# Injection of Zerovalent Iron Gels for Aquifer Nanoremediation: Lab Experiments and Modeling

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Materials

_{10}), 1.9 μm (d

_{50}), and 3.97 μm (d

_{90}) and are composed of iron (98.55%), oxygen (0.80%), carbon (0.03%), nitrogen (0.01%), and other impurities (0.61%). Their specific surface area per unit of solid volume is 3.16 × 10

^{−6}${\mathrm{m}}^{2}/{\mathrm{m}}^{3},$ and their density is 9760 $\mathrm{kg}/{\mathrm{m}}^{3}$. Guar gum and xanthan gum were both provided by Rantec Corporation (Ranchester, Wyoming, USA) in the form of dry powder. The carboxymethyl cellulose (CMC-2000) was supplied by CHEMPOINT (Maastricht, The Netherlands).

^{3}. Furthermore, to eliminate any residual impurities and colloids, the sand was cleaned through three cycles of washing and sonication with NaOH 0.1 M, tap water, and deionized water.

#### 2.2. Preparation of the mZVI Slurry

#### 2.3. Bulk and Porous Medium Rheology

^{−3}and 1 × 10

^{4}s

^{−1}by means of an Antoon Paar (Graz, Austria) rheometer (MCR302). The gel rheology inside the porous medium was instead characterized through the interpretation of 4 column transport tests (details about the tests are reported in the next section). The interpretation procedure, reported in Figure S1, provided one couple of shear rate and viscosity value for each column test. The graph representing these data represents the fluid rheogram in the porous medium.

#### 2.4. Column Transport Tests

- Pre-conditioning the porous medium with 5 pore volumes (PVs) of deionized water;
- Injecting 10 PVs of iron slurry.

#### 2.5. Radial Transport Test

- 2 PVs pre-conditioning with deionized water;
- 0.8 PVs of iron slurry injection.

#### 2.6. mZVI Transport Model in Radial Geometry

- First site expressing irreversible blocking dynamics: blocking is a physicochemical deposition mechanism that typically happens when particle-particle interactions are strongly repulsive. In this case, the already deposited particles prevent suspended ones from further attachment, and a porous medium saturation can be achieved. The particle deposition rate decreases with increasing ${S}_{Fe,i}$ and goes to zero when the saturation concentration of deposited particles, ${S}_{max}$, is reached [44,49,50].
- Second site expressing irreversible straining dynamics: straining is a physical deposition mechanism due to colloid trapping into small pore throats. Straining is likely to occur when the ratio between the size of the colloid and the sand grain is greater than, or close to, 0.5% [51,52]. In this study, a ${d}_{50,Fe}/{d}_{50,sand}$ of 0.68% was found, suggesting that straining might be a relevant deposition mechanism in this system.

## 3. Results

#### 3.1. Bulk and Porous Medium Rheology

^{−1}that corresponded to the radial model region close to the injection well, where the highest velocities were observed. Such low viscosity values limited the pressure increase during the mZVI injection in the subsoil, reducing the risk of porous medium fracturing and the consequential generation of preferential flow paths. The experimental rheogram of the shear-thinning gel (dots) was fitted against the Ostwald de Waele power-law model (solid line) with a good agreement (Figure 2b). The parameters k and n, obtained from the experimental data fitting, were, respectively, 0.22 Pa∙s

^{n}and 0.52.

#### 3.2. Column Transport Tests and Modeling

_{0}> 0.8). In particular, the concentration data analysis suggested the presence of two concurrent retention mechanisms within the sandy bed: (1) the sigmoidal shape of the breakthrough curves indicates that the particle deposition rate is decreasing over time because of saturation phenomena typical of a blocking deposition mechanism [56,57]; (2) the hyper-exponential shape of the concentration profiles, associated with a maximum outlet concentration lower than C

_{0}, can be instead ascribed to irreversible straining kinetics [45,58]. The kinetic coefficients determined for each test through the inverse fitting of the concentration data are reported in Table S2. A constant value, equal to 0.0027 g

