applicable, but not yet tested: Other chlorinated solvents (chloroform, trichlorethane and tetrachlorcarbon (CCl4) Dichlorophenol (positive in lab) MTBE (persistent and water soluble; but volatile Perchlorate (taken up and translocated in plants) Cu, Cd success likely Method failed or success unlikely No success was experienced with BTEX. Probably degraded PAH. Perhaps too lipophilic, except naphthalene Alkanes. Lipophilic, volatile, not persistent Free cyanide. Rapid degradation Iron cyanide. Degradation Iron. High natural background Phenol and monochlorophenol. Rapid degradation F A Q How deep? Typical tree roots 3 7 m but response down to 18 m (Sørek et al. 28). Which trees? Conifers have some advantages. Can I calculate GW concentration from tree core? No we found a rank correlation but no linear relation. Do I need allowance to make bore holes? Yes. Is the tree damaged? Very little. It s a forestry standard method. Where can I get more information? Download our guide and read papers. Get your own short guide to vegetation sampling at http://homepage.env.dtu.dk/stt 1