Spatially Heterogeneous Response of Carbon Storage to Land Use Changes in Pearl River Delta Urban Agglomeration, China

Carbon storage of terrestrial ecosystems plays a vital role in advancing carbon neutrality. Better understanding of how land use changes affect carbon storage in urban agglomeration will provide valuable guidance for policymakers in developing effective regional conservation policies. Taking the Pearl River Delta Urban Agglomeration(PRDUA) in China as an example, we examined the heterogeneous response of carbon storage to land use changes in 1990–2018 from a combined view of administrative units and physical entities. The results indicate that the primary change in land use was due to the expansion of construction land(5897.16 km2). The carbon storage in PRDUA decreased from 767.34 Tg C in 1990 to 725.42 Tg C in 2018 with a spatial pattern of high wings and the low middle. The carbon storage loss was largely attributed to construction land expansion(55.74%), followed by forest degradation(54.81%). Changes in carbon storage showed significant divergences in different sized cities and hierarchical boundaries. The coefficients of geographically weighted regression(GWR) reveal that the alteration in carbon storage in Guangzhou City was more responsive to changes in construction land(-0.11) compared to other cities, while that in Shenzhen was mainly affected by the dynamics of forest land(8.32). The change in carbon storage was primarily influenced by the conversion of farmland within urban extent(5.05) and the degradation of forest land in rural areas(5.82). Carbon storage changes were less sensitive to the expansion of construction land in the urban center, urban built-up area, and ex-urban built-up area, with the corresponding GWR coefficients of 0.19, 0.04, and 0.02. This study necessitates the differentiated protection strategies of carbon storage in urban agglomerations.

Leave or Stay?Antecedents of High-level Talent Migration in the Pearl River Delta Megalopolis of China:from a Perspective of Regional Differentials in Housing Prices

Rapid urbanization and population growth have triggered an increase in urban housing demand and rising housing prices,which can influence the migration intention of high-level talents.Much work within the literature has focused more on the migration of the general public.However,antecedents of migration intention and the impact of housing prices on the migration of high-level talents remain unclear.Therefore,based on the push-pull theory,this study investigates the influencing factors of talent migration intention and explores the role of housing prices.This study reveals a complex mechanism underlying migration decisions by using logistic regression models and survey data of high-level talents in the Pearl River Delta(PRD)megalopolis of China.The results indicate that:1)in high house-price regions,social integration is the primary push factor,and the main factors for retaining talents are the expectation of future work and intimate family relationships;2)in medium house-price regions,the main factors that attract talents are the current salary level and close family ties;3)in low house-price regions,living convenience is a determining factor in retaining talents.This study provides a new perspective for talent mobility research and offers valuable inputs for retaining and attracting talents in different economic development regions.Findings are of great significance for formulating talent introduction policies and forming a new pattern of rational spatial docking and effective allocation of human resources.

Characterizing ionic species in PM_(2.5) and PM_(10) in four Pearl River Delta cities,South China

PM2.5 and PM10 samples were collected at four major cities in the Pearl River Delta （PRD）, South China, during winter and summer in 2002. Six water-soluble ions, Na^＋, NH4＋, K^＋, Cl^-, NO3^- and SO4^2- were measured using ion chromatography. On average, ionic species accounted for 53.3% and 40.5% for PM2.5 and PM10, respectively in winter and 39.4% and 35.2%, respectively in summer. Secondary ions such as sulfate, nitrate and ammonium accounted for the major part of the total ionic species. Sulfate was the most abundant species followed by nitrate. Overall, a regional pollution tendency was shown that there were higher concentrations of sulfate, nitrate and ammonium in Guangzhou City than those in the other PRD cities. Significant seasonal variations were also observed with higher levels of species in winter but lower in summer. The Asian monsoon system was favorable for removal and diffusion of air pollutants in PRD in summer while highly loading of local industrial emissions tended to deteriorate the air quality as well. NO3^-/SO4^2- ratio indicated that mobile sources have considerably contribution to the urban aerosol, and stationary sources should not be neglected. Besides the primary emissions, complex atmospheric reactions under favorable weather conditions should be paid more attention for the control of primary emission in the PRD region.

