The aim of this study was to clarify the response characteristics of Chinese cabbage pakchoi (Brassica chinensis L.) under two particle size (100 nm and 1000 nm) polystyrene microplastic (PS-MPs) stress conditions. This study can provide a theoretical basis and experimental reference for the interpretation of the physiological and ecological mechanism of microplastic pollution and the bioremediation of microplastic-contaminated soil. Hydroponic experiments were carried out to study the effects of two particle sizes (100 nm and 1000 nm) of PS-MPs on growth, photosynthetic physiology, antioxidant enzyme activities, nutritional quality, anatomical structure, and canopy temperature in Chinese cabbage pakchoi. The results showed that PS-MPs stress significantly inhibited the growth and development of Chinese cabbage pakchoi. When PS-MPs stress was increased, the phenotypic indicators were significantly reduced. Meanwhile, PS-MPs stress significantly enhanced the oxidative stress response of Chinese cabbage pakchoi, such as the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX) and the content of malondialdehyde (MDA) in leaves. Such a change tended to decrease the thickness of fenestrated and leaf and spongy tissues. Moreover, PS-MPs stress significantly increased the canopy population temperature of the Chinese cabbage pakchoi leaves. Microplastic stress had obvious inhibitory effects and toxic damage on the growth, development, and physical and chemical properties of Chinese cabbage pakchoi.
根据协同治理理论,构建茶农绿色生产行为多主体治理协同度测度指标体系,采用复合系统协同度模型和验证性因素分析模型,利用福建省安溪县、武夷山市和福鼎市872份样本数据,评估茶农绿色生产行为多主体协同治理效应并实证分析其影响因素.结果表明:(1)研究区域茶农绿色生产行为多主体协同治理系统中各子系统有序度较低且存在失衡;(2)安溪县、武夷山市和福鼎市茶农绿色生产行为多主体治理协同度均处于一般协同形态,未达到最优协同状态;(3)治理主体参与度、治理客体发展度、治理机制保障度、治理目标导向度和治理环境促进度5个维度的测度指标均会对茶农绿色生产行为多主体协同治理效应产生显著正向影响且存在差异性.据此提出以下政策建议:充分发挥各治理主体的协同作用,提高茶农绿色生产行为治理参与程度;完善多主体协同治理的实现机制,保障茶农绿色生产行为治理高效协同;健全多主体协同治理的系统结构,增强茶农绿色生产行为治理要素功能.
为探究改性褐煤施用量对北方典型石灰性土壤团聚体及不同粒级团聚体中镉(Cd)分布的影响.向Cd污染土壤中加入多种褐煤基改性材料培养150d后,采用干筛法和湿筛法提取不同粒级土壤团聚体,研究石灰性土壤团聚体及Cd在团聚体中的赋存状况对不同改性褐煤施用量(0、1％、3％和5％)的响应,探明不同形态Cd在土壤各粒级中的分布情况.干筛和湿筛结果表明,随着不同改性材料施用量的增加,土壤中水稳性团聚体含量呈现逐渐增加趋势,褐煤(LI)、褐煤基腐殖酸(LIH)、去矿化褐煤(LID)、腐殖酸树脂(HAR)和腐殖酸接枝共聚体(HAG)处理水稳性团聚体含量分别增加 0.9％～25.2％、5.5％～24.5％、12.1％～46.5％、98.4％～156.1％和127.8％～174.4％;施用改良剂后土壤的水稳性团聚体、平均重量直径、几何平均直径和粒径大于0.25 mm团聚体含量显著提高,分形维数显著下降;各处理砂粒级大团聚体(r1)和粉砂粒级微团聚体(r3)Cd各提取态富集系数较大,粗粉砂粒级微团聚体(r2)Cd各提取态富集系数最小.总之,施用各改性材料不仅可以有效地增加土壤水稳性团聚体含量,还可以有效地将离子交换态、碳酸盐结合态和铁锰氧化态等易效态Cd主要富集在＞0.25 mm大团聚体和≤0.053 mm水稳性微团聚体中,将强有机态、弱有机态和残渣态等难效态Cd富集在≤0.053 mm水稳性微团聚体中,尤其是褐煤基腐殖酸和去矿化褐煤对水稳性团聚体的形成和Cd的富集赋存作用较好.
