茶叶铅污染来源的研究进展

根据近年来国内外对茶叶铅污染研究的相关报道,综述了茶叶中铅污染的主要来源。这些来源主要包括:茶园土壤酸化和较高的有机质含量,大气沉降物中的铅和茶叶的加工过程。还根据各种茶叶铅污染来源的特征,有针对性地提出了一些防治措施。     

中国铅污染的调查研究

阐述了中国铅污染的调查结果,包括:历史回顾、群体铅中毒事件、燃油铅污染、燃煤铅污染、铅中毒率统计和防治研究等6个部分。历史回顾从人类对铅污染危害认识的3次飞跃,反映了铅污染由公共卫生问题上升为人类社会问题;中毒事件调查,告诉人们企业的违规排铅,是铅中毒事件的罪魁祸首;燃油污染调查结果表明,汽油无铅化后,燃油大气铅年排放量比从前平均降低了98%左右;燃煤污染的调查结果表明,中国燃煤铅排放量年均增长9.55%,到2010年,中国燃煤铅排放量突破14 000 t,是汽车尾气铅排放量的35倍,且燃烧大气铅排放量与儿童铅中毒率之间存在显著的正相关关系;中毒率的调查结果表明,2003—2007年中国儿童铅中毒率平均为23.61%,比1994—2003年的35.27%有显著降低,但2007年为23.5%,比2006年的17.2%有所反弹;防治研究指出,中国对铅的研究主要是涉及铅毒理和铅污染防治等方面的研究,2006年发表铅文献量接近1 600篇。防治对策是污染源控制和人群监测,发铅与血铅监测同样可靠。     

铅的大气环境及北大园区大气中铅的测定

简述了大气中铅污染的主要来源，铅的毒性及其在人发，血液及尿中的参考值，采和双膜法收集了大气样品，并用阳极溶出伏安法测定北大园区内铅的水平，结果表明，大气中铅主要存在于〈１０μｍ的细粒子中，北大校园内大气中铅的浓度低于国家规定的Ⅱ级地区标准。     

铅同位素在示踪城市环境污染源研究中的应用

在分析铅同位素示踪环境铅污染源理论的基础上,以成都市为例,对成都市城市环境（土壤、大气降尘、主要水系沉积物）铅污染的主要来源进行了研究.结果表明,成都市城市环境污染主要来自于燃煤扬尘和汽车尾气排放.铅同位素示踪理论应用于城市环境污染源的研究,能够取得比较理想的结果.     

汽油无铅化后中国儿童铅中毒现状、污染源及防治对策

汽油无铅化后,我国儿童铅中毒问题仍相当严重,群体铅中毒事件频频发生,铅中毒流行率相对较高且有回升趋势,膳食铅摄入量过高。在各类铅污染源中,燃煤铅排放已成为大气铅污染的重要贡献者,初步估算表明,2001—2005年燃煤大气铅排放总量达4.5万t,铅排放量与铅中毒率之间呈显著相关关系。预防铅中毒应切实加强环境污染的有效控制和敏感人群的定期监测,铅中毒监测亦应采取血铅测定和发铅测定双管齐下的方针。     

铅暴露的易感人群

铅暴露被认为对许多特殊人群有较大的危险性 ,除铅作业工人、汽车司机、交通警察等经常暴露于铅环境的人群外 ,要特别注意下列人群 :(1 )儿童。儿童中许多人有嗜土癖和手 口活动 ,胃肠道对铅的吸收率和滞留率较高 ,密质骨比例比成年人小 ,不能将吸收的铅更多地转移到骨中。这样就有较多的铅滞留在易产生毒性的软组织中。血液、神经和肾脏三大系统最易蒙受铅的毒害。(2 )妊娠妇女及发育中的胎儿。铅可通过母体胎盘转运到胎儿循环系统中 ,对胎儿产生不利的影响 ;在胎儿发育期 ,铅对代谢过程和生理过程最为灵敏 ;妊娠时由于激素平衡发生变更 ,…     

1953—2005年中国燃煤大气铅排放量估算

采用随时间变化的铅排放因子估算了中国1953—2005年燃煤大气铅排放量。在52年间,中国燃煤累计向大气排放19.1万t铅,平均每年以4.02%的速度增加,其中2001—2005年排铅38 688 t,平均增速达9.55%;工业用煤的铅排量占总量的87%,生活用煤铅排量占8%;2006年的燃煤铅排量超过了10 000 t。这表明,燃煤造成的铅污染已成为当前中国面临的重要环境问题。     

