The guaranteeing of natural ecological security boundaries is a new development goal proposed by the Fifth Plenary Session of the 19th Central Committee of the Communist Party of China, and it is an important direction for ecological conservation in the future. However, current research about natural ecological security boundaries does not provide sufficient theoretical support for ecological conservation and restoration. Based on environmental management practices, the concept of natural ecological security boundaries has been analyzed and their meaning has been described from two perspectives, namely boundaries of spatial distribution and environmental management. The challenges faced when attempting to guarantee natural ecological security boundaries, including those related to ecosystem quality, the ecological space estate, and supervision capacity construction has also been described. Based on the analysis, further research focus on natural ecological security boundaries are recommend, which include the strengthening of basic theoretical exploration, optimizing of territory planning, and designing of ecological restoration systems. In addition, future management of natural ecological security could be advanced by the strengthening of top-level design, improving of the legal protection system, and coordinating of demands for ecological conservation and economic development.

With increasing area of the transgenic crops, the biological and ecological safety of the transgenic crops has become a focus topic. To keep track of the global research trends and hot spots of safety of the transgenic crops, relevant literatures from 1999 to 2020 were explored based on the data of Web of Science(WOS) and China National Knowledge Infrastructure(CNKI), and software Hiscite and Citespace were used to achieve bibliometrics visual analysis. The results show that(1) the number of literatures in WOS increased at first and then stabilized, with the highest number of 237 literatures in 2018; the number of literatures in CNKI increased at first and then decreased, with the highest number of 68 publications in 2014; (2) United States, China, United Kingdom, Germany and France were the top 5 countries for publication numbers in WOS, with 1 246, 615, 342, 272 and 260 literatures, respectively; (3) Chinese Academy of Agricultural Sciences, Institut National de la Recherche Agronomique, Monsanto Company, Iowa State University and U.S. Department of Agriculture-Agricultural Research Service were the top 5 institutions for publication numbers in WOS, with 182, 115, 113, 112 and 93 literatures respectively; (4) In this field, 4 topics were highly concerned by the researchers, including gene flow, effects on non-target organisms, resistance of target pest and food safety. Among them, the study on effects of transgenic crops on non-target organisms were abundant, but the studies on gene flow were relatively lacking. In China, In addition, research hotspots in WOS were transgenic soybean, coexistence of transgenic and traditional crops, and environmental harm of transgenic crops, and research hotspots in CNKI were transgenic rice, comparison of transgenic and traditional breeding techniques, safety certificates.

In recent years, urban environmental pollution has become increasingly prominent and attracts widespread attention. Urban trees have the potential to trap dust and help to alleviate this type of environmental pollution. In particular, urban trees play an extremely important role in their capacity to trap dust. However, there is a lack of systematic research on the ability of urban trees to retain dust. Many researchers use different methods to screen, sort and grade tree species that have a strong ability to retain dust and optimize the allocation structure to explore these mechanisms. The differences in the methods currently used in these studies have resulted in a lack of reference for these studies. Therefore, the focus of the next step of this research is to combine and extend the effect of urban trees to retain dust using different multi-scale and multi-dimensional methods. Success with this goal should enable more comprehensive, reliable and practical methods for the evaluation of the further researches on this topic, including those on measurements, mechanisms, temporal and spatial characteristics, environmental impact factors and other influencing factors. The final goal of this paper is to address the existing problems of retention of dust by urban trees and the prospects for future research.

Soil environmental background value is the basis for soil pollution identification and plays an important role for environmental management. Several countries and regions have already carried out researches on soil environmental background value. In this paper, the definition of soil environmental background value is introduced, and the status of the application of soil environmental background value has been reviewed, including the development of soil environmental standard, the management of agricultural land sustainability, the identification of contaminated sites, the screening of the concerned contaminants, and the determination of remediation goals. The expressions of soil environmental background values are then summarized. At last, the problems in the application of soil environmental background values in China have been analyzed and some suggestions are proposed accordingly. This study can provide a reference for scientific research on soil environmental background value and its administrative management.