科学评价村镇建设资源环境承载力,是合理配置乡村生产、生活和生态三大功能空间,促进村镇建设与资源环境协调发展的基础和前提.然而,在村镇建设资源环境承载力评价研究方面,缺少具有系统性和逻辑自洽性的分析框架与指标体系,这限制了开展有地域差异性、历史多变性和系统复杂性的村镇建设资源环境承载力评估和监测工作的开展.在落实乡村振兴战略和实施国土空间规划过程中,亟需构建面向村镇建设需求的资源环境承载力评价指标体系.为此,在总结村镇建设与资源环境承载力研究成果基础上,阐释村镇建设与资源环境承载力关键概念及其协调关系,构建村镇建设资源环境承载力评价技术框架,在遵循指标体系构建原则和指标筛选方法基础上,建立面向宏观尺度村镇建设资源环境本底评价和微观尺度不同主导功能类型村镇建设资源环境承载力测算及其协调性评价的科学化、系统化和规范化的指标体系,并提出关键指标算法和主要参数选择依据.研究结果有望为中国村镇地域资源环境承载力评估与管理提供理论和方法依据,为在国土空间上分区分类推进村镇建设与资源环境协调发展提供科学依据和技术支撑.
生态文明示范区是推进区域环境保护和社会发展协同共赢的重要平台和有效载体,包括国家生态文明建设示范区和"绿水青山就是金山银山"实践创新基地(简称"两山"实践创新基地),分别着力于构建以产业生态化和生态产业化为主体的生态经济体系、探索生态产品价值实现路径和模式,特别是在快速城市化地区.以长江三角洲(简称长三角)区域77个生态文明建设示范区和22个"两山"实践创新基地为对象,综合利用土地利用、夜间灯光和MODIS数据,分别构建遥感生态指数(remote sensing ecological index,RSEI)和综合夜间灯光指数(compoun-ded night light index,CNLI)代表生态环境质量和城市化水平,并采用空间叠加分析方法和耦合协调度模型探析长三角生态文明示范区建设水平和时空差异性.结果表明:(1)生态文明示范区在长三角区域分布具有不均衡性,生态文明建设示范区分布较为集中且以平原地形为主,"两山"实践创新基地分布较分散,以山地地形为主.(2)生态文明示范区生态用地面积占比超70％,具有较好的生态环境基础,"两山"实践创新基地RSEI指数高于生态文明建设示范区,生态环境质量优越,但更具脆弱性.(3)生态文明建设示范区CNLI指数及其增速均大于"两山"实践创新基地,具有更高的城市化水平和发展速度.(4)2017-2021年,生态文明建设示范区和"两山"实践创新基地RSEI和CNLI指数的耦合协调度呈现不断增加趋势,平均增幅分别为10.55％和8.90％,生态文明建设取得一定成效,其中江浙两省交界处耦合协调度最高.
生态环境质量的优劣一定程度上决定着人类社会能否实现可持续发展,探明乡村发展对生态环境的作用方式及程度,对于区域实现乡村振兴和可持续发展具有一定的现实意义.以陕西省为研究对象,以县域为研究单元,利用长时间序列的遥感生态指数(RSEI)表征陕西省生态环境质量的时空变化特征与变化趋势,借助时空地理加权回归模型,探究生态环境质量的影响因素及其空间差异.研究表明:(1)2000-2020年生态环境质量整体呈向好趋势,RSEI值从2000年的0.483 3增长到2020年的0.651 2,生态环境质量等级为好、较好区域面积占比由40.14％上升至63.43％,集中分布在陕南山区及延安市;(2)生态环境质量从2000-2020年总体呈现"快速变好→缓慢转好"的演变趋势,生态环境质量改善区域面积远大于生态环境退化区域;(3)人口因子、土地因子和产业因子对生态环境的影响呈现明显的空间差异性,影响方式发生转变的因子有林地面积占比、农村居民点面积占比、单位面积化肥使用量和单位面积机械总动力.建议在未来发展过程中制定出分区域、科学合理的乡村振兴政策,以实现陕西省乡村发展与生态环境的协调发展.
