RESUMO
In environmental systems, the soil is a principal route of contamination by various potentially toxic species. Roxarsone (RX) is an arsenic (V) organic compound used to treat parasitic diseases and as an additive for animal fattening. When the animal excretes RX, the residues may lead to environmental contamination. Due to their physicochemical properties, the soil's humic substances (HS) are important in species distribution in the environment and are involved in various specific interaction/adsorption processes. Since RX, an arsenic (V) compound, is considered an emerging contaminant, its interaction with HS was evaluated in simulated environmental conditions. The HS-RX interaction was analyzed by monitoring intrinsic HS fluorescence intensity variations caused by complexation with RX, forming non-fluorescent supramolecular complexes that yielded a binding constant Kb (on the order of 103). The HS-RX interaction occurred through static quenching due to complex formation in the ground state, which was confirmed by spectrophotometry. The process was spontaneous (ΔG < 0), and the predominant interaction forces were van der Waals and hydrogen bonding (ΔH < 0 and ΔS < 0), with an electrostatic component evidenced by the influence of ionic strength in the interaction process. Structural changes in the HS were verified by synchronized and 3D fluorescence, with higher variation in the region referring to the protein-like fraction. In addition, metal ions (except ions Cu(II)) favored HS-RX interaction. When interacting with HS, the RX epitope was suggested by 1H NMR, which indicated that the entire molecule interacts with the superstructure. An enzyme inhibition assay verified the ability to reduce the alkaline phosphatase activity of free and complexed RX (RX-HS). Finally, this work revealed the main parameters associated with HS and RX interaction in simulated environmental conditions, thus, providing data that may help our understanding of the dynamics of organic arsenic-influenced soils.
Assuntos
Arsênio , Roxarsona , Poluentes do Solo , Animais , Substâncias Húmicas/análise , Solo/química , Roxarsona/química , Poluentes do Solo/análise , ÍonsRESUMO
The use of sewage sludge is a practice highly promising for the development of sustainable agricultural systems. The objective of this study was to assess the improvement in soil fertility management strategies on different sewage sludge and mineral nitrogen after seven application of this residue. The experiment was carried at the São Manuel Experimental Farm belonging to the faculty of Agronomic Sciences of UNESP, Botucatu, located in the county of São Manuel. It was adopted the experimental design in a randomized blocks consisting of six treatments and five repetitions defined as follows: T0 without nitrogen fertilizer, T1 mineral fertilizer nitrogen according to the crop needs, T2 50% nitrogen from sewage sludge and 50% in the form of chemical fertilizer, T3 100% of nitrogen recommended by the culture, from sewage sludge, T4 - 150% of nitrogen recommended by the culture, from sewage sludge and T5 200% of the nitrogen from the sewage sludge. It has done seven application of sewage sludge in crop (year 1 sunflower, year 2 sunflower, year 3 oats and bean, year 4 triticale and sunflower, year 5 wheat) and the first three applications were treated with sewage sludge and the other applications were composted sludge. In the depth 0-20 cm, the sewage sludge promoted an increase in levels of organic matter, P, S, H+Al, CEC and decreased in soil pH. In the depth of
A utilização de lodo de esgoto é uma prática promissora para o desenvolvimento de sistemas agrícolas sustentáveis. O objetivo deste trabalho foi verificar a melhoria na fertilidade do solo sobre diferentes manejos de lodo de esgoto e de nitrogênio mineral após 7 aplicações deste resíduo. O experimento foi conduzido na Fazenda Experimental São Manuel pertencente à Faculdade de Ciências Agronômicas da UNESP de Botucatu, localizada no município de São Manuel. Foi adotado um delineamento experimental em blocos casualizados constituído por 6 tratamentos e 5 repetições assim definidos: T0 - sem adubação nitrogenada, T1 - adubação química nitrogenada de acordo com a necessidade da cultura, T2 - 50% adubação nitrogenada proveniente do lodo de esgoto e 50% na forma da adubação química, T3 - 100% da adubação nitrogenada do recomendado pela cultura, proveniente do lodo de esgoto, T4 150% da adubação nitrogenada proveniente do lodo de esgoto e T5 - 200% da adubação nitrogenada proveniente do lodo de esgoto. Foram feitas sete aplicações de lodo de esgoto com as seguintes culturas (ano 1 girassol, ano 2 girassol, ano 3 - aveia e feijão, ano 4 triticale e girassol, ano 5 trigo), sendo que as três primeiras aplicações foram com lodo de esgoto tratado e as demais aplicações foram com lodo compostado. Na profundidade de 0 a 20 cm o lodo de esgoto promoveu um incremento nos teores de maté
RESUMO
The use of sewage sludge is a practice highly promising for the development of sustainable agricultural systems. The objective of this study was to assess the improvement in soil fertility management strategies on different sewage sludge and mineral nitrogen after seven application of this residue. The experiment was carried at the São Manuel Experimental Farm belonging to the faculty of Agronomic Sciences of UNESP, Botucatu, located in the county of São Manuel. It was adopted the experimental design in a randomized blocks consisting of six treatments and five repetitions defined as follows: T0 without nitrogen fertilizer, T1 mineral fertilizer nitrogen according to the crop needs, T2 50% nitrogen from sewage sludge and 50% in the form of chemical fertilizer, T3 100% of nitrogen recommended by the culture, from sewage sludge, T4 - 150% of nitrogen recommended by the culture, from sewage sludge and T5 200% of the nitrogen from the sewage sludge. It has done seven application of sewage sludge in crop (year 1 sunflower, year 2 sunflower, year 3 oats and bean, year 4 triticale and sunflower, year 5 wheat) and the first three applications were treated with sewage sludge and the other applications were composted sludge. In the depth 0-20 cm, the sewage sludge promoted an increase in levels of organic matter, P, S, H+Al, CEC and decreased in soil pH. In the depth of
A utilização de lodo de esgoto é uma prática promissora para o desenvolvimento de sistemas agrícolas sustentáveis. O objetivo deste trabalho foi verificar a melhoria na fertilidade do solo sobre diferentes manejos de lodo de esgoto e de nitrogênio mineral após 7 aplicações deste resíduo. O experimento foi conduzido na Fazenda Experimental São Manuel pertencente à Faculdade de Ciências Agronômicas da UNESP de Botucatu, localizada no município de São Manuel. Foi adotado um delineamento experimental em blocos casualizados constituído por 6 tratamentos e 5 repetições assim definidos: T0 - sem adubação nitrogenada, T1 - adubação química nitrogenada de acordo com a necessidade da cultura, T2 - 50% adubação nitrogenada proveniente do lodo de esgoto e 50% na forma da adubação química, T3 - 100% da adubação nitrogenada do recomendado pela cultura, proveniente do lodo de esgoto, T4 150% da adubação nitrogenada proveniente do lodo de esgoto e T5 - 200% da adubação nitrogenada proveniente do lodo de esgoto. Foram feitas sete aplicações de lodo de esgoto com as seguintes culturas (ano 1 girassol, ano 2 girassol, ano 3 - aveia e feijão, ano 4 triticale e girassol, ano 5 trigo), sendo que as três primeiras aplicações foram com lodo de esgoto tratado e as demais aplicações foram com lodo compostado. Na profundidade de 0 a 20 cm o lodo de esgoto promoveu um incremento nos teores de maté