Spatiotemporal Dynamics of Hand-Foot-Mouth Disease and Its Relationship with Meteorological Factors in Jiangsu Province,China

Hand, foot and mouth disease (HFMD) is an important public health issue in mainland China, including Jiangsu Province. The main purpose of this study was to depict the epidemiological characteristics of HFMD and evaluate the effects of meteorological variables on its dynamics via spatiotemporal analytic methods, which is essential for formulating scientific and effective prevention and control strategies and measures. In total, 497,910 cases of HFMD occurred in the 2009-2013 period, with an average annual incidence of 126.3 per 100,000 in Jiangsu. Out of these, 87.7% were under 5 years old with a male-to-female incidence ratio of 1.4. The dominant pathogens of the laboratory-confirmed cases were EV71 and CoxA16, accounting for 44.8% and 30.6% of all cases, respectively. Two incidence peaks were observed in each year, the higher occurring between April and June, the lower between November and December. The incidence ranged between 16.8 and 233.5 per 100,000 at the county level. The incidence in the South of the province was generally higher than that in the northern regions. The most likely spatiotemporal cluster detected by space–time scan analysis occurred in May-June of 2012 in the southern region. Average temperature and rainfall were positively correlated with HFMD incidence, while the number of days with rainfall ≥ 0.1mm, low temperature, high temperature and hours of sunshine were negatively related. Particularly, relative humidity had no relationship. In conclusion, the prevalence of HFMD in Jiangsu Province has an obvious feature of seasonality. The etiological composition changed dynamically and might be a latent driving force for the temporal variation of the incidence of HFMD. A moderately warm environment promotes the transmission of the HFMD viruses, while particularly cold and hot climate conditions restrain their transmission.     

南昌市空气PM2.5和PM10的时空动态及其影响因素

PM_2.5和PM₁₀已成为我国大部分城市空气的首要污染物.本文通过分析南昌市2013—2015年的空气PM_2.5和PM₁₀质量浓度、气象因素、交通流量的监测数据,探讨了空气颗粒物污染的时空动态规律以及气象、交通对颗粒物浓度变化的影响.结果表明: 2013、2014、2015年,南昌市PM_2.5浓度(70.92 μg·m^-3＞53.70 μg·m^-3＞43.65 μg·m^-3)、PM₁₀浓度(119.72 μg·m^-3＞86.11 μg·m^-3＞73.32 μg·m^-3)逐年降低,并呈现出夏季低(PM_2.5和PM₁₀平均浓度分别为36.74、69.20 μg·m^-3)、冬季高(PM_2.5和PM₁₀平均浓度分别为74.29、111.64 μg·m^-3)的季节动态和由城市中心向郊区递减的城乡梯度变化; PM_2.5/PM₁₀值(0.595＞0.584＞0.557)逐年降低,并且表现出城市中心高、城市边缘低的空间分布格局;PM_2.5、PM₁₀浓度受到多种气象因素的影响,与气压、温度、相对湿度、风速、降水量、日照时数显著相关,各种气象因子对PM_2.5、PM₁₀浓度的影响存在差异;车流量会显著提高周边PM_2.5浓度,但对PM₁₀浓度影响不明显.     