明晰农村居民环境治理参与方式的选择偏好,对进一步提高农户环境治理参与率,加快生态宜居和美丽乡村建设具有重要意义.基于湖北省1 168份微观调研数据,采用双变量Probit模型实证方法分析资源禀赋、家乡认同与农户村域环境治理参与方式选择之间的内在作用关系.结果表明:(1)农户村域环境治理参与方式选择存在差异,10.70％的农户倾向于仅出钱参与村域环境治理,38.36％的农户倾向于仅出力参与,19.52％的农户倾向于既出钱又出力参与.(2)受教育水平、务工收入占比越高的农户越偏好于出钱参与村域环境治理;家庭总收入、务工收入占比越低,社会网络越宽泛的农户越偏好于出力参与;家庭总收入、社会信任和社会声望水平越高的农户,越偏好于又出钱又出力的方式参与.(3)家乡认同在家庭总收入影响农户"是否愿意出钱"和劳动力数量影响农户"是否愿意出力"参与村域环境治理过程中存在正向调节作用,即家乡认同在一定程度上能够推动有能力出钱或出力参与却未参与村域环境治理的农户群体参与.对此,从提高农户家庭资源禀赋水平、培育和加强农户家乡认同感、加快农村经济发展以及制定群体差异化治理策略等方面提出推动农户参与环境治理的政策建议.
This study aimed to evaluate the pollution characteristics and risks of phthalate esters (PAEs) in typical chemical industry parks in Jiangsu Province. Samples were collected of drinking water, surface water, raw water and effluent from sewage treatment plants, and soil and sediment from five chemical industry parks in Changzhou, Suzhou, Taizhou and Nantong in Jiangsu Province in December 2022. The concentrations of PAEs in the different samples were determined by gas chromatography-mass spectrometry. The main PAEs detected were bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), and di-n-octyl phthalate (DNOP). The total concentration ranges of PAEs in water, sediment, and soil were not from detected to 13 757 ng·L-1, 78.4 to 2 618 μg·kg-1, and 56.7 to 1 329 μg·kg-1, respectively. The average PAEs concentrations in water, sediment, and soil were 1 369 ng·L-1, 661 μg·kg-1, and 442 μg·kg-1, respectively. High concentrations of PAEs were detected in surface water and drinking water in Nantong and Taizhou, and in sewage treatment plant effluent in Taizhou. High concentrations of PAEs were also detected in soil and sediment in Nantong and Taizhou. The risk entropy method was used to assess the risk levels of the PAEs. The results show that PAEs in surface water, soil, and sediment in typical chemical parks in Jiangsu Province presented a moderate to high degree of risk. High risk was presented by PAEs in sewage treatment plants. A health risk evaluation show that the PAEs health risk entropy in drinking water and water sources around chemical industrial parks in Jiangsu Province ranged from 0 to 0.191 2. The PAEs in drinking water presented a moderate risk in Nantong and a low risk in other areas. Overall, samples from Nantong and Taizhou showed the highest levels of pollution and had risks that were above moderate levels; therefore, pollution in these areas should receive high attention. Further analysis is required to identify the sources of PAEs pollution in these areas so that effective measures can be taken to control excessive emission of such pollutants into the environment.
