Numerical model of the behavior of chlorinated ethenes in a fractured, karstic limestone aquifer

Abstract

Characterizing the transport and degradation of chlorinated ethenes in fractured aquifers, as well as the assessment of cleanup times, poses an extreme technical challenge. In the presented study, a method to analyze reactive transport and reductive dechlorination of chlorinated solvents in fractured aquifers is developed. A rough-walled parallel-plate model of nonlinear flow behavior is coupled with random-walk particle tracking, incorporating particle exchange between the mobile and stagnant zones, adsorption processes, and reductive dechlorination reaction pathways. The developed methodology, considering reductive dechlorination processes in a Lagrangian framework, is able to simulate the motion of particles affected by first-order network reactions, so that particles move according to their chemical state, affecting physical transport processes (advection, dispersion, mass-transfer exchange between mobile and stagnant zones). The developed model is applied to a case study of groundwater contamination in the industrial area of Bari and Modugno (Italy), where the limestone aquifer has a fractured, karstic nature. The steady-state distribution of the contamination by chlorinated ethenes from a source at a hot spot is obtained and compared with the observed scenario of contamination, in order to estimate the plausible transport and degradation processes and the mass loading at source. The study represents a valuable tool in deciding the role of natural attenuation as a treatment option, where the natural attenuation capacity of groundwater can be integrated with engineering methods in order to obtain site remediation.

Karst water resources in a changing world: Review of solute transport modelling approaches

“…For these reasons, the (biogeo)chemical reactions are generally overlooked in karst systems. But when they are considered, a (biogeo)chemical interaction term is often coupled with the advective-dispersive transport processes (Dvory et al, 2018a(Dvory et al, , 2018bPastore et al, 2021).…”

“…where 𝐾 𝑑 [L 3 M -1 ] is denoted as the distribution (or partition) coefficient that is described as a ratio of the sorbed concentration into (geological) material and the dissolved concentration in groundwater at (thermodynamically) equilibrium conditions. In karst aquifers, 𝐾 𝑑 is often used to describe the sorption degree of any species in karst groundwater based on the distribution of solute between solid matrix and groundwater (e.g., Pastore et al, 2021). Therefore, as for the manuscript submitted to Review of Geophysics estimation of retardation given in Eq.5, when 𝐾 𝑑 is equivalent to 0, it equals 1, which means that the retardation is negligible during the karst transport mechanism.…”

A Multi-Objective Improved Hybrid Butterfly Artificial Gorilla Troop Optimizer for Node Localization in Wireless Sensor Groundwater Monitoring Networks

“…In this case, study [35] simulated plume by means of a rough walled parallel plate model coupled with a geostatistical analysis [36] that clearly exhibits (Figure 11) a locally anisotropic behavior in correspondence to the hotspot area, due to the anticline formation of the fractured rock limestone formation in the ENE-WSW direction. In this case, it appeared evident that the position of the monitoring points realized by the Water Agency under the EPM assumption partially failed to capture the contamination.…”