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This paper reports on an investigation of the spatial and temporal variation of main environmental indicators in the Pearl River estuary using a numerical water quality model. An integrated field survey was undertaken in 2006 and 2007, and the data obtained were used to set up and verify the model. The water quality model was driven by a hydrodynamic model in which the monthly average freshwater discharges from eight major entrances were taken into account and the seaward boundary elevations were specified based on eight major tidal constituents. Two environmental indicators - dissolved inorganic nitrogen and chemical oxygen demand - were chosen as nutrient and pollution indicators, respectively, according to the actual pollution conditions. Both land-based sources (carried by the discharges) and air-based sources (wet and dry atmospheric depositions) were included in the water quality model and the processes of advection, diffusion and degradation were also modelled. The model predictions generally agreed well with the sampling data, and existing field and model results. The present contributions of the main sources were investigated and prospective scenarios of pollution reductions were predicted. [ABSTRACT FROM AUTHOR]

Basin response to precipitation variability by terrestrial hydrological processes may be manifested at different timescales and vary from one basin to another. A quantitative grasp of natural variability modulation is desirable for characterizing basin tendency or vulnerability on floods and droughts; quantification is not always straightforward, however. Using a macro-scale hydrological model, the Variable Infiltration Capacity (VIC) model, the hydrological time series (runoff, soil moisture, and evapotranspiration) were obtained for the 10 sub-basins over the Pearl River basin in South China for the period 1952–2000. A continuous wavelet transform was used to identify the characteristics of the temporal scales of basin-featured extreme events and related multiple-scale variabilities. By use of wavelet coherence analysis and rank correlation method, the cross correlations of monthly anomalies of hydrological processes were examined. The results showed that the runoff correlated most with, and the evapotranspiration had less response to, the precipitation variability. The analyzed results revealed that the attenuation effect of runoff in response to precipitation variability was mainly within the timescale of 2 yr in the Pearl River basin. The soil moisture variability can extend precipitation variation along with timescales. With understanding of the variability features of the terrestrial hydrological processes, this paper showed one geomorphic index, a basin form factor (FF), can represent the wavelet-based indices for high- and low-frequency responses to precipitation variability. It was found that, for a sub-basin with a higher FF value, precipitation variability can be represented more by runoff variability at less than 2-yr timescales; such a sub-basin is apt to have serious floods. With a lower FF value, a sub-basin has longer memory of soil moisture, leading to severe droughts during dry periods. This finding would be valuable to evaluate the tendency on occurrence of floods and droughts in the Pearl River basin, a humid region, which may be transferable to other basins in the globe. [ABSTRACT FROM AUTHOR]

Abstract: The complementary processes of globalization and regionalization have resulted in the proliferation of cross-boundary regions in the world since the 1980s. Existing studies have primarily concentrated at supranational paradigms or nation-based level of analysis in some specific regions, such as European Union (EU), North American Free Trade Association (NAFTA) and Association of Southeast Asian Nations (ASEAN), etc. This paper presents a salient sub-national cross-boundary region under “one country, two systems” in China, taking the Pearl River Delta (“the PRD” hereafter) and Hong Kong as a case. It argues that the PRD and Hong Kong have been evolving into a cross-boundary region, as a result of intensified socio-economic interaction between them over the past two decades. Previous studies have identified the role of Hong Kong as the largest source of foreign investment and entrêpot during the process of the dramatic economic development of the PRD in the 1980s and the mid-1990s. However, the changes of their relationship after Hong Kong returned to the Chinese sovereignty in 1997 are still poorly understood and analyzed. The paper attempts to update and fill the gap in the literature with the investigation of the transformation of the cross-boundary interaction between the PRD and Hong Kong in the post-1997 period. Particular attentions are paid to the paradigm shift and evolving patterns of the PRD-Hong Kong cross-boundary region under the unique framework of “one country, two systems”. [Copyright &y& Elsevier]

