京津冀PM2.5时空分布特征及其污染风险因素

为分析京津冀及其周边区域2013年典型污染事件中PM_2.5的时空分布特征及污染风险因素,根据国家城市环境空气质量实时发布数据和京津冀地区地理国情信息监测成果,采用空间数据挖掘方法对PM_2.5污染的热点区域进行了划分;并采用地理探测器定量分析了PM_2.5污染风险因子及其影响程度. 结果表明:在选取的京津冀6个城市中,在PM_2.5污染事件统计上存在保定—廊坊—北京—天津—承德—张家口的污染顺序. PM_2.5污染在空间上呈河南省(山东省)—河北省—北京市(天津市)一线的带状分布特征,在单次污染事件中,城市间的PM_2.5污染存在空间运移关系. 空间热点探测表明,京津冀及其周边区域主要分为5个热点聚集区,其中3个高值区分布在北京市、天津市、河北省和山东省的中部,面积分别为5.31×104、10.26×104、5.04×104 km2. 在8个污染风险因子中,污染企业总数(影响力为0.97,下同)、降水量(0.93)、地形坡度(0.89)对PM_2.5污染的影响显著高于其他风险因子;其他风险因子影响力排序依次为人口数量(0.60)、降水量大于0.1 mm的降水日数(0.57)、地表覆盖类型(0.52)、年均相对湿度(0.51)、年均风速(0.33),但风险因子间相比没有显著性差异. 研究显示,京津冀地区PM_2.5污染的主要因素是污染物排放,其次,气象要素中的年降水量和自然地理环境中的地形坡度也是影响PM_2.5污染特征的重要风险因子.      

云南菊科入侵物种与本地共生物种光合特性比较

为了探求菊科入侵植物的入侵机制,了解菊科入侵植物与非入侵植物光合特性的差异,以云南省包括薇甘菊(Mikania micrantha)、紫茎泽兰(Ageratina adenophora)、飞机草(Chromolaena odorata)、三叶鬼针草(Bidens pilosa)在内的4种菊科入侵物种为研究对象,并以与其共生的菊科外来非入侵物种熊耳草(Ageratum houstonianum)为对照,研究外来入侵物种与非入侵物种叶片特性及气体交换参数等方面的区别. 结果表明:薇甘菊、紫茎泽兰、飞机草和三叶鬼针草的P_nmax(maximum net photosynthetic rate, 最大净光合速率)分别为15.92、18.69、17.15和22.78 μmol/(m2·s),分别比其共生非入侵物种熊耳草的高出21.63%、42.77%、31.02%和73.99%;4种入侵物种的LSP(light saturation point, 光饱和点)和LCP(light compensation point, 光补偿点)也显著高于熊耳草,但其AQY(apparent quantum yield, 表观量子效率)却显著低于该共生种. 4种入侵物种叶片的N_mass(leaf N content per unit mass, 单位质量N含量)和CC_mass(leaf construction cost per unit mass, 单位质量建成成本)均显著高于熊耳草,除飞机草外,其他3种入侵物种的PEUE(photosynthetic energy use efficiency, 光合能量利用效率)和PNUE(photosynthetic nitrogen use efficiency, 光合氮利用效率)均显著高于熊耳草,而飞机草和熊耳草之间差异并不显著. 5种植物叶片N_mass分别与叶片SLA(specific leaf area,比叶面积)、CC_mass呈极显著正相关,与植物P_nmax、叶片P_mass(leaf N content per unit mass, 单位质量P含量)和PEUE呈显著正相关,植物P_nmax与PNUE、PEUE呈极显著正相关,与叶片SLA呈显著正相关. 研究显示,与菊科共生外来非入侵植物相比,较高的光合特性参数、叶片特性指标和能量利用效率指标可能是外来菊科入侵物种成功入侵的原因之一.      

On the use of principal component analysis (PCA) for evaluating interannual vegetation anomalies from SPOT/VEGETATION NDVI temporal series

In this work, we discuss the use of principal component analysis (PCA) for evaluating the vegetation interannual anomalies. The analysis was preformed on a temporal series (1999–2002) of the yearly Maximum Value Composit of SPOT/VEGETATION NDVI acquired for Sicily Island. The PCA was used as a data transform to enhance regions of localized change in multi-temporal data sets. This is a direct result of the high correlation that exists among images for regions that do not change significantly and the relatively low correlation associated with regions that change substantially. Both naturally vegetated areas (forest, shrub-land, herbaceous cover) and agricultural lands have been investigated in order to extract the most prominent natural and/or man-induced alterations affecting vegetation behavior. Our findings suggest that PCA can provide valuable information for environmental management policies involving biodiversity preservation and rational exploitation of natural and agricultural resources.     

The StepOne real-time polymerase chain reaction detection of Salmonella sp., Salmonella enterica ser. typhimurium and enteritidis in milk and meat

The aim of this study was to follow contamination of ready to eat milk and meat products with Salmonella spp. by using the StepOne real-time polymerase chain reaction (PCR). Classical microbiological methods for detection of foodborne bacteria involve the use of pre-enrichment and/or specific enrichment, following isolation of bacteria in solid media and the final confirmation by biochemical and/or serological tests. We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and MicroSEQ® Salmonella spp. Detection Kit for pursuance of the real-time PCR (Applied Biosystems). In samples without incubation we detected strain of Salmonella sp. in 5 out of 25 samples (swabs), as well as in the internal positive control (IPC), which was positive in all samples. This StepOne real-time PCR assay is extremely useful for any laboratory equipped by real-time PCR. It is a fast, reproducible, simple, specific and sensitive way to detect nucleic acids, which could be used in clinical diagnostic tests in the future. Our results indicated that real-time PCR assay developed in this study could sensitively detect Salmonella spp. in ready-to-eat food. This could prevent infection caused by Salmonella, and also could benefit food manufacturing companies by extending their product's shelf-life as well as saving the cost of warehousing their food products while awaiting pathogen testing results.     

Detection of Listeria monocytogenes in ready-to-eat food by Step One real-time polymerase chain reaction

The aim of this study was to follow contamination of ready-to-eat food with Listeria monocytogenes by using the Step One real time polymerase chain reaction (PCR). We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and MicroSEQ® Listeria monocytogenes Detection Kit for the real-time PCR performance. In 30 samples of ready-to-eat milk and meat products without incubation we detected strains of Listeria monocytogenes in five samples (swabs). Internal positive control (IPC) was positive in all samples. Our results indicated that the real-time PCR assay developed in this study could sensitively detect Listeria monocytogenes in ready-to-eat food without incubation.