Hormesis Effect of Dichlorophenoxy Acetic Acid Sub-Doses and Mepiquat Chloride on Cotton Plant

<div><p>ABSTRACT: The aim of this study was to evaluate the hormesis effect of sub-doses of dichlorophenoxy acetic acid herbicide and the plant growth regulator mepiquat chloride on the vegetative and productive characteristics of two cotton cultivars (FMT 701 and Fibermax 966). The experiment was conducted from November 2013 to May 2014. The experimental design was a randomized block in a factorial scheme 6 x 2 x 2, with four replications, totaling 96 installments with 24 treatments: the witness and five sub-doses of the herbicide 2,4-D: 0.68, 1.36, 2.04, 2.72 and 3.40 g equivalent acid (e.a) per ha, with and without application of mepiquat chloride at a dose of 200 mL ha-1 in the cotton cultivars FMT 701 and Fibermax 966. The sub-doses applied were 2,4-D at 45 days after the emergence of the plant (DAE), and the growth regulator was applied at 70 DAE. It was found that the use of the growth regulator (mepiquat chloride) at a dose of 200 mL ha-1 was effective in controlling plant development relative to its variable height. The application of sub-doses of 2,4-D up to 1.75 g e.a ha-1 provides increased seed cotton productivity FMT 701 and Fibermax 966). The cultivar FMT 701 got greater plant height, stem diameter, number of reproductive branches, bolls per plant and seed cotton productivity compared to the cultivar Fibermax 966.</p></div

Efficiency of Zeolite Coated with Zero-Valent Iron Nanoparticles for Removal of Humic Acid from Aqueous Solutions

The most important effect of natural organic materials in water is reacting with disinfectants and creating disinfectant by-products that are mostly carcinogenic. The aim of this study was to determine the optimum conditions for removal of humic acid (HA) by zeolite coated with nZVI nanoparticles (Zeolite/nZVI) from aqueous solutions. In this study, after synthesis of zeolite/nZVI, its structure and morphology were examined using FTIR, BET, XRF, and FESEM techniques. The effects of HA concentration, composite content, pH, and reaction time were evaluated. The experimental data were analyzed by Langmuir and Freundlich isotherm and pseudo-first-order and second-order kinetic models. Finally, the thermodynamic parameters of enthalpy (ΔΗ°), entropy (ΔS°), and Gibbs free energy (ΔG°) were calculated. The results of the analyses confirmed the accuracy of the composite structure. Its specific surface area by using BET method was 203.43 m2/g. The HA removal efficiency was obtained at 92.98% in optimum conditions of 50 mg/L concentration, 2 g/L composite dose, pH = 3, and reaction time of 60 min. The results of the isotherm and kinetic study showed that the HA adsorption process follows the Langmuir isotherm (R2 = 0.9707) and pseudo-second-order kinetic. The maximum adsorption capacity of the composite was determined at 23.36 mg/g by Langmuir model. Thermodynamic parameters indicate that the adsorption of HA endothermic and the reaction cannot be done spontaneously. Zeolite/nZVI composite had good removal efficiency after five times of recycling. The present study showed that zeolite/nZVI can be used as an effective adsorbent for removal of HA from aqueous solutions

Toxicidade aguda e risco ambiental do antibiótico oxitetraciclina para tilápia ( Oreochromis niloticus ), Daphnia magna e Lemna minor

RESUMO O objetivo deste estudo foi classificar o antibiótico Terramicina(r) de acordo com a toxicidade aguda e o risco de intoxicação ambiental para Oreochromis niloticus, Daphnia magna e Lemna minor, com base no seu ingrediente ativo oxitetraciclina (OTC). Além disso, observou-se a ocorrência de sinais de intoxicação aguda em peixes e o efeito da diluição do antibiótico sobre as variáveis de qualidade de água. Alevinos, neonatos e frondes foram expostos a concentrações de OTC. De acordo com os resultados dos testes de toxicidade aguda, a Terramicina(r) foi classificada pela toxicidade aguda e pelo risco de intoxicação ambiental. Para O. niloticus, a CL(I)50; 48h calculada foi de 6,92 mg L-1, para D. magna a CE(I)50; 48h foi de 0,17mg.L-1, enquanto para L. minor a CI(I)50;7d foi de 0,68 mg L-1. A Terramicina(r) foi classificada como muito tóxica para O. niloticus e extremamente tóxica para D. magna e L. minor e causa risco de intoxicação ambiental para os três organismos testados. Concentrações de 7,5 e 8,0 mg L-1 de OTC reduziram a concentração de oxigênio dissolvido na água. De acordo com este estudo, a Terramicina(r) não deve ser utilizada na aquicultura, pois é altamente tóxica e causa risco de intoxicação ambiental aos organismos teste