Context, aim and method

Abstract. The Pearl River Delta (PRD) region in South China is faced with severe ambient tropospheric ozone (O3) pollution in autumn and summer, which mostly coincides with the occurrence of typhoons above the Northwest Pacific. With increasingly severe O3 pollution in the PRD under the influence of typhoons, it is necessary to gain a comprehensive understanding of the impact of typhoons on O3 transport, production and accumulation for efficient O3 reduction. In this study, we analysed the general influence of typhoons on O3 pollution in the PRD via systematic comparisons of meteorological conditions, O3 processes and sources on O3 pollution days with and without typhoon occurrence (denoted as the typhoon-induced and no-typhoon scenarios, respectively) and also examined the differences in these influences in autumn and summer. The results show that the approach of typhoons was accompanied by higher wind speeds and strengthened downdraughts in autumn, as well as the inflows of more polluted air masses in summer, suggesting favourable O3 transport conditions in the typhoon-induced scenario in both seasons. However, the effect of typhoons on the production and accumulation of O3 were distinct. Typhoons led to reduced cloud cover, and thus stronger solar radiation in autumn, which accelerated O3 production, but the shorter residence time of local air masses was unfavourable for the accumulation of O3 within the PRD. In contrast, in summer, typhoons increased cloud cover, and weakened solar radiation, thus restraining O3 formation, but the growing residence time of local air masses favoured O3 accumulation. The modelling results using the Community Multiscale Air Quality (CMAQ) model for the typical O3 pollution days suggest increasing contributions from the transport processes and sources outside the PRD for O3 pollution, confirming enhanced O3 transport under typhoon influence in both seasons. The results of the process analysis in CMAQ suggest that the chemical process contributed more in autumn but less in summer in the PRD. Since O3 production and accumulation cannot be enhanced at the same time, the proportion of O3 contributed by emissions within the PRD was likely to decrease in both seasons. The difference in the typhoon influence on O3 processes in autumn and summer can be attributed to the seasonal variation of the East Asian monsoon. From the meteorology–process–source perspective, this study revealed the complex influence of typhoons on O3 pollution in the PRD and their seasonal differences. To alleviate O3 pollution under typhoon influence, emission control is needed on a larger scale, rather than only within the PRD.

General features and synoptic-scale environments of mesoscale convective systems over South China during the 2013–2017 pre-summer rainy seasons

Many organic pollutants attract public health concern due to their genotoxicity. To investigate the genotoxicity of organic matter in surface water of the Pearl River Delta (PRD). Organic substances of 24 samples (dry and wet season) from North River, West River and East River were extracted from 60 L source water by XAD-2 macroporous resin. DNA damage effect of organic extracts was tested in human derived liver cells (HL-7702), using single cell gel electrophoresis (SCGE) assay. The results showed that 100% organic extracts (24/24) could induce DNA damage in HL-7702 cells when the concentration was above 1.0 L surface water/ml culture, no significant difference of DNA damage between dry and wet seasons was observed. The organic substance-induced DNA damage in HL-7702 cells was significantly (P < 0.05) correlated with the contents of Dissolved Organic Carbon in both seasons and Total Suspended Solids in dry season. In conclusion, organic extracts induced genetic damage in HL-7702 cells, indicating potential genotoxicity of organic pollutants of surface water from PRD, South China.

Occurrence and risk assessment of tetracycline antibiotics in soils and vegetables from vegetable fields in Pearl River Delta, South China

The overcapacity in China’s ports has spurred port integration across many provinces but not in the Pearl River Delta (PRD) due to its unique institutional environment. Effective port integration often involves coordinating differentiated functions. We therefore wonder whether port functional differentiation occurs in the PRD. Traditionally, port throughput has been a primary indicator for functional differentiation, constraining the exploration of diverse shipping-related characteristics. This study aims to propose an analytical approach to identify various port functions with seven indicators, considering the multifaceted shipping characteristics of ship traffic and shipping services within a regional port system. The research approach is applied to the PRD container port system in South China, utilizing Automatic Identification System (AIS) data from 2015 to 2022. Furthermore, the study investigates how geographical conditions, industrial development, institutional factors, and port governance structures contribute to the observed functional differentiation. The results reveal evolving functional specialization among the core ports within the PRD. Hong Kong primarily focuses on imports and transshipment, Shenzhen establishes its strength in exports and serves as a gateway, while Guangzhou handles the majority of domestic traffic. We found that the port functional differentiation in the PRD has been largely spontaneous, with minimal proactive policy interventions.

