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Table of Content

Volume 36 Issue 4
25 April 2020
Nitrous Oxide Eemission Mechanism and Emission Mitigation Measures of Tea Plantation: A Review
ZHANG Ke-bin, WANG Yi, LIU Xin-liang, KANG Man, SHEN Jian-lin, LI Yong
2020, 36(4):  413-424.  doi:10.19741/j.issn.1673-4831.2019.0709
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Tea plantation has become an important source of agricultural nitrous oxide (N2O) emission in China due to high N2O emission factor, high application of nitrogen fertilizer and increasing planting area year by year. In 2013, the total N2O emission of tea plantations in China was estimated to be 40.90 Gg. Therefore, it is urgent to study the N2O emission mechanism and effective emission reduction measures of tea plantations. With the deepening of research on N2O emission process and influencing factors in tea plantations, many summarized emission reduction strategies are regarded as effective measures to mitigate N2O emission in tea plantations. Through the review, we found that:(1) the N2O emissionfrom tea plantations is mainly caused by soil nitrification and denitrification, and the later contricutes more;(2) the main factors affecting N2O emission in tea plantations are meteorological factors (temperature, rainfall) and soil conditions (pH, moisture content, texture, temperature, substrate concentration); (3) effective N2O emission mitigation measures in tea plantations mainly include the application of ammonium nitrogen fertilizer, controlled release nitrogen fertilizer, lime nitrogen fertilizer and deeply placing of nitrogen fertilizer; (4) there are still different opinions in the N2O emission reduction effects among applying organic fertilizer,applying biological nitrification inhibitors, adding alkaline materials, adding biomass charcoal, interplanting leguminous and applying biological fertilizers, which need to be further studied. At present, there are many researches on the influence of different agronomic measures on N2O emission characteristics in tea plantation, but there is no agreement on the effect of N2O emission reduction.This paper comprehensively analyzes the effect and mechanism of different agronomic measures on N2O emissionin tea plantation, hoping to provide theoretical and practical references for further research on N2O emissions mitigation in tea plantation.
Research Trends of Agricultural Non-Point Source Pollution Risk Assessment Based on Bibliometric Method
ZHU Kang-wen, CHEN Yu-cheng, YANG Zhi-min, HUANG Lei, ZHANG Sheng, LEI Bo
2020, 36(4):  425-432.  doi:10.19741/j.issn.1673-4831.2019.0497
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The purpose of this study was to objectively analyze the research progress, research hotspots and research trends of agricultural non-point source pollution (AGNPSP). The research was based on CNKI database and Web of Science database. Statistical analysis was carried out by bibliometric method from the time of publication, research topics, research areas and research method. And relevant analysis was also carried out in combination with GIS technology. The results show that: (1) The total number of the articles published in the two databases was generally on the rise. As on June 15, 2019, the total number of the articles published in the two databases was 147 and 541, respectively. In the five time periods before 2000, 2001-2005, 2006-2010, 2011-2015 and 2016-2019, the average annual numbers of articles published in CNKI and Web of Science databases were 0, 0.50, 3.80, 13.6, 19.5 and 3.22, 10.2, 21.6, 30.6 and 52.25, respectively. (2) The two databases mainly focused on AGNPSP, risk assessment, output coefficient model, hydrological model and GIS spatial analysis, but there were obvious advantages on international research over China in the field of toxicology research. (3) Hotspot analysis found that there were five agglomeration areas in China: Beijing-Tianjin-Hebei, Northeast three provinces, Yangtze River Delta, Shandong and Chongqing-Guizhou-Sichuan, and four agglomeration areas in the world: China, the United States-Canada, Britain-France-Germany, Brazil. The publication vol-[LM]umes in the two databases in Anhui Province were the highest with 13 articles and in China with 165 articles, respectively. (4) There were some differences in the methods of risk assessment research at different scales, and the GIS technology could play a better role in different scales. On the basis of literature analysis, the existing problems were analyzed from basic data observation and acquisition, mechanism research, model self-development, standard formulation and so on. And suggestions were put forward to researchers for reference in this field.
