Cassini Growth of Population Between Two Metropolitan Cities——A Case Study of Beijing-Tianjin Region,China

The existing models of population distribution often focus on the region with a single city or even multiple centers, and lack the detailed explorations of the common and special type of urbanization areas with two centers. Taking Beijing-Tianjin region of China, which is a distinct dual-nuclei metropolitan area in the world, as an example and choosing Landsat-5 TM image in 2005, population, etc. as the data, this paper devotes to comprehending and illustrating a model of Cassini growth of population between the two metropolitan cities through the research of spatial population distribution pattern, aided with RS and GIS techniques. Main technical processes include Kriging interpolation of the population data and character simulation of the Cassini ovals. According to the calculation of a/b, a key characteristic index of Cassini growth model, the spatial structures of population distribution were given. When a/b〈 1, it is a curve with two separated loops with a population density more than 3000 persons/km^2. When a/b=1, it is a lemniscate curve with a population density about 3000 persons/km^2. When 1〈a/b〈 √2, it is a dog-bone shaped concave curve with a population density between 500-3000 persons/km^2. When a/b= √2, it is an oblate curve with a population density about 500 persons/km^2. When a/b〉 √2, there is an oval-shaped convex curve with a population density less than 500 persons/km^2. The results show that owing to the combined action and influence of the regional dual-nuclei, the population distribution of Beijing-Tianjin region is in accord with Cassini model significantly. Therefore, there is Cassini growth of population between the two metropolitan cities in Beijing-Tianjin region. In addition, the process of Cassini growth has extraordinarily instructive significance for judging the development stages of the dual-nuclei metropolitan areas.

Useful Precursor Weather Conditions for Hail-Event Forecasting in the Beijing-Tianjin Region

Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hail based on 30 previous hail events were derived.It was found that the high-level trough and low-level cold front over the Mongolian region,the accumulated convective available potential energy,the decrease of the height of the 0℃-isotherm in the morning,and the persistence and intensification of these factors from morning to afternoon are valuable clues for forecasting the occurrence of hail events over the BT region.

Seasonal Characteristics of Forecasting Uncertainties in Surface PM_(2.5)Concentration Associated with Forecast Lead Time over the Beijing-Tianjin-Hebei Region

Forecasting uncertainties among meteorological fields have long been recognized as the main limitation on the accuracy and predictability of air quality forecasts.However,the particular impact of meteorological forecasting uncertainties on air quality forecasts specific to different seasons is still not well known.In this study,a series of forecasts with different forecast lead times for January,April,July,and October of 2018 are conducted over the Beijing-Tianjin-Hebei(BTH)region and the impacts of meteorological forecasting uncertainties on surface PM_(2.5)concentration forecasts with each lead time are investigated.With increased lead time,the forecasted PM_(2.5)concentrations significantly change and demonstrate obvious seasonal variations.In general,the forecasting uncertainties in monthly mean surface PM_(2.5)concentrations in the BTH region due to lead time are the largest(80%)in spring,followed by autumn(~50%),summer(~40%),and winter(20%).In winter,the forecasting uncertainties in total surface PM_(2.5)mass due to lead time are mainly due to the uncertainties in PBL heights and hence the PBL mixing of anthropogenic primary particles.In spring,the forecasting uncertainties are mainly from the impacts of lead time on lower-tropospheric northwesterly winds,thereby further enhancing the condensation production of anthropogenic secondary particles by the long-range transport of natural dust.In summer,the forecasting uncertainties result mainly from the decrease in dry and wet deposition rates,which are associated with the reduction of near-surface wind speed and precipitation rate.In autumn,the forecasting uncertainties arise mainly from the change in the transport of remote natural dust and anthropogenic particles,which is associated with changes in the large-scale circulation.

