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Leaves as an Indicator of Exposure to Airborne Volatile Organic Compounds

 

Table 1.  The Properties of Analytes and Surrogates Used for Quantitation.
 

retention timea
(min)

quantitation ion
secondary ion(s)
 relative volatility
(aKOA)b
surrogates    
 fluorobenzene 9.91 96
70
 690
 1,4-difluorobenzene 10.06 114
63
 860
 toluene-d8 13.02 98
100, 99
 2200
 1,2-dibromoethane-d4 15.44 111
113
 5000
 o-xylene-d10 17.81 98
116
 8400
 bromobenzene-d5 20.05 161
163, 82
 12000
 1,2-dichlorobenzene 22.65 152
150
 22000
 1,2,4-trichlorobenzene 24.75 183
185
 41000
 naphthalene-d8 25.03 136
108
 57000
analytes    
 benzene 9.45 78
77
 460
 toluene 13.18 91
92
 2100
 tetrachloroethene 14.6 166
164
 6100
 ethylbenzene 16.79 106
91
 5000
 m,p-xylene 16.97 106
91
 4500
 1,4-dichlorobenzene 22.14 146
148
 20000
 naphthalene 25.07 128
108
 41000

a Retention times were determined using 60-m x 0.53-mm i.d., 3.0-µm film thickness VOCOL column.  Temperature program was: 3 min at 10 °C, 50 °C/min ramp to 40 °C; 5 °C/min ramp to 120 °C; 20 °C/min to  220 °C and held at 220 °C to end of run.
b Relative volatility values from ref 7.

Table 2. Physical Properties of Leaves.
  Dry-weight density surface diameter length
leaf (%) g/cm3 cm2/g cm cm
grass 22.7 0.82a 173 NAb 2
mock orange 34.7 0.90c 66 NA 2
pine 48.9 0.90c 61 0.81 NA
rosemary 21.7 0.90c 64 0.143 NA

a Value from ref 9.
b Data not required to determine laminar flow boundary.
c Estimated values.

Table 3. Bioconcentration Factors and Enthalpy of Phase Change for VOCs in Leaves.
    grass mock orange pine rosemary
    BCFa DHPA
kJ/mol		 BCF DHPA
kJ/mol		 BCF DHPA
kJ/mol		 BCF DHPA
kJ/mol
  Hvbb Ic IId I II I II I II
compound kJ/mol avg dev avg deve avg dev avg dev avg dev avg dev avg dev avg dev
benzene 30.7 NAf 136 32.7 0.5(3) NA 150 31.0 0.3(3) NA 98 35.4 2.6(6) NA 206 35.3 2.9(6)
toluene 33.2 200 70 244 32.7 1.5(7) 590 230 315 29.9 0.6(4) 2300 1800 574 34.1 1.5(5) 14000 6000 3056 38.1 2.0(5)
tetrachloroethene 34.7 220 190 190 31.9 6.6(2) 350 320 382 36.0 (1) 440 80 485 35.6 0.5(3) 5400 8100 1648 37.3 1.8(3)
ethylbenzene 35.6 350 240 235 33.6 2.0(6) 1600 900 954 31.1 1.8(4) 1800 1300 2093 37.9 1.2(5) 11000 7000 2158 37.3 3.2(6)
m,p-xylenes 35.7 420 200 299 32.1 0.5(3) 2200 1500 1089 33.2 3.8(5) 1300 1100 1978 39.0 0.9(4) 10000 70000 2052 37.3 2.4(8)
1,4-dichlorobenzene 38.8 2700 300 2731 29.4 0.2(3) 5200 3100 2856 32.8 1.9(5) 6200 NA 5995 38.8 1.8(4) NA 7441 35.3 1.8(2)
naphthalene 38.1 5800 600 6792 32.9 1.0(6) 39000 22000 14472 34.9 1.2(5) 13000 10000 17446 37.5 1.1(2) 66000 34000 15875 36.0 2.5(7)

a Bioconcentration factor for analyte (ng/kg leaf dry weight to ng/L air) for 20 °C
b Enthalpy of vaporization at the compound boiling point from ref 21
c BCF reported in ref 7
d BCF determined in this study
e One sigma deviation. The number of replicates to determine DHPA are in parenthesis.
Value is blank for results based on one determination
f Not determined

