Recent Advances in Mechanistic Understanding of Metal-Free Carbon Thermocatalysis and Electrocatalysis with Model Molecules

Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Over the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms.However,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods.In this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon catalysis.Using both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically studied.Combined with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level.Furthermore,the outlook of model carbon catalysis has also been proposed in this work.

Urban Three-dimensional Expansion and Its Driving Forces——A Case Study of Shanghai,China

Urban expansion is a phenomenon of urban space increase,and an important measuring index of the process of urbanization.Taking Shanghai as an example,the changes of urban average height and built-up area were studied to represent city's vertical and horizontal increases respectively,and statistical methods were used to analyze the driving forces of urban expansion.The research drew following conclusions:1) The urban expansion process of Shanghai from 1985 to 2006 had a clear periodic feature,and could be divided into three stages:vertical expansion in dominance,coordinated vertical and horizontal expansion,and horizontal expansion in dominance.2) The average height and quantity of buildings in core city were significantly bigger than those in suburbs,but the changing speed of the latter was faster.And 3) urbanization process was the major driving force for the city's horizontal expansion,while industrial structure improvement was the key driving factor for the vertical expansion.Those two driving forces were simultaneously affected by city's political factors.

Distributions of typical contaminant species in urban short-term storm runoff and their fates during rain events:A case of Xiamen City

The pollutants in urban storm runoff, which lead to an non-point source contamination of water environment around cities, are of great concems. The distributions of typical contaminants and the variations of their species in short term storm runoff from different land surfaces in Xiamen City were investigated. The concentrations of various contaminants, including organic matter, nutrients （i.e., N and P） and heavy metals, were significantly higher in parking lot and road runoff than those in roof and lawn runoff. The early runoff samples from traffic road and parking lot contained much high total nitrogen （TN 6-19 mg/L） and total phosphorus （TP 1-3 mg/L）. A large proportion （around 60%） of TN existed as total dissolved nitrogen （TDN） species in most runoff. The percentage of TDN and the percentage of total dissolved phosphorus remained relatively stable during the rain events and did not decrease as dramatically as TN and TP. In addition, only parking lot and road runoff were contaminated by heavy metals, and both Pb （25-120 μg/L） and Zn （0.1-1.2 mg/L） were major heavy metals contaminating both runoff. Soluble Pb and Zn were predominantly existed as labile complex species （50%-99%）, which may be adsorbed onto the surfaces of suspended particles and could be easily released out when pH decreased. This would have the great impact to the environment.

A New Carbon and Oxygen Balance Model Based on Ecological Service of Urban Vegetation

The application of human induced oxygen consumption and carbon emission theory in urban region was summed up and on this base a new model of urban carbon and oxygen balance (UCOB) was constructed by calculating the carbon and oxygen fluxes. The purpose was to highlight the role of vegetation in urban ecosystems and evaluate the effects of various human activities on urban annual oxygen consumption and carbon emission. Hopefully,the model would be helpful in theory to keep the regional balance of carbon and oxygen,and provide guidance and support for urban vegetation planning in the future. To test the UCOB model,the Jimei District of Xiamen City,Fujian Province,China,a very typical urban region,was selected as a case study. The results turn out that Jimei′s vegetation service in oxygen emission and carbon sequestration could not meet the demand of the urban population,and more than 31.49 times of vegetation area should be added to meet the whole oxygen consumption in Jimei while 9.60 times of vegetation area are needed to meet the carbon sequestration targets. The results show that the new UCOB model is of a great potential to be applied to quantitative planning of urban vegetation and regional eco-compensation mechanisms.

