scholarly journals Meteorological formation mechanism of regional transport in winter heavy air pollution events in the middle Yangtze River area, China

2020 ◽  
Author(s):  
Yongqing Bai ◽  
Tianliang Zhao ◽  
Yue Zhou ◽  
Jie Xiong ◽  
Weiyang Hu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Formation Mechanism ◽  
Air Pollutants ◽  
Yangtze River ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
Regional Transport ◽  
Near Surface ◽  
Orthogonal Function ◽  
Pollution Events

Abstract. Anthropogenic emission, meteorological conditions, and regional transport are the three major factors influencing heavy air pollution in China. The Hunan and Hubei provinces in the middle Yangtze River region border China's main air pollution areas, serving as the hub of regional transport of air pollutants. The meteorological formation mechanism of regional transport of air pollutants on heavy air pollution in the Hunan and Hubei provinces still remain urgent to be addressed in depth. In this study, multivariate empirical orthogonal function (MV-EOF) analysis was performed to objectively select eight typical heavy pollution events in the two provinces that occured in January 2015–2019. Based on the regional surface environment, meteorological network data, atmospheric sounding data, ERA-interim reanalysis data, and a numerical simulation experiment, this study investigated the pattern of regional transport of air pollutants in the two provinces and its mechanism of regional meteorological conditions. The results showed that transporting air pollutants mainly passed through two transport pathways, namely the Nanxiang Basin-Yunmeng Plain pathway and the Dabie Mountain's Hilly Area-Yunmeng Plain pathway, existing anomalous near-surface northerly winds in the two provinces and their upstream area accompanied by southward penetration of a shallow cold layer, all of which jointly provide a dynamic condition for regional air pollutant transport. The weak cold-air mass degenerated as it passed through the Hunan–Hubei Plain, causing warm air to accumulate in the near-surface layer of the downstream area, where winds slowed down and converged, buffering the air pollutant transport and resulting in pollutants accumulation; the near-surface atmosphere of the Hunan and Hubei provinces was a non-stagnant condition (dry intrusion of cold air, anomalous northerly winds, and positive anomalies of boundary-layer height), which is conducive to the horizontal transport of air pollutants. However, the mid-high layers, characterized by temperature inversion and the presence of a warm lid, had a stable stratification, inhibiting the diffusion of air pollutants to the upper layers; there is an obvious longitudinal vertical circulation above the Hunan–Hubei Plain, which results in the sinking and accumulation of air pollutants, thereby promoting rapid accumulation of air pollutants in the Hunan and Hubei provinces. In addition, extended empirical orthogonal function (EEOF) analysis was performed, revealing a quasi-4-d periodic oscillation pattern of air pollutants transport in the Hunan and Hubei provinces, which provides a reference for early prediction of its regional transport. The findings are of practical value in broadening the scientific understanding of the differences in the formation mechanism of heavy atmospheric pollution between the various regions of China and promoting environmental and ecological protection of the middle Yangtze Basin.

scholarly journals Heavy air pollution with a unique “non-stagnant” atmospheric boundary layer in the Yangtze River middle basin aggravated by regional transport of PM<sub>2.5</sub> over China

2020 ◽  
Vol 20 (12) ◽  
pp. 7217-7230 ◽  
Author(s):  
Chao Yu ◽  
Tianliang Zhao ◽  
Yongqing Bai ◽  
Lei Zhang ◽  
Shaofei Kong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Atmospheric Boundary Layer ◽  
Air Pollutants ◽  
Yangtze River ◽  
Temperature Inversion ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
The Yangtze River ◽  
Regional Transport

