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Table of Content

Volume 37 Issue 8
25 August 2021
Study on the Current Status of Medical Waste Management and Its Improvement in China
MA Jie, ZHANG Cheng, ZHANG Ai-guo, ZHANG Hou-hu
2021, 37(8):  953-961.  doi:10.19741/j.issn.1673-4831.2020.0828
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Medical waste management is related to the overall situation of public health safety and epidemic prevention and control. Based on the statistical data on the current status of medical waste generation, treatment and disposal in China, in addition to the official management policies and practices, the following common issues related to current medical waste management have been revealed:various different statistical scales, insufficient information management, lacking of self-disposal supporting standards, and insufficient researches on harmless ways of its utilization, a mismatch between supply and disposal capacity, unbalanced distribution of disposal facilities, etc. Finally, considering the impact of the updated status of the epidemic on the treatment and disposal of medical waste, corresponding prospects are put forward in terms of system matching, process connection, implementation, supervision and management, as well as layout optimization. The national and local governments are recommended to take a multi-pronged approach to accelerate the timely update and improvement of the existing management system, to increase the investment in the missing supporting standards, to strengthen research on the recycling path of infusion bottles (bags). And in order to optimize the layout of medical waste disposal facilities, it is necessary to take measures of medical waste classification and distribution management, and combine centralized disposal with emergency disposal. The information statistics paths can be improved via the interconnection of medical waste information management with the establishment of efficient supply and demand docking platforms. Through the synchronous promotion of urban and rural management, to further promote the establishment of a modern system for urban and rural medical waste treatment, to improve the formation of multi-party linkage of information supervision and law enforcement, and to firmly guard the defense line of people's livelihood.
Research Progress on Nitrogen Removal from Low Pollution Water by Different Types of Constructed Wetlands
LI Rong-tao, YANG Ping-guo, LI Lin-lin, LU Shao-yong, DU Zhi-chao, KONG Wei-jing
2021, 37(8):  962-971.  doi:10.19741/j.issn.1673-4831.2020.0933
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Low-pollution water has the characteristics of wide sources, large water volume, strong fluctuation of water quality and quantity, and relatively low concentration of pollutants. Constructed wetland is an effective measure to treat low-polluting water. In this paper, the oxygen increasing mechanisms of two typical oxygen-enhanced constructed wetlands, i.e. tidal flow constructed wetlands and aerated constructed wetlands, for nitrogen removal from low pollution water were described, and their denitrification effects and the influencing factors were analyzed. The results show that in the tidal flow constructed wetland, proper idle time and submerged reaction time can create good aerobic-anaerobic conditions, which is beneficial to the removal of TN; when the operating cycle to be less than 24h, and the submerged ~idle time ratio to be between 0.25-4 and 0.5-7, the wetland would have the best NH3-N and TN removal effect in low-polluted water. Reasonable aeration can make the constructed wetland to maintain a high pollutant removal rate at low temperature (-5-10℃); for the treatment of low-polluted water by aeration constructed wetland, the best air-water ratio is 6:1, and the best aeration part is the bottom of the wetland. In addition, by comparing the denitrification effects of the two constructed wetlands, it shows that the treatment effect of aerated constructed wetlands on the removal of NH3-N and TN was better than that of the tidal flow constructed wetlands, but the treatment effect of COD removal was weaker than that of tidal flow constructed wetlands. Finally, this article also points out the existing problems in the denitrification of low-polluted water in the two constructed wetlands. The results of this study could be used as a reference for similar further researches.
