International Journal of Environment and Pollution (23 papers in press)
Research on immobilisation of heavy metals in karst soil in Guizhou Province under the effect of carbonate
by Shaoxia Lin, Mingyang Cui, Zhiqiang Xiao, Changhu Lin
Abstract: Yellow soil and limestone soil are two dominant types of agricultural cultivated soil in carbonatite outcropped regions in Guizhou Province. Heavy metals in these soils are characteristic of high background value and low activity. To explore the relationship between high carbonate content and heavy metal activity in soils, this study simulated immobilisation of heavy metals in yellow soil and limestone soil under the existence of different concentrations of carbonates through laboratory experiments. Results showed that CaCO3 can increase the pH of yellow soil up to 7.08 and the limestone soil up to 8.25. CaCO3 is conducive to immobilisation of heavy metals in yellow soils within a certain range. It can relieve bio-availability of heavy metals in soil. In limestone soils, CaCO3 controls activity of heavy metals by adjusting soil pH and thereby influences solubility product constant of metallic compound precipitation. The adsorption kinetics model revealed that adsorption of heavy metals by yellow soil and limestone soil is not a physical adsorption, but a chemical adsorption based on chemical bonds. The rate of adsorption is controlled by heavy metal diffusion in soil particles and liquid film diffusion. High-concentration carbonates in karst soils in Guizhou Province can inhibit activity of heavy metals. Although the background value of heavy metals in soils in Guizhou Province is high, it hasnt shown serious health risks to crops or human beings.
Keywords: calcium carbonate; heavy metal; yellow soil; adsorption kinetics;.
Geographic information system simulation and assessment for environmental impact of overall urban planning
by Chuhong Li, Bo Zhou
Abstract: In order to achieve the rationality of urban positioning and development direction and the suitability of ecological shadow environment, the environmental impact of overall urban planning based on Geographic Information System (GIS) evaluation method is evaluated. Firstly, a GIS evaluation index system for the environmental impact of urban planning is established, and the regional boundary layer model and the atmospheric motion equation are used to analyze the feasibility of the GIS model. Then, the construction of GIS evaluation model for the environmental impact of overall urban planning is introduced, and spatial division of the planning scheme is carried out. The atmospheric environment and noise environment models of urban planning are established using the land regression method, and the water environment use model is established using the continuous water tank method. Finally, taking X city as an example, the environmental impact of the overall urban planning is evaluated using the GIS evaluation model. The results show that the assessment of environmental impact of urban master planning based on GIS is feasible. In terms of the water quality environment, the GIS model can be used to find out the reasons affecting the water quality environment and provide good guidance for the site selection and planning of factories in cities. In the aspect of atmospheric environment, the congested routes can be found out to provide guidance for urban road planning. In terms of noise environment, the construction site can be selected away from the concentrated residential buildings. The GIS evaluation of urban master plan quantitatively evaluates the atmospheric environment, noise environment, and water environment, which can provide scientific basis for urban master plan. The study provides a good guiding ideology for the overall planning of the city.
Keywords: environmental impact; overall urban planning; geographic information system; evaluation model.
Effects of phosphorus fertiliser type and application rate on leaf traits of sickle lucerne (Medicago falcate L) in a semi-arid environment in Northern China
by Bo Xu, Huimin Jiang, Baoyin Taogetao
Abstract: By observing the micro-structure of sickle alfalfa (Medicago falcate L.) treated with different phosphorus fertilisers, the adaptive mechanism of sickle alfalfa to structures in different phosphorus application rates can be explained, and a theoretical basis for phosphorus environment adapted by alfalfa can be provided. Six micro-morphological structure indicators from 2012 to 2014, including leaf thickness, palisade tissue thickness, spongy tissue thickness, palisade/spongy ratio, CTR and SR, were measured for sickle alfalfa treated with different phosphorus fertilisers. The results show: (1) with increase of phosphorus application rate, leaf thickness firstly increased and then decreased: it was thickest under moderate phosphorous rate; (2) different phosphorus fertiliser types had less effect on leaf thickness.
Keywords: phosphorus fertiliser; leaf micro-structural mechanism; allometry.