Abstract. The regional transport of air pollutants, controlled by emission sources and meteorological factors, results in a complex source–receptor relationship of air pollution change. Wuhan, a metropolis in the Yangtze River middle basin (YRMB) of central China, experienced heavy air pollution characterized by hourly PM2.5 concentrations reaching 471.1 µg m−3 in January 2016. To investigate the regional transport of PM2.5 over central eastern China (CEC) and the meteorological impact on wintertime air pollution in the YRMB area, observed meteorological and other relevant environmental data from January 2016 were analyzed. Our analysis presented noteworthy cases of heavy PM2.5 pollution in the YRMB area with unique “non-stagnant” meteorological conditions of strong northerly winds, no temperature inversion, and additional unstable structures in the atmospheric boundary layer. This unique set of conditions differed from the stagnant meteorological conditions characterized by near-surface weak winds, air temperature inversion, and stable structure in the boundary layer that are typically observed in heavy air pollution over most regions in China. The regional transport of PM2.5 over CEC aggravated PM2.5 levels, thus creating heavy air pollution in the YRMB area. This demonstrates a source–receptor relationship between the originating air pollution regions in CEC and the receiving YRMB region. Furthermore, a backward trajectory simulation using a Flexible Particle dispersion (FLEXPART) Weather Research and Forecasting (WRF) model to integrate the air pollutant emission inventory over China was used to explore the patterns of regional transport of PM2.5 governed by the strong northerly winds in the cold air activity of the East Asian winter monsoon season. It was estimated that the regional transport of PM2.5 from non-local air pollutant emissions contributes more than 65 % of the PM2.5 concentrations to the heavy air pollution in the YRMB region during the study period, revealing the importance of the regional transport of air pollutants over China as a causative factor of heavy air pollution over the YRMB area.

scholarly journals Heavy air pollution with the unique “non-stagnant” atmospheric boundary layer in the Yangtze River Middle Basin aggravated by regional transport of PM<sub>2.5</sub> over China

2019 ◽  
Author(s):  
Chao Yu ◽  
Tianliang Zhao ◽  
Yongqing Bai ◽  
Lei Zhang ◽  
Xingna Yu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Air Pollutants ◽  
Yangtze River ◽  
Eastern China ◽  
Temperature Inversion ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
Regional Transport ◽  
Central Eastern

Abstract. Regional transport of air pollutants controlled by both emission sources and meteorological factors results in a complex source-receptor relationship of air pollution change. Wuhan, a metropolis in the Yangtze River Middle Basin (YRMB) of central China experienced heavy air pollution characterized by excessive PM2.5 concentrations reaching 471.1 μg m−3 in January 2016. In order to investigate the regional transport of PM2.5 over China and the meteorological impact on wintertime air pollution in the YRMB area, observational meteorological and other relevant environmental data from January 2016 were analyzed. Our analysis presented the noteworthy cases of heavy PM2.5 pollution in the YRMB area with the unique “non-stagnant” meteorological conditions of strong northerly winds, no temperature inversion and additional unstable structures in the atmospheric boundary layer. This unique set of conditions differed from the stagnant meteorological conditions characterized by near-surface weak winds, air temperature inversion, and stable structure in the boundary layer observed in heavy air pollution over most regions in China. The regional transport of PM2.5 over central-eastern China aggravated PM2.5 levels present in the YRMB area, thus demonstrating the source-receptor relationship between the originating air pollution regions in central-eastern China and the receiving YRMB regions. Furthermore, a backward trajectory simulation using FLEXPART-WRF to integrate the air pollutant emission inventory over China was used to explore the patterns of regional transport of PM2.5 governed by the strong northerly winds in the cold air activity of the East Asian winter monsoon over central-eastern China, which contributes markedly to the heavy PM2.5 pollution in the YRMB area. It was estimated that the regional transport of PM2.5 of non-local air pollutant emissions could contribute more than 65 % of the PM2.5 concentrations to the heavy air pollution in the YRMB region during the study period, revealing the importance of the regional transport of air pollutants over central-eastern China in the formation of heavy air pollution over the YRMB region.

scholarly journals Effects of atmospheric circulations on the interannual variation in PM<sub>2.5</sub> concentrations over the Beijing–Tianjin–Hebei region in 2013–2018

2020 ◽  
Vol 20 (13) ◽  
pp. 7667-7682 ◽  
Author(s):  
Xiaoyan Wang ◽  
Renhe Zhang
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Air Pollutants ◽  
Emission Reduction ◽  
Interannual Variation ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
Chinese Government ◽  
Near Surface ◽  
Bth Region