Heavy metal concentrations in edible bivalves and gastropods available in major markets of the Pearl River Delta

Molluscs are able to accumulate heavy metals and impose health hazard to consumers. The main objective of the present study is to investigate the heavy metal concentrations in edible bivalves and gastropods available in major markets of the Pearl River Delta. Fourteen species of edible molluscs were purchased from six markets in Hong Kong and Guangdong Province. The fresh of these biota were tested for their cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) concentrations (based on wet weight). The results indicated that amongst the 14 edible molluscs, only Cd, Pb, Ni, Cr, Sb and Sn concentrations in three species (Ruditapes philippinarum, Perna viridis and Hemifusus tuba) were within the local regulatory limits. Over 60% of bivalve species exceeded maximum permitted levels of Cd (2 mug/g) and Cr (1 mug/g), while over 40% of gastropod species exceeded the maximum levels of Sb (1 mug/g) and Cr (1 mug/g). Most of the samples collected from Hong Kong had significantly higher contents of Pb and Sb, but similar levels of Cd, Cu and Zn when compared with samples collected across the border ( p < 0.05; p 0.01; p < 0.001 respectively). In general, the molluscs purchased in Guangdong markets had higher metal contents than those purchased from the Hong Kong markets. When compared with the Provisional Tolerable Weekly Intake or Maximum Acceptable Daily Load recommended by FAO/WHO Expert Committee on Food Additives, Cd levels of five species (Anadara ferruginea, Pinna pectinata, Chlamys nobilis, Babylonia lutosa and Hemifusus terntanus) and Cr levels of seven species ( Anadara ferruginea, Paphia undulata, Pinna pectinata, Babylonia lutosa, Hemifusus terntanus, Cymbium melo and Cipangopaludina chinensis) were higher than both the human daily acceptable limits (for Cd and Cr respectively) and the local regulatory levels (for Cd and Cr respectively).

Impacts of Weather Conditions Modified by Urban Expansion on Surface Ozone: Comparison between the Pearl River Delta and Yangtze River Delta Regions

In this paper, the online weather research and forecasting and chemistry （WRF-Chem） model is used to explore the impacts of urban expansion on regional weather conditions and its implication on surface ozone concentrations over the Pearl River Delta（PRD） and Yangtze River Delta（YRD） regions. Two scenarios of urban maps are used in the WRF-Chem to represent the early 1990s （pre-urbanization） and the current urban distribution in the PRD and the YRD. Month-long simulation results using the above land-use scenarios for March 2001 show that urbanization increases both the day- and night-time 2-m temperatures by about 0.6℃and 1.4℃, respectively. Daytime reduction in the wind speed by about 3.0 m s-1 is larger than that for the nighttime （0.5 to 2 m s-1）. The daytime increase in the PBL height （〉 200 m） is also larger than the nighttime （50-100 m）. The meteorological conditions modified by urbanization lead to detectable ozone-concentration changes in the PRD and the YRD. Urbanization increases the nighttime surface-ozone concentrations by about 4.7%-8.5% and by about 2.9%-4.2% for the daytime. In addition to modifying individual meteorological variables, urbanization also enhances the convergence zones, especially in the PRD. More importantly, urbanization has different effects on the surface ozone for the PRD and the YRD, presumably due to their urbanization characteristics and geographical locations. Even though the PRD has a smaller increase in the surface temperature than the YRD, it has （a） weaker surface wind speed, （b） smaller increase in PBL heights, and （c） stronger convergence zones. The latter three factors outweighed the temperature increase and resulted in a larger ozone enhancement in the PRD than the YRD.

Changes in forest biomass carbon stock in the Pearl River Delta between 1989 and 2003

Forest ecosystems play a significant role in maintaining climate stability at the regional and global scales as an important carbon sink.Regional forest carbon storage and its dynamic changes in the Pearl River Delta have been estimated using the continuous biomass expansion factor(BEF)method based on field measurements of forests plots in different age classes and forest inventory data of three periods(1989–1993,1994–1998,1999–2003).The results show that regional carbon storage increased by 16.76%,from 48....

Impact of the Built Environment on the Spatial Heterogeneity of Regional Innovation Productivity:Evidence from the Pearl River Delta,China

With the global economy increasingly dependent on innovation,urban discourse has shifted to consider what kinds of spatial designs may best nurture innovation.We examined the relationship between the built environment and the spatial heterogeneity of regional innovation productivity(RIP)using the example of China's Pearl River Delta(PRD).Based on a spatial database of 522546 patent data from 2017,this study proposed an innovation-based built environment framework with the following five aspects:healthy en-vironment,daily interaction,mixed land use,commuting convenience,and technology atmosphere.Combining negative binomial regression and Geodetector to examine the impact of the built environment on RIP,the results show that the spatial distribution of innovation productivity in the PRD region is extremely uneven.The negative binomial regression results show that the built environment has a significant impact on the spatial differentiation of RIP,and,specifically,that healthy environment,mixed land use,commuting convenience,and technology atmosphere all demonstrate significant positive impacts.Meanwhile,the Geodetector results show that the built environment factor impacts the spatial heterogeneity of RIP to varying degrees,with technology atmosphere demonstrating the greatest impact intensity.We conclude that as regional development discourse shifts focus to the knowledge and innovation economy,the innovation-oriented design and updating of built environments will become extremely important to policymakers.