The Zhuhai Formation of the Huizhou Oilfield has been interpreted as being deposited in a tide-dominated estuarine setting. This paper uses stratigraphic principles, cores and logging data to analyse the facies changes of tidal sedimentation in response to the base level cycle. We conclude that the mud flat progradational allocycle is the result of a long-term base level fall, while the fining-upwards autocycle is in response to a short-term base level fall. Region-wide mud layers of supratidal zones and scour surfaces of subtidal zones are stratigraphic surfaces of tidal sedimentation. By integrating high-resolution stratigraphic correlations with seismic attributes extracted from the stratal slicing of 3-D data volumes, we use an attribute map of RMS (root mean square) amplitude to image the distribution and evolution of tidal deposits in the study area. Intertidal zones and the upper parts of the tidal cycle are favourable areas for prospecting and oil reserves and thus provide a basis for petroleum exploration and development. [ABSTRACT FROM AUTHOR]

This paper analyzes the role of the prevalent formal and informal institutions in Guangzhou in alleviating deteriorating water quality in the Pearl River. In addition to the dominating role of the local government, it examines the influences of other relevant factors such as the role of environmental non-governmental organizations, the media, and the impact of social and cultural norms. It concludes that the current institutional framework is not sufficiently competent to handle water pollution problems and that a multi-dimensional and cross-sectoral approach is necessary for water pollution control in the Pearl River in Guangzhou. [ABSTRACT FROM PUBLISHER]

This paper reports screening of multiple hormonal activities (estrogenic and androgenic activities, antiestrogenic and antiandrogenic activities) for surface water and sediment from the Pearl River system (Liuxi, Zhujiang, and Shijing rivers) in South China, using in vitro recombinant yeast bioassays. The detection frequencies for estrogenic and antiandrogenic activities were both 100% in surface water and 81 and 93% in sediment, respectively. The levels of estrogenic activity were 0.23 to 324 ng 17β-estradiol equivalent concentration (EEQ)/L in surface water and 0 to 101 ng EEQ/g in sediment. Antiandrogenic activities were in the range of 20.4 to 935 × 103 ng flutamide equivalent concentration (FEQ)/L in surface water and 0 to 154 × 103 ng FEQ/g in sediment. Moreover, estrogenic activity and antiandrogenic activity in sediment showed good correlation ( R2 = 0.7187), suggesting that the agonists of estrogen receptor and the antagonists of androgen receptor co-occurred in sediment. The detection frequencies for androgenic and antiestrogenic activities were 41 and 29% in surface water and 61 and 4% in sediment, respectively. The levels of androgenic activities were 0 to 45.4 ng dihydrotestosterone equivalent concentration (DEQ)/L in surface water, and the potency was very weak in the only detected sediment site. The levels of antiestrogenic activity were 0 to 1,296 × 103 ng tamoxifen equivalent concentration (TEQ)/L in surface water and 0 to 89.5 × 103 ng TEQ/g in sediment. The Shijing River displayed higher levels of hormonal activities than the Zhujiang and Liuxi rivers, indicating that the Shijing River had been suffering from heavy contamination with endocrine-disrupting chemicals. The equivalent concentrations of hormonal activities in some sites were greater than the lowest-observed-effect concentrations reported in the literature, suggesting potential adverse effects on aquatic organisms. Environ. Toxicol. Chem. 2011;30:2208-2215. © 2011 SETAC [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of aerosol have been simultaneously retrieved over the Pearl River Delta (PRD), China during December 2009 from multi-angular, multi-spectral, and polarized airborne data. A new airborne Directional Polarimetric Camera (DPC) with high spatial resolution (4m at 4000m a.g.l.) is used to retrieve the aerosol optical properties, which is an experimental airborne instrument focused on monitoring aerosol particle pollution, dealing with the apportionment of sources and controlling air quality in cities. We present a case study of polarized observations performed during high air pollution episodes in the southeast of China. Exceptionally high values of the aerosol optical depth of up to 0.8 (at 0.865μm) were observed in this case study. The spatial and temporal variability of aerosol optical properties over the Pearl River Delta region were analyzed using polarized measurements with high spatial resolution. To reduce the ambiguity in retrieving aerosol optical properties using DPC alone, ground-based measurements (Automatic CE318-DP polarized sun-sky radiometer, Raman Lidar) were used to constrain the inversion in terms of the key characteristics of a local aerosol model, including spectral complex refractive index, size distribution, and vertical distribution of aerosol optical parameters. The surface contribution to the polarized radiance was simulated using bidirectional polarized reflectance distribution function (BPDF), which was adjusted using DPC measurements at low altitude. The aerosol optical properties were retrieved using DPC over the Pearl River Delta, and are in good agreement with coincident sun photometer retrievals. The retrieval algorithm of aerosol optical properties using high spatial resolution polarized measurements proposed in this paper shows potential to retrieve the aerosol optical properties over cities. [Copyright &y& Elsevier]

