Bacterial communities in mining soils and surrounding areas under regeneration process in a former ore mine

Abstract Human activities on the Earth's surface change the landscape of natural ecosystems. Mining practices are one of the most severe human activities, drastically altering the chemical, physical and biological properties of the soil environment. Bacterial communities in soil play an important role in the maintenance of ecological relationships. This work shows bacterial diversity, metabolic repertoire and physiological behavior in five ecosystems samples with different levels of impact. These ecosystems belong to a historical area in Iron Quadrangle, Minas Gerais, Brazil, which suffered mining activities until its total depletion without recovery since today. The results revealed Proteobacteria as the most predominant phylum followed by Acidobacteria, Verrucomicrobia, Planctomycetes, and Bacteroidetes. Soils that have not undergone anthropological actions exhibit an increase ability to degrade carbon sources. The richest soil with the high diversity was found in ecosystems that have suffered anthropogenic action. Our study shows profile of diversity inferring metabolic profile, which may elucidate the mechanisms underlying changes in community structure in situ mining sites in Brazil. Our data comes from contributing to know the bacterial diversity, relationship between these bacteria and can explore strategies for natural bioremediation in mining areas or adjacent areas under regeneration process in iron mining areas.

Freshwater quality of a stream in agricultural area where organic compost from animal and vegetable wastes is used / Qualidade da água de um córrego em área agrícola onde é usado composto orgânico de resíduos animais e vegetais

ABSTRACT Organic compost from biomass residues constitutes a viable alternative for partial or total replacement of mineral fertilizers for growing vegetables. This study evaluated the effects of compost on the water quality of a stream used mainly for irrigation of agricultural crops cultivated in nearby soil that has been treated with organic compost produced by carcasses, animal and vegetable waste for the last ten years. We sampled water biannually for two years, 2013 and 2014, from five locations along the stream. Physical variables and some chemical variables were analyzed. We also analyzed the total number of coliforms (Escherichia coli). Bacterial populations were compared by carbon substrate consumption. Total phosphorus contents in the samples from 2014 exceeded 0.1 mg L-1. The concentrations of other chemical species analyzed and the results for the physical variables were in accordance with the expected values compared with national and international water quality standards. The environment showed differential carbon source consumption and a high diversity of microorganisms, but our results did not show any evidence that the applied compost is changing the microbial population or its metabolic activity. This study shows that the use of the organic compost in agricultural areas seen does not negatively influence the quality of surface water in the study area. These results are important because the process of composting animal and vegetable waste and the use of compost obtained can be an alternative sustainable for adequate destination of these wastes.

RESUMO Composto orgânico produzido a partir de biomassa residual constitui uma alternativa viável para a substituição parcial ou total de fertilizantes minerais no cultivo de hortaliças. Neste estudo foram avaliados os efeitos do composto, sobre a qualidade da água de um córrego, usado principalmente para a irrigação de culturas agrícolas cultivadas em solo nas proximidades, tratado nos últimos dez anos com composto orgânico produzido a partir de carcaças, resíduos animais e vegetais. Amostras de água foram coletadas semestralmente, em 2013 e 2014, em cinco pontos ao longo do córrego. Foram analisadas variáveis físicas, algumas variáveis químicas e o número total de coliformes (Escherichia coli). As populações bacterianas foram comparadas pelo consumo de substratos de carbono. Os teores de fósforo total nas amostras de 2014 ultrapassaram 0,1 mg L-1. As concentrações das demais espécies químicas analisadas e os resultados para as variáveis fisicas ficaram de acordo com valores estabelecidos em normas nacionais e internacionais de qualidade de água. O ambiente mostrou consumo diferencial de fontes de carbono e grande diversidade de micro-organismos, mas os resultados não mostraram qualquer evidência de que o composto aplicado seja o fator responsável pela alteração da população microbiana ou sua atividade metabólica. Este estudo mostra que o uso do composto orgânico em áreas agrícolas parece não influenciar negativamente a qualidade da água superficial na área estudada. Estes resultados são importantes porque o processo de compostagem de resíduos animais e vegetais e o uso do composto obtido podem ser uma alternativa sustentável para o destino adequado desses resíduos.