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Abstract Locations of city features, e.g., city centers, roads, railways, and rivers, may impact urban carbon sinks. Therefore, the effects of city features on spatial variations of urban carbon sinks were investigated using geographic proximity data. The main results were as follows. (1) Carbon sink function varied in a complex manner with distance from the city center and with city size. The carbon sink per unit area increased with distance from the prefecture-level city center (0–30 km), with the dominant influence occurring within a 9 km radius. The lowest carbon sink per unit area was observed at a distance of 12 km from the city center of the provincial capital city (Guangzhou) and special economic zone (Shenzhen), which may be suburban industrial zones. (2) Carbon sinks decreased with increases in road grades as a result of the different functions and traffic flow, and carbon sinks were lowest near city express ways. For highways, carbon sinks were lower near highway entrances and exits. Carbon sinks around ordinary railways were higher than those around subways and light rail, but carbon sink characteristics grew more complex with increasing distances from subways and light rail. (3) Rivers were closely related to the urban layout. Grade I (i.e., larger) rivers were associated with lower carbon sinks, and carbon sink characteristics became increasingly complex around larger rivers. Within a 0–1000 m distance of all rivers, the carbon sink per unit area increased rapidly, but carbon sink characteristics differed slightly for grade I rivers. This study implies that it is important to take urbanization spatial position effects into account while assessing regional carbon sinks during urbanization and development. Highlights • Urban carbon sinks were assessed in the Pearl River Delta region. • Influence of spatial positions of city features on carbon sinks was detected. • The carbon sink per unit area increased with distance from the city centers. • Carbon sinks decreased with increases in road grades. • The locations of rivers also influenced the carbon sinks. The carbon sink per unit area increased with distance from the city centers. Carbon sinks decreased with increases in road grades. The locations of rivers also influenced the carbon sinks. [ABSTRACT FROM AUTHOR]

Integrating synthetic aperture radar (SAR) and optical data to improve urban land cover classification has been identified as a promising approach. However, which integration level is the most suitable remains unclear but important to many researchers and engineers. This study aimed to compare different integration levels for providing a scientific reference for a wide range of studies using optical and SAR data. SAR data from TerraSAR-X and ENVISAT ASAR in both WSM and IMP modes were used to be combined with optical data at pixel level, feature level and decision levels using four typical machine learning methods. The experimental results indicated that: 1) feature level that used both the original images and extracted features achieved a significant improvement of up to 10% compared to that using optical data alone; 2) different levels of fusion required different suitable methods depending on the data distribution and data resolution. For instance, support vector machine was the most stable at both the feature and decision levels, while random forest was suitable at the pixel level but not suitable at the decision level. 3) By examining the distribution of SAR features, some features (e.g., homogeneity) exhibited a close-to-normal distribution, explaining the improvement from the maximum likelihood method at the feature and decision levels. This indicated the benefits of using texture features from SAR data when being combined with optical data for land cover classification. Additionally, the research also shown that combining optical and SAR data does not guarantee improvement compared with using single data source for urban land cover classification, depending on the selection of appropriate fusion levels and fusion methods. [ABSTRACT FROM AUTHOR]

Environmental flow is fundamental to ecological health and integrity of a riverine environment. River delta systems have become more and more complicated due to climate change and human activities and these have made a significant impact on significant changes in hydrological processes and the ecological environment. Highly intense human activities and most economically developed regions in the Pearl River Delta (PRD), China, was selected as case study. Based on observed daily flow data with a length of 50 years from seven control stations, inter-annual and intra-annual streamflow alterations in this region were analyzed by using the indicators of hydrologic alteration (IHA) method, the range of variability approach (RVA), and the histogram matching approach (HMA), and quantitative impact of main factors on inter- and intra-annual streamflow alterations were derived. Results showed the following: (1) Combination of RVA and HMA can better reveal changes of IHAs, so as to more comprehensively evaluate environmental flow alteration of river systems. (2) Discharge diversion due to changes in river channel geometry is the main factor causing inter-annual streamflow alteration in the Northwest River of PRD, whose contributions were 122.35% and 90.08% at Makou and Sanshui stations, respectively. (3) Change in upstream flow is the main factor causing intra-annual streamflow alteration in the Northwest River of PRD, while reservoir operation is the main factor causing intra-annual streamflow alteration in the East River of PRD. (4) Climate change and reservoir operation can make intra-annual distribution of monthly discharge more concentrate and even, respectively. This study contributes to an improved understanding of environmental flow alteration and associated underlying causes of flow regime variations in the river delta region. [ABSTRACT FROM AUTHOR]

