With the rapid economic and social development, China's groundwater pollution becomes serious and urgently needs repairing. However, due to the diversity of pollution and complexity of hydrogeological conditions, many of the remediation techniques actually used are not the best option. At present, researchers have tried to establish and optimize the technical evaluation system of groundwater pollution remediation using a variety of evaluation methods, such as multi-criteria decision analysis method (MCDA), life cycle assessment method (LCA), cost-benefit analysis method (CBA), etc. Aiming at the problem that China still lacks perfect standards and legal norms to guide remediation decision-making this paper reviews the research progress of groundwater pollution remediation technology evaluation methods by means of literature research and compares and analyzes the advantages and disadvantages of different evaluation methods. The results show that MCDA has obvious advantages. In addition, when using AHP to construct the evaluation system, selection of evaluation indicators and determination of index weights have a significant impact on the evaluation results of groundwater remediation technology. In a word, in order to optimize the existing evaluation methods it is necessary to conduct more in-depth research on selection of evaluation indicators, determination of index weights, and organic combination of evaluation methods according to the actual situation in China.

According to the water resources ecological footprint model and system dynamics method, four different scenarios are designed to evaluate and predict the water resources ecological footprint and ecological carrying capacity of the North China Plain (NCP) in the current years (2000—2018) and future years (2019—2050) based on the construction of water resources utilization SD (system dynamics) model of the NCP. The results show the followings: 1) for the current years, the average values of per capita water resources ecological footprint, ecological carrying capacity and ecological profit and loss are 0.427, 0.126 and -0.302 hm²/capita, respectively, and the average values of water resources ecological pressure index and ecological economic coordination index are 3.522 and 1.242, respectively. The water resources in the NCP are under excessive pressure and in an unsafe utilization state. The South-to-North Water Transfer Project can alleviate water resources ecological loss in the NCP to a certain extent. 2) in the future, the average values of per capita water resources ecological footprint under the four scenarios will be 0.392, 0.430, 0.329 and 0.359 hm²/capita, respectively, and the average values of per capita water resources ecological carrying capacity will be 0.121, 0.121, 0.121 and 0.120 hm²/capita, respectively, resulting in per capita water resources ecological losses of 0.271, 0.309, 0.208 and 0.239 hm²/capita. The average values of water resources ecological pressure indexes and ecological economic coordination indexes under the four scenarios will be 3.240, 3.571, 2.734 and 3.011, and 1.251, 1.235, 1.283 and 1.266, respectively. The water resources utilization pressure in the NCP in the future will be large and in an unsafe state. 3) from 2019 to 2050, the pressure and the state of unsafe utilization of water resources will continue in the NCP. Scenario NS4 can not only ensure economic development but also reduce the degree of water resources unsafe utilization, which is a development scenario that should be considered in the NCP in the future. However, it is necessary to promote applications of various water saving measures and technologies and improve water efficiency of various departments. Only in this way can the sustainable utilization of water resources be realized.

Under the situation of rapid economic development emissions of nitrogen oxides (NO_x) from electric power, metallurgy, chemical industry and other industries have posed a huge threat to the ecological environment and human health. Therefore, the country's NO_x emission standards are becoming more and more stringent, NO_x governance is facing severe challenges. Traditional NO_x treatment methods cannot meet increasingly stringent emission standards and the dielectric barrier discharge technology (DBD) has received widespread attention because of its advantages of safety and cleanliness, low price and simple operation. The recent research progress of NO_x removal by dielectric barrier discharge is summarized and discussed, and the NO_x conversion rate, reaction conditions and reaction mechanism are mainly reviewed in terms of reactor structure characteristics, power supply characteristics and gas components. At the same time, the conversion enhancement effect of the dielectric barrier discharge technology in cooperation with various catalysts is also summarized. Finally, challenges, obstacles and future development directions of NO_x removal using dielectric barrier discharge technology are presented.

With the development of industrial production, the emission of volatile organic compounds and pollutant components continue to increase. A variety of technologies and processes for treatment of VOCs have emerged. This paper briefs the typical characteristics of VOCs, summarizes and compares corresponding physical, chemical and biological treatment technologies, and summarizes in detail the treatment technologies such as adsorption, plasma and biological methods. The traditional treatment technology has low cost, mature technology and large processing capacity, but it can not meet the current situation of industrial production, especially decomposition of a variety of mixed polluting gases. Emerging technologies and combined technologies have the advantages of high purification efficiency, no secondary pollution and low energy consumption, which will be a continuous research hotspot in the future. By analyzing the current emission characteristics of VOCs and the corresponding treatment technologies, this paper discusses the most significant advantages and disadvantages of each technology as well as the difficulties that need to be overcome in the future. Finally, the future improvement direction and trend of VOCs treatment methods are put forward.