Scientific evaluation of the resource and environment carrying capacity for rural and township development is the basis and premise for rationally allocating the three functional spaces of "production-living-ecology", and promoting the rural and township coordinated development with resource and environmental protection. However, in terms of research on the assessment of resource and environment carrying capacity of rural and township development, due to the lack of systematic and logical self-consistent analysis framework and indicator system, the assessment and monitoring of resource and environment carrying capacity of rural and township development with regional differences, historical variability and system complexity are limited. In the process of implementing the strategy of rural revitalization and the land space planning, it is urgent to build an evaluation index system of resource and environment carrying capacity for the needs of rural and township development. Therefore, on the basis of summarizing the research results of rural and township development and resource and environment carrying capacity, the key concepts and the coordination relationship between rural and township development and resource and environment carrying capacity are explained, and the technical framework for evaluating resource and environment carrying capacity of rural and township development has been constructed. In addition, under the guidance of the principles of indicator system construction and indicator screening methods, a scientific, systematic and standardized indicator system was established for the background evaluation of resource and environment carrying capacity for rural and township development at macro scale, and for the calculation and coordination evaluation of the carrying capacity of resource and environment for rural and township development with different dominant function types at micro scale. The key indicator algorithms and the basis for the selection of main parameters are proposed. The research results are expected to provide theoretical and methodological basis for the assessment and management of regional resource and environment carrying capacity for rural and township development in China, and to provide scientific basis and technical support for promoting the coordinated rural and township development and resource and environment carrying capacity development in terms of territorial space division and classification.
The Yellow Sea Wetland Heritage Area is the first coastal wetland natural heritage in China. Under the background that the wetland habitat conservation becomes a focal point of development, the livelihoods of farmers in the vicinity of the heritage area face numerous challenges. Enhancing the livelihood resilience of these farmers is crucial for achieving wetland conservation and promoting collaborative development with neighboring communities. Taking the typical villages surrounding the Yellow Sea Wetland Heritage Area as a case for the study, an evaluation index system for farmers′ livelihood resilience based on three dimensions: buffering capacity, self-organization ability, and learning capacity was developed. The key influencing factors were also identified by the Obstacle Degree Model, and based on which the optimization path of farmers′ livelihood resilience was further put forward. The findings are as follows: (1) Overall, the livelihood resilience of farmers in the villages surrounding the Yellow Sea Wetland Heritage Area was relatively low. Buffering capacity was the highest, while self-organization ability and learning capacity were comparatively lower, with significant variations in livelihood resilience among different types of households. (2) Housing conditions, public service coverage, per capita agricultural area, family livelihood diversity, financial support and risk perception ability were the common influencing factors of farmers′ livelihood resilience across various household types. (3) A systematic approach should be adopted to construct a pathway for enhancing livelihood resilience, which should be guided by the principles of "classification optimization, multi-sector collaboration, policy support, and farmer self-awareness". The research results can serve as valuable decision-making reference for advancing harmonious co-existence between humans and nature in the Yellow Sea Wetland Heritage Area and promoting high-quality rural development.
There are a number of small and medium-sized rivers throughout China, which are the closest to humans. But they are also affected by man-made transformation and production and life activities and show more obvious ecological degradation. Taking the Xuchang section of the Qingyi River as the study area, a mass-balance food web model was established with "Ecopath with Ecosim" according to the data of aquatic organisms collected in the summer and autumn of 2021. The achieved results reveal that the Qingyi River ecosystem mainly consists of five integrated nutrient levels (1.00-3.29), and due to the low transfer efficiency of trophic levels I and II, the energy flow to the higher nutrient level was seriously hindered, and the conversion efficiency of the whole system was only 1.08% and 1.82%. The mixed trophic impacts did not alter in summer and autumn, and predators except Culter alburnus exhibited a strong inhibitory effect on the bait organisms. A comprehensive analysis of multiple indicators, including parameters close to maturity, resilience and stability of the system, indicate that the total flow rates of the Qingyi River ecosystem were 2 571.06 and 1 472.58 t·km-2 in summer and autumn, respectively, and the size of the ecosystem in summer is greater than that in autumn and Finn′s cycling index (FCI) and Finn′s mean path length (FML) also revealed that the ecosystem maturity and stability in summer were superior to those in autumn. Finally, according to the food web model, three key functional groups at various nutrient levels in the Qingyi River ecosystem have been selected as phytoplanktons, molluscs, and Culter albus, while maintaining the appropriate requirements of key functional habitats and growth habits, the pertinent suggestions for restoring the ecosystem, such as limiting the growth of dominant phytoplankton species, increasing mollusk predator pressure, and restoring the Culter alburnus population are presented. The findings of this study could provide decision-making basis and scientific support for the ecological restoration of the Qingyi River and similar rivers.
