The sustainable construction of rural energy structure is an important part of optimizing the existing energy consumption structure in rural areas, implementing joint air pollution prevention and control, and achieving carbon emission reduction goals. Using a sample of 1 113 rural households from the 2018 "Rural Energy, Population Transfer and Welfare" survey, Probit regression analysis and Tobit regression models were used to analyze the impact of farm households' livelihood capital on their consumption choices of combined energy. The results show that (1) The human capital significantly promotes the consumption of commodity energy and clean energy. (2) The natural capital is significantly and positively correlated with the consumption of non-commodity energy and conventional energy, and the opposite with the consumption of new energy and clean energy. (3) The physical capital is significantly and positively correlated with the consumption of commodity energy, and the opposite with the consumption of conventional energy. The findings reveal that livelihood capital has a significant impact on the choice of combined energy consumption of farmers, and the optimization of farmers' human capital and the accumulation of physical and financial capital make it easier for farmers to form cleaner and lower carbon combined energy consumption habits. This paper proposes to optimize the stock of livelihood funds and raise awareness of energy conservation in rural areas while improving related supporting facilities and increasing farmers' willingness to protect the environment, so as to promote the prcesses of green and low carbon energy consumption in rural areas.

In order to explore the relationship between land use and carbon storage, and to improve the regional carbon sequestration capacity, Huangpi District, Wuhan, a metropolitan suburb was taken as the research object. The Markov-FLUS coupling model was used to simulate the land use change under the natural development scenario, the economic priority development scenario and the comprehensive development scenario, and the InVEST model was applied to quantitatively study the effect of land use change on carbon storage under different scenarios. The results show that, from 2000 to 2020, the cultivated land and forest land in Huangpi District decreased by 63.916 and 3.549 km², respectively, while the construction land and water area increased by 63.826 and 5.406 km², respectively. The regional land use changes drastically, and the total area of transferred land is 76.041 km², of which the transferred out area of cultivated land is 64.486 km². From 2000 to 2020 (especially from 2010 to 2015), the carbon storage in Huangpi District decreased by 4.27 Tg, but the overall ecological background was good, and the average land carbon density was high. The conversion of cultivated land to construction land under the three scenarios is still the main reason for the reduction of regional carbon storage, but the reduction is the smallest under the comprehensive development scenario. The Moran index of land use intensity and carbon storage at a scale of 1 km×1 km showed a significant negative correlation, and the local autocorrelation showed that the two synergies accounted for the largest proportion under the comprehensive development scenario. These findings indicate that the suburbs of the metropolis should adhere to the bottom line of ecological security in the future development and construction process, so as to slow down the rapid loss of carbon storage and take the path of high-quality development.

Identifying the urban-rural gradient of supply-demand matching of ecosystem services is the premise of overall promotion of urban-rural ecological construction, and is of great significance for the coordinated optimization of urban-rural residents' well-being. Taking the main area of Nanchang city as an example, the paper evaluated the spatial characteristics of supply and demand by using the relative index of ecosystem services supply and demand, classified the supply and demand status by using the method of natural discontinuity, and stacked them yielding a variety of supply and demand matching types. The urban-rural gradient types were identified by combining landscape structure analysis and spatial location. The results show that: The areas with high and medium demand for ecosystem servicesare mainly located in urban area, while the areas with high and medium supply are mainly located in rural area. There are 6 matching types of supply-demand with different landscape structure and spatial location. There are six types of urban-rural gradient in the study area: urban inner circle, urban middle circle, suburban, agricultural, semi-ecological and ecological villages. There are four types of supply-demand matching types of ecosystem services in the suburban and three types of supply-demand matching types in the rural area. Urban-rural gradient of supply-demand matching of ecosystem services are influenced by distance gradient and landscape gradient, and the spatial structure show a circular layer, which is divided into four layers. In general, from the urban to the rural end, demand gradually decreases and supply gradually increases. The research proposes different corresponding regulatory strategies and specific measures for each gradient. Based on the perspective of gradient integration, the ecological integration path is proposed to promote the complementarity and flow of urban-rural supply and demand. The results provide useful references for urban-rural ecosystem service management and regional integrated development.