Legislation on protection of drinking water sources and local management practices in the Pearl River Delta region of China

The protection of drinking water sources is vital to urban development and public health.In this study,the current situation of the mandatory protection area for drinking water source in the Pearl River Delta region was investigated using a method combining Google Earth with the field survey.The gaps between management practices and legislation requirements were analyzed.Finally,several countermeasures for water resource protection were proposed as follows:to promote delineation in a more scientific way,to safeguard the sanctity of the law,to make better plan on water saving,and to encourage public participation in supervision and management.

The Age of the Old Transgression Sequence in the Pearl River Delta, China

The Pearl River Delta （PRD） is located in the north coast area of the South China Sea （SCS）. As one of the largest delta in China, only the two latest events among the several tens of eustatic fluctuations occurring in the Quaternary were recorded in almost whole area of the PRD.

A Closure Study of Aerosol Hygroscopic Growth Factor during the 2006 Pearl River Delta Campaign

Measurements of aerosol physical, chemical and optical parameters were carried out in Guangzhou, China from 1 July to 31 July 2006 during the Pearl River Delta Campaign. The dry aerosol scattering coefficient was measured using an integrating nephelometer and the aerosol scattering coefficient for wet conditions was determined by subtracting the sum of the aerosol absorption coefficient, gas scattering coefficient and gas absorption coefficient from the atmospheric extinction coefficient. Following this, the aerosol hygroscopic growth factor, f（RH）, was calculated as the ratio of wet and dry aerosol scattering coefficients. Measurements of size-resolved chemical composition, relative humidity （RH）, and published functional relationships between particle chemical composition and water uptake were likewise used to find the aerosol scattering coe？cients in wet and dry conditions using Mie theory for internally- or externally-mixed particle species [（NH_4）_2SO_4, NH_4NO_3, NaCl, POM, EC and residue]. Closure was obtained by comparing the measured f（RH） values from the nephelometer and other in situ optical instruments with those computed from chemical composition and thermodynamics. Results show that the model can represent the observed f（RH） and is appropriate for use as a component in other higher-order models.

Frequency, Duration and Intensity of Dengue Fever Epidemic Risk in Townships in Pearl River Delta and Yunnan in China, 2013

Dengue fever （DF）, one of the neglected tropical diseases also known as breakbone fever, is a mosquito-borne disease common in the tropics and subtropics. Dengue fever is transmitted primarily by A.aegypti, resulting in infection with any of four distinct but closely related virus serotypes. The majority of infected people experience a self-limiting clinical course. A small proportion of cases develop into life-threatening Dengue Hemorrhagic Fever or Dengue Shock Syndrome.

Employed Farmers in the Pearl River Delta and Related Issues

As a special weak group in agricultural floating population,employed farmers make special historic contribution to socio-economic development of the Pearl River Delta.However,employed farmers are faced with survival difficulties,which lead to a series of social issues.From historical origin,current situations and social issues,we put forward countermeasures to solve problems of employed farmers:solve the household registration of employed farmers;raise the compensation standard of land expropriation and demolition;cancel the admission threshold;provide reemployment guidance;and establish management funds of employed farmers.

HAS THE PEARL RIVER DELTA BEEN AN EXPORT-ORIENTED ECONOMY?

Ever since the introduction of the Open Door Policy, the Pearl River Delta (PRD) has enjoyed very phenomenal export and economic growth. As a result, many scholars have tried to associate the two phenomena and described the region as an,'export-oriented economy'.However, these studies, mostly based on the rapid export growth of the PRD and its status as the most important exporting area of the country,have not paid any heed to the actual export-orientation of the regional economy and, hence, cannot prove that the PRD has been a 'truly'export-oriented economy. in view of these shortcomings. the present paper attempts to re-examine the issue from the viewpoint of the PRD's local economy, at both the regional and county levels. The study period is from 1981 to 1990. Judging from the export-dependency indices and the relative importance of exports in accounting for the economic growth and industrialization of the PRD, this paper concludes that the region, though having signs of increasing export-orientation, cannot be categorized as a 'truly' export-oriented economy. In addition, it also shows that most of the 'evidences' or 'common beliefs' behind the notion of an export-oriented economy in the RD are illusionary, if not erroneous. Finally, the paper explores into the reasons behind the low export-orientation of the PRD and tries to sugyst some ways for boosting the export-orientation of the PRD and tries to suggest some ways for boosting the export-orientation of the region.

