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Atmospheric Chemistry and Physics ; 22(8):5495-5514, 2022.
Article Dans Anglais | ProQuest Central | ID: covidwho-1811067

Résumé

PM2.5, generated via both direct emission and secondary formation, can have varying environmental impacts due to different physical and chemical properties of its components. However, traditional methods to quantify different PM2.5 components are often based on online or offline observations and numerical models, which are generally high economic cost- or labor-intensive. In this study, we develop a new method, named Multi-Tracer Estimation Algorithm (MTEA), to identify the primary and secondary components from routine observation of PM2.5. By comparing with long-term and short-term measurements of aerosol chemical components in China and the United States, it is proven that MTEA can successfully capture the magnitude and variation of the primary PM2.5 (PPM) and secondary PM2.5 (SPM). Applying MTEA to the China National Air Quality Network, we find that (1) SPM accounted for 63.5 % of the PM2.5 in cities in southern China on average during 2014–2018, while the proportion dropped to 57.1 % in the north of China, and at the same time the secondary proportion in regional background regions was ∼ 19 % higher than that in populous regions;(2) the summertime secondary PM2.5 proportion presented a slight but consistent increasing trend (from 58.5 % to 59.2 %) in most populous cities, mainly because of the recent increase in O3 pollution in China;(3) the secondary PM2.5 proportion in Beijing significantly increased by 34 % during the COVID-19 lockdown, which might be the main reason for the observed unexpected PM pollution in this special period;and finally, (4) SPM and O3 showed similar positive correlations in the Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD) regions, but the correlations between total PM2.5 and O3 in these two regions, as determined from PPM levels, were quite different. In general, MTEA is a promising tool for efficiently estimating PPM and SPM, and has huge potential for future PM mitigation.

2.
Chinese Journal of Infectious Diseases ; (12): E018-E018, 2020.
Article Dans Chinois | WPRIM (Pacifique occidental), WPRIM (Pacifique occidental) | ID: covidwho-6171

Résumé

Objective@#To analyze the epidemiological and clinical characteristics of patients with 2019 novel coronavirus (2019-nCoV) infection in Shenyang.@*Methods@#The epidemiological and clinical characteristics of 30 patients diagnosed with 2019-nCoV infection admitted to Shenyang sixth people's hospital on January 22, 2020 and February 8, 2020 were retrospectively analyzed.@*Results@#Among the 30 cases, 21 were imported, including 17 from Hubei Province and four from other provinces. Nine cases were local infections. There were 18 men and 12 women, aging from 21 to 72 years with the median of 43 years. Eight cases had underlying diseases including hypertension, diabetes, coronary heart disease and bronchitis. On admission, two (7%) cases were mild, 19 (63%) cases were ordinary, eight (27%) cases were severe, and one (3%) case was critical. Clinical manifestations mainly include fever, with or without upper respiratory tract symptoms, normal, decreased or slightly increased white blood cell counts, mainly decreased lymphocyte counts, normal or increased c-reactive protein, and normal procalcitonin. The computed tomography (CT) of the early stage of the lungs showed that multiple patchy ground glass shadows were mainly accompanied by consolidation, which often involved both lungs or multiple lobes of one lung. At the moment, the clinical treatment mainly included respiratory support, symptomatic treatment, antiviral treatment adn anti-bacterial treatment. By February 15, a total of nine cases were cured and discharged, including one mild case, six ordinary cases, and two severe cases. In the comparisons between mild/ordinary patients and severe/critical patients, the fever duration in the severe/critical group (median 11.5 d) was significantly longer than that in the light/normal group (median 2 d) (Z=-2.292, P=0.022), and the laboratory tests indicated elevated d-dimer levels (Z=-2.669, P=0.008) and more cases with neutrophilic/lymphocyte ratio > 3 (Z=-4.071, P<0.01).@*Conclusions@#In Shenyang, the early cases with 2019-nCoV infection are mainly imported cases, and expanding local infections gradually develop. Clinical manifestations are mainly characterized by fever and cough. Lung CT performance shows multiple ground glass shadows, mainly accompanied by consolidation. CT changes in the lungs should be closely monitored during the treatment, and CT findings in the lungs may change earlier than the clinical manifestations. Prolonged fever duration, elevated d-dimer level and neutrophil/lymphocyte ratio >3 could be used as early warning indicators for severe cases.

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