This study continues investigating the groundwater arsenic mobilization processes in El Paso Texas, by testing arsenic desorption from the solids of the aquifers into the groundwater. Multivariate regression and factor analysis complement previous bivariate correlations on archival information from wells in two basins (the Hueco and the Mesilla). Augmenting the archival information, fifteen well cuttings were analyzed for arsenic, iron and total organic carbon. The well cuttings were leached in pH 9 and 10 solutions and the leachates were analyzed for dissolved arsenic. Leachable arsenic ranged from 0.79 to 3.74 ppb and slightly higher concentrations were leached from pH 10 than from 9. Significant associations between dissolved arsenic and solid-phase iron (R-square 0.71 p-value < 0.01), and significant associations of arsenic leached from the cuttings with both dissolved and solid arsenic were found (R-square 0.62 and 0.66, p-value < 0.05 and 0.01). The distribution of arsenic in the Mesilla Basin is largely controlled by depth, with low arsenic water from the river overlying deeper and older water with higher pH and arsenic concentrations. In the Hueco, desorption of arsenic from aquifer solids may occur gradually along the path of flow while divalent cations are exchanged for monovalent ones (Positive and significant correlation of As with Na and K, and at the same time the negative significant of As with Ca and Mg, p-values between 0.001 and 0.05). The Hueco has a lower pH and lower arsenic concentrations than the Mesilla. A lower pH would be expected to result in lower arsenic concentrations if desorption from hydroxide solids is a major control on arsenic concentrations. Arsenic concentration in the groundwater in part by sorption/desorption to ferric hydroxides was supported by both archival and experimental analyses in the entire region.