Hangzhou Bay Area Research Articles

Measuring the Urban Particulate Matter Island Effect with Rapid Urban Expansion.

Rapid urbanization has posed numerous negative impacts on the environment, including fine particulate matter (PM2.5) pollution. However, quantitative investigations of the PM2.5 concentration trends over an urban-rural gradient at the local level are still lacking. The urban particulate matter island (UPI) effect, representing the phenomenon that high particle concentrations in urban areas are gradually attenuated to surrounding areas, was adopted and modified in this paper to study the Hangzhou Bay area from 2000 to 2015. We found the following: (1) every urban area in the Hangzhou Bay area experienced rapid expansion, especially during 2000–2005; (2) more than half of the urban areas suffered UPI problems, and these urban areas had relatively high and stable UPI intensity (UPII) values, although the UPI footprint (UPIFP) values decreased with urban expansion; and (3) urban areas could be divided into three categories: plain areas, hilly areas and the junction of plains and hills, and the probability of the UPI effect varied significantly for different categories. This paper can compensate for the lack of research on the UPI effect at the local level and provide scientific evidence for air pollution control during urban agglomeration planning.

Linking ecosystem services trade-offs, bundles and hotspot identification with cropland management in the coastal Hangzhou Bay area of China

Understanding the co-occurrence of multiple ecosystem services within farming systems and how they are associated across space are relatively new topics. Quantifying ecosystem services and their interactions as dependent on cropland management can help to formulate a more effective and sustainable land use management system. However, current academic efforts and cropland management practices based on the perspective of ecosystem services bundles and tradeoffs remain limited, especially in developing countries. This paper aimed to integrate ecosystem services into cropland protection and functional zoning. Taking Cixi County in the Hangzhou Bay area, China, as the case study area, five typical ecosystem services (food supply, carbon sequestration, hydrological regulation, soil fertility and recreation potential) delivered by croplands and their correlations were quantitatively assessed. The results demonstrated a heterogeneous spatial pattern of multiple ecosystem services and diverse interactions between them, which depended on regional specific conditions and agricultural activities. Further, we adopted the framework of ecosystem services bundles as a planning tool to support the spatial strategy of cropland management. Cropland protection priority and functional zoning were determined by hotspot analysis and clustering algorithms, respectively. The croplands in Cixi were classified into three protection grades and a zoning scheme comprising four functional types with policy guidelines was proposed based on the spatial cluster results. The integrative approach used in this study is applicable to supplement the current cropland management actions by incorporating the perspective of ecosystem services tradeoff and bundles.

Smart sampling strategy for investigating spatial distribution of subsurface shallow gas pressure in Hangzhou Bay area of China

Subsurface shallow gas has been widely discovered in coastal areas across continents at buried depths of approximately 10–100 m. Its presence poses a significant hazard and risk during underground construction, e.g., risk of explosion and fire when using tunnel boring machines for subway construction. Therefore, it is important to determine the spatial distribution of the shallow gas pressure during site investigation for subsequent hazard analysis and mitigation. In engineering practice, the gas pressure is often sparsely measured at a limited number of locations using modified cone penetration tests (CPTs) owing to time, budget, resource, and technical constraints. There are no rational or quantitative methods available for the planning of site investigation of gas pressure. Therefore, it is important to determine ways to properly and efficiently plan a site investigation of the shallow gas pressure during geotechnical site investigation (e.g., how to determine the required number of modified CPTs (i.e., the sample size) and their corresponding optimal locations). A smart sampling strategy is developed for planning of site investigation in this study that uses innovative data analytic methods (e.g., Bayesian compressive sampling, BCS, and information entropy) to automatically determine sample size and optimal sampling location for gas pressure characterization. The proposed smart sampling strategy is illustrated using numerical examples. The results show that the proposed smart sampling strategy performs reasonably well.

