Fate and transport of 1278-TCDD, 1378-TCDD, and 1478-TCDD in soil-water systems

The most toxic dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD), and obtaining comprehensive experimental data for this compound is challenging. However, several nontoxic isomers of 2378-TCDD exist, and can provide significant experimental evidence about this highly toxic dioxin. The goal of this study was to obtain experimental evidence for the fate and transport of 2378-TCDD in natural soils using its nontoxic isomers, 1,2,7,8-tetrachlorodibenzo-p-dioxin (1278-TCDD), 1,3,7,8-tetrachlorodibenzo-p-dioxin (1378-TCDD), and 1,4,7,8-tetrachlorodibenzo-p-dioxin (1478-TCDD). Batch sorption and miscible-displacement experiments, in various soils, were done using [4-(14)C]-radiolabeled TCDDs, while metabolism of these compounds was monitored. The results from the batch experiments indicated a high sorption affinity of all the TCDD isomers to soils and a strong correlation to organic matter (OM) content. 1278-TCDD, 1378-TCDD and 1478-TCDD (TCDDs) were more tightly bound to the soil with high OM than to the soil with low OM; however, it took a longer contact time to approach sorption equilibrium of TCDDs in the soil with high OM. Miscible-displacement breakthrough curves indicated chemical nonequilibrium transport, where there was a rate-limited or kinetic sorption that was likely caused by OM. Combustion analyses of extracted soil from the soil columns showed that most TCDDs were adsorbed in the top 1-5 cm of the column. These column combustion results also showed that sorption was correlated to specific surface and soil depth, which suggested the possibility of colloidal transport.     

A pharmacokinetic model for estimating exposure of Americans to dioxin-like compounds in the past,present, and future

Empirical evidence suggests that exposure of Americans to dioxin-like compounds was low during the early decades of the 20th century, then increased during the 1940s and 1950s, reaching a peak in the 1960s and 1970s, and progressively decreased to lower levels in the 1980s and 1990s. Such evidence includes dioxin analysis of carbon-dated sediment cores of lakes and rivers, preserved meat samples from different decades of the 20th century, and limited body burden measurements of dioxin-like compounds. Pinsky and Lorber (1998) summarized studies measuring 2,3,7,8-TCDD in blood and adipose tissue, and found a range of 10-20 pg/g (ppt) lipid during the 1970s, and 2-10 ppt lipid during the 1980s. This study reviews body burdens of dioxin toxic equivalents, TEQs, to find a range from approximately 50 to 80 ppt lipid during the 1970s, 30-50 ppt lipid during the 1980s, and 10-20 ppt lipid during the 1990s (TEQs comprised of the 17 dioxin and furan congeners only). Pinsky and Lorber (1998) investigated historical exposure trends for 2,3,7,8-TCDD by using a single-compartment, first-order pharmacokinetic model. The current study extends this prior effort by modeling dioxin TEQs instead of the single compound, 2,3,7,8-TCDD. TEQs are modeled as though they were a single compound, in contrast to an approach where the individual dioxin and furan congeners are modeled separately. It was found that body burdens of TEQs during the 1970s, 1980s and 1990s could be modeled by assuming a historical dose which began the century at low levels of approximately 0.5 pg TEQ/kg/day, rose during the middle decades of the 20th century to over 6 pg TEQ/kg/day, and declined to current levels of approximately 0.5 pg TEQ/kg/day. Trends in individual and population body burdens of TEQs are also investigated using this PK modeling framework. A key uncertainty of this effort - assuming that TEQs behave as though they were a single compound - is discussed and analyzed.     

Standard Reference Materials for dioxins and other environmental pollutants

The National Institute of Standards and Technology issues approximately 1100 Standard Reference Materials (SRMs) certified for chemical composition or physical properties. A number of these SRMs has been developed to assist chemists in analyzing environmental samples more reliably for chlorinated dioxins and other organic pollutants. Certification of the pollutant concentration in a natural matrix SRM is based on concordant analyses by the NIST Organic Analytical Research Division using at least two independent methods. For a calibration solution, such as SRM 1614, Dioxin (2,3,7,8-TCDD) in Isooctane, certification is based on agreement of the calculated concentration based on the gravimetric preparation and the concentration as determined experimentally. SRM 1614 also includes a 13C-labeled 2,3,7,8-TCDD for use as an internal standard in methods based on gas chromatography/mass spectrometry. The certified concentrations (ng g-1) are 98.3 +/- 3.3 for the unlabeled dioxin and 95.6 +/- 1.5 for the labeled dioxin. The certificates for SRM 1588, Organics in Cod Liver Oil, and SRM 1589, Polychlorinated Biphenyls (as Aroclor 1260) in Human Serum, provide noncertified concentrations of dioxins. Concentrations of chlorinated dioxins in two urban particulate SRMs have been reported in the literature.     