奥运期间北京PM2.5、NOX、CO的动态特征及影响因素

为了成功举办第29届奥运会,确保北京奥运期间空气质量良好,采取交通管制和工厂停工等临时减排措施改善北京空气环境,希望通过这些措施使大气污染物排放量大幅度降低。在奥运前的综合治理措施中,已经对北京市的烟尘和粉尘排放控制起到了明显效果。在奥运期间更是执行了严格的燃煤污染控制和工业污染控制措施。奥运期间19家重点排污企业和4家燃煤电厂,采取压缩产量、调整运行方式、加强污染设施运行管理等措施,在确保达标基础上,减排30%。并从2008年7月1日起执行世界上最严格的燃煤锅炉排放标准限值。为控制工业污染,150多家重污染企业停产减产限产。这些举措使得奥运期间烟尘和粉尘的排放量大大减少,对PM2.5、NOX、CO的浓度下降起重要作用。此外,奥运期间城区工地停止土石方工程和混凝土浇注工程,对减少施工扬尘、建筑扬尘有明显效果。机关单位、商场、居民实行了错峰上下班措施和公交出行等绿色出行方式,进一步减少了PM2.5、NOX、CO的来源和积累。利用北京城市系统生态研究站的空气环境质量监测数据,对奥运期间北京可吸入颗粒物(PM2.5)、氮氧化物(NOX)、一氧化碳(CO)的日平均浓度的动态特征及其气象因素的关系进行了分析。结果表明:北京奥运期间PM2.5、NOX、CO在生态中心观测点与教学植物园观测点的平均浓度分别为0.060和0.070、0.065mg/m3和0.03、0.65和1.10mg/m3,显著低于奥运后PM2.5、NOX、CO日平均浓度。奥运后PM2.5日平均浓度与奥运期间比较,生态中心站与教学植物园站分别升高3.3%与58.8%,NOX日平均浓度与奥运期间比较2个站分别升高76.9%和56.7%,CO日平均浓度与奥运期间比较2个站分别升高56.5%和163%。奥运期间PM2.5、NOX、CO质量浓度的日变化都呈双峰现象,一个峰出现在7:00—10:00之间,另一个峰出现在18:00—23:00之间,这一特征与通常的北京空气污染物日变化过程一致,污染物浓度日变化双峰现象,虽与气象条件有关,但汽车尾气排放也是一个重要影响因素。主要是由于上班、上学、交通运输的高峰期,车流量大,尾气排放量也大,从而可能对形成上午与夜间的两个PM2.5、NOX、CO浓度高峰起了重要作用。奥运期间污染物除了生态中心监测点的PM2.5小时平均浓度与小时平均温度、风速有显著相关性,与其他气象因素并无相关性。研究表明奥运期间实施的临时空气环境污染控制措施有明显的效果。     

Deposition Velocity of PM2.5 in the Winter and Spring above Deciduous and Coniferous Forests in Beijing,China

To estimate the deposition effect of PM2.5 (particle matter with aerodynamic diameter <2.5 µm) in forests in northern China, we used the gradient method to measure the deposition velocity of PM2.5 during the winter and spring above a deciduous forest in Olympic Forest Park and above a coniferous forest in Jiufeng National Forest Park. Six aerosol samplers were placed on two towers at each site at heights of 9, 12 and 15 m above the ground surface. The sample filters were exchanged every four hours at 6∶00 AM, 10∶00 AM, 2∶00 PM, 6∶00 PM, 10∶00 PM, and 2∶00 AM. The daytime and nighttime deposition velocities in Jiufeng Park and Olympic Park were compared in this study. The February deposition velocities in Jiufeng Park were 1.2±1.3 and 0.7±0.7 cm s⁻¹ during the day and night, respectively. The May deposition velocities in Olympic Park were 0.9±0.8 and 0.4±0.5 cm s⁻¹ during the day and night, respectively. The May deposition velocities in Jiufeng Park were 1.1±1.2 and 0.6±0.5 cm s⁻¹ during the day and night, respectively. The deposition velocities above Jiufeng National Forest Park were higher than those above Olympic Forest Park. The measured values were smaller than the simulated values obtained by the Ruijgrok et al. (1997) and Wesely et al. (1985) models. However, the reproducibility of the Ruijgrok et al. (1997) model was better than that of the Wesely et al. (1985) model. The Hicks et al. (1977) model was used to analyze additional forest parameters to calculate the PM2.5 deposition, which could better reflect the role of the forest in PM2.5 deposition.     

