Phytoremediation. Transpiration Stream Concentration Factor (TSCF) Using TSCF to predict uptake. Quantifying root to shoot transfer

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1 Quantifying root to shoot transfer Transpiration Stream Concentration Factor () Summer course Modeling of Plant Uptake June 2013 at DTU Lyngby, DK C shoot, leaf, fruit BCF = C soil or C soilwater Chemical C xylem C aqueous phase = Estimating BCFs Estimating Travis and Arms, 1988 Briggs et al Hsu et al., 1990 Burken & Schnoor, 1992 Sicbaldi et al, 1997 Ciucani et al, 2002 Mckone, TE and Maddalena, RL Plant uptake of organic pollutants from soil: bioconcentration estimates based on models and experiments. Environ. Tox. Chem. 26(12): Phytoremediation Using to predict uptake Plant Uptake = ()(C C )(T) = transpiration stream concentration factor C C = chemical concentration in groundwater (mg/l) T = Volume of water transpired (L) 1

2 Transpiration Stream Concentration Factor Florida vs. Utah Using to predict uptake ~125 cm/yr ~1.5 m 1-10 mg/l TCE 1-10 mg/l ~50 cm/yr 2.3 m Root depth profiles different (shallow at Florida, deep at Utah). Tree core concentrations 100 X greater at HAFB Plant Uptake = ()(C C )(T) ( f ) = transpiration stream concentration factor C C = chemical concentration in groundwater (mg/l) T = Volume of water transpired (L) f = fraction of GW used ( 1)-Determine with stable isotopes measurements Doucette, W.J.; Bugbee, B.; Hayhurst, S.; Pajak, C.; Ginn, J. S. Uptake, metabolism, and phytovolatilization of trichloroethylene by indigenous vegetation: Impact of precipitation in phytoremediation. In: Transformation and Control of Contaminants, McCutcheon, S. C.; Schnoor, J. L., Eds. John Wiley and Sons, Inc. New York, NY, Variability of for TCE Davis et al Burken & Schnoor log K ow Estimated Chard 1999 Davis et al Orchard et al Burken and Schnoor appartus Burken, J. G. and J. L. Schnoor (1998). "Predictive relationships for uptake of organic contaminants by hybrid poplar trees." Environmental Science & Technology 32(21): DIPA pk a = 9.1 S= 870 g/l, log K ow = Sulfolane Orchard, B. J., W. J. Doucette, J. K. Chard and B. Bugbee (2000). "Uptake of trichloroethylene by hybrid poplar trees grown hydroponically in flow-through plant growth chambers." Environmental Toxicology and Chemistry 19(4): S= 1000 g/l, log K ow =

3 Cattails Final plant concentrations (mg/kg dry weight) DIPA Sulfolane Roots 46 Exposure: (20 mg/l) /(40 mg/l) Sulfolane in apple trees Control apple trees (no sulfolane added) Other polar compounds Apple: 16 mg/kg Leaves: 3700 mg/kg 1,4-dioxane MTBE Treatment apple trees (100 ppm sulfolane added) 30-day exposure: 55 mg/l Intact Plants measurement Pressure Chamber measurement for Intact plants Water Compound 3

4 Volatilization & Metabolism Water Compound Metabolite Pressure Chamber Method Water Compound Methods Plants and tomato Chemicals (25) 14 Volatiles (headspace/gc/ms) 2 semi-volatiles (LLE/GC/MS) 9 14 C-labeled (LSC) (1 volatile, 8 semivolatiles) Ranged in log K ow to 5 Used in previous plant uptake studies Tomato (shoots g, roots g) (shoots g, roots g) 5-7 weeks old Results-pressure chamber 4