Did Ecological Engineering Projects Have a Significant Effect on Large-scale Vegetation Restoration in Beijing-Tianjin Sand Source Region, China？ A Remote Sensing Approach

Aiming for the restoration of degraded ecosystems, many ecological engineering projects have been implemented around the world. This study investigates the ecological engineering project effectiveness on vegetation restoration in the Beijing-Tianjin Sand Source Region(BTSSR) from 2000 to 2010 based on the rain use efficiency(RUE) trend in relation to the land cover. More than half of the BTSSR experienced a vegetation productivity increase from 2000 to 2010, with the increasing intensity being sensitive to the indicators chosen. A clear tendency towards smaller increasing areas was shown when using the net primary productivity(NPP, 51.30%) instead of the accumulated normalized difference vegetation index(59.30%). The short-term variation in the precipitation and intra-seasonal precipitation distribution had a great impact on the remote sensing-based vegetation productivity. However, the residual trends method(RESTREND) effectively eliminated this correlation, while incorporating the variance and skewness of the precipitation distribution increased the models′ ability to explain the vegetation productivity variation. The RUE combined with land cover dynamics was valid for the effectiveness assessment of the ecological engineering projects on vegetation restoration. Particularly, the result based on growing season accumulated normalized difference vegetation index(ΣNDVI) residuals was the most effective, showing that 47.39% of the BTSSR experienced vegetation restoration from 2000 to 2010. The effectiveness of the ecological engineering projects differed for each subarea and was proportional to the strength of ecological engineering. The water erosion region dominated by woodland showed the best restoration, followed by the wind-water erosion crisscross regions, while the wind erosion regions dominated by grassland showed the worst effect. Seriously degraded regions still cover more area in the BTSSR than restored regions. Therefore, more future effort should be put in restoring degraded land.

Empirical Study on Effect of Industrial Structure Change on Regional Economic Growth of Beijing-Tianjin-Hebei Metropolitan Region

Based on the data of gross domestic product(GDP),industrial added value and the proportion of industrial employees from 2000 to 2008,this paper studies the effect of industrial structure change on the regional economic growth of Beijing-Tianjin-Hebei Metropolitan Region in China using the shift-share method.The results show that:1) In the 21st century,the industrial output of three industries,namely,primary,secondary,and tertiary,and the GDP grew rapidly in the study period.The tertiary industry grew the fastest;it had the largest contribution to the GDP and mean-while had become the most competitive industry in the metropolitan region.2) The development of cities within the region was not balanced.Firstly,compared with Tianjin,Beijing,as one of the two core cities,was more rational in the industrial structure.Secondly,the surrounding eight cities,which are Shijiazhuang,Qinhuangdao,Tangshan,Langfang,Baoding,Cangzhou,Zhangjiakou,and Chengde,were all uncompetitive than the two core cities.3) There was a great industrial gradient in the region(especially between the two core cities and the cities of Tangshan,Baoding,Zhangjia-kou,Chengde,Cangzhou,and Langfang).As a result,it is foreseeable that the industry transfer in the Bei-jing-Tianjin-Hebei Metropolitan Region will be one of the trends in regional development,and the industry transfer is inevitably to promote the regional integration.

Decomposition of factors influencing carbon emissions in the region of Beijing-Tianjin-Hebei,based on the perspective of terminal energy consumption

In order to analyze the factors influencing carbon emissions in the region of Beijing-Tianjin-Hebei and to explore the pathways to developing a low-carbon economy,this paper begins with the terminal energy consumption of three industries and residential consumption,and constructs an identical equation which is composed of population size,level of economic development,energy intensity,the proportion of energy consumption,energy structure,and the coefficient of carbon emissions.Based on the data of terminal energy consumption during 2000-2012,various factors are analyzed and their contribution is measured by Logarithmic Mean Divisia Index(LMDI).The results show that the levels of population and economy have a positive driving effect while energy intensity,energy structure,and carbon intensity have a negative driving effect;the proportion of energy consumption had a negative driving effect prior to 2006,then changed to positive.Among suggestions for a low-carbon economy are controlling population size,improving the quality of economic development,supporting research into new energy technology,accelerating regional integration and optimizing industrial structure,and enhancing environmental protection and spreading the concept of a low-carbon economy.

