Assessment of potentially toxic pollutants and urban livability in a typical resource-based city, China

Integrated assessment of potentially toxic elements in soil of the Kangdian metallogenic province: A two-point machine learning approach

The accumulation of potentially toxic elements in soil poses significant risks to ecosystems and human well-being due to their inherent toxicity, widespread presence, and persistence. The Kangdian metallogenic province, famous for its iron-copper deposits, faces soil pollution challenges due to various potentially toxic elements. This study explored a comprehensive approach that combinescombines the spatial prediction by the two-point machine learning method and ecological-health risk assessment to quantitatively assess the comprehensive potential ecological risk index (PERI), the total hazard index (THI) and the total carcinogenic risk (TCR). The proportions of copper (Cu), cadmium (Cd), manganese (Mn), lead (Pb), zinc (Zn), and arsenic (As) concentrations exceeding the risk screening values (RSVs) were 15.03%, 5.1%, 3.72%, 1.24%, 1.1%, and 0.13%, respectively, across the 725 collected samples. Spatial prediction revealed elevated levels of As, Cd, Cu, Pb, Zn, mercury (Hg), and Mn near the mining sites. Potentially toxic elements exert a slight impact on soil, some regions exhibit moderate to significant ecological risk, particularly in the southwest. Children face higher non-carcinogenic and carcinogenic health risks compared to adults. Mercury poses the highest ecological risk, while chromium (Cr) poses the greatest health hazard for all populations. Oral ingestion represents the highest non-oncogenic and oncogenic risks in all age groups. Adults faced acceptable non-carcinogenic risks. Children in the southwest region confront higher health risks, both non-carcinogenic and carcinogenic, from mining activities. Urgent measures are vital to mitigate Hg and Cr contamination while promoting handwashing practices is essential to minimize health risks.

The Patterns of Migration of Potentially Toxic Elements from Coal Mining Subsidence Areas and Associated Soils to Waterlogged Areas

It is crucial for effectively controlling potentially toxic element (PTE) pollution to understand the pollution situation, ecological risks, health risks, and migration patterns of PTEs. However, currently, no research has been conducted on the migration patterns of soil PTEs from coal mining subsidence areas to waterlogged areas under different restoration modes. In this study, a total of 15 sediment samples and 60 soil samples were collected from landscaped wetlands, aquaculture wetland, fish-photovoltaic complementary wetland, photovoltaic wetland, and waterlogged areas with untreated coal mining subsidence. The PTE pollution status, ecological risks, health risks, migration patterns, and the important factors influencing the migration were analyzed. The results indicated that the comprehensive pollution level of PTEs in waterlogged areas with coal mining subsidence can be reduced by developing them into landscaped wetlands, aquaculture wetlands, fish-photovoltaic complementary wetlands, and photovoltaic wetlands. Additionally, the closer to the waterlogged area, the higher the Cu content in the subsidence area soil is, reaching its peak in the waterlogged area. The Cd was influenced positively by SOC and pH. The research results were of great significance for formulating reclamation plans for waterlogged areas and controlling PTE pollution.

The combined rhizoremediation by a triad: plant-microorganism-functional materials

The article describes new strategies for the remediation of soils contaminated with organic and inorganic pollutants. The aim of this study is to investigate the synergistic effects of combining plant-microorganism-functional materials for a more effective reduction of soil contamination with toxic chemicals. The innovative triad involves functional materials as a habitat for microorganisms, which helps to control the release of pollutants into the soil solution from the adsorbed form. This, in turn, reduces the toxic effect on microorganisms and plants. Microorganisms play a complex role, consisting of partial biodegradation of pollutants, stimulation of plant growth, and support for nutrient supply. Plants synthesize root exudates that facilitate microorganisms in biodegrading organic pollutants and stimulate their growth. The plant takes up pollutants through the root system, which can be further supported by endophytic microorganisms. The cooperation of the three players produces a synergistic effect that enhances the effectiveness of rhizodegradation supported by functional materials, which is more effective than using microorganisms, phytoremediation, or functional materials alone. The combination of physicochemical methods (functional materials) and microbiological methods (bacteria and fungi, rhizosphere, symbiotic and non-symbiotic) supported by plants (hyperaccumulators) is a promising approach for reducing chemicals from soil. Key examples of the synergistic effects of combining plant-microorganism-functional materials have been provided in this article.