The quality of the ecological environment often determines whether human society can achieve sustainable development or not. It is of practical importance to explore how and to what extent rural development affects the ecological environment to achieve regional rural revitalization and sustainable development. Taking Shaanxi Province as the research object and counties as the research unit, the remote sensing ecological index (RSEI) for a long time series was used to characterize the spatial and temporal changes and changing trends in ecological environment quality in the province. The factors influencing the quality and spatial differences in the ecological environment were explored with the help of spatial and temporal geographical weighted regression models. The study show that: (1) the overall changing trend of ecological environment quality from 2000 to 2020 was positive, with the RSEI value increasing from 0.483 3 in 2000 to 0.651 2 in 2020. The ecological environment quality grades were good and relatively good, with the percentage of areas increasing from 40.14% to 63.43%, which are concentrated in the mountainous areas of southern Shaanxi Province and Yan′an City. (2) The overall trend was a "rapid improvement → slow change for the better" from 2000 to 2020. The areas with an improved ecological environment are much larger than those with a degraded ecological environment. (3) The influence of the population, land, and industry factors on the ecological environment showed an obvious spatial variability. The main factors that affecting the influence mode were the proportion of forest land area, the proportion of rural settlement area, fertilizer use per unit area, and total mechanical power per unit area. It is suggested that a sub-regional, scientific, and rational rural revitalization policy should be formulated for the future development process to coordinate rural development and the ecological environment in Shaanxi Province.
The objective of this study is to analyze the spatial and temporal patterns of agricultural inputs in Jiangxi Province over a 30-year period and investigate their correlation with adjustments in planting structure. This research aims to establish a theoretical foundation for enhancing the quality and efficiency of agricultural production and mitigating non-point source pollution in the agricultural sector. The analysis was conducted using ArcGIS, the center of gravity model, and the structural equilibrium degree approach. Linear regression analysis was employed to examine the correlation between changes in agricultural planting structure and agricultural inputs. The findings indicate that: (1) The input of chemical fertilizers, pesticides and agricultural films in Jiangxi Province demonstrated an overall trend of increasing and then decreasing from 1992 to 2019. However, the input of chemical fertilizers and pesticides on farmland in Jiangxi Province has been significantly reduced since the implementation of a series of policies aimed at reducing the consumption of pesticides and fertilizers and improving their efficiency in 2015, and the input of chemical fertilizers and pesticides in 2020 decreased by 24.5% and 43.9%, respectively compared with that in 2015, but the slowing trend of agricultural film input in recent years is not obvious; (2) There is a clear pattern of spatial clustering in the intensity of fertilizer application throughout Jiangxi Province, with a general trend of aggregated distribution along Poyang Lake Basin, Fuhe River Basin and Ganjiang River Basin; the degree of pesticide input is generally higher in the northeast of Jiangxi Province; and plastic agricultural film usage was generally increasing and particularly prevalent in the eastern and southern areas of the province; (3) The restructuring of the plantation industry in Jiangxi Province is evident in the significant rise of orchard plantation area, which increased from 106.7 thousand hectares in 1992 to 427.8 thousand hectares in 2020, resulting in an increase in proportion from 2.1% to 7.6%. A more pronounced correlation exists between the expansion of orchard planting area and the utilization of agricultural films, in comparison to the application of chemical fertilizers and pesticides. This observation suggests a strong correlation between the expansion of fruit cultivation areas in Jiangxi Province and the concurrent rise in the adoption of agricultural films.
