Humic substances reduce the erodibility of soils in mining areas

Abstract The management of mineral processing wastes is a fundamental issue in the cleaner production and sustainable development of mining industry. This work demonstrates that the humic substances obtained from the recycling of mineral coal tailings can minimize the environmental impact associated with the exploitation of ornamental rocks and could be used in the recovery process for large agricultural areas that are currently degraded. Results of disaggregation tests with specimens of different ages reveal that the incorporation of the humic substrate results in greater stability of the solid particles of the material due to insoluble two- or three-dimensional structures that act as cementing agents by increasing the tensile strength of the solid matrix. It was also shown an increase in the tensile strength in specimens that were subjected to a long period of storage (i.e., the strength in test specimens with 5% of humic substances as compared to no incorporation of humic substances doubled in a period of 1 year, from 3.23 KPa to 6.74 KPa). Moreover, the stability of long-term humic substrate seems to be an advantage over products of easy degradation that only confer an intense effect on the initial stability of aggregates after incorporation, which is a short-term effect. Results from optic and electron microscopy corroborate the above statement. Moreover, results from microscopy clearly show that the effect of the incorporation of humic substance is more apparent over a longer period of time. The results of this study may be useful for other countries where mining industry causes erodibility of soils.