Consumption patterns and risk assessment of crab consumers from the Newark Bay Complex, New Jersey, USA

The Newark Bay Complex (NBC) is a significant historical repository of polychlorinated dibenzodioxins (PCDDs) and dioxin-like compounds. Detection of high levels of 2,3,7,8 tetrachloro-dibenzodioxins (TCDD) and its toxicological equivalents in blue crabs in the early 1990's led to a ban on the taking and distribution of crabs from the NBC. Despite this ban and ongoing communication outreach, surveys of crabbers in 1995, 2002 and 2005 by the New Jersey Department of Environmental Protection (NJDEP) showed that crabbing for recreational purposes and for significant dietary supplementation was continuing. At the time they were surveyed, the crabbers had been consuming these crabs for an average of 37% of their lives. Thus, exposure can be considered chronic. The surveys provided data on the duration, frequency and amount of NBC crab consumption. In 2004, the NJDEP sampled blue crabs in the NBC and analyzed the edible portions for 2,3,7,8 TCDD toxicity equivalent (TEQ) concentration. We have combined the survey-based exposure data and the 2,3,7,8 TCDD TEQ concentration data to produce an estimate of the lifetime cancer risk to NBC crabbers from dioxin-like compounds. We employed a point-estimate approach using discrete lower, central tendency and reasonable maximum exposure (RME) estimates of exposure factors and a probabilistic approach to exposure factors. Both approaches show central tendency lifetime cancer risk of greater than one-in-a-thousand (10⁻³) and an upper percentile/RME risk of approximately one-in-a-hundred (10⁻²). Little extrapolation is involved in applying the 2,3,7,8-TCDD TEQ concentration data in crabs to risk estimates in the population consuming those crabs. The ongoing and frequent nature of the crab collection minimizes the uncertainty often inherent in food recall surveys. These estimates point to the continued risk posed to NBC crab consumers and to the continuing importance of this resource which, with proper remediation, could provide ongoing benefit to the surrounding community.     

原代培养细胞法测试水中类二噁英物质

采用固相萃取方法对北方某水厂水源水和各处理工艺出水进行富集,对各提取物采用草鱼原代培养肝细胞的7-乙氧基异吩唑酮-脱乙基酶(EROD)体外测试方法进行了类二口恶英物质的检验。结果表明,该水厂水源水和各处理工艺出水中,类二噁英物质浓度相当于0.20～0.50pg/L的2,3,7,8-TCDD(2,3,7,8-四氯代二苯并二噁英)当量,出水TCDD当量远远低于美国环保局饮用水二噁英类化合物含量标准(30pg/L)。研究表明,水样的固相萃取前处理方法结合原代培养细胞EROD分析,可以快速、有效地筛选和定量分析水样中未知的具有EROD效应的物质及其总体效应。     

Probabilistic simulation for developing likelihood distribution of engineering project cost

Inaccurate early project cost estimates can eliminate investment benefits. This study focuses on assisting estimators who are attempting to enhance the accuracy and reliability of engineering project cost in the pre-conceptual stage. This aim has recently garnered the attention of the transportation communities. Data from the Texas Department of Transportation (TxDOT) were utilized to develop an alternative approach that aids decision makers in terms of probability and confidence level. The proposed procedure comprises heuristic and practical simulation models that can be employed to calculate the probabilistic costs of highway bridge replacement projects. The simulation models utilize independent, correlated, and Latin Hypercube sampling approaches that incorporate major work items, roll-up work items, and project-level engineering contingencies. Cumulative distribution functions (CDFs) are then developed as a user-friendly chart for decision makers and these CDFs can be used to assess project risks during the pre-conceptual stage. Trial runs using these estimating procedures generate reliable pre-conceptual estimates. Additionally, these procedures can be extended to other project types along with programming techniques for developing an engineering project cost decision support system.     

