COVID-19 control measures had a significant social and economic impact in Guangdong Province, and provided a unique opportunity to assess the impact of human activities on air quality. Based on the monitoring data of PM2.5, PM10, NO2, and O3 concentrations from 101 air quality monitoring stations in Guangdong Province from October 2019 to April 2020, the PSCF (potential source contribution factor) analysis and LSTM (long short-term memory) neural network were applied to explore the impact of epidemic control measures on air quality in Guangdong Province. Results showed that during the lockdown, the average concentration of PM2.5, PM10, NO2, and O3 decreased by 37.84%, 51.56%, 58.82%, and 24.00%, respectively. The ranges of potential sources of pollutants were reduced, indicating that air quality in Guangdong Province improved significantly. The Pearl River Delta, characterized by a high population density, recorded the highest NO2 concentration values throughout the whole study period. Due to the lockdown, the areas with the highest concentrations of O3, PM2.5, and PM10 changed from the Pearl River Delta to the eastern and western Guangdong. Moreover, LSTM simulation results showed that the average concentration of PM2.5, PM10, NO2, and O3 decreased by 46.34%, 54.56%, 70.63%, and 26.76%, respectively, which was caused by human-made impacts. These findings reveal the remarkable impact of human activities on air quality and provide effective theoretical support for the prevention and control of air pollution in Guangdong Province.
The salt deposits in Vientiane Plain occurrence in Palaeocene Tagong Formation.The main Kalium-bearing minerals are carnallite and a little of sylvinite.During mineralization period,the Tagong Formation and salt deposits were controlled by NW-trending boundary faults and Tagong syncline.After mineralization period,the salt deposits were controlled by fold(salt syncline and salt anticline).The salt deposits formed broad and gentle fold under the horizontal stress.Inside syncline,deposition rate is relatively quickly and the thickness of clastic rocks upper salt seam is relatively large.On anticline,the thickness of clastic rocks upper salt seam is relatively thin.There are large density differences between salt deposits and clastic rocks,and the thickness of clastic rocks in the anticline is different from the one in syncline,so the salt deposits form differential loading.The salt deposits in syncline happened plastic flow towards anticline by larger loading.Thus the salt deposits in anticline become thicker,salt anticline form.The thickness of salt deposits in syncline becomes smaller.Thickness of the salt deposits in anticline is often great;its burial depth is shallow.The strata over anticline are often incomplete.With the salt anticline far development,the potash deposits pierce upper mudstone and expose oneself to relatively freshwater surroundings to suffer corrosion.
The rapid modernization in China has aggravated the reduction of the traditional settlements and aroused concern about the protection and research. This study aims to examine the spatial-temporal variations Tujia traditional settlements in China and to delineate the driving mechanism of the settlement distribution. Previous studies have focused on the characteristics of settlements in provincial or smaller areas, providing lacked information regarding spatial distribution heterogeneity of Tujia traditional settlements in China. In this study, the spatial heterogeneity and influence factors of the distribution of traditional Tujia settlements were examined using the GIS platform and statistical methods. The results reveal that the spatial distribution of settlements exhibits clustering with the pattern of “scattered distribution in a large region, while concentrated in small areas”. The settlements were generally built in low hills, gentle slopes, sunny slopes and low-relief terrain areas, with elevation, relief degree of land surface (RDLS), slope and aspect were the key factors affecting the distribution. In Song, Yuan, Ming and Qing dynasties, settlements showed significant clustering all through, though the location and number of clustering center kept changing. In this process, the history of the Tujia chieftain and the transportation and marketing lines of Sichuan salt had a profound influence on the historical evolution of the settlement.
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