成都市夏冬季大气胺颗粒物的单颗粒质谱研究

基于单颗粒气溶胶质谱（SPAMS）对成都市夏冬两季大气胺颗粒进行了综合观测,结合ART-2a算法及人工合并,2个季节大气中的胺颗粒都可分为7类,各类颗粒贡献的季节差异明显,燃烧源颗粒（如EC）在夏季贡献较大,而老化的有机碳颗粒（OCa）贡献在冬季显著升高.两季节平均质谱差减进一步证明夏、冬季分别以燃烧源和老化的胺颗粒为主.因高温分解,夏季胺颗粒占比在正午出现明显的低值,而下午的燃烧活动（如生物质燃烧）对该占比提升作用明显;冬季胺颗粒占比在白天显著高于夜间.随污染加重,胺颗粒数在夏冬两季均快速增加,其中夏季EC颗粒升高最为明显,污染最重时贡献可达47%;冬季升高最明显的是老化程度更高的OCa颗粒,当PM_2.5浓度达到200μg/m³以上时,其贡献比例可达37%.因此,由于污染源和气候条件的差异,成都市大气胺颗粒形成机制和理化特征季节差异巨大.     

Physicochemical analysis of individual atmospheric fine particles based on effective surface-enhanced Raman spectroscopy

Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine the physicochemical properties in atmospheric fine particles at the micrometer level, we described a sensitive and feasible surface-enhanced Raman scattering(SERS) method using Ag foil as a substrate. This novel method enhanced the Raman signal intensities up to 10,000 a.u. for ν(NO_3~-) in fine particles.The SERS effect of Ag foil was further studied experimentally and theoretically and found to have an enhancement factor of the order of ～10~4. Size-fractionated real particle samples with aerodynamic diameters of 0.4–2.5 μm were successfully collected on a heavy haze day,allowing ready observation of morphology and identification of chemical components, such as soot, nitrates, and sulfates. These results suggest that the Ag-foil-based SERS technique can be effectively used to determine the microscopic characteristics of individual fine particles, which will help to understand haze formation mechanisms and formulate governance policies.     

下垫面高度梯度对城市灰尘分布特性及其重金属污染的影响

下垫面高度梯度对城市颗粒污染物的地球化学循环有重要的影响,不同高度下垫面上累积的灰尘可能对城市地表径流与大气颗粒物污染有重要指示作用.本文以不同高度梯度的下垫面,如路面(0 m)、公交站台(3 m)、天桥(5 m)、楼顶(20 m)上的灰尘为研究对象,揭示高度梯度对灰尘颗粒物单位面积质量、粒径组成、重金属含量和粒径污染负荷比的影响.结果表明,随着高度梯度变化,不同下垫面上灰尘颗粒物的单位面积质量之间存在显著差异(p0.05):路面((33.0±27.1)g·m~(-2))楼顶((20.6±11.7)g·m~(-2))天桥((4.4±4.0)g·m~(-2))公交站台((2.3±1.4)g·m~(-2));高度梯度对细灰尘(粒径105μm)的质量比的影响为:公交站台(49.5%)楼顶(40.8%)路面(38.6%)天桥(37.6%);6种重金属在不同高度下垫面的含量不同,其中,Cr、Cu和Ni在公交站台含量最高,Cd和Pb在楼顶含量最高,6种金属(除Cu外)均在路面含量最低.细灰尘(105μm)所占颗粒物污染负荷比为:公交站台(67.4%)楼顶(49.6%)天桥(49.2%)路面(48.1%).临时性管控措施(限行、限产等)和常规性清扫(人工清扫和机械清扫)均能减少灰尘质量,使细灰尘质量比增加,重金属污染负荷有明显削减,但对城市管理来说,后者更经济实用.     