_{Fe}/kg

_{Sand}, was found for the blocking parameter ${S}_{max}$, while a velocity-dependent behavior was observed for ${k}_{a,1}$, ${k}_{a,2}$, and ${\beta}_{str}$. In Figure S3, the values of ${k}_{a,1}$ and ${k}_{a,2}$ in all the tests were reported as a function of $\frac{{v}_{e}}{{d}_{50,sand}}{\eta}_{0}$, while ${\beta}_{str}$ was plotted against the effective velocity $v$. A clear linear trend for the two attachment parameters was found, whereas an exponential correlation of ${\beta}_{str}$ with velocity was instead observed. The fitting of the kinetic coefficient trends against Equations (4) and (5) led to the estimation of the following empirical parameters: ${C}_{a,1}=0.13(-)$, ${C}_{a,2}=0.23(-)$, $\omega =0.13$, $\mathsf{\tau}=364.84\mathrm{s}/\mathrm{m}$.

#### 3.3. Radial Injection of mZVI Particles

## 4. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Tosco, T.; Papini, M.; Viggi, C.; Sethi, R. Nanoscale zerovalent iron particles for groundwater remediation: A review. J. Clean. Prod.
**2014**, 77, 10–21. [Google Scholar] [CrossRef] - Zhao, X.; Liu, W.; Cai, Z.; Han, B.; Qian, T.; Zhao, D. An overview of preparation and applications of stabilized zero-valent iron nanoparticles for soil and groundwater remediation. Water Res.
**2016**, 100, 245–266. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Beryani, A.; Alavi Moghaddam, M.R.; Tosco, T.; Bianco, C.; Hosseini, S.M.; Kowsari, E.; Sethi, R. Key factors affecting graphene oxide transport in saturated porous media. Sci. Total Environ.
**2020**, 698, 134224. [Google Scholar] [CrossRef] [PubMed] - Gallo, A.; Bianco, C.; Tosco, T.; Sethi, R. Zerovalent iron for the remediation of contaminated aquifers. Geoing. Ambient. E Min.
**2018**, 155, 5–16. [Google Scholar] - Bianco, C.; Patiño Higuita, J.E.; Tosco, T.; Tiraferri, A.; Sethi, R. Controlled Deposition of Particles in Porous Media for Effective Aquifer Nanoremediation. Sci. Rep.
**2017**, 7, 12992. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Gillies, G.; Raj, R.; Kopinke, F.D.; Georgi, A. Suspension stability and mobility of Trap-Ox Fe-zeolites for in-situ nanoremediation. J. Colloid Interface Sci.
**2017**, 501, 311–320. [Google Scholar] [CrossRef] [PubMed] - Li, X.-Q.; Elliott, D.W.; Zhang, W.-X. Zero-Valent Iron Nanoparticles for Abatement of Environmental Pollutants: Materials and Engineering Aspects. Crit. Rev. Solid State Mater. Sci.
**2006**, 31, 111–122. [Google Scholar] [CrossRef] - Di Molfetta, A.; Sethi, R. Clamshell excavation of a permeable reactive barrier. Environ. Geol.
**2006**, 50, 361–369. [Google Scholar] [CrossRef] - Crane, R.A.; Scott, T.B. Nanoscale zero-valent iron: Future prospects for an emerging water treatment technology. J. Hazard. Mater.
**2012**, 211–212, 112–125. [Google Scholar] [CrossRef] - Wang, Q.; Qian, H.; Yang, Y.; Zhang, Z.; Naman, C.; Xu, X. Reduction of hexavalent chromium by carboxymethyl cellulose-stabilized zero-valent iron nanoparticles. J. Contam. Hydrol.
**2010**, 114, 35–42. [Google Scholar] [CrossRef] - Gallo, A.; Bianco, C.; Tosco, T.; Tiraferri, A.; Sethi, R. Synthesis of eco-compatible bimetallic silver/iron nanoparticles for water remediation and reactivity assessment on bromophenol blue. J. Clean. Prod.
**2019**, 211, 1367–1374. [Google Scholar] [CrossRef] - Tiraferri, A.; Saldarriaga Hernandez, L.A.; Bianco, C.; Tosco, T.; Sethi, R. Colloidal behavior of goethite nanoparticles modified with humic acid and implications for aquifer reclamation. J. Nanoparticle Res.
**2017**, 19, 107. [Google Scholar] [CrossRef] - Sethi, R.; Di Molfetta, A. Groundwater Engineering: A Technical Approach to Hydrogeology, Contaminant Transport and Groundwater Remediation; Springer International Publishing: Cham, Switzerland, 2019. [Google Scholar]
- Mueller, N.C.; Braun, J.; Bruns, J.; Černík, M.; Rissing, P.; Rickerby, D.; Nowack, B. Application of nanoscale zero valent iron (NZVI) for groundwater remediation in Europe. Environ. Sci. Pollut. Res.
