Pearl River Delta Area Research Articles

The Single-Scattering Albedo of Black Carbon Aerosols in China

Black carbon (BC) aerosols have attracted wide attention over the world due to their significant climate effects on local and global scales. BC extinction aerosol optical thickness (AOT), scattering AOT, and single scattering albedo (SSA) over China are systematically studied based on the MERRA-2 satellite reanalysis data from 1983 to 2022 in terms of the spatial, yearly, seasonal, and monthly variations. The extinction and scattering AOTs of BC show similar spatial distribution, with high values in eastern and southern China, generally as opposed to BC SSA. A decrease in BC extinction and scattering AOTs has been documented over the last decade. The mean BC extinction AOT, scattering AOT, and SSA over China are 0.0054, 0.0014, and 0.26, respectively. The BC SSA showed small variations during 1983–2022, although a high BC extinction AOT and scattering AOT have been seen in the last two decades. During different decades, the seasonal patterns of BC extinction and scattering AOTs may differ, whereas the BC SSA shows seasonal consistency. Significant monthly variations in the BC SSA are seen over four decades, which are in agreement with their seasonal patterns. The mean BC extinction AOTs are 0.037, 0.033, 0.023, and 0.0054, whereas the average BC scattering AOTs are 0.0088, 0.0082, 0.0060, and 0.0014 in the Pearl River Delta (PRD), Yangtze River Delta (YRD), Beijing–Tianjin–Hebei (BTH) region, and Tarim Basin (TB), respectively. It is interesting to see that BC SSA values in the TB region are generally higher than those over the PRD, YRD and BTH areas, whereas the reverse is true for BC extinction and scattering AOTs. This study provides references for further research on black carbon aerosols and air pollution in China.

Surface exchange of HONO over paddy fields in the Pearl River Delta, China

Soil can release HONO, affecting atmospheric oxidation and tropospheric chemistry processes through the production of hydroxyl radicals (OH) and nitric oxide (NO) via photolysis. However, there is limited field observation of HONO flux, hindering a comprehensive understanding of its emission mechanisms. In this study, a dual open-top chambers system combined with a long path absorption photometer (LOPAP) was employed to measure HONO flux from paddy fields in the Pearl River Delta area (PRD), showing good reproducibility and effectivity to mitigate greenhouse effects. The average HONO flux was 0.77 ± 0.72 ng N m−2 s−1, displaying a diurnal pattern of higher fluxes during the day and lower fluxes at night, similar to previous flux observations. A strong linear correlation between the HONO flux with the product of NO2 and solar radiation (R2 = 0.90) suggests that surface reactions involving NO2 and sunlight may dominate HONO production from the paddy fields, surpassing microbial activity within the soil. Given the diversity of field environments, more field observations are needed for assessing emission rates of HONO and understanding underlying mechanisms.

Effect of cloud chemistry on seasonal variations of sulfate and its precursors in China

Cloud chemistry is of paramount importance in the secondary production of atmospheric aerosols, influencing the spatial-temporal distribution of gases and aerosols in the atmosphere. Using WRF/CUACE (China Meteorological Administration Unified Atmospheric Chemistry Environment), this study assesses the seasonal impacts of cloud chemistry on the concentrations of SO2, sulfate, as well as two oxidizers, H2O2 and O3, in the most east-central areas of China, including four key pollution zones (the North China Plain (NCP), the Yangtze River Delta (YRD), the Pearl River Delta (PRD), and the Sichuan Basin (SCB)). Near the surface, H2O2-oxidation was the dominant pathway for cloud chemistry in four key pollution zones in four seasons. H2O2 consumption is most pronounced in summer, especially in the SCB and NCP, while O3 consumption peaks in autumn, particularly in the PRD and southeastern coastal areas. While at higher altitudes, oxidation by O3 and H2O2 is compatible with the cloud chemistry process. Near the surface, cloud chemistry consumes SO2 ranging from approximately 0.1 ppb–5.0 ppb, resulting in the generation of about 6.0–25.0 μg m−3 of sulfate. Higher SO2 reduction and sulfate increase are in both summer and winter, especially for the SCB and NCP in summer, and the SCB in winter. Vertically, the cloud chemistry process primarily concentrates its influence on SO2 and sulfate concentrations below 5 km, particularly within the turbulent zone of the troposphere below 2 km in all the four pollution zones and four seasons. The most notable seasonal variation occurs in the NCP compared to other zones. This study also shows that cloud chemistry effectively improves the seasonal simulation accuracy of SO2 and sulfate, resulting in improved correlation and a notable reduction in RMSE.

