Revista Ambiente & Água - An Interdisciplinary Journal of Applied Science

1-21

Authors: Giovana Tetsuya Lopes; Jean Sérgio Rosset; Jefferson Matheus Barros Ozório; Ozielly Maiane Mendes da Silva; Wesley Vieira dos Santos; José Victor Hugo dos Santos; Andrea dos Santos Gonçalves; Eloi Panachuki

This study quantified the C content of the chemical and physical fractions of SOM in different management systems in an Argisoil of sandy texture. The study was carried out in a reference area of Native Forest (NF), and in three managed areas: Permanent Pasture (PP), No-Tillage System (NTS) and an area of Private Natural Heritage Reserve (PNHR) in the process of natural regeneration. Soil samples were collected in the layers 0.0-0.05, 0.05-0.10 and 0.10-0.20 m. We assessed the soil density (Sd), total organic carbon (TOC) content, chemical fractionation of SOM with determination of the C contents of the fulvic acids (FA), humic acids (HA) and humin (HUM), with subsequent calculations of the HA/FA ratios, AE/HUM, stock (StockC), physical granulometric fractionation and determination of C contents of particulate organic matter (C-POM) and carbon management index (CMI). Higher TOC contents were observed for the NF area. The C-HA and C-HUM contents were higher in the NF and NTS. NF showed higher C-POM levels in all layers evaluated. For the C-MOM, the NTS area was superior to the other managed areas. The managed areas had lower StockPOM values than the NF. The managed areas had lower CMI values in relation to NF. The NTS area showed that, even in crop succession, it contributes to the improvement of the soil organic fraction over the adoption time. On the other hand, the areas of PP and PNHR showed that inadequate management favors the reduction of edaphic quality.

1-11

Authors: Priscila Helena da Silva Macedo; Emily Mariano da Cruz Lopes; Mariano Vieira dos Santos de Souza Lopes; Fernando César Sala; Claudinei Fonseca Souza

In order to address issues of limited resources and contamination by fertilizers, nutrient solutions may be reused in hydroponics as an alternative to their disposal in the environment. This work evaluated the feasibility of nutrient replacement for the nutrient solutions reused during lettuce hydroponic cultivation. The experiment was carried out in an agricultural greenhouse in an NFT hydroponic system using the “Milena” lettuce cultivar. The experiment was divided into two stages: 1) monitoring and data collection and proposition of nutrient replacement management; and 2) validation of the proposed replacement management. Monitoring the consumption of the crop's nutritional solution in the first stage served as the basis for the proposed nutritional replacement management. Management was validated in the second stage through the evaluation of fresh and dry mass, crop nutritional status, and the amount of the fertilizer applied in the treatments: T1 - nutrient replacement with nutrient solution reuse; and T2 - nutrient replacement without nutrient solution reuse. The fresh and dry mass data and the amount of nutrients absorbed by the plants were submitted to the t-test at 5% probability, showing no significant difference between the treatments, making it possible to conclude that the nutrient solution reuse provided nutrient replacement during the lettuce crop cultivation.

1-12

Authors: Mariana Aguiar dos Santos; Flávia Mariani Barros; Sérgio de Sousa Castro; Fábio Orssatto

This study evaluated the efficiency of electrocoagulation in removing chemical oxygen demand (COD), turbidity, and apparent color from the incineration effluent generated in a gas cleaning system (GCS). Modeling and optimization of the variables electric current (I), hydraulic retention time (HRT), and electrode distance (ED) were also performed in a batch reactor using iron electrodes. A 23 rotatable central composite design CCRD was used, with a total of 19 trials, with electric currents ranging from 1A and 5A, a retention time of the effluent in the reactor from 15 to 40 minutes, and electrode distance of 1 and 3 centimeters. An algorithm with the desirability function was created to optimize simultaneously the parameters studied. The treatment of GCS by electrocoagulation was satisfactory in removing turbidity, apparent color, and COD, with maximum removal efficiencies above 70% for all parameters, using HRT of 27.5 minutes, ED of 2 centimeters, and electric current of 1 A. The statistical analysis showed a good fit of the model, with a coefficient of determination of R2 > 0.9. The optimum operating condition was observed at 1A electric current, 27 minutes HRT, and 2 centimeters of electrode distance, with removals of 82.07, 86.86, and 70.82% of COD, turbidity, and apparent color, respectively. The simulated trials showed that lower electrolysis times can be used without impairing the treatment efficiency. Therefore, electrocoagulation may be a potential tool in the treatment of GCS.