Abstract: Accurate assessment of phytoplankton chlorophyll-a (Chla) concentration in turbid waters by means of remote sensing was challenging due to the optical complexity of turbid waters. Recently, a conceptual model containing reflectance in three spectral bands in the red and near-infrared range of the spectrum was suggested for retrieving Chla concentrations in turbid productive waters. The objective of this paper was to evaluate the performance of this three-band model to estimate Chla concentration in the Pearl River Estuary (PRE), China. Reflectance spectra of surface water and water samples were collected concurrently. The samples contained variable Chla (4.80–92.60 mg/m3) and total suspended solids (0.4–55.2 mg/L dry wt). Colored dissolved organic matter (CDOM) absorption at 400 nm was 0.40–1.41 m−1; turbidity ranged from 4 to 25 NTU (Nephelometric Turbidity Units). The three-band model was spectrally calibrated by iterative and least-square linear regression methods to select the optimal spectral bands for the most accurate Chla estimation. Strong linear relationships (, RMSE=1.4 mg/m3, ) were established between measured Chla and the levels obtained from the calibrated three-band model , where was the reflectance at wavelength . The calibrated three-band model was independently validated (, RMSE=6.44 mg/m3, ) and applied to retrieve Chla concentrations from the calibrated EO-1 Hyperion reflectance data in the PRE on December 21, 2006. The EO-1 Hyperion-derived Chla concentrations were further validated using synchronous in situ data collected on the same day (, RMSE=2 mg/m3, ). The spatial tendency of Chla distribution mapping by Hyperion showed gradually increased concentrations of Chla farther from the river mouths (although decreasing from east to west), which were disturbed by the combination of river outlets and tidal current in Lingding Bay of the PRE. This observation conformed to previous observations and studies, and could reasonably be explained by geographical changes. Also, results indicated that the slope of the three-band regression line decreased as the Chla concentration increased, resulting in the first sensitive band of the three-band model to move towards short wavelengths. These findings validated the rationale behind the conceptual model and demonstrated the robustness of this algorithm for Chla retrieval from in situ data and the Hyperion satellite sensor in turbid estuarine waters of the PRE, China. [Copyright &y& Elsevier]

Abstract: Radiocarbon can serve as a powerful tool for identifying sources of organic carbon and evaluating the erosion intensity in river drainage basins. In this paper we present 14C-AMS measurements of particulate organic carbon (POC) collected from the three major tributaries of the Zhujiang (Pearl River) system: the Xijiang (Western River), Beijiang (Northern River) and Dongjiang (Eastern River) rivers. Furthermore, we discuss the distribution of POC 14C apparent ages and the related watersheds erosion of these rivers. Results yield Δ14C values of −425‰ to −65‰ which indicate that the 14C apparent ages of suspended POC in the entire area are in the range of 540–4445years. The POC apparent ages from Xijiang are mostly between 2000 and 4000years, while in Dongjiang they mostly range from 540 to 1010years. These 14C apparent ages indicate that the watershed erosion of the Xijiang is more severe than that of the Dongjiang. This is in agreement with other data showing deeper erosion in Xijiang due to human activities. [Copyright &y& Elsevier]

