Chemical Oxygen Demand Emissions Research Articles

Spatiotemporal characteristics and driving factors of chemical oxygen demand emissions in China’s wastewater: An analysis based on spatial autocorrelation and geodetector

The advancement of industrialization and urbanization has exacerbated global water pollution. Chemical Oxygen Demand (COD) serves as a crucial metric for assessing organic contamination in aquatic environments. Consequently, the spatiotemporal characteristics and driving factors of COD emissions have emerged as a significant area of current research interest. This study employs spatial autocorrelation and geodetector methods to rigorously analyze the spatial–temporal patterns and principal drivers of COD emissions in China’s wastewater, drawing on eleven geographic and socio-economic datasets spanning from 2011 to 2019. This study indicates that COD emissions in China’s wastewater have consistently decreased annually between 2011 and 2019, with a marked reduction observed post-2016. Regarding spatial distribution, COD emissions in the eastern region significantly surpass those in the western region, highlighting pronounced regional disparities. The analysis of the global Moran’s Index indicates that the COD emissions across China’s provincial regions demonstrate spatial clustering of similar values, with this clustering intensifying annually. Furthermore, the local Moran’s Index identifies the precise locations of these spatial clusters. Geodetector analysis identified that the consumption of nitrogen fertilizers and the consumption of chemical fertilizers had substantial impacts on COD emissions, whereas the proportion of urban population at year-end and the number of granted inventions exerted lesser effects. Furthermore, the interaction between two factors notably enhances the explanatory power regarding COD emissions. This research underpins the formulation of efficacious pollution control and environmental protection strategies, contributing vital insights for the stewardship of water quality.

Joint Optimization of Urban Water Quantity and Quality Allocation in the Plain River Network Area

Cities located in the plain river network area possess abundant water resources. However, due to urbanization and industrialization, there is a severe water shortage problem caused by poor water quality. To overcome this issue, a multi-objective optimal allocation model of water quantity and quality is proposed. The model considers regional water resources, economic, social, and environmental requirements and uses the NSGA-II genetic algorithm for model solution. Furthermore, to evaluate and analyze the degree of spatial equilibrium of regional water resources and how it relates to economic factors, the study uses the spatial equilibrium theory of water resources and the Gini coefficient of water resources. Jingjiang, a city in Jiangsu Province characterized by a typical plain river network area, was selected as the study area. The results of the optimal allocation of water resources in Jingjiang City show that: (1) total water consumption and chemical oxygen demand (COD) emissions for the current planning period are within their respective limits. In addition, the implementation of the water conservation program has resulted in a 5% reduction in total water shortages and a reduction of COD emissions by 1276 tons, (2) the structure of the water supply in Jingjiang City has been optimized; more than 90% of Ⅳ~V surface water is used for agriculture, and the domestic water supply is mainly from transit water, which effectively ensures that high-quality water is used in the domestic water supply, (3) the spatial equilibrium coefficient of water resources per sub-area is between 0.33 and 0.74, indicating an unbalanced or almost unbalanced level. The application of a water conservation program has resulted in the improvement of the spatial equilibrium level of water resources in each sub-area, with an overall spatial equilibrium of 0.64, indicating a more balanced level; the degree of matching of water resources with population, GDP, and land area is at the matching level, (4) according to the Gini coefficient of the distribution of water resources, the plains river network area displays a better match between water resources and economic and social factors of each water receiving area, thanks to its unique geographical location and natural conditions. This study can serve as a decision-making reference for addressing the urban water quality water shortage problem in the plain river network area.

