North Jiangsu Research Articles

A method for velocity modeling in volcanic rock zone that integrates the amplitude envelope attribute and grid tomography: application to data from the North Jiangsu Basin

A method for velocity modeling in volcanic rock zone that integrates the amplitude envelope attribute and grid tomography: application to data from the North Jiangsu Basin

Extracting waterline and inverting tidal flats topography based on Sentinel-2 remote sensing images: A case study of the northern part of the North Jiangsu radial sand ridges

Muddy tidal flats with landforms vary widely over space and time. The evolution of tidal flats topography has had a significant impact on the region. Therefore, there is a need to develop methods for rapidly and accurately characterizing tidal flats topography. This study applied thresholding segmentation (TS), machine learning, and two image classification methods to Sentinel-2 remote sensing images to extract the instantaneous waterline of the northern part of the North Jiangsu Radial sand Ridges (NJRSR). Tidal level data at specific time intervals were obtained using the Delft3D and TPXO9 models, after which tidal flats topography inversion was conducted. As a result, varied among the different classification methods, with the K-Nearest Neighbors (KNN) algorithm producing the optimal waterline extraction. Furthermore, the accuracy of tidal level simulation was improved by employing Delft3D software and constructing a scaled-down model of the study area. Comparisons with Delft3D model simulations of tidal levels with observations at three tide gauge stations yielded accuracies of 17.5 cm, 18.5 cm and 17.9 cm, this result showed that the establishment of the tidal level model can enhance the accuracy of tidal flats Digital Elevation Model (DEM) inversion. In fact, the combined application of the KNN algorithm and Delft3D model within retrieval of tidal level provided the most accurate topographic inversion, with an average error of 0.297 m, which was reduced to 0.292 m after median filtering, and the results indicated a trend of southward erosion in the tidal flats in the study area, with a turning point roughly located in the southern part of Doulong Port. The results of this study can help improve the future monitoring of dynamic changes in intertidal wetland topography and the conservation and development of tidal flats areas.

Differences and Causal Mechanisms in the Lithospheric Thermal Structures in the Cratons in East China: Implications for Their Geothermal Resource Potential

The thermal structure of the lithosphere is key to understanding its thickness, properties, evolution, and geothermal resources. Cratons are known for their low heat flow and deep lithospheric roots. However, present-day cratons in East China have geothermal characteristics that are highly complex, with variable heat flow values, diverging from the typical thermal state of cratons. In this study, we conducted a detailed analysis of the geothermal geological background of the cratons in East China, summarizing the thermal state and tectono-thermal processes of different tectonic units, calculating the temperature at various depths, and discussing differences in temperature and thermal reservoirs at different depths. The observed lithospheric thermal thickness within the North Jiangsu Basin and the Bohai Bay Basin is notably reduced in comparison to that of the Jianghan Basin and the Southern North China Basin. The phenomenon of craton destruction during the Late Mesozoic emerges as a pivotal determinant, enhancing the geothermal resource prospects of both the Bohai Bay Basin and the North Jiangsu Basin. Our findings contribute significantly to the augmentation of theoretical frameworks concerning the origins of heat sources in global cratons. Furthermore, they offer invaluable insights for the methodical exploration, evaluation, advancement, and exploitation of geothermal resources.

Monitoring the Water Quality Distribution Characteristics in the Huaihe River Basin Based on the Sentinel-2 Satellite

Remote sensing technology plays a crucial role in the rapid and wide-scale monitoring of water quality, which is of great significance for water pollution prevention and control. In this study, the downstream and nearshore areas of the Huaihe River Basin were selected as the study area. By utilizing spectral information from standard solution measurements in the laboratory and in situ water quality data matched with satellite spatiotemporal data, inversion models for total phosphorus (TP) and ammonia nitrogen (NH3-N) water quality parameters were developed. The validation results using field measurements demonstrated that the inversion models performed well, with coefficients of determination (R2) of 0.7302 and 0.8024 and root mean square errors of 0.02614 mg/L and 0.0368 mg/L for total phosphorus and ammonia nitrogen, respectively. By applying the models to Sentinel-2 satellite images from 2022, the temporal and spatial distribution characteristics of total phosphorus and ammonia nitrogen concentrations in the study area were obtained. The ammonia nitrogen concentration ranged from 0.05 to 0.30 mg/L, while the total phosphorus concentration ranged from 0.10 to 0.40 mg/L. Overall, the distribution appeared to be stable. The southern region of the Guan River estuary showed slightly higher water quality parameter concentrations compared to the northern region, while the North Jiangsu Irrigation Main Canal estuary was affected by the dilution of river water, resulting in lower concentrations in the estuarine area.

