Holton et al. (203) Evaluation of Selected Environmental Factors at a Vapor Intrusion Study Site Chase Holton Hong Luo Yuanming Guo Paul Dahlen Kyle Gorder Erik Dettenmaier Paul C. Johnson
Holton et al. (203) Outline Background What do we know? ASU VI Research House (SDM) Results What can we learn from environmental factors? Conclusions Acknowledgments Questions
Holton et al. (203) Background What do we know? Temporal variability is present in indoor air data with active and inactive periods Most would agree the variation is connected with environmental factors What questions remain? Can we identify conditions under which vapor intrusion becomes active? Can environmental factors help narrow the assessment period?
Holton et al. (203) Hill AFB Off-Site Plumes Hill AFB Situation: About 3000 homes above dissolved CHC plumes (0 00 ug/l; mean about 30 ug/l) About half of the home-owners have opted for indoor monitoring at least once
Sun Devil Manor [Layton, UT] Source: GW plume with 0-60 μg/l,- DCE and TCE; GW deep gradient 0.23 ft/ft across house; Geology: silty clay with sand stringers Holton et al. (203)
Holton et al. (203) + Multi-level soil gas and groundwater sampling points Subsurface Monitoring Network Indoor air monitoring (VOCs, radon) Differential pressures, soil moisture, soil temperature Weather (wind, barometric pressure, rainfall, outdoor temp) HVAC operation, indoor T, exchange rate (SF 6 )
Sun Devil Manor Highly customized monitoring network: Thermal desorption tubes with auto-sampler SRI GCs with PDD and ECD (TO-7) Meteorological Station Sensor data acquisition system HAPSITE GC-MS www.inficon.com Durridge RAD7 Holton et al. (203)
Concentration in Indoor Air (ppb v ) Long Term: Seasonal Changes 00 Fall Winter Spring Summer Fall Winter Spring Summer 0 Portable GC/MS (-min sample) Thermal desorption tubes (4-h composite) 0. 0.0 60 20 80 240 300 360 420 480 540 600 660 720 Oct. 4 th, 200 Time (d) Aug. 4th, 202 Holton et al. (203)
Combined 24-h Average Indoor Air TCE [ppb v ] Combined 24-h Average Indoor Air TCE [ppb v ] 24-h Average dp at 5-SS [Pa] 0 0. P: Sub-slab to Indoor Air 24-h Ave. TCE dp: 5-SS to Indoor Air 0.0-2.0 50 0 70 230 290 350 40 470 530 590 650 Oct. 4 th, 200 Time [d] May 25 th, 202 0 2.0.5.0 0.5 0.0-0.5 -.0 -.5 0. 0.0 -.0-0.5 0.0 0.5.0 24-h Average dp at 5-SS [Pa] Holton et al. (203)
Combined 24-h Average Indoor Air TCE [ppb v ] Combined 24-h Average Indoor Air TCE [ppb v ] 24-h Average Outdoor Barometric Pressure[mbar] Holton et al. (203) Outdoor Barometric Pressure 0 24-h Ave. TCE Outdoor Barometric Pressure 875 860 0. 845 0.0 830 50 0 70 230 290 350 40 470 530 590 650 Oct. 4 th, 200 Time [d] May 25 th, 202 0 0. 0.0 830 835 840 845 850 855 860 865 870 875 24-h Average Outdoor Barometric Pressure[mbar]
Combined 24-h Average Indoor Air TCE [ppb v ] Combined 24-h Average Indoor Air TCE [ppb v ] 24-h Average Outdoor-to-Indoor dp[pa] 0 0. P: Outdoor to Indoor Air 24-h Ave. TCE dp: Outdoor to Indoor Air 3 2 0 - -2 0.0 0-3 50 0 70 230 290 350 40 470 530 590 650 Oct. 4 th, 200 Time [d] May 25 th, 202 0. 0.0-3 -2-0 2 3 24-h Average Outdoor-to-Indoor dp [Pa] Holton et al. (203)
24-hrAverage Indoor Air TCE [ppb v ] 24-hr Average Indoor Air TCE [ppb v ] Holton et al. (203) Wind Speed [mph] 0 0. Wind Speed 24-hr Ave. TCE 24-hr Ave. Peak Wind Speed 25 20 5 0 5 0.0 0 50 0 70 230 290 350 40 470 530 590 650 Oct 4th, 200 Time [d] May 25 th, 202 0 0. 0.0 0 5 0 5 20 25 Wind Speed [mph]
