[Effect of Biomass Burning on Carbonaceous Aerosol Composition and Light Absorption in Guangxi Regional Background Site].

Carbonaceous aerosols are an important component of fine particulate matter (PM2.5) in the atmosphere, having great impacts on air quality, human health, and the climate. In this study, PM2.5 samples were collected from November 2017 to October 2018 in a background site of Guangxi Province to investigate the potential impacts of biomass burning, an essential source of carbonaceous aerosols, on carbonaceous aerosols. Further, the composition of carbonaceous aerosols, sugar compounds, and the light absorption coefficient (babs) of water-soluble brown carbon (BrC) were also conducted. Considering the effect of the degradation of atmospheric levoglucosan (LG), the concentration of the corrected LG was quantified using the aging of air masses (AAM) index. Then, the contribution of biomass burning (BB) to organic carbon (OC) [BB-OC] was quantified using the corrected LG-derived molecular tracer method combined with the Bayesian mixing model. Here, we further explored the potential sources of water-soluble BrC using correlation analysis. In this research, the mean AAM index was 0.40±0.28 during the study period, indicating that the atmospheric LG had undergone a photochemical degradation process. The characteristic ratio combined with the Bayesian mixing model indicated that the crop straw (i.e., corn, rice, and sugarcane straw) was the dominant biomass fuel type in the Guangxi Region, contributing 22%, 23%, and 18% of OC without the correction of LG and 16%, 21%, and 17% with the corrected LG concentration, respectively. The neglection of LG degradation led to the underestimation of BB-OC, in which the BB-OC values with and without correction were 49.0% and 21.1%, respectively. Here, the annual mean babs of water-soluble BrC was (8.7±10.7) Mm-1, and its main sources were BB, fossil fuel combustion, and vegetation emission.

[Simultaneous determination of six rare sugars in solid foods by high performance liquid chromatography-evaporative light-scattering detection].

Excessive sugar consumption is associated with metabolic health problems. Rare sugars are gradually being used as substitutes for sugar, and their consumption is increasing daily, raising food-safety issues such as false advertising, adulteration, and overdosing. The determination of rare-sugar compounds has attracted considerable attention in recent years. However, no standard method for the simultaneous determination of six rare sugars (allulose, tagatose, trehalose, isomaltulose, erythritol, and mannitol) in solid foods is available. Therefore, establishing a suitable analytical method for these sugars is necessary. In this study, high performance liquid chromatography coupled with evaporative light-scattering detection was used to determine rare sugars in solid foods. The optimum chromatographic and detector conditions were determined by evaluating the instrument parameters. Analysis was carried out on a Zorbax Original NH2 column (250 mm×4.6 mm, 5 µm) via flow-rate gradient elution (0-15 min, 1.0 mL/min; 15-18 min, 1.0-2.0 mL/min; 18-25 min, 2.0 mL/min) with acetonitrile-water (80∶20, v/v) as the mobile phase. Sharp and symmetric chromatographic peaks were obtained under these conditions. The resolutions for all the six rare sugars were greater than 1.5. Optimization of the evaporative light-scattering detector was extremely important to the responses of the rare-sugar compounds. The two most significant parameters were the nebulizer carrier gas flow rate and drift tube temperature. The detection system was operated under the following conditions: the drift tube temperature was set to 50 ℃, the nebulizer carrier gas was high-purity nitrogen, the carrier gas flow rate was 1.0 mL/min, the nitrogen pressure was regulated to 275.79 kPa, and the gain factor was set to 3. The sample was extracted with 25 mL of water, shaken and vortexed for 10 min, purified with 200 µL of zinc acetate solution and 200 µL of potassium ferricyanide solution, and centrifuged at 4500 r/min for 10 min. Next, 1 mL of the supernatant was passed through a 0.22 µm aqueous-phase filter membrane, and the filtrate obtained was analyzed using the evaporative light-scattering detector. The six rare sugars were quantitatively analyzed using the external standard method and showed good linearity with coefficients of determination (R2) greater than 0.9985. The limits of detection and quantification were 0.020-0.60 and 0.60-1.8 g/100 g, respectively. In addition, when blank solid food samples were spiked with the analytes at three levels, the average recoveries of the six rare sugars were 92.6%-103.2%, with relative standard deviations (RSDs) of 0.7%-4.4%. An RSD of <5% indicated that the method had good precision. Interference experiments were performed to determine whether the sugars and artificial sweeteners commonly found in solid foods affected the targets. The method established in this study was used to analyze the contents of the six rare sugars in actual solid food samples. The experimental results showed various levels of rare glycoconjugates in different solid foods. Moreover, the actual compositions and labeled of rare glycoconjugates in the solid foods were generally consistent. The proposed method features simple operation, rapid results, high sensitivity, and good reproducibility; thus, it meets the requirements for the detection of the six rare sugars in solid foods. It also provides technical support for the development of methodological standards and detection limits for rare sugars in Chinese foods. The results of this study are of great relevance for the daily monitoring of the levels of the six rare sugars in solid foods.

[Changes in Carbonaceous Aerosol in the Northern Suburbs of Nanjing from 2015 to 2019].

