In the process of economic development, the unreasonable land allocation had led to deterioration of urban ecological environment which includes soil and water loss, farmland degradation and traffic jam. Therefore, optimal land use allocation has been regarded as one of the keys to the sustainable development of cities. Since some significant contradictions often exist between land development and nature conservation, land use allocation confronts great challenges to balance land use suitability, compactness and ecosystem services values.
In order to solve this problem, this paper aims to propose an ideal solution by using the multiobjective particle swarm optimization algorithm based on principle of pareto optimization. Six major land use types are arranged in study area which included cultivated land, forest land, wetland, waterbody, habitat and industry land. Three objective functions are defined: maximizing suitability, maximizing ecosystem service value, maximizing land use compactness. As the initial swarm was created, the values of the objective functions were calculated, and nondominated answers were preserved in an external archive. To prevent particle swarm sticking into local convergence, mutation operators were added to the particle swarms to promote the uniform distribution of particles. Combining with the constraints of the land policy, the Paretofront that meets the realistic requirements was finally formed in the threedimensional space. We selected Wujin district of Changzhou as study area, which had the land use maps, urban planning and socioeconomic data for the experiment of optimal land use allocation.
The results show that a uniform set of ParetoFrontiers can be obtained by applying the model, which means that each result is an optimal land use allocation. The optimized allocation improves the land suitability, ecosystem service value and land compactness by 9.96%, 4.27%, and 5.23% respectively. Compared with singleobjective model that can only produce one result, the model can obtain more optimized allocations with the same optimal level, different quantity structure and spatial characteristics, which can be better support for land use planning.

There are a lot of theoretical and practical researches on the urban land use efficiency, but the existing research has not reached a consensus on the measuring method and influencing mechanisms of land use efficiency. From the research content, research methods and research conclusions，the paper uses the method of induction and comparative analysis to sort out and summarize the related problems of urban land use efficiency, analyzed the causes of the differences in existing research results, and try to find out the direction of land use efficiency in the future. It is found that the current research on urban land use efficiency mainly includes two aspects: measurement and influence mechanism of efficiency. In addition, the research on land use efficiency evaluation has improved the theoretical system of efficiency, but the research perspective is single and the research significance has certain limitations. The research content and method of land use efficiency impact mechanism are more diverse, but there are more empirical studies and lack of theoretical explanation. Future research needs to improve the research system of land use efficiency in cities, especially development zones, considering the relationship between land use efficiency and land marketization reform, supplyside reform, putting forward feasible policy of how to improve urban land use efficiency in economic transformation and development.

The paper use the two stage DEA model to calculate the rural collective construction land market efficiency, and then analyze the influence of transaction cost, asset specificity; transaction uncertainty and other factors on the demand side of efficiency, which is based on the 398 survey data of the rural collective construction land market in Nanhai District. The results show that: (1) The overall efficiency of rural collective construction land market is 0.230, the pure technical efficiency is 0.390, and the scale efficiency is 0.658. Most of the market scale is in the increasing stage, which can attract more social capital to participate in the construction of new countryside for promoting urbanization and urban upgrading. (2) The transaction cost has no significant influence on land market efficiency, which is related to the sublease behavior in the market. (3) The aspect of asset specificity: transaction subject, enterprises with high skill level workers are helpful to improve the land market efficiency. Transaction object, in equilibrium, the higher factor price in agglomeration area mean better production factor matching, and the efficiency of the rural collective construction land market is higher. (4) The side of transaction uncertainty, transaction behavior, enterprises will choose to increase production input to optimize the level of market resource allocation when the enterprise life cycle is more matched with the land use cycle. Transaction environment, the way of price determination has a significant impact on market efficiency. The lower the transaction uncertainty is, the more favorable it is for the demander to improve the expectation of rural collective land market and market efficiency. Therefore, the rural collective construction land market can promote the consolidation and rectification of rural collective land space and then reduce the fragmentation degree. At the same time, the transaction system of the collective construction primary land market and the secondary market should be constructed to improve the inputoutput efficiency on the demand side.