Regional sustainable and renewable energy development in China: A comprehensive assessment and influencing factors

In order to address regional energy imbalances, it is necessary to assess Sustainable and Renewable Energy (SRE) development and to explore its influencing factors. However, existing literature only focused on one part of the aforementioned solutions, and remained controversial, especially in China. Based on provincial panel data from 2005 to 2020 in China, this study utilized the information entropy method to construct a comprehensive evaluation system for regional SRE development, and a panel model with fixed effects was established, with this composite score as the dependent variable, and with economic, demographic, environmental, and technological factors as independent variables. The results showed regional SRE development deepened from the western to the eastern part of China, and over time. The empirical evidence indicated that the significant positive predictors of SRE development were disposable income per capita, dependency ratio, urbanization rate, railroad mileage, and technology market turnover while the value added of secondary sectors had a significant negative impact on SRE development. No empirical evidence supported the significant association between chemical oxygen demand emissions and SRE development. The founding can provide data support and theory references for policymakers of energy sectors.

Analysis of the Spatial Correlation Network Structure of Agricultural Water Use Efficiency in Northwest China

There are some problems in Northwest China, such as the fragile ecological environment, poor basic conditions of agricultural production, low efficiency of agricultural water use, and difficulty in clarifying the path of agricultural water use efficiency (AWUE) improvement. Based on the superefficiency data envelopment analysis (DEA) model, this study increases the amount of ‘green water’ resources in the agricultural water consumption index of the input index and increases the wastewater pollutants (total chemical oxygen demand emissions; total ammonia nitrogen emissions) in the undesired output index to measure the AWUE in the northwest region. Based on the calculation results of AWUE, combined with the modified gravity model, the connection strength of AWUE between any two provinces in Northwest China is calculated, and the spatial structure and network characteristics of AWUE in this area are analysed via the social network analysis (SNA) method. The results show that the average AWUE in 2020 is nearly two times higher than that in 2011. From the situation of the northwest provinces, the average AWUE of the five provinces is in the order of Qinghai > Shaanxi > Gansu > Ningxia > Xinjiang. The AWUE value, total population, real GDP and per capita GDP of the capital cities of the five provinces in Northwest China are the key factors for the improvement of the connection intensity of AWUE. From 2011 to 2020, the connection intensity and closeness of AWUE in Northwest China increased, and there was a clear network hierarchy. The improvement in overall AWUE in the region is mainly due to the radiation and driving effect of the central province on other provinces. Based on this, the study proposes policy recommendations for gradually realising the AWUE improvement path of the central province (Shaanxi; Gansu)—cooperation circle (Shaanxi–Ningxia; Gansu–Qinghai)—the whole region. The results provide theoretical support and a quantitative basis for optimising the spatial pattern of agricultural water resources and improving AWUE in Northwest China.

The effect of social economy-water resources-water environment coupling system on water consumption and pollution emission based on input-output analysis in Changchun city, China

With the rapid development of social economy, water resources consumed excessively and water pollution emissions increased. However, few studies have considered the feedback of water resources and water environment on social economy. In this study, a social economy-water resources-water environment coupling system was constructed by multiple regression model and system dynamic model. Five scenarios were set to investigate the relationship among industrial restructuring, pollution treatment and water conservation in Changchun city, China. Based on input-output model, this study analyzed the effect of the coupling system on the economic efficiency of sectoral water consumption and pollution emission. The driving factors were identified and the contributions were quantified using structural decomposition analysis model. The results showed that pollution treatment and water conservation promoted economic development and increased Gross Domestic Product (GDP) by 36.76%. The comprehensive effect of industrial restructuring, pollution treatment and water conservation was better than single measures, which made the GDP increment (44.39%), Chemical Oxygen Demand (COD) reduction (34.11%), Ammonia Nitrogen (NH3–N) reduction (52.50%) and total water consumption increment (7.56%) largest. Meanwhile, the comprehensive effect improved the water consumption efficiency of agriculture and service industries, reduced indirect water consumption in industrial sectors, and improved the economic benefits of pollution emissions in all sectors. The industrial restructuring further increased the contribution of population to COD emissions and the contribution of emission intensity to NH3–N emissions. Under the condition of comprehensive effect, the final demand level was the main factor for the increase of COD and NH3–N, contributing 36998.80 t and 821.07 t, respectively. Therefore, the government should pay attention to saving water resources and protecting water environment while developing social economy. The study quantified the coupling relationship between social economy, water resources and water environment, and provided guidance for water resources management in sectors.

