挥发性有机物在线气相色谱仪响应漂移订正方法研究

挥发性有机化合物（VOCs）作为大气对流层臭氧和二次有机气溶胶的重要前体物,其精确监测对评估和改善空气质量至关重要. 在线气相色谱仪（GC）广泛用于VOCs监测,其数据处理中如何订正仪器响应漂移是一项极具挑战的工作. 本文通过分析北京市2023年3月至2024年7月为期16个月的VOCs在线GC响应漂移及数据订正情况,提出了一种基于多点标准曲线与高频率零/跨检查结果,采用线性插值法对在线GC响应漂移进行订正的质量控制方法,可有效控制仪器响应漂移给后续数据处理带来的误差,提高VOCs长期在线监测数据的可靠性与稳定性. 研究表明,在标准曲线相关系数大于0.98的情况下,约80%的目标VOCs在监测期内的响应漂移波动幅度仍可达±50%,可见仪器响应漂移对VOCs长期监测数据质量的影响不容忽视. 高频率的零/跨检查有利于将仪器响应漂移误差控制在较小的范围内. 每4—8 d完成1次零/跨检查且每个点连续测量3次时,可将92%—94%的目标VOCs跨度偏差控制在±15%以内,82%—88%的目标VOCs跨度偏差控制在±10%以内,61%—66%的目标VOCs跨度偏差控制在±5%范围内. 相比仅用标准曲线定量,约87%的目标VOCs浓度在订正后有不同程度下降. 其中,15种芳香烃平均降低5%—15%,23种烷烃平均降低1%—26%,10种烯烃平均降低4%—17%. 异丁烯、1-戊烯、乙炔是少数订正后浓度有较明显上升的化合物,上升幅度分别为21%、8%和7%. 表明忽略响应漂移而仅用有限次数的标准曲线定量可能对大部分VOCs浓度高估、对个别VOCs浓度低估. 研究结果可为VOCs在线GC的质量控制和数据订正提供科学的依据和方法.     

Probability distributions and statistical inference for axial data

Observations on axes which lack information on the direction of propagation are referred to as axial data. Such data are often encountered in enviromental sciences, e.g. observations on propagations of cracks or on faults in mining walls. Even though such observations are recorded as angles, circular probability models are inappropriate for such data since the constraint that observations lie only in [0, π) needs to be enforced. Probability models for such axial data are argued here to have a general structure stemming from that of wrapping a circular distribution on a semi-circle. In particular, we consider the most popular circular model, the von Mises or circular normal distribution, and derive the corresponding axial normal distribution. Certain properties of this distribution are established. Maximum likelihood estimation of its parameters are shown to be surprisingly, in contrast to trigonometric moment estimation, numerically quite appealing. Finally we illustrate our results by several real life axial data sets. Received: September 2004/ Revised: December 2004     

Obtaining species: sample size considerations

Suppose fish are to be sampled from a stream. A fisheries biologist might ask one of the following three questions: ‘How many fish do I need to catch in order to see all of the species?’, ‘How many fish do I need to catch in order to see all species whose relative frequency is more than 5%?’, or ‘How many fish do I need to catch in order to see a member from each of the species A, B, and C?’. This paper offers a practical solution to such questions by setting a target sample size designed to achieve desired results with known probability. We present three sample size methods, one we call ‘exact’ and the others approximate. Each method is derived under assumed multinomial sampling, and requires (at least approximate) independence of draws and (usually) a large population. The minimum information needed to compute one of the approximate methods is the estimated relative frequency of the rarest species of interest. Total number of species is not needed. Choice of a sample size method depends largely on available computer resources. One approximation (called the ‘Monte Carlo approximation’) gets within ±6 units of exact sample size, but usually requires 20–30 minutes of computer time to compute. The second approximation (called the ‘ratio approximation’) can be computed manually and has relative error under 5% when all species are desired, but can be as much as 50% or more too high when exact sample size is small. Statistically, this problem is an application of the ‘sequential occupancy problem’. Three examples are given which illustrate the calculations so that a reader not interested in technical details can apply our results.     

Experimental study of recirculating flows generated by lateral shock waves in very large channels

Due to the lack of data on hydraulic-jump dynamics in very large channels, the present paper describes the main characteristics of the velocity field and turbulence in a large rectangular channel with a width of 4 m. Although a hydraulic jump is always treated as a wave that is transversal to the channel wall, in the case of this study it has a trapezoidal front shape, first starting from a point at the sidewalls and then developing downstream in an oblique manner, finally giving rise to a trapezoidal shape. The oblique wave front may be regarded as a lateral shockwave that arises from a perturbation at a certain point of the lateral wall and travels obliquely toward the centreline of the channel. The experimental work was carried out at the Coastal Engineering Laboratory of the Water Engineering and Chemistry Department of the Technical University of Bari (Italy). In addition to the hydraulic jump formation, a large recirculating flow zone starts to develop from the separating point of the lateral shock wave and a separate boundary layer occurs. Intensive measurements of the streamwise and spanwise flow velocity components along one-half width of the channel were taken using a bidimensional Acoustic Doppler Velocimeter (ADV). The water surface elevation was obtained by means of an ultrasonic profiler. Velocity vectors, transversal velocity profiles, turbulence intensities and Reynolds shear stresses were all investigated. The experimental results of the separated boundary layer were compared with numerical predictions and related work presented in literature and showed good agreement. The transversal velocity profiles indicated the presence of adverse pressure gradient zones and the law of the wall appears to govern the region around the separated boundary layer.     

