Supporting Information for. Development of Solid Ceramic Dosimeter for the Time Integrative Passive. Sampling of Volatile Organic Compounds in Waters

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1 Supporting Information for Development of Solid Ceramic Dosimeter for the Time Integrative Passive Sampling of Volatile Organic Compounds in Waters 5 6 Riza Gabriela Bonifacio 1, Go-Un Nam 1, In-Yong Eom 2, Yongseok Hong 1,* Department of Environmental Engineering, Daegu University, 201 Daegudae-ro, Jillyang-eup, Gyeongsan-si, Gyeongsangbuk-do, Republic of Korea 2 Department of Chemistry, Daegu Catholic University, 330 Geumrak-ri, Hayang-eup, Gyeongsan-si, Gyeongsangbuk-do, Republic of Korea * Corresponding author: YS. Hong, yshong@daegu.ac.kr, tel: , fax: In Preparation for: Environmental Science & Technology Supporting Information: 20 pages, 4 figures, 9 tables S1

2 20 21 S1. Summary of some of the properties of the volatile organic compounds Table S1. Selected VOCs for Study VOCs Molecular Structure MW (g/mol) Log K ow Solubility in water (g/l) [20/25 C] Density (g/ml) Vapor pressure (Pa at 25 C) Henry s constant (at 298 K) LeBas Molar Volume (cm 3 /mol) 1,2-Dichloroethane (DCA) C 2 H 4 Cl C 6 H 6 Benzene (BZN) Trichloroethene (TCE) C 2 HCl C 7 H 8 Toluene (TOL) S2

3 C 2 H 3 Cl 3 1,1,2- Trichloroethane (TCA) C 2 Cl 4 Tetrachloroethene (PCE) C 6 H 5 Cl Chlorobenzene (CBZ) C 8 H 10 Ethylbenzene (EBZ) S3

4 C 8 H 10 p-xylene (PXY) C 9 H 12 1,3,5- trimethylbenzene (TMB) C 6 H 4 Cl 2 1,3-dichlorobenzene (DCB) Source: CRC Handbook of Chemistry and Physics 1 S4

5 23 S2. Construction of Ceramic Dosimeter and Soil-Gas Sampler 24 (a) (b) Figure S1. The ceramic dosimeter (a) with PTFE caps showing its dimensions (5 cm long including the caps), and (b) the dosimeter with the stainless steel soil-gas sampler probe. 29 S3. Liquid-liquid extraction (LLE) method The aqueous phase extraction was done by taking a 1-mL aliquot of the aqueous solution and pouring it into 2-mL vials containing 700 µl of spiked DCM. The vials were then mixed with a vortex mixer for at least 1 minute. The vials were agitated again after the layers became settled. S5

6 To remove the interface emulsion, 20 µl of saturated sodium chloride was added to the mixture and vortexed for 30 seconds. The vials were stored upside down for easier extraction. The organic layer was separated and poured into another vial by extracting at least 500 µl of the DCM layer using a 2-mL gas-tight syringe and then analyzed by GC-MS. The extraction efficiency was obtained by measuring the absorbed concentration against the amount of VOCs left in the water. The presented values are average of 4 replicates. 39 Table S2. Extraction Efficiency of Liquid-liquid Extraction Method VOCs % Efficiency % Std Dev DCA BZN TCE TOL TCA PCE CBZ EBZ PXY TMB DCB AVERAGE The percent extraction efficiency was calculated using the equation: C %ExtractionEfficiency= DCM 100% (S1) C The extraction efficiency is as high as 94.2 ± 2.2% for 1, 2-dichloromethane, and has an average value of 88.0 ± 5.4% for the selected VOCs (Table S2). This implies that the method as presented DCM,i S6

7 44 45 in this paper is satisfactory for extracting VOC concentrations in water. The extraction efficiency is a factor to be added when calculating for solvent-extracted water samples S4. Kinetics of VOC absorption at various concentrations (1100 ug L -1 ) 48 S7

8 (116 ug L -1 ) 49 S8

9 (16.9 ug L -1 ) Figure S2. VOC mass accumulation (in grams) with respect to time (in hours) showing the linear absorption kinetics of the dosimeter for VOC target concentrations of (a) 1100 µg L -1, (b) 116 µg L -1 and (c) 16.9 µg L -1 in water. 54 S9