Does environmental regulation promote the upgrading of industrial structure? Evidence from the Yangtze River Economic Belt in China
by Yanyun Chen, Yuying Chen, Fang Wang, Kun Liao
Abstract: This paper examines the impact of environmental regulation on regional industrial structure in the Yangtze River Economic Zone of China. We show that the environmental regulation imposes a single-threshold dampening effect on the upgrading of industrial structure. Specifically, the dampening effect decreases significantly after regulation intensity crosses the threshold. In addition, there exists spatial heterogeneity in the relationship between environmental regulation and the industrial structure upgrading across the region. In the lower reaches of the Yangtze River Economic Zone, environmental regulation imposes a single-threshold positive impact on the regional industrial structure upgrading, which is further strengthened when the environmental regulation intensity passes the threshold. On the contrary, there is a single negative relationship between environmental regulation and industrial structure upgrading in the upper and middle reaches of the Yangtze River. Therefore, when imposing environmental regulations, differential strategies across regions and industries should be adopted considering regional differences.
Keywords: environmental regulation; industrial structural upgrade; Yangtze River Economic Zone; threshold model; single threshold effect.
Assessment of pollution load and identifying bioindicator algal species using multivariate statistical techniques: a case study from Damodar River, India
by Savana Lata Dora, Abhiroop Chowdhury, Subodh Kumar Maiti, Rajani Kanth Tiwary
Abstract: The ecological health of Damodar River, flowing through the mining-industrial zone of the mineral-rich Chotanagpur plateau of India, is assessed in this study, and pollution indicator algal species have been identified. As the river flows through weathered lateritic formations of Chotanagpur, Fe (126820
Keywords: pollution; Damodar River; trace metals; bioindicators; algal biodiversity; saprobic index; diversity index; contamination indices; canonical correspondence analysis.
Assessment the risk of urban exposure to polyaromatic hydrocarbons in cities of Transylvania, Romania
by Andreea-Maria Rotaru, Mihail Simion Beldean-Galea
Abstract: The goal of this study is to estimate the urban environmental risk exposure to polyaromatic hydrocarbons (PAHs) in the atmosphere of six cities of Transylvania region using moss as biomonitor and GC-MS analysis.The carcinogenic potential of the measured atmospheric PAHs was estimated by the benzo[a]pyrene toxicity equivalent (BaPeq) and the toxic equivalence factor (TEF), respectively.The PAHs concentration found in the analysed dried moss ranged from 45.27 ng g-1 in T
Keywords: polycyclic aromatic hydrocarbons; urban atmosphere; moss; biomonitors; risk assessment; Transylvania.
Visible symptoms and changes in physiological parameters of Cinnamomum camphora and Michelia chapensis under ozone stress
by Lan Pan, Long-hua Ye, Hong-yue Chen, Gan-wen Lie
Abstract: The responses of Cinnamomum camphora and Michelia chapensis to ozone (O3) exposure in terms of the O3 injury and changes in the physiological parameters of their leaves were examined in charcoal-filtered (CF) air and O3 at 1
Keywords: tropospheric ozone; visible injury; chlorophyll; antioxidative system.
Growth, accumulation and trasnfer of Cu and Zn by Commelina communis under Cu, Zn and their combined pollution
by Zhiqiang Pan, Shuqin Zhang, Dajun Ren, Xiaoqing Zhang, Shuang Liu
Abstract: A pot experiment was carried out to investigate the growth, accumulation and transfer of Cu and Zn in a traditional Chinese plant species named Commelina communis, which were cultivated under single and combined pollution of Cu and Zn. Afterwards, the biomass and Cu and Zn concentrations in the roots, stems and leaves were measured, and the tolerance index (TI), bioconcentration factor (BCF), transportation factor (TF) were calculated. The chlorophyll content, relative electronic conductivity, and malondialdehyde (MDA) were also determined. The results showed that, with increasing single and combined concentration of Cu and Zn, the biomass of Commelina communis initially increased and then decreased. The highest biomass was observed in the Cu200Zn100 treatment group. The Cu tolerance and accumulation capacity of Commelina communis was superior to Zn, the BCF and TF were both higher than that of Zn and more than 1.0. With an increasing Cu and Zn concentration, the relative electronic conductivity and MDA increased eventually and the chlorophyll content declined. In addition, the experiment data revealed that low concentration level of Cu and Zn had a synergistic effect, which low-dose Zn significantly facilitated the adsorption of Cu in Commelina communis. High-dose Cu and Zn tend to antagonistic effects, causing an inhibition to Cu accumulation by the plant. Comprehensively, Commelina communis was a potential hyper-accumulator for Cu and could be applied to the heavy metal contaminated environments.