Research on Ecological Environment Quality in Central Yunnan Based on MRSEI Model
NONG Lan-ping, WANG Jin-liang, YU Yuan-he
2021, 37(8):  972-982.  doi:10.19741/j.issn.1673-4831.2020.0821
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This study adopted Central Yunnan as the study area. Data sources used include the Moderate Resolution Imaging Spectroradiometer (MODIS), a digital elevation model (DEM), and socio-economic data. A modified remote sensing ecological model was used to monitor the eco-environmental quality of Central Yunnan. In addition, the spatiotemporal variation in eco-environmental quality was analyzed by means of the variation coefficient, Theil-Sen median degree, and spatial autocorrelation. Finally, a geographical detector was used to isolate influencing factors. The results show that:(1) The eco-environmental quality of Central Yunnan improved insignificantly from 2000 to 2018 and stabilized. Among the four cities in Central Yunnan, Chuxiong Prefecture showed the most stable eco-environmental quality. (2) Spatial aggregation in eco-environmental quality occurred in counties in Central Yunnan. A longitudinal zonal spatial pattern of "High-High aggregation"-"Low-Low aggregation"-"No significance" occurred from the western to eastern parts of Central Yunnan and the eco-environmental quality in the west exceeded that in the east. (3) Improved eco-environmental quality was observed at an altitude exceeding 3 000 m and at a slope ranging from 20° to 30°. The distribution of the areas with poor eco-environmental quality was consistent with that of high population density. (4) The normalized difference vegetation index (NDVI) and WET were positively correlated with eco-environmental quality, whereas the normalized difference built-up and bare-soil index (NDBSI), Land surface temperature (LST), population, and gross domestic product (GDP) were negatively correlated. The interactions between multiple factors showed a greater impact on eco-environmental quality in comparison to that of any single factor. Among these interactions, that between natural factors and socioeconomic factors, such as the NDVI which was affected by anthropogenic activities to a larger extent, had a greater impact on eco-environmental quality.
The Influence of Ecological Cognition and External Environment on the Agricultural Input Reduction Behavior of Rice and Crayfish Co-cropping Farmers: Based on the Survey Data of 589 Farmers in Jiangsu Province
HU Nai-juan, WANG Yu-tao, TAO Bao-rui, ZHU Li-qun
2021, 37(8):  983-991.  doi:10.19741/j.issn.1673-4831.2020.0800
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The rice and crayfish co-cropping mode is one of the existing ecological agriculture modes widely adopted by the farmers in paddy fields of China. Therefore, clarification of the agricultural input reduction behavior and its influencing factors in this mode has an important effect on the efficient utilization of farmland resources and agricultural sustainable development. By taking 589 rice and crayfish co-cropping farmers from 3 cities in Jiangsu Province as the samples, the agricultural input (including fertilizers, pesticides, and feed) behavior and its main influencing factors in the rice and crayfish co-cropping mode were analyzed based on the farmers' behavioral selection theory and the structural equation model. The results show that most of farmers tend to reduce the input of fertilizers, pesticides and feed in the rice and crayfish co-cropping mode. The farmers' cognition to rice and crayfish co-cropping mode and the external environment have significant positive effects on the agricultural input reduction behavior, and the influence of the former is greater than that of the latter. In addition, the influence factors, including the farmers' cognition that the rice and crayfish co-cropping mode enables the agricultural input reduction, and excessive agricultural input will lead to environmental pollution, the guidance given by the agricultural technology department, agricultural insurance, agricultural subsidies and neighborhood effect all could significantly impact the agricultural input reduction behavior. Accordingly, it is proposed that comprehensive capital endowment of farmers might be improved, the agricultural technology department should increase the efforts to give guidance and strengthen the effect, the support policies and rewards and punishment mechanisms should be improved, and the brand of rice and crayfish should be established.