High-Resolution 3D Shallow S-Wave Velocity Structure Revealed by Ambient-Noise Double Beamforming with a Dense Array in Guangzhou Urban Area, China

Abstract Shallow velocity structure surveys are very important for urban seismic hazard monitoring and risk assessment. Ambient-noise tomography provides an ideal way to obtain urban fine structure. In this study, we obtained a high-resolution 3D VS model of the metropolitan areas of the Pearl River Delta (PRD) using the ambient-noise double-beamforming method with a dense nodal array. The new model reveals shallow structures that correlate well with surface geological features, with low-velocity anomalies in fault depressions and high-velocity anomalies in fault uplifts. Our findings reveal detailed fault geometries and basin characteristics of the PRD. The Guangzhou–Conghua fault emerges as a prominent velocity boundary, playing a significant role in controlling the development and subsidence of the Longgui basin. The Xinhui–Shiqiao fault and Shougouling fault are identified as major faults that control the formation and evolution of depressions in the PRD. The basin structures in the PRD are classified as semigraben basins controlled by synsedimentary faults. The long axes of the sub-basins align with the strike of the major faults, and the deposit centers are located in close proximity to these faults. Furthermore, our investigation reveals low-velocity anomalies along the faults, suggesting the existence of pre-existing faults facilitating heat transfer and fluid/melt migration from the deep crust. Our results provide new constraints on the geometric structure of the sedimentary basins and fault systems in the PRD area, thereby contributing to urban seismic hazard assessment and offering valuable insights into potential geothermal resources.

The influence of enterprise dormitories on the urban integration of migrant workers in China: an exploration of two distinct migration stages of individual and family migration and the differences between them

The role of enterprise dormitories as the main living arrangements of Chinese migrant workers who are registered as rural residents but make their living in cities in pursuit of urbanisation cannot be ignored. However, the existing research on living spaces and the urban integration of migrant workers lacks sufficient focus on enterprise dormitories. Using the logit model to examine representative data on the Pearl River Delta and Yangtze River Delta areas and applying a national dataset taken from the China Migrants Dynamic Survey, we analyse how enterprise dormitories affect the urban integration of migrant workers across the different migration stages in this paper. The research results reveal that there are two migration stages in the urban integration of migrant workers. In the individual migration stage, based on the production target, enterprises accommodate migrant workers as a means of reducing their labour costs by increasing the labour time input of migrant workers. Moreover, in the family migration stage, enterprise dormitories are conducive to the low-cost integration of migrant workers into urban society, but they negatively affect further family migration because of the insufficient family living space that they provide. This research offers the intellectual foundation required for not only resolving the contradiction between the family reunification of migrant workers and their employment situation but also for the optimisation of housing policy.

Spatiotemporal variations and driving forces analysis of ecosystem water conservation in coastal areas of China