In order to evaluate the environmental risk and bearing potential of livestock and poultry breeding in the middle and lower reaches of Yangtze River, the total amount of livestock and poultry manure, livestock manure nitrogen (N) and phosphorus (P) load on farmland as well as environmental capacity of livestock and poultry breeding in the middle and lower reaches of Yangtze River were carefully calculated using the statistical data of 2016. The handbooks of “Pollutant generation coefficient and discharge coefficient in livestock and poultry breeding industry” and “Technical guide for the measurement of soil bearing capacity of livestock and poultry manure” provided the references during the calculation. The results showed: （1) the total amount of livestock and poultry manure in the middle and lower reaches of Yangtze River was 447.84 million tons; livestock manure N and P load on farmland were 71.18 kg/hm2 and 12.71 kg/hm2, respectively; the environmental capacity of livestock and poultry breeding was 765.62 million (N) and 1 062.09 million (P), and the environmental risk index was 0.68 (N) and 0.84 (P). The environmental risk level of livestock and poultry breeding was medium, which indicated there was certain development potential with the incremental scale of 47% (N) and 19% (P) in this area. （2) In terms of the provincial differences, the abundance of livestock and poultry manure followed the order of Hunan > Hubei > Anhui > Jiangxi > Jiangsu > Zhejiang > Shanghai, the nitrogen load of cultivated land had the order of Hunan > Hubei > Jiangxi > Anhui > Jiangsu > Zhejiang > Shanghai, and the order of livestock manure P load on farmland was Hunan > Hubei > Jiangxi > Jiangsu > Anhui > Zhejiang > Shanghai. The environmental risk level of livestock and poultry breeding in Shanghai, Jiangsu, Zhejiang, Anhui, Hubei and Hunan was medium, thus, these provinces had the potential to expand livestock and poultry breeding. In contrast, the environmental risk level of livestock and poultry breeding in Jiangxi was a bit serious, the implement of massbased controls might be needed. (3) In terms of the city differences, almost 59% of the total cities’ livestock and poultry farming environmental risk level was medium, about 28% was a little serious and 3% was serious, while about 10% was less. Thus, it was necessary to optimize the distribution of livestock and poultry breeding based on key control areas, restrained development areas, moderate development areas, potential growth areas and key development areas, and dynamic adjustment according to the regional planting industry structure in the middle and lower reaches of Yangtze River was proposed.

Landuse is an important carrier and intuitive result of urbanization process.  Driven by the dual transformation of China’s land system and developed regional economy, the interrelationship between urbanization and land use nonagriculturalization in coastal areas and its evolution are uniquely explored.  Based on the county land use information of Zhejiang Province in 2005, 2010 and 2015, this paper quantitatively analyzes the differentiation of county comprehensive urbanization, land use nonagriculturalization and the conversion source and flow of key county construction land in 2005-2015. Then use the Theil index and the bivariate spatial autocorrelation method to explore the spatial correlation model of urbanization level and land use nonagriculturalization in Zhejiang  Provinces.  (1) The level of urbanization in Zhejiang County is rapidly increasing and gradually achieving spatial balance and forming a grouplike urbanization situation centered on Hangzhou, Ningbo，Jinhua, Wenzhou and other municipal districts; the focus of construction land changes from the central and northern plains to the southeast coastal plains. However, the increase in the municipal area is still the most obvious. The increase or decrease of land for agricultural conversion is the key reason for the largescale change in construction land in Zhejiang County; (2) The spatial positive correlation between land nonagriculturalization and urbanization in Zhejiang Province has increased significantly, and the spatial differentiation situation has been highlighted. It has shown that the highaggregation area has shifted from the middle part to the east coast of Zhejiang and the islands. In general, the highhigh type is mostly distributed in the northern Zhejiang Plain, while the lowlow type extends from the coastal to the inland. (3) There is a significant scale effect of comprehensive urbanization and land use nonagriculturalization in Zhejiang Province, and the correlation difference increases with spatial scale.  This study reveals the spatial correlation between urbanization and land nonagriculturalization in the period of urbanization of economically developed provinces. It has important guiding value for promoting the synergy of land use planning and urban planning, and implementing land transfer and transadministrative area replacement according to local conditions.