It is important to clarify the preferences of rural residents in their choice of environmental management methods, because it can further increase the participation rate of farmer households in environmental management and to accelerate the construction of ecologically pleasant and beautiful villages. Based on 1 168 microscopic survey data in Hubei Province, a bivariate probit model was used to empirically analyse the intrinsic role of the relationship between resource endowment, hometown identity and farmers′ choice of participation methods in village environmental governance. The results show that there were differences in farmers′ preferences for participation in village environmental governance, with 10.70% of the farmers preferring to participate with money, 38.36% preferring to participate with contributing efforts, and 19.52% preferring to participate with both money and contributing efforts. The higher the level of education and income from work, the more the farmers prefer to participate with money; the lower the proportion of total household income and income from work, and the wider the social network, the more the farmers prefer to participate with contributing efforts; the higher the level of total household income, social trust and social prestige, the more the farmers prefer to participate with both money and contributing efforts. There is a positive moderating effect of hometown identity in the process of total household income influencing farmers′ "willingness to pay" and labour force influencing farmers′ "willingness to contribute effort" to participate in village environmental management, and hometown identity can promote the participation of the groups of farmers who have the ability to contribute money or efforts to participate but have not yet done so in village environmental governance. Accordingly, policy recommendations are proposed to promote farmers′ participation in environmental governance. These include improving their household resource endowment, cultivating and strengthening their sense of hometown identity, accelerating rural economic development and developing group differentiated governance strategies.
Rainfall erosivity is an important index used to characterize the intensity of rainfall erosion, which is of great significance to the research on potential risk of soil erosion in the study area and for model predictions. To analyze the spatiotemporal variation trend of rainfall erosivity in the Nandu River Basin, based on the daily rainfall erosivity model, daily rainfall data recorded at 13 meteorological stations in the basin and its surrounding areas from 1971 to 2020 were used to systematically study the rainfall erosivity at different spatiotemporal scales. The research methods included the application of the Mann-Kendall nonparametric trend/mutation test, wavelet analysis, and inverse distance weighted interpolation to determine the spatiotemporal variation trends of rainfall erosivity. The results show that the average annual rainfall erosivity in the Nandu River Basin from 1971 to 2020 ranged from 11 841.33 to 23 692.14 MJ·mm·hm-2·h-1, with an average value of 16 497.67 MJ·mm·hm-2·h-1, and the interannual variations reflect four stages, with an overall trend of rising fluctuations. The results indicate that the potential risk of soil erosion increased gradually over the study period. The annual rainfall erosivity has a change cycle of 30 years, and no obvious abrupt change occurred during the study period. Affected by the monsoon climate, latitude, elevation, spatiotemporal distribution of rainfall erosivity and erosive rainfall distribution, the rainfall erosion force was mainly concentrated in the period from July to September, accounting for 51.26% of the annual rainfall erosivity. Therefore, it is necessary to strengthen the prevention and control of soil erosion in this period, especially when rainfall erosivity peaks in August. Rainfall erosivity showed upward trends in summer, autumn and winter, but in spring, rainfall erosivity showed a downward trend. The spatial distribution of the annual rainfall erosivity decreased gradually from south to north. The variation coefficients of the meteorological stations ranged from 0.24 to 0.43, showing high regional variability. The variation coefficient of the northern region was relatively large, while that of the southern region was relatively small, and the overall trend gradually decreased from north to south. Rainfall erosivity in the Nandu River Basin was significantly and positively correlated with the erosive rainfall and elevation; and the erosive rainfall effect passed the significance test at 0.01, while the elevation effect passed the significance test at 0.05. Certain correlations were found between rainfall erosivity and both latitude and longitude, with correlation coefficients of 0.76 and 0.42, respectively, both passing the 0.01 significance test. This study can provide a reference for the prediction and control of soil and water losses and the envirommental protection in the Nandu River Basin and related typical erosion areas.
