Characterization of Biobased Polyurethane Foams Employing Lignin Fractionated from Microwave Liquefied Switchgrass

Lignin samples fractionated from microwave liquefied switchgrass were applied in the preparation of semirigid polyurethane (PU) foams without purification. The objective of this study was to elucidate the influence of lignin in the PU matrix on the morphological, chemical, mechanical, and thermal properties of the PU foams. The scanning electron microscopy (SEM) images revealed that lignin with 5 and 10% content in the PU foams did not influence the cell shape and size. The foam cell size became larger by increasing the lignin content to 15%. Fourier transform infrared spectroscopy (FTIR) indicated that chemical interactions occurred between the lignin hydroxyl and isocyanate revealing that lignin was well dispersed in the matrix materials. The apparent density of the foam with 10% lignin increased by 14.2% compared to the control, while the foam with 15% lignin had a decreased apparent density. The effect of lignin content on the mechanical properties was similar to that on apparent density. The lignin containing foams were much more thermally stable than the control foam as evidenced by having higher initial decomposition temperature and maximum decomposition rate temperature from the thermogravimetric analysis (TGA) profiles

Chemical constituents of <i>Cinnamomum septentrionale</i> leaf litter and its allelopathic activity on the growth of maize (<i>Zea mays</i>)

<p>A pot experiment was conducted to study the effect of decomposing <i>Cinnamomum septentrionale</i> leaf litter on the growth of maize. In this study, the morphological traits of maize were significantly inhibited when the leaf litter amount reached or exceeded 40 g per pot; Furthermore, during the early growth stage or with a large amount of litter addition, the pigment contents were inhibited by <i>C. septentrionale</i> leaf litter. Gas chromatography–mass spectrometry was used to determine the volatile substances of leaf litter and 34 compounds were identified, several of which were reported to be phytotoxic. In conclusion, the leaf litter of <i>C. septentrionale</i> showed a strong allelopathic effect on the growth of maize. Thus, it is better to avoid the growing of maize under or near the <i>C. septentrionale</i> plantation unless the leaf litter could be eliminated in time or other effective leaf litter processing methods could be implemented.</p

Effect of Slope, Rainfall Intensity and Mulch on Erosion and Infiltration under Simulated Rain on Purple Soil of South-Western Sichuan Province, China

Purple soil is widely distributed in the hilly areas of the Sichuan basin, southwest China, and is highly susceptible to water erosion. The triggering of this process is related to slope, rainfall intensity and surface cover. Therefore, this study assesses the effects of different simulated rainfall intensities with different slopes on hydrological and erosional processes in un-mulched and mulched purple soils. Results show that the sediment and water losses increased with an increase of rainfall intensity and slope steepness. Generally, the slope contribution (Sc) on water and sediment losses decreased with increasing rainfall intensity and slope steepness under both un-mulched and mulched soil. In un-mulched conditions, water losses were independent of slope steepness (Sc &lt; 50%) during the highest rainfall intensity. However, in mulched soil, the higher contributions of slope (Sc) and rainfall (Rc) were found for water and sediment losses, respectively, i.e., &gt;50%, except during the increase in slope steepness from 15° to 25° under the highest rainfall intensity (120 mm·h−1). The effectiveness of mulch was more pronounced in reducing sediment losses (81%–100%) compared with water losses (14%–100%). The conservation effectiveness of mulch both decreased and increased with slope steepness for water and sediment losses, respectively, under higher rainfall intensities. Water infiltration and recharge coefficient (RC) decreased with an increase of slope steepness, while with an increase in rainfall intensity, the water infiltration and RC were increased and decreased, respectively, in both un-mulched and mulched soil. On the other hand, mulched soil maintained a significantly (α = 0.05) higher infiltration capacity and RC compared to that of the un-mulched soil

Allelopathic activity and chemical constituents of walnut (<i>Juglans regia</i>) leaf litter in walnut–winter vegetable agroforestry system

<div><p>Walnut agroforestry systems have many ecological and economic benefits when intercropped with cool-season species. However, decomposing leaf litter is one of the main sources of allelochemicals in such systems. In this study, lettuce (<i>Lactuca sativa</i> var. <i>angustata</i>) was grown in the soil incorporated with walnut leaf litter to assess its allelopathic activity. Lettuce growth and physiological processes were inhibited by walnut leaf litter, especially during early growth stage (1–2 euphylla period) or with large amount of litter addition. The plants treated by small amount of leaf litter recovered their growth afterwards, while the inhibition for 180 g leaf litter persisted until harvest. Twenty-eight compounds were identified in the leaf litter, and several of them were reported to be phytotoxic, which may be responsible for the stress induced by walnut leaf litter. Thus, for highest economic value of vegetables such as lettuce, excessive incorporation of leaf litter should be discouraged.</p></div