Although high intensity coal development promotes the rapid economic development of coal resource-based cities, it also causes severe damage to regional ecosystem services. Exploring the coupling relationship between coal development intensity and ecosystem services and its driving mechanism is vital for the coordinated development of the economy and ecological environment of coal resource-based cities in China. In this study, Huainan City, a typical coal resource-based city, was chosen as the study area. The temporal change law and primary driving factors of the coupling degree between coal development intensity and ecosystem services in Huainan City from 2005 to 2018 were determined using the capacity coupling and grey correlation models, based on the construction of its coal development intensity index system and ecosystem services. The results show that, the intensity of coal development in Huainan gradually transited from the medium- to low-intensity development level, and the ecosystem service showed an "L-shaped" downward trend. The coupling degree between them increased continuously from 2005 to 2010, but showed a downward trend after 2011. The primary internal driving factors of the coupling relationship between coal development intensity and ecosystem services comprised the proportion of coal mining land subsidence area and food production services, and their correlation with the coupling degree was 0.728 4 and 0.583 1, respectively. The primary external driving factors of the coupling relationship between coal development intensity and ecosystem services were environmental governance level and coal industry dependence, and their correlation with the coupling degree was 0.949 2 and 0.848 3, respectively. This study provides a scientific basis for the coordinated development of coal development intensity and ecosystem services in coal resource-based cities.

The nutrient release in the sediments of Xishan Island became the restriction on water quality improvement in Taihu Lake. Little efforts has been made to study the pollution characteristics of nitrogen and phosphorus in sediments and their responding to the overlying waters in Xishan Island. Fifteen representative sections were chosen and sampled in the autumn of 2020 (CZ1-CZ6, CX1-CX3, CX1-CX6), and the concentrations of nitrogen and phosphorus in sediments were determined. The adsorption-desorption experiments were developed under different initial ammonia nitrogen (NH₄⁺-N) and phosphate (PO₄^3--P) concentrations. The responses to the overlying water were studied to determine the dredged points. The results indicat that the average concentrations of total nitrogen and total phosphorus were 8.97 and 2.90 g·kg^-1, respectively. The average concentrations of reactive nitrogen and phosphorus were 3.77 and 1.29 g·kg^-1, respectively, which showed that the sediments in Xishan Island got higher risk of potential nitrogen and phosphorus releases. According to the results of simulation experiments, the sediments in seven points were dominated by NH₄⁺-N desorption, and the sediments in nine points were dominated by PO₄^3--P desorption. In order to maintain the stability of the water environment of Taihu Lake, the exterior pollution should be merely controlled for CZ1 and CZ2. The sediment in CZ4 needs to be dredged and measures should be taken to improve the conditions of waters and sediments in other points.

Yongqing County is the largest "Pollution-Free" vegetable planting base in the Beijing-Tianjin-Hebei region, China. The vast majority of irrigation water and some domestic water is taken from groundwater in Yongqing. In order to comprehensively evaluate the content of heavy metals in groundwater and the possible health risks, 370 groundwater samples were systematically collected throughout the county, and seven heavy metal elements including Cu, Pb, Zn, Cd, Ni, Hg and As were analyzed. It is found that the content of Pb, Cd, Ni and As in some groundwater samples exceeded the water quality standard of class Ⅲ (GB/T 14848-2017), and the content of Pb, Cd and Ni in some samples were higher than the water quality standard of farmland irrigation (GB 5084-2021). The sampling points with high heavy metal contents are mainly located in the central and southern parts of the study area. According to the principal component analysis, As and Cd in groundwater are mainly related to agricultural production, while Cu, Zn, Ni and Pb are mostly from transportation and agricultural production, and Hg is mainly affected by natural background. The health risks caused by carcinogenic heavy metals (Cd and As) are higher than those caused by non-carcinogenic heavy metals (Cu, Pb, Zn, Ni and Hg). Cd and As are the main heavy metals that cause health risks, accounted for 79.24% and 20.66% of the total health risk, respectively. The health risk value caused by heavy metals in groundwater exceeds the maximum acceptable level. Therefore, the groundwater safety in the study area should be reasonably planned, and effective measures should be taken to reduce the health risks caused by heavy metals in groundwater.

Environmental protection has always been centered on the using of lake sediment as a resource. The sediment collected from Hulun Lake was used as the main substrate to demonstrate the effectiveness and efficiency of lake sediment resource utilization in ecological restoration, and the planting substrate was created by combining cow dung, sheep dung, and straw. The experiment included seven treatments: CK, TN1, TN2, TN3, TY4, TY5, and TY6. Physical properties such as germination rate and survival rate of forage, plant height, average root length, and chemical properties such as organic matter, nutrient content, and pH of the soil were examined to determine the impact of planting substrates on the growth and development of steppe forage. The results show that TN3 (sediment∶cow dung∶straw=2∶3.25∶2) and TY6 (sediment∶sheep dung∶straw=2∶3.25∶2) treatments had the best effects on forage growth, and that Agropyron mongolicum grew much effectively than Leymus chinensis. Leymus chinensis had 19.00% and 28.00% germination rates in TN3 and TY6, respectively, and Agropyron mongolicum had 73.00% and 72.00% germination rates in TN3 and TY6, respectively. Adding sheep dung planting base at the same proportion is more beneficial to the growth of forage than the other treatments. As for the other physical property indexes of forage and chemical property indexes of forage and planting substrates, TN3 and TY6 are higher than the other treatments with the same raw material. This indicates that the higher the content of sediment and straw in the planting substrates, the better the forage growth. The results of this research can provide technical support for the utilization of Hulun Lake's sediment resources and the managment of sandy meadows.