China's coastal zones, characterized by their ecological vulnerability and significant economic growth, demand effective water conservation management. Such management is pivotal not only for safeguarding water resources but also for ensuring ecological stability and promoting sustainable socio-economic development. In this study, based on the water balance model, the spatiotemporal dynamics of water conservation in the ecosystems of China's coastal areas from 2001 to 2021 were characterized by three dimensions: overall, zonal, and raster. The results show that: ① the distribution pattern of ecosystem water conservation in China's coastal areas from 2001 to 2021 is “high in the south and low in the north”, with a total amount of 117.726 billion m3/a, with the Pearl River Delta and Southwest Coastal Areas as the main high-value areas, and the overall water conservation and its capacity show a “ decreasing-rising-decreasing” pattern. The overall water conservation and its capacity show a fluctuating trend of “falling-rising-falling”. Additionally, water conservation capacity varied significantly among different vegetation types and across marine-terrestrial gradients, with the highest capacity recorded in evergreen coniferous forests and areas situated 140 km from the coastline. ②From 2001 to 2021, the water conservation capacity of China's coastal ecosystems exhibited significant temporal patterns and spatial differentiation along the marine-terrestrial gradient. The research suggests that these patterns of change are intricately linked with the stages of regional development strategies and ecological construction within these coastal zones. ③In China's coastal areas, a mere 11.63 % of the rasters showed significant changes in water conservation, dominated by highly significant and significant increases, mainly in the Southeast Coastal Area, the Pearl River Delta and Southwest Coastal Areas, and the Bohai Bay Coastal Area. This included areas such as the Yangtze River Delta silty coastal plain area, the Bohai Bay silty coastal plain area, the sandy silt coastal hilly terrace area of western Guangdong and Guinan, and other China coastal protection forest system construction projects. ④ Water conservation function within China's coastal ecosystems demonstrates a profound interconnection with both natural and socio-economic determinants. Natural elements such as elevation, slope, and precipitation positively correlate with water conservation metrics. Conversely, evapotranspiration and temperature are inversely related to conservation outcomes. In terms of social factors, water conservation has a significant negative correlation with GDP density and population density, with the highest negative correlation with the GDP2 density.

Advancing shipping NOx pollution estimation through a satellite-based approach.

Estimating shipping nitrogen oxides (NOx) emissions and their associated ambient NO2 impacts is a complex and time-consuming task. In this study, a satellite-based ship pollution estimation model (SAT-SHIP) is developed to estimate regional shipping NOx emissions and their contribution to ambient NO2 concentrations in China. Unlike the traditional bottom-up approach, SAT-SHIP employs satellite observations with varying wind patterns to improve the top-down emission inversion methods for individual sectors amidst irregular emission plume signals. Through SAT-SHIP, shipping NOx emissions for 17 ports in China are estimated. The results show that SAT-SHIP performed comparably with the bottom-up approach, with an R2 value of 0.8. Additionally, SAT-SHIP reveals that the shipping sector in port areas contributes ∼21 and 11% to NO2 concentrations in the Yangtze River Delta and Pearl River Delta areas of China, respectively, which is consistent with the results from chemical transportation model simulations. This approach has practical implications for policymakers seeking to identify pollution sources and develop effective strategies to mitigate air pollution.

Embeddedness at varying depths: interactions between rural e-commerce entrepreneurs and China’s local politico-economic contexts

Using data collected from face-to-face interviews, on-site observations, and other archival records, this article builds upon the mixed embeddedness framework to develop four concepts—hyper-, hypo-, governed, and dis-embeddedness—to capture the varied depths of rural e-commerce entrepreneurs’ embeddedness within multiple levels of contexts in response to four different local politico-economic conditions in China. This study finds that entrepreneurs in coastal province interiors are hyper-embedded in multiple levels of contexts that are interlinked through personal ties, while in the Pearl River Delta area, entrepreneurs’ hypo-embeddedness within multiple levels of contexts both enables and constrains their abilities to develop rural e-commerce businesses. Moreover, in the Yangtze River Delta area, in addition to entrepreneurs making their own efforts, local governments mobilize a variety of resources to affect the size, depth, and dynamics of entrepreneurs’ embeddedness, while in central and western provinces, entrepreneurs have not completely embraced the e-commerce economy because they face weak politico-economic conditions. This article further explores policy changes that would help entrepreneurs take full advantage of rural e-commerce in China.

Efficiency evaluation and redundancy analysis on low carbon economic development in Guangdong Province.

