Designing a contaminated soil sampling strategy for human health risk assessment

Human health risk assessment is a site-based approach used to identify the potential health hazards which are induced by an old site contamination. For a proper evaluation of the daily doses of contaminants to which people will be exposed given the future occupation of the site, both a characterization and a quantification of soil pollution are needed. Such information can be provided by soil sampling. Thus the choice of the location, the number, depth and type of soil samples is very important and ought to follow a well-defined strategy. A review of contaminated site sampling practices in Europe and North America could not identify any completely formalized sampling strategy for human health risk assessment. On the contrary there are several approaches which can be roughly classified into two categories: a systematic sampling scheme over the whole site, on the one hand, and a sampling design driven by an initial knowledge of the contamination sources and fitted to the suspected pollution pattern, on the other. The first approach provides a complete coverage of the site but it may be rather expensive and entail useless sampling. The performance of the second depends on the quality of prior information. Actually both methods can be combined as explained hereafter. In view of the specificity of each site, the requirements of health risk assessment and the time and cost constraints, it seems difficult to work out a typical soil sampling strategy suitable for all sites. However, some recommendations can be made according to the site dimensions, the nature, degree and heterogeneity of contamination, and the (future) use of the site. The scientist should thus rely on a thorough examination of all available information (site history, geology and hydrogeology, soil properties, contaminants behaviour , etc.) to delimit contaminated areas as homogeneous as possible and then distribute the sampling points (e.g.using a sampling grid). They should also take the potential exposure paths into account in order to define the areas and soil strata to be sampled as a priority. Statistical and geostatistical tools can be helpful for formulating a sampling strategy as well as for interpreting the collected data. Received: 7 December 2001 Accepted: 24 February 2002     

Study of parameters associated with the determination of cadmium in lake sediments by slurry sampling electrothermal atomic absorption spectrometry

Cadmium concentration in lake sediments is determined by suspending the solid samples in a solution containing 5% (v/v) concentrated nitric acid and 0.1% (v/v) Triton X-100. Three modifiers were tested for the direct determination. The furnace temperature programmes and appropriate amount for each modifier were optimised to get the highest signal and the best separation between the atomic and background signals. The drying stage is performed by programming a 400 °C temperature, a ramp time of 25 s and hold time of 10 s on the power supply of the atomiser. No ashing step is used and platform atomisation is carried out at 2200 °C. W–Rh permanent modifier combined with conventional modifier by delivering 10 μl of 0.50% (w/v) NH₄H₂PO₄ solution was the best chemical modifier for cadmium determination. This modifier also acts as a liquid medium for the slurry, thus simplifying the procedure. Calibration is performed using aqueous standards in the 1–5 μg l⁻¹ range. The optimised method gave a limit of detection of 0.56 ng ml⁻¹, characteristic mass of 10.1±0.8 pg for aqueous standard, 9.6±0.7 pg for slurry samples containing different Cd concentrations and good precision (7.6–5.2%). The method was validated by analysing four certified reference lake sediment materials: LKSD-1, LKSD-2, LKSD-3 and LKSD-4; satisfactory recoveries were obtained (90.0–96.3%) and no statistical differences were observed between the experimental and the certified cadmium concentration. The developed methodology was used to determine cadmium in three ‘real’ sediment samples from lakes in the area of Wielkopolski National Park, Poland.     

腔长失调对光腔衰荡法测量精度的影响

 只考虑腔长失调因素下建立了反射率模拟测量的理论模型。根据高斯光束传输规律分析了腔长失调对衰荡腔模式耦合的影响，推导了腔长失调与谐振腔输出脉冲信号、衰荡信号与反射率之间的关系，模拟了腔长失调在±10mm范围内的光脉冲衰荡现象。结果表明：对于光敏面直径为0.2mm的高速探测器，为了保证10^-6的测量精度，腔长的失调量应控制在±1mm之间。在光路调节中采用具有对数变换功能的示波器和动态范围较大的探测器，可以提高测量精度。     

The raised-cosine wavelets in computerized tomography

In Computerized Tomography (CT), an image must be recovered from its sampled projections in the form of values of the Radon transform. In this work a method of recovering the image is based on the properties of the raised-cosine wavelet. This wavelet has a closed form which allows for certain precomputations and avoids convolution. The rate of convergence of the resulting algorithm to the image density function is found under suitable hypotheses. This algorithm is then tested on the standard Shepp–Logan     