Observation of nocturnal low-level wind shear and particulate matter in urban Beijing using a Doppler wind lidar

临山城市夜间山风可影响污染物的分布,但夜间低层山风的演变及其对污染物分布的影响观测研究较少。本文通过325 m气象塔及一台测风激光雷达快速移动到四地的定点观测,获取了北京城区一次三维夜间山风及污染物分布特征,为城市测风提供了一种新方法。结果表明:相距20 km南、北城均有低层风向切变且间隔为1.5 h;城北低空急流的高度及风速均大于城东南;240 m和地面颗粒物的水平分布一致;PM2.5地面高值区的南移时间与北风急流到达时间一致,晚于地面风转向时间。

Evaluation and Evolution of MAX-DOAS-observed Vertical NO_(2) Profiles in Urban Beijing

Multiaxis differential absorption spectroscopy(MAX-DOAS)is a newly developed advanced vertical profile detection method,but the vertical nitrogen dioxide(NO_(2))profiles measured by MAX-DOAS have not yet been fully verified.In this study,we perform MAX-DOAS and tower gradient observations to simultaneously acquire tropospheric NO_(2)observations in the Beijing urban area from 1 April to 31 May 2019.The average values of the tropospheric NO_(2)vertical column densities measured by MAX-DOAS and the tropospheric monitoring instrument are 15.8×1015 and 12.4×1015 molecules cm−2,respectively,and the correlation coefficient R reaches 0.87.The MAX-DOAS measurements are highly consistent with the tower-based in situ measurements,and the correlation coefficients R from the ground to the upper air are 0.89(60 m),0.87(160 m),and 0.76(280 m).MAX-DOAS accurately measures the trend of NO_(2)vertical profile changes,although a large underestimation occurs by a factor of two.By analyzing the NO_(2)vertical profile,the NO_(2)concentration reveals an exponential decrease with height.The NO_(2)vertical profile also coincides with the evolution of the boundary layer height.The study shows that the NO_(2)over Beijing mainly originates from local sources and occurs in the boundary layer,and its vertical evolution pattern has an important guiding significance to better understand nitrate production and ozone pollution.

Responses of Soil Bacterial Diversity to Fertilization are Driven by Local Environmental Context Across China

Soil microbial diversity is extremely vulnerable to fertilization,which is one of the main anthropogenic activities associated with global changes.Yet we know little about how and why soil microbial diversity responds to fertilization across contrasting local ecological contexts.This knowledge is fundamental for predicting changes in soil microbial diversity in response to ongoing global changes.We analyzed soils from ten 20-year field fertilization(organic and/or inorganic)experiments across China and found that the national-scale responses of soil bacterial diversity to fertilization are dependent on ecological context.In acidic soils from regions with high precipitation and soil fertility,inorganic fertilization can result in further acidification,resulting in negative impacts on soil bacterial diversity.In comparison,organic fer-tilization causes a smaller disturbance to soil bacterial diversity.Despite the overall role of environmental contexts in driving soil microbial diversity,a small group of bacterial taxa were found to respond to fer-tilization in a consistent way across contrasting regions throughout China.Taxa such as Nitrosospira and Nitrososphaera,which benefit from nitrogen fertilizer addition,as well as Chitinophagaceae,Bacilli,and phototrophic bacteria,which respond positively to organic fertilization,could be used as bioindicators for soil fertility in response to fertilization at the national scale.Overall,our work provides new insights into the importance of local environmental context in determining the responses of soil microbial diver-sity to fertilization,and identifies regions with acidic soils wherein soil microbial diversity is more vul-nerable to fertilization at the national scale.

Impact of Climate Change on Urban Agglomerations in China’s Coastal Region

Climate change and urbanization issues are the two key factors that make humans liable to be affected by disasters, which are overlapped in urban agglomeration. The five big urban agglomerations of China with strong economic power are the important engines for national economic and social development. However, being in the sea-land mutual interaction belts with a vast hazard-bearing body, they are affected by sea-land compound disasters, and are liable to suffer heavy disaster losses with climate change. It is suggested that government departments concerned should fully recognize the impact of climate change on coastal urban agglomerations, propose strategies as soon as possible, and integrate the impact of climate change and adaptation countermeasures into the various kinds of social-economic development plans for coastal urban regions.