10 55 Table S3. Measured concentrations of VOCs in water 56 Compounds Target concentration level (µg L -1 ) DCA 18.0 (±2.0) (±14.5) (±88.7) BZN 12.8 (±1.8) (±13.9) (±93.6) TCE 15.4 (±2.0) (±20.5) (±101.1) TOL 14.9 (±2.4) (±18.5) (±120.8) TCA 16.4 (±2.6) (±15.3) (±74.2) PCE 15.5 (±2.5) (±21.9) (±171.3) CBZ 19.9 (±2.7) 97.1 (±13.5) (±90.3) EBZ 16.7 (±1.4) (±18.6) (±100.4) PXY 15.6 (±1.7) (±20.7) (±128.8) TMB 23.1 (±1.6) (±22.9) (±124.1) DCB 17.8 (±1.6) (±20.8) (±136.8) Average 16.9 (±2.8) 116 (± 8.8) (±162) *Standard deviations resulted from 7 time point measurements (from 2 to 72 hours) VOC concentrations in water were aimed to be set consistently at 10, 100 and 1000 µg L -1. The actual concentrations in water are, however, not accurately at the target levels, hence the measured water concentrations listed in Table S3 are used for all the calculations and discussions involved. On the average, the actual VOC concentrations in water are accurately at 16.9 (±2.8), 116 (±9) and 1100 (±162) µg L -1. S10

11 62 S5. Diffusion of VOCs The equation used to calculate D air (in cm 2 s -1 ) is based on the empirical equation formulated by Fuller et al. 2 : 65 D air = 10 3 T 1.75 [(1/M p V 1/3 air air ) + (1/M )] + V 1/3 i i 2 1/2 (S2) 66 where T is the absolute temperature (in K), M air is the average molar mass of air (28.97 g mol -1 ), 67 M i is the chemical s molar mass (in g mol -1 ), p is the gas phase pressure (atm), V air is the average molar volume of the gases in air (20.1 cm 3 mol -1 ), and volume (in cm 3 mol -1 ). V i is the chemical s molar 70 The equation for the diffusivity in water D w (in cm 2 s -1 ) is modified by Hayduk and Laudie 2 : 71 D w = (S3) η V i where η is the solution viscosity in centipoise (10-2 g cm -1 s -1 ) at the temperature of interest, and V i is the chemical s molar volume (in cm 3 mol -1 ). The effective diffusion coefficient 3 is 74 D e m = D w ε (S4) where D w is the diffusion coefficient in water (in L 2 t -1 ), ε is the porosity of the ceramic material and m is the Archie s law of exponent. The values for ε and m are taken from Martin et al. (2003) S11

12 79 80 Figure S3. SEM images of the ceramic tube made up of alumina, showing the solid surface of 81 the ceramic with intermittent cracks and pores. The surface was polished with a 82 diamond suspension SEM Sample preparation: 85 A piece of solid ceramic tube was annealed at 200 C for 5 minutes to remove any moisture and 86 organic impurities. A 1-micron diamond suspension was used to polish the ceramic surface and 87 then cleaned through ultrasonication. The specimen was coated by sputtering with platinum for seconds and then analyzed using FE-SEM JSM6700F from Jeoul company. 89 S12

13 90 S6. Effect of Ionic Strength 91 Table S4. Percent mass increase showing the effect of the ionic strength VOC NaCl concentration (M) DCA 20% 31% 22% 30% BZN 29% 38% 10% 13% TCE 14% 23% 9% 49% TOL 22% 27% 12% 56% TCA 26% 33% 0% 23% PCE 28% 35% 6% 36% CBZ 14% 18% 27% 74% EBZ 7% 12% 29% 88% PXY 4% 7% 35% 97% TMB 33% 26% 88% 160% DCB 9% 7% 43% 100% Values are the average of 4 replicates Table S5. Henry s constant at different ionic strength concentration (mol L -1 ) calculated from the Setchenow constant (k s ). VOCs k s H DCA BZN a TCE b TOL c PCE d CBZ EBZ PXY TMB DCB Literature values of k s from Peng and Wan (1998) at 20 C: a 0.202, b 0.224, c 240, d S13