A Numerical Study of the Urban Intensity Effect on Fog Evolution in the Beijing-Tianjin-Hebei Region

The influence of urban intensity on fog evolution in the Beijing-Tianjin-Hebei (BTH) region (China) is investigated numerically with the the Weather Research and Forecasting (WRF) model coupled with the urban canopy parameterization-building energy model (UCP- BEM) urban physics scheme. The experiments were designed with a focus on the influence of different urban intensities, which are represented by a different fractional coverage of natural land, buildings, and energy consumption inside buildings in an urban environment. The results of this study indicate that urban areas notably influence fog evolution when natural land is reduced to a small fraction (e.g., less than 10%). Developed land changes fog evolution through urban effects. Higher urban intensity (HUI) generally results in warmer temperatures and lower wind speeds throughout the day, while inhibiting morning specific humidity loss and afternoon specific humidity gain because of the HUI effect on surface heat flux, surface roughness, and surface moisture flux. HUI leads to later and weaker liquid water content formation, with a higher liquid water content base, primarily due to its effect on near surface temperatures. This finding implies that HUI may inhibit the conditions for fog formation. In addition, urban areas with equal natural and developed land coverage seem to greatly enhance the upward surface moisture flux, which is attributed to the combination of a relatively large potential evaporation on developed land and an ample moisture supply from natural land. As a result, the specific humidity increases in the afternoon.

Assessing adaptability of the water resource system to social-ecological systems in the Beijing-Tianjin-Hebei region:Based on the DPSIR-TOPSIS framework

To optimize the overall layout of water resource allocation in the Beijing-Tianjin-Hebei region,the adaptabil‐ity of the water resource system to the regional social-ecological systems has to be enhanced.Based on the driver-pressure-state-impact-response(DPSIR)framework,this study constructs an evaluation index system to analyze the adaptability mechanisms of Beijing-Tianjin-Hebei’s water resource system according to the three major constituent social-ecological systems(i.e.,economic,social,and ecological systems).Moreover,it adopts the technique of order preference similarity to the ideal solution(TOPSIS)to comprehensively evaluate the adaptability of Beijing-Tianjin-Hebei’s water resource system based on three constituent social-ecological systems(i.e.,economic,social,and ecological systems)and identifies the spatiotemporal differentiation char‐acteristics of the region.Our results showed that,①from 2000 to 2020,the adaptability of Beijing-Tianjin Hebei’s water resource system,as a whole,significantly improved.In terms of stages,from 2000 to 2007,the adaptability of the water resource social system was significantly higher than that of economic and ecological systems in the region.From 2008 to 2015,by accelerating the transformation and upgrading of industrial structures,improving the efficiency of economic water utilization,and strengthening the governance of the water ecosystem,the adaptability of water resource economic and ecological systems rapidly improved;how‐ever,that of the water resource ecological system was still the lowest.Additionally,the adaptability of the wa‐ter resource economic system exceeded that of the social system.From 2016 to 2020,the gap in adaptability of the water resource system to all three major constituent systems gradually narrowed.By 2020,the three sys‐tems entered a relatively balanced development stage,with the adaptability of the entire water resource system and the three major constituent systems maintaining a high level.②The economic system was significantly af‐fected by per capita GDP,per capita water resources,and the efficiency of economic water utilization.Addition‐ally,the social system was significantly affected by water consumption per unit of irrigation area.Meanwhile,the ecological system was significantly influenced by precipitation,water pollution discharge performance indi‐cators,and the structure optimization indicators of water supply.According to the evaluation results,we pro‐pose countermeasures and provide recommendations to optimize the overall layout of water resource alloca‐tion and promote the coordinated management of water resources in the Beijing-Tianjin-Hebei region.