Application of Immobilized Microorganism Technology for the Biotreatment of Eutrophic Water
SUN Xia, LIU Yang, WANG Fang, TAN Lan, ZHANG Hu
2020, 36(4):  433-441.  doi:10.19741/j.issn.1673-4831.2019.0795
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Eutrophication not only affects the quality of water environment, but also destroys water ecological balance, which are hazardous to the environment and human health. The immobilized microorganism technology is the use of physical or chemical methods to confine free microbial cells within a spatial region. With this technology the free microbial cells can be protected from running water, can be recycled, and their biological activity can be maintained, and the pollutants can be effectively removed from water. Therefore, it is considered as an effective method to control eutrophication of water bodies. In this paper, the characteristics of immobilized microorganism technology and its application status in eutrophic water treatment were introduced. The selection and development of traditional and new immobilization carrier, the types of microorganisms that degrade and remove nitrogen and phosphorus pollutants, and the advantages and problems of existing immobilization methods (adsorption, entrapment, encapsulation, covalent binding, cross linking etc.) were reviewed. Some suggestions for future research and developing directions are proposed. This review can provide a reference for the application of immobilization technology to various types of wastewater biotreatment.
Assessment of the Impact Factors of Farmers' Livelihood Vulnerability Under Different Landforms in Karst Areas: A Case Study of Huajiang and Salaxi
REN Wei, XIONG Kang-ning, YING Bin, XIAO Jie
2020, 36(4):  442-449.  doi:10.19741/j.issn.1673-4831.2019.0713
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A comprehensive, multi-index evaluation methodology, entailing the use of a sustainable livelihoods framework and a vulnerability assessment model, and applying data obtained from 558 household-level questionnaires, was conducted to identify factors influencing farmers' livelihood vulnerability associated with different karst landforms. The findings of the study indicate that the livelihood vulnerability of farmers in the gorge areas on the Huajiang Plateau, whose natural and financial capital is at risk, is significantly higher than that of farmers in the elevated Salaxi Plateau. Accordingly, the risk resilience of farmers in the former region, who play an important role in reducing the fragility of farmers' natural and social capital and livelihoods in the latter region, is extremely weak. Moreover, the livelihood vulnerability of farmers in the gorge areas of the Huajiang Plateau is increased by these risks, which, in turn, increases the human and material capital risks and the fragility of farmers' livelihoods in the elevated Salaxi Plateau. Under increasingly severe conditions of ecological degradation and livelihood stress, safeguarding financial capital, improving education levels, supporting livelihood diversification business activities, and strengthening social networks are the main strategic directions that should be pursued to achieve targeted poverty alleviation within the region.
Spatial Pattern Changes and Influencing Factors of Urban-Rural Construction Land Development Intensity in the Lanzhou-Xining Urban Agglomeration
LI Zai-yan, SHI Pei-ji
2020, 36(4):  450-458.  doi:10.19741/j.issn.1673-4831.2019.0644
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It is significant to define the three lines of "urban growth boundary (UGB), ecological security red line and cultivated land protection red line" to clarify the spatial pattern characteristics and evolution process of land development intensity. 39 county-level units of the Lanzhou-Xining(Lan-Xi) urban agglomeration in 1995, 2005, 2015 and 2018 were taken as research object and trend surface analysis, spatial autocorrelation and geo-detection methods were used to analyze the spatial pattern characteristics and influencing factors of urban-rural construction land development intensity in the Lan-Xi urban agglomeration. Results show that, (1) The development intensity of urban-rural construction land in the Lan-Xi urban agglomeration increased from 2.74% in 1995 to 4.45% in 2018. The development intensity of Lanzhou and Xining was the highest, and then decreased from the core areas to peripheral regions;(2)The development intensity of urban-rural construction land in the east and west was relatively low, and those in Lanzhou and Xining were relatively high, which showed an "inverted U-shaped" curve;(3)There was a significant positive correlation of construction land development intensity, and the agglomeration characteristics were obvious, the spatial distribution of cold and hot spots were relatively stable;(4)From 1995 to 2018, the development intensity of urban-rural construction land was affected by factors such as population agglomeration, economic development, industrial structure and altitude. The results of the research can provide reference to the government authorities for decision-making on the control of urban-rural construction land development intensity for high-quality development in the Lan-Xi urban agglomeration.