14 96 97 S6. Model derivation for the diffusion coefficients and Henry s constants in various environmental conditions 98 S6.1 Ionic Strength When the ionic concentrations are not negligible, the VOC concentration C is expressed in terms of its activity a such that 101 a = γ (S5) VOC C VOC where γ is the activity coefficient, which measures the degree of non-ideality of the VOC solution in the presence of ions. Peng and Wan (1998) used an empirical equation to relate the activity coefficient of the salt ions with the Setchenow coefficient k s and ionic strength µ: 105 logγ = k µ (S6) s Since the mass accumulation of the VOCs in the dosimeter is affected by the ionic strength, the concentrations in Equation 4 are expressed in terms of the activity, 108 M t ( γ C ) 2πHDtL VOC = (S7) ln(b/a) which goes back to the original equation multiplied by the activity coefficient. Thus, the modelled HD in the presence of a non-negligible ionic concentration is then expressed as 111 ( ) modeled γ( HD) kinetic HD = (S8) S6.2 Effect of Dissolved Organic Matter S14

15 In the presence of dissolved organic matter, the total concentration of VOCs in the solution is the sum of the free VOC concentration and the DOM-bound VOC concentration, 116 C VOC, tot = C VOC, free + C VOC,DOC bound (S9) 117 The DOM-bound concentrations is 118 C VOC, DOM bound = C VOC, free * K d * C DOM * 10-6 (S10) where C VOC, free and C DOM are the concentrations of the freely dissolved VOCs and the concentration of the DOM, respectively, and K d is the linear partitioning coefficient of the VOCs to DOC in L/kg. The value of K d can be estimated from the octanol-water partitioning coefficient (K ow ) by extrapolation from the single-parameter linear free energy relationships obtained from the literature 4 for monoaromatic hydrocarbons BZN, TOL, EBZ, PXY, and TMB (log K oc = 0.84 log K ow 0.28, with R 2 =0.96) and for halogenated hydrocarbons DCA, TCE, TCA, PCE, CBZ, and DCB (log K oc = 0.94 log K ow 0.43 with R 2 = 0.98) In the presence of DOM, the actual concentration of the VOC is calculated by combining equations S5 and S6, 129 C VOC, free = C VOC, total /(1 + K d * C DOC * 10-6 ) (S11) Using this concentration to fit into Equation 4, the kinetic mass accumulation of the VOCs with dissolved organic matter can be expressed as, 132 M t 2πHDtLC = ln(b/a) VOC, total 1+ K d *C 1 DOM *10 6 (S12) S15

16 133 Hence, the modelled HD becomes, HD (S13) ( ) ( ) modelled= HD kinetic 6 1+ Kd *CDOM * S6.3 Effect of Temperature The effect of temperature on the diffusion of the VOCs through the void air is described by the empirical relation described by Fuller et al. (Equation S2): 139 D air = 10 3 T 1.75 [(1/M p V 1/3 air air ) + (1/M )] + V 1/3 i i 2 1/2 (S2) 140 Henry s constant can be obtained by rearranging Equation 6, 141 B A T H = 10 (S14) 142 Hence, the modeled HD is described by the following equation, considering the tortuosity. 143 B A 1.75 ( ) = T 3 air i HD τ modeled T [(1/ M 1/3 p V air + V ) + (1/ M )] 1/3 i 2 1/ 2 (S15) The overall modelled HD equation considering the ionic strength, DOM and temperature is the combination of equations S4, S9 and S12: 146 B A /2 T [(1/M ) + (1/M )] 1 modeled 1/ Kd *CDOM *10 + i ( HD) 10 T 3 air i = 10 τ γ p 1/3 Vair + V (S16) S16

17 147 S7. Field Sampling Results (a) (b) Figure S4. (a) The ceramic dosimeter is enclosed loosely in a mesh cage and (b) attached through nylon wire to be immersed into the groundwater well Table S6. Water quality of samples Temp C Conductivity (ms cm -1 ) Ionic Strength (mol L -1 ) ph DO (mg L -1 ) E Table S7. Average concentrations from dosimeter extracts 1 at 2 different depths Depth, m Average C w, Well Average C w, mg L -1 mg L -1 (±SD) Solvent extracted C w, mg L -1 (±SD) DCA (7.4) (1.53) S17