Recent worldwide heatwaves have shattered temperature records in many regions. In this study, we applied a dynamical downscaling method on the high-resolution version of the Max Planck Institute Earth System Model (MPI-ESM-1-2-HR) to obtain projections of the summer thermal environments and heatwaves in the Pearl River Delta (PRD) considering three shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5) in the middle and late twenty-first century. Results indicated that relative to the temperatures in the 2010s, the mean increases in the summer (June–September) daytime and nighttime temperatures in the 2040s will be 0.7°–0.8°C and 0.9°–1.1°C, respectively. In the 2090s, the mean difference will be 0.5°–3.1°C and 0.7°–3.4°C, respectively. SSP1-2.6 is the only scenario in which the temperatures in the 2090s are expected to be lower than those in the 2040s. When compared with those in the 2010s, hot extremes are expected to be more frequent, intense, extensive, and longer-lasting in the future in the SSP2-4.5 and SSP5-8.5 scenarios. In the 2010s, a heatwave occurred in the PRD lasted for 6 days on average, with a mean daily maximum temperature of 34.4°C. In the 2040s, the heatwave duration and intensity are expected to increase by 2–3 days and 0.2°–0.4°C in all three scenarios. In the 2090s, these values will become 23 days and 36.0°C in SSP5-8.5. Moreover, a 10-yr extreme high temperature in the 2010s is expected to occur at a monthly frequency from June to September in the 2090s. Significance Statement Pearl River Delta (PRD) has been experiencing record-shattering heatwaves in recent years. This study aims to investigate the future trends of summer heatwaves in the PRD by modeling three future scenarios including a sustainable scenario, an intermediate scenario, and a worst-case scenario. Except for the sustainable scenario, summer temperatures in the intermediate and worst-case scenarios will keep increasing, and heatwaves will become more frequent, intense, extensive, and longer-lasting. In the worst-case scenario, extreme heat events that occurred once in 10 years in the 2010s will shorten to once a month in the 2090s. A better understanding of heatwave trends will benefit implementing climate mitigation methods, urban planning, and improving social infrastructure.

While the “state-led urbanisation” argument highlights the dominance of state power in China’s urban process, the notion of “local state/village corporatism” pays attention to the significant stake of local governments and their rural collectivities in economic development and urban growth, especially in the region of Guangdong’s Pearl River Delta. Yet, these two arguments overlook the multiple forms of collectivities, including the communal land system, local clanship, and territories of folk religion, and their participation in the urban process. This article adopts a more structural approach by seeing the “urban process” as the socio-spatial reorganisation of and struggle over “the collective” in the capitalist socio-spatial relations of production. With the ethnographic study of Village Z in Dongguan, I argue that proletarianisation is not simply an integral part of the urban process but also the background against which communal imagination and the cellular form of activism take their shapes. Local collectivities do not necessarily share the interests and values of the developmental states but counteract the local states at all levels, thereby perpetuating contestation over urban spaces.

Butyltins in sediments and biota collected from the Pearl River Delta, South China were analyzed by a gas chromatograph–atomic emission detector (GC-AED). The concentrations of tributyltin (TBT) in the sediments ranged from 1.7 to 379.7 ng/g dry weight. Their spatial distribution suggested that shipping activities, especially shipyards were mostly responsible for the TBT contamination in the region. A good linear relationship was observed between the DBT (dibutyltin)/TBT and MBT (monobutyltin) /TBT ratios of the samples in the Pearl River, the Pearl River estuary and the West River, suggesting that TBT in these areas came from similar sources but had undergone a different extent of degradation. The butyltins in the Macao waters seemed to have undergone a different degradation process. All TBT concentrations of the fish, mussel and shrimp samples collected in this study were below the seafood tolerable average residue level (TARL).