Keywords: Commelina communis; copper; zinc; combined pollution; accumulation.
Transport and influential parameters of Cryptosporidium from soil to surface water with preferential flow
by Tao Yuan, Sen Cheng, Yadong Kong, Ping Lu
Abstract: Cryptosporidium outbreaks in surface water are the main route of the human infection cryptosporidiosis. However, Cryptosporidium transport from soil to surface water is not clear. In this paper, two transport paths were simulated to determine the transport behaviour and mechanism of Cryptosporidium oocyst substitutes in a soil-water medium (i.e., root path with preferential flow and root-free path without preferential flow) through laboratory experiments. Fluorescent polystyrene microspheres were used as substitutes for Cryptosporidium oocysts. A 50 cm slope model was used to simulate the two-dimensional transport of Cryptosporidium oocyst substitutes under rainfall conditions. The results showed that the preferential flow formed by plant roots enhanced the transport of Cryptosporidium oocysts. Soil physicochemical properties affected the transport of Cryptosporidium oocyst substitutes, and the results indicated that a high sodium ion intensity and organic matter content in soil inhibited the transport of Cryptosporidium oocyst substitutes; low soil pH values enhanced the adsorption by plant roots, thereby inhibiting the transport of Cryptosporidium oocyst substitutes.
Keywords: cryptosporidium oocyst substitutes; transport; preferential flow; influencing factors.
Removal of copper, lead and zinc from artificially contaminated soil samples using EDTA, rhamnolipids, and soapnut in batch experiments.
by Elijah Ugwu, Bhaskar Sen Gupta, Adebayo Adeloye, Nadia Martínez-Villegas
Abstract: The feasibility of the removal of Cu, Pb and Zn from sandy loam soils was investigated in laboratory-scale batch experiments, using soapnut, rhamnolipids, and EDTA (ethylenediamine tetraacetate) as washing agents. Influencing parameters, including the concentration and pH of the washing solutions, soil-solution ratios (weight of soil sample/volume of the washing solution) and washing times, were studied. It was observed that removal efficiencies were influenced by the concentration of the washing solution, pH, soil-solution ratio, and washing time as well as by the addition of EDTA. While an increase in the concentration of the washing solution, soil-solution ratio, washing time and addition of EDTA increases the removal efficiency, an increase in pH of the washing solution decreases the removal efficiency. The results indicate that the heavy metal removal efficiency almost approached a plateau, at pH 3, a soil-solution ratio of 40, a concentration of 3%, and a washing time of 24 h.
Keywords: copper; lead and zinc; saponin; contaminated soil; soil washing; biosurfactant; removal efficiency.
Oil spills risk management system: challenges and prospects in South Africa
by Phindile Tiyiselani Zanele Sabela-Rikhotso, Dewald Van Niekerk, Livhuwani David Nemakonde
Abstract: The potentially devastating consequences of accidental oil spills on the marine ecosystem raise a growing concern on the efficiency of the preparedness and response strategies. Previous studies have explored scientific variables, including the toxicity of pollutants, dispersants and other response mechanisms. This study is, however, limited to the institutional lens of managing oil spills. While there has been a generic focus on marine legislation, a limitation of studies concentrating on institutional and governance principles for managing oil spill risk persist. This article thus critically analyses the risk management system for oil spills in South Africa. A total of forty-two experienced individuals within the field of marine oil spills management participated in the study. This article identifies three salient elements of the risk management system for oil spills that require attention in South Africa. Firstly, the existing legislative arrangements mandating the function of oil spills management is fragmented, highlighting a need for integrated policy reform. Secondly, stakeholders involved in ex-ante and ex-post activities have limited technical capacity in oil spills risk management, suggesting the need for structured training and exercise inputs. Lastly, the complexity of the current financial arrangements creates a gap that undermines resilience, calling for the adoption of budgetary re-allocation and alternative forms of funding.
Keywords: risk management; oil spills; South Africa; institutional capacity; legislative arrangements.
