Evaluation of the Impact of Transition from Porous to Fractured Rock Media on 3D Field-scale DNAPLs Contamination

• Published in: Journal of hazardous materials 2024-01, Vol.462, p.132711-132711, Article 132711
• Main Authors: Kim, Taehoon, Han, Weon Shik, Yoon, Seonkyoo, Kang, Peter K., Shin, Jehyun, Nam, Myung Jin
• Format: Article
• Language: English
• Subjects: 3D Numerical Modeling; DNAPLs Contamination; Field Scale; Fractured Rock; Site Characterization; Weathered Rock
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.132711

A 3D high-resolution subsurface characteristic (HSC) numerical model to assess migration and distribution of subsurface DNAPLs was developed. Diverse field data, including lithologic, hydrogeologic, petrophysical, and fracture information from both in situ observations and laboratory experiments were utilized for realistic model representation. For the first time, the model integrates hydrogeologic characteristics of both porous (unconsolidated soil (US) and weathered rock (WR)) and fractured rock (FR) media distinctly affecting DNAPLs migration. This allowed for capturing DNAPLs behavior within US, WR, and FR as well as at the boundary between the media, simultaneously. In the 3D HSC model, hypothetical 100-year DNAPLs contamination was simulated, quantitatively analyzing its spatiotemporal distributions by momentum analyses. Twelve sensitivity scenarios examined the impact of WR and FR characteristics on DNAPLs migration, delineating significant roles of WR. DNAPLs primarily resided in WR due to low permeability and limited penetration into FR through sparse inlet fractures. The permeability anisotropy in WR was most influential to determine the DNAPLs fate, surpassing the impacts of FR characteristics, including rock matrix permeability, fracture aperture size, and fracture + rock mean porosity. This study first attempted to apply the field-data-based multiple geological media concept in the DNAPLs prediction model. Consequently, the field-scale effects of WR and media transitions, which have been often overlooked in evaluating DNAPLs contamination, were underscored. Dense non-aqueous phase liquids (DNAPLs) contamination has become a global, unresolved conundrum due to its widespread industrial application and complex dynamics in the subsurface. DNAPLs are poorly soluble in water and have a higher density than water. Therefore, they infiltrate deeply under groundwater table, contaminating multiple aquifers and geological media at various depths. At the actual DNAPLs contaminated site, their fate and transport can be disturbed by irregular geostructures and hydrologic properties arising from weathering process. This study highlighted less explored aspects of field-scale DNAPLs behavior in weathered rock, by developing a 3-D high-resolution subsurface characteristic numerical model. [Display omitted] •Coupled DNAPLs migration in porous and fractured rock media is captured.•Significant effects of weathered rock – fractured rock transition are explored.•Sha