[Emission Characteristics of the Catering Industry in Beijing].

The emissions of the catering industry are important sources of air pollution in megacities in China. A total of 41 restaurants in Beijing were selected as the sampling sites to evaluate the contribution of the catering industry to megacity air pollution. The original emissions load of cooking fume, particulate matter, and non-methane hydrocarbon (NMHC) were studied via field tests for different types of restaurants. The results showed that the cooking fume, particulate matter, and NMHCs generated from the kitchen were 1.93, 6.6, and 10.9 mg·m-3, respectively. An evaluation method based on working days was developed. Considering the total number of restaurants in Beijing, the original emission loads of 2019 were calculated. The cooking fume, particulate matter, and NMHC emissions were 5512, 18849, and 6169 t, respectively. The Pearson numbers of the cooking fume emission and particular matter emission from Sichuan and Hunan cuisine, Roast Duck, Grill and Barbecue, and Chinese Home-Style cuisine were all above 0.6, which indicated a high level of correlation between the cooking fume emission and particular matter emission. Notably, the Pearson numbers of Sichuan and Hunan cuisine and Roast Duck were both higher than 0.8, which indicates a strong correlation between the cooking fume emission and particular matter emission.

[Pollution Characteristics of Cooking Fumes, Particulates, and Non-methane Hydrocarbons in the Exhaust of Typical Beijing Restaurants].

To understand the atmospheric pollution emission concentration and overall emission level of the Beijing catering industry, and thus provide a basis for the targeted formulation of pollution control measures for the catering industry, this study selected typical catering enterprises in Beijing to research. Combined with the use of stoves during the on-site measurement and testing period, the emission concentrations of cooking fumes, particulates, and non-methane hydrocarbons (NMHC), and the relationship between them in different types of catering enterprises, were analyzed, and the emission of atmospheric pollutants in the Beijing catering industry was estimated. The results showed that the average concentrations of cooking fumes, particulates, and NMHC of typical catering enterprises were (2.91±5.52), (9.25±10.02), and (12.72±11.38) mg·m-3, respectively. These all exceed the Beijing local emission standards. Of the typical catering enterprises, roast duck and barbecue had higher particulate matter and NMHC emissions, which easily exceeded the emission standard. Roast duck and barbecue are therefore the governance focus of the catering industry. The ratio of particulates to cooking fumes in roast duck, barbecue, and cooking catering enterprises ranged from 6.21 to 43.08, 5.03 to 19.07, and 0.75 to 7.55, respectively. The emission concentrations of particles are much larger than those of cooking fumes from charcoal grill and fruit-roasted duck. Pearson correlation coefficient analysis showed that the concentrations of particulates and cooking fumes in catering enterprises were strongly correlated, and the concentrations of particulates and NMHC were weakly correlated. The study estimates roughly that the emissions of cooking fumes, particulates, and NMHC were 2492, 6127, and 9436 tons, respectively, from the catering industry in Beijing in 2014.

[Emission Characteristics of Wind Erosion Dust from Topsoil of Urban Roadside-Tree Pool].

This study characterized the wind erosion dust emissions from topsoil of urban roadside-tree pool. The study area is the Xicheng District of Beijing and uses GIS to obtain the spatial distribution of various road mileages. A full bore investigation method was carried out to survey tree pool in the Zhanlanlu Subdistrict to obtain the activity level of tree pool in the Xicheng district. The portable in situ wind erosion laboratory (PI-SWERL) was used to determine the emission factors of PM2.5 from the wind erosion dust from tree pool and to estimate the PM2.5 emission inventory of tree pool in the Xicheng District in 2016. The results showed that:①The annual emission factors per unit area of PM2.5 from tree pool of freeways' frontage roads, major roads, minor roads, and alleys are 47.9, 7.9, 14.9, and 29.9 g·(m2·a)-1, respectively. The reduction rate of PM2.5 emission factors from tree pool by precipitation was about 30.3% in 2016. ②The annual emission factors per unit mileage of PM2.5 from the tree pool of freeways' frontage roads, major roads, minor roads, branch roads, and alleys are 2.57, 2.33, 4.04, 7.31, and 5.44 kg·(km·a)-1, respectively, and the factors for branch roads are 1.3, 1.8, 2.8, and 3.1 times as much as those for alleys, minor roads, freeways' frontage roads, and major roads, respectively. Taking the emission factor for minor roads as an example, the winter emission factor is 1.3, 7.3, and 8.7 times greater than that in the spring, summer, and autumn, respectively. ③PM2.5 emissions from the tree pool in the Xicheng District of Beijing are 1.60 t·a-1, and the uncertainty range of the emission inventory is -143%~184%. The emissions in winter are 0.68 t·a-1, which are 1.1, 1.42, and 5.1 times greater than that in the spring, summer, and fall, respectively. The emission values for freeways' frontage roads, major roads, minor roads, collectors, and alleys account for 5.6%, 8.7%, 23.2%, 4.1%, and 58.4% of the total emissions, respectively. It is recommended that the urban roadside-tree pool be covered to reduce wind erosion dust emissions with materials that do not affect the growth of trees as soon as possible.