Since 2020, China has been dedicated to the goal of "carbon peak and carbon neutrality" in the international community, demonstrating its commitment to energy conservation and emissions control. In 2021, in response to the guidance of the State Council, all provinces in China included the creation of a low-carbon economic system as one of their key development goals. This paper aims at investigating the low-carbon economic development efficiency and the redundancy of inefficient areas of Guangdong Province by using the three-stage DEA-Malmquist index model. Panel data of 21 cities from 2011 to 2020 in Guangdong Province were selected. Results revealed that the low-carbon economic development efficiency in the whole province rises, but the growth rate has slowed down in the past three years. Pearl River Delta area is better-developed in low-carbon economy than others. It is recommended to improve the efficiency of scale, make use of environmental advantages and develop energy-saving and emission reduction technologies.

Assessing urban rooftop PV economics for regional deployment by integrating local socioeconomic, technological, and policy conditions

Assessing the urban rooftop photovoltaic (PV) economics is important for scaling up rooftop PVs for rapid decarbonization. In this study, socioeconomic, technological, and policy factors were integrated into a rooftop PV economic assessment. This comprehensive method was applied to 21 cities in the Guangdong province of China, in combination with local real parameters. The results show that, with higher urbanization levels, electricity tariffs, and PV self-consumption rates, cities in the Pearl River Delta area generally had better economic performance in terms of both economic scale and profitability. They accounted for 75% of the total rooftop PV potential in Guangdong Province and had an internal rate of return (IRR) as high as 14.6–19.2% for Commercial and Industrial buildings (C&I), and 9.9–15.9% for residential buildings (R). Socioeconomic, technological, and policy factors jointly affect the economic performance and create a promising future for Guangdong rooftop PVs. It is projected that the IRR of current worst performing cities will grow by 4.9–5.8, and 4.4–5.9 percentage points, and the payback period will be shortened by 5.8–6.7 and 3.4–4.1 years by 2030 for R and C&I buildings, respectively. Among the three factors, technological advancement had the most significant long-term effect, followed by socioeconomic development. Policy factors play an important role in alleviating short-term cash flow pressure. Integrating the three factors in the assessment provides us with a more comprehensive picture of how urban rooftop PV economics will evolve and a better idea of how to prioritize rooftop PV development. Suggestions for prioritizing the deployment of rooftop PV systems in Guangdong by 2030 were provided.

Evaluation and optimization of ecological landscape pattern for urban agglomeration in the Pearl River Delta, China.

The evaluation and optimization of landscape ecological pattern has important implications for the accurate improvement of forest quality and high-quality urban development in the Pearl River Delta urban agglomeration. Based on the "one map" data and digital elevation model data of forest resource management in 2021, we evaluated and optimized landscape ecological pattern of the Pearl River Delta urban agglomeration by morphological spatial pattern analysis and minimum cumulative resistance model. The results showed that there were 435861 patches in the Pearl River Delta urban agglomeration that could be used as ecological source area, covering an area of 7346.60 km2 and accounting for 13.4% of the Pearl River Delta area. Thirty patches were selected as the ecological source area of the study area by using the area and patch importance index, covering an area of 2792.59 km2 and accounting for 5.1% of the Pearl River Delta area. The overall natural environment of the Pearl River Delta urban agglomeration was excellent. The ecological resistance level was small. The peripheral ecological resistance was low. The core ecological resistance was high. There was still a large room for adjustment of stand types and landscape patterns, which should be optimized by adjusting the composition and spatial distribution of tree species. The ecological network of the Pearl River Delta urban agglomeration was optimized with 30 ecological sources, 103 key ecological corridors, and 95 ecological nodes. The improvement rates of the optimized probability of connectivity index and integral index of connectivity index were 297.5% and 695.1%, respectively. The optimization results could effectively connect the ecological sources and spread the ecological service functions of ecological sources.