Starting from the concept of rural complex,quantitatively evaluate the building capacity of the rural complex in township,and provide theoretical support for the comprehensive utilization of agricultural land in Gaochun District.Taking Gaochun District of Nanjing as an example, this study constructed a quantitative measurement system covering modern agriculture, leisure tourism and rural communities, and used GIS spatial analysis, TOPSIS and obstacle model to analyze the building capacity and impediments of rural complex,which we took the town as the study scale,on the basis of which to refine the development path of differentiation.The results showed that:(1)The spatial differences of building capacity were significant in modern agriculture, leisure tourism and rural communities.(2) The three dimensions of leisure tourism, rural communities and modern agriculture had different degrees and directions for the building capacity of rural complex.(3)The main barrier factors were different from each other, and the factors had complex control effects. (4)The research proposed corresponding construction paths for the land use of the eastern slow city ecological zone, the central and southern surrounding wet area, the western water township network area, and the central and northern center old city.

Ecosystem services are a fundamental concept in natural environment management and sustainable land use. Most previous studies focus on assessments of ecosystem services, while less research quantified the supply and demand of ecosystem services, as well as the balance. This paper quantified the deficit and surplus of ecosystem services in a context of rapid urbanization, and put forward suggestions for sustainable land development path. Hubei province was used as a case study, four ecosystem services, including water conservation, PM10 removal, carbon sequestration and recreation were selected to evaluate the surplus and deficit of ecosystem services in Hubei province from 2010 to 2015, and the equilibrium threshold (i.e., supplydemand balance) was calculated. The results showed that: (1) all focal ecosystem services were in deficit expect water conservation; (2) the equilibrium of water conservation services was relatively stable through time, while larger deficits were produced for other services; (3) the supplydemand of ecosystem services presented evident spatial heterogeneity; and (4) the green space ratio threshold required by the balance increased, while the construction land threshold ratio decreased. This study provided a scientific support for sustainable land management by quantifying the supply and demand of ecosystem services. We suggest that Hubei government should put more efforts on the removal of PM10 and carbon emission control during urbanization, increase urban green space and control the expansion of construction land.

To protect the habitat and germplasm resources of Eriocheir sinensis furtherlly and assess the nutritional relationship of the Yangtze River crabs scientifically. Besides, providing reference for exploitation and utilization. Stable isotope technology was employed to in the analysis of the stable isotopes of Eriocheir sinensis and Chiromantes dehaani in Jingjiang section, Xinkai sand and Langshan sand of Yangtze River. In addition, the research detected the δ13C and δ15N values of Eriocheir sinensis and Chiromantes dehaani. The results are used to figure out the area of trophic niches and the niche widths of two species. As the results revealed, there were significant differences in δ13C between Eriocheir sinensis and Chiromantes dehaani（P<0.05). The range of δ13C signatures in Eriocheir sinensisis greater than those of Chiromantes dehaani, indicating that Eriocheir sinensis feeds on more food resources. The range of δ13C signatures in Eriocheir sinensis and Chiromantes dehaani are relatively concentrated at -25.00‰ to -23.00‰ and -26.00‰ to -24.00‰ respectively, which indicate that both species prefer certain food. There is an overlap of trophic niches between Eriocheir sinensis and Chiromantes dehaani indicating the intercomposition for the two species. The overlap of trophic niches in Jingjiang section is larger, which shows that the intercomposition between the two species in Jingjiang section is the most intense. The amplitude of δ13C signatures(CR), δ15N signatures (NR) and total trophic area(Ta) in Eriocheir sinensis are all greater than those of Chiromantes dehaani, which specifies that Eriocheir sinensis has more competitive power for food resources.

