Escória de siderurgia e nutrição fosfatada de milho inoculado com fungos micorrízicos arbusculares

The objective of this work was to evaluate the effect of the use of steel slag as a soil acidity corrective and of mycorrhizal fungi associated with phosphate fertilization on corn plants. The study was performed in a greenhouse, using 3-kg pots with a Typic Haplorthox, in a 4x5x2 factorial arrangement, with four acidity correction treatments (C1, correction with dolomitic limestone at a dose of 4 Mg ha-1; C2, correction with steel slag at a dose of 4 Mg ha-1; C3, correction with a 1:1 mixture of 2 Mg ha-1 dolomitic limestone and 2 Mg ha-1 steel slag; and C4, control, without pH correction), five phosphorus doses (0, 42, 95, 213, and 480 mg dm-3), and the presence or absence of two arbuscular mycorrhizal fungi (Rhizophagus clarus and Gigaspora margarita), with five replicates. Steel slag was efficient in correcting soil pH and providing Ca and Mg for the plants; therefore, it could replace limestone. The inoculation with R. clarus and G. margarita, associated with P doses of 42, 95, and 213 mg dm-3, improved the development of corn plants after 45 days, resulting in greater plant height, stem diameter, leaf area, and shoot and root dry matter.O objetivo deste trabalho foi avaliar o efeito do uso de escória de siderurgia como corretivo da acidez do solo e de fungos micorrízicos associados à adubação fosfatada em plantas de milho. O trabalho foi conduzido em casa de vegetação, tendo-se utilizado vasos com 3 kg de Latossolo Vermelho distrófico, em arranjo fatorial 4x5x2, com quatro tratamentos corretivos da acidez (C1, correção com calcário dolomítico na dosagem de 4 Mg ha-1; C2, correção com escória de siderurgia de aciaria na dosagem de 4 Mg ha-1; C3, correção com a mistura 1:1 de 2 Mg ha-1 de calcário dolomítico e 2 Mg ha-1 de escória; e C4, controle, sem correção de pH), cinco doses de fósforo (0, 42, 95, 213 e 480 mg dm-3), e presença ou ausência de dois fungos micorrízicos arbusculares (Rhizophagus clarus e Gigaspora margarita), com cinco repetições. A escória foi eficiente em corrigir o pH do solo e fornecer Ca e Mg para as plantas; portanto, pode substituir o calcário. A inoculação com R. clarus e G. margarita, associada às doses de 42, 95 e 213 mg dm-3 de P, promoveu melhoras no desenvolvimento de plantas de milho após 45 dias, tendo resultado em maiores altura, diâmetro do colo, área foliar e matéria seca das raízes e da parte aérea das plantas

Soil arthropod community responses to restoration in areas impacted by iron mining tailings deposition after Fundão dam failure

In 2015, the failure of the Fundão dam in Mariana, Brazil released ~43 million m 3 of iron mining tailings into the environment. Despite restoration initiatives in the following years, few studies-and most focused on revegetation-have evaluated the effectiveness of the restoration process in areas impacted by the disaster. We aimed to evaluate the responses of the arthropod community in areas impacted by iron mining tailings deposition from the Fundão dam that is in the restoration process. We defined sampling units in the riparian zone of the Gualaxo do Norte River, which is under restoration, and in a native not impacted riparian zone. We collected soil arthropods using pitfall traps and sampled environmental variables in the same sites. We used generalize least squares models (GLS) to test if the restored areas already presented values of arthropod diversity and functional group abundance similar to the reference area and to test which environmental variables are influencing arthropod diversity. We also tested how large the differences of arthropod community composition between the study areas and used the index of indicator species (IndVal) to verify which species could be used as an indicator of reference or restoration areas. The diversity of arthropods and the functional groups of detritivores and omnivores were higher in the native riparian zone. Understory density, soil density, organic matter content, and microbial biomass carbon were the environmental variables that significantly explained the diversity and species composition of arthropods. We show that restoration areas still have different soil arthropod diversity values and community composition when compared to reference areas. Evaluating the response of the arthropod community to the restoration process and long-term monitoring are essential to achieve a satisfactory result in this process and achieve a self-sustaining ecosystem

Tolerance to and accumulation of cadmium, copper, and zinc by Cupriavidus necator