Spatial response relationship between mining and industrial activities and eco-environmental risks in mineral resource-based areas

Mining and industrial activities in mineral resource-based areas are important sources of potentially toxic elements (PTEs) in the soil, which lead to spatial heterogeneity in regional eco-environmental risks. In this study, we analysed the spatial response relationship between mining and industrial activities and eco-environmental risks using Anselin local Moran's I index and bivariate local Moran's I index. The results showed that the proportions of moderate, moderate to strong, and strong pollution of PTEs in the study area reached 30.9%. The high clusters of PTEs ranged from 5.4 to 13.6%, and were mainly distributed around cities. The influence of different types of metal mines on eco-environmental risks was nonferrous metal mines > precious metal mines > ferrous metal mines. In turn, that of different pollution enterprises was manufacturing industry > other industries > power and thermal industries. Our research demonstrates that there was a significant spatial response relationship between densities of mines and enterprises and eco-environmental risk level. High-density metal mines (5.3/100 km2) and high-density pollution enterprises (10.3/100 km2) resulted in the local high risk. Consequently, this study provides a basis for regional eco-environmental risk management of mineral resource-based areas. With the gradual depletion of mineral resources, high-density pollution enterprise area should be paid more attention to, which would pose a threat not only to the environment but also to population health.

Ecological challenges in the economic recovery of resource-depleted cities in China

The depletion of resource reserves will cause stagnation of socio-economic development in resource-based cities. The formation of new sources of economic growth in resource-depleted cities can profoundly change the structure of human activities and affect the environment. The Chinese government has established a list of resource-depleted cities in three batches since 2008 to support these cities in finding new sources of economic growth. The article analyzes the impact of the regeneration process of resource-based cities on ecosystem quality. The paper constructs an inter-city panel dataset covering 281 cities from 2003 to 2018. The article valued the habitat quality of Chinese cities. Habitat quality index and normalized vegetation index were used to measure the long-term and short-term ecological impacts of economic recovery in resource-based cities. Using a difference-in-difference technique, the results show that the central government's economic support for resource-based cities significantly improves the condition of urban ecosystems. However, the long-term ecological effects are still smaller than the short-term changes in ecosystems. The transmission path of support policies affecting the ecological quality of cities depends on the shift in industrial structure and economic scale at the provincial level. In addition, urban-rural differences, regional distribution, and resource endowment also significantly affect the ecological effects of supportive policies.

A Method for Evaluating the Green Economic Efficiency of Resource-Based Cities Based on Neural Network Improved DEA Model

In this study, we use BP neural network to improve the DEA model to conduct in-depth research and analysis on the method of green economic efficiency evaluation of resource-based cities. The traditional DEA cannot make ranking and analysis of effective units, which affects the accuracy of empirical analysis. Accordingly, the BP-DEA model is introduced to further conduct a comparative eco-efficiency analysis of relatively effective provinces. In this study, the optimal inputs and outputs are calculated by DEA, and further, the BP neural network is used to fit the functional relationship between the optimal inputs and outputs, and by adding variables, the trained neural network can be used for the prediction of the optimal outputs. In this study, the BP-DEA model is used to empirically investigate the temporal evolution trend, spatial differences, and efficiency differences in eco-efficiency. Meanwhile, breaking through the limitation that DEA can only calculate regional efficiency values, this study combines the Malmquist index to compare and decompose the eco-efficiency of different provinces to analyze the sources of total factor productivity changes. The results show that the method can clarify the gap between the actual operation of each indicator and the reference point; it can identify how much room for improvement still needs to be made for each indicator, and it can also determine whether each city should be rewarded or penalized and its specific amount. Finally, based on the evaluation of eco-efficiency and the main constraints, corresponding policy recommendations are proposed. Finally, based on the evaluation results of the BP-DEA method, this study analyzes the overall efficiency improvement of cities in the two study areas in three dimensions: urbanization construction, ecology, and economic development put forward seven types of urban efficiency improvement and propose targeted urban development suggestions according to regional characteristics.