Carbonaceous aerosol is an important component of atmospheric fine particles that has an important impact on air quality, human health, and climate change. In order to explore the long-term changes in carbonaceous aerosol under the background of emission reduction, this study measured the mass concentrations of organic carbon (OC) and elemental carbon (EC) of PM2.5, which collected in the northern suburbs of Nanjing for five years (December 17, 2014 to January 5, 2020). The results showed that the five-year average ρ(OC) and ρ(EC) were (10.2±5.3) µg·m-3 and (1.6±1.1) µg·m-3, accounting for 31.1% and 5.2% of PM2.5, respectively. OC and EC concentrations were both high in winter and low in summer. According to the nonparametric Mann-Kendall test and Sen's slope, the mass concentrations of OC and PM2.5 decreased significantly[OC:P<0.0001, -0.79 µg·(m3·a)-1, -0.29%·a-1; PM2.5:P<0.0001, -4.59 µg·(m3·a)-1, -1.58%·a-1]. Although EC had an upward trend, the significance and range of change were not obvious[P=0.02, 0.05 µg·(m3·a)-1, 0.02%·a-1]. OC and EC decreased significantly during winter from 2014 to 2019[OC:P<0.0001, -2.05 µg·(m3·a)-1, -0.74%·a-1; EC:P=0.001, -0.15 µg·(m3·a)-1, -0.05%·a-1], and the decline was more obvious than the whole. The correlation between OC and EC showed that the sources in winter and summer were more complex than those in spring and autumn. According to the characteristic ratio of OC and EC, the contribution of coal combustion and biomass burning decreased from 2015 to 2019, whereas the impact of industrial sources and vehicle emissions became more significant. Corresponding to this was the obvious decline in OC and the slight recovery of EC. The OC/EC ratio was over 2.0, indicating that there was secondary pollution in the study area. Further calculation revealed that the variation in SOC was consistent with that in OC, showing a significant decrease[P<0.0001, -0.47 µg·(m3·a)-1, -0.17%·a-1]. The average mass concentration of SOC was (5.0±3.5) µg·m-3, accounting for 49.2% of OC. These changes indicate clear effects of the prevention and control of air pollution in Nanjing in recent years. Furthermore, future control can focus on the emissions of VOCs to reduce secondary pollution.

[Organic Aerosols and Source Analysis of Fine Particles in the Background of Shiwanda Mountain, Guangxi].

The non-polar compounds in atmospheric fine particles (PM2.5) mainly include polycyclic aromatic hydrocarbons (PAHs) and normal alkanes (n-alkanes), etc., which are usually used to identify the source of the air pollution and have a great important impact on human health and the environment. To study the pollution characteristics and sources of non-polar organic aerosols in the background point PM2.5 in Guangxi, from November 2017 to October 2018, 17 types of PAHs and 20 types of n-alkanes were analyzed on PM2.5 samples collected in the field. It was found that the annual average concentrations of PAHs and n-alkanes were 4.28±4.25 ng·m-3 and 13.7±14.72 ng·m-3, respectively. The seasonal change was as follows:winter[(7.86±5.19) ng·m-3, (27.51±16.90) ng·m-3]>spring[(2.73±1.76) ng·m-3, (7.64±4.71) ng·m-3]>autumn[(2.34±145) ng·m-3, (7.01±4.55) ng·m-3]>summer[(1.91±1.67) ng·m-3, (3.98±3.12) ng·m-3]. In PAHs, 5-ring and 6-ring molecules accounted for more than 60%, followed by low- and medium-ring molecules (4-ring and 3-ring). The high molecular weight of n-alkanes was relatively high (C29>C31>C27), and the odd and even carbon numbers were significantly different. In addition, combined with the feature ratio method, principal component analysis method, and backward trajectory joint verification, it was found that 41.5% of non-organic aerosols in winter were affected by maritime traffic emissions and ocean source transportation, and 36.7% of the pollution was explained by the coal burning and local biomass burning; 25.2% of the pollution in spring came from biomass combustion and transportation, and 45.0% was attributed to marine transportation in the southern part of the study area and higher plant wax emissions pollution; 53.4% of pollution in summer came from polluted ship emissions, and 10.6% of pollution came from transportation in Southwest Thailand Source transportation. The organic aerosols at the background sites in Guangxi were affected by the combined effects of local emissions and transmission sources.

Comparison of the Wells score with the revised Geneva score for assessing suspected pulmonary embolism: a systematic review and meta-analysis.

The Wells score and the revised Geneva score are two most commonly used clinical rules for excluding pulmonary embolism (PE). In this study, we aimed to assess the diagnostic accuracy of these two rules; we also compared the diagnostic accuracy between them. We searched PubMed and Web of science up to April 2015. Studies assessed Wells score and revised Geneva score for diagnosis suspected PE were included. The summary area under the curve (AUC) and the 95 % confidence interval (CI) were calculated. Eleven studies were included in this meta-analysis. For Wells score, the sensitivity ranged from 63.8 to 79.3 %, and the specificity ranged from 48.8 to 90.0 %. The overall weighted AUC was 0.778 (95 % CI 0.740-0.818; Z = 9.88, P < 0.001). For revised Geneva score, the sensitivity ranged from 55.3 to 73.6 %. The overall weighted AUC was 0.693 (95 % CI 0.653-0.736; Z = 11.96, P < 0.001). 95 % CIs of two AUCs were not overlapped, which indicated Wells score was more accurate than revised Geneva score for predicting PE in suspected patients. Meta-regression showed diagnostic accuracy of these two rules was not related with PE prevalence. Sensitivity analysis by only included prospective studies showed the results were robust. Our results showed the Wells score was more effective than the revised Geneva score in discriminate PE in suspected patients.