**2012**, 19, 550–558. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Su, C.; Puls, R.W.; Krug, T.A.; Watling, M.T.; O’Hara, S.K.; Quinn, J.W.; Ruiz, N.E. A two and half-year-performance evaluation of a field test on treatment of source zone tetrachloroethene and its chlorinated daughter products using emulsified zero valent iron nanoparticles. Water Res.
**2012**, 46, 5071–5084. [Google Scholar] [CrossRef] [PubMed] - Velimirovic, M.; Tosco, T.; Uyttebroek, M.; Luna, M.; Gastone, F.; De Boer, C.; Klaas, N.; Sapion, H.; Eisenmann, H.; Larsson, P.-O.; et al. Field assessment of guar gum stabilized microscale zerovalent iron particles for in-situ remediation of 1,1,1-trichloroethane. J. Contam. Hydrol.
**2014**, 164, 88–99. [Google Scholar] [CrossRef] [Green Version] - Tosco, T.; Gastone, F.; Sethi, R. Guar gum solutions for improved delivery of iron particles in porous media (Part 2): Iron transport tests and modeling in radial geometry. J. Contam. Hydrol.
**2014**, 166, 34–51. [Google Scholar] [CrossRef] [Green Version] - Christiansen, C.M.; Damgaard, I.; Broholm, M.; Kessler, T.; Klint, K.E.; Nilsson, B.; Bjerg, P.L. Comparison of Delivery Methods for Enhanced In Situ Remediation in Clay Till. Groundw. Monit. Remediat.
**2010**, 30, 107–122. [Google Scholar] [CrossRef] - Litter, M. Iron Nanomaterials for Water and Soil Treatment; Jenny Stanford Publishing: Singapore, 2018. [Google Scholar]
- O’Carroll, D.; Sleep, B.; Krol, M.; Boparai, H.; Kocur, C. Nanoscale zero valent iron and bimetallic particles for contaminated site remediation. Adv. Water Resour.
**2013**, 51, 104–122. [Google Scholar] [CrossRef] - Tiraferri, A.; Chen, K.L.; Sethi, R.; Elimelech, M. Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum. J. Colloid Interface Sci.
**2008**, 324, 71–79. [Google Scholar] [CrossRef] - Gastone, F.; Tosco, T.; Sethi, R. Green stabilization of microscale iron particles using guar gum: Bulk rheology, sedimentation rate and enzymatic degradation. J. Colloid Interface Sci.
**2014**, 421, 33–43. [Google Scholar] [CrossRef] [Green Version] - Dalla Vecchia, E.; Luna, M.; Sethi, R. Transport in Porous Media of Highly Concentrated Iron Micro- and Nanoparticles in the Presence of Xanthan Gum. Environ. Sci. Technol.
**2009**, 43, 8942–8947. [Google Scholar] [CrossRef] [PubMed] - Cohen, M.; Yakirevich, A.; Weisbrod, N. The Role of Stabilizer Concentration in the Mobility of Carbon-Supported Nanozerovalent Iron (nZVI) in Fractured Media. Water Resour. Res.
**2019**, 55, 8164–8177. [Google Scholar] [CrossRef] - Cohen, M.; Weisbrod, N. Field Scale Mobility and Transport Manipulation of Carbon-Supported Nanoscale Zerovalent Iron in Fractured Media. Environ. Sci Technol
**2018**, 52, 7849–7858. [Google Scholar] [CrossRef] [PubMed] - Thombare, N.; Jha, U.; Mishra, S.; Siddiqui, M.Z. Guar gum as a promising starting material for diverse applications: A review. Int. J. Biol. Macromol.
**2016**, 88, 361–372. [Google Scholar] [CrossRef] [PubMed] - Xue, W.; Huang, D.; Zeng, G.; Wan, J.; Cheng, M.; Zhang, C.; Hu, C.; Li, J. Performance and toxicity assessment of nanoscale zero valent iron particles in the remediation of contaminated soil: A review. Chemosphere
**2018**, 210, 1145–1156. [Google Scholar] [CrossRef] [PubMed] - Velimirovic, M.; Simons, Q.; Bastiaens, L. Guar gum coupled microscale ZVI for in situ treatment of CAHs: Continuous-flow column study. J. Hazard. Mater.
