Examination of evidence materials for environmental contamination using activation analysis

A unique application of forensic neutron activation analysis involving the analysis of trace levels of tungsten, cobalt and tantalum was presented as evidence in a murder trial. The evidence materials analyzed included the blous of the victim, bed sheets, a pair of pantyhose used in strangulation, head and public hair from the suspect, and several samples of raw materials used at a factory where the suspect was employed. The stalned areas of the fabrics analyzed showed trace levels of cobalt, tantalum, and tungsten which were not present in the fabric mattrices. The occupation of the suspect exposed him to fine dust particulates containing these trace elements. Although eyewitness accounts indicated that the suspect was in the neighborhood, there was, however, no evidence other that the neutron activation analysis results to indicate the probable presence of the suspect at the scence of the crime. A jury trial accepting neutron activation analysis findings resulted in a conviction.     

Sampling and sampling strategies for environmental analysis

Sampling errors are generally believed to dominate the errors of analytical measurement during the entire environmental data acquisition process. Unfortunately, environmental sampling errors are hardly quantified and documented even though analytical errors are frequently yet improperly reported to the third decimal point in environmental analysis. There is a significant discrepancy in directly applying traditional sampling theories (such as those developed for the binary particle systems) to trace levels of contaminants in complex environmental matrices with various spatial and temporal heterogeneities. The purpose of this critical review is to address several key issues in the development of an optimal sampling strategy with a primary goal of sample representativeness while minimizing the total number of samples and sampling frequencies, hence the cost for sampling and analysis. Several biased and statistically based sampling approaches commonly employed in environmental sampling (e.g. judgmental sampling and haphazard sampling vs. statistically based approaches such as simple random, systematic random, and stratified random sampling) are examined with respect to their pros and cons for the acquisition of scientifically reliable and legally defensible data. The effects of sample size, sample frequency and the use of compositing are addressed to illustrate the strategies for a cost reduction as well as an improved representativeness of sampling from spatially and temporally varied environmental systems. The discussions are accompanied with some recent advances and examples in the formulation of sampling strategies for the chemical or biological analysis of air, surface water, drinking water, groundwater, soil, and hazardous waste sites.     

Improper environmental sampling design bias assessments of coastal contamination

Pollution of coastal areas play an important role in anthropocentric issues. Thus, several analytical tools were developed and optimized in recent years aiming to improve the acquisition of good quality chemical data. Despite these efforts, assessments of the environmental occurrence of hazardous chemicals in coastal regions are often biased by poorly planned sampling campaigns. In coastal zones, the influence of local contamination sources and environmental factors (such as coastal currents, tides, estuarine discharges, depth and luminosity) should be carefully considered before establishing a sampling grid. Moreover, the wrong selection of the environmental matrix to be analyzed, especially by multiresidue methods which include analytes with different physicochemical properties, has also been an important source of bias in many published papers. This critical review provides an overview of the key-factors to be considered during the planning and execution of sampling campaigns seeking to identify and quantify contaminants in environmental samples obtained in coastal areas. Further, a discussion on a more suitable and cost-effective sampling design, based in recent advances, is also presented.     

Passive sampling in environmental analysis

Since its invention more than three decades ago, passive sampling technology has been widely used for environmental monitoring throughout the world. In many cases, it is the only practical means of determining pollution levels caused by numerous anthropogenic chemicals. Passive sampling technology today is used in various areas ranging from workplace exposure monitoring to global issues of climate change arising due to the presence of various chemicals in the atmosphere. In this review, the present status of the technology and its applications will be discussed along with aspects related to its regulatory acceptance and recent trends.     

Problems concerning representative sampling for possible contamination in a complex waste processing facility

A survey is given of the main activities of the Belgoprocess Company, with special emphasis on safety precautions. The routine sampling program for internal contamination consists of urinary and faecal sampling, among others. Faecal samples sometimes reveal low contamination levels. This contamination can be considered as low-level, frequent, and intermittent. No distinct correlation is found with another control technique.A survey is given about uncertainties that might hamper a representative sampling and/or a correct interpretation of the obtained data. Reference is made to the dosimetric models regarding complexity and uncertainties.     

Heliuim-3 mass spectrometry for low-level tritium analysis of environmental samples

Helium-3 (³He) mass spectrometry for the analysis of low-level tritium (³H) concentrations (0.5 to 5 Bq·l^–1) in environmental sample matrices was compared with conventional low-level -decay counting methods. The mass-spectrometry method compared favorably, equalling or surpassing conventional decay-counting methods with respect to most criteria. Additional research and method refinements may make³He mass spectrometry the method of choice for routine, low-level to very-low-level (L<0.5 Bq·l^–1)³H measurements in a wide variety of environmental samples in the future.     

