Mitigation of ammonia and greenhouse gases emissions from urea coated with oil shale residues in a silvopastoral system.

The objective of this work was to investigate the viability of using retorted oil shale as urea coating (U + ROS) in the decrease of N losses by ammonia (NH3-N) volatilization. The experiment was carried out in a silvopastoral system with a randomized block design with split-plots. The main treatments consisted of spatial arrangements of the trees, while the subdivision of the plots constituted the surface application of common urea (U) and retorted oil shale-coated urea (U + ROS) for the pasture. In addition to NH3 measurements, fluxes of N2O and CH4 in the soil were determined, as well as soil moisture and contents of mineral N (0-5 cm). Independently of tree spacing, the use of ROS along with urea (U + ROS) showed a mean decrease of 15.9% in the accumulated NH3 volatilization and 24.1% in the peaks of emission, although it was not significantly different from the U treatment (P < 0.10). In addition, it did not increase significantly the N2O and CH4 emissions, evidencing a potential to decrease N losses by ammonia volatilization, with no impact on greenhouse gases emissions from the soil.

Agricultural use and pH correction of anaerobic sewage sludge with acid pH.

Agricultural use is the main way of recycling sewage sludge. Besides providing nutrients and organic matter to crops and soils, it is an important alternative for recycling this residue. However, problems during the sewage treatment process may generate sludge batches with an acidic pH. Thus, it is essential to understand the consequences of using such sludge on soils and plants, and to explore ways to overcome this limitation. The objective of this study was to evaluate addition rates of anaerobic sewage sludge (ASS) with acidic compositions on the soil fertility and performance of lettuce plants. Additionally, a methodology for pH correction of ASS with acidic pH is proposed. An agronomic experiment was conducted in a greenhouse using seven addition rates of ASS (0.0, 0.25, 0.5, 1, 2, 4 and 8 g kg-1 in dry basis), treated with an additional step of disinfection (solarization), and applied in an Albaqualf soil cultivated with lettuce (Lactuca sativa). Soil and leaf chemical composition, as well as chlorophyll index and the dry matter of lettuce leaves were evaluated. Failures during the acidogenesis phase of the anaerobic digestion process were probably the cause of ASS acidification. Although this ASS increased soil fertility indicators and plant dry matter, it significantly reduced soil pH, thereby requiring a complementary assay to correct its pH up to 6.0, which was achieved through liming. Anaerobic sewage sludges with an acidic pH can be effectively used in agriculture after being dried and disinfected through solarization, followed by pH correction, avoiding negative impacts on soil chemical attributes and plant response.

Cold finger with semi closed reflux system for sample preparation aiming at Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, V and Zn determination in Drinking Water Treatment Sludge by MIP OES.

This study presents method development and optimization, based on statistical approaches, of an alternative sample preparation methodology for Drinking Water Treatment Sludge, through decomposition in semi closed system with cold finger, aiming at the determination of Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, V and Zn by microwave induced plasma optical emission spectrometry. This system was employed to decompose three different Drinking Water Treatment Sludge samples, from three different treatment plants. The compromise conditions were 250 mg of dried sample, 5 mL of HNO3, 1 mL of H2SO4 and heating at 225 °C for 150 min. After the digestion, 1% of cesium and lanthanum chloride buffer solution was added to all samples and standard solutions. The accuracy of the proposed sample preparation method was evaluated by analyzing a sediment certified reference material (CRM NIST 1646a) as well as the spike recovery technique. The recoveries ranged from 83% to 119% for all elements, and the found concentrations for the CRM agreed with the respective certified values, at 95% confidence level. The correlation coefficients for all investigated elements were higher than 0.999. The method LOQ values were adequate and complied with the Drinking Water Treatment Sludge regulation avaliable, ranging from 0.3 (V) and 32 (Zn) µg L-1, or 0.1 (V) to 13 (Zn) mg kg-1. The digestion procedure in acidic medium showed suitable to measure the analytes in the investigated matrix by microwave induced plasma optical emission spectrometry.