Spatial Variability of PM_(2.5) Pollution in Imbalanced Natural and Socioeconomic Processes: Evidence from the Beijing-Tianjin-Hebei Region of China

Accurately identifying and quantifying the factors influencing PM_(2.5) pollution is of great significance for the prevention and control of pollution. However, the redundancy among potential factors of PM_(2.5) may be overlooked. Meanwhile, the inconsistent spatial distribution of the natural and socioeconomic conditions brings unique implications for the cities within a region, which may lead to an uncertain understanding of the relationship between pollution and environmental factors. This study focused on the Beijing-TianjinHebei(BTH) Region, China, which presents complex and varied background conditions. Potential impact factors on PM_(2.5) were firstly screened by combining systematic cluster analysis with a random forest recursive feature elimination algorithm. Then, the representative multi-factor responsible for PM_(2.5) pollution in the region during the key period of 2014–2018(when the strict national air pollution control policy was implemented). The results showed that the key driving factors of PM_(2.5) pollution in the BTH cities are different, indicating that the uniqueness of a city will have an impact on the leading causes of pollution. Further discussion shows that air control policy provides an effective way to improve air quality. This study aims to deepen the understanding of the risk drivers of air pollution within the BTH Region. In the future, it is recommended that more attention should be paid to the specific differences between the cities when formulating PM_(2.5) concentration control measures.

The status quo and prospect of geothermal resources exploration and development in Beijing-Tianjin-Hebei region in China

The Beijing-Tianjin-Hebei region boasts rich geothermal resources and new achievements have been made in the exploration and development of geothermal resources in this region based on previous regional investigation.In detail,geothermal reservoirs of Gaoyuzhuang Formation of Jixian System and Changcheng System in Xiongan New Area have been recently discovered,opening up the second space of geothermal resources;the calculation method of the recoverable resources of geothermal fluid with reinjection being considered has been improved in Beijing-Tianjin-Hebei region,and uniform comprehensive assessment of shallow geothermal energy,hydrothermal geothermal resources,and hot dry rocks(HDR)geothermal resources in the whole Beijing-Tianjin-Shijiazhuang region has been completed.The scientific research base for cascade development and utilization of geothermal resources in Beijing-Tianjin-Hebei region has applied hydraulic fracturing technology to the geothermal reservoirs in Gaoyuzhuang Formation.As a result,the production capacity doubled and two-stage cascade utilization composed of geothermal power generation and geothermal heating were realized,with the first-phase installed capacity of 280 kW and the geothermal heating is 30000 m2.In this way,a model of the exploration,development,and utilization of geothermal resources formed.Large-scale utilization has become the future trend of geothermal resource development in Beijing-Tianjin-Hebei region,and great efforts shall be made to achieve breakthroughs in reinjection technology,geothermal reservoir reconstruction technology,thermoelectric technology and underground heat exchange technology.

Spheres of Urban Influence and Factors in Beijing-Tianjin-Hebei Metropolitan Region Based on Viewpoint of Administrative Division Adjustment

The coordinated development of Beijing, Tianjin and Hebei has been elevated as China's important strategy. And, the priority in considering how to bring the maximum effect of their coordinated development into play is to delineate the spheres of urban influence with regard to the cities in the Beijing-Tianjin-Hebei Metropolitan Region. By building an evaluation index system of urban comprehensive strength, this paper applies the principal component analysis method to determine centrality strength of the cities, and the breakpoint theory and weighted Voronoi diagram to identify the spheres of urban influence in all central cities of the region. Results show that 13 central cities within the region greatly differ in strength, which can be classified into four tiers and that the spheres of urban influence do not have a high goodness of fit with administrative jurisdiction scope. Cities like Beijing, Tianjin, Shijiazhuang and Handan have larger spheres of urban, spheres of urban influence in Tangshan and Qinhuangdao are basically consistent with their administrative jurisdiction scopes, and seven cities including Langfang and Baoding have smaller spheres of urban influence. So according to these cities' comprehensive strength and spheres of influence, the region can be divided into five plates: Beijing, Tianjin, Shijiazhuang, Tangshan and Handan. The major influence factors for inconsistency between spheres of urban influence and spheres of jurisdiction include difference in urban administrative ranking, small number of central cities with weak strength, discrepancy in the number of counties under jurisdiction, unreasonable spheres of jurisdiction and diversity in topographical conditions. In order to solve the imbalance in the spheres of urban influence and those of jurisdiction and better facilitate the coordinated development of the region, it is advised to adjust administrative areas so as to obtain more optimized urban spatial layout and more reasonable urban scale hierarchy system.

