Following the implementation of the strictest clean air policies to date in Beijing,the physicochemical characteristics and sources of PM_(2.5) have changed over the past few years.To improve pollution reduction polic...Following the implementation of the strictest clean air policies to date in Beijing,the physicochemical characteristics and sources of PM_(2.5) have changed over the past few years.To improve pollution reduction policies and subsequent air quality further,it is necessary to explore the changes in PM_(2.5) over time.In this study,over one year(2017-2018)field study based on filter sampling(TH-150C;Wuhan Tianhong,China)was conducted in Fengtai District,Beijing,revealed that the annual average PM_(2.5) concentration(64.8±43.1μg/m^3)was significantly lower than in previous years and the highest PM_(2.5) concentration occurred in spring(84.4±59.9μg/m^3).Secondary nitrate was the largest source and accounted for 25.7%of the measured PM_(2.5).Vehicular emission,the second largest source(17.6%),deserves more attention when considering the increase in the number of motor vehicles and its contribution to gaseous pollutants.In addition,the contribution from coal combustion to PM_(2.5) decreased significantly.During weekends,the contribution from EC and NO3−increased whereas the contributions from SO4^2−,OM,and trace elements decreased,compared with weekdays.During the period of residential heating,PM_(2.5) mass decreased by 23.1%,compared with non-heating period,while the contributions from coal combustion and vehicular emission,and related species increased.With the aggravation of pollution,the contribution of vehicular emission and secondary sulfate increased and then decreased,while the contribution of NO3−and secondary nitrate continued to increase,and accounted for 34.0%and 57.5%of the PM_(2.5) during the heavily polluted days,respectively.展开更多
Given their low cost and intrinsic safety,aqueous Zn metal batteries(AZMBs)are drawing increasing attention in the field of smart grids and large-scale energy storage.However,the Zn metal anode in aqueous electrolyte ...Given their low cost and intrinsic safety,aqueous Zn metal batteries(AZMBs)are drawing increasing attention in the field of smart grids and large-scale energy storage.However,the Zn metal anode in aqueous electrolyte suffers from a critical issue,corrosion,which must be fully addressed before the practical implementation of AZMBs.In this perspective,the mechanisms of aqueous Zn metal anode corrosion in both alkaline and neutral electrolytes are compared and discussed.The methods for studying the corrosion processes and the strategies for Zn corrosion protection in AZMBs are also summarized.Finally,some expectations about potential research directions for making corrosion-resistant AZMBs a commercial reality are provided.展开更多
为更好地认识盐蚀环境下沥青路面的性能损伤机理,在实验室内模拟除冰盐、融雪剂形成的盐蚀环境对沥青结合料的侵蚀作用。采用沥青四组分试验和原子力显微镜(atomic force microscopy,AFM)试验评价沥青的化学组分及表面微纳观形貌特性。...为更好地认识盐蚀环境下沥青路面的性能损伤机理,在实验室内模拟除冰盐、融雪剂形成的盐蚀环境对沥青结合料的侵蚀作用。采用沥青四组分试验和原子力显微镜(atomic force microscopy,AFM)试验评价沥青的化学组分及表面微纳观形貌特性。开展针入度、软化点、延度和黏度试验,探讨盐蚀环境下沥青结合料的性能演化情况。结果表明:在氯盐溶液中干湿循环和冻融循环处理后,沥青中的饱和分和芳香分含量减少,沥青质和胶质含量增加。沥青结合料表面粗糙度和蜂状结构面积百分比出现不同程度的下降。在盐蚀环境下,沥青结合料的针入度和延度均有不同程度的下降,软化点和黏度出现不同程度的升高。沥青结合料性能劣化的主要原因是在盐蚀环境中沥青的化学组分发生改变,出现一定程度的"盐老化现象"。展开更多
基金the National Natural Science Foundation of China(Nos.41805095,41705113,41877312)the Sichuan Science and Technology Program(Nos.2018SZ0288 and 2019YFS0476)+1 种基金the National Research Program for Key Is-sues in Air Pollution Control(DQGG0101)the Beijing Ma-jor Science and Technology Project(Z181100005418014)。
文摘Following the implementation of the strictest clean air policies to date in Beijing,the physicochemical characteristics and sources of PM_(2.5) have changed over the past few years.To improve pollution reduction policies and subsequent air quality further,it is necessary to explore the changes in PM_(2.5) over time.In this study,over one year(2017-2018)field study based on filter sampling(TH-150C;Wuhan Tianhong,China)was conducted in Fengtai District,Beijing,revealed that the annual average PM_(2.5) concentration(64.8±43.1μg/m^3)was significantly lower than in previous years and the highest PM_(2.5) concentration occurred in spring(84.4±59.9μg/m^3).Secondary nitrate was the largest source and accounted for 25.7%of the measured PM_(2.5).Vehicular emission,the second largest source(17.6%),deserves more attention when considering the increase in the number of motor vehicles and its contribution to gaseous pollutants.In addition,the contribution from coal combustion to PM_(2.5) decreased significantly.During weekends,the contribution from EC and NO3−increased whereas the contributions from SO4^2−,OM,and trace elements decreased,compared with weekdays.During the period of residential heating,PM_(2.5) mass decreased by 23.1%,compared with non-heating period,while the contributions from coal combustion and vehicular emission,and related species increased.With the aggravation of pollution,the contribution of vehicular emission and secondary sulfate increased and then decreased,while the contribution of NO3−and secondary nitrate continued to increase,and accounted for 34.0%and 57.5%of the PM_(2.5) during the heavily polluted days,respectively.
基金Z.Cai acknowledges the financial support from the National Natural Science Foundation of China(No.22205068)The project was supported by the"CUG Scholar"Scientific Research Funds at China University of Geosciences(Wuhan)(Project No.2022118).
文摘Given their low cost and intrinsic safety,aqueous Zn metal batteries(AZMBs)are drawing increasing attention in the field of smart grids and large-scale energy storage.However,the Zn metal anode in aqueous electrolyte suffers from a critical issue,corrosion,which must be fully addressed before the practical implementation of AZMBs.In this perspective,the mechanisms of aqueous Zn metal anode corrosion in both alkaline and neutral electrolytes are compared and discussed.The methods for studying the corrosion processes and the strategies for Zn corrosion protection in AZMBs are also summarized.Finally,some expectations about potential research directions for making corrosion-resistant AZMBs a commercial reality are provided.
文摘为更好地认识盐蚀环境下沥青路面的性能损伤机理,在实验室内模拟除冰盐、融雪剂形成的盐蚀环境对沥青结合料的侵蚀作用。采用沥青四组分试验和原子力显微镜(atomic force microscopy,AFM)试验评价沥青的化学组分及表面微纳观形貌特性。开展针入度、软化点、延度和黏度试验,探讨盐蚀环境下沥青结合料的性能演化情况。结果表明:在氯盐溶液中干湿循环和冻融循环处理后,沥青中的饱和分和芳香分含量减少,沥青质和胶质含量增加。沥青结合料表面粗糙度和蜂状结构面积百分比出现不同程度的下降。在盐蚀环境下,沥青结合料的针入度和延度均有不同程度的下降,软化点和黏度出现不同程度的升高。沥青结合料性能劣化的主要原因是在盐蚀环境中沥青的化学组分发生改变,出现一定程度的"盐老化现象"。