Spatial and Temporal Variations of the Water Loss and Gain Status at the Monthly Scale in Songnen Plain From 1961 to 2016
LU Zhong, LEI Guo-ping, ZHANG Lu-yang
2020, 36(4):  459-469.  doi:10.19741/j.issn.1673-4831.2019.0889
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Under the background of climate warming, it is a very realistic and important issue facing China that how to accurately analyze the water loss and gain status of agricultural ecosystems. In order to explore the water loss and gain status at the monthly scale in Songnen Plain, remote sensing data, long-time series meteorological data and soil data were used as base date. In this study, water loss and gain models, trend analysis and wavelet analysis were employed to analyze the spatial and temporal variations of water loss and gain status of Songnen Plain in each month of the crop growth cycle (May to September) from 1961 to 2016. The results show that: (1) From 1961 to 2016, the average potential evapotranspiration during the crop growth cycle was between 432.8 and 605.8 mm in Songnen Plain, and its general variation trend was -0.51 mm·a-1. The monthly variation trends from May to September were -0.27, -0.16, -0.09, -0.03 and 0.02 mm·a-1, respectively. (2) The water deficit in the study area was most severe in May and June. The areas with high water deficit were mainly located in the central and western parts of the Songnen Plain, with frequencies between 30% and 50%. The second serious occurred in September, and the areas with high water deficit were located in the northeast, and its frequency was between 20% and 30%. The water deficit was lightest in July and August. (3) According to the periodic regularity and change trend of water loss and gain status, each month showed a clear periodic change on the time scale of 15 years. In addition, from May to July the water loss and gain status showed a periodic downward trend, while for August and September the water loss and gain status showed an upward trend.
Study on Ecological Utilization of Mountain Valley Highland Barley Land in Qomolangma National Nature Reserve Based on One-Year Phenological Monitoring
CAI Kui, SHI Yun-jie, GONG Zi-ling
2020, 36(4):  470-479.  doi:10.19741/j.issn.1673-4831.2019.0762
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In the context of current ecological civilization construction and rural revitalization strategy, the ecological utilization in village level is particularly important. Taking the highland barley land at Z Village of Qomolangma National Nature Reserve as the research area, Brinno TLC 200 phenology camera was used to record the land use change information from August 2017 to August 2018 depending on manual point selection and fixed angle placement, extract the change information of land use, calculate the green leaf index, analyze the regular pattern, and differential degree of land use as well as the vegetation cover change and economic benefits. The findings illustrate that, the land use in the study area was divided into 5-month cultivation period and 7-month grazing period from 2017 to 2018, and presented a pattern of the sowing time of cultivated land > sheep herding period > cattle herding period in accordance with the traditional land use behavior in the region. Meanwhile, the components of farming activities and grazing activities composed the organic circulation system in the study area. The high, middle and low utilization levels of the land in the study area corresponded to the cultivation period, grazing period and fallow period respectively with cultivation period > grazing period > fallow period. In different periods of the year, the vegetation cover changed apparently, and the green leaf index (GLI) had a changing trend of smooth fluctuation-rising-falling-smooth fluctuation, which was consistent with the cultivation and grazing periods. When the GLI fluctuated around 0, cattle, sheep and wild animals presented, together with frequent rainfall. When the GLI was positive number, the labour input increased. The economic benefit of highland barley land was 98.15 yuan every 667 m2, mainly from grain, with high labor input, resulted in overall low economic benefit.
Research on Supply-Demand Relationship for Village Greening in the Typical Areas of Shandong Province
YU Yu-lei, CUI Yi, CHEN Jia-qi, HUANG Li-sha, CAO Ran, XU Cheng-yang
2020, 36(4):  480-487.  doi:10.19741/j.issn.1673-4831.2019.0876
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In order to explore the characteristics and influencing factors of villagers' demand on village greening, and to reveal the supply-demand relationship on village greening, so as to provide scientific basis for ecological livable and beautiful countryside construction, typical sampling method was used to extract 40 villages in Weifang City and Linyi City of Shandong Province and greening situation data was obtained by field survey. By random access to villagers, 325 valid questionnaires were obtained. Most villagers tended to construct recreational parks and greening landscapes for sightseeing. The villagers' demand was rather high in the road greening, courtyard greening, rural green way and park construction. More than 80% of villagers expressed satisfaction to village greening overall situation. The lack of greening subsidies and planning guidance from government were the main factors restricting the development of village greening. Significant differences existed in greening demand within the villagers, who lived in the village with different topography, urban distance, construction types, economic models, and different ages. It is recommended to strengthen the greening of roads, courtyards, and waterfronts, popularize the benefits of farmland forest networks and protect ancient trees; focuse on the construction of leisure and recreational amusement parks and greening landscapes that are beneficial to tourism; focuse on solving the shortage of afforestation funds and the lack of overall planning. It is necessary to solve the problem of lacking greening funds in coastal villages, and provide greening planning guidance for mountainous and industrialized villages.
