Explainable ensemble machine learning revealing the effect of meteorology and sources on ozone formation in megacity Hangzhou, China

Megacity Hangzhou, located in eastern China, has experienced severe O3 pollution in recent years, thereby clarifying the key drivers of the formation is essential to suppress O3 deterioration. In this study, the ensemble machine learning model (EML) coupled with Shapley additive explanations (SHAP), and positive matrix factorization were used to explore the impact of various factors (including meteorology, chemical components, sources) on O3 formation during the whole period, pollution days, and typical persistent pollution events from April to October in 2021-2022. The EML model achieved better performance than the single model, with R2 values of 0.91. SHAP analysis revealed that meteorological conditions had the greatest effects on O3 variability with the contribution of 57 %-60 % for different pollution levels, and the main drivers were relative humidity and radiation. The effects of chemical factors on O3 formation presented a positive response to volatile organic compounds (VOCs) and fine particulate matter (PM2.5), and a negative response to nitrogen oxides (NOx). Oxygenated compounds (OVOCs), alkenes, and aromatic of VOCs subgroups had higher contribution; additionally, the effects of PM2.5 and NOx were also important and increased with the O3 deterioration. The impact of seven emission sources on O3 formation in Hangzhou indicated that vehicle exhaust (35 %), biomass combustion (16 %), and biogenic emissions (12 %) were the dominant drivers. However, for the O3 pollution days, the effects of biomass combustion and biogenic emissions increased. Especially in persistent pollution events with highest O3 concentrations, the magnitude of biogenic emission effect elevated significantly by 156 % compared to the whole situations. Our finding revealed that the combination of the EML model and SHAP analysis could provide a reliable method for rapid diagnosis of the cause of O3 pollution at different event scales, supporting the formulation of control measures.

Assessing the cold island effect of urban parks in metropolitan cores: a case study of Hangzhou, China

As the oasis area in the city, urban park plays an extremely prominent role in the regulation and improvement of the urban ecological environment, especially the local thermal environment, and has become one of the significant ways to reduce the urban heat island (UHI) effect. Our study comprehensively considers the maximum cooling distance and spatial continuity of urban parks, takes 30 parks in Hangzhou, and analyzed their influencing factors to comprehensively explore the park cooling effect. The results showed that the land cover shifted drastically during 2000-2020, and the built-up land area increased greatly, which aggravated the UHI effect. The high UHI value of Hangzhou was concentrated in the city center and presented a spreading trend from north to south. Different types of urban parks presented different cold island effects, with comprehensive parks and ecological parks having the largest cooling area, and community parks exhibit better accumulative cooling effect. In addition, the park's own characteristics (perimeter, area, shape index) and inner and surrounding landscapes were significantly correlated with the park's cooling effect (park cooling area and park cooling efficiency). Our study comprehensively considered the cooling effect of parks from the maximum and accumulative perspectives and provides theoretical and practical guidance for the construction and planning of urban parks, thereby enhancing the well-being of urban residents.

Analysis of 13-valent pneumococcal polysaccharide conjugate vaccine among children born in Hangzhou from 2017 to 2021

Background

13-valent pneumococcal polysaccharide conjugate vaccine (PCV13) has been introduced in Hangzhou since 2017, whereas its current immunization state in children is not clear. Therefore, this study aims to describe the PCV13 vaccination distribution among children born in Hangzhou from 2017 to 2021 to provide data for reducing vaccination differences among different populations.

Methods

Descriptive epidemiology was used for data analysis and PCV13 vaccination related information of children was collected from children vaccination management system of Zhejiang Province (ZJCVMS).

Results

Among the 649,949 children born in Hangzhou from 2017 to 2021, 169,230 were vaccinated with an average full course vaccination rate of 26.0%. The full course vaccination rates in 5 years were different (P = 0.000) with an increasing trend (P _fortrend < 0.01). The first dose vaccination rates were different in 5 years (P = 0.000) with an increasing trend (P _fortrend < 0.01). The distribution of age when first dose PCV13 was administered varied, most people at 2 months and least people at 5 months. The full course vaccination rate varied by areas, highest in central urban areas and lowest in remote areas respectively (all P-value < 0.05). Overall, the full course vaccination rate of PCV13 was higher in the registered residence population than the non-registered residence population, which was 136,693 (31.4%) and 32,537 (15.1%) respectively (P = 0.000). The full course vaccination rates were the same between men and women (P = 0.502), which was 87,844 for men (26.0%) and 81,386 for women (26.1%).