Pilot area of Shennongjia National Park (SNP) contains important habitat of Asiatic black bear (Ursus thibetanus) in central China, however, there is a lack of research on the activity rhythm of this species in SNP, which is conducive for managers to make better management plan for conserving the species. Occurrence data of Asiatic black bear were collected from 772 camera trapping sites from 2018 to 2020 with 62 575 camera trapping nights. Date and time of photographs of Asiatic black bear were extracted to assess their activity rhythm. The chi-square test and one-way ANOVA test were used to analyze the behavior of black bear at different elevations and vertical migration in different seasons. Below are the research results: (1) The annual activity rhythm of Asiatic black bears in SNP is unimodal, with the highest activity intensity occurring in summer and autumn. The hibernation period of black bear lasts from late December to mid-April of the next year for about 3 and a half months. (2) Daily activity rhythm of Asiatic black bear in SNP was bimodal, and the intensity of diurnal activity was higher, showing obvious diurnal pattern. (3) Asiatic black bear of SNP was most active between the altitude from >1 000 to 2 600 m. (4) There were significant differences in the range of elevations for the activity of Asiatic black bear in SNP in different seasons, which showed obvious vertical migration behavior of the species. (5) The lowest photograph rate of Asiatic black bear in SNP occurred between the altitude of >1 600-1 800 m, as the length of highway and the number of settlements in this elevation section ranked the second and first in SNP, respectively, indicating that human activities had a great influence on Asiatic black bear activities. The findings on the activity rhythm of the Asiatic black bears will provide important basic data and scientific support for the conservation and management of Asiatic black bear population and mitigation of human-bear conflict in SNP.

To assess the health status of aqua-system of Cao'e River, fish resources in nine sampling points in the main stream and tributaries of Cao'e River were investigated from 2016 to 2018, and the fish-based index of biotic integrity (F-IBI) was established. A total number of 17 116 individuals of fishes were collected, which belonged to 12 orders, 25 families, 69 genera and 107 species. Twenty-three candidate indices in five properties, including species composition and richness, nutritional structure, environmental tolerance, reproductive colocation group, fish quantity and health status, were proposed to develop the F-IBI. The results of data analysis show that four indices, i.e. species number of Cypriniformes (M3), ratio of species number in middle and lower layer (M9), ratio of sensitive fish individuals (M15) and ratio of species number spawned eggs in Mollusca (M19), were screened out as the core indices. Meanwhile, the scoring standard with diagnostic significance for fish biotic integrity was established and successfully used to evaluate the health statuses of nine sampling points in Cao'e River basin. The results show that the health statuses of the nine sampling points along the main stream were in "very poor-poor" to "normal" levels, while those of the tributaries were in "normal" to "good" levels, indicating that the health statuses of the tributaries were better that those of the main stream. The results suggest that, water pollution, obstruction of water conservancy projects and overfishing might be the important factors causing the lower health statuses of the main stream of Cao'e River, and water conservancy projects might be the important factor causing the lower health status of the main tributary Changzhao.

Potassium ferrate has been widely used as a water quality improver in aquatic industry, but the safety of its use and the reference value of freshwater aquaculture organisms have been unclear. In this study, the species sensitivity distribution (SSD) method was used to determine the reference value of potassium ferrate and evaluate the ecological risk of potassium ferrate to freshwater aquaculture organisms. The acute toxicity of potassium ferrate to 14 freshwater aquatic organisms was obtained by acute toxicity test. Six fitting models were selected to fit the toxicity data, and the regression coefficient and residual sum of squares were compared to determine the model with the best goodness of fit. The HC₅ threshold (hazardous concentration for 5% of the species) of potassium ferrate for different species and the reference value of potassium ferrate for freshwater aquaculture organisms and freshwater aquatic organism were derived. The potentially affected fraction (PAF) of potassium ferrate on freshwater aquaculture organisms was calculated by using the SSD model. The results show that: (1) The sigmoid model had the best goodness of fit, and the basic safety value of potassium ferrate for all freshwater aquatic organisms was 6.82 mg·L^-1, and for freshwater aquaculture organisms was 9.53 mg·L^-1. (2) The PAF value corresponding to the concentration value of potassium ferrate used in daily aquaculture is 0, indicating low ecological risk. The results can provide scientific basis and theoretical guidance for the formulation of reference value of potassium ferrate in freshwater aquaculture organisms and the safe use of potassium ferrate.