Quantitative provenance study of sediments in the coastal tidal flats of central Jiangsu based on grain-size End-Member analysis

The coastal mudflats in central Jiangsu Province are influenced by the sediment supply from the Yangtze River and the abandoned Yellow River. However, the sources of sediment in this area have yet to be confirmed, and quantitative studies have been limited. In this study, we addressed this gap by obtaining sediment core samples with lengths of approximately 100 cm from Dongtai and Sheyang, respectively, on the central coast of Jiangsu Province in 2018. The sediment sources were identified and quantitatively evaluated using a grain-size end-member(EM) model. The findings revealed that (1) Sheyang was decomposed into five EMs, with EMs 1-3 originating from the abandoned Yellow River, EM 4 originating from the Yangtze River and the North Jiangsu radial sand ridges (NJRSR), and EM 5 originating from the NJRSR. Over a century scale, the abandoned Yellow River contributed 73.91% to sediment deposition in Sheyang, while the Yangtze River and the NJRSR contributed 26.09%. (2) Dongtai was decomposed into six EMs, with EMs 1-4 originating from the abandoned Yellow River, EM 5 originating from the Yangtze River, and EM 6 originating from the Yangtze River and the NJRSR. Over a century scale, the abandoned Yellow River contributed 70.55% to sediment deposition in Dongtai, and the Yangtze River and the NJRSR contributed 29.45%. (3) On a temporal scale, the contribution of the abandoned Yellow River to sediment deposition on the central mudflats of Jiangsu Province showed an increasing trend. Spatially, the contribution of the abandoned Yellow River to sediment deposition decreased from north to south. (4) There were significant changes in the sediment sources of Sheyang and Dongtai at the depths of 56 cm and 60 cm, respectively, which both experiencing an increased sediment supply from the abandoned Yellow River. In Dongtai, the sediment on the southern side had increased contributions from the abandoned Yellow River due to a reduction in the sediment supply from the Yangtze River. In Sheyang, the sediment on the northern side had increased contributions from the abandoned Yellow River due to the introduction of Spartina alterniflora, despite no actual changes in the sediment sources.

Formation mechanism of NO2 distribution heterogeneity at different spatial scales

NO2 is one of the main pollutants in the atmospheric environment, which can directly or indirectly cause harm to human health. Jiangsu province is economically developed and densely populated, and the conflict between economic development and ecological environment protection is more prominent, which causes its mean annual NO2 concentration to be higher than other neighboring provinces. The study takes the formation mechanism of NO2 concentration distribution heterogeneity at different spatial scales as the research object. By using OMI satellite remote sensing data and NO2 concentration ground monitoring data in Jiangsu Province from 2015 to 2020, the paper studies NO2 concentration distribution heterogeneity at macroscopic and microscopic scales, respectively, to analyze the formation mechanism. The results show that: (1) The spatial distribution characteristics of NO2 concentration obtained based on the analysis of two data sources have good consistency, with the overall performance of high NO2 concentration in the south of Jiangsu where the concentration of NO2 column reached 16.3 × 1015 molec/cm 2 and the monitoring concentration reached 46.3μg/m3, while the concentration of NO2 in central Jiangsu is relatively low, with average concentrations of 6 × 1015 molec/cm 2 and 26μg/m3. (2) Under the macroscopic spatial scale, the average NO2 column concentration in the south of Jiangsu is 9 × 1015 molec/cm 2 higher and the monitoring concentration is 15μg/m3 than that in the north of Jiangsu; natural factors such as temperature are the important influencing factors for the heterogeneity of NO2 concentration distribution under this scale. (3) At the microscopic spatial scale, NO2 concentration is 5–10% higher in industrial concentrations in southern Jiangsu, some heating cities in northern Jiangsu, and industrial parks in northern Jiangsu. In addition, NO2 concentration decreases gradually with distance from this area; anthropogenic factors such as population density, GDP, and car ownership are important factors to influence the heterogeneity of NO2 concentration distribution at this scale. Based on the above findings, the paper proposes to adjust the industrial structure, limit the number of high energy-consuming and high-emission enterprises, and develop seasonal emission reduction measures.