Monitoring of the environmental exposure level of emerging pollutants (EPs) is an important way to ascertain the pollution condition and control the risks of EPs. Developed countries and regions have established survey and monitoring system for EPs under the framework of chemical environmental management regulation and the surface water environmental quality assessment. The targeted and non-targeted screening and monitoring technologies were used to monitor and evaluate EPs such as endocrine disruptor chemicals (EDCs), persistent organic pollutants (POPs), microplastics and environmental persistent drugs et.al. The monitoring results, as well as the monitoring data platform have effectively promoted the prevention and control of environmental and health risks of EPs. In China, the monitoring of EPs is mainly at the level of scientific research. It is recommended that China should establish EPs monitoring system and develop the monitoring network as soon as possible. Based on foreign experiences, a three-level monitoring program for EPs, including screening, risk assessment and supervision should be established. Further, the monitoring aim, objective, region and the main technical methods need to be clarified on all levels. Meanwhile, the researches on EPs monitoring technology need to be constantly carried out in order to strengthen the EPs monitoring technical competence, and fully supporting the monitoring and treatment of EPs.

The study of the spatial distribution and overlapping relationship of natural protected areas is an important basis for constructing the system of natural protected areas dominated by national parks. This study selected 582 natural protected areas of 9 types in Hunan Province as the research objects, aiming at putting forward the integration optimization countermeasures by using geographic concentration index and ArcGIS spatial analysis to analyze the spatial distribution and overlapping characteristics of protected areas in Hunan Province. The results show that the natural protected areas in Hunan Province are distributed in an aggregation manner, and the number of natural protected areas in Wuling-Xuefeng mountain area and Nanling mountain area accounts for 61.41% of the total number of protected areas in the province, which is a geographical ecological area with dense distribution of natural protected areas. The cities of Hunan Province, such as Xiangxi Autonomous Prefecture, Huaihua City, Shaoyang City, and Yongzhou City, are the administrative districts with a large number of natural protected areas in Hunan Province. The phenomenon of overlapping of natural protected areas is prominent and the number of overlapping protected areas accounts for 45.02% of the province's natural protected areas. Meanwhile, among the intersecting overlap types, the number of one overlap type is the most, accounting for 75.56% of intersecting and overlapping protected areas number. In terms of the types of overlapping protected areas, the overlapping between nature reserves and forest park, between nature reserves and scenic spots, between nature reserves and wetland park, and between scenic spots and forest park are the most common. On the basis of analysis of the spatial overlap relationship of natural protected areas in Hunan, this study put forward suggestions for optimization and integration of natural protected areas, including integration supplement and boundary adjustment.

Fractional vegetation coverage (F_VC) is an important indicator of vegetation growth in arid and semi-arid regions. Trend analysis was used to study the spatial-temporal change of F_VC in Xilingol of Inner Mongolia from 2000 to 2019, and ordinary least squares (OLS) and geographical weighted regression (GWR) were used, respectively, to explore the dominant factors of F_VC based on 10 km×10 km grid. The results show that the annual growth of F_VC was 0.007 and F_VC owned the characteristics of overall improvement but with some local reduction. Spatially, F_VC decreased in parts of the east, significantly improved in the middle and was relatively stable in the west. The influencing factors of vegetation show that precipitation, atmospheric temperature and population were the dominant factors of F_VC with strong spatial aggregation, and the dominant proportion accounted for ≥ 82.10%. Specifically, precipitation was positively dominant. Temperature was negatively dominant. Population played a dual role, which gradually increased with the passage of time. The influences of elevation, slope gredient, slope aspect, sand, and clay on vegetation were not significant and with broken spatial aggregation. The dominant proportion accounted for only ≤ 17.10%. Mining had various effects on vegetation and vegetation had not been improved significantly around the open mining areas. When exploring the causes of spatial heterogeneity of vegetation in Xilingol, GWR was better than OLS. The study on F_VC has certain theoretical and practical significance for arid and semi-arid areas in Xilingol, and the results are expected to provide scientific supports for the ecological management in local areas of Xilingol.