Climate Change, Air Quality and Urban Health: Evidence from Urban Air Quality Surveillance System in 161 Cities of China 2014

Air pollution has posed a serious public health issue in China. In the study, we aimed to examine the burden of air pollution and its association with climate factors and total mortality. City-level daily air quality index (AQI) data in 161 cities of China in 2014, and meteorological factors, socioeconomic status and total morality were obtained from China environmental, meteor-ology and healthcare agencies. Linear regression, spatial autocorrelation analysis and panel fixed models were applied in data analysis. Among 161 cities, monthly average AQI was significantly different by seasons and regions. The highest average AQI was in winter, and the lowest in summer. A significant clustering distribution of AQI by cities was observed, with the highest AQI in north China (22 cities, mean = 117.36). Among the 161 cities, 5 cities (3%) had AQI > 150 (e.g., moderate polluted reference value), and 50 cities (31.1%) had AQI between 100 and 150 (slightly polluted value). Daily heat index, precipitation and sunshine hours were negatively and significantly, but air pressure was positively correlated with AQI. Cities with higher AQI concentrations had higher total mortality than those with lower AQI. This AQI-mortality association remained significant after adjustment for socioeconomic status. In conclusion, the study highlights the burden and seasonal, regional and areas variations in air pollution across the nation. Air pollution is estimated to account for more than 4% of the urban health inequality in total mortality in China.

A New Interdisciplinary Science Plan for Urban Health and Wellbeing in an Age of Increasing Complexity

Cities of the future will need to cope with the triple challenges of urban growth,planetary boundaries leading to reduced energy and other resources,and rapid climate change.In response to the challenges of these complexities,urban growth and innovations in networked infrastructure development need to go hand-in-hand to transform urban systems and sustain the urban health advantage.In order to achieve this,knowledge and policy-making need to undergo processes of accelerated learning.The International Science Council’s global science programme“Urban Health and Wellbeing:A Systems Approach”has formulated goals to meet the urban health challenges of future cities.

Fe-N-C core-shell catalysts with single low-spin Fe(Ⅱ)-N_(4)species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells

Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.

从中国首台紫外-可见光高光谱卫星仪器反演得到的高空间分辨率臭氧廓线

Understanding the vertical distribution of ozone is crucial when assessing both its horizontal and vertical transport,as well as when analyzing the physical and chemical properties of the atmosphere.One of the most effective ways to obtain high spatial resolution ozone profiles is through satellite observations.The Environmental Trace Gases Monitoring Instrument(EMI)deployed on the Gaofen-5 satellite is the first Chinese ultraviolet-visiblehyperspectralspectrometer.However,retrieving ozone profiles using backscattered radiance values measured by the EMI is challenging due to unavailable measurement errors and a low signal-to-noise ratio.The algorithm developed for the Tropospheric Monitoring Instrument did not allow us to retrieve 87%of the EMI pixels.Therefore,we developed an algorithm specific to the characteristics of the EMI.The fitting residuals are smaller than 0.3%in most regions.The retrieved ozone profiles were in good agreement with ozonesonde data,with maximum mean biases of 20%at five latitude bands.By applying EMI averaging kemels to the ozonesonde profiles,the integrated stratospheric column ozone and tropospheric column ozone also showed excellent agreement with ozo-nesonde data.The lower layers(0-7.5 km)of the EMI ozone profiles reflected the seasonal variation in surface ozone derived from the China National Environmental Monitoring Center(CNEMC).However,the upper layers(9.7-16.7 km)of the ozone profiles show different trends,with the ozone peak occurring at an altitude of 9.7-16.7 km in March,2019.A stratospheric intrusion event in central China from August 11 to 15,2019,is captured using the EMI ozone profiles,potential vorticity data,and relative humidity data.The increase in the CNEMC ozone concentration showed that downward transport enhanced surface ozone pollution.

