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Wu Z, Wu S, Hou Y, Cao H, Cai C. Facilitated transport of toluene and naphthalene with humic acid in high- and low-permeability systems: Role of ionic strength and cationic type. JOURNAL OF HAZARDOUS MATERIALS 2024; 465:133487. [PMID: 38219592 DOI: 10.1016/j.jhazmat.2024.133487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 12/25/2023] [Accepted: 01/08/2024] [Indexed: 01/16/2024]
Abstract
The occurrence of colloids on pollutants transport in groundwater has attracted more attention. However, the research on the regulation mechanism of colloids on combined pollutants transport in heterogeneous aquifers is limited. In this study, a series of tank experiments were conducted to systematically investigate the effects of ionic strength, and cation type on humic acid (HA) facilitated transport of toluene (TOL), and naphthalene (NAP) in high- and low-permeability systems. The results showed that HA facilitated pollutants transport in low Na+ solution. In Ca2+ solution, the presence of HA hindered pollutants transport, and the inhibition increased with the increase of ionic strength. Both in Na+ solution and low Ca2+ solution, the influence of heterogeneous structure on pollutant transport played a dominant role, and TOL and NAP had a greater transport potential in the high permeability zone (HPZ) due to the preferential flow. Whereas, deposition of HA aggregates, and electrostatic attractive interaction had negative effects on transport than groundwater flow in high Ca2+ solution. Pollutants were prone to accumulate at the bottom of the HPZ, and the top of the low permeability zone (LPZ). These new findings provide insights into the mechanism of colloids influence on the pollutants transport in heterogenous aquifer.
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Affiliation(s)
- Zhongran Wu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Science, Beijing 100049, China
| | - Shengyu Wu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Science, Beijing 100049, China
| | - Yao Hou
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Science, Beijing 100049, China; College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Hongjian Cao
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Science, Beijing 100049, China
| | - Chao Cai
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Science, Beijing 100049, China.
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Dorchester L, Day-Lewis FD, Singha K. Evaluation of Dual Domain Mass Transfer in Porous Media at the Pore Scale. GROUND WATER 2024; 62:260-275. [PMID: 37254685 DOI: 10.1111/gwat.13328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 04/28/2023] [Accepted: 05/10/2023] [Indexed: 06/01/2023]
Abstract
Dual-porosity models are often used to describe solute transport in heterogeneous media, but the parameters within these models (e.g., immobile porosity and mobile/immobile exchange rate coefficients) are difficult to identify experimentally or relate to measurable quantities. Here, we performed synthetic, pore-scale millifluidics simulations that coupled fluid flow, solute transport, and electrical resistivity (ER). A conductive-tracer test and the associated geoelectrical signatures were simulated for four flow rates in two distinct pore-scale model scenarios: one with intergranular porosity, and a second with an intragranular porosity also defined. With these models, we explore how the effective characteristic-length scale estimated from a best-fit dual-domain mass transfer (DDMT) model compares to geometric aspects of the flow field. In both model scenarios we find that: (1) mobile domains and immobile domains develop even in a system that is explicitly defined with one domain; (2) the ratio of immobile to mobile porosity is larger at faster flow rates as is the mass-transfer rate; and (3) a comparison of length scales associated with the mass-transfer rate (Lα ) and those associated with calculation of the Peclet number (LPe ) show LPe is commonly larger than Lα . These results suggest that estimated immobile porosities from a DDMT model are not only a function of physically mobile or immobile pore space, but also are a function of the average linear pore-water velocity and physical obstructions to flow, which can drive the development of immobile porosity even in single-porosity domains.
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Affiliation(s)
| | - Frederick D Day-Lewis
- Pacific Northwest National Laboratory, Earth Systems Science Division, 902 Battelle Boulevard, Richland, WA, 99352
- Department of Geophysics, Colorado School of Mines, Golden, CO
| | - Kamini Singha
- Hydrologic Science and Engineering Program, Colorado School of Mines, 1301 19th Street, Golden, CO, 80401
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