Characterization of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere of different workplaces of a sinter plant

This study investigated concentrations, contents and congener profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the workplaces of a sintering plant. Air samples were collected from the charging zone, the sintering zones of the sintering grate and the rough roll shredder, and the control room. The charging zone was found to have a higher total suspended particulate (TSP) but lower PCDD/F concentrations (=4969 microg nm(-3) and 7.61 pg nm(-3), respectively) than the sintering zone (=1422-1448 microg nm(-3) and 19.16-23.17 pg nm(-3), respectively). The TSP and PCDD/F concentrations were lowest in the control room (=98 microg nm(-3) and 1.75 pg nm(-3), respectively). However, the above concentrations were within the range of a typical urban-industrial area. Quite similar PCDD/F contents were found in particles in the sintering zones and control room (=11.72-14.30 and 15.85 ng g(-1), respectively) suggesting that the sintering zone and the control room are very similar. In both charging and sintering zones, 2,3,4,7,8-PeCDF contributed 40-60% to the total I-TEQ in both the gas phase and particle phase. However, in control room, both congeners 2,3,4,7,8-PeCDF and 2,3,7,8-TCDD were the main contributors; the later contributed 30% of the total I-TEQ in gas phase. In control room, the contribution of 2,3,7,8-TCDD to the total PCDD/F concentration in the gas phase greatly exceeded that in particle phase (=5.5% and 0.8%, respectively). Therefore, solutions must be sought to avoid the transfer of not only the particle-phase but also the gas-phase PCDD/Fs from the sintering zone to the control room in the future.     

PCB, PCDD and PCDF residues in fin and non-fin fish products from the Canadian retail market 2002

Fish products (n=129) available on the Canadian retail market were collected and analyzed for levels of PCBs, PCDDs and PCDFs during the spring of 2002. The collection included samples from eight fish groups (Arctic char, crab, mussels, oysters, salmon, shrimp, tilapia, trout) from the wild and those raised on fish farms, as available. Sample collection included both domestic and imported fish products, however, no significant difference in residue levels was observed between these groups of fish products. Salmon samples were found to contain the highest concentration of sigmaPCBs (geometric mean 12.9 ng/g wet weight), while crab samples had greatest sigmaPCDD/F levels (geometric mean 0.002 ng/g wet weight). The geometric mean of the total toxic equivalents (WHO-TEQ) ranged from 0.06 pg WHO-TEQ/g whole weight in farmed shrimp to 1.1 pg WHO-TEQ/g whole weight in farmed salmon samples. PCB 153, 138, 118 and 101 were the dominant congeners observed in fish product samples studied, while 1,2,3,7,8-pentachlorodibenzodioxin and 2,3,7,8-tetrachlorodibenzofuran contributed the most to total PCDD and PCDF loadings. Lipid content was positively correlated to sigmaPCB levels; however, no relationship between lipid content and sigmaPCDD/F concentrations was established. SigmaPCB levels were below the Canadian guideline value for PCBs in fish and fish products (2000 ng/g). Similarly, 2,3,7,8-TCDD levels in all fish products were below the Canadian guideline value (0.020 ng/g).     

Calibrated methodology for assessing climate change adaptation costs for urban drainage systems

Changes in precipitation patterns associated with climate change may pose significant challenges for storm water management systems across the U.S. In particular, adapting these systems to more intense rainfall events will require significant investment, though no method currently exists for estimating the costs of these investments on a national scale. To support assessment of these costs at the national level, this paper presents a reduced-form approach for estimating changes in normalized flood depth (the volume of node flooding normalized by the area of the catchment) and the associated costs of flood prevention. This reduced form approach is calibrated to results generated by the U.S. Environmental Protection Agency's Storm Water Management Model (SWMM) for city-wide or neighborhood-level catchments in seven cities across the U.S. Estimates derived from this approach represent a reasonable approximation of storm water management adaptation costs and exhibit no systematic bias relative to results derived from SWMM.     