A commentary review on the use of normalized diff erence vegetation index(NDVI)in the era of popular remote sensing

The Normalized Diff erence Vegetation Index(NDVI),one of the earliest remote sensing analytical products used to simplify the complexities of multi-spectral imagery,is now the most popular index used for vegetation assessment.This popularity and widespread use relate to how an NDVI can be calculated with any multispectral sensor with a visible and a near-IR band.Increasingly low costs and weights of multispectral sensors mean they can be mounted on satellite,aerial,and increasingly—Unmanned Aerial Systems(UAS).While studies have found that the NDVI is effective for expressing vegetation status andquantified vegetation attributes,its widespread use and popularity,especially in UAS applications,carry inherent risks of misuse with end users who received little to no remote sensing education.This article summarizes the progress of NDVI acquisition,highlights the areas of NDVI application,and addresses the critical problems and considerations in using NDVI.Detailed discussion mainly covers three aspects:atmospheric eff ect,saturation phenomenon,and sensor factors.The use of NDVI can be highly eff ective as long as its limitations and capabilities are understood.This consideration is particularly important to the UAS user community.

Detection of Acid Rain Stress Effect on Plant Using Hyperspectral Data in Three Gorges Region,China

This paper aims to use hyperspectral data to detect the spectral change caused by acid stress to a native forest type in the Three Gorges region of China. For this purpose, a ground-based hyperspectral experiment was conducted at the Three Gorges region to detect acid deposition that caused Masson pine (Pinus massoniana) forest degra-dation. Continuum removal method was used to isolate wavebands more responsive to stress in wavelengths 450-750nm. The differences in chlorophyll concentrations and needle thickness caused by acidic stress are found to be explicable to the different spectral reflectance patterns in the visible and near-infrared wavelengths. Two new chlorotic indices were utilized to explain the stress-caused leaf chlorosis. The comparison of simulated vegetation indices and principal component analysis (PCA) results suggests that it would be possible to monitor acid rain stress effect on forest ecosystem from some wider spectral regions.

Investigating the Transport Mechanism of PM2.5 Pollution during January 2014 in Wuhan, Central China

Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different from other megacities, like Beijing. Both the growth rates and decline rates of PM2.5 concentrations in Wuhan were lower than those in Beijing, but the monthly PM2.5 value was approximately twice that in Beijing. Furthermore, the sharp increases of PM2.5 concentrations were often accompanied by strong winds. A high-precision modeling system with an online source-tagged method was established to explore the formation mechanism of five haze episodes. The long-range transport of the polluted air masses from the North China Plain (NCP) was the main factor leading to the sharp increases of PM2.5 concentrations in Wuhan, which contributed 53.4% of the monthly PM2.5 concentrations and 38.5% of polluted days. Furthermore, the change in meteorological conditions such as weakened winds and stable weather conditions led to the accumulation of air pollutants in Wuhan after the long-range transport. The contribution from Wuhan and surrounding cities to the PM2.5 concentrations was determined to be 67.4% during this period. Under the complex regional transport of pollutants from surrounding cities, the NCP, East China, and South China, the five episodes resulted in 30 haze days in Wuhan. The findings reveal important roles played by transregional and intercity transport in haze formation in Wuhan.

First record of Biecheleria cincta (Dinophyceae) from Chinese coasts, with morphological and molecular characterization of the strains

The presence of Biecheleria cincta (=Woloszynskia cincta) in the Chinese coasts is reported for the first time. In scanning electron microscope, three to five series of vesicles and an elongated apical vesicle (EAV) were visible in the epicone, and both the hypocone and the cingulum had three series of vesicles each. Thin sections revealed that B. cincta possesses stalked pyrenoids and an unusual eyespot consisting of a stack of cisternae with brick-like materials (type E), thus supporting its transfer from Woloszynskia to Biecheleria. Spiny cysts formed spontaneously in culture, with an encystment rate of around 20%. Both large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer region (ITS) sequences in 12 strains from the Chinese coasts were determined. Phylogenetic analyses based on LSU rDNA and ITS sequences using Bayesian inference and maximum likelihood revealed two distinct ribotypes (referred to as ribotype A and B) in B. cincta. ITS region pairwise distances within B. cincta ranged from 0.024 to 0.072, suggesting the existence of a complex of cryptic species.