Table 4. Physical Properties for Volatile and Semivolatile Compounds and their Enthalpy of Phase Change between Air and Grass.
Compound Log BCFa
25 °C		 log KOAb
25 °C		 DHvapc
(kJ/mol)		 DHPAd
(kJ/mol)
benzene 2.04 2.59 39.7 32.7
tetrachloroethene 2.17 2.61 38.0 31.9
toluene 2.28 3.17 33.8 32.7
m,p-xylene 2.36 3.65 42.2 32.1
ethylbenzene 2.25 3.59 49.0 33.6
1,4-dichlorobenzene 3.29 4.03 42.5 29.4
naphthalene 3.63 4.21 54.2 32.9
PCB 4 + 10e 4.73 6.56 69.7 54.2
PCB 8 + 5 4.92 6.98 72.2 65.4
PCB 18 5.25 7.12 75.4 70.6
PCB 16 + 32 5.46 7.18 75.4 64.5
PCB 31 + 28 5.58 7.61 77.9 82.4
PCB 52 5.86 7.73 80.8 86.6
PCB 44 6.12 7.78 81.0 83.7
PCB 71 + 64 6.08 7.89 81.0 90.0
PCB 95 6.24 8.04 84.2 91.8
PCB 84 + 90 + 101 6.54 8.23 85.8 97.8
PCB 110 6.94 8.58 86.6 107.2
PCB 149 7.01 8.68 89.8 108.9
PCB 153 7.31 9.09 91.4 116.7
PCB 158 + 138 7.59 9.15 92.1 123.3
PCB 187 7.52 9.25 94.0 117.2
PCB 180 8.11 9.72 96.5 128.8
PCB 202 7.51 9.28 92.9 108.8
PCB 203 + 196 8.33 9.91 100.4 137.5

a Bioconcentration factor for analyte (ug/kg leaf dry weight to ug/L air). The first seven compound
values are from this study and the remainder from ref 10
b The first seven octanol air partition coefficients are from ref 15. The remainder are from ref 10
c The first seven heat of vaporization values are from ref 21. The remainder are from ref 10
d The first seven enthalpy of phase change between air and grass were from this study, the remainder  from ref 10
e IUPAC number

Table 5. Predicted relative concentrations of VOCs in pine and grass three hours after maximum air concentrations under varying conditions.
- T wind Benzene toluene tetrachloroethene ethylbenzene m,p-xylene 1,4-dichlorobenzene naphthalene
leaf (°C) (m s-1) Ia IIb I II I II I II I II I II I II
pine 0 to 10 0.5 0.78 0.02 1.13 0.59 1.14 0.72 1.11 0.86 1.06 0.93 1.11 0.87 1.140 0.83
  0 to 10 1.0 0.74 0.00 1.09 0.48 1.14 0.63 1.13 0.81 1.08 0.90 1.13 0.82 1.16 0.77
  0 to 10 5.0 0.73 0.00 0.95 0.19 1.04 0.36 1.14 0.62 1.13 0.80 1.14 0.65 1.12 0.55
  20 to 30 0.5 0.75 0.00 0.96 0.20 1.04 0.35 1.13 0.60 1.13 0.78 1.14 0.63 1.11 0.54
  20 to 30 1.0 0.76 0.00 0.89 0.10 0.98 0.23 1.09 0.49 1.14 0.70 1.10 0.52 1.06 0.42
  20 to 30 5.0 0.78 0.00 0.77 0.01 0.82 0.04 0.96 0.20 1.08 0.45 0.96 0.23 0.89 0.14
grass 0 to 10 0.5 0.73 0.00 1.05 0.39 1.01 0.30 1.02 0.33 0.94 0.18 0.77 0.03 1.09 0.48
  0 to 10 1.0 0.73 0.00 0.99 0.27 0.94 0.18 0.95 0.21 0.87 0.09 0.72 0.01 1.02 0.36
  0 to 10 5.0 0.75 0.00 0.83 0.05 0.79 0.02 0.80 0.03 0.74 0.00 0.69 0.00 0.83 0.10
  20 to 30 0.5 0.77 0.00 0.86 0.06 0.82 0.03 0.82 0.04 0.77 0.01 0.71 0.00 0.87 0.12
  20 to 30 1.0 0.78 0.00 0.80 0.02 0.77 0.01 0.77 0.01 0.74 0.00 0.71 0.00 0.79 0.05
  20 to 30 5.0 0.79 0.00 0.74 0.00 0.74 0.00 0.73 0.00 0.73 0.00 0.73 0.00 0.68 0.00

a Concentration of analyte in air maximizes at 7:00 a. m. and gradually minimizes to 1/10 of maximum concentration at noon. The resultant value is the fraction of analyte that remains at 10:00 a. m.
b Concentration of analyte in air maximizes at 7:00 a. m. and immediately becomes negligible. The resultant value is the fraction of analyte that remains at 10:00 a. m.

Figure 1

Figure 1.  Log BCF at 20 °C vs log KOA at 25 °C for lipophilic compounds in grass.

Figure 2

Figure 2.  Log DHPA vs DHvap for lipophilic compounds in grass.

Figure 3

Figure 3. The effects of wind velocity on the concentration of toluene in pine needles respective to its concentration at 7:00 a.m. when the content of toluene in air is greatest. The temperature increases from 0 to 10 °C over the 5-h period.  Air(I) is a trend where the toluene content in air steadily decreases from a maximum at 7:00 a.m. to 1/10 maximum at noon.  Air(II) is a condition where after the 7:00 a.m. maximum the content of toluene in air is negligible at 8:00 a.m.

 

 

 


 

National Exposure Research Laboratory
Author:  Mike Hiatt / Email:  Hiatt.Mike@epa.gov
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