Assessing regional intake fractions in North America

This paper develops the IMPACT North America model, a spatially resolved multimedia, multi-pathway, fate, exposure and effect model that includes indoor and urban compartments. IMPACT North America allows geographic differentiation of population exposure of toxic emissions for comparative risk assessment and life cycle impact assessment within U.S. and Canada. It looks at air, water, soil, sediment and vegetation media, and divides North America into several hundred zones. It is nested within a single world box to account for emissions leaving North America. It is a multi-scale model, covering three different spatial scales — indoor, urban and regional — in all zones in North America. Model results are evaluated against monitored emissions and concentrations of benzo(a)pyrene, 2,3,7,8-TCDD and mercury. Most of the chemical concentrations predicted by the model fall within two orders of magnitude of the monitored data. The model shows that urban intake fractions are one order of magnitude higher than rural intake fractions. The model application and importance is demonstrated by a case study on spatially-distributed emissions over the life cycle of diesel fuel. Depending on population densities and agricultural intensities, intake fractions can vary by eight orders of magnitudes, and even limited indoor emissions can lead to intakes comparable to those from outdoor emissions. To accurately assess these variations in intake fraction, we require the essential three original features described in the present paper: i) inclusion of the continental model within a world box for persistent pollutants, ii) addition of an urban box for short- and medium-lived substances (for grid size larger than 100 km), and iii) assess indoor emissions. This model can therefore be used to screen chemicals and assess regionalized intake fractions within North America for population-based human exposure assessment, life cycle impact assessment, and comparative risk assessment. The model can be downloaded at http://www.impactmodeling.org.     

Progressive collapse of multi-storey buildings due to sudden column loss — Part I: Simplified assessment framework

This paper proposes a novel simplified framework for progressive collapse assessment of multi-storey buildings, considering sudden column loss as a design scenario. The proposed framework offers a practical means for assessing structural robustness at various levels of structural idealisation, and importantly it takes the debate on the factors influencing robustness away from the generalities towards the quantifiable. A major feature of the new approach is its ability to accommodate simplified as well as detailed models of the nonlinear structural response, with the additional benefit of allowing incremental assessment over successive levels of structural idealisation. Three main stages are utilised in the proposed assessment framework, including the determination of the nonlinear static response, dynamic assessment using a novel simplified approach, and ductility assessment. The conceptual clarity of the proposed framework sheds considerable light on the adequacy of commonly advocated measures and indicators of structural robustness, culminating in the proposal of a single rational measure of robustness that is applicable to building structures subject to sudden column loss. The companion paper details the application of the new approach to progressive collapse assessment of real steel-framed composite multi-storey buildings, making in the process important conclusions on the inherent robustness of such structures and the adequacy of current design provisions.     

Project cash flow analysis in the presence of uncertainty in activity duration and cost

The inherent uncertainty and imprecision in project scheduling have motivated the proposal of several fuzzy set theory based extensions of activity network scheduling techniques. Building upon these, a cash flow calculation methodology for projects including activities with fuzzy durations and/or costs is proposed in this paper. According to the proposed approach, the project cash flow is represented by an S-surface (as opposed to the traditional S-curve) ensuing by connecting S-curves at different risk possibility levels. The methodology is exemplified by estimating the working capital requirements in a real world road construction project. Furthermore, the benefits of the methodology and its subsequent computerization are discussed. It is believed that the proposed approach may also be useful for both evaluating project proposals during feasibility studies and for performing earned value analysis for project monitoring and control.     

Incremental wave analysis and its application to performance-based assessment of jacket platforms

In this paper, a relatively novel approach is established to estimate different limit states and accurate behavior of jacket platforms against environmental wave loading. This novel approach which is called Incremental Wave Analysis (IWA) can be an appropriate substitute to current pushover practice. The IWA can take into account the effects of variation in wave height and wave-in-deck loading in the estimating of platforms' behavior. This paper aims to introduce the applications of this approach in deterministic assessment of offshore platforms, comprehensively. The IWA can estimate the collapse-prevention limit state of jacket platforms properly. In addition, an appropriate parameter for ultimate capacity of offshore platforms is introduced which is called Collapse Wave Height (CWH). It is illustrated that the CWH can be utilized as a substitute to RSR parameter in the design and assessment of jacket platforms. Moreover, this novel indicator is able to exceptionally estimate the collapse probability of offshore platforms utilizing a deterministic practice. This is a unique feature that can never be achieved by current pushover method utilizing RSR parameter. The IWA can be carried out using either nonlinear static or dynamic wave analyses. Therefore, in this paper, both Static and Dynamic Incremental Wave Analyses (SIWA and DIWA) will be systematically explained. Before conducting DIWA, some fundamental questions such as importance of dynamic analysis and also proper methodology for conducting dynamic analysis, will be investigated. Comparison between SIWA and DIWA will also bring about worthwhile results which will be discussed thoroughly.     

