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The Eurasia Tunnel, a 5.4-km tunnel connecting the Asian and European sides of Istanbul, Turkey, was opened for operation in December 2016. This paper describes the air quality modeling that was conducted during the design phase of the structure, to evaluate the impact of the tunnel traffic on ambient air quality in the vicinity of the tunnel. The ventilation of the tunnel consists of longitudinal forced ventilation with vertical extraction through two stacks located near the Asian and European portals of the tunnel. The analysis was conducted using the AERMOD computer program for three pollutants CO, NO2, and PM10. Model results show that pollutants will rapidly disperse once released from the stack and will not affect air quality in the vicinity of the tunnel. The most critical parameters which controlled the ventilation system design were found to be NO2 and PM10. Maximum concentrations are not expected to violate the pertinent Turkish and EU air quality standards. Overall, this analysis shows that the ventilation system is efficient for the dispersion of the pollutants.

The rate of interphase mass transfer from non-aqueous phase liquids (NAPLs) entrapped in the subsurface into the surrounding mobile aqueous phase is commonly expressed in terms of Sherwood (Sh) correlations that are expressed as a function of flow and porous media properties. Because of the lack of precise methods for the estimation of the interfacial area separating the NAPL and aqueous phases, most studies have opted to use modified Sherwood expressions that lump the interfacial area into the interphase mass transfer coefficient. To date, there are only two studies in the literature that have developed non-lumped Sherwood correlations; however, these correlations have undergone limited validation. In this paper controlled dissolution experiments from pooled NAPL were conducted. The immobile NAPL mass is placed at the bottom of a flow cell filled with porous media with water flowing horizontally on top. Effluent aqueous phase concentrations were measured for a wide range of aqueous phase velocities and for two different porous media. To interpret the experimental results, a two-dimensional pore network model of the NAPL dissolution kinetics and aqueous phase transport was developed. The observed effluent concentrations were then used to compute best-fit mass transfer coefficients. Comparison of the effluent concentrations computed with the two-dimensional pore network model to those estimated with one-dimensional analytical solutions indicates that the analytical model which ignores the transport in the lateral direction can lead to under-estimation of the mass transfer coefficient. Based on system parameters and the estimated mass transfer coefficients, non-lumped Sherwood correlations were developed and compared to previously published data. The developed correlations, which are a significant improvement over currently available correlations that are associated with large uncertainties, can be incorporated into future modeling studies requiring non-lumped Sh expressions.

Summarization: The accidental release of organic contaminants in the form of non-aqueous phase liquids (NAPLs) into the subsurface is a widespread and challenging environmental problem. Successful remediation of sites contaminated with NAPLs is essential for the protection of human health and the environment. One technology that has received significant attention is the injection of chemical additives (such as cosolvents) upgradient of the NAPL zone for the enhanced dissolution and mobilization of the NAPL mass. A key process influencing the effectiveness of NAPL mass recovery is the interphase mass transfer which is the transfer of components across the interface separating the different phases. In this work, we examine the impact of cosolvent content, flushing solution velocity, and injection pattern (continuous versus intermittent) on the interphase mass transfer rate. A series of flushing experiments were conducted using an intermediate-scale tank which allows for the impact of density variations on DNAPL mobility. The target DNAPL selected in this study was trichloroethylene while the flushing solutions consisted of ethanol–water mixtures with ethanol contents ranging from 0 to 50% by volume. The experimental results were also modeled using the UTCHEM multiphase flow simulator that was modified to model cosolvent flushing. Results show that the observed interphase mass transfer coefficient, expressed as a modified Sherwood number, was much lower than predicted based on published correlations developed under idealized conditions. Moreover, interphase mass transfer rate decreased with time, indicating that a single interphase mass transfer coefficient cannot accurately model the entire flushing solution. The data also suggest that the interphase mass transfer coefficient is dependent on cosolvent content. Presented on: Water, Air, and Soil Pollution