Analysis of chlorinated ethenes behaviour in fractured and karstic limestone

Abstract

The understanding of the transport and degradation phenomena of chlorinated ethenes in fractured aquifers as well as the assessment of the cleanup times poses an extreme technical challenge. In the present study a method to analyze reactive transport and reductive dechlorination of chlorinated solvents in fractured aquifers is presented. Reductive dechlorination pathway, adsorption processes, mass exchange phenomena between mobile and stagnant zones as well as the non – linear flow behaviour in fractures are considered. 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 zone). The developed model is applied to a case study of groundwater contamination in the industrial area of Modugno – Bari (Italy), where the limestone aquifer has a fractured and karstic nature. The steady state distribution of the contamination by chlorinated ethenes with the source at the hot spot is obtained and compared with the observed scenario of contamination in order to estimate the plausible transport and degradation processes as well as the mass loading at source. The carried out study represents and valuable tool for deciding the role of natural attenuation in a treatment where the natural attenuation capacity of groundwater can be integrated with engineering methods for site remediation.