Pyrolysis and Oxidation of Cellulose in a Continuous-Feed and -Flow Reactor: Effects of NaCl

Molecular turnover time of soil organic matter in particle-size fractions of an arable soil

The composition and molecular residence time of soil organic matter (SOM) in four particle-size fractions (POM >200 microm, POM 63-200 microm, silt and clay) were determined using Curie-point pyrolysis/gas chromatography coupled on-line to mass spectrometry. The fractions were isolated from soils, either continuously with a C(3) wheat (soil (13)C value = -26.4 per thousand), or transferred to a C(4) maize (soil (13)C value = -20.2 per thousand) cropping system 23 years ago. Pyrograms contained up to 45 different pyrolysis peaks; 37 (ca. 85%) were identifiable compounds. Lignins and carbohydrates dominated the POM fractions, proteins were abundant, but lignin was (nearly) absent in the silt and clay fractions. The mean turnover time (MRT) for the pyrolysis products in particulate organic matter (POM) was generally <15 years (fast C pool) and 20-300 years (medium or slow C pools) in silt and clay fractions. Methylcyclopentenone (carbohydrate) in the clay fraction and benzene (mixed source) in the silt fraction exhibited the longest MRTs, 297 and 159 years, respectively. Plant-derived organic matter was not stored in soils, but was transformed to microbial remains, mainly in the form of carbohydrates and proteins and held in soil by organo-mineral interactions. Selective preservation of plant-derived OM (i.e. lignin) based on chemical recalcitrance was not observed in these arable soils. Association/presence of C with silt or clays in soils clearly increased MRT values, but in an as yet unresolved manner (i.e. 'truly' stabilized, or potentially still 'labile' but just not accessible C).

Burning characteristics and emission products related to metallic content in incense

This study mainly compared particulate emission factors of nine popular incense. The influence of metallic contents upon the burning rate, ash and particulate emission factors of combustion was discussed. The contents of Ca and K were the highest among all metallic elements in the raw materials of the incense (the geometric mean contents 8.7 and 2.5mgg(-1), respectively), followed by Al, Mg, Fe, Na (0.1-1.0mgg(-1)) and Ba, then Sr, Mn, Cu and Zn (<0.01-0.1mgg(-1)). Most calcium existed as inorganic salts, such as CaCO(3). Under the same burning conditions, the particulate generation rates are similar (0.50mgmin(-1)+/-9%) among different types of incense-the shorter the combustion duration of a stick, the lower the total suspended particulate emission. Additionally, with the same incense weight burned, the greater the emission of ash is, the lower the emission of suspended particulate. It is recommended that consumers select incense which produces more ash, hence less particulate, to minimize the threat to their' health. Additionally, when the total metallic content (with Ca as the major component) was lower than 2% of the raw materials, properly increasing the total metallic content (from 0.5 to 2.0%) can effectively reduce the level of particulates (about 40%) during the combustion.

Interaction of Pd and PdCl2 with cellulose: a theoretical investigation

The pyrolytic fragmentation of cellulose in the presence of atomic palladium (Pd) and palladium(II) chloride (PdCl2) has been studied with use of hybrid density functional theory and cellobiose as a model for cellulose. The configuration changes in the host, rearrangement of geometries of the products, and the respective reaction energetics for different fragmentation pathways are analyzed. While Pd is found to undergo insertion at the beta-1,4-linkage oxygen (O1)-carbon (C-1) of the rings, Pd(II) chloride is observed to promote the cleavage of the chain as well as rearrangement of the rings. A detailed mechanism for the formation of levoglucosan from one of the fragments following the interaction with PdCl2 is also highlighted.