Response of Vegetation Cover Change to Drought at Different Time-scales in the Beijing-Tianjin Sandstorm Source Region,China

Dominated by an arid and semiarid continental climate,the Beijing-Tianjin Sandstorm Source Region(BTSSR)is a typical ecologically fragile region with frequently occurring droughts.To provide information for regional vegetation protection and drought prevention,we assessed the relations between vegetation cover change(measured by the Normalized Difference Vegetation Index,NDVI)and the Standardized Precipitation Evapotranspiration Index(SPEI)at different time-scales,in different growth stages,in different subregions and for different vegetation types based on the Pearson's correlation coefficient in the BTSSR from 2000 to 2017.Results showed that 88.19%of the vegetated areas experienced increased NDVI in the growing season;48.3%of the vegetated areas experi-enced significantly increased NDVI(P<0.05)and were mainly in the south of the BTSSR.During the growing season,a wetter climate contributed to the increased vegetation cover from 2000 to 2017,and NDVI anomalies were closely related to SPEI.The maximum correlation coefficient in the growing season(Rmax)was significantly positive(P<0.05)in 97.84%of the total vegetated areas.In the vegetated areas with significantly positive Rmax,pixels with short time-scales(1-3 mon)accounted for the largest proportion(33.9%).The sensitivity of vegetation to the impact of drought rose first and then decreased in the growing season,with a peak in July.Compared with two subregions in the south,subregions in the north of the BTSSR were more sensitive to the impacts of drought variations,especially in the Xilingol Plateau and Wuzhumuqin Basin.All four major vegetation types were sensitive to the effects of drought variations,especially grasslands.The time-scales of the most impacting droughts varied with growth stages,regions,and vegetation types.These results can help us understand the relations between vegetation and droughts,which are important for ecological restoration and drought prevention.

Measuring Social Vulnerability to Natural Hazards in Beijing-Tianjin-Hebei Region,China

Social vulnerability in this study represents the differences between the capacity to cope with natural hazards and disaster losses suffered within and between places.The assessment of social vulnerability has been recognized as a critical step in understanding natural hazard risks and enhancing effective response capabilities.This article presents an initial study of the social vulnerability of the Beijing-Tianjin-Hebei(B-T-H) Region in China.The goal is to replicate and test the applicability of the United States Social Vulnerability Index(So VI) method in a Chinese cultural context.Thirty-nine variables adapted from the So VI were collected in relation to two aspects:socioeconomic vulnerability and built environment vulnerability.Using factor analysis,seven factors were extracted from the variable set:the structure of social development,the level of economic and government financial strength,social justice and poverty,family structure,the intensity of space development,the status of residential housing and transportation,and building structure.Factor scores were summed to get the final So VI scores and the most and least vulnerable units were identified and mapped.The highest social vulnerability is concentrated in the northwest of the study area.The least socially vulnerable areas are mainly distributed in the Beijing,Tianjin and Shijiazhuang core urban peripheral and central city areas of the prefecture-level cities.The results show that this method is a useful tool for revealing places that have a high level of vulnerability,in other words,areas which are more likely to face significant challenges in coping with a large-scale event.These findings could provide a scientific basis for policy making and the implementation of disaster prevention and mitigation in China.

CO2 emission driving forces and corresponding mitigation strategies under low-carbon economy mode:evidence from China's Beijing-Tianjin-Hebei region

On account of the background of China's "new normal" characterized by slower economic growth, this paper analyses the low-carbon economy status quo in the Beijing-Tianjin-Hebei region and empirically investigates the relationship between carbon dioxide(CO_2) emissions and its various factors for China's Beijing-Tianjin-Hebei region using panel data econometric technique. We find evidence of existence of Environmental Kuznets Curve. Results also show that economic scale, industrial structure, and urbanization rate are crucial factors to promote CO_2emissions. However, technological progress, especially the domestic independent research and development, plays a key role in C0_2 emissions abatement. Next, we further analyze the correlation between each subregion and various factors according to Grey Relation Analysis. Thereby,our findings provide important implications for policymakers in air pollution control and C0_2 emissions reduction for this region.