Characteristics of Carbonaceous Aerosols in Ambient PM2.5 During the COVID-19 Period in Nanjing
JI Yuan, ZHAO Qiu-yue, CHEN Feng, CHEN Dong
2021, 37(8):  992-1000.  doi:10.19741/j.issn.1673-4831.2020.0857
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In order to explore the variations of carbon components[including organic carbon (OC) and element carbon (EC)] in PM2.5 at the urban area of Nanjing during the breakout of COVID-19 period, PM2.5, OC and EC mass concentrations were measured by online monitoring from January to February 2020. Compared to the concentrations before the emergency response, the PM2.5 concentration after the emergency response was reduced by 41.2% and EC reduced by 57.9%. These results indicate that the shutdown significantly reduced PM2.5 and EC concentrations, but the OC concentration increased. Before the emergency response, the OC and EC concentrations were low in daytime and high at night and early morning. After the emergency response, the average concentration of EC only had a slight change within a day and maintained at low concentration level, OC showed a curve trend which was higher in the afternoon and lower in morning and evening. The significant decrease of PM2.5 concentration after the emergency response period led to the increasing of light radiation intensity, which promoted the formation of secondary organic carbon (SOC). The SOC concentration increased when the PM2.5 and EC concentrations decreased, and the correlation between OC and EC also decreased significantly.
Impacts of Damming and Water-storing on Spatial Distribution of Nitrogen and Phosphorus Nutrients During Summer in Heihe River
WANG Yu, KONG De-xing, FENG Qi, ZHANG Xin-yu, ZUO Yi-feng, WANG Shuang, LU Han
2021, 37(8):  1001-1010.  doi:10.19741/j.issn.1673-4831.2020.1035
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For exploring the impact of damming and water-storing on spatial distribution of nutrients in the upper and middle reaches of the Heihe River, the spatial heterogeneity of nitrogen and phosphorus nutrients in water samples and sediments collected from 28 different sampling sites from July to August in 2018 and 2019 was determined and analyzed. The results show that the content of nitrogen and phosphorus basically met the class Ⅲ of water quality standard. Nitrogen in water mainly existed in the form of ammonia nitrogen (NH3-N), while in sediments mostly in the form of nitrate nitrogen (NO3-N) at the upper and middle reaches of Heihe River. From the perspective of distribution characteristics, the contents of total phosphorus (TP) and total nitrogen (TN) in sediment were the highest in the upstream dammed river. Water temperature (WT), salinity (SAL) and dissolved oxygen (DO) are the key environmental factors affecting the distribution of nitrogen and phosphorus; For the middle reaches, TP and TN contents are the second in natural river reach, and chemical oxygen demand (COD), water temperature and pH are the key environmental factors affecting the distribution of nitrogen and phosphorus. Livestock breeding, mineral mining, industrial and agricultural wastewater discharge are the main sources of nitrogen and phosphorus nutrients in the Heihe River water. The retention effect of dam construction and the changes in environmental factors are main reasons for the uneven spatial distribution of nitrogen and phosphorus. Therefore, the key to improve the health condition of Heihe River is to control the exogenous pollution sources caused by human activities and implement a reasonable reservoir operation mode according to the changing characteristics of different types of pollutants.
The Influence of Rural Settlements on Soil Erosion in the Typical Black Soil Region of Northeast China
FENG Lin, LEI Guo-ping
2021, 37(8):  1011-1021.  doi:10.19741/j.issn.1673-4831.2020.0898
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From the perspective of human-land relationship, the study on the impact of typical rural settlements on the ecological environment is of great strategic significance for rationally optimizing the distribution pattern of rural settlements and ensuring food security. Taking Keshan County, a typical black soil region in Northeast China, as an example, spatial analysis methods such as dispersion statistics, kernel density estimation, and spatial correlation measurement models were comprehensively used to explore and reveal the spatiotemporal evolution of rural settlements in Keshan County from 1988 to 2018. The influences of rural settlement distribution characteristics on soil erosion are explored by the landscape index analysis and the gray relational degree quantification model of the generalized variation coefficient based on the RULSE model. The results show that:(1) In the past 30 years, the number of rural settlement areas in Keshan County has increased sharply, and the trend of decentralization is obvious. The spatial distribution is characterized by "high-density multicore agglomeration, low-density widespread distribution", and the distribution center of gravity has migrated to the northeast. (2) The soil erosion is mainly at micro light and moderate level, and the spatial distribution pattern of soil erosion intensity is consistent with the spatial distribution pattern of rural residential areas. (3) The distribution characteristic factors of rural settlement areas have different effects on soil erosion. The distribution range and density of rural settlement areas have a strong relationship with soil erosion.