The rise and fall of the leprosy clinic in Ru Gao in the North of Jiangsu in the period of the Republic of China

The North of Jiangsu was a traditional area for leprosy in Chinese history. In the period of the Republic of China, one of the largest leprosy clinics in China was established in Ru Gao (Jugao) with the help of Chinese and foreign charitable organizations, the Chinese central government and some squires. It was the only large clinic for leprosy in the North of Jiangsu. It was officially opened in 1924, attached to the Presbyterian Church hospital, and was closed in 1927 after the breakout of the civil war. It reopened in May 1933, hosted by a leprologist, Lee S. Huizenga. Ru Gao (Jugao) leprosy clinic treated around 1,000 lepers in the North of Jiangsu with medicines and language communication. The establishment of the leprosy clinic made a historical contribution in terms of preventing leprosy from spreading to Shanghai. It closed in the spring of 1938 because of the invasion of the Japanese military.

Regional Energy–Economy–Environment Coupling Coordinated Development System Driven by Carbon Peaking and Carbon Neutralization over 13 Cities in Jiangsu Province

It is important to explore the energy–economy–environment (3E) coupling mechanism for building a sustainable economy in the context of carbon-peaking and carbon-neutralization strategy. Based on the DPSIRM (driving force–pressure–state–influence–response–management) theoretical model, this paper constructs the evaluation system of 3E coupling-coordinated development, takes the carbon-neutral and sustainable-development strategy and spatiotemporal heterogeneity into account in the index system, and constitutes the energy–economy–environment and carbon-neutral strategy–sustainable development–space (3E3S) strategic-development model. This paper uses the coupling-coordination-degree model to measure the coordinated development of 3E in Jiangsu from 2010 to 2020 and analyzes the time-sequence evolution and spatial-difference evolution characteristics of the coupling-coordinated development. The results show that (1) when the coupling coefficient of 3E was in a stable and high-level coupling state and the correlation degree of each system was high, the coupling-coordination degree increased from 0.4 in 2010 to 0.7 in 2020; the level of coordination of 3E coupling transited from the initial maladjustment recession to the intermediate coordinated development and moved towards high-quality coordinated development. (2) In addition, at the beginning, the development level of southern and central Jiangsu was generally higher than that of northern Jiangsu; in the middle term, the overall development was in a stage of barely coordinated development. The urban difference between northern and central Jiangsu was relatively high, and the level in southern Jiangsu was generally high; in the later stage, the overall development was in a well-coordinated stage. The development of southern Jiangsu was relatively saturated, gradually approaching the stage of high-quality coordinated development. Roughly speaking, in 2010, the average level of coupling coordination degree of South Jiangsu, Central Jiangsu, and North Jiangsu was 0.5, 0.4, and 0.3, respectively; by 2020, it had developed to 0.9, 0.8, and 0.7, respectively, and the development level rose steadily despite regional differences. The level of coupling coordination generally increased from north to south. Therefore, strengthening the strategic-development awareness of 3E and establishing and improving the government consultation mechanism according to local conditions will help decision-makers to formulate effective regional sustainable-development and carbon-neutral strategies and form a coordinated-development strategy of 3E3S in Jiangsu.

