Practical application of 1H benchtop NMR spectroscopy for the characterization of a nonaqueous phase liquid from a contaminated environment

Nonaqueous phase liquids (NAPLs) located at the surface of the water table and/or below the water table are often a significant source for groundwater contamination near current or former commercial/industrial facilities. Due to the complex and long history of many industrial sites, these NAPLs often contain a complex mixture of contaminants and as such can be difficult to fully characterize using conventional analytical methods. Remediation and risk assessment activities at sites containing NAPLs may, subsequently, be hindered as the contamination profile may not be fully understood. This paper demonstrates the application of bench-scale ¹H nuclear magnetic resonance (NMR) spectroscopy as a practical tool to assist with the characterization of complex NAPLs. Here, a NAPL collected from a contaminated site situated near a former chemical manufacturing facility was analyzed using a combination of one-dimensional (1D) ¹H NMR spectroscopy and two-dimensional (2D) ¹H J-resolved spectroscopy (JRES). It is shown that 1D NMR experiments are useful in the rapid identification of the classes of compounds present, whereas 2D JRES NMR experiments are useful in identifying specific compounds. The use of benchtop NMR spectroscopy as a simple and cost effective tool to assist in the analysis of contaminated sites may help improve the practical characterization of many heavily contaminated sites and facilitate improved risk assessments and remedial strategies.     

Fast determination of phenols in contaminated soils

An extraction method for the determination of phenols in contaminated soils, based on the application of solid-phase microextraction (SPME) coupled with GC-flame ionization detection analysis, was developed and tested. This method was developed using a natural soil spiked with phenol to a concentration level typical of an acute contamination event that can occur in an industrial site. The effects of the extraction parameters (pH, extraction time and salt concentration) on the extraction efficiency were studied and the method was then applied to determine the pollutant concentration at the beginning and during the biological treatment of a soil, contaminated with phenol and 3-chlorophenol, respectively. The SPME results were validated by comparison with those obtained with an US Environmental Protection Agency certified extraction method. The SPME method was also successfully applied to the determination of the adsorption behavior of 3-chlorophenol on a natural clay soil and was shown to be suitable for different matrices and phenolic compounds. Application of SPME technique results in a sharp reduction of the extraction times with negligible solvent consumption.     

Analytical methods for monitoring contaminants in food—An industrial perspective

Incoming legislation on the registration, evaluation, authorisation and restriction of chemical substances places responsibility on the chemical industry, including downstream users of chemicals, to provide appropriate safety information with which to improve the protection of human health and the environment through the better and earlier identification of the intrinsic properties of chemical substances. Food consumption is only one of several potential exposure routes, but if industrial chemicals enter the food chain, the diet may be a significant pathway of human exposure. Consequently strong measures are taken to protect the integrity of the human food chain and these are constantly revised to address perceived chemical safety threats. In order to understand the risk presented by the possible presence of a chemical residue in food, knowledge is required of its toxicology and of the level of exposure. Reliable exposure assessment requires robust analytical methodology. Existing standards for the validation and performance evaluation of methods have led to improved analytical capability and better inter-laboratory agreement of results. However, increasing the availability of robust, cost-effective methodology should be the benchmark for future developments in the field of food chemical residue analysis. Chromatography meets the needs of target analyses well and largely provides the selectivity of measurement needed to assess compliance with food regulatory limits. However, to keep pace with the increased need for expanded analytical capability – faster throughput, more analytes per sample – chromatographic separation capability still needs to grow. In this respect, orthogonal separation techniques and multi-dimensional chromatography are key tools for the future.     

Optimization of the matrix solid-phase dispersion sample preparation procedure for analysis of polycyclic aromatic hydrocarbons in soils: comparison with microwave-assisted extraction

A fast and simple preparation procedure based on the matrix solid-phase dispersion (MSPD) technique is proposed for the first time for the isolation of 16 polycyclic aromatic hydrocarbons (PAHs) from soil samples. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-c,d]pyrene were considered in the study. Extraction and clean-up of samples were carried out in a single step. The main parameters that affect extraction yield, such as dispersant, type and amount of additives, clean-up co-sorbent and extractive solvent were evaluated and optimized. The addition of an alkali solution in MSPD was required to provide quantitative recoveries. Analytical determinations were carried out by high performance liquid chromatography (HPLC) with fluorescence detection. Quantification limits (between 0.01 and 0.6 ng g(-1) dry mass) were well below the regulatory limits for all the compounds considered. The extraction yields for the different compounds obtained by MSPD were compared with the yields obtained by microwave-assisted extraction (MAE). To test the accuracy of the MSPD technique, the optimized methodology was applied to the analysis of standard reference material BCR-524 (contaminated industrial soil), with excellent results.     

