Mangrove forests are valuable resources in tropical and subtropical regions,which have been faced dieback due to various human activities including rapid expansion of shrimp farming,urban development,and pollution,as ...Mangrove forests are valuable resources in tropical and subtropical regions,which have been faced dieback due to various human activities including rapid expansion of shrimp farming,urban development,and pollution,as well as natural factors such as rising sea level,increasing air temperature,drought,and sharp decrease in rainfall.However,the mechanisms of dieback of mangrove forests are not well understood.Therefore,this research aimed to assess the vegetative,chemical,and physiological status of grey mangrove(Avicennia marina(Forsk.)Vierh.)forests at different intensities of dieback in the Hormozgan Province,Iran.A total of 40 plots categorized into four dieback intensities(severe,medium,low,and control)were randomly selected for monitoring,and various parameters related to vegetative,chemical,and physiological status of grey mangrove forests were examined.The results revealed that the control group had the highest tree density,seedling density,vitality levels,aerial root density,and aerial root height.Generally,as dieback severity increased,a decrease in demographic and vegetative parameters of trees and seedlings was observed in the dieback treatments.The amounts of heavy metals(lead,cadmium,and nickel)in the sediment,roots,and leaves of grey mangrove trees at different dieback levels indicated that lead levels were the highest in the sediment,roots,and leaves in the severe dieback treatment.At the same time,the control had the lowest values.Cadmium concentrations in the sediment followed the pattern of severe dieback>moderate dieback>low dieback>control with no significant differences in the roots and leaves.Nickel amounts in all three parts,i.e.,sediment,roots,and leaves showed the highest levels in the severe dieback treatment.Furthermore,metal level analysis in the organs of grey mangrove trees at different dieback levels revealed that lead and nickel were more abundant in the root organ compared with the leaves.In contrast,the leaf organ exhibited the highest cadmium levels.Dieback significantly impacted water electrical conductivity(EC),soil organic carbon(SOC),and chlorophyll a,b,and total chlorophyll contents,with the highest values observed in the severe dieback treatment.However,no significant differences were observed in acidity and carotenoid levels.In conclusion,sediment erosion and heavy metal accumulation were critical contributors to dieback of grey mangrove trees,affecting their physiological,vegetative,and plant production characteristics.As the ability of these plants to rehabilitate has diminished,effective management planning is imperative in dieback-affected areas.展开更多
This research aimed to investigate the effect of pulping conditions and refining intensities of wheat straw to be recommended for fluff pulp production.For this purpose,mono ethanol amine(MEA)was selected as a de-lign...This research aimed to investigate the effect of pulping conditions and refining intensities of wheat straw to be recommended for fluff pulp production.For this purpose,mono ethanol amine(MEA)was selected as a de-lignification agent at three levels of 50:50,25:75,and 15:85(MEA/water,W/V%),and soda-AQ 14 W/V%was used as a reference pulping.To investigate the optimal refining intensity,the obtained pulp was passed through a single disk laboratory refiner from 0 to 6 times and in two different consistencies(1.5 and 2.5 W/V%).Total yield,kappa number,ash content,and the Schopper-Riegler(SR°)freeness of the prepared pulps were investigated.Finally,hand sheets with a targeted basic weight of 70 g/m^(2) were made according to the related standards.The hand sheets were characterized using Fourier transform infrared(FTIR)spectroscopy and a field emission scanning electron microscope(FE-SEM).Sheet density,brightness,and mechanical properties such as burst,tensile,and tear indices were also investigated.The FE-SEM photographs showed that the texture of the hand sheet became denser as the refining intensity increased.External fibrillation on the surface of the fibers was also observed,especially on those refined with 2.5%consistency.The results of the chemical composition of wheat straw indicated that wheat straw containing a high percentage of holocellulose is an excellent candidate for the production of fluff pulp.The total yield and kappa number of MEA pulps increased with the decrease in MEA concentration.FTIR results indicated the presence of a peak related to amino groups in the pulp related to MEA pulp.The results also indicated that the mechanical properties of the papers,except for the tear index,were enhanced as the intensity of refining and the pulp consistency during refining increased.展开更多
In this research,some practical aspects of densified wood glulam were investigated.For this aim,poplar wood specimens were densified by hygro-thermo-mechanical technique.Glulam specimens were produced by finger joint ...In this research,some practical aspects of densified wood glulam were investigated.For this aim,poplar wood specimens were densified by hygro-thermo-mechanical technique.Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin.Physical and mechanical properties of glulams were investigated according to ASTM D 143-09,ASTM D 905-03 and ISO 8375 standards.Based on obtained results,using this process(steam and pressurize compaction)resulted in improvement of physical and mechanical prop-erties of glulam specimens.Optical microscopic and scanning electron microscopic(SEM)pictures were proved structural changes on wood material during of applied technique.Generally,the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability.This tech-nique showed a significant effect on water absorption;the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter.Also,delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination.Moreover,modulus of rupture,modulus of elasticity,shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time.Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.展开更多