Environmental and provenance change since MIS 2 recorded by two sediment cores in the central North Jiangsu Plain, East China

In order to reveal the evolution of sediment provenance and paleoenvironment of the central North Jiangsu Plain (NJP) since marine isotope stage 2 (MIS 2), we analyzed lithology, accelerator mass spectrometry (AMS) 14C dating, macrofossils and foraminifera, grain size, and geochemical compositions of sediments from two sediment cores (Core M and Core Y) recovered in the northern side of the Yangtze River. Our results show that fluvial environments prevailed in the central NJP during MIS 2, followed by alternations of coastal-marsh environments and shallow-bay environments in north central NJP and coastal-marsh environments in south central NJP during MIS 1. Provenance analysis suggests a major change in sediment provenance from the Yangtze River to the Yellow River at early MIS 1 in north central NJP; these Yellow River sediments might be transported from previously deposited sediments by strong tidal currents and intense waves to this area or be a reflection of a southward shift of the Yellow River during this period. However, the Yangtze River-derived sediments dominated the south central NJP since MIS 2. The depositional succession and sediment supplies since MIS 2 were dominantly controlled by sea-level fluctuations, regional geomorphic patterns, shift of the rivers, etc.

Entrepreneurial agents, asset modification and new path development in rural China: The study of Gengche model, Jiangsu Province

This paper, through a case study of the Gengche Township in north Jiangsu (Subei), unveils how a less-favored region breaks out of the old industry path of waste recycling and processing and embarks on a green new one specializing in E-commerce. Drawing on key concepts in evolutionary economic geography, we propose a conceptual framework that addresses how entrepreneurial agents enact the processes of asset modification at multiple scales for new green path development in a rural context. Based on on-site interviews and survey, our analysis reveals that rural lead entrepreneurs and state elites pioneered and opened windows of opportunities for change, then legitimized by the state with wider support towards old path breaking. These state interventions enforce the bottom-up process of new green path development. In this process, extra-regional knowledge linkages and assets help facilitate the E-commerce development. It is concluded that rural new path development processes are not only contingent on local pre-conditions but are tempo-spatially dependent on collective actions of entrepreneurial multi-actors in identifying, transplanting and modifying local and non-local assets. The Gengche case demonstrates that rural new green path development in China requires the formation of strong system-level rural agency engaging in multi-scalar asset modification.

Chemical Characterization, Source Identification, and Health Risk Assessment of Atmospheric Fine Particulate Matter in Winter in Hangzhou Bay

PM2.5 is an important pollutant which affects air quality and human health. In this study, chemical components (water-soluble inorganic ions, organic carbons (OC), elemental carbons (EC), and elemental metals) and health effects were analyzed in wintertime in a suburban area in Hangzhou Bay. OC and SNA (sulfate, nitrate, and ammonium) contributed 76.2% to local PM2.5. NH4+ existed mainly in the form of (NH4)2SO4 and NH4NO3. Seven sources were resolved from PMF analysis, namely secondary inorganic aerosol (31.8%), vehicle exhaust (19.5%), industry mixed with coal combustion (16.3%), crustal dust (9.5%), biomass burning (9.4%), sea salt (8.7%), and the leather industry (4.8%). Potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analysis were applied to study regional transport in this region. Secondary inorganic formation was enhanced from the air plume from the northwest, especially from north Jiangsu Province. The results of the health risk assessment of associated metals indicated the higher potential of Cr and Mn to cause noncarcinogenic effects in children. A significant carcinogenic risk was observed for all people of Cr emitted from the leather industry. Our results showed the chemical characterization and sources of PM2.5 in a suburban region, the health effects of which should be addressed in future policies to safeguard public health, especially in the leather industry.

Poverty Stories of rural households in China: The case of North Jiangsu

After decades of rapid economic growth and massive rural-to-urban migration, rural poverty in China has been largely alleviated. Existing literature has highlighted the crucial role played by non-farm employment in the rural population's escape from poverty. However, despite some engagement in non-farm employment, a huge population in rural China remains poor. Why rural households remain poor in spite of non-farm employment has not been sufficiently explored by scholars. To fill the research gap, this paper explores the underlying mechanisms of poverty among the poor rural population, based on a recent questionnaire survey (n = 2,822) conducted in rural North Jiangsu in China. Our multinomial logistic regression model and OLS regression model show that education is positively associated with the likelihood of engaging in non-farm sectors. Relatively low education attainment of working-age household members (secondary education and below) restricted the earnings from non-farm activities, reducing the likelihood of escaping poverty. Supporting higher education for their children is often a heavy burden for poor non-agricultural rural households, driving them into the poverty trap. The results also show that significant family events, such as severe illness and children's college enrollment, have kept rural households poor, even if some household members have participated in non-farm activities through migration or working in the local non-rural sector. In addition, instead of being looked after, some apparently dependent family members (the elderly) undertake agricultural activities and domestic work to support the out-migration of the labor force in poor rural households to enable household wealth accumulation. The findings suggest that policymakers should implement a series of reforms, especially regarding improvement in health insurance and education and the economic development in the local areas (incl. rural areas and nearby towns) to deal with rural poverty.