An improvement of PM2.5 concentration prediction using optimized deep LSTM
by Tong-Hyok Choe, Chung-Song Ho
Abstract: Air pollution poses a serious threat to human health and the environment worldwide, of which particulate matter (PM2.5), consisting of suspended particles with a diameter equal to or less than 2.5 ?m, receives increasing attention with deeper recognition of human health risk. Of air pollution abatement technologies, accurate prediction of PM2.5 concentration is a prerequisite for people's health as well as protection and management of the environment of the atmosphere. In the previous studies, many methods were used to predict the concentration of PM2.5, especially including neural network models. In general, neural network models produce outputs of different quality depending on how the model parameters are set. In this paper, we propose a method for optimising the deep Long Short Term Memory (LSTM) model to improve the quality of PM2.5 concentration prediction and use it for PM2.5 concentration prediction. The parameters of the optimised deep LSTM model were determined by using the genetic algorithm, and were applied to predict PM2.5 concentration, thus achieving better results than when the genetic algorithm was not used. The predicted PM2.5 concentration results of the optimised deep LSTM model were compared with the Recurrent Neural Network (RNN) and Gated Recurrent Unit (GRU) models, showing that the LSTM model had improved performance. This method would possibly contribute to enrich solutions in the aspect of air-pollution prediction.
Keywords: air quality; air pollution; PM2.5 prediction; deep LSTM; long short term memory; neural networks; genetic algorithm; optimisation.
Research on carbon footprint reduction and smart pricing decision-making system of green energy consumption
by Zheng Liu, Bin Hu, Ling-ling Lang, Hang-xin Guo, Jing-ying Sun, Kelly Florence
Abstract: Reducing carbon footprint is one of the important purposes of green energy consumption. The article takes the secondary supply chain consisting of a single manufacturer and a single retailer as the research object, and firstly analyes the influence of the supply chain structure on the optimal decision of the game when the supply chain members have different gaming capabilities, by consideration of the optimal total profit of the supply chain system under centralised and decentralised decisions, optimal decision model of supply chain (RS model) under Retailer-Stackelberg game and the decision model of producer and retailer (N model) under Nash game. Finally, the advantages and disadvantages of the optimal wholesale price, the optimal carbon footprint of products, and the retailer's optimal sales price under the two games are compared.
Keywords: complex structures; green energy products; carbon footprints; smart pricing; decision-making systems.
Characteristics of polycyclic aromatic hydrocarbons in fresh snow in Changping district, Beijing
by Yun-Yang Wan, Jia-Jia Fei, Yi Zhang, Shuang-Xin Shi, Liang Dong, Zhi-Huan Zhang
Abstract: To investigate the distribution characteristics and pollution sources of 16 priority
polycyclic aromatic hydrocarbons (PAHs) in heavy snow in Changping district, Beijing, China, and to evaluate the ecological risk of PAHs in snow in the research area, we collected seven subsamples from three sample snow locations, namely, along roadsides, in parks, and in a mountain area (background region). We pretreated the samples by liquid-liquid extraction after melting, and the total contents of the 16 PAHs were determined by gas chromatography-mass spectrometry as 4281.9 ng
Keywords: PAHs; snowfall; ecological risk assessment; pollution source; combustion; incineration.
Photocatalytic degradation of Ciprofloxacin by bagasse-derived graphene oxide, and toxicity test of the degraded products through microbiological assay
by Aditya Kumar Jha, Sukalyan Chakraborty
Abstract: Ciprofloxacin, an antibiotic of fluoroquinolone drug class, is often associated with negative impacts on aquatic ecosystems demanding innovative techniques and materials for treatment before discharge. In the present study, bagasse, a potential solid waste, was used to treat Ciprofloxacin by converting it into Graphene Oxide (GO) using ferrocene reagent as a catalyst by slow thermal pyrolysis. Characterisation of GO by SEM and HRTEM revealed ultra-thin sheet-like layers, while Raman spectroscopy confirmed its high purity and XRD confirmed its crystalline nature. The synthesised material, when tested for removal of Ciprofloxacin through natural solar-irradiated photocatalysis, showed a maximum 81% degradation following pseudo-second-order kinetics. Mass spectrometry confirmed the fragmentation of the antibiotic into lower molecular weight compounds. Further, a microbiological assay of the degraded products on bacterial strains indicated them to be innocuous. The study depicts a circular economic approach to tackling the solid waste disposal problem and wastewater treatment simultaneously.