In order to analyze the problems and influencing factors of shallow lake ecosystem, and to promote the protection and management of lake ecological environment more scientifically and precisely, Baima Lake was taken as a typical case and an index system was established for the evaluation of ecological security of lakes in plain water network area based on the Diring force-Presure-Status-Influence-Response (DPSIR) model and the comprehensive assessment method of lake ecological security ("4+1" assessment methodology framework). Meanwhile, the ecological security status, spatio-temporal difference and their affecting factors were also investigated, and the results show that the ecological security situation of Baima Lake was improved in the last few years, with the ESI (Ecological Security Index) rose from 66.70 in 2013 to 74.79 in 2018, which was at comprehensive safety degree. However, it was difficult to make quick balance within the ecosystem, and the improvement of water ecological health had an obvious delay. The whole ecological security status was ranked as in the "General State" level with a trend of gradually declining from south (ESI 82.78) to north (ESI 68.36). The correlation analysis results indicate that the main factors affecting the ecological security level were the pollution load from the upper reaches of the basin, the water quality of inflow rivers, the function of water conservation and the ability of pollution interception and purification. While the high interference of human activities were the fundamental reasons which caused the progressive deterioration of ecological security status in Baima Lake. Therefore, the primary task for the protection and management of shallow lakes is to control the external disturbance factors within the carrying capacity of lake basin.

Nitrogen is a principle nutrient for agricultural production, however during agricultural activities and consumption process, the low use efficiency and high loss rate of nitrogen have subsequently led to a series of nitrogen pollution problems. To improve the understanding of nitrogen use efficiency and its characteristics on environmental loads during agricultural production could help to develop approaches reducing the nitrogen release intensity. The present study established a nitrogen flow model of agroecosystem to analyze the nitrogen flow characteristics in Chishui Township, Nancheng Township and Shangyong Township, allocated in Dehua County in Daiyun Mountain Area of Fujian Province, using material flow analysis method. Results show that from 2002 to 2016, the nitrogen flow flux of crop production system in these three townships declined, especially the nitrogen input in Chishui Township decreased from 86.40 kg·hm^-2 in 2002 to 37.19 kg·hm^-2 in 2016. However, the nitrogen inputs in all these three townships were still higher than the national average level, and the excessive input of fertilizer nitrogen which accounted for 45.56%-72.26% of the total nitrogen input in crop production ecosystem, is the main reason of environmental nitrogen load in this area. Furthermore, in Shangyong Township, the nitrogen utilization rate was 27.05%-35.05% and the nitrogen loss rate was lower than that of the other two townships. Though the excessive fertilization has been progressively controlled during the last two decades, the relatively low nitrogen use efficiency and high loss rate compared with the national average level are still major problems for crop production in this area. It is therefore essential to develop sustainable agricultural production system in local farms for optimizing the environmental benefit. It is recommended to adjust the fertilizer formulas, improve the utilization rate of agricultural wastes and increase the recycling rate of nitrogen, to comprehensively reduce waste of resources and environmental pollution.

Understanding the potential distribution of Spartina alterniflora under climate change is necessary to formulate effective management measures and mitigate invasion danger. In this study, a multi-source data integration technology was developed to collect occurrence records of Spartina alterniflora in the Chinese coast. The MaxEnt model was used to predict the potential distribution of Spartina alterniflora under the current and future(2050s) climate change scenarios, and the effect of climate factors on species distribution was analyzed. Results show that sufficient occurrence records of Spartina alterniflora were obtained using the data integration technology, which can overcome spatial sampling bias and solve the difficulty of species information collection in complex environment. The prediction results of MaxEnt model were satisfactory, and the average values of AUC(area under curve) and standard deviation were 0.943 and 0.005, respectively. Under the current climatic condition, suitable areas for the distribution of Spartina alterniflora account for 9.35% of the total coastal areas, with the highly suitable areas accounting for 1.35%, which are mainly located in salt marshes of Jiangsu, Zhejiang and the north of Fujian. The spatial distribution of Spartina alterniflora are greatly affected by the climate factors, including isothermality, mean diurnal range, mean temperature of warmest quarter, etc., and these factors contribute more than 70% of the variation. Under two climate scenarios of RCP4.5 and RCP8.5, the suitable areas of Spartina alterniflora in 2050s will increase by 22.82% and 24.19%, respectively, compared with the current climate model, and show an expansive trend from coastline to inland. The high suitable area will increase by 7 470.04 and 13 208.47 km², respectively, and the expansion of medium and low suitable areas will be more obvious.