Labour Costs on the Vegetables: A Research on the location effect on salaries in Jiangsu Province, China

ABSTRACT: In this study, the labour requirement and labour cost of common vegetable cultivation were investigated to help agricultural enterprises and family farms establishing reasonable “working hour” management systems in Jiangsu Province. The labour requirement of each step of three type of producers, agriculture enterprises, family farms, and private vegetable growers, in three regions in Jiangsu Province, named north, middle and south Jiangsu, was investigated by on-site observation or questionnaire survey during 2018 and 2019. The labour cost of each step and each vegetable was counted according to the labour requirement and the salary level. The results indicated that “residue cleaning”, “soil preparation and bedding”, “plant regulation”, “auxin treatment of tomato flowers” and “hand pollination” accounted for higher proportions of labour cost amongst the entire vegetable culture process. No significant differences in the labour requirements of the investigated vegetables were reported amongst three regions in Jiangsu Province. However, the order of labour cost is south Jiangsu > north Jiangsu > middle Jiangsu, due to the salary difference amongst three regions. Watermelon, broccoli and chive are more suitable for growing by agricultural enterprises since they have relatively low unit labour and high prices. We established a method to calculate and analyze labour requirement and cost of vegetable production in Jiangsu Province, which also may be instructive for other regions. In addition, our results provided useful data for various vegetable producers to improve their labour management.

Suitability assessment of carbon dioxide storage sites in sedimentary basins

The assessment of the suitability of CO2 storage sites is the basis for large-scale deployment of Carbon Capture Utilization and Storage (CCUS) projects. However, the research on the suitability of CO2 in sedimentary basins is relatively lagging behind in China. Previous studies have focused on CO2 storage sites, while social, economic and environmental factors are ignored. This paper takes counties and districts as the research objects, and conducts a comprehensive evaluation of onshore sedimentary basins. The research results show that: (1) Onshore sedimentary basins cover 839 counties (districts) in China, of which 318 counties (districts) are prohibited from implementing CO2 storage; 286 counties (districts) are Class II environmental risk areas; The suitable and suitable areas include 217 and 19 counties (districts) respectively, accounting for about 45% of the total onshore storage area. (2) The suitable and relatively suitable areas are mainly distributed in the Tarim Basin, the central and northern parts of the Songliao Basin, the northwestern part of the Ordos Basin, the northeastern part of the Erlian Basin, and the central and southern parts of the Bohai Bay Basin. Forbidden areas and general suitable areas are mainly distributed in Sichuan Basin, Jianghan-Dongting Basin, North Jiangsu Basin, northeastern Bohai Bay Basin, and southern Songliao Basin. This study establishes a method for assessing the suitability of CO2 storage sites, and gives a suitable area for CO2 storage in China, which provides a method and basis for the site selection of large-scale deployment of CCUS projects in China.