According to the theory of collaborative governance, an indicator system was constructed to measure the collaborative degree of multi-agent governance of tea farmers′ green production behavior. A sample dataset of 872 cases from Anxi County, Wuyishan City and Fuding City, Fujian Province, were used to evaluate the collaborative effect of multi-agent collaborative governance of tea farmers′ green production behavior and empirically analyze its influencing factors, where a collaborative degree model of compound system and a confirmatory factor analysis model were employed. Results show that: (1) The order degree of each subsystem in the multi-agent collaborative governance system of green production behavior among tea farmers in the research area is low and imbalance. (2) The multi-agent collaborative governance synergy degree of green production behavior among tea farmers in Anxi County, Wuyishan City and Fuding City is in the general collaborative form, and has not reached the optimal collaborative state. (3) The five dimensions of measurement indicators, namely, governance agent participation, governance object development, governance mechanism assurance, governance goal orientation and governance environment promotion, have a significant positive impact on the multi-agent collaborative governance effect of green production behavior among tea farmers, while variations exist among the five dimensions. Based on these findings, the following policy recommendations are put forward: harness the collaborative role of various governance agent, enhance the participation level of governance in the governance of green production behavior among tea farmers, improve the realization mechanism of multi-agent collaborative governance and ensure the efficient coordination of governance of green production behavior among tea farmers, improve the system structure of multi-agent collaborative governance and enhance the function of governance elements of green production behavior among tea farmers.
Rural leisure tourism sewage has the characteristics of discontinuous discharge and large fluctuation with time, which poses a great challenge to the management and operation of decentralized sewage treatment equipment. In this study, a two-stage AO-MBR setup is designed, which uses simulated sewage as the inlet water. Through the operation mode of shutdown/restart in different time periods, the impact of shutdown on the biochemical performance and recovery of the treatment process was explored. The results show that the shutdown operation had a significant impact on the biochemical treatment efficiency of the experimental setup, and the decline degree of biochemical treatment efficiency and the recovery time had a significant correlation with the shutdown time of the setup. As the shutdown time was extended from 1 d to 8 d, the COD removal efficiency could be decreased from 90% to 80%, and the longest recovery time was up to 5 d; the removal efficiency of ammonia nitrogen could be decreased from 90% to around 70%, and the longest recovery time was up to 5 d; the total nitrogen removal efficiency could be decreased from 48% to 34%, and the longest recovery time of the system required 5 d too. From the perspective of sludge activity, with the extension of shutdown time, the sludge activity indexes such as SOUR, dehydrogenase activity and SATP decreased accordingly. Through the method of microbial sequencing, it was also found that the microbial population changed greatly before and after the shutdown. From the perspective of phylum level, the proportion of heterotrophic bacteria of Proteobacteria decreased significantly after the shutdown, and the proportion of anaerobic bacteria such as Bacteroidea increased. From the perspective of genus classification, the number of traditional nitrifying bacteria decreased, but the number of bacteria with synchronous nitrification and denitrification showed an upward trend. For the wastewater treatment facilities that have to be shut down, an aeration operation with less oxygen is a feasible alternative way to maintain the activity of the sludge.
Biochar, as a green and sustainable soil stabilization agent, has been widely used in the remediation of heavy metals (HMs) contaminated soil. The migration and transformation of HMs are highly affected by the physicochemical characteristics of soil. Under the change of redox process caused by flooding-drainage intercropping in paddy soils, the fluctuation of physicochemical characteristics of soil will threaten the long-term safety of land utilization. Here, a mulberry stem was selected as feedstock to produce biochar by the in situ "water-fire coupled" method. The derived biochar was noted as SG-BC. The capability and mechanisms of SG-BC adsorbing Cd, Zn, and Pb were investigated. The results show that the maximum adsorption capacities for Pb, Zn, and Cd of SG-BC were 214.39, 41.10, and 25.75 mg·g-1, respectively. The mechanisms were clarified as surface complexation, precipitation, and cation-π interactions. In addition, a soil microcosm incubation experiment was conducted under redox dynamic conditions to explore the impact of SG-BC on the soil Eh and pH, and the immobilization of HMs. The results show that compared to the control, the addition of SG-BC could increase soil pH, slightly decrease soil Eh, and inhibit the soil HMs release at various degrees during flooding, and the inhibition was more strong during drainage, especially in the early stage; SG-BC decreased the concentrations of Pb, Zn, and Cd in soil solution by 96.69%, 80.77%, and 78.41%, respectively. These results indicate that SG-BC is effective to immobilize Cd, Zn, and Pb in the soil with dynamic redox processes. This study provides theoretical basis for applying biochar to remediate HMs contaminated agricultural soil.