Keywords: Ciprofloxacin; degradation mechanism; graphene oxide; photocatalytic degradation; sunlight.
Spatial and temporal analyses of airborne particulate matter in South Marmara region of Turkey
by Atilla Mutlu
Abstract: In the lengthy time period between 2007 and 2019, airborne particulate matter (PM10) levels from real-time intensive measurements were analysed to determine how the long-term PM10 levels may vary from the effects of both meteorological parameters and different emission sources in the South Marmara region of Turkey. In this study, the main statistical approaches, such as an analysis of variance, correlation analysis, and multiple and quantile regression analyses, were performed to determine how daily measured long-term PM10 levels varied by the influence of local meteorological parameters in the study area. According to the regression models, the significant contributors in the study area were ambient temperature and wind speeds. The local sources, including quarries, crushing and screening facilities, briquette houses and marble workshops, of airborne PM10 levels may be considered the main contributors to the peak PM10 levels in the study area. Therefore, spatial analyses were performed to understand the main contributor to the PM10 episodes when the highest PM10 levels were observed throughout the studied years. Also, the cluster analysis and weighted concentration analysis (CWT) approach showed that the local sources were mostly associated with the higher PM10 levels during the long-term observation of the study area.
Keywords: PM10; ANOVA; regression analysis; HYSPLIT; cluster; CWT.
Transcriptome analysis of muskmelon respond to cadmium stress
by Yunqiang Wang, Zhen Lei, Xiaoqian Liu, Zhengkang Zou, Licong Yi, Yu Gong, Zhaoyi (corresponding Author) Dai, Junli (corresponding Author) Li
Abstract: Cadmium (Cd) contamination is the most serious and largest heavy metal pollution of China. It is necessary to explore the mechanism of Cd poisoning and the mechanism of resistance to Cd stress in crops. In the study, Illumina sequencing technology was used for transcriptome high-throughput sequencing. The molecular mechanism of Cd stress in muskmelon was investigated using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In addition, through the detection of physiological indexes of muskmelon leaves, it was found that chlorophyll content and POD activity were considerably reduced. In addition, the related genes were significantly up-regulated exposed to Cd. In the study, the main pathways and genes of muskmelon response to Cd stress were analysed, providing a theoretical foundation for future research into the mechanism of Cd stress response.
Keywords: muskmelon; RNA-seq; transcriptome; high-throughput sequencing; cadmium stress; differentially expressed genes; gene ontology; KEGG; physiological indexes; response pathways.
Improved degradation of Orange II by Fe3O4/NiO/NaHSO3 system under visible light irradiation
by Yu Mei, Bin Zhou, Jianfeng Ma, Xinyu Zhang
Abstract: Fe3O4/NiO composite oxides have been synthesised and characterised by various analytical techniques. Fe3O4/NiO was used as the catalyst to activate NaHSO3, and supplemented with visible light illumination, which formed a novel photo-assisted Fenton-like system in degradation of dye in wastewater. By changing the calcination time of the precursor, three composite oxides were obtained. In degradation of the azo dye Orange II, several experimental results show that Fe3O4/NiO(8h) has the best adsorption and catalytic ability, 90% of the dye can be removed within 2 h in the Fe3O4/NiO(8h)/NaHSO3 system. Also the mechanism of the degradation is discussed.
Keywords: Fe-Ni composite oxide; NaHSO3; visible light; degradation.
Special Issue on: Stochastic Computational Models for Air Pollution and Environmental Risk Assessment
Effects of an ICT-based campus energy management system on educational performance: a perspective of a fuzzy DEA approach
by Xuesong Zhai, Yumeng Zhu, Yan Li, Wenzhi Chen
Abstract: The use of Information and Communication Technology (ICT) to digitalise and visualise the campus energy management aided the ideology of green and sustainable campuses. However, the effects of ICT-based energy management systems on educational performance are less explored. Although Data Envelopment Analysis (DEA) has been regarded as a validating efficiency evaluation approach, the data sources were constrained to the objective data set. The subjective educational data are invalid to be employed in the DEA. This study applied fuzzy set theory to the DEA to evaluate the efficiency of an ICT-based campus energy management system on educational performance. The energy-management input data and educational performance output data were collected from 63 universities and colleges in China. The efficiency distinctions across samples may be theoretically explained by fuzzy DEA, emphasising the value of further investigation of an ICT-based energy management system on educational performance by varied school features.