**2014**, 265, 20–29. [Google Scholar] [CrossRef] [PubMed] - Gastone, F.; Tosco, T.; Sethi, R. Guar gum solutions for improved delivery of iron particles in porous media (Part 1): Porous medium rheology and guar gum-induced clogging. J. Contam. Hydrol.
**2014**, 166, 23–33. [Google Scholar] [CrossRef] [Green Version] - Tosco, T.; Marchisio, D.; Lince, F.; Sethi, R. Extension of the Darcy-Forchheimer Law for Shear-Thinning Fluids and Validation via Pore-Scale Flow Simulations. Transp. Porous Media
**2013**, 96, 1–20. [Google Scholar] [CrossRef] - Truex, M.J.; Vermeul, V.R.; Mendoza, D.P.; Fritz, B.G.; Mackley, R.D.; Oostrom, M.; Wietsma, T.W.; Macbeth, T.W. Injection of Zero-Valent Iron into an Unconfined Aquifer Using Shear-Thinning Fluids. Groundw. Monit. Remediat.
**2011**, 31, 50–58. [Google Scholar] [CrossRef] - Zhong, L.; Szecsody, J.; Oostrom, M.; Truex, M.; Shen, X.; Li, X. Enhanced remedial amendment delivery to subsurface using shear thinning fluid and aqueous foam. J. Hazard. Mater.
**2011**, 191, 249–257. [Google Scholar] [CrossRef] - Luna, M.; Gastone, F.; Tosco, T.; Sethi, R.; Velimirovic, M.; Gemoets, J.; Muyshondt, R.; Sapion, H.; Klaas, N.; Bastiaens, L. Pressure-controlled injection of guar gum stabilized microscale zerovalent iron for groundwater remediation. J. Contam. Hydrol.
**2015**, 181, 46–58. [Google Scholar] [CrossRef] [PubMed] - Xue, D.; Sethi, R. Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles. J. Nanoparticle Res.
**2012**, 14, 1239. [Google Scholar] [CrossRef] [Green Version] - Longo, S.; Di Federico, V.; Chiapponi, L.; Archetti, R. Experimental verification of power-law non-Newtonian axisymmetric porous gravity currents. J. Fluid Mech.
**2013**, 731, 1–12. [Google Scholar] [CrossRef] [Green Version] - Ciriello, V.; Di Federico, V. Similarity solutions for flow of non-Newtonian fluids in porous media revisited under parameter uncertainty. Adv. Water Resour.
**2012**, 43, 38–51. [Google Scholar] [CrossRef] - Wexler, J.S.; Trinh, P.H.; Berthet, H.; Quennouz, N.; Du Roure, O.; Huppert, H.E.; Linder, A.; Stone, H.A. Bending of elastic fibres in viscous flows: The influence of confinement. J. Fluid Mech.
**2013**, 720, 517–544. [Google Scholar] [CrossRef] [Green Version] - Tatti, F.; Papini, M.P.; Sappa, G.; Raboni, M.; Arjmand, F.; Viotti, P. Contaminant back-diffusion from low-permeability layers as affected by groundwater velocity: A laboratory investigation by box model and image analysis. Sci. Total Environ.
**2018**, 622–623, 164–171. [Google Scholar] [CrossRef] [PubMed] - Luciano, A.; Mancini, G.; Torretta, V.; Viotti, P. An empirical model for the evaluation of the dissolution rate from a DNAPL-contaminated area. Environ. Sci. Pollut. Res.
**2018**, 25, 33992–34004. [Google Scholar] [CrossRef] - Chao, H.-C.; Rajaram, H.; Illangasekare, T. Intermediate-scale experiments and numerical simulations of transport under radial flow in a two-dimensional heterogeneous porous medium. Water Resour. Res.
**2000**, 36, 2869–2884. [Google Scholar] [CrossRef] - Kobus, H.; Koschitzky, H.-P. Role of Controlled Experiments for Research on Groundwater Contamination and Remediation. In Proceedings of the Groundwater Quality: Remediation and Protection Conference, Prague, Czech Republic, 15–18 May 1995; pp. 431–438. [Google Scholar]
- Chaudemanche, C.; Budtova, T. Mixtures of pregelatinised maize starch and κ-carrageenan: Compatibility, rheology and gelation. Carbohydr. Polym.