Ecological Vulnerability Assessment of Qingdao Coastal Zone Based on Landscape Pattern Analysis
ZHANG Jia-chen, GAO Peng, DONG Xue-de, LI Teng, XU Jing-wei, DUN Xing-jian
2021, 37(8):  1022-1030.  doi:10.19741/j.issn.1673-4831.2020.0860
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In order to study the change characteristics of the vulnerability of urban coastal zone landscape types and reveal the temporal and spatial distribution of coastal ecological vulnerability, indicators, such as aggregation degree, fractal dimension reciprocal, patch density, vegetation coverage index and land ecological suitability, were selected to calculate the vulnerability of landscape types. An ecological vulnerability index model was constructed to evaluate the ecological vulnerability of Qingdao coastal zone based on the remote sensing image data of Qingdao in 2009 and 2018. The results show that:(1) Among the coastal landscape types of Qingdao from 2009 to 2018, the area of forest land, water area, residential and industrial land showed an increasing trend, while the area of cultivated land, grassland and unused land tend to decrease, and the six land use types were all transferred to other types. Among them, studies show the largest decrease in unused land, with a reduction ratio of 55.18%, and the residential and industrial land expanded significantly, with an increase ratio of 58.99%; (2) The unused land and grassland are most vulnerable, which means they are easily disturbed by human factors and external environment. The landscape type of forest land is the third most vulnerable, and the water area is the least; (3) There was a decrease trend in the area of ecologically sound areas and severely vulnerable areas in Qingdao coastal zone, with an average annual reduction rate of 16.24% and 16.83% compared with last year, respectively. However, the mild vulnerable areas, general vulnerable areas and vulnerable areas showed an increasing trend, with an average annual growth rate of 0.95%, 10.74% and 11.24% compared with last year, respectively. The overall ecological vulnerability is high in the east and southwest, and low in the middle. Overall, mild vulnerability is the main vulnerability level of Qingdao coastal zone.
Study on Identification of Key Areas for Ecological Protection and Restoration in Resource-exhausted Region: Take Dayu County, Jiangxi as an Example
ZHANG Xiao-ping, HU Zi-hong, WEI Xiao-jian, HUANG Yao-wen
2021, 37(8):  1031-1040.  doi:10.19741/j.issn.1673-4831.2020.0872
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Following the research route of "ecological security pattern-key area-protection and restoration strategy", Dayu County, one of the resource-exhausted counties in China, was taken as the study area. The purposes of the study were to recognize the number and spatial position of several types of key points and areas for ecological protection and restoration, such as ecological source areas, ecological pinch points, barrier points, break points and fragmented ecological spaces, so as to classify the key areas and points and provide corresponding proposals for ecological protection and restoration. The results show that there are 147.36 km2 of ecological source areas, covered by forest, water and pasture, 69 ecological corridors with spatial feature of "two horizontal and five vertical", 12 ecological pinch points, 13 ecological barrier points, 23 ecological break points and 57.46 km2 of fragmented ecological spaces. The key areas could be divided into 5 types of districts, followed with their respective ecological protection and restoration proposals:For the mine restoration district, afforestation should be implemented; For the mountain and water source managing district, the ruined mountains should be restored and the water pollution should be controlled; For the farmland district, consolidation programs and pollution prevention measures should be carried out; For the rural settlement regulation district, some of the settlements should be integrated and the unused rural roads should be reclaimed; For the traffic land optimization district, wildlife corridors should be established and the vegetation should be restored along the traffic roads. The key areas for ecological protection and restoration could be exposed entirely from the view of the establishment of ecological security pattern. The land use type of key areas is a significant factor for classification and strategy development of the protection and restoration districts. It is beneficial for the transition from specific restoration project to systematic restoration in resource-exhausted counties based on study from the integral view of regional ecological security pattern.