Taking citric acid-modified pepper straw-based biochar as the object, an optimal process for the adsorption process of methylene blue was studied. The dosage of modified carbon, methylene blue concentration, adsorption time, temperature, solution pH, and shaker speed were taken as investigation factors and methylene blue adsorption as investigation index, the Plackett-Burman (P-B) design was used to screen out the factors of significant effects. And further combined with the Box-Behnken Design (BBD) response surface method, the significant factors were optimized and verified and analyzed to obtain the optimal adsorption process parameters. The results showed that among the selected 6 factors, the order of significance affecting the adsorption capacity of methylene blue was modified carbon dosage > methylene blue concentration > shaking table rotation speed. The interaction effect between the significant factors was as follows: dosage of modified carbon and rotating speed of shaking table > dosage of modified carbon and concentration of methylene blue > concentration of methylene blue and rotating speed of shaking table. After optimization, the optimum adsorption conditions were obtained as follows: the dosage of modified carbon was 45.40 mg, the concentration of methylene blue was 86.00 mg/L, and the rotating speed of the shaking table was 130 r/min. Under these conditions, the adsorption capacity of methylene blue could reach 41.03 mg/g, the difference between the verified value and the model predicted value of 42.24 mg/g was 2.87%, therefore, the P-B/BBD method is stable and effective in optimizing the adsorption process of modified biochar for methylene blue, which provides a data reference for optimizing the adsorption process of carbon materials.

Catalytic iron internal electrolysis coupled biological phosphorus removal can effectively solve the problems of low efficiency of biological phosphorus removal, large dosage of chemical phosphorus removal and difficult process control. It has a broad application prospect. This paper introduces the mechanism of phosphorus removal by catalytic iron internal electrolysis coupled with biological method, emphatically analyzes the influence of three coupling modes of catalytic iron internal electrolysis and biological method on phosphorus removal effect, and points out that the biological preprocessing has a strong ability to resist impact load and can simultaneously realize phosphorus removal, reduce biological toxicity and improve the biodegradability of wastewater. In the biological built-in process, the catalytic iron internal electrolysis filler as the biological carrier greatly improves the number and activity of microorganisms, highlights the electrochemical high-efficiency phosphorus removal, and strengthens the biological nitrogen and phosphorus removal capacity. The biological post processing can effectively slow down the fouling on the surface of packing but it is rarely concerned because of its effluent chromaticity. It is concluded that new materials for catalytic iron internal electrolysis and their coupling process with biological method are still the main research direction in the future.

Combs the characteristics and existing problems of road traffic noise pollution prevention and control in China, analyzes the international experience in road traffic noise pollution prevention and control management. Suggestions for further work are put forward through a comparative study. At present, there are many problems in China's urban road traffic noise, such as strong emission sources, large differences between cities, lack of measures and standards, low noise compliance rate in the areas on both sides of the main traffic line and difficult to solve complaints. From the experience of road traffic noise pollution prevention and control in typical foreign countries, a sound road traffic noise pollution prevention and control standard system should be developed, and joint control of quality standards and emission standards should be adopted. China should issue guidance on road traffic noise pollution prevention and control, that the local government should improve the control standards for road traffic noise emission, and that road traffic noise control should be gradually strengthened.

Based on OMI data product, the spatio-temporal variabilities characteristics of ozone column concentration and its correlation with influential factors in Fujian province are analysed using spatial information technology and Pearson correlational analysis method for the period of 2011 to 2020. The results show that the lowest monthly average value was 260.10 DU in April and the highest 283.97 DU in October. The monthly change was wavy, the order of seasonal mean values was autumn, summer, winter and spring, with autumn being obviously higher than the other three.. The variation range of annual average values was 265.18-275.09 DU, the lowest in 2013 and the highest in 2014, and the total mean value of ozone in recent 10 years was 270.19 DU. In terms of spatial distribution, monthly averages were generally distributed as a relatively high value area from July to December and as a relatively low value area from January to June. The spatial distribution of the mean values in autumn was in a relatively high area, and latitude changes in autumn and summer were more obvious than those in spring and winter. The spatial distributions of average annual values in 2013 and 2016 were in the relatively low value areas, while 2011, 2012, 2014 and 2018 in relatively high value areas. In the recent ten years, the distribution of the total mean values in the north was higher than that in the south, and the relatively high value areas were mainly in Ningde City, Nanping City and the north of Fuzhou City, while the relatively low value areas were mainly in Zhangzhou City, Xiamen City, and the south of Longyan City and Quanzhou City. The overall trend of distribution of ozone was that the ozone values decreased with the decrease of latitude in the north-south orientation, and it rose from inland areas to coastal areas in the east-west orientation. In terms of correlation of ozone with the influencing factors, temperature and precipitation presented both positive correlation and negative correlation, with positive correlation mainly distributed in coastal cities while negative correlation mainly in inland cities, presenting the characteristics of strong positive correlation gradually changed into strong negative correlation from coastal to inland. For precipitation and ozone, most regions showed negative correlation. The NDVI also showed the coexistence of positive and negative correlations but the area of negative correlation was significantly larger than that of positive correlation, showing a significant negative correlation on the whole.