Chinese sturgeon (Acipenser sinensis Gary) is a large anadromous species, which matures in coastal waters and enters into rivers for spawning. This species was listed in the IUCN Red List as the endangered in 1996 and Critically Endengered in 2010. However, this kind of threatened categories of this species is questionable since no systematic criterion had been established for such classificaiton. This study established the classification criterion for endangered levels of this species on the basis of the IUCN Red List Categories and Criteria. Data from the biological changes (i.e., decline in the spawning population and spawning sizes, changes in the sex ratio) and the abiotic changes (i.e., habitat fragmentation, environmental changes, anthropogenic activities such as overfishing, river damming) were collected and analyzed. This study classified such data by decades to reveal the generational changes in Yangtze stocks of Chinese sturgeon and abiotic factors. Moreover, the biological and abiotic changes from the spawning grounds were used for the establishments of endangered categories of Chinese sturgeon, refering to the indexs of mature individuals and area of occupancy from the IUCN Red List Categories and Criteria. This study revealed that both spawning stocks and spawning sizes in the spawning grounds declined sharply since 1980s. Abiotic changes affected such decline varied over the decades. According to the endangered criterion esatblised in this study, Chinese sturgeon is endangered during the periods from 1983 to 1992 and critically endangered during the periods from 2003 to 2012. The endangered levels of Chinese sturgeon were affected by multiple factors, mainly the population quality, anthropogenic activities, and environmental changes. The influence of anthropogenic activities and changes in environmental structure on Chinese sturgeon demonstrates a highly diversity and complexity pattern. This type of influence varied with temporal and spatial scales. Based on the endangered status of Chinese sturgeon and affected factors, the countermeasures and effects in different decades were evaluated. Finally, the framework for the conservation options and strategies of Chinese sturgeon were proposed.

Based on the fish resources surveys in Jianli section of the Yangtze River from 2013 to 2015 and 2017 to 2018, the fish community structure and species diversity were described using ShannonWiener diversity index, Simpson dominance index, Margalef’s richness index, Pielou’s evenness index and multivariate statistical analysis, respectively. A total of 68 fish species belonging to 13 families and 6 orders were collected during monitoring periods. They were dominated by Cypriniforme. The numbers of fish species in 2018 were more than those in other years. There were no significant variations in Pielou’s evenness index in different years, while ShannonWiener diversity index and Margalef’s richness index in 2018 were highest in all years. Simpson dominance index fluctuated to some extent, but they were all low in the five years. The abundancebiomass curves (ABC) and Wstatistical analysis indicated that fish community was suffering with high disturbance in 2013 and 2014, while the community was not disturbed in 2015, 2017 and 2018. The fish community structures in the five years were divided into three groups by using cluster analysis and nonmetric multidimensional scaling (NMDS) methods．No significant difference was found by the analysis of similarity statistics (ANOSIM)  during these three groups.

Soil Testing and Formulated Fertilization Technology can promote the costsaving and efficiency of agricultural, improve the level of farmers’ scientific fertilization, and purify agricultural production environment. However, there are still some problems that make the adoption rate of Soil Testing and Formulated Fertilization Technology to be further improved, such as farmers’ unclear cognition, unsoundness of the government extension mechanism, imperfect supporting services, etc. In order to more effectively promote the Soil Testing and Formulated Fertilization Technology, this study is based on the survey data of 277 farmers in Jiangxi Province, using Structural Equation Modeling (SEM) to quantitatively explore the impact of farmers’ subjective awareness and environmental background on farmers’ willingness to improve the adoption rate of Soil Testing and Formulated Fertilization Technology. In SEM, latent variables including the farmers’ willingness to adopt, the perceived usefulness, the perceived ease of use, the subjective norms, the convenience conditions, the results display, and household characteristics. The results show that the perceived usefulness, the perceived ease of use, and the subjective norms are the key factors affecting farmers’ willingness to adopt; the degree of influence is ranked as the perceived ease of use (0.431)> the perceived usefulness (0.325)> the subjective norms (0.266); the results display and farmer characteristics have significant positive impact on the perceived usefulness and the perceived ease of use; the convenience conditions have a significant positive impact on the perceived ease of use.Based on the above research results, we could further promote the Soil Testing and Formulated Fertilization Technology from the four aspects of the farmer guidance, the government support, the technological innovation and the evaluation system construction.