Effects of Flooding Stress on Physiological Characteristics and Rhizosphere Bacterial Community of Acorus calamus
GU Shi-yun, YANG Fei, ZHANG Yi-min, ZHANG Zhi-wei, XIE Ke-fu, GUAN Xiang-yang
2020, 36(4):  488-498.  doi:10.19741/j.issn.1673-4831.2019.0731
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The typical emergent plant Acorus calamus was selected for a in-situ simulation experiment in Gehu Lake. Effects of different treatments on physiological characteristics and rhizosphere bacterial community of Acorus calamus were investigated at different flooding depths (T0, T1, T2 referred to normal water level, half-submerged water level about 40 cm and completely submerged water level about 80 cm, respectively) and flooding duration (within an experimental period of 42 d). The results show that: (1) Acorus calamus could adapt to 28 d half-submerged environment, but more than 35 d half-submerged or more than 21 d completely submerged environment would aggravate leaf membrane lipid peroxidation, and increase the content of malondialdehyde (MDA), significantly inhibiting the activity of superoxide dismutase (SOD) and the photosynthesis of plant leaves (P<0.05). (2) Comparing the characteristics of rhizosphere bacterial community of Acorus calamus at the beginning of flooding (0 d) and the end of flooding (42 d), it was found that flooding led to the change of rhizosphere bacterial community structure of Acorus calamus, which was less similar to that at the beginning of flooding, but the similarity between different flooding depths was higher. The diversity and richness of rhizosphere bacterial community of Acorus calamus were increased and there were more unique bacterial species at the end of flooding. There was no significant difference in the composition of bacterial community at the level of phylum, class, order, family, genus, but the composition quantity was different. At the level of phylum, the abundance of Cyanobacteria and Firmicutes increased and the abundance of Proteobacteria decreased at the end of flooding. At the level of genus, the abundance of aerobic flora such as Pseudomonas, Thiobacillus, Sulfuricurvum decreased, and the abundance of anaerobic flora such as Prevotella increased, which was related to the low oxygen environment in the rhizosphere caused by flooding.
Study on the Suitable Habitat of Western Population of Brown-Eared Pheasent Crossoptilon mantchuricum Based on MaxEnt Model
LI Hong-qun, NIU Chang-hui, HAN Pei-shi, LIU Xiao-li, FU Yong-yao
2020, 36(4):  499-504.  doi:10.19741/j.issn.1673-4831.2019.0474
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Based on 126 known coordinates and 25 environmental factors of brown-eared pheasent Crossoptilon mantchuricum, and its potential suitable habitat and main influencing factors were analyzed in Huanglong Mountains by using MaxEnt model. Results show that the accuracy of Maxent model was excellent in predicting its potential habitat, with an AUC value of 0.988 and 0.984 for model training and testing. Mean temperature of driest quarter, precipitation of driest month, precipitation of coldest quarter, maximum temperature of warmest month and distance to road were the main environmental factors influencing the habitat of brown-eared pheasant with thresholds of -6.0--4.3 ℃, 4.90-5.75 mm, 15.3-16.8 mm, 23.0-26.3 ℃ and 0-54 m, respectively. The potential distribution areas of the western population are in Huanglong County, Yichuan County, Luochuan County and Hancheng City in Shaanxi Province. The suitable areas of each county or city are as follows: Huanglong County> Hancheng City> Yichuan County> Luochuan County, indicating that Huanglong County is the main living area of the pheasant, followed by Hancheng City, Yichuan County and Luochuan County. At present, two national nature reserves related to the pheasant have been established in Huanglong Mountain, Shaanxi Province. However, the suitable and medium suitable habitats of the pheasant exceeded the boundary of the nature reserve, suggesting that the government or forestry department needs to adjust the planning of the nature reserve or that surveillance should be strengthened in these areas beyond the boundaries.
