The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies ...The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources： mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope（δ13Corg） and the molar ratio of total organic carbon to total nitrogen（C/N）. The percentage of mangrove-derived organic matter（MOM） contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.展开更多
The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis se...The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter（NOM）. The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms（using QST3 method） of the photosensitive degradation products were analyzed. The results showed that（i） the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;（ii） the degradation activities（i.e., C–Cl bond cleavage energies） were the same for both degradation pathways and followed the order ortho 〉 meta 〉 para;（iii） the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;（iv） there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;（v） the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and（vi） even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.展开更多
The hypoxic phenomena of seawater have been found in the Changjiang esturay and its adjacent area for several decades. To study organic matter degradation in seasonal hypoxic seawater, series of stimulated incubation ...The hypoxic phenomena of seawater have been found in the Changjiang esturay and its adjacent area for several decades. To study organic matter degradation in seasonal hypoxic seawater, series of stimulated incubation experiments with S keletonema costatum in seawater under different oxygen saturations were conducted. By tracking variations of lipids originated from the alga, time-dependent concentrations of neutral lipids(hexadecanol, otctadecanol, cholesterol, brassicasterol and phytol) and fatty acids(12:0, 14:0, 16:0, 16:1, 18:0, 18:1(9), 20:5 and 22:6) were obtained during three month of incubation. The results indicate that residence time, oxygen saturation, bacterial community and the structure of lipids were key factors controlling preservation and degradation of lipids in seawater. The degradation rate constants calculated from multi-G model showed that under same oxygen saturation, algal fatty acid degraded faster than neutral lipids, and unsaturated fatty acids degraded faster than saturated fatty acids. Our new discovery showed that degradation rate constant had linear positive correlation with oxygen saturation of seawater, indicating the critical role of oxygen on degradation of algal lipids in hypoxic seawater. The results of this study will be helpful to understand organic carbon cycling in seawater and marine environment more deeply. Future field experiments and investigation should be conducted tracking control factors, especially the role of oxygen saturation on organic matter degradation in natural environment.展开更多
Microbial activity and interaction are the important driving factors in the start-up phase of food waste composting at low temperature.The aim of this study was to explore the effect of inoculating Bacillus lichenifor...Microbial activity and interaction are the important driving factors in the start-up phase of food waste composting at low temperature.The aim of this study was to explore the effect of inoculating Bacillus licheniformis on the degradation of organic components and the potential microbe-driven mechanism from the aspects of organic matter degradation,enzyme activity,microbial community interaction,and microbial metabolic function.The results showed that after inoculating B.licheniformis,temperature increased to 47.8℃ on day2,and the degradation of readily degraded carbohydrates(RDC)increased by 31.2%,and the bioheat production increased by 16.5%.There was an obvious enhancement of extracellular enzymes activities after inoculation,especially amylase activity,which increased by 7.68 times on day 4.The inoculated B.licheniformis colonized in composting as key genus in the start-up phase.Modular network analysis and Mantel test indicated that inoculation drove the cooperation between microbial network modules who were responsible for various organic components(RDC,lipid,protein,and lignocellulose)degradation in the start-up phase.Metabolic function prediction suggested that carbohydrate metabolisms including starch and sucrose metabolism,glycolysis/gluconeogenesis,pyruvate metabolism,etc.,were improved by increasing the abundance of related functional genes after inoculation.In conclusion,inoculating B.licheniformis accelerated organic degradation by driving the cooperation between microbial network modules and enhancing microbial metabolism in the start-up phase of composting.展开更多
基金The National Basic Research Program (973 Program) of China under contract No.2010CB951203the National Natural Science Foundation of China under contract Nos 41376075,41576061 and 41206057
文摘The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources： mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope（δ13Corg） and the molar ratio of total organic carbon to total nitrogen（C/N）. The percentage of mangrove-derived organic matter（MOM） contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.