5 Ave vs log K ow 25 chemicals vs log Kow predicted (Trapp 2006) log Kow model thick roots only with fine roots Briggs regression Dettenmaier, EM., Doucette, WJ., Bugbee, B Chemical Hydrophobicity and Uptake by Plant Roots. Environ. Sci. Technol. 43 (2): The model predicts that polar, non-volatile compounds will effectively be transported from soil to fruits, while lipophilic compounds will preferably accumulate from air into fruits. Reported Values Method: Intact plants, hydroponics Plant: barley Plant age: 10 days Exposure duration: hrs Water transpired: Average 1 ml/day Root weight: 0.1 g/plant? Method: Pressure chamber Plants: Tomato and Plant age: days Exposure duration: 5-48 hrs, steady state Water transpired : ml Root weight: g Why the scatter? Literature Pressure Chamber No protocols for conducting plant uptake studies Plant growth environment (soil or hydroponics) Growth conditions (temperature, light, humidity) Exposure system concentration and duration Plant age and species s assumed independent of these variables? 5

6 Hydroponic (s) Soil column (BCFs) Pressure Chamber vs Intact Plants Conclusions Pressure chamber vs. intact plants 3 days 30 days 90 days > Volatilization Metabolism Faster, less costly, more reproducible? Distribution Summary Root uptake () Polar, neutral compounds showed highest uptake More consistent data needed for reliable QSAR Intact plants-s method dependent Need accepted protocol Plant health, growth conditions Pressure Chamber Fewer variables Measure of root to shoot transfer potential Difference between Pressure Chamber and Intact plant values Provides indication of volatilization and metabolism loss Investigating differences in the root to shoot transfer of organic compounds between zucchini, squash, and soybean using a pressure chamber method Bill Doucette and Naho Garvin Utah State University, Logan, UT USA 6

7 Why is Zucchini unique? Enhanced desorption from soil? Exudates Not likely since soil and hydroponic uptake similar Enhanced xylem sap solubility? Co-solvents, proteins Facilitated transport thru root membrane? Carrier proteins Combination of processes Question Could the pressure chamber approach be used to examine the unique root to shoot transport of hydrophobic organics by zucchini? *Previous studies used intact plants. Plants 14C-labeled Study Compounds * * Caffeine, log K ow = Triclocarban, log K ow = (Hoyt) Zucchini (Gold Rush) Squash () * * Endosulfan, log K ow = 3.8 7

8 H 2 O Caffeine summary Time (min) Endosulfan Time (min) Triclocarban Compound Log K ow Soy Tritiated water ( 3 H 2 O) 14 C-Caffeine (n = 3) 14 C-Endosulfan (n = 3) 14 C-Triclocarban (n = 3) A 1.03 ± 0.022* B 0.78 ± A C -4.9 A ± ± Gold rush ± ± 0.03 *95% Confidence Interval, A: Hansch and Leo 1995, B: Hansch et al., 1989 C: Snyder et al., Time (min) Time (min) Xylem Sap Solubility Modified Shake Flask Method (EPA OPPTS ) Conc.(mol/L) 1.4e-4 1.2e-4 1.0e-4 8.0e-5 6.0e-5 4.0e-5 2.0e Caffeine (mol/l) Time (hr) 1.4e-6 DDW Reported Conc.(mol/L) 8e-5 6e-5 4e-5 2e-5 Endosulfan (mol/l) 0 Triclocarban (mol/l) Time (hr) DDW Reported 1.2e-6 1.0e-6 Conc.(mol/L) 8.0e-7 6.0e-7 4.0e-7 2.0e DDW Reported Time (hr) Xylem Sap Analysis Total Carbon Protein Content* Conc. (mg/l) 95 % 95 % (mg/l) CI(±) CI(±) Squash Zucchini *Bicinchoninic acid (BCA) protein assay kit by Sigma Aldrich. 41 Root Tissue Lipid Analysis % lipid (fresh wt) 95 % CI(±) Squash Zucchini

9 Summary (hydrophobics, log K ow > 4) zucchini > squash = soybean Xylem sap solubility zucchini > squash = soybean Xylem protein content zucchini > squash = soybean Root lipid content zucchini > squash = soybean Conclusions Pressure chamber method showed enhanced root to shoot transfer for zucchini as observed in intact plant studies Enhancement related in part to xylem solubility Additional characterization of xylem sap needed Pressure chamber method Rapid, reproducible approach for measurement Direct collection of xylem for solubility studies May be viewed as artificial 9