Comments on "Ion adsorption components in liquid/solid systems"

Recently, Wu et al. (J Environ Sci 18(2006) 1167-1175) published a paper entitled as above. In the paper, the authors proposed a plotting method for describing adsorption isotherm, where adsorption density (q e) was plotted against the ratio of equilibrium concentration/particle concentration (Ce/W0) rather than (Ce) as traditionally defined. The authors claimed that this plot can eliminate the "particle concentration effect" (i.e., adsorption isotherm declines with increasing particle concentration), which may otherwise be inevasible with traditionally defined adsorption isotherms. We think that their conclusion is conceptually flawed and the plot may cause substantial inconstancy problems in practice.     

Po-210 and Pb-210 as atmospheric tracers and global atmospheric Pb-210 fallout: a review

Over the past ∼5 decades, the distribution of ²²²Rn and its progenies (mainly ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po) have provided a wealth of information as tracers to quantify several atmospheric processes that include: i) source tracking and transport time scales of air masses; ii) the stability and vertical movement of air masses iii) removal rate constants and residence times of aerosols; iv) chemical behavior of analog species; and v) washout ratios and deposition velocities of aerosols. Most of these applications require that the sources and sink terms of these nuclides are well characterized.Utility of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po as atmospheric tracers requires that data on the ²²²Rn emanation rates is well documented. Due to low concentrations of ²²⁶Ra in surface waters, the ²²²Rn emanation rates from the continent is about two orders of magnitude higher than that of the ocean. This has led to distinctly higher ²¹⁰Pb concentrations in continental air masses compared to oceanic air masses. The highly varying concentrations of ²¹⁰Pb in air as well the depositional fluxes have yielded insight on the sources and transit times of aerosols. In an ideal enclosed air mass (closed system with respect to these nuclides), the residence times of aerosols obtained from the activity ratios of ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb are expected to agree with each other, but a large number of studies have indicated discordance between the residence times obtained from these three pairs. Recent results from the distribution of these nuclides in size-fractionated aerosols appear to yield consistent residence time in smaller-size aerosols, possibly suggesting that larger size aerosols are derived from resuspended dust. The residence times calculated from the ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb activity ratios published from 1970’s are compared to those data obtained in size-fractionated aerosols in this decade and possible reasons for the discordance is discussed with some key recommendations for future studies.The existing global atmospheric inventory data of ²¹⁰Pb is re-evaluated and a ‘global curve’ for the depositional fluxes of ²¹⁰Pb is established. A current global budget for atmospheric ²¹⁰Po and ²¹⁰Pb is also established. The relative importance of dry fallout of ²¹⁰Po and ²¹⁰Pb at different latitudes is evaluated. The global values for the deposition velocities of aerosols using ²¹⁰Po and ²¹⁰Pb are synthesized.     

引信步进应力加速试验贮存寿命预测研究

目的 针对某机电引信加速寿命试验数据,采用传统统计分析方法存在计算量大、寿命预测精度难以保证的问题,开展与智能算法相结合的引信贮存寿命预测研究。方法 针对步进应力加速寿命试验数据,采用贝叶斯理论的环境因子法,对各级应力下的贮存时间进行折合计算。利用进化策略对粒子群算法进行改进,进而对所建立的BP神经网络预测模型的全局参数进行调整和优化,突破传统方法的局限。将折合后的试验时间、样本量、应力水平作为网络输入,失效数作为输出,来预测引信贮存寿命。结果 利用训练好的 BP神经网络预测引信在正常应力水平下的失效数,计算其贮存可靠度。在迭代402次后,模型找到最优解,且预测误差在1%以内。结论 步进应力加速寿命试验与智能算法相结合的方法计算过程简单,预测精度较高,可有效提高引信贮存寿命的预测精度。     

