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 [a_L, a_TV], distribution coefficient [Kd], the initial concentration [Co] 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 of the observed contaminant plume in Buenavista with a close to 95 % match. The values obtained were a_L = 50.0 m, a_TV = 2.5 m, Kd = 0.007 mL/g, Co = 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.