Conclusion

Although the number of people who received PCV13 full course vaccination and received the first dose vaccination showed yearly increasing trends in Hangzhou, the full course vaccination rate for the whole population was relatively low. In addition, the PCV13 vaccination rates also differed by geography and household registration status. Measures such as expanding vaccination publicity or including national immunization should be taken to increase vaccination rates and reduce the differences in vaccination among groups with different characteristics.

Population genomics implies potential public health risk of two non-toxigenic Vibrio cholerae lineages

Diarrheal cases caused by non-toxigenic Vibrio cholerae have been reported globally. Lineages L3b and L9, characterized as ctxAB-negative and tcpA-positive (CNTP), pose the highest risk and have caused long-term epidemics in different regions worldwide. From 2001 to 2018, two waves (2001-2012 and 2013-2018) of epidemic caused by non-toxigenic V. cholerae occurred in the developed city of Hangzhou, China. In this study, through the integrated analysis of 207 genomes of Hangzhou isolates from these two waves (119 and 88) and 1573 publicly available genomes, we showed that L3b and L9 lineages together caused the second wave as had happened in the first wave, but the dominant lineage shifted from L3b (first wave: 69%) to L9 (second wave: 50%). We further found that the genotype of a key virulence gene, tcpF, in the L9 lineage during the second wave shifted to type I, which may have enhanced bacterial colonization in humans and potentially promoted the pathogenic lineage shift. Moreover, we found that 21% of L3b and L9 isolates had changed to predicted cholera toxin producers, providing evidence that gain of complete CTXφ-carrying ctxAB genes, rather than ctxAB gain in pre-CTXφ-carrying isolates, led to the transition. Taken together, our findings highlight the possible public health risk associated with L3b and L9 lineages due to their potential to cause long-term epidemics and turn into high-virulent cholera toxin producers, which necessitates a more comprehensive and unbiased sampling in further disease control efforts.

Evaluating supply-demand matching of ecosystem services considering water-energy-food nexus and synergies/trade-offs in the Hangzhou of China

The proposal of water-energy-food nexus provides a new perspective for the supply-demand matching assessment of ecosystem services (ESs). This study aims to evaluate quantitative and spatial matching of supply-demand of ESs considering water-energy-food nexus, and to analyze the synergies/trade-offs between ESs. By taking Hangzhou as a case study, the results showed that supply-demand matching degrees of ESs related to water-energy-food nexus in Hangzhou were all less than zero during the study period, indicating that the supply of ESs in Hangzhou could not meet the local demand. Among them, the gap between supply and demand of water yield gradually narrowed, while the gap between supply and demand of carbon storage/food production gradually widened. From the perspective of supply-demand spatial matching, water yield/food production was dominated by low-low spatial matching area, showing an expanding trend. Carbon storage was mainly characterized by high-low spatial mismatching area, presenting a stable trend. In addition, there were significant synergistic effects between ESs related to water-energy-food nexus. Therefore, this study proposed some supply-demand management policies of ESs from the perspective of water-energy-food nexus to promote the sustainable development of ecosystems and natural resources.

Analysis on the intention and influencing factors of free influenza vaccination among the elderly people aged 70 and above in Hangzhou in 2022

Background

Although influenza vaccination is recommended for people aged 70 and above in Hangzhou, and the vaccine is provided free of charge, the elderly influenza vaccination rate is still low. The purpose of this study was to understand the barriers and motivations of older people in deciding to receive free influenza vaccine through questionnaires.

Methods

The method of stratified random sampling was adopted to take samples. A questionnaire survey was conducted among the elderly aged 70 years and above by face-to-face interview or telephone interview.