International trade of PRC and its place in environmental sustainability

The sustainable development of trade and the environment is related to the sustainability of a region, a country, and even the global economy. As a major trading country, China has achieved remarkable results in international trade growth in recent years, driven by its continuous deepening of open trade policies. Article identify the key factors that contribute to the changes in environmental sustainability in China’s international trade. Research defined the ways of China’s growth of international trade volume with promoting sustainable environmental development. Analysis found the impact and role of the continuous expansion of trade scale on China’s sustainable environmental development. By analyzing the data on the scale and structure of China’s international trade, research checked the data changes that affect the relationship between international trade and environmentally sustainable development. In this paper we substantiate the conceptual provisions of the theoretical and methodological model of the international trade and its place in environmental sustainability: system characteristics (international trade development to total GDP; international trade pattern structure analysis; geographic direction of international trade) and the principles of environmental sustainability (total industrial waste gas emissions and treatment; industrial solid waste generation, disposal and comprehensive utilization; industrial wastewater emissions, industrial chemical oxygen demand emissions, and Industrial ammonia nitrogen emissions).

Political connection and water pollution: New evidence from Chinese listed firms

We analyze the data of 689 Chinese listed firms between 1999 and 2010 to study the relationship between firms’ political connections and their pollution emissions. We find that, ceteris paribus, a polluting firm with politically connected top managers discharges about 25% more chemical oxygen demand (COD) per 10,000 RMB (about 1,500 USD) worth of total output. The impact of political connections on COD emissions gradually fades out with the departure of politically connected top managers. However, political connections do not affect firms’ emissions of unregulated water pollutants or air pollutants that receive high levels of public attention. In addition, we find evidence that polluting firms may leave wastewater treatment units idle, which lessens treatment costs and thus raises pollution emissions. The findings of this study would help advance discussion about managing water pollution and designing effective environmental regulations under a command-and-control policy schema in developing countries.

The nonlinear effect of new urbanization on water pollutant emissions: Empirical analysis based on the panel threshold model

Rapid urbanization has led to a significant increase in water consumption and wastewater discharge. Balancing the relationship between urbanization development and water pollutants emissions is crucial for the sustainable development of the country. Given the uneven regional economic development and resource distribution in China, exploring the relationship between new urbanization and water pollution emissions cannot be limited to a single perspective such as population urbanization. This study developed a comprehensive evaluation index system for new urbanization level. Based on data from 30 provincial-level regions in China from 2006 to 2020, a Panel Threshold Regression Model (PTRM) was used to explore the nonlinear relationship between the new urbanization level and water pollution discharge. The research results show that China's new urbanization level (NUBL) and its subsystems, including population urbanization (P-NUBL), economic urbanization (E-NUBL), and spatial urbanization (SP-NUBL), all have a double threshold effect on chemical oxygen demand (COD) emissions. The promoting effect of NUBL and E-NUBL on COD emissions gradually increased in the later stage of the study. P-NUBL and SP-NUBL show a trend of inhibiting COD emissions after crossing the dual threshold values. Social urbanization (S-NUBL) and ecological urbanization (EL-NUBL) had no threshold effect, but they also had a promoting effect on COD emissions. In addition, the speed of new urbanization in eastern China was significantly faster than that in central and western China, with provinces such as Beijing, Shanghai, and Jiangsu being the first to enter the high threshold stage. The central region began to gradually enter the middle threshold stage, but provinces such as Hebei, Henan, and Anhui are still in the high pollution and high emission stage. The level of new urbanization in western China is relatively low, and future development should prioritize economic construction. Provinces with high thresholds and low water pollution emissions still need to be developed. The results of this study have important implications for promoting the harmonious development of water-saving and sustainable urban development in China.