Carbon Footprint Analysis of Rice-Procambarus clarkii Integrated Farming System
LIU Jin-gen, YANG Tong, FENG Jin-fei
2021, 37(8):  1041-1049.  doi:10.19741/j.issn.1673-4831.2020.0808
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Investigating the size and composition of carbon footprint is a key issue for the low carbon development of rice-Procambarus clarkii integrated farming system (R-P) in China. In this study, a field investigation was conducted to analyze the composition of the carbon footprint of R-P with carbon footprint theory and its major influencing factors. The results show that the carbon footprint per area of R-P was 7 859 kg·hm-2, which was between that of rice-wheat farming system(R-W, 10 650 kg·hm-2) and single rice farming system(SR, 5 483 kg·hm-2). The carbon footprint per unit output value and carbon footprint per unit profit of R-P are 0.11 and 0.26 kg·Yuan-1, which are 64.26% and 60.65% lower than that of rice-wheat farming system and 67.37% and 45.02% lower than that of single rice farming system, respectively. R-P significantly decreased direct carbon emissions, but did not affect indirect carbon emissions, compared with rice-wheat farming system. And R-P significantly increased indirect carbon emissions, but did not affect direct carbon emissions, compared with the single rice farming system. The carbon footprint of R-P showed a "parabola" trend with Procambarus clarkii yield, output value and profit. When the carbon footprint reached to 7 458, 7 855, and 7 363 kg·hm-2, the yield, output value and profit of R-P can be maximized, respectively. The scale of R-P farm has a significant impact on the carbon footprint of R-P. The small-scale (< 5.00 hm2) and large-scale (> 20.00 hm2) farm is conducive to reducing the carbon footprint and increasing output value and profits. Overall, R-P can effectively reduce emissions and increase efficiency, compared with the traditional farming systems. However, we should pay attention to the trade-off between carbon footprint and economic benefits in order to promote the green and efficient development of R-P.
Spatial and Temporal Patterns of Avian Diversity in Hupingshan National Nature Reserve
JIANG Bo-wen, HE Chun-rong, LIAO Qing-yi, KANG Zu-jie, WEN Zhe, TIAN Shu-rong
2021, 37(8):  1050-1058.  doi:10.19741/j.issn.1673-4831.2020.0902
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Biodiversity is multidimensional and scale-affected, therefore necessitating the analysis of spatial and temporal patterns of birds. To analyze the composition and dynamic of birds in Hupingshan National Nature Reserve and, thus, to fully understand the spatial and temporal patterns of avian distribution, avian diversity in different areas within the Reserve from 2016 to 2017 was assessed. A total of 110 avian species were recorded during the study period, accounting for 25.11% of the total avian species in Hunan Province. To analyze the spatial and temporal patterns of birds in the Reserve, both the alpha diversity index of each monitoring station and beta diversity index of the entire reserve were calculated by month. The variations between different stations, months, seasons, and years were then analyzed using analysis of variance (ANOVA). Next, the Bray-Curtis index of species composition of each altitude section was calculated by season to compare the dissimilarity. Results show that there were significant differences in bird diversity among different monitoring stations (F7,88=7.549, P=0.000 9) and altitudes (F4,91=24.849, P<0.000 1). In addition, the species compositions were significantly different seasonally among different monitoring stations (F3,92=4.189 2, P=0.008 2). In particular, the avian diversity had a significantly high level in the highest-altitude section. The alpha diversity was highest in spring and lowest in winter, owing to more larva being available for birds to eat in spring, and fewer food resources in winter. The beta diversity shows that there are significant seasonal differences in the entire reserve (F3,20=4.186 7, P=0.019 6). The Bray-Curtis index showed that the composition of birds has no significant correlation between seasons (F3,36=1.064 5, P=0.376 2), indicating that, irrespective of season, each altitude section has its own relatively stable species structure. Biodiversity monitoring is a basic work for protecting biodiversity. The results of this study show that there are certain spatial and temporal differences in bird composition, but the composition of birds in each season and altitude is relatively stable. It reflects the relative independence of bird diversity difference with space and time. This research can provide a basis for the monitoring and protection of biodiversity, which is of great significance in protecting and maintaining the overall ecosystem.