[Atmospheric Pollutant Emission Characteristics from the Cooking Process of Traditional Beijing Roast Duck].

As one of the characteristics of traditional food in Beijing, there is a significant difference between roast duck and other foods in the cooking process, in that fruit trees are used as fuel in the former. However, system research about the emission characteristics of this food source has not been done domestically. In order to grasp such food source emission characteristics and provide technical basis for pollution control, we selected the representative roast duck restaurant in Beijing and studied the emission characteristics of atmospheric pollutants in the cooking process of roast duck. The results showed that the emission concentrations of cooking fumes, particulate matter, volatile organic compounds (VOCs), and aldehyde and ketone compounds were (0.74±0.45), (15.32±7.93), (7.60±3.41), and (1.22±0.59) mg·m-3, respectively. The emission concentration of particulate matter was much higher than that of cooking fumes. The VOC component composition was very complex, containing alkanes, alkenes, aromatic hydrocarbons, and oxygen VOCs, such as aldehydes, ketones, alcohols, ester compounds, and halogenated hydrocarbons, with the highest concentrations of 3-methylfuran, ethanol, and methyl acetate. The main components of aldehyde and ketone compounds were acetaldehyde, formaldehyde, and acrolein, of which C1-C3 compounds were 72.27%.

[Pollution Characteristics of NH4+,NO3-,SO42- in PM2.5and Their Precursor Gases During 2015 in an Urban Area of Beijing].

Simultaneous measurements of precursor gases NH3,NO,NO2,SO2 and the main water-soluble ions in PM2.5 such as sulphate (SO42-),nitrate (NO3-) and ammonium (NH4+) (collectively called SNA)were carried out in the urban area of Beijing during 2015-01 to 2015-12,which obtained 325 groups of samples. PTFE membrane filters were used to collect particulate NH4+, NO3- and SO42-, followed by the online instruments to collect precursor gases. The pollution characteristics of the precursor gases and SNA were analyzed and their correlation was studied. The mean concentrations of NH3, NO, NO2, SO2, NH4+,NO3- and SO42- were 21.5, 17.7, 54.3, 14.2, 8.1, 13.5 and 12.7 µg·m-3 respectively during the period of monitoring, and SNA accounted for 43.4% of PM2.5. The concentrations of SO2,NOx and SNA declined compared to 2014. The concentrations of NO,NO2 and SO2 were highest in winter and lowest in summer. The concentration of NH3 was higher in summer and lower in autumn; The concentration and the percentage of NH4+ were stable during the four seasons,both the concentrations and the percentage of NO3- were lowest in summer. The concentrations of SO42- was highest in winter and the percentage was lowest in summer. The ratio of ([NO3-]+2[SO42-]) and NH4+ was 0.97 during the whole year, showing that anions mainly existed in the form of NO3- and SO42-. In summer, the ratio of[NO3-]+2[SO42-] and[NH4+] was slightly higher than 1.0, which was the reason why NO3- was bound to Ca2+, Mg2+ and Na+besides NH4+. With the increase of pollution, the mass concentration of precursor gases and SNA increased dramatically, among which NOx increased most rapidly, and SO2 decreased from severe pollution to serious pollution. The contribution rate of NH4+ was maintained at a relatively stable level. SO42- had a higher contribution when the pollution level was lower, whereas the concentration of NO3- was higher than others and contributed most to PM2.5 in heavy pollution. Heterogeneous transformation on the surface of particulate matter played a more important role in the formation of SO42- and NO3-. The correlations between NO3-, NO2 and NO,NH4+ and NH3,SO42- and SO2 were significant at the confidence level of 0.01. SO42- had negative correlation with SO2, and NO3- had positive correlation with NO2. Compared with NH3, the NH4+ concentration was more obviously affected by acid gases NO2, SO2.

[Comparison Test Between On-line Monitoring of Water-soluble Ions and Filter-based Manual Methods for PM2.5].