How do firms respond to the tighter COD discharge standards? Evidence from the pulp and paper industry in China

ABSTRACT The chemical oxygen demand (COD) emissions from the pulp and paper industry in China have declined continuously since the tighter COD discharge standards were implemented in 2008. Using firm-level data from 2003 to 2013, we investigate how China’s pulp and paper firms would respond to the tighter COD discharge standards with a difference-in-differences design. We find that the tighter COD discharge standards have significant causal effects to induce the pulp and paper firms to reduce their COD emissions primarily through adopting cleaner production. However, the effectiveness of the tighter COD discharge standards depends on monitoring and enforcement activities as well as other regulations accompanying with the tighter COD discharge standards, all of which have become strengthened since China’s 11th Five-Year-Plan (FYP, 2006–2010). While strengthened environmental regulations since the 11th FYP are from the top leadership of the Chinese government in order to deal with the increasing environmental degradation, the underlying driving force of the strengthened environmental regulations is from the household demand for better environmental quality as income increases. This study enriches literature not only on firms’ responses to environmental regulations in developing countries but also on environmental regulations and technology adoption as well as environmental enforcement and compliance.

Effects of Aeration on Surface Water Nutrient Dynamics and Greenhouse Gas Emission in Different Straw Returning Paddy Fields

Straw returning is of great significance for improving soil structure, soil fertility, crop yield, and quality. However, straw returning causes environmental problems such as increased methane emission and non-point source pollutant emission risk. How to reduce the negative effects of straw returning is an urgent problem to be solved.In this study, the effects of aerobic treatment on carbon and nitrogen concentration in surface water and greenhouse gas emissions in paddy fields with different treatments of straw returning were systematically compared.The results showed that different treatments of straw returning significantly increased chemical oxygen demand (COD) in the surface water of the paddy field and significantly promoted the methane emission of the rice field and the global warming potential (GWP), although it slightly reduced N2O emission. The increasing trends showed that wheat straw returning>rape straw>broad bean straw returning.Straw returning increased rice yield when compared with the control without straw returning, but the difference was not significant. Aerobic treatment reduced the COD in surface water by 15%-32%, the methane emission of the paddy field by 10.4%-24.8%, and the GWP of paddy field by 9.7%-24.4% under different straw returning treatments, without affecting the rice yield. The mitigation effect of aerobic treatment with wheat straw returning was the best. The results indicated the potential of oxygenation measures in greenhouse gas emission mitigation and COD emission risk reduction in straw returning paddy fields, especially in wheat straw returning paddy fields.

The impact of export VAT rebate reduction on firms' pollution emissions: Evidence from Chinese enterprises

This study investigates firm-level environmental responses to China's export value-added tax (VAT) rebate reduction policy launched in 2007 that aims to reduce exports in high-polluted and high-energy-consumption sectors. First, we combine firm-level export information from the Customs dataset and the list of policy-targeted products to identify firms affected by export VAT rebate reduction policy. Then, we employ a difference-in-differences strategy to examine changes in the affected and unaffected firms' sulfur dioxide and chemical oxygen demand emissions before and after policy implementation. Empirical analysis reveals that the export rebate reduction policy increases firms' pollution emission intensities and decreases their total outputs, leading to a negative but less significant effect on total pollution emissions. Tests to explore the mechanism reveal that firms' financial constraints become tighter if affected by the export VAT rebate reduction, as evidenced by reduced revenues, profits, and total factor productivity. This further translates into lowered purchases of environment-friendly technologies and a worse capacity to adopt clean production practices, which accounts for increased pollutant emission intensities following the export VAT rebate reduction policy.

High-speed rail and firms' environmental performance: empirical evidence from China.