New radioisotope methods of analysis based on the application of radioactive reagents

Graph-Calculation Method of analysis has been developed. The new method considerably increases (in comparison with Radioactive Reagent Method) the sensitivity of determinations and allows to enlarge the list of suitable reagens as well as permissible limits of relative quantities of radioactive reagent applied. The equations have been derived which allow to calculate the degree of interaction of the reacting substances and to carry out model calculations for any radioisotope method of analysis applying radioactive reagents.     

Comparison of three fish bioaccumulation models for ecological and human risk assessment and validation with field data

This article compares two bioconcentration Quantitative Structure Activity Relationships (QSARs) for fish applied in human risk assessments with the mechanistic bioaccumulation model OMEGA and field data. It was found that all models are virtually similar up to a Kow of 10(6). For substances with a Kow higher than 10(6), the fish bioconcentration curve in the risk assessment model EUSES decreases parabolically. In contrast, OMEGA bioaccumulation outcomes approximately show a linear increase, based on mechanistic bioconcentration and biomagnification properties of chemicals. The OMEGA-outcomes are close to the fish bioconcentration outcomes of the risk assessment model CalTOX. For very hydrophobic substances, field accumulation data in freshwater and marine fish species are closer to OMEGA- and CalTOX-outcomes compared to EUSES. The results also show that it is important to include biomagnification in fish and lipid content of fish in human exposure models.     

A kinetic model for predicting biodegradation

Biodegradation plays a key role in the environmental risk assessment of organic chemicals. The need to assess biodegradability of a chemical for regulatory purposes supports the development of a model for predicting the extent of biodegradation at different time frames, in particular the extent of ultimate biodegradation within a ‘10?day window’ criterion as well as estimating biodegradation half-lives. Conceptually this implies expressing the rate of catabolic transformations as a function of time. An attempt to correlate the kinetics of biodegradation with molecular structure of chemicals is presented. A simplified biodegradation kinetic model was formulated by combining the probabilistic approach of the original formulation of the CATABOL model with the assumption of first order kinetics of catabolic transformations. Nonlinear regression analysis was used to fit the model parameters to OECD 301F biodegradation kinetic data for a set of 208 chemicals. The new model allows the prediction of biodegradation multi-pathways, primary and ultimate half-lives and simulation of related kinetic biodegradation parameters such as biological oxygen demand (BOD), carbon dioxide production, and the nature and amount of metabolites as a function of time. The model may also be used for evaluating the OECD ready biodegradability potential of a chemical within the ‘10-day window’ criterion.     

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     

A kinetic model for predicting biodegradation

Biodegradation plays a key role in the environmental risk assessment of organic chemicals. The need to assess biodegradability of a chemical for regulatory purposes supports the development of a model for predicting the extent of biodegradation at different time frames, in particular the extent of ultimate biodegradation within a '10 day window' criterion as well as estimating biodegradation half-lives. Conceptually this implies expressing the rate of catabolic transformations as a function of time. An attempt to correlate the kinetics of biodegradation with molecular structure of chemicals is presented. A simplified biodegradation kinetic model was formulated by combining the probabilistic approach of the original formulation of the CATABOL model with the assumption of first order kinetics of catabolic transformations. Nonlinear regression analysis was used to fit the model parameters to OECD 301F biodegradation kinetic data for a set of 208 chemicals. The new model allows the prediction of biodegradation multi-pathways, primary and ultimate half-lives and simulation of related kinetic biodegradation parameters such as biological oxygen demand (BOD), carbon dioxide production, and the nature and amount of metabolites as a function of time. The model may also be used for evaluating the OECD ready biodegradability potential of a chemical within the '10-day window' criterion.     

QSAR Models for Human Carcinogenicity: An Assessment Based on Oral and Inhalation Slope Factors

Carcinogenicity is a crucial endpoint for the safety assessment of chemicals and products. During the last few decades, the development of quantitative structure–activity relationship ((Q)SAR) models has gained importance for regulatory use, in combination with in vitro testing or expert-based reasoning. Several classification models can now predict both human and rat carcinogenicity, but there are few models to quantitatively assess carcinogenicity in humans. To our knowledge, slope factor (SF), a parameter describing carcinogenicity potential used especially for human risk assessment of contaminated sites, has never been modeled for both inhalation and oral exposures. In this study, we developed classification and regression models for inhalation and oral SFs using data from the Risk Assessment Information System (RAIS) and different machine learning approaches. The models performed well in classification, with accuracies for the external set of 0.76 and 0.74 for oral and inhalation exposure, respectively, and r² values of 0.57 and 0.65 in the regression models for oral and inhalation SFs in external validation. These models might therefore support regulators in (de)prioritizing substances for regulatory action and in weighing evidence in the context of chemical safety assessments. Moreover, these models are implemented on the VEGA platform and are now freely downloadable online.     