土壤及其他背景样品中铅同位素比值的测定方法

为给铅同位素示踪技术在判别土壤、大气、水体和人体中铅与相关重金属污染来源,区别汽车尾气铅污染和工业铅污染等方面的应用提供科学依据。通过大量的对比条件实验,拟出了土壤、煤、汽车尾气和气溶胶样品中铅同位素比值的测定方法。利用这三个流程分别测定了采自杭州茶园的土壤及茶园附近的煤、汽车尾气和气溶胶样品的铅同位素比值,其中207Pb/206Pb的精度(2σ)均优于±0.03%。重复样误差优于±0.05%2。08Pb强度一般均在1V以上,有的高达8 V以上。监控分析流程的国际标准物质NBS981的207Pb/206Pb为0.91449±0.00004。全流程本底铅为10-8数量级。     

铅稳定同位素在环境污染示踪中的应用和进展

从国内外大量研究实例出发,论述了铅同位素示踪在环境污染研究中的应用和进展。包括大气降尘、水系沉积物、土壤—植物体系这三个方面的相关理论以及最新的研究成果,并得出了不同研究对象中铅污染的来源、迁移以及富集的一些规律。     

不同环境蔬菜中铅污染的研究

用原子吸收分光光度计石墨炉法分析了公路附近的蔬菜中铅的含量。结果表明,蔬菜中铅的含量还与其距离公路的远近有关,蔬菜与空气接触程度也有关;不同种类蔬菜中的铅污染有差异。     

丽水市地表水体铅污染的控制对策与成效

通过多点的普监和连续的定点跟踪监测,明确了丽水市地表水体铅污染的基本状况和主要污染源,提出了相应的对策措施,取得了显著的控制成效,为区域水环境治理提供了参考依据.     

PVC塑料流化床气化试验研究

为开发城市生活垃圾低污染流化床气化与旋风燃烧熔融技术，研究了垃圾中广泛存在的PVC塑料在流化床内的气化特性与污染物生成机理。不同温度和过量空气系数下进行了流化床PVC气化试验，分析了不同工况对PVC中Cl转化为HCl的影响。实验结果表明，反应高于600 ℃、过量空气系数大约0.4时，Cl转化为HCl的选择性达到95％以上；气化效率达到22％～25％，气化气热值达到2 000 kJ/m3～2 300 kJ/m3。反应高于700 ℃，PVC流化床气化生烟量明显减少，过量空气系数0.6时，生烟量减少到PVC质量的10％左右。提出的HCl析出与生烟机理较好地解释了试验结果，为城市生活垃圾气化熔融技术提供了相关基础数据与污染物生成及控制方法。     

便携式气相色谱–质谱法现场测定有组织排放废气中VOCs

建立便携式气相色谱-质谱仪现场测定有组织排放废气中VOCs的方法。针对固定污染源有组织废气排放的特点,对升温程序、扫描方式、采样方式、进样体积进行了讨论优化,提出了对高、低浓度废气样品测定的解决方案,分析了气袋本底的干扰和去除方式。用所建方法对TO-14标准气体进行测定,各组分的含量在0.02~1.00μL/L范围内线性关系良好,相关系数均大于0.990,各组分检出限为0.004~0.014μL/L。测定结果的相对标准偏差为2.4%~15.3%(n=6),加标回收率为73.3%~109%。该方法检测时间短,具有良好的精密度和准确度,适用于有组织排放废气中VOCs测定。     

Pilot study: PAH fingerprints of aircraft exhaust in comparison with diesel engine exhaust

In the course of a preliminary investigation the PAH fingerprints from diesel engines were compared with those from aircraft turbines. The goal was to determine whether PAH fingerprints permit to distinguish between the sources of air and road traffic. The results showed that the PAH spectra of both sources do not vary significantly. However, in turbine exhaust gas p-quaterphenyl was found, that is untypical for diesel engines. So this component may be a tracer for PAH pollution from aeroplanes.     

Pilot study: PAH fingerprints of aircraft exhaust in comparison with diesel engine exhaust

In the course of a preliminary investigation the PAH fingerprints from diesel engines were compared with those from aircraft turbines. The goal was to determine whether PAH fingerprints permit to distinguish between the sources of air and road traffic. The results showed that the PAH spectra of both sources do not vary significantly. However, in turbine exhaust gas p-quaterphenyl was found, that is untypical for diesel engines. So this component may be a tracer for PAH pollution from aeroplanes. Received: 7 February 1997 / Revised: 24 September 1997 / Accepted: 27 September 1997     

Determination of particle-associated polycyclic aromatic hydrocarbons in urban air of Beijing by GC/MS.