Ultraviolet/visible spectroscopy and fluorescence spectroscopy were used to describe the spectral characteristics of soil dissolved organic matter (DOM) in four typical coastal wetlands i.e. Spartina anglica, Suaeda glauca, Phragmites australis and Robinia pseudoacacia wetlands in Yancheng, China. The results show that the aromatic index (SUVA₂₅₄) of soil DOM under Robinia pseudoacacia community was significantly higher than that of other wetlands. Except for Suaeda Glauca wetland, the SUVA₂₅₄ values of DOM in the topsoil of all other wetlands were significantly higher than that in the soil of depth. The fluorescence efficiency (FE) of soil DOM was significantly different between soil layers and increased with soil depth, and also significant negative correlated with SUVA₂₅₄. In the >25-40 cm soil depth, the FE value of DOM in Phragmites Australis wetland was significantly higher than that in other wetlands. The FI values of soil DOM under the four vegetation communities were all less than 1.40, which indicates that the terrestrial input of DOM played a dominant role. The humification index (HIX_syn) value of soil DOM was higher in Spartina Anglica wetland, while the HIX_syn of Robinia pseudoacacia wetland showed significant differences between soil layers. Moreover, the SUVA₂₅₄ values of DOM were positively correlated with soil organic carbon, dissolved organic carbon and C/N ratio, respectively. Our findings indicate that the aromatization and humification of DOM were higher in the topsoil of Robinia pseudoacacia and Spartina Anglica wetlands, respectively, and suggest that there are more complex compounds in the topsoil in these wetlands.

The objective of this study is to explore the effect of applying zinc (Zn) and silicon (Si) as foliar sprays on the accumulation of cadmium (Cd) in lettuce plants growing in lightly Cd-polluted soil. The Cd contents in various organs of lettuce and its subcellular distribution patterns were determined, and the morphological responses of lettuce plants were analyzed. The results of the study show that foliar spraying with Zn and Si reduced the Cd contents in edible parts of lettuce plants by 10.51%-45.09%. The Cd content in the edible parts of lettuce treated with Si was lower than the limit specified in the national food safety standard. The concentration of Zn/Si was the main factor affecting the accumulation of Cd in lettuce, with higher concentrations having a stronger effect to reduce Cd accumulation. Foliar spraying with Si or Zn promoted the conversion of Cd from an active to an inactive state, significantly increased the proportion of sodium chloride-extracted Cd in various organs of lettuce, and reduced the proportion of active Cd in the roots, stems, and leaves by 75.83%, 60.38%, and 80.03%, respectively. Foliar spraying with Si or Zn significantly reduced the distribution of Cd in root organelles, and reduced the distribution of Cd in stem and leaf organelles by more than 30%. Foliar spraying with Zn and Si could reduce the activity of the heavy metal Cd in lettuce roots and prevent and control Cd accumulation in the edible parts of lettuce plants.

Development of high-performance adsorption materials and effective treatment of ammonia nitrogen in acid wastewater is crucial to the eco-environment conservation of ion-absorbed rare earth mine area. The NaCl modified natural zeolite (NZ-NaCl) was prepared by impregnation method, and the effects of modified conditions on adsorption of ammonia nitrogen were investigated. The structural characteristics of zeolite before and after modification were determined by BET, SEM-EDS, XRF and FTIR. The results show that NaCl modified zeolite improved the adsorption performance of zeolite for ammonia nitrogen. The zeolite modified by 1 mol·L^-1 NaCl at room temperature and the solid to liquid ratio of 1∶5, the equilibrium adsorption capacity of NZ-NaCl reached to 11.12 mg·g^-1, which was 2.62 times that of natural zeolite. In the actual application of wastewater in ion-absorbed rare earth mine area, the removal rates of ammonia nitrogen, rare earth elements, Pb and Cd were 100%, 96.2%, 99.8% and 47.0%, respectively, when the dosage of NZ-NaCl was 0.02 g·mL^-1. The improvement of adsorption capacity was related to the increase in the specific surface area, exposure of internal lamellar structure and pores, and the occurrence of columnar nanofibers. The modification reduced the steric hindrance of ammonia nitrogen adsorption, accelerated the internal diffusion, released more NH₄⁺ adsorption sites, due to the replacement of other cations in internal zeolite by sodium, and then improved the adsorption performance of NZ-NaCl for ammonia nitrogen. In addition, NZ-NaCl had more binding forms to removal ammonia nitrogen by adsorption than that of natural zeolite. The results could be an important guideline to the further development of high-performance adsorption materials and to the effective removal of ammonia nitrogen in acid wastewater of ion-absorbed rare earth mine area.