Under the background of the shortage of agricultural resources, China’s agriculture shows the phenomenon of production agglomeration. From the perspective of agglomeration effect, the formation of agricultural production agglomeration is the result of the interaction of resource endowment and external factors. This paper systematically combs the intrinsic mechanism between resource endowment characteristics, externalities and agricultural production agglomeration, and uses panel data of 31 provinces in China from 1996 to 2015 to process empirical data by means of fixed effect model and generalized moment estimation. Through theoretical analysis and regression analysis, it is found that: (1) agricultural capital Agricultural labor force, agricultural capital stock, agricultural technology level and cultivated land resources have a significant role in promoting the level of production agglomeration. However, natural disasters and topography play a significant role in restricting the level of agricultural production. (2) From the impact of the trend, the number of agricultural land, agricultural technology level on the level of agricultural production concentration showed a “U” type of development trend. The number of agricultural labor force and agricultural capital stock showed a trend of “U”.

Based on the survey data of 668 farmers in Hebei, Anhui and Hubei provinces，this paper analyzed the embeddedness factors that influenced farmers’ adoption of conservation tillage technology in the light of social embeddedness theory. The results showed that the “embeddedness factors” of nine variables from three dimensions，namely， government support，farmers’ cognition and social capital network，had a significant influence on farmers’ adoption of conservation tillage technology. Among those factors under investigation, government policy publicity，farmers' cognition of ecological, social and economic values, interpersonal trust, institutional trust, reciprocity norms and farmers’ participation network had positive effects on farmers’ conservation tillage technology adoption. Thus, in order to facilitate farmers’ adoption of conservation tillage technology，government should raise awareness of the importance of conservation tillage technology，strengthen the publicity of conservation tillage technology，and support the construction of a social-embedding environment which is conducive to the promotion of conservation tillage technology according to local conditions.

The delta is usually located in the transition zone between large surface water bodies such as rivers, lakes and oceans, supporting about 8% of the world's population. However, the delta system is considered to be a highly sensitive and vulnerable zone of many ecosystems due to multiple factors such as low terrain, reduced sands from the upstream river and rising sea levels, thus has attracted lots of attention from policymakers, scientists and inhabitants. In recent years, surface hydrological connectivity has become a hot issue in hydrology and hydrodynamics research of river delta. This study presents a review of surface hydrological connectivity in the river delta area. Based on bibliography analysis, the concept and composition of surface hydrological connectivity in the river delta were introduced, and its relationship between delta morphology was then discussed. The results show that delta surface hydrological connectivity can be classified into structural connectivity, functional connectivity and process connectivity. Structural connectivity based on graph theory only characterizes the role of river networks in hydrological connectivity in the river delta, while functional connectivity and process connectivity reflects the spatial distribution of hydrodynamic elements and their coupling with meteorological and other environmental factors, which needs effective field observations and survey datasets. In addition, delta morphology and hydrological connectivity are related, and some morphological indicators can be used to describe surface hydrological connectivity in the river delta, such as nearest-edge distance, synthetic sediment fluxes and nourishment area. Due to the high spatial and temporal heterogeneity and complex topography of the delta, the multi-disciplinary research strategies such as field observation, mathematical statistics and numerical simulation should be adopted in the future to improve understanding of hydrological connectivity in the river delta. This paper provides references for the study of environmental effects of deltas under the influence of climate change and human activities, and also provides a scientific basis from hydrology perspective for major environmental issues such as the adapting of delta wetland ecosystems to the rapidly changing environment.

Improving environmental quality is an important connotation and inevitable requirement for economic development with high quality. Based on the two perspectives of environmental pollution and environmental absorption, this paper USES SDM model to analyze the influencing factors and spatial effects of national and regional environmental quality based on the comprehensive assessment of environmental pollution index and absorption index based on the comprehensive atmospheric, soil and water environment factors. Research findings:(1) the spatial agglomeration features of environmental quality are obvious, regional imbalance is prominent, and the trend of environmental deterioration has not been fundamentally reversed; (2) high proportion of heavy industry is the main reason for low environmental quality; (3) the environmental quality and economic development in the eastern region gradually tend to be coordinated, but the population agglomeration has brought great negative impacts on the environment. The development mode of “high investment, high energy consumption, high pollution and low efficiency” in central and western regions has become a constraint to improve environmental quality. Finally, according to the characteristics of different regions, this paper puts forward the differentiated environmental governance path of the integration“hard governance” and “soft governance”.