Results

A total of 11,663 elderly people aged 70-100 years were successfully and effectively interviewed. 85.98% of the respondent were willing to get the influenza shot, 8.91% were unwilling to get the influenza shot, and 5.11% were on vaccine hesitancy. The people of age of 70-79 years old (hesitancy: OR 70~79 = 0.668, 95%CI: 0.571 0.782, Unwilling: OR 70 - 79 = 0.755, 95%CI: 0.622 0.916), primary school degree or below (hesitancy: OR Secondary school degree or above = 1.467, 95%CI: 1.249 1.724, Unwilling: OR Secondary school degree or above = 1.255, 95%CI: 1.028 1.535), remote areas (hesitancy: OR near central urban area = 2.111, 95%CI: 1.604 2.778, OR central urban area = 2.957, 95%CI: 2.255 3.877, Unwilling: OR near central urban area = 1.687, 95%CI: 1.230 2.313. OR centralurbanarea = 2.218, 95%CI: 1.626 3.027), and convenient for movement (hesitancy: OR yes = 0.494, 95%CI: 0.420 0.580, Unwilling: OR yes = 0.585, 95%CI: 0.480 0.713), understanding of the free vaccine policy (hesitancy: OR understand = 0.204, 95%CI: 0.171 0.245, Unwilling: OR understand = 0.164, 95%CI: 0.128 0.210), influenza knowledge level≥ 13 points (hesitancy: OR ≥13points = 0.628, 95%CI: 0.533 0.739, Unwilling: OR ≥13points = 0.538, 95%CI: 0.437 0.662), influenza vaccine knowledge level≥ 12 points (hesitancy: OR ≥12points = 0.422, 95%CI: 0.350 0.508, Unwilling: OR ≥12points = 0.370, 95%CI: 0.290 0.472), and social trust level ≥ 12 points (hesitancy: OR ≥12points = 0.134, 95%CI: 0.112 0.160, Unwilling: OR ≥12points = 0.220, 95%CI: 0.180 0.269) are more willing to receive free influenza vaccine.

Conclusion

The proportion of elderly people aged 70 and above who are willing to receive free influenza vaccine is high in Hangzhou. But the level of knowledge about influenza, vaccine and trust in society is low. The government should continue to improve the elderly's awareness and trust in society through medical staff, family members, television and radio media, and guide the elderly to actively vaccinate against influenza. Effective publicity should be carried out through the above channels to guide the elderly to actively vaccinate against influenza.

The associations between short-term exposure to ambient particulate matter and hospitalizations for osteoporotic fracture in Hangzhou: a time-stratified case-crossover study

Our results suggested that short-term exposure to particulate matter (PM) might increase the risks of hospitalizations for osteoporotic fractures. Government should protect its citizens by putting in place policies to reduce unhealthy emissions and air pollution.

INTRODUCTION

Osteoporotic fractures are accompanied by high rates of disability and mortality. PM has been linked with many health outcomes. However, few studies focus on the association of short-term exposure to ambient PM and osteoporotic fractures.

METHODS

Data on daily mean air pollution, meteorological factors, and hospitalizations for osteoporotic fractures were collected from Hangzhou, China, 2020-2021. A time-stratified case-crossover design with extended Cox proportional hazards regression was applied to assess the associations between PM and osteoporotic fractures.

RESULTS

Short-term exposure to PM significantly increased the risks of hospitalizations for osteoporotic fractures at cumulative lag days. Per 10 μg/m3 increased in PM2.5 (PM with an aerodynamic diameter ≤ 2.5 μm), PMC (PM with an aerodynamic diameter between 2.5 μm and 10 μm), and PM10 (PM with an aerodynamic diameter ≤ 10 μm) were associated with 5.65% (95% confidence intervals (CIs): 1.29, 10.19), 3.19% (0.11, 6.36), and 2.45% (0.57, 4.37) increase in hospitalizations for osteoporotic fractures, respectively. Significant PM-osteoporotic fracture associations were only observed in females and people aged over 65 years old. For the season, the estimates of PM on hospitalizations for osteoporotic fractures were 6.30% (95% CIs: 1.62, 11.20) in the cold season vs. 2.16% (95% CIs: - 4.62, 9.42) in the warm season for per 10 μg/m3 increase of PM2.5, and 0.99 (95% CIs: - 2.69, 4.80) vs. 6.72% (95% CIs: 0.68, 13.13) for PMC.