Preliminary results of in vitro experiments with multicontaminated soils and solid media indicated that nodulating diazotrophic bacteria of the genus Cupriavidus are promising for the remediation of contaminated environments due to their symbiosis with legumes and metal tolerance. Thus, strains of Cupriavidus spp. (LMG 19424T, UFLA 01-659, UFLA 01-663, and UFLA 02-71) were tested for their ability to tolerate and bioaccumulate cadmium (Cd), copper (Cu), and zinc (Zn) in Luria-Bertani broth. Changes in the growth pattern of Cupriavidus strains in the presence or absence of heavy metals were analyzed by scanning electron microscopy and metal allocation by transmission electron microscopy, to clarify the mechanisms of bioremediation. Highest tolerance was detected for strain UFLA 01-659 (minimum inhibitory concentration of 5, 4.95, and 14.66 mmol L−1 of Cd, Cu, and Zn, respectively). Among the removal rates of the metals tested (9.0, 4.6, and 3.2 mg L−1 of Cd, Cu, and Zn, respectively), the bacterial activity was clearly highest for Cd. The efficiency of strain UFLA 01-659 in removing the heavy metals is associated with its high biomass production and/or higher contents of heavy metals adsorbed and absorbed in the biomass. In response to the presence of heavy metals in the liquid culture medium, the bacteria produced exopolysaccharides and small and aggregated cells. However, these responses varied according to the strains and heavy metals. Regarding allocation, all heavy metals were adsorbed on the cell wall and membrane, whereas complexation was observed intracellularly and only for Cu and Zn. These results indicate the possibility of using C. necator UFLA 01-659 for remediation in areas with very high Cd, Cu, and Zn contents

Tolerance to and Accumulation of Cadmium, Copper, and Zinc by Cupriavidus necator

<div><p>ABSTRACT Preliminary results of in vitro experiments with multicontaminated soils and solid media indicated that nodulating diazotrophic bacteria of the genus Cupriavidus are promising for the remediation of contaminated environments due to their symbiosis with legumes and metal tolerance. Thus, strains of Cupriavidus spp. (LMG 19424T, UFLA 01-659, UFLA 01-663, and UFLA 02-71) were tested for their ability to tolerate and bioaccumulate cadmium (Cd), copper (Cu), and zinc (Zn) in Luria-Bertani broth. Changes in the growth pattern of Cupriavidus strains in the presence or absence of heavy metals were analyzed by scanning electron microscopy and metal allocation by transmission electron microscopy, to clarify the mechanisms of bioremediation. Highest tolerance was detected for strain UFLA 01-659 (minimum inhibitory concentration of 5, 4.95, and 14.66 mmol L−1 of Cd, Cu, and Zn, respectively). Among the removal rates of the metals tested (9.0, 4.6, and 3.2 mg L−1 of Cd, Cu, and Zn, respectively), the bacterial activity was clearly highest for Cd. The efficiency of strain UFLA 01-659 in removing the heavy metals is associated with its high biomass production and/or higher contents of heavy metals adsorbed and absorbed in the biomass. In response to the presence of heavy metals in the liquid culture medium, the bacteria produced exopolysaccharides and small and aggregated cells. However, these responses varied according to the strains and heavy metals. Regarding allocation, all heavy metals were adsorbed on the cell wall and membrane, whereas complexation was observed intracellularly and only for Cu and Zn. These results indicate the possibility of using C. necator UFLA 01-659 for remediation in areas with very high Cd, Cu, and Zn contents.</p></div

Structure and composition of the nematode community in a restoration area affected by iron tailings

In 2015, the Fundão Dam collapse released over 40 million m3 of iron mine tailings, causing several environmental damages. Certain affected areas were revegetated with a mix of fast-growing species that can allowed the return of some organisms of soil fauna. Nematodes are the most abundant multicellular organisms in soil and are commonly used as bioindicators. Therefore, this study aimed to use the nematode community as bioindicators of the restoration process of an area affected by iron tailings at the margins of the Gualaxo do Norte River. Soil samples were collected from affected and native forest areas to perform physical, chemical, biochemical, and biological analyses. Nematodes were identified and classified according to feeding habits and on a colonizer-persisters (cp) scale. A non-metrical multidimensional scaling and PERMANOVA were conducted to assess differences between communities. Shannon's diversity index and the maturity index were significantly higher in the restoration area. There was a difference in the composition and the structure of nematode communities of the restoration and reference area, nematode genus occurrence and abundance were different between the areas resulting in differences in feeding habits and life strategies according to the cp scale. The cp-5 nematodes are more abundant in the restoration area and cp-1 in the forest reference area. Bacterivore nematodes were more abundant in the reference forest area. In addition, the soil attributes in the restoration area were altered following the tailings deposition. Such alterations include high pH, low organic matter content, and low microbial biomass, which consequently influenced the structure and the composition of the nematode community. This is likely the first report of soil nematode community diversity in the areas of the Rio Doce Basin impacted by the Fundão tailings, and nematodes proved to be good bioindicators to show the differences between the restoration and forest reference area