北京海淀区绿色空间PM2.5滞尘服务模拟

绿色空间能够有效吸附空气中的颗粒悬浮物,具有极其重要的PM_2.5滞尘作用.本研究基于植被的PM_2.5滞尘机理,提出了绿色空间的滞尘服务量化方法,并对北京市海淀区绿色空间的PM_2.5单日累积滞尘量,以及不同景观类型冬季、夏季和年滞尘总量进行了空间量化和对比研究.结果表明:海淀区绿色空间冬季的滞尘服务频率和最大单日滞尘量均低于夏季.全年来看,海淀区西部山林景观平均滞尘服务值最高;北部平原区由零散的林地斑块和农田斑块构成的田园景观年滞尘服务总量则最大;而南部城区除几个零星的公园绿地斑块外,大部分区域的滞尘服务是全区的最低水平.PM_2.5滞尘服务模型能够快速定量化绿色空间的滞尘量及其空间分布,对城市绿化建设及PM_2.5大气污染治理具有重要作用.     

云南松茸产区出菇及其气象因子分析

在云南松茸产区楚雄州、保山市、迪庆州各设置一个固定样方监测点,观察和监测松茸出菇情况,并在样方内设置自动气象观测仪监测和记录气象因子及其变化。通过监测数据发现三个监测点的出菇开始时间和出菇高峰存在差异。其中迪庆州叶日监测点的出菇时间早且相对集中,呈现1个集中爆发式的出菇高峰 而保山市海棠和楚雄州芹菜塘两个监测点的情况基本一致,即出菇时间相对较晚但周期长,有3个出菇小高峰。松茸子实体的菌盖、菌柄和高度与生长天数各自存在一定的非线性函数关系。通过对比分析三个研究点的气象因子差异,及其对出菇和子实体生长的影响发现：三点间出菇前和出菇日的温度基本一致,高温缩短子实体的存活时间,土壤温度可能是影响出菇的关键因素。     

Spatiotemporal Dynamics of Scrub Typhus Transmission in Mainland China, 2006-2014

BackgroundScrub typhus is endemic in the Asia-Pacific region including China, and the number of reported cases has increased dramatically in the past decade. However, the spatial-temporal dynamics and the potential risk factors in transmission of scrub typhus in mainland China have yet to be characterized.ObjectiveThis study aims to explore the spatiotemporal dynamics of reported scrub typhus cases in mainland China between January 2006 and December 2014, to detect the location of high risk spatiotemporal clusters of scrub typhus cases, and identify the potential risk factors affecting the re-emergence of the disease.MethodMonthly cases of scrub typhus reported at the county level between 2006 and 2014 were obtained from the Chinese Center for Diseases Control and Prevention. Time-series analyses, spatiotemporal cluster analyses, and spatial scan statistics were used to explore the characteristics of the scrub typhus incidence. To explore the association between scrub typhus incidence and environmental variables panel Poisson regression analysis was conducted.ResultsDuring the time period between 2006 and 2014 a total of 54,558 scrub typhus cases were reported in mainland China, which grew exponentially. The majority of cases were reported each year between July and November, with peak incidence during October every year. The spatiotemporal dynamics of scrub typhus varied over the study period with high-risk clusters identified in southwest, southern, and middle-eastern part of China. Scrub typhus incidence was positively correlated with the percentage of shrub and meteorological variables including temperature and precipitation.ConclusionsThe results of this study demonstrate areas in China that could be targeted with public health interventions to mitigate the growing threat of scrub typhus in the country.     

北京西山典型城市森林内PM_(2.5)动态变化规律

城市森林内PM2.5浓度的状况可以直接反映城市森林对PM2.5的净化效果,也是居民休闲游憩关心的森林环境问题。选择北京西山3种典型的游憩型城市森林,通过对林内PM2.5浓度一年四季昼夜24h内变化的同步观测,分析了不同类型城市森林内PM2.5浓度的季节变化、日变化以及影响因素,结果表明:(1)北京西山3种游憩林内PM2.5浓度多数时候远低于城区对照值,在春、夏、秋三季都达到了国家城市化地区的标准,甚至在春季、秋季还达到了国家一类地区的标准。(2)城市森林在不同季节对PM2.5的净化效果存在差异,林内PM2.5浓度总体上呈现冬季夏季秋季春季的规律。(3)林内PM2.5浓度在一天24h内有很大变化波动,夜间浓度总体上高于白天,日变化曲线近似呈"双峰双谷"型,两个高峰出现在夜晚和早上,两个低谷出现在凌晨和中午前后。一年四季白天低谷出现时间有所不同,春季15:00左右、夏季13:00—17:00、秋季13:00—15:00、冬季9:00—11:00。(4)PM2.5在不同类型游憩林内的变化趋势和浓度值存在一定差异。郁闭度较大的侧柏林夜间PM2.5浓度总体上高于其它两种林型,其高峰和低谷出现时间延迟,高峰值大,高峰期持续时间长,且这种规律在秋季表现得更明显。(5)基于上述研究认为,北京西山城市森林为居民在PM2.5污染比较突出的都市背景下提供了一个相对清洁、健康的森林游憩环境,春季、夏季、秋季全天以及冬季9:00—11:00均是森林中PM2.5状况健康而适宜外出游憩的时段。     

