大气超细颗粒物观测和扩散模拟研究进展

总结了近年来不同地区对不同环境下大气超细颗粒物的观测和扩散模拟研究进展。大量的观测研究结果表明,大气超细颗粒物的时空分布、组成特征、形成和成长的特性因观测地区的不同而存在很大差异,受气象因素和局部污染源的影响很大;其来源主要包括固定、移动燃烧源的直接排放和大气中颗粒成核现象,前一种来源一般是局部的,而后一种来源则是区域性的。目前,大多数关于大气超细颗粒物扩散的模拟研究都是针对其质量浓度的,对其数浓度扩散的模拟研究主要集中在小范围(机动车排放烟云的研究方面),在城市区域范围上的研究和应用还很少。最后,探讨和展望了大气超细颗粒物今后的主要研究方向和研究中面临的挑战。     

Influence of soil ageing on bioavailability and ecotoxicity of lead carried by process waste metallic ultrafine particles

Ultrafine particulate matters enriched with metals are emitted into the atmosphere by industrial activities and can impact terrestrial and aquatic ecosystems. Thus, this study investigated the environmental effects of process particles from a lead-recycling facility after atmospheric deposition on soils and potential run-off to surface waters. The toxicity of lead-enriched PM for ecosystems was investigated on lettuce and bacteria by (i) germination tests, growth assays, lead transfer to plant tissues determination and (ii) Microtox analysis.The influence of ageing and soil properties on metal transfer and ecotoxicity was studied using three different soils and comparing various aged, spiked or historically long-term polluted soils. Finally, lead availability was assessed by 0.01 M CaCl₂ soil extraction.The results showed that process PM have a toxic effect on lettuce seedling growth and on Vibrio fischeri metabolism. Soil-PM interactions significantly influence PM ecotoxicity and bioavailability; the effect is complex and depends on the duration of ageing. Solubilisation or stabilisation processes with metal speciation changes could be involved. Finally, Microtox and phytotoxicity tests are sensitive and complementary tools for studying process PM ecotoxicity.     

Leaching of zinc from tire wear particles under simulated estuarine conditions

Tire wear particles (TWP) abraded from end-of-life passenger car tires have been added at a concentration of 1 g L⁻¹ to river water, sea water and mixtures thereof in order to examine the chemical controls on the leaching of Zn from the rubber matrix. Results of time-dependent experiments conducted over a period of 5 days were consistent with a diffusion controlled leaching mechanism with rate constants of about 0.04 mg L⁻¹ h^−1/2 in river water and between about 0.02 and 0.03 mg L⁻¹ h^−1/2 in sea water. Additional experiments revealed a reduction in Zn dissolution with both increasing salinity and pH and enhancement of leaching in the presence of fluorescent light compared with dark conditions. In corresponding experiments conducted in the presence of a fixed quantity (0.8 g L⁻¹) of clean, fractionated estuarine sediment, aqueous Zn concentrations were reduced by at least an order of magnitude. Increasing the quantity of sediment resulted in a progressive reduction in Zn concentration until an apparent equilibrium was achieved, with partition coefficients defining the sediment-water distribution of Zn of about 550 mL g⁻¹ and 270 mL g⁻¹ in river water and sea water, respectively. Results are interpreted in terms of the dissolution of ZnO and other residual complexes from the matrix and the subsequent, rapid adsorption of Zn²⁺ ions to coexistent estuarine sediment. The findings of the study are discussed in terms of their implications for the transport, fate and effects of TWP Zn in aquatic environments that are likely to receive urban runoff.     

微波纳米磁粉协同作用处理污泥的研究

将粒径范围在10～20 nm之间的磁粉加入到原污泥中,在微波场中辐射,考察0.5～5 min辐射时间内污泥可生化性能、沉降性能和脱水性能的改善效果.结果表明,在微波和纳米磁粉的协同作用下,污泥快速发生水解,5 min内VSS溶解率达到34.62%,COD溶出率达到13.38%,在显微镜下观察到污泥微生物细胞发生了破裂;...     

新型低气阻高效除尘器的研究与应用

为了提高除尘器对细颗粒物的捕捉效率,制备了一种由蜂窝陶瓷、聚酰胺材质扭线刷和缚尘剂组成的除尘模块。其中填充了聚酰胺扭线刷的蜂窝陶瓷为除尘模块的主体,该主体独有的结构将拦截尘粒的滤料纤维分布在与气流方向垂直的平面上,有利于含尘气体的捕捉。缚尘剂为除尘模块的增强因子,它可以在除尘模块表面形成液膜,用来抑制除尘时的二次扬尘,提高除尘效率。通过对涂覆有缚尘剂的除尘模块的除尘效率的研究表明,含尘气体通过除尘模块,对粒径2μm的颗粒除尘效率最高可达到97.08%,表明了除尘模块去除细颗粒物的潜力;另外,在实验中设定的条件下,系统的压降保持在85 Pa以下。总体而言,该除尘模块在保持较低压降的同时对细颗粒物有较高的去除效率,有应用在工业除尘的潜力。     