Geospatial and statistical approaches to nitrate health risk and groundwater quality assessment of an alluvial aquifer in SE Nigeria for drinking and irrigation purposes

In agricultural districts, like Ogbaru in southeastern Nigeria, water supplies are under obvious threats from human activities. Therefore, continuous monitoring and assessment of water quality suitability for drinking, domestic, and irrigation purposes are encouraged to keep check of the effects of water contaminants. In this paper, several quality water assessment tools were integrated to determine the suitability of the groundwater in Ogbaru for drinking and irrigation uses and to assess the ingestion and dermal health risks of nitrate occurrence. The majority of the physicochemical parameters analyzed in this study were within their respective standard limits. However, groundwater quality index classified 52.63% of the groundwaters as excellent water and 47.37% as good water. Overall index of pollution, on the other hand, classified 84.21% as excellent water and 15.79% as acceptable water. The pH ranged from 5.4 to 6.8, indicating that the groundwater is acidic. Most irrigation water quality assessment indices (SAR, Na%, PS, KR, RCO, CAI-1 and 2) revealed that the groundwater samples are suitable for irrigation. However, magnesium hazard and permeability index grouped the majority of the water samples as unsuitable resources for irrigation uses. The nitrate health risk assessment (mean score = 1.371) indicated that children are exposed to higher non-carcinogenic health risk due to ingestion of contaminated groundwater than the other populations. It was observed that 21.05% of the groundwater samples had the highest concentrations of the analyzed chemical species. Multivariate statistical methods (hierarchical cluster analysis and factor analysis) efficiently aided the contaminant source apportionment. Based on the findings of this paper, it is advised that adequate regulatory strategies and water treatment techniques be adopted in the area to protect and sustain the groundwater quality and public health.     

工业过程生态生命周期评价的生态累积耗模型

生态生命周期评价(Eco-LCA)作为常规生命周期评价的拓展,提供了一种对工业过程生态影响及可持续性分析评价的方法.但目前Eco-LCA中尚缺失生态累积耗(ECEC)指标的完整模型.本文探讨了工业过程中自然资源消耗、社会经济投入和环境污染危害三种主要影响因素.通过构建囊括资源、经济、环境三要素的工业过程生态累积耗模型,完善了Eco-LCA方法应用于工业过程可持续分析的理论框架.最后,以此生态累积耗模型对中国原油生产进行了示例性分析讨论.     

Analysis of heat-induced contaminants (acrylamide, chloropropanols and furan) in carbohydrate-rich food

Heat-induced food contaminants have attracted attention of both the scientific community and the public in recent years. The presence of substances considered possibly or probably carcinogenic to humans has triggered an extensive debate on the healthiness of even staple foods. In that respect, acrylamide, furan and chloropropanols are the main substances of concern. Their widespread occurrence in processed food, which concomitantly causes considerable exposure to humans, led either to the setting of maximum limits (for some chloropropanols) or at least the initiation of monitoring programmes in order to put risk assessment on a solid data basis. Acrylamide, furan and chloropropanols are small molecules with physicochemical properties that make their analysis challenging. Their amount in food ranges typically from below the limit of detection to hundreds of micrograms per kilo or even milligrams per kilo. However, a number of recently published scientific reports deal with the analysis of these substances in different kinds of food. The aim of this publication is to give an overview of analytical approaches for the determination of acrylamide, furan and chloropropanols in foodstuffs.     

Evaluation of the possibility of detecting benzenic pollutants by direct spectrophotometry on PDMS solid sorbent

Solid-phase extraction has become one of the most commonly used techniques for preconcentration of analytes from environmental samples. In the standard use of solid sorbent phases the extracted pollutants are subsequently eluted with a suitable organic solvent before chromatographic analysis. An alternative to this procedure is analysis of the adsorbed and concentrated pollutants by direct application of a spectroscopic method (fluorimetry or absorptiometry) to the phase. Although this method cannot be expected to give results as precise as those given by chromatographic methods, it might have valuable applications, particularly for "on site" pollution monitoring. This paper reports an evaluation of the capability of the method for the spectrophotometric detection of BTX (benzene, toluene, xylenes) in aqueous media and in contaminated atmospheres, with polydimethylsiloxane (PDMS) as sorbent. The tests performed, with the estimated detection limits, indicate that the method is relatively simple and easy to operate and sensitive enough for application to the monitoring of pollution both in water and in air in an industrial ambient atmosphere.     

