RESUMO

Organic soils are generally located in fluvial settings such as river floodplains that are commonly used for the disposal of bodies. Therefore, the aim of this study was to provide a protocol for the analysis of small amounts of organic soils for forensic purposes. The protocol was applied in five representative sites within the Curitiba metropolitan region (Brazil), with each site supplying four composite samples separated from one another by 3m. The soil samples were collected at a depth of 0 to 5cm. One gram of soil sample was used to determine the total elemental content and perform physical fractionation of the soil (>53µm and <53µm). For both soil size fractions, total C and N contents were determined, and the elements adsorbed to organic matter was determined only for the <53µm size fraction (Na-pyrophosphate extraction). Chemometric multivariate analyses were conducted for the total data set, where more than 77% of the variation was explained by the first three factors. It was determined that Ca, Ba, and Mg adsorbed to organic matter, and total Ba, Ca, K, Mg, Mo, and C contents were most important in sample groupings. As expected in forensic science, the five sites were efficiently distinguishable from each other and the four replicates collected at the same individual site were clearly grouped. This protocol for sampling, chemical analysis, and data treatment of organic soils can be used in real crime situations.

RESUMO

We evaluated the effects of the soil organic matter (SOM) composition, distribution between soil aggregates size, and their interactions with the mineral phase on herbicide sorption (alachlor, bentazon, and imazethapyr) in tropical and subtropical Oxisols under no-till systems (NT). Using soil physical fractionation approach, sorption experiments were performed on whole soils and their aggregates. SOM chemistry was assessed by CP/MAS (13)C NMR. The lower sorption observed in tropical soils was attributed to the greater blockage of SOM sorption sites than in subtropical soils. When these sites were exposed upon physical fractionation, sorption of the three herbicides in tropical soils increased, especially for imazethapyr. High amounts of poorly crystallized sesquioxides in these soils may have contributed to masking of sorption sites, indicating that organomineral interactions may lead to blockage of sorption sites on SOM in tropical soils.

Assuntos

RESUMO

We evaluated the effects of soil water content on the retention of diuron and its residual distribution into organomineral aggregates in four Brazilian oxisols. (14)C-Diuron was incubated for days at 25, 50, and 75% of maximum water-holding capacity for each soil. After 42 days, the physical fractionation method was used to obtain >150, 53-150, 20-53, 2-20, and <2 µm aggregate sizes. Diuron retention increased with increasing soil water content for all soils. At lower soil water content, diuron's retention was higher in the sandier soil. It was mostly retained in the fine (<20 µm) aggregates of sandier soil, and for clayed soils, retention was higher in the coarse aggregates (>53 µm). The sorption coefficients (Kd and Koc) generated by batch studies should be carefully used because they do not provide information about aggregation and diffusion effects on pesticides soil sorption.

Assuntos

RESUMO

The aim of this study was to investigate the behavior of the association between atrazine and glyphosate in the soil through mineralization and degradation tests. Soil treatments consisted of the combination of a field dose of glyphosate (2.88 kg ha⁻¹) with 0, ½, 1 and 2 times a field dose of atrazine (3.00 kg ha⁻¹) and a field dose of atrazine with 0, ½, 1 and 2 times a field dose of glyphosate. The herbicide mineralization rates were measured after 0, 3, 7, 14, 21, 28, 35, 42, 49, 56 and 63 days of soil application, and degradation rates after 0, 7, 28 and 63 days. Although glyphosate mineralization rate was higher in the presence of 1 (one) dose of atrazine when compared with glyphosate alone, no significant differences were found when half or twice the atrazine dose was applied, meaning that differences in glyphosate mineralization rates cannot be attributed to the presence of atrazine. On the other hand, the influence of glyphosate on atrazine mineralization was evident, since increasing doses of glyphosate increased the atrazine mineralization rate and the lowest dose of glyphosate accelerated atrazine degradation.

Assuntos