Keywords: campus energy management; education performance; ICT in education; efficiency assessment; fuzzy set; DEA model.
Model and simulation of grassland social-ecological system risk assessment: a case study of Yanchi County, Ningxia
by Caixia Hou, Xiaojie Zhang, Mengmeng Zhang, Mengmeng Wang, Hanliang Fu
Abstract: To effectively control desertification and restore grassland social-ecological system (SES), in 2002, China launched a grazing-prohibited policy in severely desertified areas. At present, a new grazing-prohibited policy is about to start. Whether the policy needs to be adjusted and how to adjust it have become issues that need to be considered. Based on this, Yanchi County, a typical desertification reversal area, was taken as an example to build the grassland SES dynamic model. By adjusting the prohibited grazing time and area, we assessed the risk and resilience of grassland SES. According to the dynamic results, (1) under the current policy, SES resilience will remain stable; (2) When the prohibited grazing time is 273 days and the grazing time is from June to August, the resilience is at its strongest; (3) By adjusting the prohibited grazing area, when the proportion of grazing prohibition is 100%, the resilience is at its strongest.
Keywords: social-ecological system; risk assessment; resilience; system dynamics; prohibited grazing time; prohibited grazing area.
Research on forest carbon sequestration assessment and forest management plan based on TOPSIS method and grey correlation analysis
by Hong Chen, Chao-Chen Tie, Ye Teng, Zhang Geng, Jia-Ming Zhu
Abstract: In view of the impact of climate change on human development, countries have taken measures to reduce carbon emissions and carbon sequestration. Forest carbon sink plays an pivotal part in achieving carbon neutrality in China. China has put forward the 'double carbon' goal of carbon peak and carbon neutralisation. Firstly, using the data of nine forest resources inventory from 1973 to 2018, an evaluation model of forest carbon sequestration effect in China is established, and 24 provinces in China are compared and analysed. Secondly, the grey correlation analysis model is used to study the dynamic change of forest carbon sink effect and forest resources in China. Finally, it provides reasonable advice for the development and management of forest resources in China, improves the level of forest management, and provides a basis for the implementation of China's carbon peak and carbon neutral strategy.
Keywords: climate change; human development; carbon emission; 'double carbon' target; effect evaluation model; grey correlation analysis.
Dynamic characteristics of low-carbon economy investment yields
by Qizhi He, Bo Li, Xu Zhang, Xiang Dai
Abstract: The rapid development of low carbon economics has brought great influence on resources allocation and social welfare. The paper tests empirically the stochastic volatility of low carbon economics investment yields and gives compares it with that of other corresponding variables using the stochastic volatility models, and finds out that there only a weak leverage-effect in the investment yields of Mainland low carbon and strong leverage-effects in the investment yields of Shanghai composite index, China securities high technology and environmental governance and no leverage-effect in the investment yields of China securities energy. The empirical tests show that the investment yield of low carbon economics is influenced by Shanghai composite index, China securities high technology and environmental governance, and there exist break-points in the relationship among low carbon economics and the front variables using constant-coefficient model and break-point model. Finally, conclusions and suggestions are given.
Keywords: stochastic volatility model; leverage-effect; low carbon economics; environmental governance; break-point model.
Assessing ecological efficiency of Chinas urban agglomerations using data envelopment analysis model
by Jie Wu, Yinghao Pan, Zhixiang Zhou, Xiaoxing Liang
Abstract: Air pollution is a increasing serious problem in urban areas with the development of urban agglomeration. Ecological efficiency assessment is considered as a key way in regional environmental regulation, in which a Data Envelopment Analysis (DEA) model is widely used to compute the ecological efficiency score with stochastic factors. This paper focuses on two kinds of relationship among cities within urban agglomerations and constructs a set of DEA models by inserting different relationship matrices. The presented models are used to assess the ecological efficiency of three major urban agglomerations, namely "Beijing Tianjin Hebei" , "Yangtze River Delta" and "Guangdong-Hong Kong-Macao Greater Bay Area", by constructing an index system with pollution emission indexes. The results of an empirical study illustrate the performance of urban agglomerations during 2014 to 2019, and provide details of the efficiency score for their member cities.
Keywords: air pollution; efficiency assessment; data envelopment analysis; urban agglomeration.