TY - JOUR

T1 - A novel, direct-push approach for detecting sulfidated nanoparticulate zero valent iron (S-nZVI) in sediments using reactive and non-reactive fluorophores

AU - Reischer, Markus

AU - Christensen, Anders G.

AU - Weber, Klaus

AU - Tobler, Dominique J.

AU - Dideriksen, Knud

N1 - Funding Information: We warmly thank Weichao Sun and Anna-Maria Tilg for helping with the OIP in-situ experiments and Marco Mangayayam for providing the presynthesis CMC stabilized S-nZVI. We are grateful for the kind assistance provided by Kevin A. Beyer and Leighanne C Gallington at the APS beam line 11 ID-B. This research was funded by Metal-Aid Innovative Training Network (ITN) , supported by a grant from the European Commission's Marie Skłowdowska Curie Actions program under project number 675219 . Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences , under Contract No. DE-AC02-06CH11357 . Funding Information: We warmly thank Weichao Sun and Anna-Maria Tilg for helping with the OIP in-situ experiments and Marco Mangayayam for providing the presynthesis CMC stabilized S-nZVI. We are grateful for the kind assistance provided by Kevin A. Beyer and Leighanne C Gallington at the APS beam line 11 ID-B. This research was funded by Metal-Aid Innovative Training Network (ITN), supported by a grant from the European Commission's Marie Sk?owdowska Curie Actions program under project number 675219. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Publisher Copyright: © 2021 The Authors

PY - 2021/12

Y1 - 2021/12

N2 - Injection of microparticulate and nanoparticulate zero valent iron has become a regularly used method for groundwater remediation. Because of subsurface inhomogeneities, however, it is complicated to predict the ZVI transport in the subsurface, meaning that tools capable of determining its distribution after injection are highly useful. Here, we have developed a new direct-push based technique, which combines fluorescent and visible imaging, for detection of sulfidized nanoparticulate zero valent iron (S-nZVI) in the subsurface. Laboratory experiments show that the redox sensitive fluorophore riboflavin is rapidly reduced by S-nZVI within 200 s. Because the reduced riboflavin losses its green fluorescence, it can be used as S-nZVI sensitive indicator. Secondly, S-nZVI is black and tints light coloured sediment to a degree that allows detection in images. For quartz sand, 70 mg/kg of S-nZVI can be detected by visible imaging. Based on these results, a new direct-push probe (Dye-OIP) was designed based on Geoprobe's Optical Image Profiler (OIP), which was equipped with a fluorophore injection port below the OIP-unit. The injectant consisted of the redox active riboflavin mixed with the redox inactive fluorophore rhodamine WT, which fluoresces red and was used to verify that the mixture was indeed injected and detectable. Small scale experiments show that the fluorescence of this mixture in S-nZVI amended sand changes within 150 s from green with a hue of ~50 to red with a hue of ~30 when imaged with Dye-OIP. Tests of the Dye-OIP after a S-nZVI injection in a 1 m3 sized tank show that the tool could detect S-nZVI via fluorescence and visible imaging, when S-nZVI concentration was >0.2 mg per g dry sediment. Thus, these novel methods should be able to detect S-nZVI in the subsurface, without relying on infrastructure such as wells. Based on our results, the Dye-OIP could be further improved to make it suitable for regular use in the field.

AB - Injection of microparticulate and nanoparticulate zero valent iron has become a regularly used method for groundwater remediation. Because of subsurface inhomogeneities, however, it is complicated to predict the ZVI transport in the subsurface, meaning that tools capable of determining its distribution after injection are highly useful. Here, we have developed a new direct-push based technique, which combines fluorescent and visible imaging, for detection of sulfidized nanoparticulate zero valent iron (S-nZVI) in the subsurface. Laboratory experiments show that the redox sensitive fluorophore riboflavin is rapidly reduced by S-nZVI within 200 s. Because the reduced riboflavin losses its green fluorescence, it can be used as S-nZVI sensitive indicator. Secondly, S-nZVI is black and tints light coloured sediment to a degree that allows detection in images. For quartz sand, 70 mg/kg of S-nZVI can be detected by visible imaging. Based on these results, a new direct-push probe (Dye-OIP) was designed based on Geoprobe's Optical Image Profiler (OIP), which was equipped with a fluorophore injection port below the OIP-unit. The injectant consisted of the redox active riboflavin mixed with the redox inactive fluorophore rhodamine WT, which fluoresces red and was used to verify that the mixture was indeed injected and detectable. Small scale experiments show that the fluorescence of this mixture in S-nZVI amended sand changes within 150 s from green with a hue of ~50 to red with a hue of ~30 when imaged with Dye-OIP. Tests of the Dye-OIP after a S-nZVI injection in a 1 m3 sized tank show that the tool could detect S-nZVI via fluorescence and visible imaging, when S-nZVI concentration was >0.2 mg per g dry sediment. Thus, these novel methods should be able to detect S-nZVI in the subsurface, without relying on infrastructure such as wells. Based on our results, the Dye-OIP could be further improved to make it suitable for regular use in the field.

KW - Contamination

KW - Fluorescent tracer

KW - Monitoring

KW - Redox indicator

KW - Vitamin B2

KW - Zero valent iron detection

U2 - 10.1016/j.jconhyd.2021.103896

DO - 10.1016/j.jconhyd.2021.103896

M3 - Journal article

C2 - 34695716

AN - SCOPUS:85117722882

VL - 243

JO - Journal of Contaminant Hydrology

JF - Journal of Contaminant Hydrology

SN - 0169-7722

M1 - 103896

ER -