Characteristics, Origins, and Atmospheric Processes of Amines in Fine Aerosol Particles in Winter in China

AbstractAmines affect particle formation, aerosol acidity, nitrogen cycle, and climate change. However, little is known about the temporal and spatial differences in the composition, source, and formation process of amines in fine particulate matter (PM2.5) in different regions of China. Seven amines (amine salts) were investigated in PM2.5 collected in the Yangtze River Delta (YRD, Shanghai and Nanjing), Pearl River Delta (PRD, Guangzhou), northern China (Xi'an and Haerbin), and background (Puding) areas in winter 2017–2018. Methylamine was the dominant amine species at the YRD, northern China, and background sites, while diethylamine dominated at the PRD site; moreover, the mass concentration and fraction of diethylamine were the lowest at the background site. These results could be attributed to changes in sources and atmospheric processes. Further, coal combustion and biomass burning were found to be important contributors of amines in northern cities in winter. The contribution of biomass and coal combustion to amines was weakened in other urban sites. In contrast, the amine abundance at the background site was largely controlled by biogenic sources. Acid‐base chemistry and displacement mechanism were tightly associated with the formation of amine salts at all sites. In particular, the atmospheric degradation of amines by hydroxyl radical (•OH) was significant at the Nanjing, Guangzhou, Xi'an, and Haerbin sites. The insignificant photochemical degradation of amines at the Shanghai and background sites can be explained by differentiated amine sources, meteorological conditions, and •OH levels. Overall, our findings deepen the understanding of the origins and atmospheric processes of amines.

Analysis on the effects of ecological conservation redline policies in the Pearl River Delta area, China

IntroductionThe ecological conservation redline (ECR) policies conducted in China are an important innovation to protect biodiversity, safeguard ecological security, and achieve sustainable development. The Pearl River Delta (PRD) area implemented the ECR policies in 2005.MethodsThis study examines the contrast between the 15 years before and after 2005. It also reveals the ECR policies' effects by comparing land use change, landscape pattern index, and habitat quality inside (IECR) and outside (OECR) the ECR area. Results and discussionThe results suggest that: (1) The ECR area has served as an ecological barrier in maintaining the stability of natural ecosystems. Over the past 30 years, the PRD area significantly changed land use types and ecosystems, mainly concentrated in the central plains and estuaries. Specifically, in the IECR, land use change was relatively stable, with a decrease of 0.05% and 0.57% in ecological land and an increase of 0.28% and 0.68% in construction land before and after 2005. In contrast, the OECR area land use changed dramatically, with a decrease of 0.37% and 1.36% in ecological land and an increase of 7.06% and 5.02% in construction land before and after 2005. (2) A general trend of landscape fragmentation exists in the study area. The contagion (CONTAG) in the IECR area is higher than in the OECR. The Shannon's diversity index (SHDI) in the IECR is lower than in the OECR area, which indicates a high degree and rapid landscape fragmentation in the OECR area. (3) Over 85% of the IECR scale had a habitat quality of 0.8–1, while the OECR area had an almost half scale with a habitat quality of 0–0.2. On the whole, the ecological stability and landscape connectivity of in the IECR area was higher than that of the OECR area. This indicates that the prohibitions on human disturbance, industrial construction, and logging activities in the IECR area allow green vegetation to succumb under natural conditions. Habitat quality in the IECR area was also higher than that of the OECR area in the PRD area, revealing that the quality of green development in the IECR area was higher. Finally, the ECR policies’ implementation has protected the environment in the PRD area and will provide experience for ecological conservation in other areas.

Detecting human interventions by spatial dependence of extreme water levels using a high dimensional conditional probability approach over the Pearl River Delta