CONCLUSIONS

Our study showed PM was positively linked with the risk of osteoporotic fractures. Females and people aged over 65 years old were more susceptible to PM. The adverse impacts of PM2.5 in the cold season and PMC in the warm season were worthy of special attention.

Effect of COVID-19 lockdowns on city-center and suburban housing markets: Evidence from Hangzhou, China

In 2020, governments worldwide enforced lockdowns to contain the spread of COVID-19, severely impeding aspects of daily life such as work, school, and tourism. Consequently, numerous economic activities were affected. Before the COVID-19 outbreak, city-center housing markets in areas surrounding popular tourist attractions performed better than did suburban housing markets because of the output of the tourism industry. This study examines the changes in the performance of city-center and suburban housing markets in regions with popular tourist attractions after the lockdown. Specifically, the dynamics of city-center and suburban housing markets in Hangzhou, where West Lake is located, and the changes in the information transfer between these housing markets after the lockdown are explored. Transaction data from January 1, 2019 to September 30, 2020 are used to perform analysis, in which adjusted housing prices and asking prices are employed to measure market performance and sellers' pricing strategies, and transaction volume and time on the market are used to measure market liquidity and transaction frequency. The results reveal that the effects of lockdowns differ between city-center and suburban housing markets. After the lockdown, a substantial structural change is observed in the suburban housing market; the volatility risk of housing prices decreases substantially, causing an increase in transaction premiums. Housing prices and transaction volume increase in the city-center housing market after the lockdown; this is possibly because of the influence from the overall housing market booms. In addition, because sellers raise their asking prices and the transaction time is extended, the sellers in the city-center housing market are particularly influenced by the disposition effect. This leads to a reversal in the lead-lag relationship between the city center and suburban housing markets in terms of informativeness. Specifically, before the lockdown, the city-center market transfers information to the suburban market, but after the lockdown, the suburban market transfers information to the city-center market. The COVID-19 pandemic has changed the world in many aspects; this paper finds that it will also change the development pattern of the real estate market in different locations.

Simulating Urban Expansion Based on Ecological Security Pattern-A Case Study of Hangzhou, China

Disordered urban expansion has encroached on a large amount of ecological land, resulting in the steady degradation of urban ecology, which has an adverse effect on the sustainable development of the region. An ecological security pattern can effectively control urban expansion, and it is of great significance to balance urban development and ecological protection. In order to analyze the impact of ecological security patterns on urban expansion, Hangzhou was taken as an example, the CA-Markov model and FLUS model were used to simulate the urban expansion pattern in 2030 under the natural development scenario and the ecological security scenario. The results showed that (1) the ecological source area in the study area is 630.90 km² and was mainly distributed in the western mountainous area. There are 14 ecological corridors, primarily composed of valleys and rivers. Ecological nodes are mainly distributed on the north and south sides of the main urban area. (2) From 2000 to 2018, the annual increase index (AI) of construction land decreased in the northeast and southeast directions but increased in the northwest and southwest directions, and in the northeast direction the value was always the highest. Except for the southwest direction, the average annual growth rate (AGR) of construction land in the other directions decreased. At a distance from the city center of 30 km, AI was relatively higher and was increasing, while AGR was declining. At a distance of 30–45 km, both AI and AGR were increasing, indicating that the focus of construction land was moving outwards. (3) From 2018 to 2030, under both natural development scenario and ecological security scenario, construction land would keep expanding, but the construction land area, proportion, AI, and AGR of the latter would both be smaller than the former, indicating that the ecological security pattern can effectively curb urban expansion. Because of a large amount area of ecological sources, the expansion of construction land in the southwest direction would be constrained, especially under the ecological security scenario. The methods and results of this study can provide theoretical and application references for urban planning and green development in metropolises.