The Middle-aged and Knowledge Workers: Demographic and Economic Changes in the Pearl River Delta, China

Demographic and economic development can be seen as two sides of one coin in the process of regional development.This article deals with how economic and demographic changes influence the settlement structure and development of the Pearl River Delta(PRD)and lead to regionalization processes within the large agglomerations.The aim of the study was to understand the interrelation between the three aspects:economic change,demographic change and change of spatial structures.Based on population age and occupational data,spatial changes in demographic structure and economic activities from 2000 to 2010 were analyzed.It was found that the demographic and economic change reflected changing spatial patterns between the urban centers and the hinterland in the PRD.Two processes were apparent during the studied period in the hinterlands and the high-density areas of the PRD.On one hand,the hinterlands in the PRD attracted more manufacturing activities,while the inner high-density areas experienced a decrease in manufacturing,associated with an increase in young labor in regions where workplaces that only required limited education expanded.On the other hand,specialization in knowledge-intensive business services increased in the inner high-density areas,which also saw an increased share in the older population.This finding suggests that increasing knowledge-intensive work correlates with higher age structures due to the longer formal education required and also the benefits knowledge workers accrue through experience and gained knowledge over time.Therefore,based on a transformation process,we tentatively conclude that the populations in high-density areas in the PRD became more middle-aged and were represented by more knowledge workers.

Analysis on Ecological Footprint of the Urban Agglomeration in Pearl River Delta

[Objective] The research aimed to calculate and analyze ecological footprint of the urban agglomeration in Pearl River Delta in 2009. [Method] 9 cities in Pearl River Delta as research zone, by using calculation model of the ecological footprint, ecological footprint and security of the urban agglomeration in Pearl River Delta were calculated. Current situation and sustainable development condition of the ecological environment in Pearl River Delta were conducted quantitative analysis. [Result] Except construction land and woodland, other 4 kinds of lands were all in ecological deficit states in Pearl River Delta. Especially arable land and fossil fuel land had obvious ecological deficit. [Conclusion] Biological resource consumption level and energy consumption level in Pearl River Delta were higher. We ought to take a variety of measures to reduce ecological deficit, making development manner turn toward sustainable direction.

Study on Low Carbon Trade Development in China Pearl River Delta Region Initiated by Low Carbon Tariffs

In order to clarify the linkage between carbon tariffs and trade development, the Pearl River Delta region of China, the area with intensive processing trade, was selected to analyze the effects of carbon tariff collections on the production cost, export commodity structure, trade modes and trade terms of the export industries in the Pearl River Delta region, and measures of developing low carbon trade were proposed.

Gene abundances of AOA,AOB,and anammox controlled by groundwater chemistry of the Pearl River Delta,China

Ammonia-oxidizing archaea(AOA),ammonia-oxidizing bacteria(AOB),and anaerobic ammonia-oxidation(anammox)bacteria are very important contributors to nitrogen cycling in natural environments.Functional gene abundances of these microbes were believed to be well relevant to N-cycling in groundwater systems,especially in the Pearl River Delta(PRD)groundwater with unique high intrinsic ammonia concentrations.In this research,20 sediment samples from two in the PRD were collected for porewater chemistry analysis and quantification of N-cycling related genes,including archaeal and bacterial amoA gene and anammox 16S ribosomal Ribonucleic Acid(rRNA)gene.Quantitative Polymerase Chain Reaction(qPCR)results showed that gene abundances of AOA,AOB,and anammox bacteria ranged from 3.13×10^(5)to 3.21×10^(7),1.83×10^(4)to 2.74×10^(6),and 9.27×10^(4)to 8.96×10^(6)copies/g in the sediment of the groundwater system,respectively.Anammox bacteria and AOA dominated in aquitards and aquifers,respectively,meanwhile,the aquitard-aquifer interfaces were demonstrated as ammonium-oxidizing hotspots in the aspect of gene numbers.Gene abundances of nitrifiers were analyzed with geochemistry profiles.Correlations between gene numbers and environmental variables indicated that the gene abundances were impacted by hydrogeological conditions,and microbial-derived ammonium loss was dominated by AOA in the northwest PRD and by anammox bacteria in the southeast PRD.

Evolution of Living Space in Traditional Villages in the Pearl River Delta under the Influence of Urbanization:A Case Study of Xiaozhou Village in Guangzhou City

Traditional villages in the Pearl River Delta are known as "Lingnan water village".Urbanization affects the style of traditional villages in three ways.It also presents a positive side under the background of new urbanization.The living space of Xiaozhou Village has the unique characteristics of Lingnan water village.At the same time,it is obviously affected by urbanization.Industrialization and commercialization continue to promote the villagers to dismantle the old and build new ones until it becomes a village in the city.The evolution of the traditional living space is reflected in three aspects:being nibbled away or even disappeared,destroying the traditional style,function disappearance or transformation.In the later stage of urbanization,some living spaces have been repaired and updated.

Annual Fluxes of Heavy Metal Elements in Atmospheric Dry and Wet Depositions in the Pearl River Delta Economic Region, Guangdong Province

There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The eight heavy metal elements of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd in 474 dry and wet deposition samples were tested in terms of the standard procedures. Their average annual fluxes have no obvious difference between dry deposition and wet deposition. So these elements might be at an equilibrium or quasi-equilibrium state between dry deposition and wet deposition.