Ecological compensation mechanism for Beijing-Tianjin-Hebei region based on footprint balance and footprint deficit

Construction of the ecological compensation mechanism is an important approach to put the“Beijing-Tianjin-Hebei Coordinated Development Plan”into practice and improve the ecological environment of the Beijing-Tianjin-Hebei region.This paper constructs an ecological compensation mechanism for the Beijing-Tianjin-Hebei region based on the footprint balance and footprint deficit after clarifying ecological governance objectives.First,this paper proposes to establish a uniform,hierarchical and classified supply mechanism of ecosystem services according to the classification of land resources,water resources and forest resources for the Beijing-Tianjin-Hebei region.Then,the“Authority with Corresponding Responsibility”for the supply of ecosystem services in the Beijing-Tianjin-Hebei region can be realized through a footprint balance and footprint deficit indicator circulation mechanism.Finally,the scientific and rational ecological compensation standard can be guaranteed through establishing the integrated governance mechanism for ecological compensation in the Beijing-Tianjin-Hebei region and improving the“ecological compensation standard”.The results of this paper can provide sound theoretical support for effectively promoting the improvement of ecosystem services and human well-being in the Beijing-Tianjin-Hebei region.

Does digitalization mitigate regional inequalities?Evidence from China

Regional inequality significantly influences sustainable development and human well-being.In China,there exists pronounced regional disparities in economic and digital advancements;however,scant research delves into the interplay between them.By analyzing the economic development and digitalization gaps at regional and city levels in China,extending the original Cobb-Douglas production function,this study aims to evaluate the impact of digitalization on China's regional inequality using seemingly unrelated regression.The results indicate a greater emphasis on digital inequality compared to economic disparity,with variable coefficients of 0.59 for GDP per capita and 0.92 for the digitalization index over the past four years.However,GDP per capita demonstrates higher spatial concentration than digitalization.Notably,both disparities have shown a gradual reduction in recent years.The southeastern region of the Hu Huanyong Line exhibits superior levels and rates of economic and digital advancement in contrast to the northwestern region.While digitalization propels economic growth,it yields a nuanced impact on achieving balanced regional development,encompassing both positive and negative facets.Our study highlights that the marginal utility of advancing digitalization is more pronounced in less developed regions,but only if the government invests in the digital infrastructure and education in these areas.This study's methodology can be utilized for subsequent research,and our findings hold the potential to the government's regional investment and policy-making.

A Brief Analysis of the Causes and Countermeasures of Fog-Haze in Beijing-Tianjin-Hebei Region

Since China broke the blockade and opened the country to the outside world, many township enterprises develop quickly. Together with the pollution caused by China’s coal-burning as the main source of national energy, the pollution caused by small and medium-sized enterprises in towns and villages due to their small investment, low technology level and weak environmental awareness, and the pollution caused by a sharp increase in motor vehicle emissions lead to the fact that fog-haze has been rampant in China’s cities and urban agglomerations for nearly two decades, especially in the Beijing-Tianjin-Hebei region. This paper sorted out the current situation of fog-haze and analyzed the causes of fog-haze from the two aspects of natural and man-made causes, discussed the harms of fog-haze to human body, environment and life, and put forward the concrete measures to solve the fog-haze problem.

