Search

Night-time light data (NTL) have been extensively utilized to map urban fringe areas, but to date, there has not been a comprehensive evaluation of the existing spatial clustering methods for delineating the urban fringe using different types of night-time light data. Therefore, we first selected three popular sources of night-time light data (i.e., NPP/VIIRS, Luojia 1-01, and NASA's Black Marble) to identify the urban fringe. The recognition of spatial mutations across the urban–rural gradient was conducted based on changes in night light intensity using a spatial continuous wavelet transform model. Then, we employed three representative dual spatial clustering approaches (i.e., MK-Means, DBSC, and DSC) for extracting urban fringe areas using different NTL. By using dual spatial clustering, the spatial patterns of the mutation points were effectively transformed into homogeneous spatially adjacent clusters, enabling the measurement of similarity between mutation points. Taking Nanjing city, one of China's megacities, as the study area, we found that (1) Compared with the fragmented and concentrated results obtained from the Luojia 1-01, NASA's Black Marble and NPP/VIIRS data can effectively capture the abrupt change of urban fringes with NTL variations; (2) DSC provided a reliable approach for accurately extracting urban fringe areas using NASA's Black Marble data. [ABSTRACT FROM AUTHOR]

In this study, the water-soluble inorganic ions (WSIIs) composition of fine particulate matter (PM2.5) was measured in the northern Nanjing city from 2015 to 2021. NH4+, NO3− and SO42− concentrations dominated in total WSIIs (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42−), accounting for 87.8%. The nitrate with highest average concentration among all ions was 11.0 μg·m−3. Total WSIIs concentrations were higher in winter and lower in summer, with the highest levels in December (45.6 μg·m−3) and the lowest levels in August (15.1 μg·m−3). NO3−/SO42− was higher than 1, indicating the important contribution of mobile sources. The aerosols exhibited a weak acidic by the molar ratio of water-soluble anions and cations. Positive matrix factorization (PMF) analysis results showed that secondary nitrate and sulfate were the major pollution sources in December 2016 and 2020. The contribution of secondary nitrate in 2020 increased by 47.6% compared to 2016, while that of secondary sulfate decreased by 42.4%. The potential source contribution results demonstrated that for secondary aerosol concentrations, the contribution of regional transport from north of Anhui increased, while the contribution of local emissions decreased. The results from this study could contribute to the better prevention and control of regional air pollution in the future. [ABSTRACT FROM AUTHOR]

Objectives: Based on taxi movement trajectories, urban traffic operating conditions can be analyzed. At present, the relevant research mainly focuses on the investigation of traffic origin and destination points and the extraction of traffic hotspots, but seldom analyzes the interaction between traffic hotspots. We focus on exploring the temporal and spatial patterns of urban traffic hotspots, with the purpose of providing a scientific basis for traffic management departments for traffic management in different periods and sections.Methods: We take the main urban city of Nanjing City as the research area, and use taxi GPS data in 2015, 2016, and 2017 for experiments. Firstly, the effective trajectory flow is extracted from the taxi GPS data through the local anomaly test method. Secondly, based on the GeoJSON geocoding to realize map matching, the Pathlet method is used to process the trajectory flow into a sequence which can be optimally solved by dynamic programming. Finally, based on the standard for evaluation of urban traffic operation status, the macroscopic fundamental diagram model is constructed according to the relationship be‑ tween traffic flow, speed and density in the road network, and the evaluation index is established by combining travel time ratio and the delay time ratio.Results: (1) Judging from the average of the traffic operation indicators, the main urban area of Nanjing is the most congested in the morning and evening rush hours, and the traffic is smooth in the early morning hours, and the traffic hotspots are more active on working days than on rest days. (2) Judging from the traffic operation indicators of the nine different nodes, the traffic congestion near the parking lot and office building nodes is relatively increased on weekdays, and the traffic congestion near the nodes of shopping malls and residential quarters is relatively increased on the rest days.(3) Judging from the perspective of spatial distribution of traffic hotspots in five representative periods, traffic hotspots mostly appear near intersections and ramps, and there are more interactions between main roads and express roads, but between townships and village roads and county roads. There is less interaction. (4) Judging from the perspective of the temporal and spatial patterns of traffic hotspots near the school during the morning rush hour, the temporal and spatial interaction characteristics of traffic hotspots are significant in areas with high node coverage, while the spatial distribution characteristics of traffic hotspots change unclearly with time in areas with low node coverage.Conclusions: Urban traffic hotspots show significant differences in time and space distribution characteristics, and their spatiotemporal interactions be‑ come stronger with time and space aggregation, which has a significant positive correlation. [ABSTRACT FROM AUTHOR]