How changing grain size affects the land surface temperature pattern in rapidly urbanizing area: a case study of the central urban districts of Hangzhou City, China

Urbanization has led to the rapid and large-scale changes in land use and land cover and has affected the spatial distribution of land surface temperature (LST) in urban areas. Studying the LST pattern and their spatial heterogeneity characteristics at different scales can help understand the dynamic mechanism of the thermal landscape and provide insights into urban ecological planning. We utilized transfer matrixes, landscape metrics, and spatial autocorrelation analyses to study the transfer of LST classes, changes in the LST pattern, and changes in LST clusters with varying grain sizes by taking the central urban districts of Hangzhou City in China as a case study. Results indicate that (1) the transfer proportion of the LST classes increased, except for high-temperature class, and each LST class shifted to the adjacent dominant LST class with the increase in grain size. (2) The landscape metrics remarkably changed as the grain size increased, indicating that the LST pattern was scale-dependent. As the grain size increased, the small patches gradually merged into large patches; the fragmentation, complexity, and ductility of the urban thermal landscapes decreased; and the shape of the patches became simple and regular. (3) The LST pattern exhibited a positive spatial autocorrelation. The area of low-low cluster decreased, whereas that of non-significant clusters substantially increased with the grain size. The area of high-high cluster remained steady when the grain size exceeded 90 m. (4) Patch density, mean patch fractal dimension, clumpiness index, and contagion index exhibited predictable responses to changing grain size, whereas Shannon's diversity and Shannon's evenness indexes showed erratic responses, indicating that the diversity and evenness of the LST pattern were not scale-dependent. (5) The suitable domain of scale for the analysis of LST pattern was (60, 120), and the optimal grain size was 120 m. The selection of domains of scale and optimal grain size need to be determined according to the changes in thermal landscape patterns at different grain sizes and regional environments.

Spatiotemporal variations and reduction of air pollutants during the COVID-19 pandemic in a megacity of Yangtze River Delta in China

In recent decades, air pollution has become an important environmental problem in the megacities of eastern China. How to control air pollution in megacities is still a challenging issue because of the complex pollutant sources, atmospheric chemistry, and meteorology. There is substantial uncertainty in accurately identifying the contributions of transport and local emissions to the air quality in megacities. The COVID-19 outbreak has prompted a nationwide public lockdown period and provides a valuable opportunity for understanding the sources and factors of air pollutants. The three-month period of continuous field observations for aerosol particles and gaseous pollutants, which extended from January 2020 to March 2020, covered urban, urban-industry, and suburban areas in the typical megacity of Hangzhou in the Yangtze River Delta in eastern China. In general, the concentrations of PM_2.5-10, PM_2.5, NO_x, SO₂, and CO reduced 58%, 47%, 83%, 11% and 30%, respectively, in the megacity during the COVID-Lock period. The reduction proportions of PM_2.5 and CO were generally higher in urban and urban-industry areas than those in suburban areas. NO_x exhibited the greatest reduction (>80%) among all the air pollutants, and the reduction was similar in the urban, urban-industry, and suburban areas. O₃ increased 102%-125% during the COVID-Lock period. The daytime elevation of the planetary boundary layer height can reduce 30% of the PM₁₀, PM_2.5, NO_x and CO concentrations on the ground in Hangzhou. During the long-range transport events, air pollutants on the regional scale likely contribute 40%-90% of the fine particles in the Hangzhou urban area. The findings highlight the future control and model forecasting of air pollutants in Hangzhou and similar megacities in eastern China.

[Characteristics and Reactivity of VOCs in Hangzhou During a Typical Photochemical Pollution Episode]

An intensive observation of ambient volatile organic compounds (VOCs) was carried out in Hangzhou, a key city in the Yangtze River Delta, during a typical photochemical pollution episode from September 14-23, 2018. The analysis results of 80 effective samples showed that the average concentration of 122 compounds of VOCs was (59.5±19.8)×10^-9 during the observation period, and oxygenated VOCs (OVOCs) were the most abundant component. The assessment results of atmospheric reaction activity with ozone formation potential (OFP) showed that the average value of OFP was 145×10^-9 during the observation period, of which alkenes and carbonyl compounds were the most abundant components. The chemical reactivity of VOCs in Hangzhou was equivalent to acrylonitrile. Based on the positive matrix factorization (PMF) model, five major sources of VOCs in Hangzhou were identified, including secondary formation (25.2%), combustion and industrial processing (27.2%), solvent use (17.3%), biogenic sources (9.2%), and vehicular exhaust (21.2%). The results can provide guidance for further understanding of VOC characteristics and the basis for scientific prevention and control measures in Hangzhou.