Prospective study on physical planning and the environment in the megalopolis in formation in North-West Europe

Mixing ratios and sources of halocarbons in urban, semi-urban and rural sites of the Pearl River Delta, South China

Polycyclic aromatic hydrocarbons in upstream riverine runoff of the Pearl River Delta, China: An assessment of regional input sources

This study investigated the extent of heavy metal accumulation in leaf vegetables and associated potential health risks in agricultural areas of the Pearl River Delta (PRD), South China. Total concentrations of mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and arsenic (As) were determined in 92 pairs of soil and leaf vegetable (flowering Chinese cabbage, lettuce, pakchoi, Chinese cabbage, loose-leaf lettuce, and Chinese leaf mustard) samples collected from seven agricultural areas (cities). The bioconcentration factors (BCF) of heavy metals from soil to vegetables were estimated, and the potential health risks of heavy metal exposure to the PRD residents through consumption of local leaf vegetables were assessed. Results showed that among the six leaf vegetables, pakchoi had the lowest capacity for heavy metal enrichment, whereas among the five heavy metals, Cd had the highest capacity for transferring from soil into vegetables, with BCF values 30-fold those of Hg and 50-fold those of Cr, Pb and As. Sewage irrigation and fertilization were likely the main sources of heavy metals accumulated in leaf vegetables grown in agricultural areas of the PRD region. Different from previous findings, soil pH had no clear effect on metal accumulation in leaf vegetables. Despite a certain degree of metal enrichment from soil to leaf vegetables, the PRD residents were not exposed to significant health risks associated with consumption of local leaf vegetables. Nevertheless, more attention should be paid to children due to their sensitivity to metal pollutants.

Riverine inputs of total organic carbon and suspended particulate matter from the Pearl River Delta to the coastal ocean off South China

Geochemical evolution of geothermal waters in the Pearl River Delta region, South China: Insights from water chemistry and isotope geochemistry

1-Chloro-2,2-bis(4-chlorophenyl)ethene (p,p'-DDMU), a metabolite of either 1,1-dichloro-22-bis(4-chlorophenyl)ethane (p,p'-DDD) or 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (p,p'-DDE), which is degraded from 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT), was detected in a variety of environmental matrices of the Pearl River Delta (PRD), South China, including fish, fish feeds, semidigested fish stomach contents, marine surface sediment, surface soil, atmospheric gaseous phase, and particulates, rainwater, and coastal rainwater. Forfish species,the concentrations of p,p'-DDMU were significantly higher in farmed fish than in marine wild fish, with the highest value obtained in seawater farmed fish species (mear/median values of 262/173 ng/g lipid). The relative abundance of p,p'-DDMU to total DDTs (sum of o,p'- and p,p'-DDT, DDD, and DDE) was higher in samples of marine origin (approximately 5%) than in those of terrestrial origin (approximately 2%). Because p,p'-DDD was considerably abundant in all samples and a negative linear correlation was found between p,p'-DDD/(p,p'-DDD + p,p'-DDE) and p,p'-DDMU/DDTs in the marine sediments (r2 = 0.73) and seawater farmed fish (r2 = 0.29) under investigation, it is possible that DDMU was partially dehydrochlorinated from DDD in the environment of the PRD. A fugacity-based assessment suggested that p,p'-DDMU is likely to transport from sediment to seawater and then to air and from soilto air. The ubiquity of p,p'-DDMU in the PRD indicates that it may also be widespread worldwide particularly in countries with large amounts of DDT used currently and/or historically. Given the potential risk of p,p'-DDMU to human health, more efforts should be directed toward to this previously overlooked contaminant