Developing countries are struggling to balance the economic development and environment protection. This paper examines the impact of high-speed rail (HSR) on firm-level environmental performance in China. Using the staggered expansion of China's passenger-dedicated HSR and the panel data of Chinese manufacturing firm-level data from 2002 to 2012, we find that firms exhibit a lower level of chemical oxygen demand (COD) emissions after the opening of HSR. The average geographical slope of city is used as an instrumental variable to address the potential endogeneity problem of the HSR variable. Furthermore, the reduction effect of HSR introduction on firms' COD emission intensity is more pronounced for firms that located in eastern regions as well as technology-intensive and labor-intensive firms. Agglomeration economies, scale effects, and technological innovation are three plausible channels that allow HSR to promote firm environmental performance. Our paper provides new insights into the impacts of introduction of HSR on firm environmental performance and the development of green city.

Study on the environmental effects of two-way foreign direct investment in China’s service industry

A mathematical model was built in this paper to divide the environmental effects of Foreign Direct Investment (FDI) in the service sector in terms of scale effect, structural effect and technical effect. Also, inbound FDI (IFDI) and outbound FDI (OFDI) were put under the same research framework, where the effects of two-way FDI on the emissions of SO2 and chemical oxygen demand (COD) were empirically tested with the 2004-2016 panel data of China’s service sector. The results show that IFDI in the service sector has significantly reduced China’s pollution emissions and improved environmental quality. This is mainly due to the positive technical and structural effects. OFDI in the service sector exhibits different responses to different pollution emission indexes. When there are both IFDI and OFDI in the service sector, SO2 emissions are suppressed to a certain extent, whereas COD emissions are not effectively controlled. In addition, the increased service output scale, per-capita capital stock and R&D input also have varying effects on environmental pollution in China.

Spatial-Temporal Evolution Characteristics of Agricultural Intensive Management and Its Influence on Agricultural Non-Point Source Pollution in China

The influencing mechanism of agricultural non-point source pollution under intensive agricultural management is complicated. This paper adopted provincial panel data from 2008 to 2020 to estimate the level of agricultural intensive management, the agricultural chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) emissions and emission intensity of agricultural non-point source pollution in different regions of China and analyze the spatial-temporal differentiation characteristics. Moreover, the mediation effect model and spatial spillover effect model were adopted to further explore the influence mechanism of agricultural intensive management on agricultural non-point source pollution. The results show that (1) The total emissions and emission intensity of agricultural non-point source pollution both showed an increasing trend, and these areas with high levels of agricultural non-point source pollution are roughly consistent with those areas with high-level of agricultural intensive management. (2) At the overall level, there were mediating effects of natural ecology, agricultural land management, planting and rearing structure and pollution control investment between the relationship of agricultural intensive management and agricultural non-point source pollution, among which agricultural land management was the largest. Additionally, there was significant spatial heterogeneity in the influencing mechanism of agricultural intensive management on non-point source pollution. (3) There were significant spatial agglomeration characteristics in both agricultural intensive management and agricultural non-point source pollution, which showed a fluctuating trend of “rise-decline-rise-decline”. (4) Agricultural intensive management has a significant positive spatial spillover effect on COD, TN and TP emissions of agricultural non-point source pollution. However, environmental regulation could cause agricultural non-point source pollution to be transferred nearby. Scientific understanding of the spatio-temporal differentiation characteristics and influencing mechanism of agricultural non-point source pollution under the agricultural intensive management model is conducive to providing reference for policy regulation.

Why is COD pollution from Chinese manufacturing declining?——The role of environmental regulation

This paper combines the datasets of the Annual Survey of Industrial Firms and Pollution Emission of Chinese Firms, and uses the difference-in-differences method to explore the impact of environmental regulation on firm chemical oxygen demand (COD) emissions. Using China's COD reduction targets in the 11th Five-Year Plan, we show that environmental regulation reduces firms' COD emissions. The mechanism analysis suggests that the decline of firms' COD emissions caused by environmental regulation is not only driven by the cutting of firm's output but also the falling of COD emission intensity, and environmental regulation's effect on COD emission intensity is much larger. Furthermore, we find end-of-pipe treatment is not at work to the decline of COD emission intensity and front-end preventive control takes effect. Besides, exit of the emission inefficiency firms also contributes to the improvement of firm's COD emissions efficiency.