Unexpected rise of ozone in urban and rural areas, and sulfur dioxide in rural areas during the coronavirus city lockdown in Hangzhou, China: implications for air quality

The outbreak of coronavirus named COVID-19, initially identified in Wuhan, China in December 2019, has spread rapidly at the global scale. Most countries have rapidly stopped almost all activities including industry, services and transportation of goods and people, thus decreasing air pollution in an unprecedented way, and providing a unique opportunity to study air pollutants. While satellite data have provided visual evidence for the global reduction in air pollution such as nitrogen dioxide (NO₂) worldwide, precise and quantitative information is missing at the local scale. Here we studied changes in particulate matter (PM_2.5, PM₁₀), carbon monoxide (CO), NO₂, sulfur dioxide (SO₂) and ozone (O₃) at 10 urban sites in Hangzhou, a city of 7.03 million inhabitants, and at 1 rural site, before city lockdown, January 1-23, during city lockdown, January 24-February 15, and during resumption, February 16-28, in 2020. Results show that city lockdown induced a sharp decrease in PM_2.5, PM₁₀, CO, and NO₂ concentrations at both urban and rural sites. The NO₂ decrease is explained by reduction in traffic emissions in the urban areas, and by lower regional transport in rural areas during lockdown, as expected. SO₂ concentrations decreased from 6.3 to 5.3 μg m^-3 in the city, but increased surprisingly from 4.7 to 5.8 μg m^-3 at the rural site: this increase is attributed both to higher coal consumption for heating and emissions from traditional fireworks of the Spring Eve and Lantern Festivals during lockdown. Unexpectedly, O₃ concentrations increased by 145% from 24.6 to 60.6 μg m^-3 in the urban area, and from 42.0 to 62.9 μg m^-3 in the rural area during the lockdown. This finding is explained by the weakening of chemical titration of O₃ by NO due to reductions of NO_x fresh emissions during the non-photochemical reaction period from 20:00 PM to 9:00 AM (local time). During the lockdown, compared to the same period in 2019, the daily average concentrations in the city decreased by 42.7% for PM_2.5, 47.9% for PM₁₀, 28.6% for SO₂, 22.3% for CO and 58.4% for NO₂, which is obviously explained by the absence of city activities. Overall, we observed not only the expected reduction in some atmospheric pollutants (PM, SO₂, CO, NO₂), but also unexpected increases in SO₂ in the rural areas and of ozone (O₃) in both urban and rural areas, the latter being paradoxically due to the reduction in nitrogen oxide levels. In other words, the city lockdown has improved air quality by reducing PM_2.5, PM₁₀, CO, and NO₂, but has also decreased air quality by augmenting O₃ and SO₂.

Urban expansion simulation and scenario prediction using cellular automata: comparison between individual and multiple influencing factors

Quantifying the contribution of driving factors is crucial to urban expansion modeling based on cellular automata (CA). The objective of this study is to compare individual-factor-based (IFB) models and multi-factor-based (MFB) models as well as examine the impacts of each factor on future urban scenarios. We quantified the contribution of driving factors using a generalized additive model (GAM), and calibrated six IFB-DE-CA models and fifteen MFB-DE-CA models using a differential evolution (DE) algorithm. The six IFB-DE-CA models and five MFB-DE-CA models were selected to simulate the 2005-2015 urban expansion of Hangzhou, China, and all IFB-DE-CA models were applied to project future urban scenarios out to the year 2030. Our results show that terrain (DEM) and population density (POP) are the two most influential factors affecting urban expansion of Hangzhou, indicating the dominance of biophysical and demographic drivers. All DE-CA models produced defensible simulations for 2015, with overall accuracy exceeding 89%. The IFB-DE-CA models based on DEM and POP outperformed some MFB-DE-CA models, suggesting that multiple factors are not necessarily more effective than a single factor in simulating present urban patterns. The future scenarios produced by the IFB-DE-CA models are substantially shaped by the corresponding factors. These scenarios can inform urban modelers and policy-makers as to how Hangzhou city will evolve if the corresponding factors are individually focused. This study improves our understanding of the effects of driving factors on urban expansion and future scenarios when incorporating the factors separately.