Related documents on environmental governance in China, according to the introduction of concept of ideal types, are sorted out in a systematical manner. With the help of the theoretical framework of action system, four ideal types of environmental governance are distinguished by taking actors and means of actions as the dimensions. Those four types are single-center scientism model, multi-center scientism model, single-center humanism model and multi-center humanism model, with their corresponding typical practices of campaign-styled, market-oriented, resistance-based and participative environmental governance, the current research progress of which is also reviewed. On the basis of the comparative study of ideal types, it concluded thatthe overall current characteristics of environmental governance in China features governmentdominated by means of scientific approaches, and the future development direction is predicted to be comprehensive and innovative environmental governance.

Based on data from 285 cities in China from 2003 to 2016，the impact mechanism of human capital and technological innovation on environmental pollution was discussed. The main research conclusions are as follows：（1）Human capital and technological innovation can significantly reduce environmental pollution；（2）Human capital and technological innovation have synergistic effects on environmental pollution. Under the influence of human capital，technological innovation shows a clear pollution reduction effect. Under the influence of technological innovation, human capital also shows a clear decontamination effect；（3）human capital and technological innovation cross the respective thresholds，the synergy effect of the two will be enhanced，and the pollution reduction effect will be more obvious；（4）human capital and technology The impact of innovation on environmental pollution is achieved through three types of intermediary channels：“industrial cleansing effect”，“foreign cleansing effect”and“financial cleansing effect”. The conclusions of this paper provide useful reference for the treatment of environmental pollution in China.

As an effect of global climate change, extreme temperature events occur frequently in most parts of China that have serious social and environmental impacts. The Qinling-Huaihe River, an important geographical dividing line between North and South China, belongs to ecologically fragile and climate sensitive areas that are vulnerable to extreme high temperatures. Based on the daily maximum temperature, minimum temperature and average relative humidity data from 1960 to 2017 in the north and south of the Qinling-Huaihe River,the Spatiotemporal variation characteristics of high temperature and humidity in the north and south of the Qinling-Huaihe river were investigated by using the apparent temperature index, combined with ESMD (Extreme-point Symmetric Mode Decomposition) trend analysis and special spatial interpolation software for meteorological elements-ANUSPLIN. The relationship between sea surface temperature (SST) anomalies in the eastern equatorial Pacific and multi-time-scale response of high temperature and humidity were discussed using the wavelet coherence method. The results show that: (1) In terms of trend change, taking the mid-1980s and 2010 as the time node, the high temperature and humidity conditions show the characteristics of stage change in the north and south of the Qinling-Huaihe River. The north of Qinling-Huaihe River and Qinba Mountains show the trend of “descending-slowly rising-rising”, while the south of Qinling-Huaihe and Huaihe Plain show the trend of “descending-slowly rising-descending”. (2) In regard to spatial variation, the high temperature and humidity conditions in Qinling-Huaihe are characterized by “more east and less west, more south and less north”, and the influence of this pattern continues to expand northward. (3) The effect of the SST anomaly in the eastern equatorial Pacific on the northern Qinling-Huaihe River region is more significant than that in the western region. The long-term periodic scale is more stable than the short-term periodic scale. On the short-term scale of 2-8a, when the SST in the eastern equatorial Pacific Ocean is abnormally high, the high temperature and high humid weather in each region decrease. On the long-term scale of 14-16a, when the SST anomaly is high, the high temperature and humidity conditions in the lower reaches of the Yellow River and Qinba Mountains increase.

Based on the field observation data of current velocity and suspended sediment concentration (SSC) measured in the upper reach of North Channel in the Changjiang Estuary from 15th April to 24th April in 2018, the vertical distribution patterns of SSC during the neap and spring tides are studied. The results show the SSCs in the study area were relatively low, with the mean value of only 0.17 kg/m3. SSCs were higher in spring tide than in neap tide, and close to each other for the flood-mean and ebb-mean values. Tidal currents were much stronger in spring tide than in neap tide, and in ebb phase than in flood phase. Salinity was considerable low during the survey period, with the mean value of only 0.16 psu. The neap-spring variation, flood-ebb variation and vertical variation of salinity were all very small, indicating the impact of salinity-induced stratification on the SSC profile is negligible. In such hydrodynamics, sediment dynamics and salinity condition, the SSCs profiles during the spring tide were the linear type and exponential type. But during the neap tide the SSCs profiles were the linear type, vertical-line type and exponential type, and the linear profile was the dominant type. By fitting Rouse equation, we found that most of measured SSCs profiles fitted Rouse equation roughly, and the settling velocity of suspended sediment deduced by this equation is between 0.36-2.89 mm/s.
Soulsby equation can accurately predict the observed linear and vertical-line types of SSC profiles, with the average error less than 10%.

