Biochar from slow pyrolysis under controlled conditions is favorable in the transformation of waste into materials that serve as soil conditioners, and/or environmental remediation. Thus, this work aimed to produce and characterize biochar from cassava waste under different temperature conditions and evaluate interactions with Ca2+ and Pb2+ for agricultural and environmental applications. To investigate the efficiency of the interaction of biochar with nutrients (Ca) and contaminants (Pb), the influence of pH and contact time were evaluated. There was an increase in pH, pHzpc (zero point charge), and condensed aromatic structures in BC, due to the increase in pyrolysis temperature. Also, biochar demonstrated a Pb2+ adsorbed amount of 2.03 to 2.37 mg g-1 and a Ca2+ release capacity of 0.655 to 0.765 mg g-1. In this way, biochar produced from residues of cassava waste can be a viable strategy to enhance agricultural production and reduce environmental contaminants.

Alkaline extractions from humic material are used to risk assessment in soils. However, there are questions about the type of extraction most suitable for this evaluation. Thus, this work evaluated different soil extractions in search of realistic environmental conditions (simulated rain). The parameters obtained revealed significant differences between the levels and structural characteristics of organic matter, depending on the extractant used, reinforcing the importance of developing methodologies and analytical procedures that minimize structural changes and may be more representative of the molecular structures of organic matter found in soils. The results showed that the material extracted by simulated rain is similar to the fulvic acids of the soil organic matter extracted by alkaline extraction showing the importance of this type of extraction for risk assessment studies in soils.

The suspended particulate material (SPM) present in waters has fundamental importance for a better understanding of environmental behaviors of aquatic pollutants. This work determined the physicochemical parameters (pH, temperature, conductivity, total organic carbon and metals concentration) in water samples from Mundaú-Manguaba estuarine-lagoon system, Alagoas, Brazil. This work extracted and characterized the organic matter present in SPM in this estuary and studied the interaction of this organic matter with potentially toxic metals (Cd2+ and Pb2+). The results of the physical-chemical parameters evaluated showed influence of the tide and also of anthropic contributions close to the estuary. In fact, the lead concentrations determined (0.10-1.32 mg L-1) are well above that allowed by Brazilian legislation (< 0.010 mg L-1). The organic matter present in the SPM showed a high degree of humification being similar to the organic matter extracted from water and showed strong interaction by Pb2+ ions.

A simple, fast and inexpensive method was developed to determine essential elements in pellets of rice samples using energy dispersive X-ray fluorescence spectrometry (EDXRF). The accuracy and precision were evaluated using Standard Reference Material (rice flour NIST 1568a), and yielding relative standard deviation below 5%. The paired t-test showed good agreement within 95% confidence values. The detection limits (3σ) of Mn and Zn were 5.1 and 2.2 mg kg-1, respectively. The proposed method proved to be effective when used to determine Mn and Zn in commercial samples of rice without go by stage of decomposition.