In order to remove cadmium (Cd) from contaminated soil, magnetic nano hydroxyapatite (nHAP@Fe₃O₄) was synthesized by co-precipitation method under the soil water ratio of 1∶1 precursor. 0, 0.1%, 5%, 1.0% and 3.0% nHAP@Fe₃O₄ were then added to soil, respectively. After 21, 30 and 45 days of remediation, magnetic separation was used to separate nHAP@Fe₃O₄ from soil, and the removal rates of Cd in soil, the recovery effect of materials and the changes of soil physical and chemical properties after remediation were then investigated. The results show that the average Cd removal rate and the material (nHAP@Fe₃O₄) recovery rate of heavy polluted paddy soil (containing 2.510 mg·kg^-1 of Cd) with the addition of 1% nHAP@Fe₃O₄ were 16.45% and 85.33%, respectively. The nHAP@Fe₃O₄ can significantly reduce the exchangeable and carbonate bound forms of soil Cd, and promote its transformation to a more stable form. After the remediation by nHAP@Fe₃O₄, the pH of the soil was increased, while the CEC decreased and the pore size between soil particles was increased. The removal of Cd from soil could be realized by using magnetic method to separate nHAP@Fe₃O₄ and adsorb Cd from the soil, which has little effect on soil physico-chemical properties. It is suitable for the remediation of severely polluted agicultural soil.

The bacterial diversity and community structure of soil alkaline phosphatase genes in different land use types were studied to provide a reference for the impact mechanism of the loss of bacterial diversity in ionic rare earth mining areas. Taking the abandoned farmland in the mining area (mine tail water irrigated) as the control, soil samples of parly tail water irrigated farmland and spring water irrigated vegetables, Camellia oleifera and Citrus reticulata were collected. In order to explore soil acidification and bacterial response of phoD gene. High-throughput sequencing technology was used to analyze the bacterial community characteristics of the phoD gene. The chemical properties of the soil were measured. The results show that there are significant differences in pH among different land use types. Tail water irrigation exacerbates soil acidification. The OTUs and Shannon index of phoD gene bacteria were in the order of vegetables land > Camellia oleifera land > Citrus reticulata Barco land > farmland > abandoned farmland. There were significant differences in phoD bacterial community structure among different land types. The dominant phyla are Proteobacteria, Planctomycetes and Acidobacteria. The dominant bacteria of abandoned farmland and farmland were Bradyrhizobium (64.7%) and Pseudomonas (47.7%), respectively. The abundance of Gemmata, Stella, unspecified Planctomycetes and Rhodoplanes in the two types of soil were significantly lower than that in soil of other lands (P<0.05). The pH and available phosphorus content were significantly and positively correlated with these bacteria. PCA analysis showes that phoD gene bacterial communities were similar between abandoned farmland soil and farmland soil (P<0.05). This study showes that there is a significant positive correlation between soil available phosphorus and phoD gene bacterial abundance. Tail water irrigation affected the community structure and diversity of phoD gene bacteria by affecting the physico-chemical properties of soil such as pH and available phosphorus content.

The dissolved organic matter (DOM) has complex biogeochemical characteristics that affect the carbon cycle, migration and transformation of pollutants. The sources and the key properties of DOM can be identified quickly by the spectral characteristics. Therefore, the DOM spectrum characteristics of biochar made from five kinds of typical biomass (apple branch, orange branch, peanut shell, rice straw and corn straw) prepared at the same pyrolysis temperature were explored by using ultraviolet-visible spectrum, three-dimensional fluorescence spectrum and fourier transform infrared spectrum. The results show that the dissolved organic carbon (DOC) of straw biochar is much higher than that of the other three biochars. Ultraviolet-visible spectrum analysis shows that the content of aromatic components in DOM of the five biochars was small, the humification degree was low, and hydrophilic components were dominant. Three-dimensional fluorescence spectrum analysis shows that the content of fluorescent components of straw biochar DOM was higher than those of wood biochar and shell biochar, and soluble microbial degradation products and humic acid were the highest in the proportion of fluorescent components. Fourier transform infrared spectroscopy shows that the DOM spectral characteristics of the five biochar species were similar.