**2008**, 72, 579–589. [Google Scholar] [CrossRef] - Lindner, A.; Bonn, D.; Meunier, J. Viscous Fingering in a Shear-Thinning Fluid. Phys. Fluids
**2000**, 12, 256–261. [Google Scholar] [CrossRef] - Bianco, C.; Tosco, T.; Sethi, R. A 3-dimensional micro- and nanoparticle transport and filtration model (MNM3D) applied to the migration of carbon-based nanomaterials in porous media. J. Contam. Hydrol.
**2016**, 193, 10–20. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Tosco, T.; Sethi, R. Transport of Non-Newtonian Suspensions of Highly Concentrated Micro- And Nanoscale Iron Particles in Porous Media: A Modeling Approach. Environ. Sci. Technol.
**2010**, 44, 9062–9068. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Dentz, M.; Icardi, M.; Hidalgo, J.J. Mechanisms of dispersion in a porous medium. J. Fluid Mech.
**2018**, 841, 851–882. [Google Scholar] [CrossRef] [Green Version] - Katzourakis, V.E.; Chrysikopoulos, C.V. Modeling dense-colloid and virus cotransport in three-dimensional porous media. J. Contam. Hydrol.
**2015**, 181, 102–113. [Google Scholar] [CrossRef] - Chrysikopoulos, C.V.; Syngouna, V.I.; Vasiliadou, I.A.; Katzourakis, V.E. Transport of Pseudomonas putida in a 3-D Bench Scale Experimental Aquifer. Transp. Porous Media
**2012**, 94, 617–642. [Google Scholar] [CrossRef] - Kretzschmar, R.; Borkovec, M.; Grolimund, D.; Elimelech, M. Mobile subsurface colloids and their role in contaminant transport. Adv. Agron.
**1999**, 66, 121–193. [Google Scholar] [CrossRef] - Katzourakis, V.E.; Chrysikopoulos, C.V. Mathematical modeling of colloid and virus cotransport in porous media: Application to experimental data. Adv. Water Resour.
**2014**, 68, 62–73. [Google Scholar] [CrossRef] - Bradford, S.; Bettahar, M.; Simunek, J.; van Genuchten, M. Straining and attachment of colloids in physically heterogeneous porous media. Vadose Zone J.
**2004**, 3, 384–394. [Google Scholar] [CrossRef] - Bradford, S.; Simunek, J.; Bettahar, M.; Van Genuchten, M.; Yates, S. Modeling colloid attachment, straining, and exclusion in saturated porous media. Environ. Sci. Technol.
**2003**, 37, 2242–2250. [Google Scholar] [CrossRef] - Boccardo, G.; Crevacore, E.; Sethi, R.; Icardi, M. A robust upscaling of the effective particle deposition rate in porous media. J. Contam. Hydrol.
**2018**, 212, 3–13. [Google Scholar] [CrossRef] [Green Version] - Yao, K.-M.; Habibian, M.T.; O’Melia, C.R. Water and waste water filtration. Concepts and applications. Environ. Sci. Technol.
**1971**, 5, 1105–1112. [Google Scholar] [CrossRef] - Cross, M.M. Rheology of non-Newtonian fluids: A new flow equation for pseudoplastic systems. J. Colloid Sci.
**1965**, 20, 417–437. [Google Scholar] [CrossRef] - Ko, C.; Elimelech, M. The “shadow effect” in colloid transport and deposition dynamics in granular porous media: Measurements and mechanisms. Environ. Sci. Technol.
**2000**, 34, 3681–3689. [Google Scholar] [CrossRef] - Johnson, P.; Elimelech, M. Dynamics of colloid deposition in porous-media-blocking based on random sequential adsorption. Langmuir
**1995**, 11, 801–812. [Google Scholar] [CrossRef] - Bradford, S.; Yates, S.; Bettahar, M.; Simunek, J. Physical factors affecting the transport and fate of colloids in saturated porous media. Water Resour. Res.
**2002**, 38, 63-1–63-12. [Google Scholar] [CrossRef] [Green Version] - Homsy, G.M. Viscous Fingering in Porous Media. Annu. Rev. Fluid Mech.
**1987**, 19, 271–311. [Google Scholar] [CrossRef] - Obernauer, S.; Temprano, N.; Chertcoff, R.; D’Onofrio, A.G.; Gabbanelli, S.; Rosen, M. Miscible Displacement of Polymers in Porous Medi. In Proceedings of the SPE Latin America/Caribbean Petroleum Engineering Conference, Buenos Aires, Argentina, 27–29 April 1994; p. 16. [Google Scholar]
- Bradford, S.A.; Torkzaban, S.; Walker, S.L. Coupling of physical and chemical mechanisms of colloid straining in saturated porous media. Water Res.
**2007**, 41, 3012–3024. [Google Scholar] [CrossRef]