Comparing the Environmental Fate of Typical Antibiotics Sulfamethoxazole and Enrofloxacin in Aquaculture Using a Multi-media Environmental Fugacity Model
SHAN Xiang-bao, FANG Long-xiang, SHI Yu-lu, XING Lu-chang, QIU Li-ping, HU Geng-dong, SONG Chao, CHEN Jia-zhang
2021, 37(8):  1059-1065.  doi:10.19741/j.issn.1673-4831.2021.0073
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The antibiotics sulfamethoxazole and enrofloxacin are commonly used in aquaculture in China, but their fates within the culture environment of tilapia are unclear. Based on the "Guidelines for the use of fishery drugs" (NY 5071-2002) and the "Code for the use of enrofloxacin in aquaculture" (SC/T 1083-2007), the distributions of these two drugs within the tilapia culture environment were studied through field culture experiments. The multi-medium environmental fugacity model was used to simulate the behavior and fate of the drugs. The predicted proportional distributions of sulfamethoxazole in the aquaculture water, fish body and sediment were 92.10%, 7.28% and 0.60%, respectively, and for enrofloxacin the proportions were 64.10%, 35.50% and 0.44%, respectively. While the actual measured proportional distributions of sulfamethoxazole in the culture water and fish were 74.87% and 2.66% (muscle 1.03%, liver 1.10%, intestinal content 0.53%), respectively. For enrofloxacin, the fish body accounted for 36.29% (muscle 33.35%, liver 1.62%, intestinal content 1.32%) of the distribution, but enrofloxacin was not detected in either the culture water or sediment samples. The times for sulfamethoxazole levels to decrease to their initial values in the culture water, muscle, liver and intestinal tract[(2.5±0.9) ng·mL-1 in water, (2.7±0.1) ng·g-1 in muscle, (37.0±9.3) ng·g-1 in liver, and (21.5±5.4) ng·g-1 in intestine] were 32.5, 36.0, 13.1 and 20.4 d respectively. For enrofloxacin, the corresponding elimination times were 5.7 d and 10.3 d for liver and intestine, respectively[liver (4.5±0.3) ng·g-1, intestinal tract (31.7±2.7) ng·g-1], but complete elimination did not occur in muscle[initial value of muscle (8.1±2.0) ng·g-1; residual concentration, (55.7±4.9) ng·g-1]. It is suggested that the withdrawal periods for sulfamethoxazole and enrofloxacin should not be less than 36 d and 20 d, respectively. These data will be valuable for the protection of the ecological environment of fishery and to ensure the quality and safety of tilapia aquacultural products.
Study on the Causes and Assessment of Ecological Risk of Soil Pb Pollution at the Old Site of a Relocated Enterprise
HU Yu-xin, SONG Wei, ZHOU Rui-jing, JIN Zi-wen, NI Bao-feng, LI Xiao-peng
2021, 37(8):  1066-1072.  doi:10.19741/j.issn.1673-4831.2020.0892
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Taking the soil of an old site of a relocated enterprise as the research object, the single factor index method, the geo-accumulation index method, and the potential ecological risk index method were used to comprehensively evaluate Pb pollution and ecological risk in the soil. The pollution causes and spatial distribution characteristics of Pb in the soil were also studied from multiple perspectives. The results show that the Pb content of 73.56% of the sampling points exceeded the standard. In terms of pollution level, the average values of single factor index and geo-accumulation index of Pb in the soil in the study site were 1.07 (slightly polluted) and 1.47 (moderately accumulated), respectively. Pb pollution in soil, was particularly heaviy from >6.0~10.0 meters below the soil surface, and then gradually decreased from below 10.0 meters. From the perspective of the causes of Pb pollution in soil, a large amount of backfilled iron sulfide slag, pollution leakage from the original production workshops and raw material storage area, building rubbish and extremely alkaline soil are the main causes of the high content and heavy pollution of Pb in the soil. However, the ecological risk of Pb in soil of this site is relatively low in generally. It could be concluded that the evaluation results of soil Pb pollution and its ecological risk by using multiple methods are relatively consistent and reliable.
