Abstract

Arsenic (As) sorption characteristics in decommissioned tailings dam environment at the Obuasi mine, Ghana was studied. The aim was to outline effective remediation strategy for As, hence the objectives were to establish: (1) Arsenic degradation capacity of the decommissioned tailings dam environment and empirical model(s) to describe the degradation pattern; (2) relevant equilibrium concentration range and time frame for As degradation by natural attenuation. Eighteen water sampling events from monitoring boreholes were spread over 24 months, while leachate from dynamic leaching experiment of soil/sediment were sampled during 14 sampling events, spread over 30 weeks. The samples were filtered through 0.45 μm cellulose membrane and filtrates analyzed for As concentrations. Results followed reducing mass pattern for both sets of observations. The Freundlich and Langmiur isotherms were applied to both data, with the Freundlich isotherm indicating a strong sorption capacity, with regression gradients of 0.528 and 0.615 and high predictive model $(R^2)$ values of 0.842 and 0.912 for both experimental and field data respectively. A t-test statistic established that, equilibrium existed between sorption processes within the media between compliance value (C), ranges of 0.50-0.01 mg/L and time period (t) of 14.5-45.5 months. The As degradation pattern within both investigated media is governed by the model equation: $[t_n \>= \>- 8ln(c_n) + 9]$ or; $[t_n\>=\> 8ln(\frac 1 c_n) +9]$; where n is a variable. The model may be used to evaluate soil sample leaching results from contaminated sites ear-marked for remediation through setting targets and objectives for environmental management plans.

Keywords:

Arsenic, degradation, isotherms, obuasi mine, sorption, tailings dam,

References

Competing interests

The authors have no competing interests.

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The authors have no competing interests.