基金supported by the Fundamental Research Funds for the Central Universities in 2013(JB2013146)the Key Projects in the National Science&Technology Pillar Program in the Eleventh Five-Year Plan Period(2008BAC43B01)
文摘The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter（NOM）. The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms（using QST3 method） of the photosensitive degradation products were analyzed. The results showed that（i） the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;（ii） the degradation activities（i.e., C–Cl bond cleavage energies） were the same for both degradation pathways and followed the order ortho 〉 meta 〉 para;（iii） the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;（iv） there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;（v） the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and（vi） even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.
基金Supported by the National Natural Science Foundation of China for Creative Groups(No.41521064)the National Natural Science Foundation of China(No.41676067)+2 种基金the Fundamental Funds for Central Universities(No.201762030)the National Key Research and Development Program of China(No.2016YFA0601302)the Natural Science Foundation of Shandong Province(No.ZR2010DM001)
文摘The hypoxic phenomena of seawater have been found in the Changjiang esturay and its adjacent area for several decades. To study organic matter degradation in seasonal hypoxic seawater, series of stimulated incubation experiments with S keletonema costatum in seawater under different oxygen saturations were conducted. By tracking variations of lipids originated from the alga, time-dependent concentrations of neutral lipids(hexadecanol, otctadecanol, cholesterol, brassicasterol and phytol) and fatty acids(12:0, 14:0, 16:0, 16:1, 18:0, 18:1(9), 20:5 and 22:6) were obtained during three month of incubation. The results indicate that residence time, oxygen saturation, bacterial community and the structure of lipids were key factors controlling preservation and degradation of lipids in seawater. The degradation rate constants calculated from multi-G model showed that under same oxygen saturation, algal fatty acid degraded faster than neutral lipids, and unsaturated fatty acids degraded faster than saturated fatty acids. Our new discovery showed that degradation rate constant had linear positive correlation with oxygen saturation of seawater, indicating the critical role of oxygen on degradation of algal lipids in hypoxic seawater. The results of this study will be helpful to understand organic carbon cycling in seawater and marine environment more deeply. Future field experiments and investigation should be conducted tracking control factors, especially the role of oxygen saturation on organic matter degradation in natural environment.
基金supported by the Open Research Fund Program of State Environmental Protection Key Laboratory of Food Chain Pollution Control(No.FC2022YB01)the National Natural Science Foundation of China(No.32071552)+1 种基金the Independent Research Project of Science and Technology Innovation Base in Tibet Autonomous Region(No.XZ2022JR0007G)China Agricultural University-Dabeinong Group Professional degree graduate joint training reform project(No.CAUDBN PDG-JTRP).
文摘Microbial activity and interaction are the important driving factors in the start-up phase of food waste composting at low temperature.The aim of this study was to explore the effect of inoculating Bacillus licheniformis on the degradation of organic components and the potential microbe-driven mechanism from the aspects of organic matter degradation,enzyme activity,microbial community interaction,and microbial metabolic function.The results showed that after inoculating B.licheniformis,temperature increased to 47.8℃ on day2,and the degradation of readily degraded carbohydrates(RDC)increased by 31.2%,and the bioheat production increased by 16.5%.There was an obvious enhancement of extracellular enzymes activities after inoculation,especially amylase activity,which increased by 7.68 times on day 4.The inoculated B.licheniformis colonized in composting as key genus in the start-up phase.Modular network analysis and Mantel test indicated that inoculation drove the cooperation between microbial network modules who were responsible for various organic components(RDC,lipid,protein,and lignocellulose)degradation in the start-up phase.Metabolic function prediction suggested that carbohydrate metabolisms including starch and sucrose metabolism,glycolysis/gluconeogenesis,pyruvate metabolism,etc.,were improved by increasing the abundance of related functional genes after inoculation.In conclusion,inoculating B.licheniformis accelerated organic degradation by driving the cooperation between microbial network modules and enhancing microbial metabolism in the start-up phase of composting.