长江三角洲2017年机动车IVOCs排放清单构建及其对SOA的生成影响

中等挥发性有机物（IVOCs）对大气中二次有机气溶胶（SOA）的生成有重要贡献,但尚未包括在目前的排放清单中.本研究以长三角地区为研究对象,分别基于排放因子法和IVOCs/POA比例系数法对长三角地区2017年机动车IVOCs的排放量进行估算,构建长三角地区2017年机动车IVOC排放清单,分析其不确定性并估算其对SOA生成潜势的影响.基于排放因子法的结果表明,2017年长三角地区机动车IVOCs排放总量为3.58万t,SOA的生成潜势为695 t,其中载货汽车的IVOCs排放量在长三角大部分城市的占比均超过70%;从燃料类型来看,柴油车的IVOCs排放量远高于汽油车.基于IVOCs/POA比例系数法的结果表明,由不同的IVOCs/POA比例以及不同的POA/PM_2.5占比得到的排放清单结果差别巨大,最大值可达64.2万t,最小仅为5.2万t,造成的SOA生成潜势分别为1.55万t和1032 t.本研究表明基于不同的估算方法构建的IVOCs排放清单结果差别巨大,具有很大的不确定性,将直接影响后续空气质量模型对SOA的模拟结果.因此,需进一步将不同清单结果用于空气质量模型中对SOA进行模拟,通过与观测值的比较,从而获得较为准确的长三角地区机动车IVOCs排放清单.     

环境磁学在监测城市河流沉积物污染中的应用

环境磁学因简便、快速、经济等特征而逐渐广泛应用于城市环境污染研究,并得到了大量学者的认可.与此同时,对环境磁学污染响应机理的研究也成为当前环境磁学发展突破点.本文选取流经兰州市不同功能区（绿地区、生活区、商业区、工业区）的典型河流——寺儿沟为研究对象,通过环境磁学、元素、粒度等指标对其4个功能区河段沉积物的磁性特征进行...     

北方强沙尘暴天气过程对广州空气质量影响的个例分析

2009年4月23—25日,我国内蒙古、甘肃、陕西等地区出现了1次强沙尘暴天气过程,沙尘暴产生的浮尘自北南下,于26日开始影响广州.期间,沙尘暴沿途城市的可吸入颗粒物(PM10)浓度先后升高.本文通过对广州4月27日—29日(浮尘时段)和5月12—14日(非浮尘时段)的空气颗粒物进行质量浓度分析,发现浮尘时段PM10的浓度均值为0.231mg·m-3,较非浮尘时段(0.103mg·m-3)大1倍.化学分析结果发现金属元素含量、金属元素富集因子、可溶性阴阳离子含量等在这两个时段也均存在显著差异.浮尘时段颗粒物中金属元素含量的总浓度为53.5μg·m-3,比非浮尘时段的总浓度(28.5μg·m-3)翻了近1倍.浮尘时段的Na、Ti、Zn、Cu、Cr浓度较非浮尘时段的增加幅度在0～100%之间,从富集因子来看,非浮尘时段均高于浮尘时段,说明污染源主要来自广州本地源;浮尘时段的K、Mg、Al、Fe、Mn、V、Co浓度较非浮尘时段的增幅在100%以上,其富集因子均高于非浮尘时段,说明污染源主要来自于外来源;而Ni、Pb、Cd3种元素浓度增幅为负值,说明沙尘携带这3种元素的量可以忽略,且冷空气的稀释作用使得它们在浮尘时段的富集系数远远低于非浮尘时段.另外,通过对水溶性离子的分析发现,浮尘天气时段空气颗粒物中各种水溶性阴阳离子含量都有所升高,但NH4+、NO3-、SO24-3种离子的质量浓度,无论在浮尘还是非浮尘时段,差别均不显著(均占约82%),说明这3种离子都是PM10中最主要的可溶性阴阳离子.并且从浮尘时段的气象场分析和后向轨迹计算表明,此次广州沙尘的源地来自内蒙地区.     

2016年10～11月期间北京市大气颗粒物污染特征与传输规律

本研究采用气溶胶化学组分在线监测仪（ACSM）对北京地区2016年10月15日~11月15日期间非难熔性PM₁（NR-PM₁）化学组分进行实时连续在线观测,探讨了NR-PM₁化学组分的演变特征;运用潜在源贡献分析（PSCF）法和气象-空气质量模式（WRF-CAMx）识别了北京PM_2.5潜在污染源区和传输路径,揭示了PM_2.5净传输通量的垂直分布特征.结果表明,北京秋季NR-PM₁和PM_2.5质量浓度分别为（59.16±57.05）μg·m^-3和（89.82±66.66）μg·m^-3,其中NR-PM₁平均占PM_2.5的（70.31±22.28）%.整个观测期间,有机物（Org）、硝酸盐（NO₃^-）、硫酸盐（SO₄^2-）、铵盐（NH₄⁺）和氯化物（Chl）分别占NR-PM₁总质量浓度的（42.75±11.35）%、（21.27±7.72）%、（19.11±7.08）%、（12.19±2.64）%和（4.68±3.24）%,不同化学组分的日变化特征存在明显差异.对北京秋季NR-PM₁污染影响较大的潜在源区主要集中在河北南部、河南东北部及山东西部,重污染期间保定、北京南部及廊坊等城市对NR-PM₁贡献较大.WRF-CAMx模拟结果表明,PM_2.5总的净传输通量呈现出显著的垂直分布特征.整个观测期间,毗邻城市主要向北京输入PM_2.5,净通量最大出现在海拔600~1000 m;而重污染前期外来源输送PM_2.5主要位于高空,直到污染最严重的11月5日,PM_2.5转为近地面传输,说明高空和近地面传输是影响北京秋季PM_2.5重污染形成的重要因素.同时鉴别出了两种传输路径,即西南-东北方向（保定→北京→承德）和西北-东南方向（张家口→北京→廊坊北→天津）.     

