In this study, different soil Pb concentrations [24 (control), 80, 136, 362, and 1150 mg kg⁻¹] were used to analyze the tolerance threshold and accumulation potential of Brassica juncea L. in a pot experiment under greenhouse conditions. In addition to growth and Pb accumulation, the following contamination indices were calculated: transfer coefficient (TC), translocation factor (TF), and tolerance index (TI). Growth and Pb accumulation were determined at 60 days after emergence. The Pb concentrations were determined using the flame atomic absorption spectrometry (FAAS). The plant height was affected by soil Pb contamination, and it decreased from 1.37 to 0.83 m when the soil Pb concentration increased from 24 (control) to 1150 mg kg⁻¹, respectively. The Pb concentration in the shoots and roots increased as the Pb concentration in the soil increased, reaching 94 mg kg⁻¹ in shoots and 783 mg kg⁻¹ in roots when was grown under 1150 mg kg⁻¹ of Pb. TF was <1 at all levels of contamination. The TI values suggested that B. juncea presented Pb tolerance in Pb contaminated soils. Our findings indicate that B. juncea has the potential to accumulate Pb in soil under tropical conditions.

The effectiveness of açaí endocarp as biosorbent for removal of Cd²⁺, Pb²⁺ and Cr³⁺ from single solute solutions was analyzed. The biomass of açaí endocarp was characterized by scanning electron microscopy, infrared spectroscopy and determining the point of zero charge. The optimum conditions for adsorption process were obtained at solution pH 6.0 for Cd(II) removal, pH 5.0 for Pb(II) removal, and, pH 4.0 for Cr(III). Furthermore, the average optimum efficiency of biosorbent in the optimum conditions was 8, 20 and 12 g of biosorbent per litre of contaminant solution, respectively, for Cd(II), Pb(II) and Cr(III). The best dynamic equilibrium time was reached at 60 min and Langmuir's model had the best fit for Cd(II) and Cr(III) biosorption, indicating a monolayer adsorption. Freundlich's model exhibited the best fit for Pb(II) ion. Elution rates were low, indicating a strong metal interaction with the adsorbent's surface. Thermodynamic parameters showed a spontaneous and endothermal process in the case of Cd(II) and Pb(II) ions, but not for Cr(III) ion, which appears to be an exothermic process. Results show that the use of the açaí biosorbent may be a promising alternative for the remediation of polluted water, due to its low cost and highly availability.

The objective of the present study was to gather information on the effects of liming on changes in soil physical attributes. Soil acidity, caused by natural ways, such as rain, weathering and decomposition of organic matter and by human interference, by the use of nitrogen fertilizer mainly ammonia and urea fertilizer contribute to the acidification of the soil. In this context liming is perform to correct soil pH and neutralize the effect of toxic elements. Numerous benefits of liming are known, but their influence on soil physical attributes is poorly studied. Liming directly affects some physical properties of the soil, such as flocculation, aggregates, density and porosity. Flocculation of soil particles initially is smallest, which promotes greater particle dispersion. However, it changes over time, since H+ and Al3+ ions tend to be subsumed by Ca2+ and Mg2+ increasing particle flocculation power which favors its approximation and aggregate formation. For soil aggregates, surface liming in improves soil aggregation by increasing the mean aggregate diameter with positive responses as dose increases. Density and porosity of soil also undergo changes. It is important to point out that liming also has the potential to alter the porous structure of the soil. Porosity liming promotes soil density reduction and increase influenced reducing macroporosity values and increase of total porosity and micropores values. The results of studies carried out present divergent and similar results according to the evaluated physical attributes. This is possibly due to the dynamics between liming under different edaphoclimatic conditions.

The pollution of water has been one of the greatest problems faced by the modern society, due to industrialization and urban growth. Rivers, lakes and seas have been continually suffering from the rising concentration of various pollutants, especially toxic elements. This study aimed to evaluate the use of cashew nut shell (Anacardium occidentale) (CNS), after chemical modification with H₂O₂, H₂SO₄ and NaOH, as an new and renewable adsorbent material, for the removal of metals Cd²⁺, Pb²⁺ and Cr³⁺ in aqueous medium. The adsorbents were characterized by its chemical constitution, structure, infrared spectroscopy, morphology, by means of scanning electron microscopy, determination of the point of zero charge, thermogravimetrical analysis and porosimetry assessments. Tests were conducted to determine the optimal conditions (pH vs. adsorbent mass) for adsorption, by means of multivariate analysis using a central composite design. The adsorption kinetics was evaluated by models of pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion, while adsorption isotherms were linearized by Langmuir, Freundlich and Dubinin–Radushkevich. The effect of initial concentration, temperature and desorption was also performed. The adsorbents exhibited irregular, spongy and heterogeneous structure. FTIR analysis confirms the presence of hydroxyl, aliphatic, phenolic and carboxylic acid groups, which are favorable adsorption characteristics. The pH_PZC of adsorbent is 4.35, 2.50 e 6.92, respectively, for CNS H₂O₂, H₂SO₄ and NaOH. The optimum adsorption conditions were as follows: pH 5.0; relation of adsorbent mass/volume of water: 4 g L⁻¹; 40 min of contact time for reaching the equilibration. Results suggest the predominance of chemisorption of Cd²⁺ and Cr³⁺. Most of biosorbents exhibited good fit by Langmuir and Freundlich, suggesting the occurrence of adsorption on mono- and multilayers. The adsorbents of cashew nut shell exhibited high removal efficiency of Cd, Pb and Cr from waters.