Nitrogen Assessment in Amended Mining Soils Sown with Coronilla juncea and Piptatherum miliaceum

Abstract

Metalliferous mining activities generate a large amount of waste. This waste usually has high concentrations of pollutants such as metal(oid)s associated with the extractive processes, which, if not properly treated and reclaimed, put the ecosystem and the population at risk. One of the most used techniques for mine waste reclamation is aided phytostabilization, which is based on the use of plants that immobilize metals in the soil/roots aided by the use of amendments to improve the soil properties to favor plant growth. Although amendments increase nutrients and improve the soil properties, the concentration of these nutrients—especially N, the most limiting plant nutrient—decreases over time. Thus, this study focused on the evaluation of the relationship between different combinations of amendments (compost, biochar, zeolite and limestone) and plant growth (we introduced Coronilla juncea and Piptatherum miliaceum) on the evolution of soil N over time as well as the influence of C. juncea on soil N fixation. The results showed that the addition of amendments improved the soil characteristics in all plots favoring the growth of C. juncea and P. miliaceum. The compost provided higher concentrations of total N, nitrites, nitrates and ammonium due to the nature of this amendment and the biochar was less in measure. The limestone helped to elevate the pH and the zeolite controlled the exchangeable ions. Soils from C. juncea showed higher concentrations of N forms, suggesting that this legume contributes to the enrichment of soil N, likely due to biological fixation. Hence, the combinations limestone-zeolite-compost and limestone-zeolite-compost-biochar were the most suitable treatments for improving the soil fertility and favored plant growth. In addition, C. juncea seems to be a good candidate for reclaiming mining environments.

Editorial for Special Issue “Risk Assessment, Management and Control of Mining Contamination”

“…To do this, they assessed six reactants for iron precipitation: CaO, Ca(OH) 2 , Na 2 CO 3 , CaCO 3 , NaOH, and MgO; they selected Ca(OH) 2 because it is the reagent recommended for zinc yield recovery, electrowinning efficiency, and iron precipitate filtration rate. Beltrá et al [3] propose using different types and combinations of amendments for improving the soil fertility and favoring plant growth in a mining waste phytostabilization process. Zhang et al [4] investigated health risks from soil contaminated by cadmium from a Chinese coal chemical plant and determined the safety threshold of this metal.…”