The Pearl River Delta (PRD) is one of the largest urbanized areas in both area and population and also suffers increasing flooding hazards in the context of climate change and anthropogenic interventions. The co-occurrence of multiple upstream flooding drivers (compound flooding) over different upstream channels often exacerbates stronger impacts on downstream water levels compared with their isolated occurrence. It is particularly important to derive more reliable risk estimations of extreme water levels in downstream channels of a nested river system by considering the spatial dependence between multiple upstream floods and downstream water levels. In this study, we present an approach, termed the high-dimensional conditional probability (HDCP) approach, to capture the probabilistic dependence behavior of upstream floods and downstream water level events at the PRD, and estimate the extreme water levels' likelihood and event-impacted areas under the multiple upstream flooding. The PRD, as one of the most vulnerable regions to extreme floods in China, was used as a case study to test the applicability of the HDCP approach. First, the HDCP is used to model the conditional dependence of upstream floods and downstream water levels based on the canonical vine copula. Then, different flood scenarios are investigated by estimating the occurrence likelihood of downstream water level events and their spatial patterns. The final part identifies the changes in the occurrence likelihood variability of extreme water level events after strong human interventions. Results indicate that the upstream flooding over the Xijiang River dominates the occurrence likelihood of extreme water level events over the PRD, and the Beijiang River plays a secondary role. After strong human interventions, the effect of the Beijiang River has been strengthened, while the effect of the Xijaing River has been weakened. The proposed HDCP approach is not only applicable to the PRD area dominated by multiple upstream rivers, as mentioned in this study, but it is also promising in detecting the spatial occurrence likelihood of other hydrometeorological variables in other areas with different climates and topographical conditions, and formulating regional development strategies for policymakers in water resources and disaster drought risk managements against single/compound extreme events.

Mesoscale Structure in Urban–Rural Mobility Networks in the Pearl River Delta Area: A Weighted Stochastic Block Modeling Analysis

Understanding the spatial structure of a megaregion with urban and rural areas is crucial for promoting sustainable urbanization and urban–rural integration. Compared to the city network (or the network of urban areas), however, fewer studies focus on the network connecting rural areas or on the comparison of regional structures between urban and rural networks. Using weighted daily mobility flows from the massive mobile-phone signaling data, this study constructs an urban–urban mobility (UUM) network and an urban–rural mobility (URM) network in the Pearl River Delta (PRD) region. A weighted stochastic block model (WSBM) was adopted to identify and compare the latent mesoscale structures in the two networks. Results investigated a gradient community mesoscale structure nested with typical core–periphery (CP) structures in the UUM network and an asymmetric bipartite mesoscale structure mixed with CP hierarchies in the URM network. In a comparison of the different spatial configuration of urban/rural nodes and groupings of their roles, positions, and linkages, the study yielded empirical insights for renewed urban–rural interaction and potential planning pathways towards urban–rural integration.

Study of Construction Technology of Large Diameter and Ultradeep Cement Mixing Pile in Road Engineering

As the soft soil in the Pearl River Delta area is deep, 50 cm-diameter cement mixing pile composite foundation is often used for road engineering. A municipal road in the Hongwan District of Zhuhai adopted a mixing pile with a diameter of 80 cm and a length of 27 m, which brought great difficulty to the construction of the project. To ensure the engineering quality, the bit optimization scheme was adopted to improve the blades from the conventional two layer and four groups of blades to three layer and six groups of blades. The projection direction of each layer of blades was vertical, which could increase the mixing times and improve the mixing uniformity. At the same time, double-channel teeth were added to effectively increase the smoothness of slurry flow. The optimized nozzle is improved from a nozzle located at the bottom of the drill bit to the left and right sides of the bottom of the drill pipe to effectively relieve the blockage of the nozzle, silt backflow, and other problems. The grouting pressure is generally 0.4–0.6 MPa. After the optimization of the grout pressure, the upper limit of 0.6 MPa was used in the first stirring and spraying process, and 0.4 MPa was used in the second stirring and spraying process. The advantage is that in the first mixing, excess cement grout is ejected for mixing, and in the second mixing, the total grout dosage can be controlled by reducing the grouting pressure, which effectively improves the quality of pile body and controls the cost. To ensure uniform soil mixing, measures were taken to improve the drilling speed of the drill pipe, accelerate the speed when sinking, slow down the speed when lifting. Through the above measures, the strength of the mixing pile body was improved, and the integrity of the pile body was guaranteed. Pile integrity, effective pile diameter, pile length, and pile strength uniform accord with the design. The difficult problem of large diameter and deep cement mixing pile is solved, which provides a good reference value for similar engineering.