Effects of suspended common-scale and nanoscale particles on the survival,growth and reproduction of Daphnia magna

Suspended particles are a natural component of aquatic ecosystems. This study provides a report on the survival, growth and reproduction of common-scale and nanoscale particles of Daphnia magna Straus exposed to five types of particles (i.e. KN (kaolinite), MN (montmorillonite), MNn (nanoscale MN), NP (natural particles), and NPn (nanoscale NP)). The results of the study show that the suspended particles elicited a dose-dependent toxicity in KN, MN and MNn, with the following toxicity pattern: MN > KN > MNn. On the contrary, NP and NPn did not show any harmful effects on the animals. Instead, NP and NPn, especially NPn, contributed to the survivorship of the animals. The animals were able to survive throughout the 21-day period of bioassays, and when the particle concentration reached 600 mg L⁻¹, they produced many neonates without any addition of food. This experimental results also indicated that the nanoscale particles were less toxic than the common-scale ones, both for MN and NP. Moreover, the results of the 21-day period of bioassays indicated that when the organisms were exposed to particles of different size scales, they showed different selection patterns for allocating resources. This may be due to the generation of different assimilation and digestion patterns.     

水石流概化水槽试验相似律的探讨

针对水石流粒粗,粘性小的特点,提出了利用水槽进行分段模拟水石流的设想,首次通过几何率解决难度较大的阻力相似问题,改变以往过度加糙的方式,通过变粒径尺度的方法消除了相模型沙级配不连续相似的问题,较好地实现了固体物质级配相停,达到了泥石流的密度相似和输沙相似,通过水槽概化模型实验实例,对本方法进行了验证。     

西安城北地区秋季PM_(2.5)中的矿尘颗粒污染特征

采用单颗粒气溶胶飞行时间质谱仪(Single Particle Aerosol Mass Spectrometer,SPAMS)对西安市大气矿尘颗粒物进行连续12 d在线分析,共采集到107 425个同时含有正负质谱信息的矿尘颗粒,矿尘颗粒物占PM_(2.5)样本数的8.44%。结果表明,矿尘颗粒物的正离子碎片成分以Na~+、K~+、Al~+、Ca~+、CaO~+、Fe~+为主,同时还含有Pb~+等,负离子碎片成分以NO~-_2和NO~-_3为主,另外还含有HSO~-_4、SiO~-_3、HSiO~-_3、H(NO_3)~-_2等。在西安市大气细颗粒物中,矿尘颗粒物中贡献较大的几类(如含钙、含铁、铁氧颗粒物等)大多是老化的成分。将观测阶段采集到的矿尘颗粒纳入本地污染源谱进行来源分析,其主要来源为扬尘源、工业源、燃煤源和汽车尾气源等。     

北京西北城区春季PM10单颗粒形貌类型及成分特征

主要对北京西北城区2010年度春季大气可吸入颗粒物的理化特征进行分析研究,通过利用高分辨率场发射扫描电镜和图像分析技术研究了区内可吸入颗粒物的微观形貌类型及百分含量特征,利用扫描电镜及能谱分析研究矿物颗粒的元素组成及富集类型。结果表明,在西北城区春季大气PM₁₀中可识别出烟尘集合体、球形颗粒、矿物和其他未知颗粒等4种单颗粒类型,沙尘暴天气对矿物颗粒的数量比例影响较大,同时影响颗粒物粒度分布。矿物颗粒按成分可分为"富Si"、"富Ca"、"富Fe"、"富S"、"富Na"、"富Ti"、"富Al"、"富Cl"和"富Mg"颗粒九大类,沙尘天气与非沙尘天气的矿物颗粒均以"富Si"颗粒、"富Ca"颗粒、"富Fe"颗粒、"富S"颗粒等为主。     

天津市PM2.5中水溶性离子组分特征

2006年8—12月连续采集PM_2.5样品,分析其中水溶性无机离子浓度特征。结果表明,采样期间,天津市PM_2.5日均浓度均不同程度超过美国EPA日均浓度标准(35 μg/m³);SO₄^2-、NO₃^-、NH₄⁺和Cl^-为无机离子的主要成分,占全部无机离子的88.6%;各离子均表现出不同季节变化特征。对NH₄⁺和NO₃^-、SO₄^2-进行相关性分析发现,NH₄⁺和NO₃^-相关性最好,相关系数为0.795。SOR和NOR的平均值分别为0.16和0.23,均为8月最高,表明前体物二次转化夏季最明显。