Fatigue performance assessment and service life prediction of high-speed ship structures based on probabilistic lifetime sea loads

This article focuses on estimating probabilistic lifetime sea loads for high-speed ship structures with the aim of assessing fatigue performance and predicting service life from available data. Performance assessment and service life prediction for naval ship structures are extremely important issues. In particular, understanding the effect of sea loading on naval high-speed vessels is still a challenge. Potential lifetime load effects including low frequency wave-induced and high frequency slam-induced whipping loadings are investigated in this article by using a probabilistic approach. Clearly, integration of probabilistic sea loads into structural reliability assessment and service life prediction will provide a more reliable estimation of the long-term structural performance. Accordingly, this article presents an approach for fatigue reliability evaluation of ship structures based on the estimated lifetime sea loads. Loading information associated with sea states, ship speeds and relative wave headings is obtained from a joint high-speed sealift ship monohull structural seakeeping trials, while the S–N curves are established based on the British Standards.     

基坑工程环境水文地质评价

目前地下水引起的基坑安全及环境风险问题变得越来越严重,为消除或减弱该类.风险,需要进行基坑环境水文地质评价.详细列举了基坑环境水文地质评价的主要内容,即通过分析基坑及其周边的水文地质条件,分析及预测基坑地下水控制引起的环境变化,同时提出基坑工程地下水控制措施的建议,对基坑设计和施工中地下水引起的基坑安全及环境风险控制有...     

Effects of storage height on critical delivered flux of representative fuels

Fire suppression experiments were conducted to determine the critical delivered fluxes (CDFs) of representative fuels. The objective was to evaluate the CDF-based commodity classification for sprinkler protection purposes with emphasis on the effects of storage height. The experiments were carried out in 2- and 5-tier double-row, rack storage configurations, which, together with previous 3-tier work, provide a complete set of CDF measurements at different storage heights. The experimental results show that the 5-tier CDFs correlate well with full-scale sprinkler testing experiences. The comparison of CDFs also reveals the storage height effects for different fuels: the CDF values scale linearly for the cartoned commodities, while nonlinearities are observed for the uncartoned plastic commodities. Based on these results, a commodity classification method is proposed to assess solid combustible materials in the real world with separate treatment of cartoned and uncartoned fuels.     

Hierarchical infrastructure network representation methods for risk-based decision-making

Estimating the extent of hazard-induced damage to infrastructure networks is a complex task that goes beyond computing direct costs and requires considering the effect of network connection patterns and interactions. This article presents a new model that combines a systems approach with strategies for detecting the internal structure of networks, and providing flexibility and different levels of accuracy in estimating the extent of damage. The model describes networks as hierarchical structures obtained by successive clustering. Hierarchical analysis of networks provides unique insights about how damage affects performance throughout the whole infrastructure system. The model enables using information for decision-making more efficiently by generating different levels of resolution for different problems. This is illustrated using data from hurricane Ike, Texas, USA in 2008, where the primary transportation network is studied. Estimates of population affected and loss of productivity are discussed, emphasising the importance of multiple levels for assessment, and their application on fast decision-making for emergency situations.     

Ecological risk assessment of pesticides in the Mediterranean region. The need for crop-specific scenarios

The risk assessment procedures of pesticides in the European Union are mostly based on worst-case scenarios developed for central and northern European conditions. From the point of view of Mediterranean conditions, these assessment procedures are not always appropriate, and therefore the development of specific scenarios is required. There are differences not only in meteorological data (temperature, solar irradiation, or rainfall volume and annual distribution) between these countries, but also in farm distribution, crop characteristics, soil or sediment properties and surface or groundwater characteristics. These differences are more evident for the typical crops of the southern countries, such as olive groves, vineyards, citrus or rice fields, and in these cases more realistic estimates of exposure are required. Our proposal includes the development of new criteria to improve the ecological risk assessment process for the conditions of the Mediterranean region, and the justification of this need.     

Seismic fragility analysis of 3D structures

A statistical approach for time-variant system reliability problems is developed and investigated. The basic proposal is to use a response surface, characterised by a statistical model of the mixed type, to represent the capacity in an analytical limit-state function. The fragility function of the system is then calculated by FORM analysis, with the constructed empirical limit-state function as input. The methodology is applied in the assessment of a 3D RC frame structure. The application allows a number of detailed implementation issues to be clarified, and confirms the robustness and versatility of the method.