Regeneration Design Study Based on Long-lasting Building Strategy of Typical Chinese Work-live Unit in Guangzhou, China

After rapid urbanization from last several decades, Pearl River Delta area (PRD) in China gradually steps into an urban regeneration process, especially in the field of housing sector. However, neighbour and housing reform activities in last few years focused on the inner prat of the cities where are mainly historical districts or chaotic urban villages. While another large proportion of housing in “Dan Wei” has been ignored. It is a typical Chinese working unit combined with living and other activities, but currently faces new challenges of social and functional transformation. Although a new regeneration design strategy: “Micro-upgrading”, was firstly proposed in Guangzhou and specific for this neighborhood typology, it still cannot ideally resolve its core negative issues in last few years. Therefore, based on an architectural school’s design course, this study will select a region concentrated of “Dan Wei” units in Guangzhou, which is the core city of PRD. By making use of “Open Building” theory and “Level” strategy, some valuable research outcomes and design solutions will be discussed and proposed.

Epidemiological characteristics of pulmonary tuberculosis in Guangdong province from 2016 to 2020

Objective: To analyze the epidemiological characteristics of pulmonary tuberculosis (TB) in Guangdong province from 2016 to 2020 and provide evidence for the prevention and control of pulmonary TB. Methods: Descriptive epidemiological methods were used to analyze the incidence data of pulmonary TB reported in Guangdong from 2016 to 2020. Dynamic geometric series averaging and circular distribution methods were used to reveal the epidemic pattern. Results: A total of 356 748 pulmonary TB cases were reported in Guangdong from 2016 to 2020. The reported incidence of pulmonary TB decreased from 71.82/100 000 to 50.40/100 000 (trend χ2=6 905.57,P<0.001) , with an annual decline rate of 8.47%. Results from the circular distribution methods showed that the incidence peak would occur on May 4th-5th (Z=1 176.96,P<0.05), and the incidence was relatively higher in May compared with other months. The area distribution of the pulmonary TB epidemic was uneven, and the reported average annual incidence was in the order of the eastern area (72.15/100 000), the northern area (68.14/100 000), the western area (65.31/100 000) and the Pearl River Delta area (60.05/100 000). Results of dynamic geometric series averaging analysis showed a declining trend in the reported incidence of pulmonary TB in all areas, except Dongguan, with the average growth rate less than 0.00. The decline rate in the eastern area (-10.90%) and northern area (-10.63%) was higher than the provincial average (-8.47%). The male to female ratio of the cases was 2.63∶1 (258 562∶98 186). The reported average annual pulmonary TB incidence in men (88.37/100 000) was higher than that in women (36.86/100 000), the difference was significant (χ2=75.19, P<0.001). The reported incidence of pulmonary TB generally increased with age (trendχ2=123 849.44, P<0.001), and reached peak in age group ≥65 years (164.54/100 000). Dynamic geometric series averaging analysis showed an increasing trend of the reported pulmonary TB incidence in age groups 5-14 years and 15-24 years, with the average growth rate of 0.05% and 3.60%. Conclusions: The reported annual incidence of pulmonary TB showed a declining trend year by year in Guangdong from 2016 to 2020. However, an increasing incidence was reported in children and adolescents. Active case finding should be strengthened in the elderly and other key populations. With comprehensive TB prevention and control measures, it is still necessary to pay attention to the prevention and control of pulmonary TB in men, low-income groups and less developed areas in Guangdong and strengthen the comprehensive prevention and control in winter and spring.

