亚热带常绿阔叶林林分结构对物种组成变异的驱动作用:从局域到区域尺度

林分结构可以表征森林群落光的可利用性和光环境的异质性,对群落物种组成的变异具有重要驱动作用。然而,目前还鲜有研究将林分结构用于解释群落物种组成的变异。本研究以哀牢山亚热带中山湿性常绿阔叶林20 ha森林动态监测样地及其周边区域按公里网格设置的19个1 ha森林动态样地为研究对象,将林分结构参数、环境因子和空间结构变量共同作为解释变量,采用基于冗余分析的变差分解和层次分割方法,在局域和区域尺度上同时解析群落物种组成变异的驱动因素。结果表明,在局域和区域尺度上,纳入林分结构后均提高了对物种组成变异的解释率。在局域尺度上,加入林分结构作为解释变量后,单纯的空间结构的解释率明显下降,林分结构与环境因子累计贡献了41.0%的解释率。在区域尺度上,林分结构与环境因子累计贡献了23.0%的解释率。从局域到区域尺度,环境过滤的相对作用明显增强。林分结构指示的光的可利用性对林冠下方的树种组成具有较强的塑造作用,今后的研究应进一步探讨林分结构对亚热带常绿阔叶林物种组成变异的驱动机制。

Real-world emission characteristics of carbonyl compounds from agricultural machines based on a portable emission measurement system

Emissions of carbonyl compounds from agricultural machines cannot be ignored.Carbonyl compounds can cause the formation of ozone(O3)and secondary organic aerosols,which can cause photochemical smog to form.In this study,20 agricultural machines were tested using portable emission measurement system(PEMS)under real-world tillage processes.The exhaust gases were sampled using 2,4-dinitrophenylhydrazine cartridges,and 15 carbonyl compounds were analyzed by high-performance liquid chromatography.Carbonyl compound emission factors for agricultural machines were 51.14–3315.62 mg/(kg-fuel),and were 2.58±2.05,0.86±1.07 and 0.29±0.20 g/(kg-fuel)for China 0,China II and China III emission standards,respectively.Carbonyl compound emission factor for sowing seeds of China 0 agricultural machines was 3.32±1.73 g/(kg-fuel).Formaldehyde,acetaldehyde and acrolein were the dominant carbonyl compounds emitted.Differences in emission standards and tillage processes impact ozone formation potential(OFP).The mean OFP was 20.15±16.15 g O3/(kg-fuel)for the China 0 emission standard.The OFP values decreased by 66.9% from China 0 to China II,and 67.4%from China II to China III.The mean OFP for sowing seeds of China 0 agricultural machines was 25.92±13.84 g O3/(kg-fuel).Between 1.75 and 24.22 times more ozone was found to be formed during sowing seeds than during other processes for China 0 and China II agricultural machines.Total carbonyl compound emissions from agricultural machines in China was 19.23 Gg in 2019.The results improve our understanding of carbonyl compound emissions from agricultural machines in China.

Chemical characterization of volatile organic compounds (VOCs) emitted from multiple cooking cuisines and purification efficiency assessments

Cooking process can produce abundant volatile organic compounds(VOCs),which are harmful to environment and human health.Therefore,we conducted a comprehensive analysis in which VOCs emissions from multiple cuisines have been sampled based on the simulation and acquisition platform,involving concentration characteristics,ozone formation potential(OFP)and purification efficiency assessments.VOCs emissions varied from 1828.5 to 14,355.1μg/m^(3),with the maximumand minimumvalues fromBarbecue and Family cuisine,respectively.Alkanes and alcohol had higher contributions to VOCs from Sichuan and Hunan cuisine(64.1%),Family cuisine(66.3%),Shandong cuisine(69.1%)and Cantonese cuisine(69.8%),with the dominant VOCs species of ethanol,isobutane and n-butane.In comparison,alcohols(79.5%)were abundant for Huaiyang cuisine,while alkanes(19.7%),alkenes(35.9%)and haloalkanes(22.9%)accounted for higher proportions from Barbecue.Specially,carbon tetrachloride,n-hexylene and 1-butene were the most abundant VOCs species for Barbecue,ranging from 8.8%to 14.6%.The highest OFP occurred in Barbecue.The sensitive species of OFP for Huaiyang cuisine were alcohols,while other cuisines were alkenes.Purification efficiency assessments shed light on the removal differences of individual and synergistic control technologies.VOCs emissions exhibited a strong dependence on the photocatalytic oxidation,with the removal efficiencies of 29.0%–54.4%.However,the high voltage electrostatic,wet purification and mechanical separation techniques played a mediocre or even counterproductive role in the VOCs reduction,meanwhile collaborative control technologies could not significantly improve the removal efficiency.Our results identifiedmore effective control technologies,which were conductive to alleviating air pollution from cooking emissions.

哀牢山亚热带中山湿性常绿阔叶林树种beta多样性格局形成的驱动力

Beta多样性通常指群落在时间和空间上物种组成的差异,包括物种周转组分和物种丰富度差异组分。驱动beta多样性格局形成的生态过程决定了群落的时空动态,然而关于beta多样性及其两个组分格局形成的驱动力还存在较多争议。以往研究表明,beta多样性的格局存在取样尺度的依赖性,驱动其形成的生态过程在不同取样尺度下的相对重要性也随之改变。本研究以哀牢山亚热带中山湿性常绿阔叶林20 ha动态监测样地为研究对象,在不同取样尺度上,将样方间的Bray-Curtis指数分解为物种周转组分和物种丰富度差异组分,通过典范冗余分析和方差分解的方法揭示环境过滤和扩散限制对于beta多样性及其两个组分格局形成的相对重要性及其尺度依赖性。结果表明:(1)beta多样性、物种周转组分和物种丰富度差异组分均随取样尺度的增大而减小。在不同取样尺度下,物种周转组分对于beta多样性的贡献始终占主导地位。(2)随着取样尺度的增大,环境过滤驱动beta多样性格局形成的相对重要性逐渐增加,而扩散限制的相对重要性逐渐降低。本研究进一步证实了取样尺度在beta多样性格局形成及其驱动力定量评价中的重要性,今后的研究需要进一步解析上述尺度效应的形成机制。

Development of database of real-world diesel vehicle emission factors for China

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT（Computer Programmer to calculate Emissions from Road Transport） and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5（Highway Vehicle Particulate Emission Modeling Software） models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent,which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.

Variation characteristics of fine particulate matter and its components in diesel vehicle emission plumes

A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.