Research on Regional Management and Industry Planning Based on Innovative Elements: A Case Study of Hangzhou Bay Area

In the past decade, the economic development surrounding Hangzhou Bay has been in the ascendant, but the economic advantages of the regional growth alliance are not prominent. This paper analyzes the regional management and development mechanism of bay area industry from the perspective of innovation elements. Taking Hangzhou bay area as an example, this paper analyses the innovation foundation and spatial differentiation. The empirical results show that center effect, spillover effect and absorption effect caused the disorder of innovative elements. The integration of innovation elements, opening environment, industrial pattern and spatial structure will be effective ways to improve the regional cooperation.

Risk zoning of typhoon disasters in Zhejiang Province, China

Abstract. In this paper, typhoon simply means tropical cyclone. As risk is future probability of hazard events, when estimated future probability is the same as historical probability for a specific period, we can understand risk by learning from past events. Based on precipitation and wind data over the mainland of China during 1980–2014 and disaster and social data at the county level in Zhejiang Province from 2004 to 2012, a study on risk zoning of typhoon disasters (typhoon disasters in this paper refer to affected population or direct economic losses caused by typhoons in Zhejiang Province) is carried out. Firstly, characteristics of typhoon disasters and factors causing typhoon disasters are analyzed. Secondly, an intensity index of factors causing typhoon disasters and a population vulnerability index are developed. Thirdly, combining the two indexes, a comprehensive risk index for typhoon disasters is obtained and used to zone areas of risk. The above analyses show that southeastern Zhejiang is the area most affected by typhoon disasters. The annual probability of the occurrence of typhoon rainstorms >50 mm decreases from the southeast coast to inland areas, with a maximum in the boundary region between Fujian and Zhejiang, which has the highest risk of rainstorms. Southeastern Zhejiang and the boundary region between Zhejiang and Fujian provinces and the Hangzhou Bay area are most frequently affected by extreme typhoon winds and have the highest risk of wind damage. The population of southwestern Zhejiang is the most vulnerable to typhoons as a result of the relatively undeveloped economy, mountainous terrain and the high risk of geological disasters in this region. Vulnerability is lower in the cities due to better disaster prevention and reduction strategies and a more highly educated population. The southeast coastal areas face the highest risk of typhoon disasters, especially in the boundary region between Taizhou and Wenzhou cities. Although the inland mountainous areas are not directly affected by typhoons, they are in the medium-risk category for vulnerability.

Exploring the driving forces of farmland loss under rapidurbanization using binary logistic regression and spatial regression: A case study of Shanghai and Hangzhou Bay

The unprecedented accelerating urbanization in China has led to a sharp decline in cultivated land. In this paper, the dynamics of farmland patterns during three periods (1994–2003, 2003–2009, 2009–2015) in the Shanghai and Hangzhou Bay (SHB) area are exhibited by dynamic change models and standard deviation ellipse analysis. Additionally, further detection of the determinants of farmland loss is carried out, through a combination of binary logistic regression and spatial regression models. Seven proximate driving factors are selected: distance to water; distance to coastline; distance to city center; and distance to roads (provincial road, national road, highway, and railway). The results suggest that Shanghai experienced the most drastic changes in farmland during the study periods across the whole city agglomeration, and this impact spatially diffused to its adjacent cities. Meanwhile, the transportation routes, especially for provincial road and national road, are quantitatively verified to be the most prominent determinants with a negative influence. Our research highlights that the serious farmland loss should be addressed in highly urbanized area. Furthermore, there is an urgent need for the government to formulate efficient policies for farmland protection and to curb the spread of this phenomenon in the urban agglomeration.

LED Industrial Spatial Structure and its Evolution Trend in Hangzhou Bay Area, China

The numbers of spatial scale structural dimensions and associated structural dimensions in the light emitting diode (LED) industry in Hangzhou Bay Area, China since 2002 were estimated through the fractal method for the prediction of the future evolution trend of the industry. We found that the spatial structure of the LED industry in that area is of strong monopoly but tends to be generally optimal and stable. The morphology in which the main enterprises concentrate in a linear space contributes to the interactions among the enterprises; future spatial structure of LED industry in Hangzhou Bay Area will be a stable state. Changes in external environments and the interaction between internal industrial factors constitute the basic dynamic mechanism for the formation and evolution of LED industrial spatial structure in the Hangzhou Bay Area.