Concentrations of water-soluble ions were measured in Beijing during 2014 for comparison of URG online monitoring systems and filter-based manual methods. The differences of four main ions components in spring, summer, autumn and winter were compared. The total concentrations of eight ions measured by URG online were higher than those of filter-based manual method. There was no significant differences among the annual concentrations of Cl-,NO3-,Mg2+ and Ca2+ obtained by the two methods, while the concentrations of SO42-,NH4+,Na+,K+ from online were higher than those from filter. NO3-,SO42-,Cl- had good correlations in autumn and winter, and NH4+ only had better fitting performance in winter.

[Concentration Characteristics of PM2.5 in Beijing During Two Red Alert Periods].

Variations of PM2.5 concentrations and effects of pollution control measures during two red alert periods in 2015 in Beijing were analyzed based on atmospheric pollutant monitoring data. The results showed that during the first red alert, the highest hourly-averaged PM2.5 concentration occurred at 19:00 on 9th December with a value of 282 µg·m-3 and the highest hourly PM2.5 concentration appeared at Yongledian station which is near the southeast border of Beijing, with the peak concentration of 496 µg·m-3. During the second red alert, the highest hourly-averaged concentration of PM2.5 occurred at 20:00 on 22th with a value of 421 µg·m-3. The highest hourly PM2.5 concentration was monitored at Liulihe station which is near the southwest border of Beijing, with the peak concentration of 831 µg·m-3. During the duration period of both red alerts, the concentrations at the southern stations were higher than those at downtown stations and the PM2.5 concentrations at northern stations were found to be the smallest. The difference between these two red alerts was that during the second red alert, the PM2.5 concentrations in southern Beijing were significantly higher than those in the northern area, while the magnitude of this south-to-north gradient was much smaller during the first one. During the second red alert, up to 93% of Beijing area showed an average PM2.5 concentration of above 150 µg·m-3, which was much larger than that in the first one. The meteorological conditions during the two red alerts were both not conducive to the spread of pollutants. Formation of secondary pollutants and regional pollutant transport existed as well. Though the stagnant weather conditions were in favor of the development of severe pollution, large regional-wide pollutant emission was the main reason for these two heavy air pollutions in Beijing. PM2.5 concentrations were decreased by 20%-25% after the implementation of emergency response measures, which showed the significance of emission reduction in air pollution control.

Metal artifact reduction using virtual monochromatic images for patients with pedicle screws implants on CT.

PURPOSE: To evaluate the effect of spectral CT for metal artifact reduction in patients with pedicle screw. METHODS: 45 patients with 119 pairs of pedicle screws underwent spectral CT examination. One set of conventional (140 kVp) polychromatic image and nine sets of virtual monochromatic images (60-140 keV) were obtained. The standard deviation (SD) of CT number in 12 locations around the implant and 1 on homogenous fat was measured to generate artifact index (AI). Objective assessment including AI, CT number and SD value was performed with independent t test and paired sample t test. Two radiologists independently reviewed the image quality, and Wilcoxon signed-rank test and kappa analysis were used for the subjective scores of image quality. RESULTS: The artifact index (AI) of all the regions decreased as keV increased. AIs of 100-140 keV were lower than that of 140 kVp images. At 120 keV there was no significant difference in CT numbers of psoas major muscle and vertebral canal between pedicle screw level and pedicle level, but a significant difference in SD value was determined between the two levels. The subjective scores at 100-140 keV were higher than the images at 140 kVp, and the highest subjective score of two observers and excellent interobserver agreement were found at 120 keV (κ = 0.889). CONCLUSIONS: Virtual monochromatic images at high-energy levels have a well-concordant effect of removing metal artifacts, and 120 keV monochromatic images provided an accurate CT number and good subjective score.

[Characterization of Water-soluble Ions in PM2.5 of Beijing During 2014 APEC].

The mass concentration of PM2.5 associated with its online and off-line water-soluble ions were obtained during 2014- 10- 2014-11. Secondary inorganic species NO3⁻, SO4²â» and NH4⁺ were the major components of PM2.5 during different observation periods. The total concentration of NO3⁻, SO4²â» and NH4⁺ was (26.8 ± 22.5) µg · m⁻³, which contributed (41.7 ± 8.5)% to PM2.5. The concentration of NO3⁻ was higher than those of others and contributed most to PM2.5. The ions of NO3⁻, SO4²â» NH4⁺ and Cl⁻ all showed three different periods during 2014 Beijing APEC, besides the different meteorological condition, the cumulative effect caused by local emissions and regional pollution could also not be ignored. Although the characteristics of water-soluble ions was different during different observation periods, there was no obvious acidification of PM2.5 in Beijing at the end of autumn and beginning of winter.