The quality of soil organic matter, accessed by 13C solid state nuclear magnetic resonance, is just as important as its content concerning pesticide sorption.

The global increase of food production has been achieved mainly through the intensive use of inputs such as pesticides. Once released to the soil, sorption (which could be represented by Freundlich solid-water distribution coefficients - KF) and degradation are two governing processes that determine the distribution and persistence of pesticides in the environment. In spite of the huge dataset, the only apparent generalisation is the high correlation between KF and soil organic matter (SOM) content. However, in this work no correlation was observed between KF and organic C content (OC) and so the obtained KOC (KF normalised by OC) spread out in a wide range: 1100 to 11,400 mL g-1 for abamectin; and 30-150 mL g-1 for atrazine, both ranges corroborate with data from literature. These high variabilities indicate that other soil components or SOM quality strongly interfere in the pesticide sorption in addition to SOM content. Seeking to estimate the influence of SOM quality in the abamectin and atrazine KOC values, the humic acids, a fraction of the SOM, was analysed by 13C nuclear magnetic resonance spectroscopy (13C NMR) and Principal Component (PC) Regression. The first PC of 13C NMR spectra presented negative loadings for aliphatic compounds and positive loadings for aryl C, typical of partially oxidised pyrogenic C. Their scores showed strong correlation with the abamectin KOC values (R2 = 0.91, p < 5 10-8) and weaker with atrazine KOC (R2 = 0.63, p < 0.0001), in addition to a smaller standardised slope: 1.01 for abamectin and 0.76 for atrazine. These results could be explained by the higher hydrophobicity of abamectin, being thus more prone to interact with the polycondensed aryl groups from the pyrogenic C. It is also important to highlight that humic acids are useful proxies for understanding the paramount interaction of SOM with pesticides.

Infrared spectroscopy refines chronological assessment, depositional environment and pyrolysis conditions of archeological charcoals.

Based on infrared spectral characteristics, six archeological sample sets of charcoals from German (5) and Brazilian (1) sites, covering the time span from the nineteenth century CE to 3950 BCE, were compared to a chronological (present to the fifteenth century BCE) series of Austrian charcoals. A typical chronological trend of several bands (stretch vibrations: O-C-O of carboxylates at 1,585-1,565 and 1,385-1,375 cm-1, C-O carboxylic acids at 1,260-1,250 cm-1) that indicate oxidation and subsequently increasing hydrophilicity (O-H stretch vibration at about 3,400 cm-1) was also contained in the archive samples. Three sample sets fit in the typical band development according to their age. For three sample sets this conformity was not observed. Despite the age of two sample sets (3950-2820 BCE), most charcoals were assigned to the Modern Period. Apart from the high degree of carbonization, anaerobic depositional conditions over a longer period of time seem to contribute to the surprising conservation. Non-removable mineral components in charcoals, as observed in a third sample set, strongly influence infrared band intensities and positions of organic compounds. The role of inorganic components in terms of charcoal aging, and the information we can obtain from spectral characteristics in an archeological context, are discussed.

Characterisation of the products from pyrolysis of residues after acid hydrolysis of Miscanthus.

Platform chemicals such as furfural and hydroxymethylfurfural are major products formed during the acid hydrolysis of lignocellulosic biomass in second generation biorefining processes. Solid hydrolysis residues (HR) can amount to 50 wt.% of the starting biomass materials. Pyrolysis of the HRs gives rise to biochar, bio-liquids, and gases. Time and temperature were variables during the pyrolysis of HRs in a fixed bed tubular reactor, and both parameters have major influences on the amounts and properties of the products. Biochar, with potential for carbon sequestration and soil conditioning, composed about half of the HR pyrolysis product. The amounts (11-20 wt.%) and compositions (up to 77% of phenols in organic fraction) of the bio-liquids formed suggest that these have little value as fuels, but could be sources of phenols, and the gas can have application as a fuel.

Characterization of organic matter in sediment cores of the Todos os Santos Bay, Bahia, Brazil, by elemental analysis and 13C NMR.

The impact of human activity on the sediments of Todos os Santos Bay in Brazil was evaluated by elemental analysis and 13C Nuclear Magnetic Resonance (13C NMR). This article reports a study of six sediment cores collected at different depths and regions of Todos os Santos Bay. The elemental profiles of cores collected on the eastern side of Frades Island suggest an abrupt change in the sedimentation regime. Autoregressive Integrated Moving Average (ARIMA) analysis corroborates this result. The range of depths of the cores corresponds to about 50 years ago, coinciding with the implantation of major onshore industrial projects in the region. Principal Component Analysis of the 13C NMR spectra clearly differentiates sediment samples closer to the Subaé estuary, which have high contents of terrestrial organic matter, from those closer to a local oil refinery. The results presented in this article illustrate several important aspects of environmental impact of human activity on this bay.

Pressurised pyrolysis of Miscanthus using a fixed bed reactor.

Miscanthus x giganteus was pyrolysed, in a fixed bed reactor in a constant flow of dinitrogen gas, at a rate of 13°C/min from ambient to 550°C, then held for 25 min at this temperature. The pressures employed ranged from atmospheric to 26 bar. The major compounds identified in the bio-oil were water, phenol, and phenol derivatives. The water contents impact on the usefulness of the bio-oil as a fuel. However, the phenols could provide useful platform chemicals and products. The properties of the char were determined using elemental analyses, surface area measurements using the Brunauer-Emmett-Teller equation, a calorimetric bomb, Scanning Electron Microscopy, and solid state (13)C NMR spectroscopy. The chars were highly carbonised, especially at the higher pressures, and provided thermally stable materials. Pressure impacted greatly on the surface area. Char formed at atmospheric pressure had a surface area of 162 m(2)/g, whereas that from the highest pressure applied was only 0.137 m(2)/g.