Abstract. The Chinese government has made many efforts to mitigate fine particulate matter pollution in recent years by taking strict measures on air pollutant reduction, which has generated the nationwide improvements in air quality since 2013. However, under the stringent air pollution controls, how the wintertime PM2.5 concentration (i.e., the mass concentration of atmospheric particles with diameters less than 2.5 µm) varies and how much the meteorological conditions contribute to the interannual variations in PM2.5 concentrations are still unclear, and these very important for the local government to assess the emission reduction of the previous year and adjust mitigation strategies for the next year. The effects of atmospheric circulation on the interannual variation in wintertime PM2.5 concentrations over the Beijing–Tianjin–Hebei (BTH) region in the period of 2013–2018 are evaluated in this study. Generally, the transport of clean and dry air masses and an unstable boundary layer in combination with the effective near-surface horizontal divergence or pumping action at the top of the boundary layer benefits the horizontal or vertical diffusion of surface air pollutants. Instead, the co-occurrence of a stable boundary layer, frequent air stagnation, positive water vapor advection and deep near-surface horizontal convergence exacerbate the wintertime air pollution. Favorable circulation conditions lasting for 2–4 d are beneficial for the diffusion of air pollutants, and 3–7 d of unfavorable circulation events exacerbates the accumulation of air pollutants. The occurrence frequency of favorable circulation events is consistent with the interannual variation in seasonal mean PM2.5 concentrations. There is better diffusion ability in the winters of 2014 and 2017 than in other years. A 59.9 % observed decrease in PM2.5 concentrations in 2017 over the BTH region could be attributed to the improvement in atmospheric diffusion conditions. It is essential to exclude the contribution of meteorological conditions to the variation in interannual air pollutants when making a quantitative evaluation of emission reduction measurements.

scholarly journals The role of meteorological conditions and pollution control strategies in reducing air pollution in Beijing during APEC 2014 and Victory Parade 2015

2017 ◽  
Vol 17 (22) ◽  
pp. 13921-13940 ◽  
Author(s):  
Pengfei Liang ◽  
Tong Zhu ◽  
Yanhua Fang ◽  
Yingruo Li ◽  
Yiqun Han ◽  
...  
Keyword(s):  
Air Pollution ◽  
Pollution Control ◽  
Air Pollutants ◽  
Meteorological Parameters ◽  
Control Strategies ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
Pollutant Concentrations ◽  
Air Pollutant Concentrations

Abstract. To control severe air pollution in China, comprehensive pollution control strategies have been implemented throughout the country in recent years. To evaluate the effectiveness of these strategies, the influence of meteorological conditions on levels of air pollution needs to be determined. Using the intensive air pollution control strategies implemented during the Asia-Pacific Economic Cooperation Forum in 2014 (APEC 2014) and the 2015 China Victory Day Parade (Victory Parade 2015) as examples, we estimated the role of meteorological conditions and pollution control strategies in reducing air pollution levels in Beijing. Atmospheric particulate matter of aerodynamic diameter  ≤ 2.5 µm (PM2.5) samples were collected and gaseous pollutants (SO2, NO, NOx, and O3) were measured online at a site in Peking University (PKU). To determine the influence of meteorological conditions on the levels of air pollution, we first compared the air pollutant concentrations during days with stable meteorological conditions. However, there were few days with stable meteorological conditions during the Victory Parade. As such, we were unable to estimate the level of emission reduction efforts during this period. Finally, a generalized linear regression model (GLM) based only on meteorological parameters was built to predict air pollutant concentrations, which could explain more than 70 % of the variation in air pollutant concentration levels, after incorporating the nonlinear relationships between certain meteorological parameters and the concentrations of air pollutants. Evaluation of the GLM performance revealed that the GLM, even based only on meteorological parameters, could be satisfactory to estimate the contribution of meteorological conditions in reducing air pollution and, hence, the contribution of control strategies in reducing air pollution. Using the GLM, we found that the meteorological conditions and pollution control strategies contributed 30 and 28 % to the reduction of the PM2.5 concentration during APEC and 38 and 25 % during the Victory Parade, respectively, based on the assumption that the concentrations of air pollutants are only determined by meteorological conditions and emission intensities. We also estimated the contribution of meteorological conditions and control strategies in reducing the concentrations of gaseous pollutants and PM2.5 components with the GLMs, revealing the effective control of anthropogenic emissions.

