Analysis of Transport Parameters for a Cr(VI) Contaminated Aquifer in México

In the Buenavista area of Leon City, Mexico, Cr(VI) groundwater contamination was detected, originating from an industrial landfill with chromium compounds. A 2D vertical simulation model was established for the Buenavista study area. Laboratory and field data were incorporated into a finite element groundwater flow model and a solute transport model to analyze the transport parameters in the Buenavista shallow aquifer. A sensitivity analysis was performed to obtain values representative of the transport parameters (hydraulic conductivity [K], longitudinal, horizontal and vertical transverse dispersivities [α_L, α_TV], distribution coefficient [K _d ], the initial concentration [C_o] and pumping rates [Q]). This analysis allowed a good calibration of the model. The incorporation of the resulting set of parameters in the finite element model enabled the reproduction the observed contaminant plume in Buenavista close to 95 % match. The values obtained were α_L = 50.0 m, α_TV = 2.5 m, K _d  = 0.007 mL/g, C_o = 160 mg/L and Q = 100 m³/d. The sensitivity analysis indicated that the dispersion of the Cr(VI) plume is most sensitive to variations in hydraulic conductivity, the distribution coefficient, longitudinal and transverse dispersivity and pumping rates. In addition to the sensitivity analysis, it was observed that Q strongly affects the plume geometry.