Based on the three phases of land use data and DEM data in the Guangxi border areas in 1980, 2010 and 2018 and by using the landscape ecological risk index, land use transfer matrix, topographic distribution index and other methods, the landscape ecological risk in the border area of Guangxi for the past 40 years was evaluated from the perspective of "production-living-ecological" space. At the same time, the spatial function transformation of "production-living-ecological" space and the influence of topographical factors on it were also explored. The results show that the ecological and production spaces were squeezed by the living space. During the study period, the living space had expanded significantly by 9 134.97 hm², while the ecological space and production spaces decreased by 3 899.60 and 5 235.40 hm², respectively. Landscape ecological risk as a whole was in a relatively low degree, while in some areas the risk increased first and then decreased. The land use function transformation of "agricultural production space-forest land ecological space" and "urban and rural living space-agricultural production space" had higher contribution rates to landscape ecological risk, which were 1.01% and 0.21%, respectively. From the perspective of the distribution of landscape ecological risk on the terrain gradient, altitude and slope were inversely related to the degree of landscape ecological risk. The above research results can provide reference for promoting the coordinated development of regional "production-living-ecological" space, for constructing a landscape ecological security pattern, and for exploring the optimal layout of high-quality land use with ecological priority and green development as the guidance.

Exploring the coupling coordination and spatio-temporal evolution characteristics of "production-living-ecological" functions is of great significance. It is a key measure to optimize the regional function and promote revitalization of rural areas. The coupling coordination model, local auto-correlation analysis, Dagum Gini coefficient and subgroup distribution method were employed in this study. Based on clarifying the connotation of "production-living-ecological" functions, and taking "county" as the evaluation unit, the evaluation value of the production function, living function and ecological function as well the comprehensive function of Jiangsu Province in 2002, 2007, 2012 and 2017 were calculated. Furthermore, the spatial-temporal evolution and coupling coordination law of "production-living-ecological" functions with multi-dimensional scale were revealed. It shows that during the study period, the high value agglomeration of rural "production-living-ecological" functions in Jiangsu province was prominent, and the spatial and temporal heterogeneity of production function was obvious. Northern Jiangsu and its border area with Central Jiangsu Province had prominent advantages in production functions, and the regional units of ecological function superiority showed an expanding trend. The "production-living-ecological" functions in rural areas of Jiangsu Province are mostly in the running-in stage and the high-level coupling stage, and the proportion of extremely weakly coupled regional units was the lowest. The middle and southern regions of Jiangsu Province were mainly high coupling units. The proportion of general coordinated regional units of "production-living-ecological" was the highest, and the level of coupling coordinated development showed a weakening trend. Moreover, the low level coupling and coordinated development of production-living-ecological functions in rural areas in Jiangsu Province had been deteriorating continuously, and most of them were in the unbalanced coordination zone and the transition coordination zone, without realizing the benign spatial resonance. The imbalance of rural "production-living-ecological" functions in Jiangsu Province experienced an evolutionary process of rising, decreasing and rising, and the gap between groups in southern Jiangsu Province was always small. The fluctuation trend of disequilibrium degree of life function was consistent with the comprehensive function of "production-living-ecological" and the regional disequilibrium of ecological function gradually weakened during the study period. The level of health care and ecological environment play vital roles in promoting the "production-living-ecological" function in rural areas of Jiangsu Province.