基于pso-SVM的废水厌氧处理过程软测量模型

由于厌氧消化过程的复杂性和厌氧菌的敏感性,保持厌氧消化体系的稳定和高效性是比较困难的.本文在实验室采用IC反应器构建了一套厌氧废水处理系统处理人工合成废水,基于支持向量机(SVM)提出了一种预测废水厌氧处理系统出水挥发性脂肪酸(VFA)浓度和COD去除率的软测量模型.为了提高模型的精确性和鲁棒性,加入pso算法(粒子群算法)优化SVM模型,并引入了分类策略对元数据集进行有效分类.仿真结果表明,基于pso-SVM模型的软测量模型对厌氧废水处理系统出水VFA浓度和COD去除率具有较好的预测能力,模型预测系统COD去除率及出水总VFA浓度测试样本数据相关系数分别为65.86%、85.25%;加入分类策略后,元数据集分成两类,模型预测系统COD去除率测试样本数据相关系数分别为92.34%、83.41%;模型预测系统出水总VFA浓度测试样本数据相关系数分别为99.14%、99.59%,系统预测精度明显提高.引入分类策略对元数据集进行有效分类,基于pso-SVM的软测量模型可为监控、优化和理解厌氧消化过程提供指导.     

紫色土小流域浅层井水中胶体颗粒的季节变化

胶体是多种污染物迁移进入地下水的主要载体.为探究地下水中胶体颗粒的长期动态变化及影响因素,对川中丘陵区紫色土小流域浅层井中胶体颗粒浓度及井水理化性质进行了1 a的原位观测.结果表明:浅层井水中胶体颗粒含量存在较强的季节变异(CV0.5),胶体颗粒质量浓度峰值可达到14.68 mg·L~(-1)(相应的数量浓度为1.34×109L~(-1)),出现在非雨季,由人为取水扰动所致.雨季中前期大雨产流的物理扰动能有效增加井水中胶体颗粒浓度,后期暴雨的促进作用不明显.井水化学性质(EC、Ca2+、Mg2+、DOC)是影响胶体颗粒浓度动态及存在形态最重要的因素.该地区作为饮用水源的浅层井在雨季中前期可能受到因增加的胶体颗粒输入而辅助迁移的农化物质(如农药、P等)对井水质量安全的威胁,建议加强该时段内降雨后井水中胶体及井水理化性质的监测.     

金属氧化物负载γ-Al_2O_3粒子电极对酸性橙Ⅱ的电催化氧化研究

以γ-Al_2O_3作为载体,采用浸渍热分解法制备了Sn、Mn、Cu、Pb单组分氧化物和Sn-Ce-Sb复合氧化物粒子电极。通过对酸性橙II(AOII)的降解实验,以及采用重复试验和扫描电镜(SEM)、紫外光谱扫描等方法,探讨了粒子电极材料的性能。研究结果表明:Sn/γ-Al_2O_3相比于Mn/γ-Al_2O_3、Cu/γ-Al_2O_3、Pb/γ-Al_2O_3等单组分氧化物粒子电极表现出了更好的电催化活性和稳定性。掺杂Ce、Sb后电极表面晶体粒径细小且分布均匀,有利于提高Sn/γ-Al_2O_3粒子电极的性能。电流密度为20 m A/cm2,曝气量0.5 L/min反应条件下,反应3 h后Sn-Ce-Sb/γ-Al_2O_3粒子电极对AOII的去除率为100%,TOC的去除率达84.2%,重复使用5次后TOC去除率仍保持在80%以上。表明Sn-Ce-Sb/γ-Al_2O_3粒子电极具有较好的应用前景。     

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter(DPF), diesel oxidation catalyst(DOC)and exhaust gas recirculation(EGR) under the vehicle driving cycles and regulatory cycle.Total particle number emissions(PNEs) decreased gradually during speed-up of vehicle from 17.3 to 97.3 km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration(PNC),ultrafine particle number concentration(UFPNC) and particulate matter(PM) mass was conducted to compare gaseous compounds(CO, CO_2, HC and NOx). The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NOxinfluencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle(NEDC), was slightly higher than the dilution ratio. In addition, the nuclei mode(DP: ≤ 13 nm) was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul.     