18 TCE (9.7) 7.76 (0.21) TOL (5.6) 1.00 (0.54) PCE (1.6) 0.91 (0.13) CBZ (0.45) 0.63 (0.25) EBZ (16.3) (2.10) PXY (56.7) (5.95) S8. Uptake rates by the ceramic dosimeter The sampling rate of the VOCs in the solid ceramic dosimeter is on the average 0.98 ml day -1 which is comparably lower than uptake rates from porous ceramic dosimeters in literature. The rate, in ml day -1, can be calculated using the equation S17 which is derived from equation 6: 163 2πHDceramic L R= (S17) ln ( b / a) The equation S17 shows that sampling rates can be controlled by varying the length as well as the inner and outer diameters of the ceramic tube considering the HD ceramic parameter. Longer samplers will have higher sampling rates. In general, ceramic dosimeters have lower sampling rates compared to other passive samplers which can accumulate in liters per day. The low sampling rate of the ceramic dosimeter allows longer sampling time which is suitable for S18

19 monitoring concentrations even on relatively stationary environments such as groundwater over long periods of time. 171 Table S8. Uptake rates of VOCs by the ceramic dosimeter VOCs Uptake Rate (ml day -1 ) 172 DCA 0.37 BZN 0.76 TCE 1.10 TOL 1.06 TCA 0.22 PCE 1.89 CBZ 0.98 EBZ 1.29 PXY 1.15 TMB 1.28 DCB 0.69 Average (± Standard deviation) 0.98 (±0.46) 173 S9. Standard deviations of the obtained diffusion coefficient in ceramic 174 Table S9. Calculated diffusion coefficients at various concentrations (16.9 to 1100 µg L -1 ). VOCs D ceramic ( m 2 s -1 ) a 1100 µg L µg L µg L -1 Average ( m 2 s -1 ) b DCA 1.60 (0.23) 2.74 (1.37) 2.44 (0.51) 2.26 (0.59) BZN 1.25 (0.23) 1.18 (0.34) 0.67 (0.26) 1.04 (0.32) TCE 1.06 (0.20) 1.02 (0.25) 0.59 (0.19) 0.89 (0.26) TOL 1.33 (0.33) 1.28 (0.26) 1.29 (0.66) 1.30 (0.02) TCA 1.75 (0.36) 2.11 (0.64) 2.19 (0.85) 2.02 (0.23) S19

20 PCE 0.78 (0.30) 0.89 (0.29) 0.99 (0.27) 0.89 (0.10) CBZ 1.89 (0.60) 1.88 (0.48) 2.58 (0.99) 2.12 (0.40) EBZ 1.22 (0.54) 1.09 (0.27) 1.66 (0.76) 1.32 (0.30) PXY 1.31 (0.61) 1.08 (0.30) 1.27 (0.30) 1.22 (0.12) TMB 1.01 (0.70) 0.93 (0.27) 2.20 (0.98) 1.38 (0.71) DCB 1.71 (1.09) 1.43 (0.48) 1.76 (0.62) 1.64 (0.18) Average 1.36 (0.35) 1.42 (0.58) 1.60 (0.70) 1.46 (0.49) a Standard deviations enclosed in parenthesis are from 7 data points b Standard deviations enclosed in parenthesis are from the 3 averaged values 178 References: 179 (1) Lide, D. R. CRC Handbook of Chemistry and Physics. 2003, (2) Schwarzenbach, R.; Gschwend, P. M.; Imboden, D. Environmental Organic Chemistry, 2nd Ed.; John Wiley & Sons: New Jersey, (3) Martin, H.; Patterson, B. M.; Davis, G. B.; Grathwohl, P. Field trial of contaminant groundwater monitoring: Comparing time-integrating ceramic dosimeters and conventional water sampling. Environ. Sci. Technol. 2003, 37 (7), (4) Nguyen, T. H.; Goss, K.; Ball, W. P. Polyparameter Linear Free Energy Relationships for Estimating the Equilibrium Partition of Organic Compounds between Water and the Natural Organic Matter in Soils and Sediments. Environ. Sci. Technol. 2005, 39 (4), S20