Towards the analysis of urban livability in China: spatial-temporal changes, regional types, and influencing factors

The increasing drift of urbanization and its impact on urban human settlements are of major concern for China cities. Therefore, demystifying the spatial-temporal patterns, regional types, and affecting factors of urban livability in China is beneficial to urban planning and policy making regarding the construction of livable cities. In accordance with its connotation and denotation, this study develops a systematic evaluation and analysis framework for urban livability. Drawing on the panel data of 40 major cities in China from 2005 to 2019, an empirical research was further conducted. The results show that urban livability in China has exhibited a rising trend during the period, but this differs across dimensions. The levels of urban security and environmental health are lower than those of the three other dimensions. Spatially, cities with higher livability are mainly distributed in the first quadrant divided by the Hu Line and Bole-Taipei Line. Cities in the third quadrant are equipped with the lowest livability. In addition, the 40 major cities can be divided into five categories, and obvious differences exist in terms of the geographical distribution, overall livability level, and sub-dimensional characteristics of the different types. Furthermore, the results of the System GMM estimator indicate that the overall economic development exerts an inhibiting effect on the improvement of urban livability in present-day China, but this logical effect exhibits obvious heterogeneity in different time periods and diverse city scales. Finally, there are also differences in the influencing direction and degree of specific economic determinants.

Effect of Urban fringes green space fragmentation on ecosystem service value

In this study, an urban fringe green space classification system was established to explore the spatiotemporal variation of green space landscape and ecosystem service value (ESV) based on multi-source land-use data of Ganjingzi district from 2000 to 2018. (1) Results show that the total green space area declined from 359.57 to 213.46 km² over the study period. Green space large plaque index (LPI) and class area both gradually declined, whereas the number of plaques (NP) and plaque density (PD) gradually increased, indicating green space landscape fragmentation. (2) Additionally, the value of green space ecosystem services reduced from 397.42 to 124.93 million yuan. The dynamic degree of ESV change in green space increased or decreased moderately, always being < 0 and showing a decreasing trend of ESV. From a spatial variation perspective, dynamic degrees of ESV variation in the western and northern regions with relatively intensive green space were higher than those in the east. Regarding ESV of various green space types, forest land had the highest functional values of ecological regulation and support, whereas arable land provided the highest functional values of production supply. (3) The ecological service function value of green space system is negatively correlated with PD, NP, edge density, landscape shape index, and Shannon’s diversity index, and positively correlated with aggregation index, contagion metrics, and LPI. The correlation coefficient between the climate regulation function of forest and the change of number of plaques is -0.874. The correlation coefficient of the recreation and culture of the wetland to the plaque density change is no less than -0.214.

Speciation and Potential Ecological Risk of Heavy Metals in Soils from Overlapped Areas of Farmland and Coal Resources in Northern Xuzhou, China

Contamination caused by heavy metals (HMs) in soil of overlapped area of farmland and coal resources (OAFCR) has impact on crops. The concentrations and speciation of As, Cd, Cr, Cu, Pb and Zn were investigated in topsoil of an OAFCR in Xuzhou, China. The results showed that mean concentrations of all six metals were higher than the background values of Xuzhou city and Cd was moderate accumulated with the maximum I_geo equalled to 2.13. Cd showed moderate contamination level (IP_i = 1.75) and potential ecological risk (Er = 44.06). Most of the total Cr, Cu, Ni, Pb, and Zn were presented in the residual forms (above 60%), and the percentages of reducible, oxidisable and residual forms of Pb were 23%, 21% and 43% respectively. Pb and Cd reflected a moderate degree of potential ecological risk and a considerable migration risk and ecotoxicity.

Trees and shrubs from a post-industrial area high in calcium and trace elements: the potential of dendroremediation

That is probably the first study to date of trees and shrubs differing in age and growing on post-industrial soil contaminated with calcium (Ca) and selected toxic metals/metalloids. The obtained results show that an alkaline reaction (less than 9) of soil and an unusually high Ca concentration may help the studied tree species to adapt/survive in unfavorable habitat conditions (high concentration of toxic elements). The efficiency of phytoextraction of toxic elements was so high that, especially for forest animals (roe-deer) that consume, e.g., willow shoots, it could pose a serious threat to health and life, both for them and potentially for humans.