The U.S. Department of Energy (DOE) Sampling and Analytical Chemistry Guide: Doe Methods for Evaluating Environmental and Waste Management Samples

Abstract

DOE Methods for Evaluating Environmental and Waste Management Samples (DOE Methods) is a guidance/methods document to support sampling and analysis activities at DOE sites. DOE Methods is intended to supplement existing guidance documents (e.g., EPA's Test Methods for Evaluating Solid Waste, SW-846), which generally apply to low-level or nonradioactive samples. DOE Methods targets the complexities of DOE radioactive mixed waste and environmental samples. The document contains quality assurance (QA), quality control (QC), safety, sampling, organic analysis, inorganic analysis, and radioanalytical guidance as well as sampling and analytical methods. An addendum is distributed every six months (April and October) with updated guidance and additional methods.

DOE Methods provides a vehicle for technology transfer within the environmental restoration (ER) and waste management (WM) (collectively known as EM) community. As DOE Methods evolves, its usefulness and applicability are anticipated to grow to meet the demands of the DOE/EM mission. At the present time, DOE Methods contains methods and guidance information supplied by DOE sites. Because the EM activities in DOE are not unique to the United States, the international environmental community could benefit from the information gathered for the DOE program. This information could provide additional resources for their EM activities.     

A high‐precision instrument for mapping of rotational errors in rotary stages

A rotational stage is a key component of every X‐ray instrument capable of providing tomographic or diffraction measurements. To perform accurate three‐dimensional reconstructions, runout errors due to imperfect rotation (e.g. circle of confusion) must be quantified and corrected. A dedicated instrument capable of full characterization and circle of confusion mapping in rotary stages down to the sub‐10 nm level has been developed. A high‐stability design, with an array of five capacitive sensors, allows simultaneous measurements of wobble, radial and axial displacements. The developed instrument has been used for characterization of two mechanical stages which are part of an X‐ray microscope.     

基于现场可编程门阵列单探测器复合轴控制技术

为了解决空间激光通信系统中单探测器复合轴结构的粗精解耦难题,通过分析二维关联控制矩阵,得出粗精跟踪解耦的必要条件,提出了一种单探测器复合轴结构的工作方式.在跟踪过程中,相机直接配合子轴执行器完成精跟踪工作,而主轴的跟踪信息由子轴的角度偏转器来提供,同时所有的图像处理算法、位置检测算法、以及粗精伺服控制算法都在现场可编程门阵列中实现,完成了系统的轻小型化设计.实验搭建了测试系统,并对现场可编程门阵列硬件和系统跟踪性能进行测试,结果表明单探测器复合控制系统可以实现跟踪准确度优于3μrad,为工程化奠定了良好的基础.     

地球静止轨道远程交会过程导航性能评估

远程交会是静止轨道共位卫星自主定点置入的关键途径。针对远程交会过程中大距离跨度下相对运动模型的误差信号特性,理论推导了误差的传递机理,给出了相对导航EKF算法期望及噪声特性的定量分析模型。研究表明,确定距离区间存在最优过程噪声量级及其对应的最优滤波性能,且滤波误差与交会距离正相关,可作为全局最优滤波器的定量设计依据,解决了静止轨道远程交会过程EKF导航算法性能的量化评估问题。仿真表明,分析结论正确,相对速度滤波误差全程优于0.005 m/s(1σ),满足交会任务需求。     

高精度中小11径非球面修抛技术研究

为实现高精度中小口径非球面的加工，介绍了一种非球面修抛技术。基于Preston假设，将抛光过程描述成一个线性方程，计算得到材料的去除量与抛光时间、抛光压力和零件转速之间的函数关系。设计了整体修抛法和环带修抛法两种方法，在数控抛光的基础上，对口径为Ф117mm的凹抛物面和口径为Ф17mm凸双曲面进行修抛，修抛后非球面的面形精度PV值为0．184μm，RMS均小于0．032μm，达到了工程化应用要求，实现了中小口径非球面的高精度加工。     

Controlling the Surface Functionalization of Ultrasmall Gold Nanoparticles by Sequence-Defined Macromolecules

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by ¹H NMR spectroscopy, ¹H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative ¹H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm² per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles.