Quantitative method for resilience assessment framework of airport network during COVID-19.

The resilience and vulnerability of airport networks are significant challenges during the COVID-19 global pandemic. Previous studies considered node failure of networks under natural disasters and extreme weather. Herein, we propose a complex network methodology combined with data-driven to assess the resilience of airport networks toward global-scale disturbance using the Chinese airport network (CAN) and the European airport network (EAN) as a case study. The assessment framework includes vulnerability and resilience analyses from the network- and node-level perspectives. Subsequently, we apply the framework to analyze the airport networks in China and Europe. Specifically, real air traffic data for 232 airports in China and 82 airports in Europe are selected to form the CAN and EAN, respectively. The complex network analysis reveals that the CAN and the EAN are scale-free small-world networks, that are resilient to random attacks. However, the connectivity and vulnerability of the CAN are inferior to those of the EAN. In addition, we select the passenger throughput from the top-50 airports in China and Europe to perform a comparative analysis. By comparing the resilience evaluation of individual airports, we discovered that the factors of resilience assessment of an airport network for global disturbance considers the network metrics and the effect of government policy in actual operations. Additionally, this study also proves that a country's emergency response-ability towards the COVID-19 has a significantly affectes the recovery of its airport network.

[Residues and health risk assessment of HCHs, DDTs and heavy metals in water and Tilapias from fish ponds of Guangdong].

Concentrations of copper, lead, cadmium, arsenic, hexachlorcyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in the water and the fish samples collected separately from fish pond, markets and supermarkets in four cities of Guangdong Province were measured by using GC-ECD, flame atomic absorption spectrometry and atomic fluorescence spectrometry. Health risk assessments associated with Cu, Pd, Cd, As, HCHs and DDTs were conducted based on the model of health risk assessment recommended by the US EPA. The results showed that the concentration ranges of Cu, Pd, Cd, As, HCHs and DDTs in water samples were nd-0.101 mg x L(-1), nd-0.097 mg x L(-1), nd-0.003 27 mg x L(-1), 0.0121-0.08127 mg x L(-1), 2.63-37.18 ng x L(-1) and 2.05-12.21 ng x L(-1), respectively. The health risk assessment indicates that the carcinogenic and non-carcinogenic risks of Cu, Pd, Cd, HCHs and DDTs in Tilapias both lower than the highest acceptable level of risk set by ICRP, but As cancer risk value slightly exceeded the upper limit of the acceptable risk levels in city population.

[Residues and potential ecological risk assessment of metal in sediments from lower reaches and estuary of Pearl River].

In order to investigate the heavy metal concentrations and their potential ecological risks in surface sediments of lower reaches and estuary of Pearl River, 21 bottom sediment samples were collected from lower reaches and estuary of Pearl River. Total contents of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Pb and Hg in these samples were measured by the inductively coupled plasma mass spectrometry (ICP-MS) and the atomic fluorescence spectrometry (AFS) and using the index of geoaccumulation and the potential ecological risk index to evaluate the pollution degree of heavy metals in the sediments. Results indicated that the concentration of total Fe and total Mn were 41658.73 and 1104.73 mg x kg(-1) respectively and toxic trace metals, such as Cr, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Pb and Hg were 86.62, 18.18, 54.10, 80.20, 543.60, 119.55, 4.28, 10.60, 20.26, 104.58 and 0.520 mg x kg(-1). The descending order of pollution degree of various metals is: Cd > As approximately Zn > Hg > Pb approximately Cu approximately Cr, while the single potential ecological risk followed the order: Cd > Hg > As > Cu > Pb > Zn > Cr. The pollution extent and potential ecological risk of Cd were the most serious among all heavy metals. The distribution pattern of Cd individual potential ecological risk indices is exactly the same as that of general potential ecological risk indices for all heavy metals. Clustering analysis indicates that the sampling stations may be classified into five groups which basically reflected the characteristics of the heavy metal contamination and sedimentation environments along the different river reaches in lower reaches and estuary of Pearl Rive. In general, the serious heavy metal pollution and the high potential ecological risk existed in three river reaches: Chengcun-Shawan, Chengcun-Shundegang and Waihai-Hutiaomen. The pollution degree and potential ecological risk are higher in related river reaches of Beijiang than that in other lower reaches and estuary of Pearl River.