Search

ObjectiveTo understand the characteristics of PM2.5 pollution in the air of Pearl River Delta city in Guangdong Province under the COVID-19 epidemic and the health risks of inhaling elements in PM2.5.MethodsIn 2022， 10 PM2.5 monitoring points were set up in 10 districts in Guangzhou， Shenzhen， Foshan and Zhuhai， and air samples were collected for 7 consecutive days every month to analyze the concentration of PM2.5 and the 12 elements in PM2.5. The classic "four-step" method was used to evaluate the carcinogenic risk and chronic non-carcinogenic risk of the elements in air PM2.5 on health. The age-sensitive characteristics of metal elements were combined in the carcinogenic risk assessment， and age-sensitive factors were introduced to analyze the impact of air pollution on population health.ResultsA total of 818 samples were collected. and the average annual PM2.5 concentration in the four cities of the Pearl River Delta was 30.17 （1.00-166.00， s=21.06） μg·m-3， which was lower than the concentration limit of the secondary standard of the Ambient Air Quality Standard （GB 3095-2012）. The difference of PM2.5 concentration in the four cities was statistically significant. The PM2.5 concentrations in Zhuhai and Shenzhen， which were located near the sea， were lower than those in Guangzhou and Foshan. The monthly mean concentration of PM2.5 in the four cities was the lowest at 13.70 （4.00-34.00， s=5.93） μg·m-3 in July and the highest at 57.73 （14.00-146.00， s=27.96） μg·m-3 in January， showing a low concentration from May to October and a high concentration from November to April of the following year. The average daily PM2.5 concentration exceeded the secondary standard for 29 days， mainly distributed in January and November. The average annual mass concentration of elements in PM2.5 in the four cities was Al>Mn>Pb>As>Ni>Cr>Se>Sb>Cd>Tl>Be>Hg. AS and Mn have chronic non-carcinogenic risk in population， while Cr， AS， Cd， Be and Ni have carcinogenic risk in population.ConclusionThe PM2.5 pollution levels of the four cities in the Pearl River Delta are low and variable. Coastal cities are lower than non-coastal cities， which shows the characteristics of first decreasing and then increasing throughout the year. The order of mass concentration of metal elements of PM2.5 in four cities is basically the same except Be and Ni. As and Mn in PM2.5 show a certain degree of chronic non-carcinogenic risk， and As， Cr， Cd， Ni and Be have a certain degree of carcinogenic risk. The four cities need to take effective intervention measures to continue to strengthen the pollution control and health protection of Cr， As， Cd and Mn in the air， and control the health burden caused by air pollution.

Short carbon fiber is a promising candidate for reinforcing carbon‐containing refractories at the macro scale due to its excellent high‐temperature stability and mechanical properties. In this work, the microstructure evolution of short carbon fiber and the effect of its addition on the properties of Al2O3–C refractories are investigated. The results show that adding short carbon fiber could affect the distribution of in situ ceramic phases, combined with the cross‐scale reinforcement effect, leading to high strength—the CMOR of short carbon fiber containing refractories could be 23.0% higher than the free ones, while the HMOR could be 22.0% higher. Furthermore, the results suggest that the short carbon fiber containing refractories treated at 1400°C possesses high resistance to the initiation of crack propagation, which could be attributed to the high bonding strength brought by carbon fiber. Noteworthy, adding short carbon fiber could improve thermal shock resistance. The short carbon fiber containing refractories treated at 1300°C could possess a higher residual strength ratio than free ones. For instance, the specimen containing 0.1 wt% short carbon fiber shows the highest residual strength ratio (87.7%). [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) for erythromycin (ERY) were prepared by precipitation polymerization, using ERY as template molecule, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker and methanol/acetonitrile (1:4, v/v) as porogens. The characterization of the prepared MIPs and non-imprinted polymers (NIPs) were evaluated by scanning electron microscope (SEM) and equilibrium adsorption experiment. The results showed that the MIPs possessed the specific adsorptivity toward ERY. Scatchard analysis revealed that the apparent maximum binding capacity (Qmax) and the dissociation content (Kd) to ERY were as follows: Qmax1 = 45.24 mg/g, Kd1 = 0.028 g/L; Qmax2 = 87.53 mg/g, Kd2 = 0.20 g/L. Using the prepared MIPs as selective adsorbent, the proposed molecularly imprinted solid phase extraction (MISPE) coupled with high performance liquid chromatography (HPLC) was successfully applied to determine ERY residue in pork samples. A linear correlation was obtained over a range of 0.5-50 mg/L (r2 = 0.999 4), and the limit of detection was 0.2 mg/kg (S/N = 3). The spiked recoveries of ERY were 95.2%-104.2% with the relative standard deviations (RSDs) of less than 5%. The proposed method is selective, sensitive and reliable for the analysis of ERY residue in pork samples.

Objective: To develop a quantitative method for simultaneously determining four flavones in Radix Scutellariae, by using one chemical standard substance., Method: The relative correction factors (RCF) of four flavones were determined by HPLC-DAD. Within the linear ranges, the values of RCF at 274 nm of wogonoside, baicalein, and wogonin to baicalin, were 0.7467, 0.5638, 0.4351, respectively. And the contents of baicalin in 27 samples of Scutellaria baicalensis were authentically determined by the external standard method, and the contents of the three other flavones were calculated according to their RCF. The contents of these four flavones in the all samples were determined with the external standard method., Result: The RCF had a good reproducibility (RSD 0.66%-2.83%). No significant differences between the quantitative results by the above two methods were observed., Conclusion: It is a fast, convenient, and accurate method to determine multi-components especially when some authentic standard substances were unavailable. It can be used as a method to control the quality of Radix Scutellariae.