Responses of Ecosystem Services to Urbanization-Induced Land Use Changes in Ecologically Sensitive Suburban Areas in Hangzhou, China

Ecologically sensitive suburban areas provide important ecosystem services and protect urban ecological security because of their multiple functions in natural and human systems. The research on the ecological environment effects of land use activities in ecologically sensitive suburban areas is important in guiding the healthy and sustainable development of cities. Taking the west suburbs of Hangzhou in China as a case study, we quantified land use changes from Landsat satellite imagery and calculated the value of ecosystem services using the well-established equivalent factor table for land use/cover change (LUCC) and ecosystem services value (ESV). The impacts of LUCC on the ecological environment were analyzed using the transfer matrix of land use and coefficient of elasticity. Results revealed the following. (1) The total ESV in the western suburban area of Hangzhou decreased from $109.95 million in 2000 to $87.09 million in 2016. Moreover, the ESV of gas regulation, climate regulation, soil formation and protection, as well as biodiversity conservation presented a large decrease of more than 25%, especially between 2010 and 2016. (2) The spatial distribution of ESV was high in the west and low in the east. The regions with a significant reduction in ESV were mainly distributed in the eastern town of Wuchang and in Jincheng Town located in the midwest valley. (3) Industrial agglomeration activities in the ecologically sensitive suburban area emerged as the primary factor influencing ESV for various land uses. The elasticity indicator for assessing the responses to ESV changes relative to LUCC showed that 1% of the land conversion in this area resulted in average changes in ESV of 4.1% after the establishment of the industrial agglomeration area. (4) The increase in construction land was associated with a significant decrease in forest area because of the policy of cultivated land requisition⁻compensation balance and development strategies for low-slope hilly lands. Consequently, the ESV in the ecologically sensitive suburban areas rapidly declined.

[Characteristics of and Factors Affecting Atmospheric CO2 Concentration in Hangzhou]

In situ measurement of CO₂ concentration(volume fraction) was carried out in both urban and rural areas of Hangzhou from August 2015 to September 2016. The characteristics of CO₂ concentration at the urban site were compared to those at the rural site, and the factors affecting CO₂ concentration in Hangzhou were analyzed via wind direction, weekday-weekend difference in CO₂ concentration, and evolution of CO₂ concentration during the G20 summit. The results revealed that the diurnal variation of CO₂ concentration in both the urban and rural areas presented a single peak curve most of the time, which resulted from the daily evolution of plant photosynthesis/respiration and atmospheric transport conditions. The diurnal variation of the difference in CO₂ concentration observed at the urban and rural sites showed a bimodal peak curve, because anthropogenic emissions played a more important role. The diurnal amplitude of CO₂ concentration in rural area was higher than that in urban area in spring and summer, but lower in autumn. The seasonal variation of CO₂ concentration in both the urban and rural areas showed the same trend, with higher values appearing in winter and spring and lower values in summer. The difference in CO₂ concentration observed at the urban and rural sites reached its highest level in winter, and dropped to its lowest in summer. The wind direction induction of high CO₂ concentration was consistent with the location of the surrounding urban areas. A weekday-weekend difference in CO₂ concentration was observed in Hangzhou, especially in urban area, as traffic emissions had an impact on the weekday-weekend difference in diurnal distribution of CO₂ concentration. The average volume fraction of CO₂ in urban area of Hangzhou was 9.3×10^-6 higher than that in rural area, and the reduction of anthropogenic emissions during the G20 summit reduced the atmospheric CO₂ concentration effectively, especially in urban area.

[Emission Inventory and Pollution Characteristics of Industrial VOCs in Hangzhou, China]

For the 2022 Asian Games, a series of major events were held in Hangzhou City in 2016 at the international summit, where research on VOC emission inventories, especially on industrial VOCs, has attracted the attention of local residents and management departments. By taking a bottom-up approach, 3518 enterprises in more than 30 industries in Hangzhou were investigated and an industrial VOCs emission inventory for Hangzhou was established. Based on the data on regional emissions, emissions intensity, and spatial distribution, the industrial VOCs emissions in Hangzhou were systematically analyzed. The VOC emissions from industrial sources in Hangzhou amounted to 36839.5 tons in 2015. Printing and reproduction of recorded media; chemical raw materials and chemical products manufacturing; and the metal, textile, rubber, and plastics products industries were the most important sources of industrial VOC emissions in Hangzhou. The largest industrial VOC emissions were measured in Xiaoshan District, followed by Fuyang District and Dajiangdong Industrial Agglomeration Area. The highest VOC emissions intensity was detected in Fuyang District, Jiande City, and Lin'an City. Industrial VOC emissions were mainly concentrated in more intensive industrial areas in Xiaoshan, Fuyang, Yuhang, and Dajiangdong Districts.