Agriculture has great significance for the national food, resource, and ecological security, closely relating to the life stability and health of every resident. The cultivated land is constantly occupied by urban construction as the urbanization rapidly increases. The transfer of a large number of rural labor force and the change of food consumption structure have caused great challenge on the production and supply of vegetable food in China. The former Ministry of Agriculture has launched the Vegetable Basket Project in 1988, to solve the tight supply of agricultural and sideline products. A Vegetable Basket Project planning aims to transform and expand the vegetable greenhouse base, with emphasis on strong resistance to natural disasters, stable and high yield, further to realize the balance of seasonal production and perennial consumption of vegetables. In remote sensing interpretation of Nanjing City from 1995 to 2017, the cultivated farmlands were retreating from the urban areas, and the vegetable producing areas were shifting from the central to the outer suburbs, while the greenhouse areas were ever-increasing, as the main source of urban construction and expansion. It is necessary to evaluate the Vegetable Basket Policy on the specific change of greenhouse areas in rapid urbanization. In this study, a field survey of farmers and policy analysis were carried out in six main greenhouse planting areas (Pukou, Lishui, Gaochun, Jiangning, Qixia and Liuhe District) in Nanjing, China. A Tobit model was used to quantify the impact of Vegetable Basket Project on greenhouse expansion. The variables included policy factors (whether it was a vegetable production base and the distance from vegetable production base), location factors (the distance from the vegetable market and the distance from the nearest road) and terrain factor (the slope). The results showed that: 1) The Vegetable Basket Project was an important driving force of greenhouse expansion in Nanjing in recent 20 years, thereby to effectively promote the process of suburban agricultural facilities; 2) In the Vegetable Basket Policy, the most significant impact factor was the planning and construction of vegetable production base on the change of greenhouse areas; 3) The location factors, such as market and traffic, were important impacts on the area of suburban greenhouses. The change proportion of greenhouse areas decreased with the increase of the distance from the vegetable market and roads; 4) There was a regional difference in the change of greenhouse areas. Both market accessibility and traffic convenience played a positive role in the expansion of greenhouses in each district. The policy factors were dominated in the different changes in greenhouse areas. 5) In qualitative analysis, it was found that the Vegetable Basket Policy, together with agricultural, farmers' and farmland policy, promoted the transformation of farmland greenhouses in the suburbs of big cities. [ABSTRACT FROM AUTHOR]

River crab industry plays an important role in agriculture in Nanjing City, Jiangsu Province. In recent years, with the renewal of breeding mode, the breeding of improved varieties and the construction of brand, the river crab industry has made great progress. Taking the aquaculture enterprises and major breeding farmers in the main producing areas of river crab as the main research object, this paper makes a survey on the river crab industry in Nanjing. Based on fishery statistical data and comparison with advanced areas, this paper makes an indepth analysis on the current situation, existing problems and development measures of Nanjing river crab industry, and it is recommended to make full use of external opportunities and give full play to its own advantages, in order to make Nanjing river crab industry develop healthily and rapidly. [ABSTRACT FROM AUTHOR]