scholarly journals Effects of atmospheric circulations on the interannual variation in PM<sub>2.5</sub> concentrations over the Beijing-Tianjin-Hebei region in 2013–2018

2020 ◽  
Author(s):  
Xiaoyan Wang ◽  
Renhe Zhang
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Air Pollutants ◽  
Emission Reduction ◽  
Interannual Variation ◽  
Meteorological Conditions ◽  
Mitigation Strategies ◽  
Chinese Government ◽  
Near Surface ◽  
Bth Region

Abstract. The Chinese government has made many efforts to mitigate fine particulate matter (PM2.5) pollution in recent years by taking strict measures on air pollutants reduction, which has generated the nationwide improvements in air quality since 2013. However, under the stringent air pollution controls, how PM2.5 concentration varies and how much the meteorological conditions contribute to the interannual variations in PM2.5 concentrations are still unclear, which is very important for the local government to assess the emission reduction of previous year and adjust mitigation strategies of next year. The effects of atmospheric circulation on the interannual variation in wintertime PM2.5 concentrations over the Beijing-Tianjin-Hebei (BTH) region in the period of 2013–2018 are evaluated in this study. Generally, the transport of clean and dry air masses and unstable boundary layer working with the effective near-surface horizontal divergence or pumping action at the top of the boundary layer benefit for the horizontal or vertical diffusion of surface air pollutants. Instead, the co-occurrence of a stable boundary layer, frequent air stagnation, positive water vapor advection and deep near-surface horizontal convergence exacerbate the air pollution. Favorable circulation conditions lasting for 2~4 days are beneficial for the diffusion of air pollutants, and 3~7 days of unfavorable circulation events exacerbate the accumulation of air pollutants. The occurrence frequency of favorable circulation events is consistent with the interannual variation in seasonal mean PM2.5 concentrations. There is better diffusion ability in the winters of 2014 and 2017 than in other years. A 76.5 % of the observed decrease in PM2.5 concentrations in 2017 over the BTH region could be attributed to the improvement in atmospheric diffusion conditions. It is essential to exclude the contribution of meteorological conditions to the variation in interannual air pollutants when making a quantitative evaluation of emission reduction measurements.

scholarly journals Relationship between Air Pollutant Exposure and Gynecologic Cancer Risk

2021 ◽  
Vol 18 (10) ◽  
pp. 5353
Author(s):  
Qiwei Yu ◽  
Liqiang Zhang ◽  
Kun Hou ◽  
Jingwen Li ◽  
Suhong Liu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Cancer Risk ◽  
Air Pollutants ◽  
Gynecological Cancer ◽  
Gynecologic Cancer ◽  
Ambient Air ◽  
Air Pollutant ◽  
Ambient Air Pollution ◽  
Short Term Exposure ◽  
Increased Risk

Exposure to air pollution has been suggested to be associated with an increased risk of women’s health disorders. However, it remains unknown to what extent changes in ambient air pollution affect gynecological cancer. In our case–control study, the logistic regression model was combined with the restricted cubic spline to examine the association of short-term exposure to air pollution with gynecological cancer events using the clinical data of 35,989 women in Beijing from December 2008 to December 2017. We assessed the women’s exposure to air pollutants using the monitor located nearest to each woman’s residence and working places, adjusting for age, occupation, ambient temperature, and ambient humidity. The adjusted odds ratios (ORs) were examined to evaluate gynecologic cancer risk in six time windows (Phase 1–Phase 6) of women’s exposure to air pollutants (PM2.5, CO, O3, and SO2) and the highest ORs were found in Phase 4 (240 days). Then, the higher adjusted ORs were found associated with the increased concentrations of each pollutant (PM2.5, CO, O3, and SO2) in Phase 4. For instance, the adjusted OR of gynecological cancer risk for a 1.0-mg m−3 increase in CO exposures was 1.010 (95% CI: 0.881–1.139) below 0.8 mg m−3, 1.032 (95% CI: 0.871–1.194) at 0.8–1.0 mg m−3, 1.059 (95% CI: 0.973–1.145) at 1.0–1.4 mg m−3, and 1.120 (95% CI: 0.993–1.246) above 1.4 mg m−3. The ORs calculated in different air pollution levels accessed us to identify the nonlinear association between women’s exposure to air pollutants (PM2.5, CO, O3, and SO2) and the gynecological cancer risk. This study supports that the gynecologic risks associated with air pollution should be considered in improved public health preventive measures and policymaking to minimize the dangerous effects of air pollution.