Construction and Application of a Regional Kilometer-Scale Carbon Source and Sink Assimilation Inversion System(CCMVS-R)

CO_(2)is one of the most important greenhouse gases(GHGs)in the earth’s atmosphere.Since the industrial era,anthropogenic activities have emitted excessive quantities of GHGs into the atmosphere,resulting in climate warming since the 1950s and leading to an increased frequency of extreme weather and climate events.In 2020,China committed to striving for carbon neutrality by 2060.This commitment and China’s consequent actions will result in significant changes in global and regional anthropogenic carbon emissions and therefore require timely,comprehensive,and objective monitoring and verification support(MVS)systems.The MVS approach relies on the top-down assimilation and inversion of atmospheric CO_(2)concentrations,as recommended by the Intergovernmental Panel on Climate Change(IPCC)Inventory Guidelines in 2019.However,the regional high-resolution assimilation and inversion method is still in its initial stage of development.Here,we have constructed an inverse system for carbon sources and sinks at the kilometer level by coupling proper orthogonal decomposition(POD)with four-dimensional variational(4DVar)data assimilation based on the weather research and forecasting-greenhouse gas(WRF-GHG)model.Our China Carbon Monito ring and Verification Support at the Regional level(CCMVS-R)system can continuously assimilate information on atmospheric CO_(2)and other related information and realize the inversion of regional and local anthropogenic carbon emissions and natural terrestrial ecosystem carbon exchange.Atmospheric CO_(2)data were collected from six ground-based monito ring sites in Shanxi Province,China to verify the inversion effect of regio nal anthropogenic carbon emissions by setting ideal and real experiments using a two-layer nesting method(at 27 and 9 km).The uncertainty of the simulated atmospheric CO_(2)decreased significantly,with a root-mean-square error of CO_(2)concentration values between the ideal value and the simulated after assimilation was close to 0.The total anthropogenic carbon emissions in Shanxi Province in 2019 from the assimilated inversions were approximately 28.6%(17%-38%)higher than the mean of five emission inventories using the bottomup method,showing that the top-down CCMVS-R system can obtain more comprehensive information on anthropogenic carbon emissions.

A STUDY ON ENVIRONMENTAL EVOLUTION OF BEIJING-TIANJIN-TANGSHAN REGION FROM JIN DYNASTY TO THE REPUBLIC OF CHINA (A.D. 1153-1949)

Studies of the law and characteristics of population and land-use development of the Bejing-Tianjin-Tangshen region from 1153-1949 indicated that the land development process in the region is closely related with population change of the corresponding period In Jin Dynasty, population increased rapidly, in Yuan and Ming dynasties, population increased with a sustainability while from Qing Dynasty to the founding of the Republic, population increased substatially.Wasteland reclamation and cereals cultivation by garrison and farmers appeared in Jin Dyasty and reached climax in Ming Dynasty. Correlation analysis of poulation increase and cultivated area showed that they follow a linear equation which means that population increase and cultivated area expansion were at a similar rate.

A core-satellite self-assembled SERS aptasensor containing a“biological-silent region”Raman tag for the accurate and ultrasensitive detection of histamine

Herein,a novel interference-free surface-enhanced Raman spectroscopy(SERS)strategy based on magnetic nanoparticles(MNPs)and aptamer-driven assemblies was proposed for the ultrasensitive detection of histamine.A core-satellite SERS aptasensor was constructed by combining aptamer-decorated Fe_(3)O_(4)@Au MNPs(as the recognize probe for histamine)and complementary DNA-modified silver nanoparticles carrying 4-mercaptobenzonitrile(4-MBN)(Ag@4-MBN@Ag-c-DNA)as the SERS signal probe for the indirect detection of histamine.Under an applied magnetic field in the absence of histamine,the assembly gave an intense Raman signal at“Raman biological-silent”region due to 4-MBN.In the presence of histamine,the Ag@4-MBN@Ag-c-DNA SERS-tag was released from the Fe_(3)O_(4)@Au MNPs,thus decreasing the SERS signal.Under optimal conditions,an ultra-low limit of detection of 0.65×10^(-3)ng/mL and a linear range 10^(-2)-10^5 ng/mL on the SERS aptasensor were obtained.The histamine content in four food samples were analyzed using the SERS aptasensor,with the results consistent with those determined by high performance liquid chromatography.The present work highlights the merits of indirect strategies for the ultrasensitive and highly selective SERS detection of small biological molecules in complex matrices.