The Lower Yangtze River is the typical anabranching channel, where the head of mid-channel bars are facing the seriously scouring situation under the impact of the sediment-starved flow, e.g., Tiebanzhou Island in the Datong reach. Water-sediment temporal change, area of Tiebanzhou Island, sediment deposition of bar head, and hydrodynamic characteristics (MIKE 21 model) were analyzed using the hydrological data of the Datong station (1956-2014), remote sensing imagery (1998-2016), channel topography (2004-2011). From 2003 to 2014, the mean annual runoff in the Datong station did not change much, but the mean annual sediment load decreased by 67.4%. The Tiebanzhou Island was eroded by the sediment-starved flow in the long-term, i.e., the volume of the bar head eroded from 1,635,700 m3 in 2004 to 688,400 m3 in 2011, and the average erosion rate from 8.88% in 2004-2008 increased to 11.57% in 2008-2011. The hydrodynamic simulation demonstrated that the greater incoming discharge, the strong scouring effect on the bar head, i.e., the erosion in flood seasons stronger than that in non-flood seasons. Owing to the backward slope and blocking effect on the upstream of bar head, the flow velocity decreases along the upper segment of the bar head, and sharply drops to zero when the flow is approaching the front of the bar head. The maximum velocity appears on the left side of the bar head that leads to the left side as the main erosion area.

In order to further understand the variation characteristic of the occurrence dates of critical temperature during safe growing period for double-season rice in Anhui Province, this paper analyzed the variation characteristics of safe sowing date and safe transplanting date for early-season rice, safe full heading date and safe maturity date for late-season rice, as well as days and accumulated temperature during safe growing period for double-season rice, which was planted in the region along the Yangtze River in Anhui province, using linear fitting and non-parameter Mann-Kendall test method, based on the data include daily mean temperature from 1961 to 2017 at the meteorological stations in 22 double-cropping rice producing counties in Anhui Province. Results showed that the safe sowing date for early-season rice showed a significant advance trend (P<0.05) in recent five decades, in which the average sowing date for seedling raising with plastic mulching was advanced by 1.8 daysper decade, and for seedling raising in open field was advanced by 1.5 days per decade. And the safe transplanting date for early-season rice significantly (P <0.01) advanced by 2.5days per decade averagely. The safe full heading date and safe maturity date for late-season rice both insignificantly delayed (P> 0.05). In addition, the days and accumulated temperature during safe growing period of double-season rice increased significantly (P<0.01), with an average increase of 2.6 days and 62.7℃·per decade respectively. The increase for days and accumulated temperature had a positive influence on planting and cultivar selection for double-season rice. On the basis of the traditional cropping pattern, the occurrence probability of damage which caused by low temperature in the duration of sowing and emergency for early rice decreased with the increase of days for safe growing period, so did it in the duration of full heading and maturity for late rice. As for the cultivar selection, it is suggested that mid-early-maturing varieties could be replaced by mid-late varieties which the duration of the growth is longer and yield is higher. However, the risk of chilling injury for late-season rice probably happened because of adopting the management of direct seeding and mechanical transplanting.