Abstract The agent-based modelling (ABM) is commonly used to simulate urban land growth. A key challenge of ABM for the simulation of urban land-use dynamics in support of sustainable urban management is to understand and model how human individuals make and develop their location decisions that then shape urban land-use patterns. To investigate this issue, we focus on modelling the agent learning process in residential location decision-making process, to represent individuals' personal and interpersonal experience learning during their decision-making. We have constructed an extended reinforcement learning model to represent the human agents' learning when they make location decisions. Consequently, we propose and have developed a new agent-based procedure for residential land growth simulation that incorporates an agent learning model, an agent decision-making model, a land use conversion model, and the impacts of urban land zoning and the developers' desires. The proposed procedure was first tested by using hypothetical data. Then the model was used for a simulation of the urban residential land growth in the city of Nanjing, China. By validating the model against empirical data, the results showed that adding agent learning model contributed to the representation of the agent's adaptive location decision-making and the improvement of the model's simulation power to a certain extent. The agent-based procedure with the agent learning model embedded is applicable to studying the formulation of urban development policies and testing the responses of individuals to these policies. Highlights • We construct an agent learning model for urban growth simulation • We assign a computational equation to the payoff function and extend the to-be-reinforced strategy set of RL algorithm • We develop an agent-based procedure with an agent learning model embedded for geo-simulation • The procedure is applicable to studying the formulation of urban policies and testing the responses of individuals to them • Future research should consider embedding social network into learning model and multi-stages learning models [ABSTRACT FROM AUTHOR]

[Display omitted] • A downscaling method to modify ESV by introducing LER was proposed. • Changes in LER and ESV in Nanjing City were consistent from 2000 to 2020. • Ecological restoration programs partially offset the impact of urbanization on ESV. • Water body dominated the ESV and had an important impact on change in ESV. • Proposed method will be valuable for sustainable ecosystem management. The scientific assessment of ecosystem service value (ESV) and landscape ecological risk (LER) is important for ecological security and sustainable development. However, existing studies often separate ESV and LER for a single evaluation, and the single evaluation is limited in guiding ecological conservation. Therefore, proposing an evaluation framework that integrates ESV and LER is urgent. Taking Nanjing City as an example, this study evaluated LER based on the risk evaluation cell and introduced it into ESV evaluation. Then, the influence of land use/land cover change on LER and ESV from 2000 to 2020 was analyzed. The results showed that built-up land and water body/wetland increased by 881.96 km2 and 41.41 km2, and farmland and forest land decreased by 875.46 km2 and 55.83 km2 from 2000 to 2020. The LER was low in the middle and high in the north and south. From 2000 to 2010, the LER increased from 0.67 to 0.68, and it then decreased to 0.61 in 2020. Medium-low risk regions decreased during 2000–2010, and low-risk regions increased and medium-high risk regions decreased during 2010–2020. The ESV increased by 0.77 billion United States dollars (USD) during 2000–2010 but decreased by 0.40 billion USD during 2010–2020. Under the impact of LER, the ESV per unit area of the farmland, forest land, and water body decreased during 2000–2020. The ESV of the water body dominated the total ESV and had an important influence on the change in total ESV. The ESV in Nanjing City during 2000–2020 mainly showed High-High autocorrelation and a few Low-High autocorrelations. Ecological restoration programs increased ESV during 2000–2010, but rapid urbanization reduced ESV during 2010–2020. Integrating social, economic, and ecological resources is necessary to realize the coordinated development of the economy and ecology. The results can provide an important reference for landscape planning and ecosystem management. [ABSTRACT FROM AUTHOR]

In order to understand the regional water resources carrying status and socio-economic development potential, it is necessary to clarify the threshold of water resources supporting the socio-economic scale. By analyzing the basic connotation of water resources carrying capacity (WRCC) and optimizing allocation of water resources, the calculation method of WRCC was further elaborated. Nanjing was selected as the research area and 2015 was the typical year. The change of WRCC of Nanjing after the water resources allocation was calculated and compared with the result of the WRCC to analyze the carrying status of water resources in Nanjing. The results show that the water resources allocation effectively improves the WRCC and relieves the pressure on water resources. [ABSTRACT FROM AUTHOR]