Summary: This paper presents a method for regional frequency analysis and spatio-temporal pattern characterization of rainfall-extreme regimes (i.e. extremes, durations and timings) in the Pearl River Basin (PRB) using the well-known L-moments approach together with advanced statistical tests including stationarity test and serial correlation check, which are crucial to the valid use of L-moments for frequency analysis. Results indicate that: (1) the entire Pearl River Basin (40 sites) can be categorized into six regions by cluster analysis together with consideration of the topography and spatial patterns of mean precipitation in the basin. The results of goodness-of-fit measures indicate that the GNO, GLO, GEV, and PE3 distributions fit well for most of the basin for different HOM regions, but their performances are slightly different in term of curve fitting; (2) the estimated quantiles and their biases approximated by Monte Carlo simulation demonstrate that the results are reliable enough for the return periods of less than 100years; (3) excessive precipitation magnitude records are observed at Guilin region of Guangxi Province and Fogang region of Guangdong Province, which have sufficient climate conditions (e.g. precipitation and humidity) responsible for the frequently occurred flood disasters in the regions. In addition, the spatial variations of precipitation in different return periods (Return period=1, 10, 50years to 100years) increase from the upstream to downstream at the regional scale; (4) the seasonal patterns of precipitation extremes for different topographical regions are different. The major precipitation events of AM1R, AM3R, AM5R and AM7R in regions of low-elevation in lower (south-eastern) part of the basin occur mainly in May, June, July and August, while the main precipitation periods for the mountainous region upstream are June, July and August. Further analysis of the NCAR/NCEP reanalysis data indicates that the eastern Asian summer monsoon and typhoons (or hurricanes) are major metrological driving forces on the precipitation regimes. Additionally, topographical features (i.e. elevation, distance to the sea, and mountain’s influences) also exert different impacts on the spatial patterns of such regimes. To the best of our knowledge, this study is the first attempt to conduct a systematic regional frequency analysis on various annual precipitation extremes (based on consecutive 1-, 3-, 5-, 7-day averages) and to establish the possible links to climate pattern and topographical features in the Pearl River Basin and even in China. These findings are expected to contribute to exploring the complex spatio-temporal patterns of extreme rainfall in this basin in order to reveal the underlying linkages between precipitation and floods from a broad geographical perspective. [Copyright &y& Elsevier]

In this paper, we analyzed the high/low water levels of eight stations along the Pearl River estuary and the high/low tidal levels of Sanzao station, and streamflow series of Sanshui and Makou stations using wavelet transform technique and correlation analysis method. The behaviors of high/low water levels of the Pearl River estuary, possible impacts of hydrological processes of the upper Pearl River Delta and astronomical tidal fluctuations were investigated. The results indicate that: (1) the streamflow variability of Sanshui and Makou stations is characterized by 1-year period; 1-, 0.5- and 0.25-year periods can be detected in the high tidal level series of Sanzao station, which reflect the fluctuations of astronomical tidal levels. The low tidal level series of Sanzao station has two periodicity elements, i.e. 0.5- and 0.25-year periods; (2) different periodicity properties have been revealed: the periods of high water levels of the Pearl River estuary are characterized by 1-, 0.5- and 0.25-year periods; and 1-year period is the major period in the low water levels of the Pearl River estuary; (3) periodicity properties indicate that behaviors of low water levels are mainly influenced by hydrological processes of the upper Pearl River Delta. High water levels of the Pearl River estuary seem to be affected by both hydrological processes and fluctuations of astronomical tidal levels represented by tidal level changes of Sanzao station. Correlation analysis results further corroborate this conclusion; (4) slight differences can be observed in wavelet transform patterns and properties of relationships between high/low water levels and streamflow changes. This can be formulated by altered hydrodynamic and morphodynamic processes due to intensifying human activities such as construction of engineering infrastructures and land reclamation. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with identifying the spatial and temporal patterns in the annual maximum and minimum water level in the Pearl River Delta (PRD) region. The Mann–Kendall test and Pettitt test are used to detect trends and abrupt change points, and the Trend Free Pre-Whitening (TFPW) approach then eliminates the effect of serial correlation in data series with significant autocorrelation. Approximately fifty years of the annual hydrological variables from 18 stations in the three major rivers (the West River, the North River, and the East River) are examined. The changing trends of the extremes in water level show different features in different parts of the PRD region. Generally speaking, in the upper part of the delta, the water levels show a decreasing trend while in the middle and lower part there is an increasing trend. This spatial pattern of the extreme water level variation is unlikely to be due to a long-term change in stream flow in the PRD region because the water level changes do not always coincide with the extreme stream flow variations. Sand excavation initiated in the 1980s and continuing for more than 20years in almost all tributaries around the PRD region is one of the most serious intensive human activities affecting water levels. The result of the Pettitt test indicates that most abrupt change points occurred in 1980s–1990s, which reveals that sand excavation and channel regulation are likely to have been the most significant factors contributing to the change over this period. These anthropogenic activities modify the annual extreme water level dramatically in a way that affects the morphology of river channels and estuaries of the PRD and also the redistribution of discharge. However, there are differences in the geographic locations of significant trends for the water level investigated, which implies that these impacts are not spatially uniform. [Copyright &y& Elsevier]