Chemical characterization and source apportionment of atmospheric submicron particles on the western coast of Taiwan Strait, China

Taiwan Strait is a special channel for subtropical East Asian Monsoon and its western coast is an important economic zone in China. In this study, a suburban site in the city of Xiamen on the western coast of Taiwan Strait was selected for fine aerosol study to improve the understanding of air pollution sources in this region. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer(HR-To F-AMS) and an Aethalometer were deployed to measure fine aerosol composition with a time resolution of 5 min from May 1to 18, 2015. The average mass concentration of PM1 was 46.2 ± 26.3 μg/m~3 for the entire campaign. Organics(28.3%), sulfate(24.9%), and nitrate(20.6%) were the major components in the fine particles, followed by ammonium, black carbon(BC), and chloride. Evolution of nitrate concentration and size distribution indicated that local NOx emissions played a key role in high fine particle pollution in Xiamen. In addition, organic nitrate was found to account for 9.0%–13.8% of the total measured nitrate. Positive Matrix Factorization(PMF)conducted with high-resolution organic mass spectra dataset differentiated the organic aerosol into three components, including a hydrocarbon-like organic aerosol(HOA) and two oxygenated organic aerosols(SV-OOA and LV-OOA), which on average accounted for 27.6%,28.8%, and 43.6% of the total organic mass, respectively. The relationship between the mass concentration of submicron particle species and wind further confirmed that all major fine particle species were influenced by both strong local emissions in the southeastern area of Xiamen and regional transport through the Taiwan Strait.     

基于SPAMS的太原市典型生活区停暖前后PM2.5来源及组成

为分析太原市采暖期和非采暖期PM_2.5的特征,利用单颗粒气溶胶质谱仪（SPAMS）分析太原市典型生活区采暖期（2016年3月11-18日）和非采暖期（2016年4月1-7日）PM_2.5的来源及组成.结果表明:① 采暖期（停暖前）颗粒物有机碳、硫酸盐和多环芳烃等信号强度大于非采暖期（停暖后）,而元素碳、硝酸盐、铵盐等反之.② 为了尽可能排除气象因素的影响,选取风向（东南风）、风级（二级）相同时段的颗粒物进行分析,停暖前后颗粒物主要化学组分为有机碳、混合碳和元素碳,采暖前有机碳占比（达51.9%）最高,非采暖期元素碳占比（32.6%）最高.采暖期有机碳、高分子有机物和左旋葡聚糖占比明显高于非采暖期,元素碳、矿物质和重金属反之.③ 停暖前后首要的两类污染源为燃煤和机动车尾气,二者贡献率之和分别高达70.1%和67.4%,可见本地主要受这两类源的影响.燃煤在采暖期为首要污染源,并且贡献比例高于非采暖期,而机动车尾气在非采暖期为首要污染源,且比例明显高于采暖期.研究显示,采暖和非采暖期虽然首要污染源有所差异,但在污染过程中,机动车尾气源的贡献比例均高于优良时段,说明无论是采暖期还是非采暖期,除燃煤排放的影响外,机动车尾气的影响也需得到重视,建议加强机动车燃油品质的升级,使用清洁煤,并在重污染时段采取相应的管控措施.      

天津市道路环境大气颗粒物水溶性无机离子分析

大气颗粒物,尤其是其中的水溶性无机离子,对人体危害很大.天津市大气污染中机动车尾气污染相对较高,为探究不同道路类型下水溶性无机离子的污染特征,于2015年4~5月对天津市四类道路类型分别进行大气颗粒物PM_(2.5)和PM_(10)采样及水溶性离子组分分析,并运用皮尔森相关性分析、水溶性离子比值关系分析及主成分分析方法进行探讨.结果表明,天津市水溶性无机离子主要集中在细颗粒物中,不同离子在不同道路下所占质量分数差异很大,二次污染相对较重;二次离子是水溶性无机离子的重要组成部分,在细颗粒物中含量相对较高,在PM_(2.5)中的含量是PM_(10)中的1~2倍左右;K~+、Mg~(2+)、Na~+与Ca~(2+)之间有较高的同源性;各道路PM_(2.5)和PM_(10)第一贡献因子均是燃烧和二次污染的混合源,第二贡献因子主要为扬尘与交通混合源.