Gas/particle partitioning of atmospheric PCDD/Fs in a satellite town in Eastern China

Gas/particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in ambient air was investigated in a satellite town in Eastern China from April 2007 to January 2008 comprehending large temperature variations (from 3 to 34 °C, daily average). Molecular weight, molecular structure and ambient temperatures are the three major factors that govern the gas/particle partitioning of atmospheric PCDD/Fs throughout the year. Generally, good agreements were obtained (except for winter) between measured particulate fractions and theoretical estimates of both the Junge–Pankow adsorption model and Harner Bidleman absorption model using different sets of subcooled liquid vapor pressure and octanol–air partition coefficient (K_oa), respectively. Models utilizing estimates, derived from gas chromatographic retention indices (GC-RIs), are more accurate than that of entropy-based. Moreover, during winter, the K_oa-based model using the GC-RIs approach performs better on lower chlorinated PCDD/Fs than that of -based. Furthermore, possible sources of mismatch between measured and predicted values in winter (3–7 °C) were discussed. Gas adsorption artifact was demonstrated to be of minor importance for the phenomena observed. On the other hand, large deviations of slopes (m_r) and intercepts (b_r) in logK_p vs. plots from theoretical values are observed in the literature data and these are found to be linearly correlated with ambient temperatures (P<0.001) in this study. This indicates that the non-equilibrium partitioning of PCDD/Fs in winter may be significantly influenced by the colder temperatures that may have slowed down the exchange between gaseous and particulate fractions.     

Indoor and outdoor PM mass and number concentrations at schools in the Athens area

Simultaneous indoor and outdoor PM₁₀ and PM_2.5 concentration measurements were conducted in seven primary schools in the Athens area. Both gravimetric samplers and continuous monitors were used. Filters were subsequently analyzed for anion species. Moreover ultrafine particles number concentration was monitored continuously indoors and outdoors. Mean 8-hr PM₁₀ concentration was measured equal to 229 ± 182 μg/m³ indoors and 166 ± 133 μg/m³ outdoors. The respective PM_2.5 concentrations were 82 ± 56 μg/m³ indoors and 56 ± 26 μg/m³ outdoors. Ultrafine particles 8-h mean number concentration was measured equal to 24,000 ± 17,900 particles/cm³ indoors and 32,000 ± 14,200 particles/cm³ outdoors. PM₁₀ outdoor concentrations exhibited a greater spatial variability than the corresponding PM_2.5 ones. I/O ratios were close or above 1.00 for PM₁₀ and PM_2.5 and smaller than 1.00 for ultrafine particles. Very high I/O ratios were observed when intense activities took place. The initial results of the chemical analysis showed that accounts for the 6.6 ± 3.5% of the PM₁₀ and for the 3.1 ± 1.4%.The corresponding results for PM_2.5 are 12.0 ± 7.7% for and 3.1 ± 1.9% for . PM_2.5 indoor concentrations were highly correlated with outdoor ones and the regression line had the largest slope and a very low intercept, indicative of no indoor sources of fine particulate . The results of the statistical analysis of indoor and outdoor concentration data support the use of as a proper surrogate for indoor PM of outdoor origin.     

The role of periodic boundary forcing in plankton pattern formation

We consider one and two-dimensional minimal models in plankton dynamics. The influence of oscillating boundary forcing functions as agents for triggering pattern formation is discussed. In particular it is found that in these conditions population waves arise for one dimensional models, while for two dimensional models, different amplitudes and frequencies in the boundary forcing generate definite patterns, mimicking the boundary term. This happens even though the model we investigate is very simple. The emergence of these features is an interesting metaphor for the fundamental biological problem of how pattern formation processes may be inevitable in natural heterogeneous ecosystems.     

空间分辨率与精度协同改进的卫星AOD产品降尺度模型

针对现有卫星气溶胶光学厚度(AOD)产品空间分辨率和精度往往难以满足大气污染精细治理实际需求,提出了一种耦合偏差校正的统计降尺度改进模型(SDBC).该模型基于“空间尺度不变性假设”引入相关驱动因子的额外空间信息实现AOD降尺度,并在此基础上通过偏差校正进一步提升降尺度产品的精度.以1km分辨率MAIAC AOD产品为例,在北京、大湾区、台湾岛3个典型地区开展模型验证.结果表明:(1)DEM、NDVI、人口数量和土地覆盖是影响AOD变化的细节因子,在SDBC空间降尺度过程中引入可将AOD产品的空间分辨率有效提升至500m,且降尺度产品验证R2最高可达0.88;(2)顾及卫星观测几何、质量标识、大气水蒸气柱、气溶胶模式等因子的偏差校正则可进一步提升降尺度AOD产品的精度,3个地区的验证R2均在0.85以上,最高可达0.93;(3)信息熵评估结果显示SDBC模型生成的500m AOD产品提高了原始MAIAC AOD产品的空间信息量.在保留了公里级产品AOD的空间分布格局的基础上,SDBC产品也增强了细节和纹理特征、改善了边界现象和马赛克效应.研究结果证实SDBC模型能有效协同改进现有卫星A...     