Corncob-pyrite bioretention system for enhanced dissolved nutrient treatment: Carbon source release and mixotrophic denitrification

Solid biomass waste amendment and substrates modification in bioretention systems have been increasingly used to achieve effective dissolved nutrients pollution control in stormwater runoff. However, the risk of excess chemical oxygen demand (COD) leaching from organic carbon sources is often overlooked on most occasions. Pyrite is an efficient electron donor for autotrophic denitrification, but little is known about the efficacy of autotrophic-heterotrophic synergistic effect between additional carbon source and pyrite in bioretention. Here, four bioretention columns (i.e., corncob column (C), pyrite column (P), the corncob-pyrite layered column (L-CP), and the corncob-pyrite mixed column (M-CP)) were designed and filled with soil, quartz sand, and modified media to reveal the synergistic effects. The results showed that the corncob-pyrite layered bioretention could maintain low COD effluent concentration with high stability and efficiency in treating dissolved nutrients. When the influent nitrogen and phosphorus concentrations were 8.46 mg/L and 0.94 mg/L, the average removal rates of ammonia nitrogen, total inorganic nitrogen, and phosphate were 83.6%, 70.52%, and 76.35%, respectively. The scouring experiment showed that placing the corncob in the mulch layer was beneficial to the sustained release of dissolved organic carbon (DOC). Erosion pits were found in the SEM images of used pyrite, indicating that autotrophic denitrifying bacteria in the bioretention could react with pyrite as an electron donor. The relative abundance of Thiobacillus in the submerged zone of the corncob-pyrite layered bioretention reached 38.39%, indicating that the carbon source in the mulch layer increased the relative abundance of Thiobacillus. Coexisting heterotrophic and autotrophic denitrification in this bioretention created a more abundant microbial community structure in the submerged zone. Overall, the corncob-pyrite layered bioretention is highly promising for stormwater runoff treatment, with effective pollution removal and minimal COD emission.

The effect of environmental regulation on the marginal abatement cost of industrial firms: Evidence from the 11th Five-Year Plan in China

The Chinese government set specific provincial reduction targets for sulfur dioxide (SO2) and chemical oxygen demand (COD) in the 11th Five-Year Plan. However, due to the limitations of firm-level data, there is a research gap on the impact of this policy on the marginal abatement cost (shadow price) of targeted pollutants for industrial firms. First, we estimate the shadow prices of SO2 and COD emissions for industrial firms in China from 1998 to 2009 using the quadratic output directional distance function based on the stochastic frontier analysis (SFA). We also use the Environmental Survey and Reporting database, which is a unique nationwide firm-level database including firm-level emission information. Then, using the difference-in-difference-in-differences (DDD) strategy and combining the variation in pollution reduction targets across provinces with the before-and-after policy change, as well as the firms' emissions, we identify the effect of the provincial reduction targets on the shadow prices of the two pollutants. The estimated average shadow prices of SO2 and COD emissions are 3454.96 yuan/ton and 17,560.18 yuan/ton, respectively. The heterogeneous characteristics show that non-state-owned enterprises (non-SOEs), large-scale firms, and firms in the eastern region have higher shadow prices than state-owned enterprises (SOEs), small and medium-scale firms, and firms in the central and western regions. The DDD estimations show that the setting of provincial reduction targets significantly increases the shadow prices of SO2 and COD emissions for industrial firms. Specifically, when the pollution reduction target is one standard deviation higher than the mean, the shadow prices of industrial firms' SO2 and COD emissions increase by 26.11 yuan/ton and 85.52 yuan/ton, respectively, whose SO2 and COD emissions are 10% higher than the average value. Finally, several policy implications are hereby proposed.

How do pollution fees affect environmental quality in China?

