Universidade Federal de Santa Maria

About: Universidade Federal de Santa Maria is a education organization based out in Santa Maria, Brazil. It is known for research contribution in the topics: Population & Context (language use). The organization has 21178 authors who have published 35632 publications receiving 371665 citations.

New insights into single-compound and binary adsorption of copper and lead ions on a treated sea mango shell: experimental and theoretical studies.

Abstract: Herein, adsorption isotherms of Pb(ii) and Cu(ii) ions on treated sea mango fruit in both single-compound and binary systems were experimentally realized at different temperatures in the range of 30-50 °C. Experimental results show that adsorption of Pb(ii) was more as compared to that of Cu(ii) ions; however, for both ions, a significant reduction in the adsorption capacity was observed in the binary system as compared to that in the single-compound systems. Moreover, under all the investigated conditions, adsorption seems to be promoted by an increase in temperature. To understand and interpret the experimental evidences, the Hill and competitive Hill models developed on the basis of the grand canonical ensemble were applied for the analysis of adsorption equilibrium data. These models contain some physicochemical parameters that allow an exhaustive analysis of the dynamics of single-compound and binary adsorptions. Based on the fitting results, in particular, through the evaluation of the number of ions bonded per site (n and ni), it was found that lead and copper ions interacted by inclined and horizontal positions on treated sea mango in single-compound and binary systems, respectively. In addition, based on the same parameters, a significant interaction between ions was retrieved. A study focused on the saturation adsorption capacity in single-compound and binary systems affirmed that the adsorbent was more selective for lead than for copper. The reduction of the adsorbed capacity ratio between the binary and single-compound systems (i.e. Qb/Qs) explained and confirmed that an inhibition effect between copper and lead ions at the same receptor site occurred. Finally, based on the energetic investigations, it was deduced that the adsorption energy represented the dominant factor promoting the greater adsorption of lead than that of copper in both systems.

Soil porosity, permeability and static and dynamic strength parameters under native forest/grassland compared to no-tillage cropping

Abstract: Improper soil management, increasing farm machinery mass and traffic frequency threaten the ecological functionality of soils under intensive agricultural use. Especially in Brazil, no-tillage (NT) cropping was adopted as a type of soil management that possibly preserves soil functions. Hence, the objective of the present study is to evaluate the effect and intensity of long-term NT compared to soil under natural forest (NF) or grassland (NG) based on parameters of composition (density, porosity, water retention) and functionality by means of mechanical strength (precompression stress σ p , cyclic compressibility c n ), air permeability K a , and saturated hydraulic conductivity k s . The studied Hapludox, Hapludalf and Quartzipsamment from southern Brazil under subtropical climate mostly reacted based upon their grain size distribution, namely clay, loamy sand and loamy fine sand. The largest impact appeared in the Hapludox, where compaction occurred (higher σ p , lower c n and smaller porosity, especially macroporosity). k s and K a were highest at the surface of the Hapludox under NF, but were reduced strongly under NT. In both the Hapludox and the Hapludalf deeper soil layers were also affected by NT, but in the clayey Hapludox the applied pressure resulted in the largest compacted layer. The Hapludalf of loamy sand texture showed, supposedly due to shallow soil operations, a weak, but permeable surface layer under NT above a dense layer, while the other layers were only slightly affected by cropping. In the Quartzipsamment, there was no increase in σ p and little in c n , whereas density in deeper layers slightly decreased. While k s was increased strongly under NT compared to NG, the opposite was found for K a which could not be explained by the investigated parameters. The results demonstrate that soil under NT might be significantly affected by soil compaction with regard to soil functions if not adequately managed by adjusted machinery. This is of even greater importance in fine-textured soils like the investigated Hapludox, compared to coarse-textured soils of poor aggregation like the investigated Quartzipsamment.

Biorremediação de solos contaminados com hidrocarbonetos aromáticos policíclicos

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are mutagenic and carcinogenic compounds to the humans and animals, released through the environment by anthropogenic activities related to the extraction, transport, refine, transformation and use of the petroleum and its derivatives. Most of the soils microorganisms do not possess the capacity to degrade them, which results in its accumulation in the atmosphere and contamination of the ecosystems. A strategy for PAHs elimination from the soil is through the bioremediation, where microorganisms having capacity to metabolize these compounds will transform them in inert substances, CO2 and water. However, this biotechnology can be limited by the lack of specific HAP microbial-degraders in soil, by unfavorable environmental conditions to these microorganisms or by the low bioavailability of those contaminants to the microorganisms. To overcome these limitations and to promote an efficient removal of the pollutants to the atmosphere, several bioremediation techniques were developed as passive bioremediation, bioaugmentation, biostimulation, phytoremediation, landfarming, composting and bioreactors. This revision aims at discussing microbial metabolism of PAHs, present the main chemical and physical factors that influence the survival and the activity of these microorganisms and to show the bioremediation techniques that are being used now for the PAHs removal in soil.