Abstract: Ten antibiotics belonging to three groups (macrolides, fluoroquinolones and sulfonamides) were investigated in riverine runoff of the Pearl River Delta (PRD) and Pearl River Estuary (PRE), South China for assessing the importance of riverine runoff in the transportation of contaminants from terrestrial sources to the open ocean. All antibiotics were detected in the eight outlets with concentrations ranging from 0.7 to 127 ng L−1. The annual mass loadings of antibiotics from the PRD to the PRE and coast were 193 tons with 102 tons from the fluoroquinolone group. It showed that antibiotics decreased from the riverine outlets to the PRE and open ocean. Risk assessment showed that most of these antibiotics showed various ecological risks to the relevant aquatic organisms, in which ofloxacin (OFL), erythromycin (ETM) and ciprofloxacin (CIP) posed high ecological risks to the studied aquatic environments. [Copyright &y& Elsevier]

Polychlorinated naphthalenes (PCNs) are now under review by the Stockholm Convention as a candidate for POPs for their persistence, toxicity, bioaccumulation, and long-range atmospheric transport. Data regarding PCN levels and their environmental fate are sparse in China. The PCN concentration and distribution in soils of the Pearl River Delta were reported, and the average total concentration was 59.9 ± 86.7 pg/g. Tri-CNs was the dominant homologue group, and CN 24 was the most abundant congener. A gradient of PCN levels between more and less developed areas was observed. Based on fugacity fraction results, CN 51 is proposed as a possible source marker for specific combustion emissions. Air-soil exchange of PCNs was estimated by calculating the soil and air fugacity. Fugacity fraction values indicated that tri- to penta-CNs were closer to equilibrium in winter and toward net volatilization in summer, while hexa-CNs experienced net air-to-soil transfer in both seasons. [Copyright &y& Elsevier]

Abstract: The Pearl River Delta (PRD) in Southern China is a region where the manufacturing industry is rapidly developing, accounting for about 10% of the gross domestic product (GDP) with 4% of China''s population. The economic development in this region is accompanied by severe air pollution that poses harm to people''s health and causes economic loss. This paper estimates the adverse health effects of particulate matter pollution in the PRD by using a log-linear exposure–response function, and monetizes the morbidity effect by using the cost of illness (COI) method and the mortality effects by using both the amended human capital (AHC) method and the results of contingent valuation (CV) study. The results show that in 2006 the total economic loss of the health effects from PM10 pollution in PRD is 29.21 billion Chinese yuan by using CV results and COI method, which is equivalent to 1.35% of the regional GDP, and is 15.51 billion Chinese yuan by using AHC and COI methods, which is equivalent to 0.72% of the regional GDP. The economic loss due to premature death and chronic respiratory disease accounts for more than 95% of the total loss. Despite the uncertainties, the results clearly show the severity of the health effects and economic loss incurred by particulate matter pollution in PRD; the results further point to the need for developing environmentally friendly industry, and provide a benchmark for comparing alternative options to reduce air pollution. [Copyright &y& Elsevier]

Length-weight relationships ( LWRs) were estimated for eight native fish species collected in the lower reaches of the Pearl River, Guangdong Province, South China. Fish were sampled in March and September 2014 and January 2015, using gillnets with various mesh sizes (5-8 cm) and trawl nets with a 3 cm mesh size. A total of 568 specimens of the eight species were analyzed. The r 2 values for these species ranged from 0.951 to 0.991. The b values ranged from 3.00 for Takifugu ocellatus and Moolgarda cunnesius, to 3.57 for Clupanodon thrissa. New maximum total lengths are recorded for Takifugu ocellatus (17.6 cm) and Liza carinata (24.4 cm). For five species ( Clupanodon thrissa, Megalobrama terminalis, Collichthys lucidus, Coilia grayii, Takifugu ocellatus), the LWRs are presented to fishbase for the first time. [ABSTRACT FROM AUTHOR]