Abstract: The identification of a deeply-buried petroleum-source rock, owing to the difficulty in sample collection, has become a difficult task for establishing its relationship with discovered petroleum pools and evaluating its exploration potential in a petroleum-bearing basin. This paper proposes an approach to trace a deeply-buried source rock. The essential points include: determination of the petroleum-charging time of a reservoir, reconstruction of the petroleum generation history of its possible source rocks, establishment of the spatial connection between the source rocks and the reservoir over its geological history, identification of its effective source rock and the petroleum system from source to trap, and evaluation of petroleum potential from the deeply-buried source rock. A case study of the W9-2 petroleum pool in the Wenchang A sag of the Pearl River Mouth Basin, South China Sea was conducted using this approach. The W9-2 reservoir produces condensate oil and gas, sourced from deeply-buried source rocks. The reservoir consists of a few sets of sandstone in the Zhuhai Formation, and the possible source rocks include an early Oligocene Enping Formation mudstone and a late Eocene Wenchang Formation mudstone, with a current burial depth from 5000 to 9000m. The fluid inclusion data from the reservoir rock indicate the oil and the gas charged the reservoir about 18–3.5Ma and after 4.5Ma, respectively. The kinetic modeling results show that the main stages of oil generation of the Wenchang mudstone and the Enping mudstone occurred during 28–20Ma and 20–12Ma, respectively, and that the δ13C1 value of the gas generated from the Enping mudstone has a better match with that of the reservoir gas than the gas from the Wenchang mudstone. Results from a 2D basin modeling further indicate that the petroleum from the Enping mudstone migrated upward along the well-developed syn-sedimentary faults in the central area of the sag into the reservoir, but that the petroleum from the Wenchang mudstone migrated laterally first toward the marginal faults of the sag and then migrated upward along the faults into shallow strata. The present results suggest that the trap structure in the central area of the sag is a favorable place for the accumulation of the Enping mudstone-derived petroleum, and that the Wenchang mudstone-derived petroleum would have a contribution to the structures along the deep faults as well as in the uplifted area around the sag. [Copyright &y& Elsevier]

Monthly precipitation data of 42 rain stations over the Pearl River basin for 1960–2005 were analyzed to classify anomalously wet and dry conditions by using the standardized precipitation index (SPI) and aridity index ( I) for the rainy season (April–September) and winter (December–February). Trends of the number of wet and dry months decided by SPI were detected with Mann-Kendall technique. Furthermore, we also investigated possible causes behind wet and dry variations by analyzing NCAR/NCEP reanalysis dataset. The results indicate that: (1) the Pearl River basin tends to be dryer in the rainy season and comes to be wetter in winter. However, different wetting and drying properties can be identified across the basin: west parts of the basin tend to be dryer; and southeast parts tend to be wetter; (2) the Pearl River basin is dominated by dry tendency in the rainy season and is further substantiated by aridity index ( I) variations; and (3) water vapor flux, moisture content changes in the rainy season and winter indicate different influences of moisture changes on wet and dry conditions across the Pearl River basin. Increasing moisture content gives rise to an increasing number of wet months in winter. However, no fixed relationships can be observed between moisture content changes and number of wet months in the rainy season, indicating that more than one factor can influence the dry or wet conditions of the study region. The results of this paper will be helpful for basin-scale water resource management under the changing climate. [ABSTRACT FROM AUTHOR]

