Spatial variability of sydney air quality by cumulative semivariogram

This paper establishes that an isotropic spatial correlation function in the form of a modified Bessel function of the second kind, first order, can be used to model the spatial variability of a pollution concentration field over a sufficiently long period of time in which the variability due to meteorological factors has been smoothed out. The corresponding cumulative semivariogram is derived and fitted by nonlinear least-squares to monthly averaged ozone data at 18 monitoring stations of the Sydney region. The good fit of the model indicates that the Sydney airshed has homogeneous and isotropic subregions whose radius of influence is about 17 km. The Bessel function form of the spatial correlation has a physical meaning as it is derived from the diffusion equation; hence, it is expected that the model can be used, in general, to represent the spatial variability of a smoothed homogeneous and isotropic concentration field.     

Perinatal hepatic infarction in twin–twin transfusion

We report a case of a twin pregnancy which was complicated by a twin–twin transfusion in which the recipient twin was noted to have an intra-abdominal echogenic mass. This twin died at two days of age of hepatic infarction. The donor twin was healthy at birth, at thirty weeks' gestation, and did not have any subsequent problems. Fetal intra-abdominal echogenicity may be a marker of hepatic infarction. Copyright © 2002 John Wiley & Sons, Ltd.     

A rapid and quantitative mass spectrometry method for determining the concentration of acylcarnitines and aminoacids in amniotic fluid

We describe a quantitative, rapid, sensitive and reproducible tandem mass spectrometry (MSMS) method for the one-step detection of aminoacid (AAs) and acylcarnitine (ACs) concentrations in amniotic fluid. This technology is quicker and more sensitive than other methods used to date since it is possible to determine very low AA and AC concentrations in samples simultaneously in a single run. The high degree of automation allows a large number of pregnancies to be screened for metabolic defects in a very short time. Copyright © 2001 John Wiley & Sons, Ltd.     

Critical Reconsideration of Phase Space Embedding and Local Non-Parametric Prediction of Ozone Time Series

Phase space prediction is a feature selection method which triesto exploit non-linear dynamics of an underlying system. We describe and offer a critical reconsideration of this approach,discuss questions of whether non-linear methods are justified by the data, and apply them to ozone time series from single locations. Our main objectives are to obtain air quality forecasts in order to provide public health warnings and to provide an insight into the dynamics of the underlying system.Interestingly, comparable linear data sets (surrogates)have very similar structure and give similar predictionaccuracy to that of the ozone data. In this instance theredoes not appear to be any advantage to applying the phasespace approach to univariate time series.     

搅拌棒吸附萃取-气相色谱-质谱联用测定海水中邻苯二甲酸酯

为了测定海水中痕量邻苯二甲酸酯,构建并优化了搅拌棒吸附萃取-气相色谱-质谱联用方法.选取邻苯二甲酸二甲酯、邻苯二甲酸二乙酯、邻苯二甲酸二丁酯、邻苯二甲酸丁基苄基酯、邻苯二甲酸二(2-乙基己基)酯和邻苯二甲酸二辛酯这6种邻苯二甲酸酯作为研究对象,优化了萃取时间和解析时间等5种因素,通过回收率和相对标准偏差等对SBSE-GC-MS方法进行验证.结果表明,最佳萃取时间为2 h,最佳甲醇添加量为10%,最佳氯化钠添加量为5%,最佳解析时间为50 min,最佳解析溶剂为甲醇∶乙腈=4∶1(体积比).6种邻苯二甲酸酯的峰面积和质量浓度线性对应关系良好,相关性系数均大于0.997,检出限在0.25~174.42 ng·L-1之间,不同质量浓度的回收率均在56.97%~124.22%之间,相对标准偏差在0.41%~14.39%之间.在建立方法的基础上,测定了胶州湾主要河流入海口的样品,结果表明所有采样点均检出邻苯二甲酸酯,邻苯二甲酸二乙酯检出率为100%,质量浓度较大的污染物为邻苯二甲酸二丁酯、邻苯二甲酸丁基苄基酯、邻苯二甲酸二(2-乙基己基)酯和邻苯二甲酸二辛酯.     

上海大气总悬浮颗粒物中金属的可溶性特征

大气颗粒物中金属的可溶性对于评估金属的生物可利用性和环境迁移性具有重要意义.采集上海大气总悬浮颗粒物(TSP)样品,利用高分辨率电感耦合等离子体质谱,测定经微循环淋溶提取的金属水、酸(p H=2)可溶含量,并计算水、酸溶解度.结果表明,大气TSP中金属的溶出是一个快速过程,仅需几分钟就达到溶解度最大值.Co、Cr和Cd的可溶含量较低,V、Ni、Cu处于中间,Fe、Al、Zn、Mn和Mg较高.结合大气后向轨迹分析,金属可溶含量受到气团来源的显著影响.多种金属的水、酸溶解度差异性较大,Fe水溶解度最小仅为2.0%,其次为Al、Cr、V、Pb、Co、Ni、Cu、Cd、Mn、Mg和Zn.金属溶解度随溶剂p H值的减小而增大.元素本身性质是影响金属溶解度的内在原因,且金属的离子势与水溶解度呈一定的负相关性.     

2008~2012年上海黑碳浓度变化特征分析

采用上海市城市环境气象中心2008~2012年黑碳质量浓度小时平均资料,分析了上海市区黑碳质量浓度变化规律.结果表明,2008~2012年间上海黑碳平均质量浓度呈下降趋势,各年黑碳平均质量浓度从(4 045.3±3 375.4)ng·m-3降至(2 766.2±2 078.9)ng·m-3,观测期间的逐年变化率分别为2.3%、-6.5%、-18.7%和-12.1%.与其它大城市相比,黑碳平均质量浓度为中等偏低水平.从年平均变化看,11和12月的5年平均质量浓度最高,分别为5 426.6 ng·m-3和5 365.3ng·m-3,其次为1、6和10月,分别为4 402.5、3 763.3和3 412.7 ng·m-3.工作日和休息日的5年平均日变化均呈明显双峰结构,两峰分别出现在北京时间07:00~10:00和18:00~22:00,工作日第一峰高于第二峰,休息日则相反.5年间,工作日黑碳平均质量浓度较休息日高9%.此外,根据有效观测数据,通过回归整理,给出了一个5年平均黑碳质量浓度日变化的逐时经验函数,以方便估计和预测黑碳浓度水平.     

不同功能区表层土中全氟化合物污染指纹及其来源解析

为探究区域功能对其表层土中全氟化合物(perfluorinated compounds,PFCs)污染指纹与含量水平的影响,采用固相萃取分离富集、高效液相色谱-质谱联用与源解析相结合的方法,分析了深圳市公园、居民小区、十字路口、工厂周边4个功能区和城市背景共76份表层土中14种PFCs的含量.结果表明,深圳市表层土总PFCs(ΣPFCs)含量受区域功能影响显著,呈工厂周边(P<0.001)>>十字路口(P<0.01)>>居民小区(P<0.05)>>公园>城市背景的分布.其中工厂周边、居民小区、公园表层土中PFCs呈中链(P<0.05)>>长链>短链的分布,而十字路口则呈中链≈短链(P<0.05)>>长链的分布.同时,以全氟辛烷磺酸、全氟辛酸、全氟十三酸为主要标志物的3个主成分可以解释深圳表层土超过81%的ΣPFCs,十字路口以及电镀、油漆厂周边表层土呈现出较清晰的PFCs污染指纹.