Characteristics of Polycyclic Aromatic Hydrocarbons (PAHs) Pollution in Aquatic and Terrestrial Vegetables in Guangxi Province
ZHAO Ti-yue, LONG Ming-hua, QIAO Shuang-yu, SUN Qiao-jian, HE Gang-jian, LIANG Yong-sheng
2020, 36(4):  505-514.  doi:10.19741/j.issn.1673-4831.2019.0590
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To explore the characteristics of 16 kinds of PAHs pollution in edible part of aquatic and terrestrial vegetables, 4 kinds of aquatic vegetables and terrestrial vegetables located in the same area were collected for analyzing the content and composition of PAHs in vegetables. Meanwhile, the health risk assessment of PAHs in vegetables was also investigated. The results show that the contents of G16PAHs in the soils of aquatic vegetable fields was 1 235.24 μg·kg-1, higher than those in terrestrial vegetable soils (1 006.22 μg·kg-1). Moverover, the contents of 5 and 6-ring PAHs and 7 PAHs (Gc7PAHs) attributed to Incremental Lifetime Cancer Risk (RILC) were also significantly higher than those in soils of terrestrial vegetable fields. In addition, except the location of Hezhou City, the contents of 6-ring PAHs and Gc7PAHs in edible part of aquatic vegetables were significantly higher than those in terrestrial vegetables too. By contrast, the rates of 2 and 3-ring PAHs in terrestrial vegetables were all over 50%, all significantly higher than those in aquatic vegetables. The edible part of vegetables was mainly contaminated by the low molecular weight of PAHs, and their contents were all higher than those of high molecular weight of PAHs. It was also found that there was a positive correlation between the contents of 5-ring PAHs, 6-ring PAHs and G16PAHs in aquatic vegetables and those in soils. And there was the same correlation between the contents of 5-ring PAHs and Gc7PAHs in terrestrial vegetables and those in soils, but difference was not significant (P > 0.05). The RILC for human being under different ages, which was induced by PAHs-contaminated vegetables, was in an order of child > adult > senior > adolescent. And the value of RILC for male in adult and senior stages was higher than that in female. Meanwhile, the RILC of PAHs in different vegetables was in an order of leafy vegetables > fruit vegetables > aquatic vegetables.
Effect of Lime Application on Yield of Saponins and Related Enzymes Activities of Panax notoginseng Under Cadmium Stress
LI Na, MEI Xin-yue, LI Qi, ZU Yan-qun
2020, 36(4):  515-521.  doi:10.19741/j.issn.1673-4831.2019.0696
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Field experiments were conducted to understand the effects of lime application on biomass, saponin content and activities of enzymes: squaleneepoxidase (SE), dammaraneediol synthase (DS), cytochrome P450 mono-oxygenase and glycosyltransferase (GT) related to saponin synthesis of Panax notoginseng under cadmium stress(cadmium content 6 mg·kg-2). The results show that the biomass of Panax notoginseng increased and Cd contents in Panax notoginseng decreased with the increase of lime application rates. Under Cd stress and application of 3 750 kg·hm-2 lime, biomass and saponin content, SE and DS activities were the highest; Cd contents, P450 mono-oxygenase and GT activities in all parts of Panax notoginseng were the lowest. Cd contents in each part were in the order of fibrous root >rhizome>shoot> main root. The cytochrome P450 and GT activity in each part were significantly reduced by 11%, 21%, 28% and 13%, 33%, 40%, respectively, under 750, 2 250 and 3 750 kg·hm-2 lime application compared with no lime application and the contents of R1, Rg1 and Rb1 improved, the SE and DS activities of the main root of Panax notoginseng increased significantly by 18%, 42%, 61% and 7%, 28%, 54%, respectively. Therefore, under Cd stress, the application of lime could alleviate the toxicity of Cd on Panax notoginseng, and reduce the inhibition of Cd stress on saponin content and related enzyme activities.