Particle-associated polycyclic aromatic hydrocarbons (PAHs) collected in urban air of Beijing were studied using a gas chromatograph mass spectrometer (GC/MS). The average concentration of particle-associated PAHs measured in this work was in the range from 28.53 to 362.15 ng/m3, which suggested a serious pollution level of PAHs in Beijing. The results also showed that the concentration of PAHs in the winter was distinctly higher than that in summer and spring. Benzo(a)pyrene (BaP) and benzo(a)pyrene-equivalent carcinogenic power (BaPE) were adopted to evaluate the PAHs pollution state at the sampling site. Through some diagnostic ratios, it can be concluded that traffic exhaust, especially vehicles with diesel engines, and domestic coal-burning heaters might have a prominent contribution to the PAHs concentration.     

Graphene based chemiresistor sensors for the detection of toxic air pollutants: A theoretical overview

The advancements in present world like industrial revolution, transport system, agriculture, food industry, pharmaceutical industry and electricity generation have made our life easy and comfortable in many aspects but they also have deleterious effects on our life. The pollution from industries, household waste, combustion of fossils etc. has introduced many harmful chemicals in air and water which have badly affected the life on our planet. The presence of undesirable gases in air has serious adverse effects on health and quality of life. Therefore, monitoring of these substances becomes important.Graphene based chemiresistor sensor are proved to be promising materials for the detection of toxic air pollutants. This article summarizes the recent progress of Density functional theory (DFT) based studies in the field of graphene based gas sensors. This article discusses the working mechanism of graphene based chemiresistor and also provides the information that how the sensing ability can be enhanced. The information given in the article will help the young researchers in the selection of suitable dopant and nano-clusters for graphene based surfaces to make them more selective and sensitive towards the analytes.     

Lichens biomonitoring as feasible methodology to assess air pollution in natural ecosystems: Combined study of quantitative PAHs analyses and lichen biodiversity in the Pyrenees Mountains

The air quality in the Aragón valley, in the central Pyrenees, has been assessed by evaluation of lichen biodiversity and mapped by elaboration of the Index of Air Purity (IAP) based on observations of the presence and abundance of eight kinds of lichen with different sensitivity to air pollution. The IAP values obtained have been compared with quantitative analytical measures of 16 PAHs in the lichen Evernia prunastri, because this species was associated with a wide range of traffic exposure and levels of urbanization. Analyses of PAHs were carried out by the DSASE method followed by an SPE clean-up step and GC–MS analysis. The concentration of total PAHs found in lichen samples from the Aragón valley ranged from 692 to 6420 ng g⁻¹ and the PAHs profile showed predominance of compounds with three aromatic rings. The influence of the road traffic in the area has been shown because values over the median concentration of PAHs (>1092 ng g⁻¹), percentage of combustion PAHs (>50%), and equivalent toxicity (>169) were found in lichens collected at places exposed to the influence of traffic. The combination of both methods suggests IAP as a general method for evaluating the air pollution referenced to PAHs because it can be correlated with the content of combustion PAHs and poor lichen biodiversity can be partly explained by the air pollution caused by specific PAHs. Figure Map of the air pollution level in the Aragón valley (Pyrenees) based on the Index of Air Purity (IAP) calculation (lichen biodiversity)     

The use of thermogravimetry to analyze a mixed plastic waste stream

The thermogravimetry of a mixed polymer waste stream has been studied and the weight-loss behaviour of this heterogeneous mixture has been compared with results obtained from the weight-loss curves of some individual polymers. The results suggest that the behaviour of the mixture cannot be predicted by the simple additive behaviour of the individual polymers since interactions can occur which influence the degradation weight-loss profiles. The heterogeneous polymeric waste studied was that generated from the shredding of old discarded automobiles. The results of the study indicate that while it is possible to determine what is present in a sample, the relevance of the data to a very heterogeneous waste stream is questionable.     

Evaluation of malodor for automobile air conditioner evaporator by using laboratory-scale test cooling bench

As one of the measures to improve the environment in an automobile, malodor caused by the automobile air-conditioning system evaporator was evaluated and analyzed using laboratory-scale test cooling bench. The odor was simulated with an evaporator test cooling bench equipped with an airflow controller, air temperature and relative humidity controller. To simulate the same odor characteristics that occur from automobiles, one previously used automobile air conditioner evaporator associated with unpleasant odors was selected. The odor was evaluated by trained panels and collected with aluminum polyester bags. Collected samples were analyzed by thermal desorption into a cryotrap and subsequent gas chromatographic separation, followed by simultaneous olfactometry, flame ionization detector and identified by atomic emission detection and mass spectrometry. Compounds such as alcohols, aldehydes, and organic acids were identified as responsible odor-active compounds. Gas chromatography/flame ionization detection/olfactometry combined sensory method with instrumental analysis was very effective as an odor evaluation method in an automobile air-conditioning system evaporator.