Effect of hydrofracking fluid on colloid transport in the unsaturated zone

Wenjing Sang, Cathelijne R. Stoof, Wei Zhang, Veronica L. Morales, Bin Gao, Robert W. Kay, Lin Liu, Yalei Zhang, Tammo S. Steenhuis

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13 Citations (Scopus)
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Abstract

Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydrofracking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydrofracking fluids, which return to the surface during hydrofracking, are common causes of environmental contamination. Since the chemistry of hydrofracking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequently injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While <5% of initial colloids were released by flushing with deionized water, 32–36% were released by flushing with flowback fluid in two distinct breakthrough peaks. These peaks resulted from 1) surface tension reduction and steric repulsion and 2) slow kinetic disaggregation of colloid flocs. Increasing the flow rate of the flowback fluid mobilized an additional 36% of colloids, due to the expansion of water filled pore space. This study suggests that hydrofracking fluid may also indirectly contaminate groundwater by remobilizing existing colloidal pollutants.
Original languageEnglish
Pages (from-to) 8266–8274
Number of pages9
JournalEnvironmental Science & Technology
Volume48
Issue number14
DOIs
Publication statusPublished - 6 Jun 2014

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Colloids
colloid
vadose zone
Fluids
fluid
Deionized water
flushing
Flow rate
Hydraulic fracturing
pollutant
surface tension
Hazardous materials spills
Shale
pore space
effect
water
Minerals
Surface tension
mobilization
microscopy

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Sang, W., Stoof, C. R., Zhang, W., Morales, V. L., Gao, B., Kay, R. W., ... Steenhuis, T. S. (2014). Effect of hydrofracking fluid on colloid transport in the unsaturated zone. Environmental Science & Technology, 48(14), 8266–8274. https://doi.org/10.1021/es501441e
Sang, Wenjing ; Stoof, Cathelijne R. ; Zhang, Wei ; Morales, Veronica L. ; Gao, Bin ; Kay, Robert W. ; Liu, Lin ; Zhang, Yalei ; Steenhuis, Tammo S. / Effect of hydrofracking fluid on colloid transport in the unsaturated zone. In: Environmental Science & Technology. 2014 ; Vol. 48, No. 14. pp. 8266–8274.
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Sang, W, Stoof, CR, Zhang, W, Morales, VL, Gao, B, Kay, RW, Liu, L, Zhang, Y & Steenhuis, TS 2014, 'Effect of hydrofracking fluid on colloid transport in the unsaturated zone', Environmental Science & Technology, vol. 48, no. 14, pp. 8266–8274. https://doi.org/10.1021/es501441e

Effect of hydrofracking fluid on colloid transport in the unsaturated zone. / Sang, Wenjing; Stoof, Cathelijne R.; Zhang, Wei; Morales, Veronica L.; Gao, Bin; Kay, Robert W.; Liu, Lin; Zhang, Yalei; Steenhuis, Tammo S.

In: Environmental Science & Technology, Vol. 48, No. 14, 06.06.2014, p. 8266–8274.

Research output: Contribution to journalArticle

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AU - Sang, Wenjing

AU - Stoof, Cathelijne R.

AU - Zhang, Wei

AU - Morales, Veronica L.

AU - Gao, Bin

AU - Kay, Robert W.

AU - Liu, Lin

AU - Zhang, Yalei

AU - Steenhuis, Tammo S.

PY - 2014/6/6

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N2 - Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydrofracking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydrofracking fluids, which return to the surface during hydrofracking, are common causes of environmental contamination. Since the chemistry of hydrofracking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequently injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While <5% of initial colloids were released by flushing with deionized water, 32–36% were released by flushing with flowback fluid in two distinct breakthrough peaks. These peaks resulted from 1) surface tension reduction and steric repulsion and 2) slow kinetic disaggregation of colloid flocs. Increasing the flow rate of the flowback fluid mobilized an additional 36% of colloids, due to the expansion of water filled pore space. This study suggests that hydrofracking fluid may also indirectly contaminate groundwater by remobilizing existing colloidal pollutants.

AB - Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydrofracking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydrofracking fluids, which return to the surface during hydrofracking, are common causes of environmental contamination. Since the chemistry of hydrofracking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequently injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While <5% of initial colloids were released by flushing with deionized water, 32–36% were released by flushing with flowback fluid in two distinct breakthrough peaks. These peaks resulted from 1) surface tension reduction and steric repulsion and 2) slow kinetic disaggregation of colloid flocs. Increasing the flow rate of the flowback fluid mobilized an additional 36% of colloids, due to the expansion of water filled pore space. This study suggests that hydrofracking fluid may also indirectly contaminate groundwater by remobilizing existing colloidal pollutants.

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Sang W, Stoof CR, Zhang W, Morales VL, Gao B, Kay RW et al. Effect of hydrofracking fluid on colloid transport in the unsaturated zone. Environmental Science & Technology. 2014 Jun 6;48(14): 8266–8274. https://doi.org/10.1021/es501441e