Study on the Characterization and the Removal Efficiency of Cd2+ by the Substrate Residues From Cow Dung-Shell Powder Vermireactors
WANG Feng, MIAO Li-juan, WANG Yi-fan, ZHANG Ming-yue, YING Yu-cui, ZHANG Cheng-ye, ZHANG Wei-wen, ZHU Wei-qin
2021, 37(8):  1073-1079.  doi:10.19741/j.issn.1673-4831.2021.0058
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The widespread existence of cadmium (Cd) contamination in soil environment has obtained extensive attention. There is growing interest to use organic wastes to remediate heavy metal pollution to achieve recycle of organic solid waste and the safe utilization of heavy metal contaminated soil. In this study, the vermireactors containing cow dung and shell powder were set up to obtain substrate residues for the removal of Cd2+ from aqueous solutions. The results demonstrated that earthworms showed considerably good survival rate with shell powder or modified shell powder addition. The earthworm treatment could reduce pH, C/N, lipid material and polysaccharide substance contents of substrate residues but increase its cation exchange capacity and the specific surface area, alcohol or carboxylic acids substance, aromatic substance, silicate, and soluble salts. Similarly, the addition of shell powder or modified shell powder could increase pH, cation exchange capacity and the specific surface area of substrate residues. The addition of shell powder added CaCO3, while the modified shell powder addition increased the content of CaCO3, CaO and Ca(OH)2 in substrate residues. The adsorption test showed that the removal efficiency of Cd2+ was the best for the substrate residues from cow dung and modified shell powder after earthworm treatment, and the adsorption rate was 59.9%. Therefore, it is feasible to set up the vermireactors containing cow dung and modified shell powder to produce substrate residues for the removal of Cd2+ in environment.
Effect and the Mechanism of Modified Biochar on Adsorption of Naphthalene
PENG Zhang, GONG Xiang-yi, XIONG Wu-fang, WANG Ze-ya, REN Da-jun
2021, 37(8):  1080-1088.  doi:10.19741/j.issn.1673-4831.2020.1020
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Biochars were prepared from rice husk and chicken manure, and then were modified with HNO3 and NaOH. The effect and mechanism of modified biochar on adsorption of naphthalene were studied. XRD, specific surface area analysis, and infrared spectroscopy were used to characterize the biochar, and the effects of parameters such as adsorbent dosage, solution pH value, and modifying conditions on the adsorption were investigated. The results show that the average pore diameter of the modified biochar decreased, and the total pore volume and the specific surface area increased except for HNO3 modified rice husk biochar. The oxygen-containing functional groups of biochar modified with HNO3 increased, and the aroma of rice husk biochar modified with NaOH increased. The adsorption isotherms of naphthalene by biochar were better fitted by Freundlich model, and NaOH modified rice husk biochar had the best adsorption effect. As adsorbent dosage increased, the unit adsorption capacity of naphthalene decreased; as the pH value of the solution increased, the adsorption capacity of naphthalene by biochar decreased. The modifying conditions show that rice husk biochar is more suitable for NaOH modification; and chicken manure biochar is more suitable for HNO3 modification, and the higher the HNO3 concentration, the better the adsorption effect. The adsorption mechanism of naphthalene by biochar might be void adsorption, especially microporous adsorption, and there was also a part of π-π interaction.