Air quality impact assessment for the Eurasia Tunnel in Istanbul, Turkey.

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.

Sherwood correlation for dissolution of pooled NAPL in porous media.

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.