西南地区水稻水分亏缺率时空变化特征及其影响因素

基于西南及周边地区1960—2013年气象观测资料,分析了近54年西南地区水稻生长季水分亏缺率时空变化特征,探讨了环流异常、地理环境与水分亏缺率时空变化的关系。结果表明:在空间格局上,由于受气候条件和地理环境影响,东部丘陵区水分亏缺相对较多,云贵高原水分供给相对充足,且水分亏缺区和盈余区分别呈现出“一带两中心”的分布特征;在变化趋势上,近54年西南地区水稻水分亏缺呈现“整体变干、局部变湿”的空间格局,“甘孜—钦州”一线以南地区水分亏缺率呈现增大趋势,“甘孜—钦州”一线以北地区水分亏缺率呈现“增大—减小相间”的分布格局;在影响因素上,NAO、ENSO与西南地区水稻水分亏缺率变化具有相关性。在NAO正相位时,除广西丘陵区沿海地带部分站点水分亏缺率呈下降趋势外,整个地区干旱化程度加剧;在厄尔尼诺年,西南地区水分亏缺率存在地域分异,横断山区、四川盆地和云贵高原水分亏缺率呈上升趋势,东部丘陵区水分亏缺率则呈下降趋势。全球变暖背景下,西南地区水稻水分亏缺率逐年增加,对灌溉蓄水依赖明显,增大了区域农业脆弱性。     

1982-2012年中国植被覆盖时空变化特征

利用GIMMS NDVI、MODIS NDVI和气象数据,辅以趋势分析、分段回归以及相关分析等方法,分析了1982—2012年我国植被NDVI时空变化特征及其驱动因素。结果表明:(1)近30年我国植被NDVI呈缓慢增加趋势,增速为0.2%/10a;植被覆盖变化阶段性特征明显:即1982—1997年和1997—2012年植被覆盖均呈显著增加趋势,增速分别为1.2%/10a和0.6%/10a,均通过显著水平0.05的检验。(2)空间上,我国陕北黄土高原、西藏中西部以及新疆准格尔盆地等地区植被NDVI呈显著增加趋势;而东北地区的大、小兴安岭和长白山、新疆北部的天山和阿尔泰山以及黄河源和秦巴山区等地区植被NDVI呈显著下降趋势,其中东北地区和新疆北部山区下降尤为显著,说明近年来我国中高纬度山区植被活动呈下降趋势。(3)不同区域植被对气温和降水的响应存在差异,我国北方地区植被对气温具有较长的响应持续时间;而除云南外,南方地区植被对降水的响应时间存在1—3个月的响应时间,且随着滞后时间的延长,相关性逐渐增大。(4)我国植被覆盖增加是气候变化和人类活动共同驱动的结果,尤其是1999年之后人类活动影响逐渐加强。而我国东北地区和新疆北部山区植被覆盖的下降可能是由于该区降水减少所致,东南沿海地区植被退化则受城市化影响显著。     

The Spatiotemporal Expansion of Human Rabies and Its Probable Explanation in Mainland China, 2004-2013

Background

Human rabies is a significant public health concern in mainland China. However, the neglect of rabies expansion and scarce analyses of the dynamics have made the spatiotemporal spread pattern of human rabies and its determinants being poorly understood.