Urban expansion and vegetation changes in Hangzhou Bay area using night-light data

Based on DMSP/OLS night-light data and MODIS NDVI data for 2000, 2007 and 2013, this paper studied on characteristics of urban expansion and vegetation changes in built-up areas with nighttime light threshold extraction and vegetation index analysis using remote sensing and GIS. Results showed that the threshold method could realize the effective extraction of urban land information. In general, the urban built-up area expanded along with Hangzhou Bay in V model, and there were three expansion patterns: polygon pattern, linear pattern and point pattern. Obvious spatio-temporal variations in different cities were found in the rate and the dynamic degree of urban expansion and the compactness of urban morphology. The whole study area showed a decreasing trend in the rate and the dynamic degree of urban expansion, while the average compactness of urban morphology declined after the rise. Vegetation conditions became better in built-up areas except Jiaxing in 2000-2007, but it became worse in all cities in 2007-2013. Urban expansion had a ne-gative effect on the vegetation change in built-up areas in 2000-2013.

Wetland ecosystem health assessment through integrating remote sensing and inventory data with an assessment model for the Hangzhou Bay, China

Due to rapid urbanization, industrialization and population growth, wetland area in China has shrunk rapidly and many wetland ecosystems have been reported to degrade during recent decades. Wetland health assessment could raise the public awareness of the wetland condition and guide policy makers to make reasonable and sustainable policies or strategies to protect and restore wetland ecosystems. This study assessed the health levels of wetland ecosystem at the Hangzhou Bay, China using the pressure-state-response (PSR) model through synthesizing remote sensing and statistical data. Ten ecological and social-economic indicators were selected to build the wetland health assessment system. Weights of these indicators and PSR model components as well as the normalized wetland health score were assigned and calculated based on the analytic hierarchy process (AHP) method. We analyzed the spatio-temporal changes in wetland ecosystem health status during the past 20years (1990–2010) from the perspectives of ecosystem pressure, state and response. The results showed that the overall wetland health score was in a fair health level, but displayed large spatial variability in 2010. The wetland health score declined from good health level to fair health level from 1990 to 2000, then restored slightly from 2000 to 2010. Overall, wetland health levels showed a decline from 1990 to 2010 for most administrative units. The temporal change patterns in wetland ecosystem health varied significantly among administrative units. Our results could help to clarify the administrative responsibilities and obligations and provide scientific guides not only for wetland protection but also for restoration and city development planning at the Hangzhou Bay area.

Dissolved iron distribution and organic complexation in the coastal waters of the East China Sea

The distribution of total dissolved iron and organic ligands in the coastal waters of the East China Sea, especially in the Yangtze River estuary, was investigated using competitive ligand equilibration–adsorptive cathodic stripping voltammetry (CLE–ACSV) with 2,3-dihydroxynaphthalene (DHN) as the competing ligand.The seasonal variation of total dissolved iron (D-Fe) and its organic ligands (Lt) were observed in spring and autumn. The average D-Fe concentration in both surface and bottom waters in spring was higher than that in autumn. With respect to the horizontal distribution of D-Fe and Lt content, the highest values were observed in the estuary stations located in the Yangtze River Estuary and the Hangzhou Bay area and the lowest values were observed in offshore stations. The average surface D-Fe concentration of estuary stations in spring and autumn was 39.4±26.6 (the standard deviation) nmol/L and 20.5±11.0nmol/L, respectively. The average bottom D-Fe concentrations of estuary stations in spring and autumn were 76.1±58.6nmol/L and 78.5±39.0nmol/L, respectively.Higher surface Lt concentrations were observed during the spring. The average surface Lt concentrations of estuary stations in spring and autumn were 40.0±26.8 and 23.2±7.8nmol/L, respectively. The concentration of D-Fe and Lt in the bottom water was higher than that observed in surface water and exhibited less seasonal variability. Strong ligands were observed in spring estuary surface water. The average surface logK'FeL values in spring and autumn were 12.9±0.8 and 11.7±0.5, respectively. The total ligand concentration in this study was generally in excess of the dissolved iron, particularly in autumn at offshore stations. Higher excess organic ligand concentrations were also generally observed in the upper water column compared to bottom waters in autumn.