New radiochemical procedures for environmental actinide measurements and data quality control

Suitable separation techniques were prepared for actinide,⁹⁰Sr and²²⁶Ra determinations in environmental and industrial samples. Extraction chromatography with tri-n-octylphosphine oxide (TOPO) and di(2-ethylhexyl) phosphoric acid (HDEHP) solutions was used. IN some cases, a powder of Microthene (Microporous polyethylene) supporting solid TOPO was prepared thus obtaining a material showing better storing and column preparation features.Uranium and²²⁶Ra were determined in phosphorites, phosphoric acid and phosphogypsum.Uranium, thorium and²²⁶Ra were also measured in the low specific activity scales of hydrocarbon production equipment:²²⁶Ra was found to concentrate in some parts of the plant so causing a radiation protection problem.Plutonium and⁹⁰Sr were measured either in some Mediterranean Sea samples or in environmental samples collected in Antarctica. Some interesting sea sediment profiles were also obtained.All the chemical methods were verified by: a) adding some yield tracers (²³²U,²²⁸Th,²⁴²Pu); b) analyzing some certified samples supplied by IAEA and NIST; c) participating in some international intercomparison runs; d) using, when possible, both an analytical and a radiometric method and e) following the radioactivity decay or growth (⁹⁰Y and²²⁶Ra).     

Possibilities of low-level determination of silicon in biological materials by activation analysis

The capabilities of neutron and photon activation analysis (NAA and PAA, respectively) for low-level determination of silicon in biological materials have been examined. Sensitivities of a variety of modes of NAA and PAA with radiochemical separation have been evaluated. Results are presented for silicon in reference materials CSRM 12–2-03 Lucerne, Bowen’s Kale, NIST SRM-1571 Orchard Leaves, and NIST SRM-1515 Apple Leaves. The results were obtained by employing the ²⁹Si(n,p)²⁹Al reaction with fast reactor neutrons and the radiochemical procedure developed for aluminium separation. Possibilities of further improvement of the silicon determination limit down to the μg g^–1 level by employing NAA and PAA with radiochemical separation are outlined.     

Possibilities of low-level determination of silicon in biological materials by activation analysis

The capabilities of neutron and photon activation analysis (NAA and PAA, respectively) for low-level determination of silicon in biological materials have been examined. Sensitivities of a variety of modes of NAA and PAA with radiochemical separation have been evaluated. Results are presented for silicon in reference materials CSRM 12-2-03 Lucerne, Bowen's Kale, NIST SRM-1571 Orchard Leaves, and NIST SRM-1515 Apple Leaves. The results were obtained by employing the 29Si(n,p)29Al reaction with fast reactor neutrons and the radiochemical procedure developed for aluminium separation. Possibilities of further improvement of the silicon determination limit down to the microg g(-1) level by employing NAA and PAA with radiochemical separation are outlined.     

Computerized image processing for evaluation of sampling error in ion microprobe analysis

A method is described for the microscale evaluation of sample heterogeneity as applied to in-situ ion microprobe analysis. Computer feature analysis of digitized ion images is utilized to generate sampling constants, which can be related to the degree of heterogeneity present for a particular constituent in the sample. The expected precision for a series of analyses, or the number of analyses required for a desired precision can also be determined. This approach, which is experimentally verified for NBS SRM-664 low-alloy steel, can be used both to minimize sampling error and to assess the applicability of specific reference materials to microprobe analysis.     

Reference materials in environmental trace organic analysis

 The paper reviews the application of reference materials (RMs) in environmental analysis of trace organic pollutants. The problems related to RM preparation, stability, use, etc. are critically discussed. Importance of analytical quality assurance and the role RMs play in the process are emphasised. Received: 18 May 1999 · Accepted: 27 December 1999     

Determination of low-level90Sr in environmental materials: A novel approach to the classical method

A method was developed for the separation of strontium from large amounts of calcium which does not depend on fuming nitric acid. A sample in the form of mixed carbonates or oxides is stirred into concentrated nitric acid in the proportion 17 w/v. Strontium forms insoluble nitrates while calcium remains in the solution. Two re-precipitation steps combined with an acetone wash yield a very pure strontium salt which is suitable for gravimetric determination of recovery. The method, devised originally for⁹⁰Sr assay in sea water, can also be applied to solid samples which present analytical problems due to their high calcium content.     

Some case studies of skewed (and other ab-normal) data distributions arising in low-level environmental research

Three general classes of skewed data distributions have been encountered in research on background radiation, chemical and radiochemical blanks, and low levels of 85Kr and 14C in the atmosphere and the cryosphere. The first class of skewed data can be considered to be theoretically, or fundamentally skewed. It is typified by the exponential distribution of inter-arrival times for nuclear counting events for a Poisson process. As part of a study of the nature of low-level (anti-coincidence) Geiger-Muller counter background radiation, tests were performed on the Poisson distribution of counts, the uniform distribution of arrival times, and the exponential distribution of inter-arrival times. The real laboratory system, of course, failed the (inter-arrival time) test--for very interesting reasons, linked to the physics of the measurement process. The second, computationally skewed, class relates to skewness induced by non-linear transformations. It is illustrated by non-linear concentration estimates from inverse calibration, and bivariate blank corrections for low-level 14C-12C aerosol data that led to highly asymmetric uncertainty intervals for the biomass carbon contribution to urban "soot". The third, environmentally, skewed, data class relates to a universal problem for the detection of excursions above blank or baseline levels: namely, the widespread occurrence of ab-normal distributions of environmental and laboratory blanks. This is illustrated by the search for fundamental factors that lurk behind skewed frequency distributions of sulfur laboratory blanks and 85Kr environmental baselines, and the application of robust statistical procedures for reliable detection decisions in the face of skewed isotopic carbon procedural blanks with few degrees of freedom.     