郑州市 PM2．5和 PM10质量浓度变化特征分析

根据郑州市2013年PM2．5和PM10颗粒物连续自动监测数据,对郑州市各国控站点的PM2．5和PM10的达标情况、变化趋势等进行探讨分析。结果表明：2013年郑州市PM10和PM2．5的年均质量浓度均超过了新标准规定的年均值二级标准限值。 PM10和PM2．5月均值峰值出现在1月和10月,谷值出现在8月,各月PM2．5的超标天数都大于PM10。PM10和PM2．5冬季的日均值浓度明显高于其他季节,呈双峰型,夜晚浓度整体高于白天;PM2．5春、夏、秋三季日变化呈单峰型,PM10夏季和秋季呈单峰型,春季呈双峰型。 PM2．5和PM10日均值有着非常显著的线性相关关系,PM2．5和PM10浓度的比值（p）10月最高。     

机动车排放颗粒物成分谱对比研究

对深圳、无锡、济南和美国EPA建立的机动车排放颗粒物成分谱进行对比研究,建立的成分谱中各组分含量存在较大差别原因为使用了不同的采样方法。     

青岛市区春夏季大气能见度与颗粒物的关系

利用青岛市灰霾综合观测站2012年3月2日-2012年6月7日期间的监测数据,分析了青岛市区大气能见度与不同粒径颗粒物质量浓度的日变化特征,比较了各级别大气能见度下不同粒径颗粒物质量浓度及所占比例的相关性,研究了相对湿度对大气能见度和颗粒物质量浓度相关性的影响.结果表明,监测时段大气能见度与颗粒物质量浓度呈现较好的负相关,每天大气能见度最低值出现在早晨07:00--09:00;剔除相对湿度高于90％的前提下,PM2.5是影响大气能见度的主要因子,随着其在PM1o中所占比例上升,大气能见度级别不断下降,相关系数为-0.84;不同相对湿度区间下,PM2.5对大气能见度的影响最明显,其中,相对湿度为60％ ～ 70％,大气能见度与颗粒物质量浓度之间的相关性最好.     

南京市冬季大气颗粒态汞的分布特征

采集了南京市2012年冬季4个功能区的PM2．5、PM10、TSP样品,对不同粒径大气颗粒物中的颗粒态汞测试。结果表明,南京冬季大气颗粒物TSP中汞的质量浓度为49．26 pg/m3～257．14 pg/m3,平均质量浓度为161．27 pg/m3;PM10中汞的质量浓度为44．82 pg/m3～228．29 pg/m3,平均质量浓度为147．38 pg/m3;PM2．5中汞的质量浓度为35．98 pg/m3～178．58 pg/m3,平均质量浓度为104．10 pg/m3。不同功能区大气颗粒态汞质量浓度的分布趋势为：交通综合区＞旅游区＞住宿综合区＞商业区。大气颗粒态汞60％以上存在于可吸入肺的PM2．5中,细颗粒物富集汞的能力比粗颗粒物强。     

我国居住建筑室内PM_(2.5)研究现状及进展

分析了我国居住建筑室内PM_(2.5)污染水平,总结了现阶段PM_(2.5)的研究方法,主要包括理论分析法、数值模拟法和实验测试法。指出室外源是室内PM_(2.5)的主要污染来源,而室内烟草烟雾、烹饪及人员活动也会严重影响室内PM_(2.5)浓度。针对目前研究中存在的问题,提出了标定典型建筑在不同影响因素下的I/O比范围、研究家具和家电的颗粒物释放状况、加强农村室内外空气颗粒物污染调查等建议。     

长江经济带PM_(2.5)时空特征及影响因素研究

大气细颗粒物(PM_(2.5))因其对空气环境质量乃至人类健康的巨大危害而逐渐引起学者们的关注。本文以我国综合实力最强、战略支撑作用最为突出的区域之一——长江经济带为研究对象,基于城市级空气质量监测数据,运用地理学时空分析与GIS可视化方法探索并呈现了2015年长江经济带PM_(2.5)的时空分布特征及其演变规律;在此基础上,结合空间回归模型考察了PM_(2.5)浓度与区域城市发展之间的内在关系。结果表明,就空间特征而言,长江中下游地区PM_(2.5)污染较长江上游地区更为严重,长江北岸地区比长江南岸地区更为严重;PM_(2.5)高浓度集聚地带主要位于鄂皖苏大部分地区,与空气质量较佳的云南及其周边地区呈"对角"分布状态。长江经济带内城市间PM_(2.5)浓度存在着显著的正向空间自相关,且自相关性随距离增大而不断减弱,其门槛尺度约为900 km;在这一范围内,PM_(2.5)空间集聚效应较为明显。就时间特征而言,冬季PM_(2.5)浓度相对较高,春秋两季次之,夏季空气质量最好;各地区浓度分布在年初相对离散,后有所趋同。此外,PM_(2.5)与其他类型的大气污染物(如SO2、NO2、O3)浓度两两之间均存在着显著的正相关性,暗示大气污染物从原发污染演变为二次污染,形成恶性循环。空间回归分析结果表明,PM_(2.5)污染随经济发展水平的提高呈现先上升后下降的趋势,在一定程度上支持了"环境库兹涅兹曲线"假说;且人口密度、公共交通运输强度均在不同程度上导致长江经济带PM_(2.5)浓度的升高。最后,从区域性联防联控、不同类型大气污染物协同治理、促进经济发展方式转型等方面为长江经济带的大气环境治理提出切实可行的政策建议。