scholarly journals Association between Air Pollution and the Development of Rheumatic Disease: A Systematic Review

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Gavin Sun ◽  
Glen Hazlewood ◽  
Sasha Bernatsky ◽  
Gilaad G. Kaplan ◽  
Bertus Eksteen ◽  
...  
Keyword(s):  
Air Pollution ◽  
Rheumatic Diseases ◽  
Air Pollutants ◽  
Population Sample ◽  
Case Control ◽  
Air Pollutant ◽  
Case Control Studies ◽  
Mesh Terms ◽  
Increased Risk ◽  
American Children

Objective. Environmental risk factors, such as air pollution, have been studied in relation to the risk of development of rheumatic diseases. We performed a systematic literature review to summarize the existing knowledge.Methods. MEDLINE (1946 to September 2016) and EMBASE (1980 to 2016, week 37) databases were searched using MeSH terms and keywords to identify cohort, case-control, and case cross-over studies reporting risk estimates for the development of select rheumatic diseases in relation to exposure of measured air pollutants (n=8). We extracted information on the population sample and study period, method of case and exposure determination, and the estimate of association.Results. There was no consistent evidence of an increased risk for the development of rheumatoid arthritis (RA) with exposure to NO2, SO2, PM2.5, or PM10. Case-control studies in systemic autoimmune rheumatic diseases (SARDs) indicated higher odds of diagnosis with increasing PM2.5exposure, as well as an increased relative risk for juvenile idiopathic arthritis (JIA) in American children <5.5 years of age. There was no association with SARDs and NO2exposure.Conclusion. There is evidence for a possible association between air pollutant exposures and the development of SARDs and JIA, but relationships with other rheumatic diseases are less clear.

scholarly journals Analysis of Temporal Variations of Air Pollutant Concentrations in Ogoni Area, Niger Delta Region, Nigeria

2021 ◽  
pp. 63-73
Author(s):  
B. Yorkor ◽  
T. G. Leton ◽  
J. N. Ugbebor
Keyword(s):  
Air Pollution ◽  
Temporal Variability ◽  
Niger Delta ◽  
Air Pollutants ◽  
Temporal Variations ◽  
Time Of Day ◽  
Air Pollutant ◽  
Pollutant Concentrations ◽  
Hourly Data ◽  
Air Pollutant Concentrations

This study investigated the temporal variations of air pollutant concentrations in Ogoni area, Niger Delta, Nigeria. The study used hourly data measured over 8 hours for 12 months at selected locations within the area. The analyses were based on time series and time variations techniques in Openair packages of R programming software. The variations of air pollutant concentrations by time of day and days of week were simulated. Hours of the day, days of the week and monthly variations were graphically simulated. Variations in the mean concentrations of air pollutants by time were determined at 95 % confidence intervals. Sulphur dioxide (SO2), Nitrogen dioxide (NO2), ground level Ozone (O3) and fine particulate matter (PM2.5) concentrations exceeded permissible standards. Air pollutant concentrations showed increase in January, February, November and December compared to other months. Simulation showed that air pollutants varied significantly by hours-of-the-day and days-of-the-week and months-of-the-year. Analysis of temporal variability revealed that air pollutant concentrations increased during weekdays and decreased during weekends. The temporal variability of air pollutants in Ogoni area showed that anthropogenic activities were the main sources of air pollution in the area, therefore further studies are required to determine air pollutant dispersion pattern and evaluation the potential sources of air pollution in the area.

scholarly journals Associations of Ambient Air Pollutants and Meteorological Factors With COVID-19 Transmission in 31 Chinese Provinces: A Time Series Study

