风门对矿井火灾烟气流动特性影响的数值模拟研究*

为研究巷道内风门开启程度对矿井火灾烟气流动特性的影响,使用火灾动力学模拟软件FDS模拟0.5,1.0,1.5,2.0,2.5,3.0 m/s 6种通风风速,以及风门开启1/4,1/2,3/4和全开启4种情况对巷道火灾烟气流动特征参数温度和能见度的影响。结果表明:风速0.5,1.0 m/s 时,风门开启1/4最有利于人员逃生;风速1.5 m/s时,风门开启1/2最有利于人员逃生;风速高于1.5 m/s时,风门关闭影响巷道内风流流动,因此不宜关闭风门;在风门全开启时,随着风速增大,火源上风侧的温度降低、井下能见度升高,烟气的逆退距离缩短,当风速2.5 m/s时各监测点温度最稳定。     

Release flux of mercury from different environmental surfaces in Chongqing, China

An investigation was conducted to estimate mercury emission to the atmosphere from different environmental surfaces and to assess its contribution to the local mercury budget in Chongqing, China. Mercury flux was measured using dynamic flux chamber (DFC) at six soil sites of three different areas (mercury polluted area, farmland and woodland) and four water surfaces from August 2003 to April 2004. The mercury emission fluxes were 3.5 ± 1.2–8.4 ± 2.5 ng m⁻² h⁻¹ for three shaded forest sites, 85.8 ± 32.4 ng m⁻² h⁻¹ for farming field, 12.3 ± 9.8–733.8 ± 255 ng m⁻² h⁻¹ for grassland sites, and 5.9 ± 12.6–618.6 ± 339 ng m⁻² h⁻¹ for water surfaces. Mercury exchange fluxes were generally higher from air/water surfaces than from air/soil surfaces. The mercury negative fluxes were found in tow soil sites at overcast days (mean = −6.4 ± 1.5 ng m⁻² h⁻¹). The diurnal and seasonal variations of mercury flux were observed in all sites. The mercury emission responded positively to the solar radiation, but negatively to the relative humidity. The mercury flux from air/soil surfaces was significantly correlated with soil temperature, which was well described by an Arrhenius-type expression with activation energy of 31.1 kcal mol⁻¹. The annual mercury emission to the atmosphere from land surface is about 1.787 t of mercury in Chongqing.     

北京市大气能见度规律及下降原因

利用历史资料和外场观测数据,对北京市大气能见度的规律进行了分析.结果发现,北京市大气能见度较差的时间占全年的近一半.夏季能见度最好,冬季最差.通常中午能见度最好.高浓度的颗粒物是北京市大气能见度下降的主要原因.局地重污染天气和沙尘暴天气虽然发生几率小,但可以使北京市大气能见度下降得很低.      

公路隧道能见度及其关联影响因子研究

通过对谭裕沟隧道和梧桐山隧道内能见度、机动车流量和构成、主要空气污染物的监测和研究,探讨了隧道内能见度下降的主要原因,结果表明,影响能见度的主要污染物是粒径较小的细粒子。      

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

京津冀区域霾天气特征

汇总京津冀区域内107个地面站的气象资料,利用14时实测的气象要素和天气现象资料对霾日进行判别,统计出各个站点1980~2008年中逐年及各月的霾日数.结果表明,北京、天津、河北霾天气整体变化趋势和波动特征较为相似,且均呈增加趋势,非城区站点平均霾日数明显呈增加趋势,且与市区站点霾日数的差距越来越小.京津冀区域霾日数的月际变化呈明显的双峰特征,即夏季和冬季霾日数较高.空间分布表明,霾日数高值区主要位于北京、天津、保定、石家庄、邯郸和邢台等地.多数站点霾日14时平均风速比非霾日低了1.0m/s以上,14时平均相对湿度则比非霾日高出20%以上.     

我国硫输送和沉降量规律的研究

介绍了我国排放的硫污染物在大气中的输送规律,给出我国各省(区)1992,1993和1995年高架源和低架源平均硫沉降量、总沉降量及其来源省的贡献率。研究结果证明,由于我国疆域辽阔,排放的大气酸性污染物有90%以上沉降在本国大陆地区和领海海域内。在日本和周边国家的沉降量不超过其本国沉降量的10%。      

南京市大气微生物调查及其动态研究

调查了南京市主要功能区大气微生物中常见种类的细菌和霉菌类,研究了细菌和霉菌类的生态分级和变化规律,比较了大气微生物与大气监测指标PM10、SO2、NO2的相关性。通过分析2000年10月至2001年8月6个功能区4个季节的监测结果,得出山西路监测点微生物数量最高,并且该点微生物中是以细菌为优势种,其次是霉菌属的马丁霉菌和耐渗透压霉菌。通过生理生化试验鉴定细菌和霉菌类,得出南京市大气微生物中细菌基本以微球菌属为主,霉菌以青霉属、曲霉属为主。大气微生物数量统计结果表明,南京市主要功能区微生物总量(均值)从高到低的顺序为:山西路(商业区)>中华门(交通区)>瑞金路(居住区)>迈皋桥(工业区)>玄武湖(对照点)>草场门(文教区)。大气化学监测指标PM10、SO2、NO2分析结果也表明大气微生物的数量变化与之呈一定的正相关关系,尤其与PM10关系更为密切。     

基于Landsat TM/ETM+/OLI遥感大数据分析南京市1984—2015年大气能见度变化趋势

对南京市1984—2015年Landsat 4／5／7／8卫星TM／ETM＋／OLI传感器获取的遥感数据，利用ENVI遥感软件的FLAASH大气校正模块，进行了区域大气能见度（ VIS）遥感反演。结果表明，时间跨度达30余年的Landsat卫星遥感数据影像序列反演的VIS呈明显的下降趋势，20世纪80年代数值较高，“差”能见度（＜10 km）的观测率不到6％，21世纪以来VIS下降明显，“差”能见度的观测率为20％～25％。与2010—2015年南京市PM10、PM2．5监测数据进行了对比，在城市空气清洁及污染较轻时，星地监测结果有较好的一致性，但中到重污染天气时FLAASH算法反演VIS偏高，侧重于代表离主城区距离远的偏远乡野山林地区的能见度状况。     

珠三角秋冬季节长时间灰霾污染特性与成因

利用珠三角大气超级站2012年10月与2013年1月能见度、不同粒径颗粒物与BC质量浓度、气溶胶光散射系数、O3、相对湿度等在线监测数据,分析秋冬季节2次持续时间超过10 d的长时间灰霾过程污染特性与成因。结果表明,冬季灰霾过程中气溶胶吸光系数和光散射系数对大气总消光系数的贡献分别为13%和67%;PM2.5、PM1占PM10质量浓度分别为66%和39%;较高的PM2.5与BC日均浓度相关系数(R2=0.88)体现了一次排放对颗粒物质量浓度及能见度的显著影响。秋季灰霾过程中气溶胶吸光系数和光散射系数对大气总消光系数的贡献分别为11%和69%,由BC导致的吸光效应较冬季下降了约20%;PM2.5和PM1占PM10质量浓度比例分别为68%和45%,均高于冬季;O3浓度日最大小时值的平均值接近冬季的2倍;二次来源对PM2.5浓度升高和能见度下降起主导作用。来自不同方向的2种气团在珠三角僵持,大气扩散条件差是导致这2次灰霾过程的重要外在条件,应成为灰霾预报预警的重点关注对象。