**Figure 2.**Rheological curves of CMC-2000 at 10 g/L, GG at 3 g/L and GG:XG at 1.75 g/L solutions (

**a**), bulk and porous medium rheograms of the XG:GG mixture at 1.75 g/L (

**b**): experimental data (point values) and model (solid line). CMC, carboxymethyl cellulose; GG, guar gum; XG, xanthan gum.

**Figure 3.**(

**a**) frame captured at the end of the test, (

**b**) the total iron concentration map of the radial model, (

**c**) total iron concentration profiles along the three different directions, and (

**d**) the variation of pressure over time measured at 7 cm from the injection well: experimental data (point values) and model (black line).

**Figure 4.**Simulation results for microscale iron (mZVI) particles stabilized through the gel and mZVI particles dispersed in GG only: (

**a**) total iron concentration profiles, (

**b**) the variation of pressure over time measured at 7 cm from the injection well.

Gel Concentration (g/L) | mZVI Conc. (g/L) | Well Radius (m) | $\mathbf{Discharge}\text{}\mathbf{Rate}\text{}({\mathbf{m}}^{3}/\mathbf{h})$ | Injection Duration (min) | Simulation Radius (m) | Cell Number | Inlet Boundary Condition |
---|---|---|---|---|---|---|---|

1.75 | 20 | 0.02 | 1 | 46 | 0.9 | 300 | 3rd Type-Robin |

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**MDPI and ACS Style**

Mondino, F.; Piscitello, A.; Bianco, C.; Gallo, A.; de Folly D’Auris, A.; Tosco, T.; Tagliabue, M.; Sethi, R.
Injection of Zerovalent Iron Gels for Aquifer Nanoremediation: Lab Experiments and Modeling. *Water* **2020**, *12*, 826.
https://doi.org/10.3390/w12030826

**AMA Style**

Mondino F, Piscitello A, Bianco C, Gallo A, de Folly D’Auris A, Tosco T, Tagliabue M, Sethi R.
Injection of Zerovalent Iron Gels for Aquifer Nanoremediation: Lab Experiments and Modeling. *Water*. 2020; 12(3):826.
https://doi.org/10.3390/w12030826

**Chicago/Turabian Style**

Mondino, Federico, Amelia Piscitello, Carlo Bianco, Andrea Gallo, Alessandra de Folly D’Auris, Tiziana Tosco, Marco Tagliabue, and Rajandrea Sethi.
2020. "Injection of Zerovalent Iron Gels for Aquifer Nanoremediation: Lab Experiments and Modeling" *Water* 12, no. 3: 826.
https://doi.org/10.3390/w12030826