Chemical changes and heavy metal partitioning in an oxisol cultivated with maize (Zea mays, L.) after 5 years disposal of a domestic and an industrial sewage sludge.

The need for solutions to minimize the negative environmental impacts of anthropogenic activities Fhas increased. Sewage sludge is composed of predominantly organic matter and can be used to improve soil characteristics, such as fertility. Therefore, its application in agriculture is an adequate alternative for its final disposal. However, there is a lack of information on its long-term effects on soil changes in tropical areas. Thus, the objectives of this study were to determine (i) the effect of sewage sludge application on heavy metal build-up in soil and maize grains and leaves, and (ii) the effects of soil amendment with sewage sludge on the chemical properties of a Brazilian oxisol. Besides the increasing levels of Zn, Cu, Ni, and Cr, amending soil with sewage sludge also alters the distribution of these metals by increasing the mobile Phases, which correlated significantly with the increase in metal extraction with two single extractants, Mehlich 1 and DTPA (Diethylene triamine pentaacetic acid). The levels of Fe, Mn, Zn, and Cu in maize grains and leaves increased with the type and rate of sewage sludge application. Nevertheless, metal build-up in soil and plants was within the allowed limits. Significant differences were also found in soil characteristics like humic fractionation with the applied sewage doses. The data obtained does not indicate any expressive drawbacks in the use of sewage sludge as a soil amendment, as the heavy metal concentrations observed are unlikely to cause any environmental or health problems, even overestimated loadings, and are in accordance with the Brazilian regulations on farming land biosolid disposal.

Sequential exhaustive extraction of a Mollisol soil, and characterizations of humic components, including humin, by solid and solution state NMR.

A comprehensive sequential extraction procedure was applied to isolate soil organic components using aqueous solvents at different pH values, base plus urea (base-urea), and finally dimethylsulfoxide (DMSO) plus concentrated H2SO4 (DMSO-acid) for the humin-enriched clay separates. The extracts from base-urea and DMSO-acid would be regarded as 'humin' in the classical definitions. The fractions isolated from aqueous base, base-urea and DMSO-acid were characterized by solid and solution state NMR spectroscopy. The base-urea solvent system isolated ca. 10% (by mass) additional humic substances. The combined base-urea and DMSO-acid solvents isolated ca. 93% of total organic carbon from the humin-enriched fine clay fraction (<2 ?m). Characterization of the humic fractions by solid-state NMR spectroscopy showed that oxidized char materials were concentrated in humic acids isolated at pH 7, and in the base-urea extract. Lignin-derived materials were in considerable abundance in the humic acids isolated at pH 12.6. Only very small amounts of char-derived structures were contained in the fulvic acids and fulvic acids-like material isolated from the base-urea solvent. After extraction with base-urea, the 0.5 m NaOH extract from the humin-enriched clay was predominantly composed of aliphatic hydrocarbon groups, and with lesser amounts of aromatic carbon (probably including some char material), and carbohydrates and peptides. From the combination of solid and solution-state NMR spectroscopy, it is clear that the major components of humin materials, from the DMSO-acid solvent, after the exhaustive extraction sequence, were composed of microbial and plant derived components, mainly long-chain aliphatic species (including fatty acids/ester, waxes, lipids and cuticular material), carbohydrate, peptides/proteins, lignin derivatives, lipoprotein and peptidoglycan (major structural components in bacteria cell walls). Black carbon or char materials were enriched in humic acids isolated at pH 7 and humic acids-like material isolated in the base-urea medium, indicating that urea can liberate char-derived material hydrogen bonded or trapped within the humin matrix.

Desenvolvimento e validação de métodos para a determinação de agrotóxicos em água e solo das áreas de recarga de Aquífero Guarani, na região das nascentes do Rio Araguaia, MT/GO.

Abstract: The area near the Araguaia River, between Goiás and Mato Grosso States, is the location of a portion of the recharging of the Guarani Aquifer, which is one of the world¿s largest aquifer systems and an important source of drinking water. This reservoir could be threatened by the widespread use of pesticides in maize and soybean cultivation in this area. Thus, this work developed analytical methods for the determination of imazethapyr, nicosulfuron, imazaquin, carbofuran, atrazine, linuron, clorimuronethyl and diflubenzuron, pesticides used in maize and soybean cultivation. Pesticide separation, identification and quantification were performed using High-Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) and Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry (LC-ESI-MS/MS). Solid Phase Extraction (SPE) with C18 sorbents was optimized for sample extraction from water. Soil samples were extracted by mechanical shaking, sonication or microwave-assisted extraction with industrial and home microwave ovens. Methods were validated resulting in limits of quantification (LOQ) for the pesticides in water in the range of 0.015-0.1 ng mL, using SPE-HPLC-DAD, and 0.01 ng mL using LC-ESI-MS/MS. LOQ of 1 ng mL for all pesticides in soil were achieved using the home microwave oven and LC-ESI-MS/MS. Recoveries for pesticides with all methods were in the range 70-120 %. Relative standard deviations for repeatability and intermediate precision were less than 15 %. SPEHPLC- DAD and LC-ESI-MS/MS were employed for the analysis of samples of water from the recharge area and most of the pesticides were detected at concentrations below the minimum residue limit (MRL) of 0.1 ng mL established by the European Community. The home microwave oven and LC-ESI-MS/MS were used for the analysis of soil samples from two other regions of Brazil and the pesticides were not detected in these samples. Adsorption and desorption parameters were determined for imazethapyr, imazaquin, nicosulfuron and chlorimuron-ethyl, indicating that these pesticides have little affinity for the soil of the region of the Guarani Aquifer recharge, and show significant leaching potential, according to the ground water ubiquity score (GUS index) for these pesticides.