In this paper, precipitation concentrations across the Pearl River basin and the associated spatial patterns are analyzed based on daily precipitation data of 42 rain gauging stations during the period 1960–2005. Regions characterized by the different changing properties of precipitation concentration index (CI) are identified. The southwest and northeast parts of the Pearl River basin are characterized by lower and decreasing precipitation CI; the northwest and south parts of the study river basin show higher and increasing precipitation CI. Higher but decreasing precipitations CI are found in the West and East River basin. Comparison of precipitation CI trends before and after 1990 shows that most parts of the Pearl River basin are characterized by increasing precipitation CI after 1990. Decreasing precipitation CI after 1990 (compared to precipitation CI changes before 1990) is observed only in a few stations located in the lower Gui River and the lower Yu River. Significant increasing precipitation CI after 1990 is detected in the West River, lower North River and upper Beipan River. These changes of precipitation CI in the Pearl River basin are likely to be associated with the consequences of the well-evidenced global warming. These findings can contribute to basin-scale water resource management and conservation of ecological environment in the Pearl River basin. [ABSTRACT FROM AUTHOR]

This paper reconstructs the evolutionary history of the Pearl River delta over the last 9000 years and investigates land-sea interaction in a large deltaic complex which formed under the influence of Asian monsoon climate. Specifically, this research examines the delta evolution in the context of three driving mechanisms: (1) rising sea level that influences the available accommodation space, (2) fluvial discharge as influenced by monsoon climate and (3) human activities that alter sedimentation within the deltaic system. Results reveal that the formation of deltaic sequences was initiated as a consequence of rapid sea-level rise between 9000 and 7000 cal. yr BP. The rate of sea-level rise slowed down markedly around 7000 cal. yr BP and sedimentation switched from transgressive to regressive. Initially, both the progradation of the delta plains near the apex and aggradation of delta front sedimentation in the central and lower parts of the receiving basin were fast owing to strong monsoonal-driven runoff. The progradation rate gradually slowed down between 6800 and 2000 cal. yr BP as monsoonal-driven runoff weakened. Rapid shoreline advances during the last 2000 years were the result of significantly increased human activities, a practice that trapped sediments in the encircled tidal flats along the front of delta plains. The evolutionary history of the Pearl River delta demonstrates the interplay between the three driving mechanisms. [ABSTRACT FROM AUTHOR]

Recent studies show that the rapid increases in urbanization and human activities in the PRD region have important impacts on regional air quality. In addition to local anthropogenic emissions which are major driving forces for poor air quality in this region, biomass burning in Southeast Asia has also important contribution on aerosol and ozone concentrations in the PRD region. In this paper, this effect is analyzed by using satellite data, ground measurements and models. MODIS aerosol optical depth (AOD) distribution in March 2006 shows a clear enhancement in AOD between Southeast Asia and the PRD region. With detail wind analysis, two distinguished conditions are classified, i.e., Condition-1 (PRD is under influence of the biomass burning from Southeast Asia) and Condition-2 (PRD is not under influence of the biomass burning from Southeast Asia). The characterizations of aerosol, UV, and ozone in Guangzhou city (located in the PRD region) under these two conditions are analyzed. The analyses suggest that aerosols and CO concentrations are higher in Condition-1 than in Condition-2; while the UV intensity and O3 concentrations are lower in Condition-1 than in Condition-2. This result indicates that in Condition-1, the enhanced aerosol concentrations from the Southeast Asia biomass burning produce reduction of UV intensity, and thus decreases the formation of ozone in Guangzhou. [Copyright &y& Elsevier]