Pollution fees are an important financial tool for the government to achieve environmental protection goals. Accordingly, evaluating the emissions-reduction effect of pollution fees has important theoretical value for China's construction of an ecological civilization. Thus, using panel data of China's 30 provinces for the period 2000–2017, we examine the dynamic linkage between pollution fees and sulfur dioxide (SO2) as well as chemical oxygen demand (COD) emissions. We further explore the moderating role of pollution fees in the innovation-emission nexus and regional heterogeneity. The primary findings of our study indicate that: (1) The imposition of pollution fees and technological innovation can help mitigate SO2 and COD emissions. Economic growth shows a significant inverted U-shaped relationship between SO2 and COD emissions; (2) levying pollution fees can effectively promote the technological innovation of enterprises, thus further reducing pollutant emissions; and (3) the impacts of levying pollution fees on SO2 and COD emissions differ across various regions; in other words, significant regional heterogeneity exists between regions. Only in low-fees and low-emission regions can pollution fees help mitigate SO2 emissions. Finally, we provide several policy pathways to promote energy conservation and emissions reduction.

Foreign Direct Investment’s Impact on China’s Economic Growth, Technological Innovation and Pollution

In recent years, China has gradually become one of the countries with the largest levels of foreign direct investment (FDI). FDI has played a significant role in promoting Chinese economic development, and the FDI technology spillover effect is one of the core forces driving China towards reaching new growth milestones. Therefore, due to the country’s interest in development, there is competition for FDI throughout China. However, the existing imperfect environmental protection system cannot prevent FDI from flowing into China’s highly polluting and resource-intensive industrial chain, possibly causing serious environmental problems. Therefore, the topic of properly introducing foreign capital to promote development and effectively end China’s current environmental pollution crisis has become a research focus. To explore FDI’s impact on China’s economic growth, technological innovation, and environmental pollution, we use Chinese provincial panel data for 2004–2016 to construct a dynamic panel simultaneous-equation model. Considering the interrelationships between the equations, we construct economic models of economic growth, technological innovation, and pollution emissions, and incorporate them into the same research system for generalized method of moments (GMM) estimation. Our results show that FDI has a significant and positive direct impact on China’s economic growth and technological innovation, and can furthermore have a significant pull effect on the domestic economy through the backward spillover channel. At the same time, FDI has a direct and significant impact on the increase in regional waste-water discharge, while exhibiting a pollution halo effect on the emission of sulfur dioxide (SO2) and chemical oxygen demand (COD) emissions directly. In addition, we observe “benign feedback mechanism” between technological innovation output and these three types of pollution, namely SO2 emission, COD emissions, and ammonia and nitrogen discharge.

Water environment protection and sustainable development in townlet of China: A case study in Taicang

The Environmental Kuznets Curve (EKC) model was applied to investigate the relationship between economic growth and water environment quality based on panel data of Taicang during 2010–2017. The typical inversed-U shaped relationship has been obtained between GDP (gross domestic product) and indicators of ammonia, total nitrogen (TN) and total phosphorus (TP), respectively. The EKC turning point appeared when the GDP per capita was around US$2270, which was much lower than those in some developed countries (US$11,200). However, the decoupling between chemical oxygen demand (COD) and GDP per capita occurred even before this period, which should be attributed to the strict COD emission regulation being implemented since 2010. Further, analysis based on the Tapio decoupling coefficient elasticity model analyzed the ammonia nitrogen and economic development of each industry. We found that the agriculture no-point was strong decoupling in 2011–2014, then came to Recessive decoupling. The domestic wastewater had been in a strong decoupling state; Both urban non-point and industry experienced expansive negative decoupling, due to strict policy that prioritizes the environment over development and the investment in improvement of environment and techniques, both of them gradually came to strong decoupling. The result demonstrated that the EKC turning point could be appear in earlier economic stage and the decoupling coefficient elasticity could be improved through taking strong regulation measures.