[Perfluorinated Compounds in Snow from Downtown Hangzhou, China]

Snow samples were collected from the snow event on January 20-22, 2016 from 11 sites in downtown Hangzhou to explore the occurrence of sixteen perfluorinated compounds (PFCs) in the atmosphere. All samples were prepared by solid-phase extraction with Oasis WAX cartridges and analyzed using ultra performance liquid chromatography interfaced with tandem mass spectrometry (UPLC-MS/MS). The results showed that seven medium- and short-chain PFCs including C₄ and C₈ perfluorinated sulfonates (PFSAs) and C₄-C₆, C₈, and C₉ perfluorinated carboxylic acids (PFCAs) were detected in the snow samples. Total PFC concentrations ranged from 2.85 to 35.1 ng·L^-1, whereas perfluorooctanoic acid (PFOA) dominated, with ranges of 2.15-23.0 ng·L^-1, and perfluorooctane sulfonate (PFOS) was detected at lower levels, ranging from 0 to 0.46 ng·L^-1. As compared to the results from other studies, the PFOA concentrations of the study region were at mid-level and the PFOS concentrations were relatively low. The spatial distribution of PFCs varied, and the pollutant concentrations of the snow samples from the sampling sites located in the urban areas were higher than those in the rural areas. The greatest total PFC concentrations were detected in Fuyang, whereas the lowest concentrations were detected in Jiande and Chun'an. In this study, the high concentrations of PFCs dominated by PFOA that were measured in the Hangzhou snow samples emphasize the importance of atmospheric wet deposition as one of the sources of PFC contamination in this ecological system and should be addressed. The occurrence of PFCs in the air, indicated by their presence in the snow, suggests that the atmospheric environment may be an important contributor in human and ecological exposure to PFCs by local residents.

[Assessment on heat island effect based on urban regulatory planning.]

With the improved legal status of urban planning, regulatory detailed planning is playing an increasingly important role in guiding land leasing and regulating the spatial structure of urban construction. Understanding the effect of regulatory planning indices on urban heat island (UHI) and evaluating the heat environment performance of indices combination at the scale of regulatory planning unit and plot are of great significance for assessing the thermal environment effect of regulatory planning quantitatively and putting forward action plans to mitigate heat island impacts. In this study, we assessed impacts of main urban regulation indices and their combinations on UHI by analyzing land surface temperature (LST) data, retrieved through the thermal infrared remote sensing image (Landsat8 TIRS), using statistical and GIS spatial analysis methods. Results indicated that the indices of green ratio, plot area, building density and building height all had a significant impact on LST at regulatory planning unit level. By generating 3D models, we found the regulation index combination with round 30% of green ratio, and 2.5-3.5 of floor area ratio had the minimal impact on urban thermal environment at regulatory plot. The outcomes provided a new perspective on the rational improvement of urban regulatory planning.

RECENT TRENDS IN GENDER RATIO AT BIRTH IN HANGZHOU, CHINA

INTRODUCTION

Higher than normal sex ratios at birth in China have been reported since the early 1980's. This study aimed to investigate recent trends in sex ratio at birth in Hangzhou, capital of Zhejiang Province in southeast China.

METHODS

Information on selected maternal and birth-related characteristics was extracted from the Hangzhou Birth Information Database for all pregnant women who delivered live births during 2005-2014. The sex ratios at birth were calculated after excluding infants with missing data on gender and those born with ambiguous genitalia.

RESULTS

A total of 478,192 male births and 430,852 female births were recorded giving an overall ratio of 111.0. The sex ratio at birth was almost constant at around 110.7 during the period 2005-2008, followed by an increase to the peak at 113.1 in 2010 and then declined back to 109.6 in 2014.

CONCLUSION

The gender ratio at birth in Hangzhou remained unbalanced for the past decade.