In this paper, the artificial neural network (ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the comprehensive, spatial and complex nature of urban land use. Through a preliminary calculation of the degree of intensive land use of the sample area, representative sample area selection and using the back propagation neural network model to train, the intensive land use level of each evaluation unit is finally determined in the study area. Results show that the method can effectively correct the errors caused by the limitations of the model itself and the determination of the ideal value and weights when the multifactor comprehensive evaluation is used alone. The ANN model can make the evaluation results more objective and practical. The evaluation results show a tendency of decreasing land use intensity from the core urban area to the periphery and the industrial functional area has relatively low land use intensity compared with other functional areas. Based on the evaluation results, some suggestions are put forward, such as transforming the mode of urban spatial expansion, strengthening the integration and potential exploitation of the land in the urban built-up area, and strengthening the control of the construction intensity of protected areas. [ABSTRACT FROM AUTHOR]

Simulation models based on cellular automata (CA) are widely used for understanding and simulating complex urban expansion process. Among these models, logistic CA (LCA) is commonly adopted. However, the performance of LCA models is often limited because the fixed coefficients obtained from binary logistic regression do not reflect the spatiotemporal heterogeneity of transition rules. Therefore, we propose a variable weights LCA (VW-LCA) model with dynamic transition rules. The regression coefficients in this VW-LCA model are based on VW by incorporating a genetic algorithm in a conventional LCA. The VW-LCA model and the conventional LCA model were both used to simulate urban expansion in Nanjing, China. The models were calibrated with data for the period 2000–2007 and validated for the period 2007–2013. The results showed that the VW-LCA model performed better than the LCA model in terms of both visual inspection and key indicators. For example, kappa, accuracy of urban land and figure of merit for the simulation results of 2013 increased by 3.26%, 2.96% and 4.44%, respectively. The VW-LCA model performs relatively better compared with other improved LCA models that are suggested in literature. [ABSTRACT FROM PUBLISHER]

Centralized peasant residence (CPR) is a typical phenomenon in rapid urbanization. The majority of farmers passively change their living and residential styles. The phenomenon has aroused wide concern because it reflects the peasants' life satisfaction and determines their well-being. In this paper, resident satisfaction is evaluated based on six typical CPRs in Nanjing using a fuzzy approach. Results indicate that residents in rural residential areas are satisfied with their social life and location. However, they have a relatively lower satisfaction with their economic situation and community facilities. Nearly 57.5% of respondents are concerned more about their employment and economic situations and less about community life and housing conditions. Considering the life satisfaction priority from four dimensions, improving the life satisfaction priority of rural-concentrated residential areas is suggested. We propose that the CPR location should be increasingly emphasized, and the best approach for ensuring satisfied people in CPRs is simultaneously improving their living condition, job accessibility, and public service. Furthermore, increased attention should be given to jobs, commute time, and cost of living. Rural communities should be surrounded by a new industrial park to realize employment and live integration. [ABSTRACT FROM AUTHOR]

The existing researches on the influence of information and communication technology (ICT) are mainly focused on human activity, whilst with few efforts on urban space. In the e-society, the widespread adoption of ICT devices not only affects almost every aspect of people's daily life and thereby reshapes the spatial development of regions and cities, but also generates a large amount of real-time activity data with location information. These georeferenced data, however, have relatively recently attracted attention from geographers. Adapted from Lynch's framework based on people's perceptions, this paper proposes a framework of urban spatial structure based on people's actual activity, including five elements, namely activity path, activity node, central activity zone (CAZ), activity district, and activity edge. In the empirical study, by using one week's check-in tweets (from February 25 to March 3 in 2013) collected in Nanjing City, the five elements are recognized and analyzed. Through the comparison between our results and urban spatial structure based on population (and land use), we argue that ICT uses: 1) lead to polarize, rather than to smooth, the urban structural hierarchy, due to the dual role of distance; 2) enable a partial decoupling of activity and activity space node, which challenges our conventional understanding of the role of home and the utility of travel; 3) blur the boundaries of activity districts and hence may play a positive role in enriching districts' functions, which should not be overlooked in the current urban transformation in China. [ABSTRACT FROM AUTHOR]