Specific Recognition of Breast Cancer Cells In Vitro Using Near Infrared-Emitting Long-Persistence Luminescent Zn_3Ga_2Ge_2O_(10):Cr^(3+)Nanoprobes

In this paper, near-infrared emitting long-persistence luminescent Zn3Ga2Ge2O10:Cr3?(ZGG) nanoparticles with diameters of 30–100 nm and bright luminescence were prepared by a sol–gel synthesis method. After the surface amination, the nanoparticles were further bioconjugated with breast cancer-specific monoclonal antibody(anti-Ep CAM) to form ZGG-Ep CAM nanoprobes which can specifically target breast cancer cell lines(MCF7) in vitro. The results of in vitro images show that the luminescence signals from the cells treated with ZGG-Ep CAM nanoprobes are stronger than those from cells treated with ZGG-unconjugated antibody, indicating that the prepared ZGG-Ep CAM nanoprobes possessed excellent specific recognition capability. Furthermore, due to their long afterglow properties, the imaging could persist more than 1 h. Therefore, these nanoprobes could not only provide a high specificity detection method for cancer cells but also realize the long-time monitoring. Developed near-infrared emitting long-persistence luminescent nanoprobes will be expected to find new perspectives for cell therapy research and diagnosis applications.

Stable isotope geochemical characteristics of dissolved inorganic carbon in the Jiulong River Estuary, Fujian Province, China

The isotopic composition of dissolved inorganic carbon(DIC) in estuarine environments has been studied for its significant role in determining the isotopic composition of inorganic/organic matter and its applications to the study of various natural processes. In this paper, based on the stable isotope geochemical characteristics of dissolved inorganic carbon in the Jiulong River Estuary, the following conclusions are drawn:(1) δ13CDIC values are mainly controlled by the mixing ratio of fresh water and sea water;(2) δ13Cphytoplankton values are linearly related to the δ13CDIC values;(3) δ13CPOM values for the Jiulong River Estuary are affected by anthropogenic pollution significantly; and(4) the comprehensive analysis of δ13Cphytoplankton, δ13CPOM and δ13CDIC shows that along with increasing salinity, the proportion of POM derived from the degradation of phytoplanktons gradually increases.

Seasonal comparison of bacterial communities in rhizosphere of alpine cushion plants in the Himalayan Hengduan Mountains

Positive associations between alpine cushion plants and other species have been extensively studied.However,almost all studies have focused on the associations between macrofauna.Studies that have investigated positive associations between alpine cushion plants and rhizospheric microbes have been limited to the vegetation growing season.Here,we asked whether the positive effects that alpine cushion plants confer on rhizospheric microbe communities vary with seasons.We assessed seasonal variations in the bacterial diversity and composition in rhizosphere of two alpine cushion plants and surrounding bare ground by employing a high throughput sequencing method targeting the V3 region of bacterial 16 S rRNA genes.Soil properties of the rhizosphere and the bare ground were also examined.We found that cushion rhizospheres harbored significantly more C,N,S,ammonia nitrogen,and soil moisture than the bare ground.Soil properties in cushion rhizospheres were not notably different,except for soil pH.Bacterial diversities within the same microhabitats did not vary significantly with seasons.We concluded that alpine cushion plants had positive effects on the rhizospheric bacterial communities,even though the strength of the effect varied in different cushion species.Cushion species and the soil sulfur content were probably the major factors driving the spatial distribution and structure of soil bacterial communities in the alpine communities dominated by cushion plants.