Distribution of major and trace elements in surface sediments of Hangzhou Bay in China

The Inductively Coupled Plasma Optical Emission Spectrometer was used to analyze sediment samples collected from the Hangzhou Bay to determine major and trace elemental concentrations. Based on these concentrations, the study area can be classified into three geochemical provinces. Province I covers the northern Hangzhou Bay area and contains high concentrations of Al2O3, Fe2O3, MgO, Na2O, K2O, MnO, Cr, Cu, Ni, Pb, V, Co and Zn. Province III is located in the western Hangzhou Bay, near the Qiantang River mouth, and contains high concentrations of SiO2, Na2O, P2O5, TiO2, Cr, Sr, Zr. Province II is located in the middle and eastern Hangzhou Bay, with the medium concentrations of major and trace elements. The results also demonstrate that the grain size is the dominating factor controlling the spatial variations of elemental concentrations, and the Changjiang River (Yangtze River) and Qiantang River sediments play an important role in the distribution of these elements. Anthropogenic impact on heavy metal concentrations (especially Cr, Sr and Zr) can be detected in the surface sediments near the Qiantang River mouth.

Exploration methods for late Quaternary shallow biogenic gas reservoirs in the Hangzhou Bay area, eastern China

Commercial accumulations of shallow biogenic gas have been widely found in the world. The successful development and exploitation of shallow gas is dependent on using suitable technology to effectively prospect for this kind of resource. Shallow biogenic gas reservoirs, buried less than 120 m (393.7 ft), have been discovered and successfully exploited in the Hangzhou Bay area, northern Zhejiang Province, eastern China. In this study, we describe the methods used for the exploration of shallow gas, including cone penetration test (CPT), shallow shear-wave seismic data, soil-gas radon analysis, microbiological prospecting, and electromagnetic surveying. The CPT is effective in helping to determine stratigraphic divisions and correlations, especially reservoir identification. Dense CPTs are useful for both the preliminary exploration and enlarging a known gas field. Shallow shear-wave seismic profiles identify the top surface of a gas-bearing sand bed, which shows a strong reflecting boundary. The reflection will sharply decline where the gas-bearing sand body pinches out. Thus, a gas-bearing sand body can be outlined. The area of gas reservoirs can further be determined by high soil-gas radon content over the boundary of the gas accumulation. Methane-consuming bacteria can act as an indicator for the presence of methane within the gas-bearing area. Electromagnetic methods can aid in determining whether there is gas in the sand bodies and in determining the thickness of the gas layer.

Geology and formation mechanism of late Quaternary shallow biogenic gas reservoirs in the Hangzhou Bay area, eastern China

Late Quaternary shallow biogenic gas reservoirs have recently been discovered and exploited in the coastal Hangzhou Bay area, northern Zhejiang Province, eastern China. The river in this area strongly incised the underlying old beds during a period of glacial maximum, which resulted in the formation of the Qiantangjiang and the Taihu incised valleys. These incised valleys were filled with fluvial sediments and buried by marine sediments during the postglacial period. Late Quaternary strata of the incised-valley area are composed of four sedimentary facies in ascending order: fluvial floor facies (IV), flood-plain facies (III), sublittoral-marine bay facies (II), and estuarine facies (I).All commercial gas fields occur in flood-plain sand bodies of incised valleys. The bodies are buried 3060 m (98197 ft) deep and are 3.07.0 m (9.823 ft) thick, with a maximum thickness of more than 10 m (33 ft). They are surrounded by impermeable clays. Rapid deposition of overlying sublittoral-marine bay sediments supplied not only abundant gas sources, but also good preservation conditions. The main hydrocarbon sources are dark gray clays of the flood-plain facies and gray muds of the sublittoral-marine bay facies. Sediments of both facies have organic carbon content generally more than 0.4%. Shallow biogenic gas fields and deep gas fields require vastly different drilling and completion techniques. Drilling and completion costs are much lower for the biogenic gas fields.Quaternary incised valleys and flood plains other than Hongzhou Bay in coastal areas of eastern China are promising targets of further exploration for shallow biogenic gas.