This paper suggests that the rapid increase in urbanization and human activities has important impacts on visibility in the Pearl River Delta (PRD) region. A long-term trend of visibility in Guangzhou (one of the largest cities in PRD) shows that between 1954 and 2006, there is a rapid change in visibility. Between 1954 and 1972, low visibility has the smallest occurrence (less than a few days per year). Between 1972 and 1980, the visibility condition is within a transition period, and the occurrence of low visibility increases rapidly. Between 1980 and 2006, the occurrence of low visibility remains very high (150daysyear−1), suggesting that the city of Guangzhou is often under low-visibility conditions since the 1980s. In order to understand the causes of the low visibility in Guangzhou, we analyze physical and chemical characterizations of a low-visibility event occurring between 15 and 29 November 2005. The analysis suggests that high concentration of aerosol particles is a major cause for the low visibility. The threshold aerosol concentration that is corresponding to the low visibility (<10km) is about 120μgm−3. Further analysis indicates that the relationship between aerosol concentrations and visibility appears in a non-linearity correlation. When aerosol concentrations are very high (above 120μgm−3), the change in visibility is not sensitive to aerosol concentration. By contrast, when aerosol concentrations are <120μgm−3, the change in visibility is very sensitive to aerosol concentrations. This study also shows that absorbing aerosol particles (such as element carbon (EC)) play important roles in the reduction of visibility. In most cases, the extremely low visibility (<2km) is often resulted from high EC concentrations (above 15μgm−3). In averaged condition, small scattering aerosol particles (<1μm in radius) have the largest contribution to the reduction of visibility (about 70%). By contrast, large scattering particles have the smallest contribution to the reduction of visibility. This analysis implies that the persistent low visibility is mainly resulted from small aerosol particles, including both scattering and absorbing particles. In order to improve the visibility in the Guangzhou region, the reduction of small particle emissions is urgently needed. This study suggests that there are two important steps to improve the visibility in Guangzhou. First, the aerosol concentration should be reduced to less than the threshold value (120μgm−3). Second, a further decrease in aerosols from its threshold value will lead to a significant improvement in visibility due to the non-linearity relationship between aerosol and visibility. [Copyright &y& Elsevier]

Rapid land development in rapidly growing countries has created a series of land-use problems. The implementation of sustainable land use can alleviate some of these problems. It needs a set of tools for the exploration, design, modification, illustration, and evaluation of alternative planning scenarios. This paper demonstrates that the integration of cellular automata and agent-based modelling can provide a spatial exploratory tool for generating alternative development patterns. Sustainable development strategies are embedded in the modelling to regulate agents' behaviours. The use of agents can help to represent human-environment interactions in solving complex land-use problems. It is able to examine the effects of different stakeholders in influencing the process of land development. The proposed model has been applied to the simulation of planning scenarios for residential development in a rapidly expanding city in the Pearl River Delta. [ABSTRACT FROM AUTHOR]

In this paper, the occurrence and elimination of eight selected antibiotics mainly for human use, including chloramphenicol, fluoroquinolone, sulfonamide and macrolide groups, were investigated at four sewage treatment plants (STPs) in the Pearl River Delta (PRD), South China. The most frequently detected antibiotics in the present study were ofloxacin, norfloxacin, roxithromycin, erythromycin-H2O (the main degradation product of erythromycin) and sulfamethoxazole. The concentrations of these compounds in raw influents and final effluents at the four STPs ranged from 10 to 1978ngL−1 and from 9 to 2054ngL−1, respectively. The other analytes were detected only in a few samples from the four STPs. Antibiotics could not be eliminated completely at the four STPs, with the highest elimination efficiency reaching to 81%. Analysis of the dissolved daily mass flow showed that fluoroquinolones were mostly eliminated from the sewage, and high concentrations of these compounds were found in secondary sludge. Therefore, it can be concluded that the observed elimination of fluoroquinolones in the STPs was due to their sorption to the sludge, but not biodegradation. Macrolides, especially erythromycin-H2O, were stable in sewage during the treatment process, and in fact even higher concentrations were found in the final effluents than in the raw sewages. Sulfamethoxazole was also found in raw influent and final effluent, indicating that it could withstand different treatment processes in the STPs. Remarkable differences in the daily environmental loads (the sum of the amounts in the final effluent and sludge) of the five most frequently detected antibiotic compounds were found in the range of 0.5–828g at the four STPs. [Copyright &y& Elsevier]