Methods

We collected geographic locations and timeline of reported human rabies cases, rabies sequences and socioeconomic variables for the years 2004-2013, and integrated multidisciplinary approaches, including epidemiological characterization, hotspots identification, risk factors analysis and phylogeographic inference, to explore the spread pattern of human rabies in mainland China during the last decade.

Results

The results show that human rabies distribution and hotspots were expanding from southeastern regions to north or west regions, which could be associated with the evolution of the virus, especially the clade I-G. A Panel Poisson Regression analysis reveals that human rabies incidences had significant correlation with the education level, GDP per capita, temperature at one-month lag and canine rabies outbreak at two-month lag.

Conclusions

The reduction in the overall human rabies incidence was accompanied by a westward and northward expansion of the circulating region in mainland China. Higher risk of human rabies was associated with lower level of education and economic status. New clades of rabies, especial Clade I-G, played an important role in recent spread. Our findings provide valuable information for rabies control and prevention in the future.     

Study of PM10, PM2.5, and PM1 levels in during dust storms and local air pollution events in urban and rural sites in Tehran

The aim of this study is to survey the PM₁₀, PM_2.5, and PM₁ concentrations in rural and urban areas in Tehran province during cold, warm and dust storm days from December 22, 2016 to June 5, 2017 using Grimm Model aerosol spectrometer. During the study period, daily PM₁₀, PM_2.5, and PM₁ concentrations ranged from 27.2 to 244.96, 8.4 to 77.9, and 6.5 to 56.8 μg/m³ in urban sites, and 22.8 to 286.4, 6 to 41.1, and 2.1 to 20.2 μg/m³ in rural parts, respectively. Particularly, both daily WHO limits for outdoor PM₁₀ (50.0 μg/m³) and PM_2.5 (25.0 μg/m³) exceeded in 95% and 83% of the outdoor measurements in winter and 82% and 58% in total sampled days in urban site, respectively. The 24-h average PM₁₀ and PM_2.5 concentrations also exceeded by 59% and 18% in winter and by 36% and 14% of all sampling days in rural site, respectively. During the dust storm, the 24-h average PM₁₀, PM_2.5, and PM₁ concentrations were, respectively 4.7, 2, and 1.96 times higher than those in urban site and 2, 1.7, and 1.3 times more than those in rural site in all sampled days.     

Identifying the spatial effects and driving factors of urban PM2.5 pollution in China

Exploring exactly where air pollution comes from, and identifying the key factors that influence it, can provide a scientific basis for the rational formulation and effective implementation of air pollution policies in China. Based on the data from 2001 to 2012 covering PM_2.5 concentrations in 285 Chinese cities, we use dynamic spatial panel models to empirically analyze the key driving factors of this air pollution. Results show that China’s urban smog demonstrates both obvious global spatial autocorrelation and local spatial agglomeration. There is a significant inverted “U-shaped” curve between economic development level and air pollution, and most cities are in the phase in which pollution is increasing in conjunction with improvements to the economy. Due to a rapid increase in population in built up areas, a high-proportion of secondary industry, a coal-dominated energy structure and increasing traffic intensity, China’s smog problem is becoming more and more serious. FDI probably will not play a future role in mitigating the air pollution. Central heating in winter in northern China further aggravates local smog to a certain extent. Because China’s haze pollution presents path-dependent characteristics and spatial spillover effects in the time dimension and in the space dimension respectively, so smog alleviation policies should be implemented based both on the strategies of maximizing effort and regional joint prevention and control.     