水稻光合同化碳在土壤不同粒径、密度分组中的分配特征

水稻生长影响土壤有机质在土壤及其各组分中的分布,是关系土壤有机质储量的重要因子.为量化水稻光合同化碳在土壤不同粒径和密度组分中的分布,进而为水稻土有机质积累持续机制与固碳潜力研究提供数据支撑,应用14C连续标记示踪技术,以当地主栽水稻品种"中优169"为供试作物,分别选取亚热带区4种典型稻田土壤,通过土壤有机质物理分组方法探讨了水稻根际输入的光合碳在土壤物理组分(粒径、密度)中的含量和分配特征.结果表明,水稻标记种植80 d后,250～2 000μm粒径的SOC14含量范围为118.23～309.94 mg.kg-1,SOC14/SOC的比例范围为0.52%～1.55%,均大于20～250μm、<20μm这2个粒径的SOC14含量和SOC14/SOC的比例,250～2 000μm、20～250μm这2个粒径的轻组组分的SOC14含量均显著大于相应的重组组分的SOC14含量,说明稻田生态系统通过水稻的根际沉积作用将有机碳(水稻光合同化碳)主要固定在大粒径的轻组组分中,从而提高了土壤有机碳含量.相关分析表明,250～2 000μm粒径与其轻、重组组分、<20μm粒径、20～250μm粒径的SOC14含量之间均呈显著性正相关,而<20μm、20～250μm粒径的轻组组分的SOC14含量之间呈极显著性负相关.     

Pollution sources of atmospheric fine particles and secondary aerosol characteristics in Beijing

To investigate the secondary formation and pollution sources of atmospheric particles in urban Beijing, PM_2.5 and its chemical components were collected and determined by URG-9000D ambient ion monitor (AIM) from March 2016 to January 2017. Among water-soluble ions (WSIs), NO₃^?, SO₄^2- and NH₄⁺ (SNA) had the largest proportion (77.8%) with the total concentration of 23.8 μg/m³. Moreover, as fine particle pollution worsened, the NO₃^?, SO₄^2- and NH₄⁺ concentrations increased basically, which revealed that secondary aerosols were the main cause of particle pollution in Beijing. Furthermore, the particle neutralization ratio (1.1), the ammonia to sulfate molar ratio (3.4) and the nitrate to sulfate molar ratio (2.2) showed that secondary aerosols are under ammonium-rich conditions with the main chemical forms of NH₄NO₃ and (NH₄)₂SO₄, and vehicle emission could be the main anthropogenic source of secondary aerosols in Beijing. Source analysis further indicated that secondary aerosols, solid fuel combustion, dust and marine aerosol were the principal pollution sources of PM_2.5, accounting for about 46.1%, 22.4% and 13.0%, respectively, and Inner Mongolia and Hebei Provinces could be considered as the main potential sources of PM_2.5 in urban Beijing. In addition, secondary formation process was closely related with gaseous precursor emission amounts (SO₂, NO₂, NH₃ and HONO), atmospheric ozone concentration (O₃), meteorological conditions (temperature and relative humidity) and particle components. Sensitive analysis of the thermodynamic equilibrium model (ISORROPIA II) revealed that controlling total nitrate (TN) is the effective measure to mitigate fine particle pollution in Beijing.     

南京市可吸入颗粒物（PM10）来源及防治对策

通过分析南京市可吸入颗粒物（PM10）来源分布特征,以及源贡献值和分担率的时空分布特征,提出南京市大气颗粒物污染防治对策;加强防治扬尘污染,巩固煤烟尘的治理成果,机动车尾气尘污染防治,提高环境监测能力和加强科学研究等措施。