Effect of Bacillus Complex on Water Quality and Bacterial Community Structure of Carassius aumtus Culture Water
LI Xue, LIU Shu-feng, YAN Yu-meng, ZHANG Run-jie, WANG Tian-jie, FU Bao-rong
2020, 36(4):  522-530.  doi:10.19741/j.issn.1673-4831.2019.0573
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Bacillus megaterium (A0), Bacillus coagulans (BC), Bacillus subtilis (BS) were compared for their degradation effects on aquaculture water. The effects of the combination of A0+BC and A0+BS on N and P concentrations and bacterial community structure in carp culture water were studied. The results show that the degradation effects of A0+BS on NH4+-N, NO2--N, NO3--N and TP were the most significant, and the degradation rates were 46.3%, 76.3%, 35.6% and 80.3%, respectively. The concentration of TP and NH4+-N conformed to the 3rd grade of National Surface Water Environmental Quality Standard. The concentration of TP in group A0+BC was always higher than that in CK. This result suggests that the combination of A0 and BS had synergistic effect on the removal of NH4+-N, NO2--N, NO3--N, TP, and previous studies show that Bacillus coagulans had no degradation effect on TP. The microbial communities were profiled by high-throughput sequencing of the V3-V4 hypervariable region of 16S rRNA gene using the MiSeq Illumina sequencing platform. The results show that the microbial community diversity in the A0+BS group was the highest. In addition, adding Bacillus complex in aquaculture water reduced the number of Bacteroidets, increased Proteobacteria and Actinobacteria. The relative abundance of Actinobacteria in the A0+BS group was the highest. Lysinibacillus, Solibacillus and Haematobacter were mainly dominant bacterias in the CK group. The dominant strain was Comamonas belonging to heterotrophic nitrification-aerobic denitrifying bacteria in A0+BC and A0+BS group. Other dominant bacteria in A0+BC group Acinetobacter and Pseudomonas were pathogenic bacteria. In A0+BS group dominant bacteria Bosea and Dokdonella were denitrifying bacteria. A0+BS regulated the microbial community structure in the aquaculture water, which improved the water quality of the aquaculture water.
Study on Electrosorption of As Ions in Aqueous Solution by Modified Graphene
XU Bin, WU Wen-qian, GAO Hai-ling, ZHANG Yi-min, ZHANG Shu-ling
2020, 36(4):  531-541.  doi:10.19741/j.issn.1673-4831.2019.0863
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In this paper, the modified graphene material, graphene/titanium dioxide (GA/TiO2) composite, was prepared by hydrothermal method. The morphology, pore structure and electrochemical properties of graphene (GA) and GA/TiO2 were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption, Raman spectroscopy and electrochemistry. Then GA and GA/TiO2 were assembled into electrodes to remove As ions by capacitive deionization (CDI) method. The removal efficiency of As ions was analyzed through different experimental conditions including voltage, circulating flow rate, temperature and initial As ion concentration. The results show that GA/TiO2 had a three-dimensional porous structure with specific surface area of 416.99 m2·g-1 and specific capacitance of 320.75 F·g-1, which were better than that of GA. In addition, the removal performance of As ions by CDI on GA/TiO2 electrode was better than that of GA electrode. The removal efficiency and adsorption capacity of As ions increased with the increase in voltage, but decreased with the increase in temperature. However, the removal efficiency decreased and adsorption capacity increased with the increase in initial ion concentration. The circulating flow rate had no significant effect on the removal efficiency. Moreover, the adsorption process of As ions on GA/TiO2 electrode can be well fitted by the pseudo-first order kinetic model and Freundlich model.
The Model of Aerosol Scattering Hygroscopic Growth During Autumn and Winter in Chengdu
YIN Dan-dan, NI Chang-jian, DENG Ye, ZHANG Zhi-cha, YANG Yin-shan
2020, 36(4):  542-548.  doi:10.19741/j.issn.1673-4831.2019.0374
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Aerosol scattering hygroscopic growth has an important impact on the atmospheric environment. However, there is little relevant research on the west of Sichuan Province. In this study, the hourly atmospheric observations by nephelometer and aethalometer and the environmental and meteorological datasets of Chengdu from October to December 2017 were used. Based on above dataset which include atmospheric visibility, relative humidity (RH) and NO2 mass concentration. Based on above datasets, the corresponding aerosol scattering hygroscopic growth factor f(RH) was calculated. Furthermore, the variations associated with RH were analyzed. The results show that firstly, quadratic polynomial is determined as the optimal aerosol scattering hygroscopic growth model through the comparisons between multi models; secondly, based on this optimal model, the f(RH) increased with RH, and the sharply increased point appears when the RH reached between 86% and 87%; thirdly, the f(RH) of Chengdu is less than that of Pearl River Delta, but it is generally greater than those of Beijing-Tianjin-Hebei region, Yangtze River Delta, as well as Brazil and Portugal.