Longitudinal Relationship between Personal CO and Personal PM2.5 among Women Cooking with Woodfired Cookstoves in Guatemala

Household air pollution (HAP) due to solid fuel use is a major public health threat in low-income countries. Most health effects are thought to be related to exposure to the fine particulate matter (PM) component of HAP, but it is currently impractical to measure personal exposure to PM in large studies. Carbon monoxide (CO) has been shown in cross-sectional analyses to be a reliable surrogate for particles<2.5 µm in diameter (PM_2.5) in kitchens where wood-burning cookfires are a dominant source, but it is unknown whether a similar PM_2.5-CO relationship exists for personal exposures longitudinally. We repeatedly measured (216 measures, 116 women) 24-hour personal PM_2.5 (median [IQR] = 0.11 [0.05, 0.21] mg/m³) and CO (median [IQR] = 1.18 [0.50, 2.37] mg/m³) among women cooking over open woodfires or chimney woodstoves in Guatemala. Pollution measures were natural-log transformed for analyses. In linear mixed effects models with random subject intercepts, we found that personal CO explained 78% of between-subject variance in personal PM_2.5. We did not see a difference in slope by stove type. This work provides evidence that in settings where there is a dominant source of biomass combustion, repeated measures of personal CO can be used as a reliable surrogate for an individual''s PM_2.5 exposure. This finding has important implications for the feasibility of reliably estimating long-term (months to years) PM_2.5 exposure in large-scale epidemiological and intervention studies of HAP.     

公园绿地不同景观空间PM2.5分布特征及其影响因素研究

研究选取城市公园中6个由不同景观要素构成的空间,通过监测不同空间内PM2.5浓度、空气温度、相对湿度及风速风向,分析不同空间景观要素组成与PM2.5浓度之间的关系,探讨不同空间气象因子变化与PM2.5浓度的相关性。研究结论如下,1）不同景观要素构成的空间中PM2.5浓度存在显著差异（P< 0.05）。2）PM2.5浓度与绿量（D）呈显著负相关（R=－0.966）, 当113.57 m2相似文献   

Clean air actions in China,PM2.5 exposure,and household medical expenditures: A quasi-experimental study

BackgroundExposure to air pollution, a leading contributor to the global burden of disease, can cause economic losses. Driven by clean air policies, the air quality in China, one of the most polluted countries, has improved rapidly since 2013. This has enabled a unique, quasi-experiment to assess the economic impact of air pollution empirically.Methods and findingsUsing a series of nation-scale longitudinal surveys in 2011, 2013, and 2015, we first examined the questionnaire-based medical expenditure changes before and after the policy intervention for air pollution. Using a state-of-the-art estimator of the historical concentration of particulate matters with diameter less than 2.5 μm (particulate matter (PM)_2.5), we further quantified the association between household medical expenditure and PM_2.5 using mixed-effect models of the repeated measurements from 26,511 households in 126 cities. Regression models suggest a robust linear association between reduced PM_2.5 and saved medical expenditures, since the association did not vary significantly across models with different covariate adjustments, subregions, or subpopulations. Each 10 μg/m³ reduction in PM_2.5 was associated with a saving of 251.6 (95% CI: 30.8, 472.3; p-value = 0.026) Yuan in per capita annual medical expenditure. However, due to limitations in data quality (e.g., self-reported expenditures), and imperfect control for unmeasured confounders or impact from concurrent healthcare reform in China, the causality underlying our findings should be further confirmed or refuted.ConclusionIn this study, we observed that compared with the PM_2.5 reduction in 2013, the PM_2.5 reduction in 2017 was associated with a saving of 552 (95% CI: 68, 1036) Yuan / (person × year), or approximately 736 billion Yuan (equivalent to 111 billion US dollar) per year nationally, which is equivalent to approximately 1% of the national gross domestic product of China.

In this observational study, Tao Xue and colleagues explore associations between medical expenses and changes to clean air policies in China since 2013.     

Particulate matter,PM 10 & PM 2.5 levels,and airborne mutagenicity in Chiang Mai,Thailand