Bayesian linear regression and variable selection for spectroscopic calibration

This paper presents a Bayesian approach to the development of spectroscopic calibration models. By formulating the linear regression in a probabilistic framework, a Bayesian linear regression model is derived, and a specific optimization method, i.e. Bayesian evidence approximation, is utilized to estimate the model “hyper-parameters”. The relation of the proposed approach to the calibration models in the literature is discussed, including ridge regression and Gaussian process model. The Bayesian model may be modified for the calibration of multivariate response variables. Furthermore, a variable selection strategy is implemented within the Bayesian framework, the motivation being that the predictive performance may be improved by selecting a subset of the most informative spectral variables. The Bayesian calibration models are applied to two spectroscopic data sets, and they demonstrate improved prediction results in comparison with the benchmark method of partial least squares.     

Analysis of gene expression as a new tool in ecotoxicology and environmental monitoring

Pollution affects biological mechanisms in exposed biota, with adverse effects on tissue, organism and, eventually, entire ecosystem levels. Ecotoxicological biomarkers reflect these pollutant-induced physiological alterations, usually by measuring changes in the activity of specific enzymes, or alterations in hormone or protein levels. New, robust polymerase-chain-reaction (PCR)-based methodologies for quantifying specific messenger-RNA molecules have allowed the development of a new family of biomarkers based on analysis of gene-expression patterns. These gene-expression biomarkers have already been applied to many aspects of risk assessment, from toxicological analyses of new substances to in-field monitoring schemes. We review the fundamentals of these techniques, their application in different environmental surveys, their limitations and the outlook for their use in the future.     

Assessing relative bioactivity of chemical substances using quantitative molecular network topology analysis

Structurally different chemical substances may cause similar systemic effects in mammalian cells. It is therefore necessary to go beyond structural comparisons to quantify similarity in terms of their bioactivities. In this work, we introduce a generic methodology to achieve this on the basis of Network Biology principles and using publicly available molecular network topology information. An implementation of this method, denoted QuantMap, is outlined and applied to antidiabetic drugs, NSAIDs, 17β-estradiol, and 12 substances known to disrupt estrogenic pathways. The similarity of any pair of compounds is derived from topological comparison of intracellular protein networks, directly and indirectly associated with the respective query chemicals, via a straightforward pairwise comparison of ranked proteins. Although output derived from straightforward chemical/structural similarity analysis provided some guidance on bioactivity, QuantMap produced substance interrelationships that align well with reports on their respective perturbation properties. We believe that QuantMap has potential to provide substantial assistance to drug repositioning, pharmacology evaluation, and toxicology risk assessment.     

A preliminary study on the migration mechanism of heavy metals into the vadose zone of soils of a dismissed industrial site

Within the framework of the site assessment of a dismantled steel-making plant area contaminated by Electric Arc Furnace dust (EAF dust), the actual migration of Cr, Cu, As, Cd, Pb, Zn and Ni (contaminants) from an industrial waste layer towards the vadose zone of the underlying soil has been evaluated. The crystalline phases and contaminant abundance of samples of the industrial waste layer and the surrounding soils were analysed, while the release of contaminants was evaluated by leaching tests. Results indicate the migration of pollutants from the industrial waste layer into the subsurface soil, but the high leachability of soil hides its real degree of contamination, with the consequent possibility of underestimating the hazardous characteristics of the actual situation.     

Sampling hazelnuts for aflatoxin: effect of sample size and accept/reject limit on reducing the risk of misclassifying lots

About 100 countries have established regulatory limits for aflatoxin in food and feeds. Because these limits vary widely among regulating countries, the Codex Committee on Food Additives and Contaminants began work in 2004 to harmonize aflatoxin limits and sampling plans for aflatoxin in almonds, pistachios, hazelnuts, and Brazil nuts. Studies were developed to measure the uncertainty and distribution among replicated sample aflatoxin test results taken from aflatoxin-contaminated treenut lots. The uncertainty and distribution information is used to develop a model that can evaluate the performance (risk of misclassifying lots) of aflatoxin sampling plan designs for treenuts. Once the performance of aflatoxin sampling plans can be predicted, they can be designed to reduce the risks of misclassifying lots traded in either the domestic or export markets. A method was developed to evaluate the performance of sampling plans designed to detect aflatoxin in hazelnuts lots. Twenty hazelnut lots with varying levels of contamination were sampled according to an experimental protocol where 16 test samples were taken from each lot. The observed aflatoxin distribution among the 16 aflatoxin sample test results was compared to lognormal, compound gamma, and negative binomial distributions. The negative binomial distribution was selected to model aflatoxin distribution among sample test results because it gave acceptable fits to observed distributions among sample test results taken from a wide range of lot concentrations. Using the negative binomial distribution, computer models were developed to calculate operating characteristic curves for specific aflatoxin sampling plan designs. The effect of sample size and accept/reject limits on the chances of rejecting good lots (sellers' risk) and accepting bad lots (buyers' risk) was demonstrated for various sampling plan designs.