文摘Mangrove forests are valuable resources in tropical and subtropical regions,which have been faced dieback due to various human activities including rapid expansion of shrimp farming,urban development,and pollution,as well as natural factors such as rising sea level,increasing air temperature,drought,and sharp decrease in rainfall.However,the mechanisms of dieback of mangrove forests are not well understood.Therefore,this research aimed to assess the vegetative,chemical,and physiological status of grey mangrove(Avicennia marina(Forsk.)Vierh.)forests at different intensities of dieback in the Hormozgan Province,Iran.A total of 40 plots categorized into four dieback intensities(severe,medium,low,and control)were randomly selected for monitoring,and various parameters related to vegetative,chemical,and physiological status of grey mangrove forests were examined.The results revealed that the control group had the highest tree density,seedling density,vitality levels,aerial root density,and aerial root height.Generally,as dieback severity increased,a decrease in demographic and vegetative parameters of trees and seedlings was observed in the dieback treatments.The amounts of heavy metals(lead,cadmium,and nickel)in the sediment,roots,and leaves of grey mangrove trees at different dieback levels indicated that lead levels were the highest in the sediment,roots,and leaves in the severe dieback treatment.At the same time,the control had the lowest values.Cadmium concentrations in the sediment followed the pattern of severe dieback>moderate dieback>low dieback>control with no significant differences in the roots and leaves.Nickel amounts in all three parts,i.e.,sediment,roots,and leaves showed the highest levels in the severe dieback treatment.Furthermore,metal level analysis in the organs of grey mangrove trees at different dieback levels revealed that lead and nickel were more abundant in the root organ compared with the leaves.In contrast,the leaf organ exhibited the highest cadmium levels.Dieback significantly impacted water electrical conductivity(EC),soil organic carbon(SOC),and chlorophyll a,b,and total chlorophyll contents,with the highest values observed in the severe dieback treatment.However,no significant differences were observed in acidity and carotenoid levels.In conclusion,sediment erosion and heavy metal accumulation were critical contributors to dieback of grey mangrove trees,affecting their physiological,vegetative,and plant production characteristics.As the ability of these plants to rehabilitate has diminished,effective management planning is imperative in dieback-affected areas.
基金This study was financially supported by Iranian National Science Foundation(project number of 4020345).
文摘This research aimed to investigate the effect of pulping conditions and refining intensities of wheat straw to be recommended for fluff pulp production.For this purpose,mono ethanol amine(MEA)was selected as a de-lignification agent at three levels of 50:50,25:75,and 15:85(MEA/water,W/V%),and soda-AQ 14 W/V%was used as a reference pulping.To investigate the optimal refining intensity,the obtained pulp was passed through a single disk laboratory refiner from 0 to 6 times and in two different consistencies(1.5 and 2.5 W/V%).Total yield,kappa number,ash content,and the Schopper-Riegler(SR°)freeness of the prepared pulps were investigated.Finally,hand sheets with a targeted basic weight of 70 g/m^(2) were made according to the related standards.The hand sheets were characterized using Fourier transform infrared(FTIR)spectroscopy and a field emission scanning electron microscope(FE-SEM).Sheet density,brightness,and mechanical properties such as burst,tensile,and tear indices were also investigated.The FE-SEM photographs showed that the texture of the hand sheet became denser as the refining intensity increased.External fibrillation on the surface of the fibers was also observed,especially on those refined with 2.5%consistency.The results of the chemical composition of wheat straw indicated that wheat straw containing a high percentage of holocellulose is an excellent candidate for the production of fluff pulp.The total yield and kappa number of MEA pulps increased with the decrease in MEA concentration.FTIR results indicated the presence of a peak related to amino groups in the pulp related to MEA pulp.The results also indicated that the mechanical properties of the papers,except for the tear index,were enhanced as the intensity of refining and the pulp consistency during refining increased.
文摘In this research,some practical aspects of densified wood glulam were investigated.For this aim,poplar wood specimens were densified by hygro-thermo-mechanical technique.Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin.Physical and mechanical properties of glulams were investigated according to ASTM D 143-09,ASTM D 905-03 and ISO 8375 standards.Based on obtained results,using this process(steam and pressurize compaction)resulted in improvement of physical and mechanical prop-erties of glulam specimens.Optical microscopic and scanning electron microscopic(SEM)pictures were proved structural changes on wood material during of applied technique.Generally,the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability.This tech-nique showed a significant effect on water absorption;the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter.Also,delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination.Moreover,modulus of rupture,modulus of elasticity,shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time.Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.