Daily levels of particulate matter (PM) in the ambient air (PM 2.5 and PM 10) were measured in a northern city of Thailand (Chiang Mai) from March 1998 to October 1999. Twenty-four-hour air particulate matter samples were collected each day with Airmetric Minivol portable air samplers. Monthly averages of PM 2.5 from four stations in Chiang Mai varied from 15.39 to 138.31microg/m(3) and 27.29 to 173.40 microg/m(3) for PM 10. The PM 2.5 annual average was 58.48 mg/m(3) and PM 10, 86.38 microg/m(3). Daily PM 2.5 (24h values) during the winter months in Chiang Mai frequently exceeded 200-300 microg/m(3). The maximum concentrations of PM 2.5 (24h average) in Chiang Mai air from December 1998 to April 1999 were 2.8-, 3.5-, 4.2-, 6.5- and 3.2-fold higher than the US Environmental Protection Agency (US EPA), PM 2.5, 24h standard of 65 microg/m(3). From May to October, the mean 24h levels of PM 2.5 and PM 10 were at acceptable levels. The data shows that during the winter season (December to March), levels of PM 2.5 and PM 10 in the Chiang Mai atmosphere are very high, and there may be significant health implications associated with these high concentrations. During the summer season, the fine particles were generally within the acceptable levels. To our knowledge, these are the first measurements of PM 2.5 to be reported for the city of Chiang Mai and they indicate considerable ambient fine particle exposures to the Chiang Mai population. In addition, dichloromethane extracts of airborne particulate matter PM 2.5 or PM 10 collected in the months of winter in the city of Chiang Mai were mutagenic to Salmonella typhimurium strain TA100 without metabolic activation. The mutagenicity appeared to track particle concentrations and increased in the presence of S9 mix.     

南昌市中心城区绿地景观对PM2.5的影响

随着我国城市化工业化的快速发展,大气环境质量问题越来越受到重视,PM_2.5作为重要的大气污染物,已经引起了公众的普遍关注.城市绿地作为一种半自然的地表景观能在一定程度上影响PM_2.5的浓度与分布,目前的研究主要集中在微观尺度上,在景观尺度上的研究还不多见.本研究采用土地利用回归模型进行监测点加密,基于普通克里格插值法实现PM_2.5浓度的空间分布高精度模拟.然后与通过遥感解译的城市绿地进行耦合,定量分析了城市绿地景观特征、质量等对PM_2.5浓度的影响.结果表明:研究区PM_2.5浓度由市中心向周边不断递减;绿地类型对PM_2.5浓度影响显著;绿地斑块形状对PM_2.5浓度没有显著影响;绿地斑块的面积、质量与PM_2.5浓度呈显著负相关.研究区绿地景观对PM_2.5消减作用距离小于100 m.在消减作用距离内,距离绿地斑块越近,PM_2.5浓度越低.其中,附属绿地和公园绿地对PM_2.5浓度的消减作用距离大于其他绿地类型.     

Microbial community structure in PM2.5 affected by burning fireworks during the 2019 Spring Festival in Guilin,a touristic city in South China

Setting off fireworks during the Spring Festival are a popular traditional custom and recreational activity in China. Intensity of firecracker burning can quickly deteriorate air quality. Airborne bacteria are also important constituents of atmospheric particulate matter and contain many pathogens. However, few studies have reported variations in the bacterial community structure in PM_2.5 during firecracker burning. In this study, PM_2.5 samples were collected at four different sites in the city of Guilin during Spring Festival from February 4 to 8, 2019 and a high-throughput sequencing technology was used to investigate the variations of bacterial diversity and community structure in PM_2.5. The results revealed that Proteobacteria was the predominant bacterial phylum comprising 94.3% of the total sequences, followed by Firmicutes, Actinobacteria, Bacteroidetes, and Deinococcus-Thermus. At the genus level, the top five abundant genera accounted for 81.8% of the total sequences. The proportions of major genera (Cupriavidus, Sphingobium, Brevundimonas, Sphingomonas, and Pseudomonas) were apparently affected by firecracker burning. In particular, the relative abundance of Brevundimonas genus increased dramatically from 3.2 to 60.1% at the Huaqiaonongchang (HQ) sampling site during intense firework burning, while those of other major genera and potential pathogens detected including Pseudomonas, Acinetobacter, and Serratia decreased. In addition, compared with the normal condition, the number of operational taxonomic units and the diversity and richness of microorganisms in PM_2.5 samples decreased apparently. Pearson correlation results also revealed that they were negatively correlated with the NO₂, SO₂, and PM_2.5 concentrations.