The occupancy model can be used for infrared camera research on large and medium-sized mammals. The model is aimed to understand the proportion and spatial distribution of the area occupied by a species or its suitable habitat, and to assess the impact of environmental factors on the species occupancy. In this study, 40 infrared cameras were deployed for monitoring in Fanjingshan and Chishui Alsophila National Nature Reserves from April to July 2019, respectively. Subsequently, 22 mammal species within 4 orders and 12 families, and 19 mammal species within 4 orders and 10 families were captured in the two nature reserves, respectively. The survey show that the relative abundance index of large and medium-sized mammals in both the two reserves was higher in the Tibetan macaque (Macaca thibetana), wild boar (Sus scrofa), Reeves' muntjac (Muntiacus reevesi) and tufted deer (Elaphodus cephalophus). Furthermore, the occupancy status and influencing factors of the above four species were analyzed by using the occupancy model. The results show that the occupancy rates of the four species were 0.67, 0.53, 0.37, 0.58, and the detection probabilities were 0.20, 0.21, 0.31, 0.27, respectively. The occupancy of Tibetan macaque was negatively affected by elevation and slope, and positively affected by shrub coverage. The wild boar was negatively affected by shrub coverage and slope, but positively affected by elevation. The Reeves' muntjac was negatively correlated with shrub coverage, and slightly with nelevation, but positively affected by slope in some extent. The tufted deer was positively affected by shrub coverage, and negatively affected by slope. Finally, the author further summarized the application scope of the occupancy model and the existing problems in the researches, and it is expected that this method coiuld be widerly applied in thefuture researches.

Study on the spatial distribution of a species' habitat and relationship between its habitat and environmental factors is of great significance for understanding the suitable habitat distribution of a target species and its habitat demand. The study on habitat spatial pattern of Moschus moschiferus is helpful to provide scientific basis for its habitat management and conservation. The potential habitat distribution and main influencing factors were analyzed by using the MaxEnt model in the Huanglong Mountains of Shaanxi Province. The results of the analyses show an excellent prediction performance, with an area under curve of >0.9 for model training and validation. The dominate factors identified and their thresholds were mean temperature of the driest quarter (<-3.6℃), distance to road (>4 100 m), slope degree (>71.5°), precipitation seasonality (81.5~85.0, optimum 83.5) and mean diurnal ranger (<11.6℃ optimum 9.5℃). The suitable habitats areas cover a total area of 677.75 km² and are mainly distributed in southeast of Yichuan, northeast of Huanglong and its junction with Luochuan, and northwest of Hancheng, while the medium suitable habitat areas cover a total area of 2 797.75 km² and are mainly distributed around all the suitable habitat areas and also in southwest of Yichuan, northwest and east of Huanglong, and northeast of Luochuan. The suitable habitat area of each county or city was Yichuan > Hancheng > Huanglong > Luochuan, while the moderate suitable habitat area was Huanglong > Yichuan > Luochuan > Hancheng. The protection and management of suitable and moderate suitable habitat areas should be strengthened. The people entering the mountains should be controlled and educated, so as to reduce the interference and killing of Moschus moschiferus. Meanwhile, it is suggested that the forestry authority should adjust the suitable habitat area of Moschus moschiferus in Yichuan into the planning of Huanglongshan National Nature Reserve of Shaanxi Province in the near future, and a new reserve should be established at the junction of Luochuan, Huanglong and Yichuan in the long term.

Contents of 16 polycyclic aromatic hydrocarbons(PAHs) listed for prior control by USEPA in soil samples from a large coking plant site were detected. The characteristics of horizontal and vertical distribution of the 16 PAHs were discussed, while their ecological risk and sources were investigated. Results show that:(1) The total PAHs(ΣPAHs) contents ranged from 0-47 912.23 mg·kg^-1 with a maximum of ΣPAHs in indigenous coking area; Moreover, the contents of ΣPAHs in indigenous coking area, chemical production area were higher than those in other areas,which were mainly made up of naphthalene; Besides, the contents of ΣPAHs in <3 m depth soil were higher than those in the subsoil. (2) The ecological risk sequence in different areas showed indigenous coking area> chemical production area> coking area> coal yard> office area. (3) The content ratios of total 2-3 rings PAHs and 4-6 rings PAHs revealed that the PAHs in chemical production area were mainly originated from coal tar leaking, while the PAHs in coking area, coal yard and office area mainly from soot deposition made by coking. In addition, the PAHs in indigenous coking area were mainly from both coal tar leaking and soot deposition.