Quantitative Recognition and Characteristic Analysis of Production-Living-Ecological Space Evolution for Five Resource-Based Cities: Zululand, Xuzhou, Lota, Surf Coast and Ruhr

The accurate identification of PLES changes and the discovery of their evolution characteristics is a key issue to improve the ability of the sustainable development for resource-based urban areas. However, the current methods are unsuitable for the long-term and large-scale PLES investigation. In this study, a modified method of PLES recognition is proposed based on the remote sensing image classification and land function evaluation technology. A multi-dimensional index system is constructed, which can provide a comprehensive evaluation for PLES evolution characteristics. For validation of the proposed methods, the remote sensing image, geographic information, and socio-economic data of five resource-based urbans (Zululand in South Africa, Xuzhou in China, Lota in Chile, Surf Coast in Australia, and Ruhr in Germany) from 1975 to 2020 are collected and tested. The results show that the data availability and calculation efficiency are significantly improved by the proposed method, and the recognition precision is better than 87% (Kappa coefficient). Furthermore, the PLES evolution characteristics show obvious differences at the different urban development stages. The expansions of production, living, and ecological space are fastest at the mining, the initial, and the middle ecological restoration stages, respectively. However, the expansion of living space is always increasing at any stage, and the disorder expansion of living space has led to the decrease of integration of production and ecological spaces. Therefore, the active polices should be formulated to guide the transformation of the living space expansion from jumping-type and spreading-type to filling-type, and the renovation of abandoned industrial and mining lands should be encouraged.

Research on Industry Development Path Planning of Resource-Rich Regions in China from the Perspective of “Resources, Assets, Capital”

The development of industries in China’s resource-rich regions is mainly affected by resource reserves, environmental protection, and industrial structural adjustment. The development of resource-oriented industries that can’t support a high-quality regional economy is large but not well developed. This article considers China’s resource product imports and exports, carbon emissions, and industrial structure ratio factors in recent years. It is believed that China’s resource-rich regions have macro-level development bottlenecks, and the general development of a resource-based industries path is proposed based on the perspective of “resources, assets, and capital”. Taking Guangxi Zhuang Autonomous Region as an empirical case, this article analyzes the pattern of regional industrial development by using the input-output method, calculates the degree of inter-industrial correlation, and constructs a regional industrial development system. The results show the following: 1. China’s overall industrial development pattern has undergone major changes; 2. emerging industries and service-oriented industries have risen in development status, and although resource-based industries have a weaker development momentum, they still have an important position; 3. the hierarchical industry development management model is helpful for forming a regional circular economy innovation development pattern. The results also indicate that the integrated management of “resources, assets, and capital” has a positive effect on the development of resource-based industries in resource-rich regions, which affects the overall industrial development pattern of the region and promotes economic development.

Study on Heavy Metal Contamination in High Water Table Coal Mining Subsidence Ponds That Use Different Resource Reutilization Methods

Heavy metals accumulate in high water table coal mining subsidence ponds, resulting in heavy metal enrichment and destruction of the ecological environment. In this study, subsidence ponds with different resource reutilization methods were used as study subjects, and non-remediated subsidence ponds were collectively used as the control region to analyze the heavy metal distributions in water bodies, sediment, and vegetation. The results revealed the arsenic content in the water bodies slightly exceeded Class III of China’s Environmental Quality Standards for Surface Water. The lead content in water inlet vegetation of the control region and the Anguo wetland severely exceeded limits. Pearson’s correlation, PCA, and HCA analysis results indicated that the heavy metals at the study site could be divided into two categories: Category 1 is the most prevalent in aquaculture pond B and mainly originate from aquaculture. Category 2 predominates in control region D and mainly originates from atmospheric deposition, coal mining, and leaching. In general, the degree of heavy metal contamination in the Anguo wetland, aquaculture pond, and fishery–solar hybrid project regions is lower than that in the control region. Therefore, these models should be considered during resource reutilization of subsidence ponds based on the actual conditions.