Exploration Process and Genesis Mechanism of Deep Geothermal Resources in the North Jiangsu Basin, East China: From Nothing to Something

Geothermal resources, as an important member of clean renewable energy, of which the exploration, development, and utilization of geothermal resources, especially deep geothermal resources, are of great significance for achieving carbon peaking and carbon neutrality. Taking the North Jiangsu Basin (NJB) as an example, this paper reviews the exploration process of deep geothermal resources in the basin and presents the latest results. The study shows that the NJB is a typical “hot basin” with an average heat flow value of 68 mW/m2. In this region, the deep geothermal resource favorable areas in the NJB are mainly distributed in the depressions, in particular those near the Jianhu uplift, i.e., the Yanfu depression and the Dongtai depression. In addition, the genesis mechanism of the deep geothermal resource favorable area in the NJB is best explained by the “two stages, two sources” thermal concentration, that is, “two stages” means that the transformation of the lithospheric thermal regime are caused by the late Mesozoic craton destruction in East China, and the Cenozoic lithospheric extension; these two tectono-thermal events together lead to the deep anomalous mantle-source heat (the first source), and the upper crustal-scale heat control is mainly caused by thermal refraction (the second source). Overall, this case study underlines new ideas of understanding the geothermal genesis mechanism in East China, which can guide for the exploration and development of deep geothermal resources at the basin scale.

Factors controlling iodine enrichment in a coastal plain aquifer in the North Jiangsu Yishusi Plain, China

Iodine is an essential micronutrient in the human diet and an appropriate human iodine intake level is important for population health. Excessive iodine intake is often associated with high iodine groundwater which serves as an important drinking water source in many regions. This study aims to identify the source and key hydrogeochemical processes for iodine accumulation and mobility in the groundwaters of the Northern Jiangsu Yishusi Plain. Combined hydrogeochemical and statistical analyses, specifically random forest modeling and factor analysis, were used to explore the mechanisms affecting the spatial distribution of iodine. The concentration of iodine in the investigated groundwaters was found to vary widely and to range between 4.8 and 4750 μg/L, with 48.9% of the total samples (674) exceeding the threshold value of 100 μg/L for toxic exposure, as defined by the Chinese high‑iodine standard guideline. High iodine concentrations are shown to mainly occur in the marine plain and the shallow aquifer associated with the floodplains of the Old Yellow River. The marine or lagoons-facies sediments were identified as the most plausible iodine source. In addition, mixing of groundwater with paleo-seawater might also have played a role in the coastal area. In contrast, the flood sediments of the Old Yellow River are shown to be an unlikely source. However, they serve as a cover layer that favored the development of reducing hydrogeochemical conditions that can trigger iodine mobilization via the reductive dissolution of iron oxides and the degradation of organic matter. Slow groundwater flow rates also appear to favor iodine release from sediments.

Quantitative geochemistry as a provenance indicator for surface sediments in the north Jiangsu radial sand ridges (NJRSR) in the South Yellow Sea, East China

The North Jiangsu radial sand ridges (NJRSR) are typical sedimentary bodies distributed along the continental margin of China. Historically, the Yellow and Changjiang Rivers transported terrigenous sediments into the sea, depositing them in the study area. However, the provenance of the sediments in the NJRSR is not conclusively understood. In this study, the grain sizes and major elemental geochemistry of 33 surface sediment samples were investigated to discern the provenance of the sediments in the NJRSR. The results indicate that the sedimentary components are primarily silt (53.60%), sand (35.60%), and clay (10.80%). The grain size (Mz) of the NJRSR coastal surface sediments was 2.5–8.5 Φ, with an average of 5.1 Φ, and had high SiO2 and Al2O3 contents (on average, SiO2 and Al2O3 accounted for >68%). The statistical results of the geochemical analyses were reflected in the control on sediment elemental components by riverine transport in the study area, which were then used to divide the study area into three sedimentary provinces. Elemental ratios (Mg/Al, Fe/Al, K/Al) were used to discern the provenance of the NJRSR surface sediments, indicating that the inputs from the Yellow and Yangtze rivers are the dominant sediment sources in the study area. Using the inverse model, a quantitative estimation revealed that average sediment contributions of the Abandoned Yellow and Yangtze rivers were 67.4% and 32.6%, respectively. In addition, modern current systems play an important role in controlling sediment transport from the Abandoned Yellow and Yangtze rivers to the NJRSR. This study demonstrates the importance of geochemistry for quantitatively determining the provenance of the NJRSR, which is especially useful for quantitatively investigating Earth surface processes in global shelf-marginal seas.