洱海流域湖泊湖滨带福寿螺时空分布

福寿螺是世界100种恶性入侵物种中唯一的水生螺,已对大理及周边地区造成了不可估量的经济损失和生态安全问题。为探究洱海流域湖泊湖滨带福寿螺时空分布及与水环境因子、季节之间的关系,探索福寿螺在大理地区的入侵机制,为大理地区高效防治福寿螺提供建设性建议,并为福寿螺时空分布格局的相关研究积累资料,于2016年冬季和2017年夏季在大理洱海及其上游水源地海西海、西湖、茈碧湖、绿玉池,以及罗时江湿地进行系统抽样,利用统计软件分析福寿螺分布与水质关系,结合GIS,分析福寿螺的时空分布以及潜在入侵危害。结果表明,从空间尺度上,洱海流域福寿螺有进一步扩散的趋势;从时间尺度上,福寿螺的密度随季节性水位的改变而变化;洱海流域的福寿螺分布和水质因子之间基本无相关性。     

基于PBPK模型的大鼠体内镉分布的比较：联合暴露及单独暴露

环境中同时存在着多种重金属元素,联合暴露与单独暴露时,重金属在体内的蓄积分布情况也可能有所差异。为探究重金属元素(汞、铬、砷、铅)对镉(Cd)在体内分布的影响,建立了大鼠在Cd暴露下的药代动力学(PBPK)模型,并进行了包括Cd在内5种重金属的联合毒性实验,比较了Cd单独给药与重金属混合物给药2种方式下大鼠肝脏、肾脏中的Cd浓度水平。结果表明,联合暴露高(Hg Cl23.67 mg·kg~(-1),NaAsO_2 3.67 mg·kg~(-1),CdCl_2 10.55 mg·kg~(-1),K_2Cr_2O_7 6.40 mg·kg~(-1),Pb(OOCCH_3)_2·3H_2O 133.33 mg·kg~(-1))、中(HgCl_20.367 mg·kg~(-1),NaAsO_2 0.367 mg·kg~(-1),CdCl_2 1.055 mg·kg~(-1),K2Cr2O70.640 mg·kg~(-1),Pb(OOCCH_3)_2·3H_2O 13.333 mg·kg~(-1))、低(HgCl_2 0.0367 mg·kg~(-1),Na As O20.0367 mg·kg~(-1),Cd Cl20.1055 mg·kg~(-1),K_2Cr_2O_7 0.0640 mg·kg~(-1),Pb(OOCCH3)2·3H2O 1.3333 mg·kg~(-1))剂量组大鼠肝脏中Cd浓度分别为13.37、0.78和0.06μg·g~(-1);肾脏中Cd浓度分别为14.41、1.64和0.15μg·g~(-1)。与对照组相比,暴露组中Cd浓度有显著升高,且不同剂量组之间均有显著性差异。同剂量Cd单独暴露的PBPK模拟结果显示,肝脏及肾脏中的Cd浓度水平落在联合毒性实验结果的浓度范围内,初步推断其他4种重金属的联合暴露并没有影响Cd在大鼠肾脏和肝脏中的浓度分布。     

2015年12月南京北郊细粒子的光学特性

于2015年12月采用三波长光声黑碳光度仪（PASS-3）对PM2.5 光学特性进行实时在线观测,同时采用大气粒子检测仪（BAM-1020）和扫描电迁移率粒径谱仪（SMPS）分别在线测量PM2.5和PM0.3 质量浓度.结果表明,观测期间南京北郊的气溶胶在532 nm波段的吸收、散射和消光系数分别为（56.34±27.09）Mm-1、（461.68±267.97）Mm-1和（518.02±290.94）Mm-1,其中,散射系数高于上海、广州等地的观测值,明显低于西安、沈阳等地的观测值,而吸收系数均低于其他城市.气溶胶散射和吸收系数的日变化呈双峰特性,且与NOx和CO日变化趋势一致,说明其主要受交通排放影响.气溶胶消光系数与ρ（PM2.5）呈显著的线性正相关,与大气能见度呈反比例负相关.PM2.5的质量消光效率为4.43 m2·g-1.ρ（PM0.3）占ρ（PM2.5）的质量百分比越高,其质量消光效率越大.     

燃煤烟气脱硫脱硝脱碳一体化技术的研究进展

我国长期以来一直以煤炭为主要能源,其燃烧排放的SO_x和NO_x是大气环境中主要的污染物,而CO₂的大量排放也会导致一系列环境问题的出现。本文总结了燃煤烟气的净化方法,重点介绍了吸附法、吸附机理、传统吸附剂以及新型吸附剂、影响吸附效果的因素和吸附剂循环再生情况。最后总结了吸附剂目前存在的一些缺陷以及未来的发展方向。

     

基于风险商法的中国典型淡水水域微塑料生态风险评价

微塑料是一种广泛存在于各种环境介质中的新兴污染物,但目前对于该污染物的生态风险评价方法尚不成熟。本文基于物种敏感性分布（species sensitivity distribution,SSD）使用风险商法,对中国13条典型河流微塑料污染进行了生态风险评估。首先构建了淡水生物对微塑料的敏感性分布曲线,计算出微塑料对淡水生物的预测无影响浓度为1.9×10⁵ n·m^-3,再根据各河流的微塑料赋存状况计算出对应的风险商值。结果显示,洞庭湖、洪湖和三峡水库等6个水域的风险商值<0.1,无微塑料污染生态风险;珠江、太湖、鄱阳湖、茅洲河、岷江（成都段）和玛纳斯河有个别采样点风险商值>0.1,存在潜在微塑料污染生态风险;而黄河下游风险商值>1,存在较为严重的微塑料污染生态风险。