Due to the global increases in urbanisation rates, urban sprawl has become a worldwide issue. In China, the development of rural areas has been affected by urban expansion and adjustments of metropolitan areas by administrative divisions that have led to losses in agricultural lands and ecosystem services. There is the 'paradoxical' desire for governments to promote rural development and protect land resources. Urban fringe sprawl is a prominent issue in the process of rural development. Identifying and measuring sprawl at the urban fringe could assist policymakers to either encourage or discourage this phenomenon. This paper demonstrates use of multidimensional indicators to effectively measure urban fringe sprawl by remote sensing, in addition to demographic and socio-economic data. Using integrated indicators observed in the recent Chinese development context, urban fringe sprawl was measured comprehensively for Jiangning, a district in the city of Nanjing, China. This study indicates that Jiangning is sprawling rapidly. The results also show that the multidimensional indicator approach could provide decision support to create effective long-term land-use planning policies for controlling urban sprawl patterns. [ABSTRACT FROM AUTHOR]

Through the matching relationship between land use types and carbon emission items, this paper estimated carbon emissions of different land use types in Nanjing City, China and analyzed the influencing factors of carbon emissions by Logarithmic Mean Divisia Index (LMDI) model. The main conclusions are as follows: 1) Total anthropogenic carbon emission of Nanjing increased from 1.22928 × 10 t in 2000 to 3.06939 × 10 t in 2009, in which the carbon emission of Inhabitation, mining & manufacturing land accounted for 93% of the total. 2) The average land use carbon emission intensity of Nanjing in 2009 was 46.63 t/ha, in which carbon emission intensity of Inhabitation, mining & manufacturing land was the highest (200.52 t/ha), which was much higher than that of other land use types. 3) The average carbon source intensity in Nanjing was 16 times of the average carbon sink intensity (2.83 t/ha) in 2009, indicating that Nanjing was confronted with serious carbon deficit and huge carbon cycle pressure. 4) Land use area per unit GDP was an inhibitory factor for the increase of carbon emissions, while the other factors were all contributing factors. 5) Carbon emission effect evaluation should be introduced into land use activities to formulate low-carbon land use strategies in regional development. [ABSTRACT FROM AUTHOR]

Abstract: The university town is an important phenomenon in the course of urbanization in China. This article introduces and applies theory of production of space and socio-spatial dialectic to explain the processes and mechanisms of production of space in Xianlin university town in Nanjing City, China. As a typical case, Xianlin university town displays multi-scalar separations. The time-scale separation has four sides: the old and new campuses are completely different; teachers and students spend a significant amount of time commuting that they cannot communicate well; during summer and winter vacations, the university town becomes an “empty nest”; and life of low-income earners is fragmental. The four kinds of spatial scale splits are inside the campus, between universities and downtown, among universities, and between the city and its citizens. Resources and rights have an imbalanced distribution among the different classes, which leads to social space differentiation or alienation. The powers of discourses and land resource distribution are in the hands of the government. University managers are stimulated by the idea of a “larger and newer campus” and keep a watchful eye on competing for more land resources. Planners usually cater to such ideas. However, teachers, students, and low-income earners of the university town are neglected. Social process and the influences of land-use/cover change (LUCC) should be more frequently discussed in the future. [Copyright &y& Elsevier]

Based on the empirical survey of 184 young migrant workers in Nanjing City, this paper makes an in-depth analysis of issues concerning the social integration of young migrant workers from economic integration, cultural integration and psychological integration. The survey results show that the overall level of social integration of young migrant workers is low; the dualistic household registration management system of urban and rural areas is the root cause, the lack of human capital, cultural capital and social capital is the underlying causes, and urban residents' discrimination and exclusion is the external cause; to speed up the social integration of young migrant workers, the key is based on the actual needs of youth migrant workers to take practical measures to gradually integrate them into the city. [ABSTRACT FROM AUTHOR]