2021 ◽  
Vol 58 ◽  
pp. 004695802110602
Author(s):  
Han Cao ◽  
Bingxiao Li ◽  
Tianlun Gu ◽  
Xiaohui Liu ◽  
Kai Meng ◽  
...  
Keyword(s):  
Air Pollution ◽  
Relative Humidity ◽  
Wind Velocity ◽  
Air Pollutants ◽  
Meteorological Factors ◽  
Meta Analysis ◽  
Ambient Air ◽  
Air Pollutant ◽  
Pollutant Concentrations ◽  
Air Pollutant Concentrations

Evidence regarding the effects of environmental factors on COVID-19 transmission is mixed. We aimed to explore the associations of air pollutants and meteorological factors with COVID-19 confirmed cases during the outbreak period throughout China. The number of COVID-19 confirmed cases, air pollutant concentrations, and meteorological factors in China from January 25 to February 29, 2020, (36 days) were extracted from authoritative electronic databases. The associations were estimated for a single-day lag as well as moving averages lag using generalized additive mixed models. Region-specific analyses and meta-analysis were conducted in 5 selected regions from the north to south of China with diverse air pollution levels and weather conditions and sufficient sample size. Nonlinear concentration–response analyses were performed. An increase of each interquartile range in PM2.5, PM10, SO2, NO2, O3, and CO at lag4 corresponded to 1.40 (1.37–1.43), 1.35 (1.32–1.37), 1.01 (1.00–1.02), 1.08 (1.07–1.10), 1.28 (1.27–1.29), and 1.26 (1.24–1.28) ORs of daily new cases, respectively. For 1°C, 1%, and 1 m/s increase in temperature, relative humidity, and wind velocity, the ORs were 0.97 (0.97–0.98), 0.96 (0.96–0.97), and 0.94 (0.92–0.95), respectively. The estimates of PM2.5, PM10, NO2, and all meteorological factors remained significantly after meta-analysis for the five selected regions. The concentration–response relationships showed that higher concentrations of air pollutants and lower meteorological factors were associated with daily new cases increasing. Higher air pollutant concentrations and lower temperature, relative humidity and wind velocity may favor COVID-19 transmission. Controlling ambient air pollution, especially for PM2.5, PM10, NO2, may be an important component of reducing risk of COVID-19 infection. In addition, as winter months are arriving in China, the meteorological factors may play a negative role in prevention. Therefore, it is significant to implement the public health control measures persistently in case another possible pandemic.

scholarly journals A physical modeling approach for identification of source regions of primary and secondary air pollutants

2006 ◽  
Vol 6 (4) ◽  
pp. 6467-6496 ◽  
Author(s):  
J. C. F. Lo ◽  
A. K. H. Lau ◽  
Z. B. Yuan ◽  
J. C. H. Fung ◽  
F. Chen
Keyword(s):  
Hong Kong ◽  
Air Pollutants ◽  
Power Plants ◽  
Three Dimensional ◽  
Air Pollutant ◽  
Regional Transport ◽  
Meteorological Model ◽  
Secondary Air Pollutants ◽  
Secondary Air ◽  
The Pearl River

Abstract. This paper describes a simple but practical methodology to identify the contribution of primary and secondary air pollutants from the local/regional emission sources to Hong Kong, a highly urbanized city with complex terrain and coastlines. The meteorological model MM5 coupled with a three-dimensional, mutli-particle trajectory model is used to identify salient aspects of regional air pollutant transport characteristics during some typical meteorological conditions over the Pearl River Delta (PRD) region. Several weighting factors are determined for calculating the air mass/pollutant trajectory and are used to evaluate the local and regional contribution of primary pollutants over the PRD to Hong Kong pollution. The relationships between emission inventories, physical paths and chemical transformation rates of the pollutants, and observational measurements are formulated. The local and regional contributions of secondary pollutants are obtained by this conceptual module under different weather scenarios. Our results demonstrate that major pollution sources over Hong Kong come from regional transport. In calm-weather situations, 78% of the respirable suspended particulates (RSP) totals in Hong Kong are contributed by regional transport, and 49% are contributed by the power plants within the PRD. In normal-day situations, 71% of the RSP are contributed by regional transport, and 45% are contributed by the power plants.

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