This paper systematically analyzes the characteristics of spatial and temporal distribution of NO2 vertical column density from 2005 to 2017 in Chengdu-Chongqing Urban Agglomeration (CCUA). The tropospheric NO2 vertical column density data were from the latest version of OMI (Ozone Monitoring Instrument) sensor of Aura satellite. The techniques of linear fitting, trend analysis and spatial autocorrelation analysis were used in this paper. The results showed that in CCUA there was reasonable correlation between the ground monitoring NO2 column density and the data from OMI sensor, and their variation trends were basically consistent. From 2005 to 2012, the annual NO2 column density increased about 52.38%, and it decreased after 2012, and for the density level in four seasons, winter > autumn > spring > summer. The monthly averaged values showed obvious periodicity, which was expressed in terms of sinusoidal function. The cycle was about one year, with the lowest value in July or August, and the highest value in November, December or January;Spatially, the NO2 column density in thecomparatively developed areas were higher than in the economic less-developed areas. From 2005 to 2012, for about 99.58% of the total area, the NO2 column density increased and from 2012 to 2017. for about 80.50% of the total area, the NO2 column density decreased. In general, from 2005 to 2017, in the eastern and western mountainous areas of CCUA, the NO2 column density showed an increasing trend, and there was a significantly positive spatial correlation in Chengdu and Chongqing.

With the acceleration of urbanization, air pollution has become one of the most important urban problems in China, affecting public health seriously. At present, there are few studies to explore the influence of landscape pattern on PM2.5 concentration at the microscopic scale. Therefore, the current study, taking the Chang-Zhu-Tan urban agglomeration as an example, selected six predictors including terrain, pollution, population, road traffic, land use and urban landscape pattern, then used a stepwise linear regression model to explore the effects of urban landscape pattern on PM2.5 concentration. The urban landscape pattern was represented by seven landscape metrics which were ED, CONTIG, LSI, AREA_MN, CONTAG and SHEI. The results showed that: 1) the selected landscapes metrics could explain 73.2% variation of PM2.5 concentration in the study area and the model fitted well; 2) the types of land use that affected PM2.5 concentration included construction land, woodland, grassland and water body. At the microscopic scale, landscape metrics including CONTIG and LSI had significant effects on PM2.5. When the contiguity of construction land was higher, the distribution was more concentrated. Consequently, PM2.5 concentration was higher. If the shape index of water body was smaller, the shape of water body was simpler and more regular. It was easier to reduce PM2.5 concentration; 3) at the overall urban landscape-level, landscape aggregation degree and landscape diversity had important impacts on PM2.5 concentration. Reducing the discrete distribution of various types of patches in the landscape, which could make each landscape type evenly distribute in the overall landscape, could help to reduce PM2.5 concentration. Results of this research could provide reference for future atmosphere control and urban planning.

Urban waterlogging caused by long duration heavy rainfall events has become a serious problem in urban safety construction and development in China. Therefore, it is of great significance to study the spatial evolution characteristics of different long duration heavy rainfall events. In this study, the precipitation datasets of 545 meteorological stations in China during 1961-2017 years were collected. From two attributes of rainfall amounts and rainfall days, the aggregate characteristics, trend and interannual variability to analyze the spatial pattern of different long duration heavy rainfall and total rainfall events. The results showed that: Firstly, the spatial pattern of different long duration heavy rainfall and total rainfall events over in China were higher in the Southeast China than in the Northwest China. With the increasing of rainfall duration, the spatial distribution of different long duration heavy rainfall events and total rainfall events with higher magnitude gradually converged to the southeastern coastal areas, and the spatial differentiation characteristics tended to decrease. Under the influence of autumn rainfall in the West China, the total rainfall amounts and days in the West China are higher than those in other regions of the same latitude. Secondly, different long duration heavy rainfall amounts and days in China were increasing mainly in the Southeast China, but not in the Northwest China. The trend of total rainfall amounts was increasing in the Southeast and Northwest China, but decreasing in the transitional zone between them. With the increasing of rainfall duration, the decreasing trend zone extended to the Southeast China and Northwest China. The trend of total rainfall days in different duration was increasing in the North China and decreasing in the South China. Thirdly, the interannual variability of heavy rainfall amounts and days over 2 days in China were the greatest in the ecotone between agriculture and animal husbandry and its vicinity, while the interannual variability of heavy rainfall amounts and days over 3 days are high in the Southeast China and low in the Northwest China. The interannual variability of total rainfall amounts and days are mainly high in the South China and low in the North China, and with the increasing of rainfall duration, the region with greater interannual variability expanded from North China to South China.