Abstract: The Yangtse delta area is one of the most rapidly developing areas in China. There are mega-cities like Shanghai and Nanjing and the surrounding urban areas of different sizes including those along the lower reach of the Yangtse river from Shanghai to Nanjing. In combination with their satellite counties and towns, they form one of the most densely distributed urban areas in China. This is a case study conducted in Nanjing city to evaluate the impact of urban sprawl on soil resources using satellite images and digital soil database maps. The extent of the developed land in the study area and the impact of development on soil resources at a scale of 1:200,000 are estimated. The soil types occupied by the urbanization process are determined by overlaying the soil map on the satellite images (Landsat TM) of the study area at different times (1984, 1995, 2000 and 2003). This study uses a geographic information system (GIS) to combine urban land use maps of different times derived from satellite images with data on soil characteristics contained in soil databases. The results document the rapid expansion of urbanization in Nanjing city, as well as the soil types occupied by the urbanization process, and their quality. The urban area has increased 43,544 ha, 2 times more than in 1984. The urban area expanded at an annual rate of 6.9%. Thirty of the total 32 soil types (soil families) within the city were utilized by the urbanization process among which Loamy typic-Fe-leachic-stagnic anthrosol ranked the highest (12,007 ha). The loss of surface land to urban use in Nanjing city has ranged from 4.8% in 1984 to 11.8% in 2003. Soils of the first class (5349 ha) and second class (20,781 ha) were 61.5% of the total occupied soil area. Results for Nanjing show that residential, commercial, and industrial development, known as “urban sprawl,” appear to follow soil resources, with the better agricultural soils being the most affected. Several soil types appear to be on the verge of being replaced by urban sprawl. Growing urbanization may threaten food security, soil diversity and sustainability. The extent and geographic distribution of soil quality and the pedodiversity for land presently under urbanization in the study area may be determined through modeling. [Copyright &y& Elsevier]

Abstract: An increasing number of industrial, agricultural, and commercial chemicals in the aquatic environment leads to various deleterious effects on organisms, which is becoming an increasingly serious problem in China. In this study, the comet assay was conducted to investigate the genotoxicity to human body caused by organic concentrates in the drinking water sources of Nanjing City from Yangtze River of China, and health and ecology risk due to expose to these organic pollutants were evaluated with the multimedia environmental assessment system (MEAS). For all the water samples, they were collected from four different locations in the drinking water sourer samples, es of Nanjing City. The results of the comet assay showed that all the organic concentrates from the water samples could induce different levels DNA damages on human peripheral blood lymphocytes, and a statistically significant difference (p<0.01) was observed compared with the solvent control, which demonstrated the genotoxicity was in existence. According to the ambient severity (AS) of individual compound, we had sorted out the main organic pollutants in the drinking water source of the four waterworks, and the results showed that there was some potential hazard to human body for all the source water, namely the total ambient severity (TAS) of health for each water source was more than I. However, the TAS of ecology for each water source was less than 1, which indicated that it was safe to ecology. The results of this investigation demonstrate the application of the comet assay and the MEAS in aquatic environmental monitoring studies, and the comet assay found to be fast, sensitive, and suitable for genotoxicity monitoring programs of drinking water source. [Copyright &y& Elsevier]

An understanding of historical and present land use and land cover (LULC) information and its changes, such as urbanization and urban growth, is critical for city planners, land managers and resource managers in any rapidly changing landscape. To deal with this situation, the development of a new supervised classification method for multitemporal LULC mapping with long-term reliable information is necessary. The ultimate goal of this study was to develop a new classification method using harmonic analysis with a minimum spectral distance algorithm for multitemporal LULC mapping. Here, the Jiangning District of Nanjing City, Jiangsu Province, China was chosen as the study area. The research methodology consisted of two main components: (1) Landsat data selection and time-series spectral reflectance reconstruction and (2) multitemporal LULC classification using HA with a minimum spectral distance algorithm. The results revealed that the overall accuracy and Kappa hat coefficients of the four LULC maps in 2000, 2006, 2011, and 2017 were 97.03%, 90.25%, 91.19%, 86.32% and 95.35%, 84.48%, 86.74%, 80.24%, respectively. Further, the average producer accuracy and user accuracy of the urban and built-up land, agricultural land, forest land, and water bodies from the four LULC maps were 92.30%, 90.98%, 94.80%, 85.65% and 90.28%, 93.17%, 84.40%, 99.50%, respectively. Consequently, it can be concluded that the newly developed supervised classification method using harmonic analysis with a minimum spectral distance algorithm can efficiently classify multitemporal LULC maps. [ABSTRACT FROM AUTHOR]