Concerns over the effects of globalisation and liberalisation have intensified the debates over the trajectories and underlying sources of regional inequality. This paper attempts to link macro studies of regional inequality to micro studies of local development and to expand the research on intraprovincial inequality in China to Guangdong Province. First, substantial evidence has been provided to illustrate the extent of polarisation between the Pearl River Delta (PRD) and the periphery, especially since the early 1990s. Second, it has been found that new economic spaces centred on exoproduction centres, high-tech zones, university clusters, and entrepreneurial spaces driven by the domestication of globalisation and the growth of the knowledge economy have emerged as new engines of regional growth. The orthodox notion of the PRD development as externally driven has become obsolete, and a new conceptualisation centred on the knowledge economy and integrated development better explains regional development and polarisation in Guangdong. Finally, the theoretical and policy implications of the research are discussed. The emerging form of regional development in the PRD represents an effort to make the knowledge economy the new engine of regional development and indicates that developing countries such as China are attempting to move beyond being a manufacturing assembler. The emergence of the knowledge economy in the PRD also has important implications for the recent efforts to develop the Greater Pearl River Delta, which needs to pay more attention to global networks for innovation and creativity. Moreover, the emergence of the knowledge economy makes the development of the periphery even more challenging due to the effects of self-reinforcing agglomeration and the constraints of geographical barriers. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines spatial and temporal variations of mesozooplankton abundance, biomass and community structure during three cruises of July 2002 (summer), January 2003 (winter), and April 2003 (spring) in the Pearl River estuary, China. Zooplankton abundance and biomass fluctuated widely and showed distinct heterogeneity in the Pearl River estuary. A total of 154 species were identified during three surveys. The number of zooplankton species richness was strongly linked to salinity. Hierarchical cluster analysis identified three zooplankton groups during this study. Estuarine, neritic and pelagic groups corresponded to the upper, middle and lower reaches in the Pearl River estuary. The difference among groups could be mainly ascribed to changes in the relative contributions of the dominant species. The fluctuations in the zooplankton abundance, biomass and community structure were determined by the interactive effects of freshwater inflow, tidal and coastal currents, chlorophyll a, salinity and temperature. Significant spatial variability in the distribution of zooplankton species, abundance and biomass can be ascribed to the virtual presence of a horizontal gradient in salinity. [Copyright &y& Elsevier]

This paper presents the preliminary results of a modeling study on regional air pollutants transport over the Pearl River Delta (PRD) region of China in fall season (Nov. 2002) on the basis of compiled emission inventories. The advanced regional chemical transport model, STEM-2K1, driven by meso-scale meteorological model MM5, was employed with a nesting technique. Three weather patterns were found in the fall season. Numerical sensitive study indicated that external influence on air quality in PRD was significant and dependent on the transport pattern determined by weather situations. [ABSTRACT FROM AUTHOR]

This paper argues that the Chinese pattern of urbanisation since 1978 is distinguished by dual-track urbanisation – state-sponsored urbanisation and spontaneous urbanisation, and that both tracks contribute significantly to the transformation of the spatial pattern of urbanisation. The Pearl River Delta region is chosen for a detailed analysis of the dual-track urbanisation in post-reform China. It is found that special economic zone (SEZ) cities are leading both state-sponsored and spontaneous urbanisation in the region, which is different from either large city or small town-based urbanisation advocated in the literature. Multivariate statistical analysis shows that factors affecting the two tracks of urbanisation are different and have changed over time. The level of economic development has an important impact on the level of the state-sponsored urbanisation, but is not significant to spontaneous urbanisation. Areas with fewer state owned enterprises (SOEs) have a higher level of spontaneous urbanisation. The non-state sector also became more important in the state-sponsored urbanisation of the 1990s. [ABSTRACT FROM AUTHOR]

China's agricultural reforms and open door policy adopted since 1978 have had impact on the country's economic structure, population characteristics, and urban development. This paper examines the spatial implications of such changes in the light of the development of Zhujiang Delta located in the coastal region of South China. Market-oriented agricultural production, rural industrialization, migration of surplus farm labor, and the spread of small towns in the rural areas are some of the consequences of the reforms and are placed in the perspective of the coreperiphery theory of regional development. It is argued that the hybrid ’center-downward’ and ’periphery-upward’ approach in spatial development was adopted because it was politically more adaptable to the Chinese objectives of economic development, which continue to uphold Marxism, Maoism and Communist Party leadership. Through careful control of the destination of the rural migrants in conjunction with the policy of small town development, China hopes to establish a new spatial relationship between the core and the periphery on more equal footing. Currently the spatial structure of Zhujiang Delta displays a well-integrated network of towns of varying sizes being established to fill in gaps in the settlement hierarchy to effect spread of benefits from the core to its periphery. But contrary to expectations, spatial inequity in development persists as the core has advanced at a much faster pace than its periphery. [ABSTRACT FROM AUTHOR]