Levels and ecological risk of heavy metals in the surface sediments of tidal flats along the North Jiangsu coast, China

We investigated the contamination levels of nine heavy metals (Mn, Pb, V, Cr, Co, Ni, Cu, Zn, and As) in 153 surface sediment samples collected along five tidal flats on the North Jiangsu coast, China. The spatial distributions of most heavy metals gradually decreased from the northern Sheyang region to the southern Jianggang region, while slightly increasing in the Rudong region. Principal component analysis indicated that Co, Ni, Cu, Zn, and As were mainly derived from the natural environment, V and Cr were mainly derived from human activities. Additionally, Mn and Pb influenced by both natural and human sources. The geo-accumulation index and the contamination factor indicated that heavy metal contamination in the sediments exhibited little to no pollution levels. The potential ecological risk index exhibiting low ecological risks. Meanwhile, the mean probable effect level quotient values indicating slight toxicity. Cr and Ni were the major contributors to toxicity.

Effects of small irrigation facilities on hydrological connectivity of ditches in North Jiangsu Plain, China.

Hydrological conditions in the plains irrigation area are complex, which are strongly affected by small irrigation facilities and human management. In this study, the connectivity index of ditch network and the influence index of rural small irrigation facilities were constructed to quantitatively analyze the hydrological connectivity of a typical plain irrigation area, Fudong irrigation area, in north Jiangsu Province. The self-organizing feature map (SOM) analysis method was used to identify the effects of small irrigation facilities on the spatial heterogeneity of ditch network structure connectivity. The results showed that the hydrological structure connectivity differed in different regions of Fudong. The connectivity in the north of the irrigation area was the best, but the worst in the central and southern part of the irrigation area. There were 876 pumps, 633 gates and 2420 culverts in the study area. Without the effects of small irrigation facilities, there were 13 villages with poor hydrological structure connectivity and 48 villages with good and best hydrological structure connectivity. Under the effects of small irrigation facilities, the number of villages with poor connectivity was reduced to 8, while the number of villages with good and best connectivity was increased to 53. Due to the influence of gates and culvert, the hydrological connectivity of 26 villages in Fudong became poor. The hydrological connectivity of 39 villages had been enhanced due to the existence of pump.

Climatic Risk Assessment of Winter Wheat Aphids in Northern China

Northern China is a main winter wheat production area and plays an important role in ensuring food security. Wheat aphids, as one kind of main agricultural pest, threaten wheat production. Based on wheat aphids disaster and prevention data, planting area and yield loss of wheat, growth period of winter wheat, and daily meteorological data at 561 observation stations from 1958 to 2018 in 8 main wheat production provinces of northern China, relationships between surface meteorological factors and the occurrence area of wheat aphids for every province in North China and Huanghuai area are fully analyzed using methods of correlation analysis, principal component analysis and stepwise regression analysis in various time-periods from last December to 10 June. Eight key meteorological factors which affect the occurrence area of wheat aphids in North China and 6 key meteorological factors for Huanghuai area are determined. The climate disaster indices of wheat aphids are established based on the normalized key meteorological factors and validated in 8 provinces. Furthermore, climatic risk aspects are assessed to explore the occurrence tendency of winter wheat aphids in northern China. The frequencies of different-level decadal climate disasters are taken as hazard index, the ratio of occurrence area of wheat aphids to the wheat-sown area is defined as vulnerability index, and the ratio of controlled area to occurrence area is calculated to measure the disaster prevention and mitigation capability.Comprehensive risk index is built by integrating hazard, vulnerability, disaster prevention and mitigation capability indexes to assess risk development trend in decades. The results show that the climatic hazard for wheat aphids tends to increase gradually and there are significant differences in different decades. The vulnerability for wheat aphids tends to be severe over time.The disaster prevention and mitigation capability for wheat aphids tends to improve gradually especially in the 1990s, and the trend slows down since 2001. The comprehensive climatic risk has been more severe and their scopes of the highest risk have been larger since the 1990s. The climatic risk is highest in Beijing, Tianjin, central-south Hebei, part of north Shandong. And it's the second highest in most of Shandong, north Henan, eastern and southern Shanxi, and north Jiangsu area, where effective measures should be taken to reduce the detriment of wheat aphids.