Some case studies of skewed (and other ab-normal) data distributions arising in low-level environmental research

Three general classes of skewed data distributions have been encountered in research on background radiation, chemical and radiochemical blanks, and low levels of ⁸⁵Kr and ¹⁴C in the atmosphere and the cryosphere. The first class of skewed data can be considered to be theoretically, or fundamentally skewed. It is typified by the exponential distribution of inter-arrival times for nuclear counting events for a Poisson process. As part of a study of the nature of low-level (anti-coincidence) Geiger– Müller counter background radiation, tests were performed on the Poisson distribution of counts, the uniform distribution of arrival times, and the exponential distribution of inter-arrival times. The real laboratory system, of course, failed the (inter-arrival time) test – for very interesting reasons, linked to the physics of the measurement process. The second, computationally skewed, class relates to skewness induced by non-linear transformations. It is illustrated by non-linear concentration estimates from inverse calibration, and bivariate blank corrections for low-level ¹⁴C–¹²C aerosol data that led to highly asymmetric uncertainty intervals for the biomass carbon contribution to urban “soot”. The third, environmentally skewed, data class relates to a universal problem for the detection of excursions above blank or baseline levels: namely, the widespread occurrence of ab-normal distributions of environmental and laboratory blanks. This is illustrated by the search for fundamental factors that lurk behind skewed frequency distributions of sulfur laboratory blanks and ⁸⁵Kr environmental baselines, and the application of robust statistical procedures for reliable detection decisions in the face of skewed isotopic carbon procedural blanks with few degrees of freedom.     

The reliability of mercury analysis in environmental materials

Nine intercomparisons of the determination of mercury present as impurity in different materials have been organised. 24 laboratories in 10 different countries took part, mainly using activation analysis and atomic absorption techniques. The results show that the reliability of the data produced and reported in this area leaves much to be desired, and that continuous control of the quality of mercury analysis in the extremely low concentration range is essential.     

Application of inductively coupled plasma sector field mass spectrometry for low-level environmental americium-241 analysis

An improved and novel sample preparation method for ²⁴¹Am analysis by inductively coupled plasma sector field mass spectrometry has been developed. The procedure involves a selective CaF₂ pre-concentration followed by an extraction chromatographic separation using TRU™ resin. The achieved absolute detection limit of 0.86 fg (0.11 mBq) is comparable to that of alpha spectrometry (0.1 mBq) and suitable for low-level environmental measurements. Analysis of different kinds of environmental standard reference materials (IAEA-384 - Fangataufa lagoon sediment, IAEA-385 - Irish Sea sediment and IAEA-308 - Mixed seaweed from the Mediterranean Sea) and alpha spectrometry were used to validate the procedure. The chemical recovery of sample preparation ranged between 72 and 94%. The results obtained are in good agreement with reference values and those measured by alpha spectrometry. The proposed method offers a rapid and less labor-intensive possibility for environmental ²⁴¹Am analysis than the conventionally applied radioanalytical techniques.     

Multi-element analysis in ecosystems: basic conditions for representative sampling of plant materials

Summary To obtain comparable results of multi-element analysis on plant materials by different institutes a harmonized sampling procedure within terrestrial and marine ecosystems is an essential condition. The heterogeneous distribution of chemical elements in living organisms is influenced by different biological parameters. These parameters are mainly characterized by genetic predetermination, seasonal changes, edaphic and climatic conditions, and delocalization processes of chemical substances by metabolic activities. In this article an attempt was made to divide the biological variations of the element content in plants into 5 systematic levels, which are: 1. the plant species, 2. the population, 3. the stand (within an ecosystem), 4. the individual, and 5. the plant compartment. Each of these systematic levels can be related to 1. genetic variabilities, 2. different climatic, edaphic and anthropogenic influences, 3. microclimatic or microedaphic conditions, 4. age of plants (stage of development), exposure to environmental influences (light, wind, pollution etc.), seasonal changes, and 5. transport and deposition of substances within the different plant compartments (organs, tissues, cells, organelles).

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Multielement-Analyse in Ökosystemen: Bedingungen für eine repräsentative Probenahme von Pflanzenmaterial

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Paper presented at the 5th International Workshop on Trace Elements in Analytical Medicine and Biology November, 1988.