Human infection of avian influenza A H3N8 virus and the viral origins: a descriptive study

The H3N8 avian influenza virus (AIV) has been circulating in wild birds, with occasional interspecies transmission to mammals. The first human infection of H3N8 subtype occurred in Henan Province, China, in April, 2022. We aimed to investigate clinical, epidemiological, and virological data related to a second case identified soon afterwards in Hunan Province, China. We analysed clinical, epidemiological, and virological data for a 5-year-old boy diagnosed with H3N8 AIV infection in May, 2022, during influenza-like illness surveillance in Changsha City, Hunan Province, China. H3N8 virus strains from chicken flocks from January, 2021, to April, 2022, were retrospectively investigated in China. The genomes of the viruses were sequenced for phylogenetic analysis of all the eight gene segments. We evaluated the receptor-binding properties of the H3N8 viruses by using a solid-phase binding assay. We used sequence alignment and homology-modelling methods to study the effect of specific mutations on the human receptor-binding properties. We also conducted serological surveillance to detect the H3N8 infections among poultry workers in the two provinces with H3N8 cases. The clinical symptoms of the patient were mild, including fever, sore throat, chills, and a runny nose. The patient's fever subsided on the same day of hospitalisation, and these symptoms disappeared 7 days later, presenting mild influenza symptoms, with no pneumonia. An H3N8 virus was isolated from the patient's throat swab specimen. The novel H3N8 virus causing human infection was first detected in a chicken farm in Guangdong Province in December, 2021, and subsequently emerged in several provinces. Sequence analyses revealed the novel H3N8 AIVs originated from multiple reassortment events. The haemagglutinin gene could have originated from H3Ny AIVs of duck origin. The neuraminidase gene belongs to North American lineage, and might have originated in Alaska (USA) and been transferred by migratory birds along the east Asian flyway. The six internal genes had originated from G57 genotype H9N2 AIVs that were endemic in chicken flocks. Reassortment events might have occurred in domestic ducks or chickens in the Pearl River Delta area in southern China. The novel H3N8 viruses possess the ability to bind to both avian-type and human-type sialic acid receptors, which pose a threat to human health. No poultry worker in our study was positive for antibodies against the H3N8 virus. The novel H3N8 virus that caused human infection had originated from chickens, a typical spillover. The virus is a triple reassortment strain with the Eurasian avian H3 gene, North American avian N8 gene, and dynamic internal genes of the H9N2 viruses. The virus already possesses binding ability to human-type receptors, though the risk of the H3N8 virus infection in humans was low, and the cases are rare and sporadic at present. Considering the pandemic potential, comprehensive surveillance of the H3N8 virus in poultry flocks and the environment is imperative, and poultry-to-human transmission should be closely monitored. National Natural Science Foundation of China, National Key Research and Development Program of China, Strategic Priority Research Program of the Chinese Academy of Sciences, Hunan Provincial Innovative Construction Special Fund: Emergency response to COVID-19 outbreak, Scientific Research Fund of Hunan Provincial Health Department, and the Hunan Provincial Health Commission Foundation.

Spatiotemporal transitions of organophosphate esters (OPEs) and brominated flame retardants (BFRs) in sediments from the Pearl River Delta, China

Recent regulations on the use of brominated flame retardants (BFRs, especially polybrominated diphenyl ethers, PBDEs) have led a sharp increase in the use of organophosphate esters (OPEs), which have become the subject of widespread environmental concern. To gain insights into their environmental transitions, we investigated the spatiotemporal trends and sources of 25 OPEs and 23 BFRs (21 PBDEs and two alternative BFRs) in sediments from the Pearl River Delta (PRD), the second economic/industrial region of China. Among them, PBDEs showed higher mean concentrations than OPEs and alt-BFRs in PRD sediments, a continual increase in most PRD areas, and positive correlations with most local socioeconomic parameters. The source analysis results indicated that all of these changes resulted from the substantial use/stock of PBDEs (especially deca-BDE) in this region, and BDE-209 displayed debromination in most sediments. OPEs demonstrated obvious increases in sediments from all major PRD rivers, especially those located in less-developed regions. This distribution might be related to the large-scale industry relocation from the central PRD area to its vicinities. Unexpectedly, decabromodiphenyl ethane (DBDPE), an important deca-BDE substitute, presented considerable declines in the PRD sediments while several novel OPEs showed considerably high proportions, especially aryl-substituted OPEs, which merit further screening analysis.