The ecological civilization demonstration area includes the national ecological civilization construction demonstration area and the "Lucid Waters and Lush Mountains Are Invaluable Assets (as Two Mountains)" practice and innovation base, which focuses on the developing of an ecological economic system with industrial ecology and ecological industrialization as the mainstay, explores the path and model of realization of ecological product value, especially in rapidly urbanized areas. Taking 77 ecological civilization construction demonstration areas and 22 "Two Mountains" practice and innovation bases in the Yangtze River Delta (YRD) as the objects, the author utilized land use products, VIIRS, and MODIS data to construct remote sensing ecological index (RSEI) and compounded night light index (CNLI) to represent the ecological environment quality and urbanization level, respectively, and explored the level and spatiotemporal variability of ecological civilization demonstration construction in the YRD by using spatial superposition analysis and coupling coordination degree model. The results show as follow: (1) The distribution of ecological civilization demonstration area in the YRD is uneven, among which, the distribution of ecological civilization construction demonstration areas is more concentrated and dominated by plain terrain, while the "Two Mountains" practice and innovation bases are more dispersed and dominated by mountainous terrain. (2) The ecological land area of the ecological civilization demonstration area exceeds 70% and has a good environment foundation, among which the RSEI index of the "Two Mountains" practice and innovation base is higher than that of the ecological civilization construction demonstration area, and the ecological environment quality is superior, but it is more fragile. (3) The CNLI and its growth rate of the ecological civilization construction demonstration areas are higher than those of the "Two Mountains" practice and innovation bases, which has a higher urbanization level and development speed. (4) From 2017 to 2021, the coupling coordination degree between ecological environment quality and urbanization level of the ecological civilization construction demonstration areas and "Two Mountains" practice and innovation base showed an increasing trend, with an average increase of 10.55% and 8.90%, respectively, indicating that the ecological civilization construction has achieved certain results, with the highest coupling coordination degree at the junction of Jiangsu and Zhejiang Provinces.
The study aims to investigate the effects of application of the modified lignite on the distribution of typical northern calcareous soil aggregates and distribution of heavy metal cadmium (Cd) in different particle-size aggregates. Different types of modified lignite materials were introduced into soils contaminated with Cd, followed by a 150-day incubation period. Soil aggregates at different grain levels were extracted by dry sieving and wet sieving, and the contents of calcareous soil aggregates and heavy metal cadmium and their stability were investigated in response to different modified lignite application amounts (0, 1%, 3%, and 5%), and the distribution of different Cd forms in aggregates. The distribution of various forms of Cd in soil aggregates was analyzed across different particle size fractions. The results obtained from dry and wet sieving demonstrated a gradual increase in the content of water-stable aggregates in the soil due to the application of modified lignite. More specifically, the content of water-stable aggregates exhibited an increase ranging from 0.9% to 25.2%, 5.5% to 24.5%, 12.1% to 46.5%, 98.4% to 156.1%, and 127.8% to 174.4% under treatments of lignite (LI), lignite-based humic acid (LIH), demineralized lignite (LID), humic acid resin (HAR), and humic acid-grafted copolymer (HAG), respectively. The content of water-stable agglomerates, average weight diameter, geometric mean diameter and particle size greater than 0.25 mm agglomerates of the soil increased significantly after the application of amendment. Among the different treatments, the coefficient of enrichment of Cd in coarse sand-sized aggregates (r1) and fine sand-sized microaggregates (r3) exhibited higher enrichment factors, while the coefficient of enrichment of water-stable agglomerates at the grain level (r2) was the smallest. In conclusion, the application of modified materials can not only effectively increase the water-stable aggregates of soil, but also effectively enrich the ion exchange state, carbonate binding state and iron and manganese oxidation state in the aggregates larger than 0.25 mm and the water-stable micro-aggregates smaller than or equal to 0.053 mm. The strong organic, weak organic and residual Cd are enriched in the water-stable microaggregates smaller than or equal to 0.053 mm. Particularly, lignite-based humic acid and demineralized lignite exhibited the most favorable effects on the formation of water-stable aggregates and the enrichment of Cd.