TCE Concentration in Indoor Air (ppb v ) 24-hr Average Temperature (Indoor - Outdoor) [ C] T (Indoor Outdoor) 00 0 Portable GC/MS (-m sample) Thermal desorption tubes (4-h composite) dt(indoor-outdoor) 35 30 25 20 5 0 5 0. 0-5 -0 0.0-5 60 20 80 240 300 360 420 480 540 600 660 720 Oct. 4 th, 200 Time (d) Aug. 4 th, 202 Holton et al. (203)
TCE Concentration in Indoor Air [ppb v ] T (Indoor Outdoor) 00 Thermal desorption tubes (4-h composite) Portable GC/MS (-min sample) 0 0. 0.0-0 -5 0 5 0 5 20 25 30 35 Temperature (Indoor Outdoor) [ C] Holton et al. (203)
TCE Concentration in Indoor Air [ppb v ] T (Indoor Outdoor) 00 Thermal desorption tubes (4-h composite) Portable GC/MS (-min sample) 0 0. -0-5 0 5 0 5 20 25 30 35 Temperature (Indoor Outdoor) [ C] Holton et al. (203)
Daily Average Indoor-Outdoor Temperature [C] Daily Average TCE Concentration [ppb v ] Narrowing the Assessment Period? Summer Fall Winter Spring Summer Fall Winter Spring Summer 35 Indoor - Outdoor Temperature Difference Daily Average Concentration 0 30 25 20 5 0 5 0. 0-5 -0 Aug 5, 200 (08:00) 0 00 200 300 400 500 600 700 Time [d] 0.0 August 4, 202 Holton et al. (203)
TCE Conc. in Indoor Air (ppb v ) TCE Conc. in Indoor Air (ppb v ) Short-term: Daily Variation Hapsite Data TCE Concentration in Indoor Air (ppb v ) 0. 0.0-27 -26-25 Time (d) -24-23 -22 07/8/200 07/23/200 TCE Concentration in Indoor Air (ppb v ) TD Tube Data 0. 0.0 444 446 448 Time (d) 450 452 /2/20 454 /02/20 Holton et al. (203)
TCE Concentration in Indoor Air (ppb v ) Temperature ( C) (In-Out) Short-term: Daily Variation TD Tube Data Temp (In-Out) /08/20 2:38 am /0/20 3:32 am 30 25 20 0. 5 /05/20 0:37 pm 0 5 0.0 0 444 445 446 447 448 449 450 45 452 453 454 /02/20 Time (d) /2/20 Holton et al. (203)
Holton et al. (203) January 0 th, 20 Pressure at L.5: Sub-slab to Indoor [Pa] 24-hr Average Maximum Minimum IA -0.8 Pa 0.22 Pa -0.80 Pa SS IA SS IA SS Pressure: Outdoor to Indoor [Pa] OA IA OA IA 0.268 Pa -.85 Pa.33 Pa OA IA Outdoor barometric pressure [mbar] 858.4 mbar 862.3 mbar 853.6 mbar Wind speed [mph].25 mph 8.75 mph 0 mph Differential temperature (Indoor Outdoor) [ C] 26.7 C 30.6 C 20.5 C
Holton et al. (203) January 0 th, 20 Highest 24-h average TCE concentration in indoor air (with 2 or more samples) Date: /0/20 Number of Samples 24-h Average TCE Conc. [ppb v ] Maximum TCE Conc. [ppb v ] Minimum TCE Conc. [ppb v ] 9 2.4 6.3 N/D
Number of Samples Holton et al. (203) Sampling when it s cold? 400 200 Samples above 0.38 ppbv Sample total 70 000 869 800 600 748 628 70 400 340 200 0 23 33 55 46 0 7 7 6 0 5 5 0 0 5 5 20 20 25 25 30 30 35 Temperature (Indoor Outdoor) [ C]
Holton et al. (203) Conclusions Indoor air concentrations of TCE vary seasonally Larger range of TCE concentration (0-2 - 0 ppb v ) during colder periods Greater average concentration during colder periods Wind speed, outdoor barometric pressure, and differential pressures do not show strong relationships with indoor air concentration at a 24-hour resolution Differential temperature monitoring may help narrow the assessment period Does not guarantee detection of higher concentrations Diurnal changes in VI signal may be related to daily variation in differential temperature during periods of colder temperature
Holton et al. (203) Acknowledgements Special thanks to SERDP Hill Air Force Base
Holton et al. (203) Questions? Comments?