Soil organic carbon stabilization mechanisms and temperature sensitivity in old terraced soils

Being the most common human-created landforms, terrace construction has resulted in an extensive perturbation of the land surface. However, our mechanistic understanding of soil organic carbon (SOC) (de-)stabilization mechanisms and the persistence of SOC stored in terraced soils is far from complete. Here we explored the factors controlling SOC stability and the temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England using soil fractionation and temperature-sensitive incubation combined with terrace soil burial-age measurements. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed relative to a control (non-terraced) profile. This suggests that the burial of former topsoil due to terracing provided a mechanism for stabilizing SOC. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral-protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction in substrate availability due to SOC mineral protection with aging attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C:N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth–age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils, and this has implications when assessing the effects of climate warming and terrace abandonment on the terrestrial C cycle.

Theoretical substantiation of optimum energy efficiency of ultrasonic wet dispersing

The known preliminary experimental results of ultrasonic dispersing of suspension were presented and analyzed. The need for determination optimum modes providing maximum energy efficiency of ultrasonic wet dispersing is justified. The physical mechanism and the theoretical model of ultrasonic dispersing were proposed. The model allows to calculate fraction composition of dispersed particles and to evaluate, that the maximum of energy efficiency exists at fixed intensity for different materials of solid particles.

SOC stabilization mechanisms and temperature sensitivity in old terraced soils

Being the most common and widest spread man-made landform, terrace construction has resulted in an extensive perturbation of the land surface. Our mechanistic understanding of soil organic carbon (SOC) (de-) stabilization mechanisms and of the persistence of SOC stored in terraced soils, however, is far from complete. Here we explored the factors controlling SOC stability and temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England, using soil fractionation and temperature sensitive incubation in combination with measurements of terrace soil burial age. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed, relative to a control (non-terraced) profile. This suggests that burial of former topsoil due to terracing provided a mechanism for enhanced C stabilization. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction of substrate availability due to SOC mineral protection with ageing attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C : N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth-age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils and this has implications when assessing the effects of climate warming or terrace abandonment on the terrestrial C cycle.

Accumulation, Translocation, and Toxicity of Arsenic in Barley Grown in Contaminated Soil

Aims Arsenic is a nonessential element for plants, however, high levels of As can inhibit plant growth. Toxicity of As is largely influenced by its speciation in soil. The objectives of the present study were to determine fractional composition of As in soil, its accumulation in plants, and toxic effects on the morphological, anatomical, and ultrastructural levels. Methods In a model experiment, barley (Hordeum sativum) was planted in Haplic Chernozem spiked with three different concentrations of As (20, 50 and 100 mg/kg). The fraction composition of As in the experimental soil was analysed using a method of sequential fractionation. The effect of As on plants was analysed microscopically at tissue, cellular, and intracellular levels.Results Analysis of the fraction composition of As revealed a higher amount of mobile forms of As that contaminated the generative organs of plants. Oxides of Fe, Al, and Mn became the main soil components to retain As when contamination of As increased. Arsenic toxicity inhibited plant growth by affecting morphological parameters (shape, size, and colour). It was shown impairment in the root cells and a reduction in the size of the chlorophyllic parenchyma in the leaves. Ultrastructural analysis found changes in the main cellular organelles (chloroplasts, mitochondria, and peroxisomes).Conclusions The bioconcentration factor (BCF), bioaccumulation factor (BF-soluble), and translocation factor (TF) allowed evaluation of plant protection mechanisms and determination of hazardous concentrations of As in soil. Despite high buffering capacity of soil, high As concentration affected morphological and ultrastructural parameters of the H. sativum.

Zero Percent of Light Products in Mazut. Illusion or Reasonable Perspective?

Yield of light products on atmospheric vacuum piepstill units is suggested to increase by means of making more heavy 95% boiling point of diesel fuel from 360°C (GOST requirements) to 365°C. Then fraction composition is getting lighter due to hydrogenating of aromatic compounds in heavy part of diesel fuel during hydrotreating. Test run confirmed the correctness of theoretical insights.

EFFECTS OF NITROGEN FERTILIZER ON FLOUR PROTEIN COMPOSITION AND DOUGH QUALITY IN WHEAT CULTIVATED IN LA PAMPA PROVINCE

Breadmaking quality of wheat flour (Triticum aestivum L.) depends not only on the genotype but also on the availability of nitrogen, and wheat protein composition is important for understanding the biochemical basis of wheat quality. The objective of this study was to evaluate the effect of nitrogen availability on flour protein fractions, to analyze their distribution and relationship with bakery quality. We worked with ACA 315 cultivar, where different application rates and timing of nitrogen nutrition were tested. Flour protein fraction composition was quantified following two protocols. Nitrogen application affected glutenin concentration and protein fraction composition favoring polymeric proteins and increasing polymeric/monomeric proteins ratio, however, increase of flour polymeric proteins did not resulted in improved rheological properties. The nitrogen added in this experiment in the differen experiments was not enough to obtain good quality bakery flours. Low protein values were obtained in grain, low gluten concentration and the dough had low W value and high P/L, being very tenacious and no very extensible. Due to low grain protein concentration farinograph parameters could not be interpreted since, under these conditions they are overestimated. These results show that not only genotypic genetic information, should be considered, also gene expression regulation in response to environmental factors, such as nitrogen availability. Therefore, genotype should continue to be studied, both at the level of variation allelic individual and in combination of different alleles of grain reserve proteins. It is also necessary to incorporate in future studies amount and timing of nitrogen application and other nutrients, such us S, in order to obtain better quality bakery flours in La Pampa province.