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At least 1,459 records · Page 81Linked to original sources

PubMed2005

Surgical treatment of large contaminated abdominal wall defects.

BACKGROUND: Repair of a large, severely contaminated abdominal wall defect is a challenging problem. Most patients are currently treated with a multistaged procedure, which is time consuming, carries a high complication rate, and is often not finalized. STUDY DESIGN: In this study, our experience with a one-stage repair of contaminated abdominal wall defects using the Components Separation Method was evaluated with respect to morbidity and recurrence. Medical records of patients with contaminated abdominal wall defects, treated with the Components Separation Method from 1996 to 2000, were studied. Patients were invited to visit the outpatient clinic for a physical examination. RESULTS: Twenty-six patients with a median age of 49 years and a mean defect size of 267 cm2 were treated. Intraoperative contamination, graded according to the National Research Council (NRC), showed 22 National Research Council III patients and 4 National Research Council IV patients. Postoperatively, five superficial wound infections, three cases of pneumonia, three instances of recurrent enterocutaneous fistulation, and two cases of sepsis were observed. One of the patients with sepsis died after anastomotic disruption led to peritonitis and multiple organ failure. Two asymptomatic recurrences were diagnosed (8%) after a median followup of 27 months. CONCLUSIONS: Large contaminated abdominal wall hernias can be closed by the Components Separation Method, with a low recurrence rate but considerable morbidity.

Adult↗

PubMed2005

Treating disgust reactions in contamination-based obsessive-compulsive disorder.

Contamination fear associated with obsessive-compulsive disorder (OCD) has features that strongly suggest it is based in part on disgust. In particular, sympathetic magic, or the tendency for disgust-evoking stimuli to transfer that property to previously neutral stimuli, is common in contamination fear. Treatment for OCD typically involves exposure with response prevention for feared stimuli. Unexamined, however, has been the habituation for specific disgust stimuli among individuals with contamination fear. This study is a preliminary investigation with a group of primary contamination fearful participants diagnosed with OCD (C-OC; n = 9) compared to a group with primarily other symptoms of OCD (O-OC; n = 8). All participants were exposed to a set of disgust stimuli that were not associated with anxiety reactions for 30 min across five sessions, and exposed to anxiety-evoking stimuli specific to their OCD symptoms for 30 min. Comparisons showed that, while both groups had reduced disgust reactions, the C-OC group habituated more slowly and to a lesser degree than the O-OC group. No differences existed between the groups for anxiety reduction. The findings suggest that contamination fear is based in part on disgust reactions, and that disgust is amenable to exposure-based interventions.

Adult↗

PubMed2005

Contamination by larger particles of two almost-uniform latices: analysis by combined dynamic light scattering and turbidimetry.

Multiangle dynamic light scattering (MDLS) and turbidimetry (T) were applied (both individually and combined) for determining the contamination by larger particles of two almost-uniform polystyrene (PS) latices. Latex 1 was synthesized in our laboratories, and it contained a main population diameter of 340 nm together with a small fraction of larger particles. This latex was used as the base material for producing an immunoassay kit. Latex 2 was obtained by a simple blend of two uniform PS standards. The proposed data treatment calculates the diameter and number fraction of the large particles contamination assuming that the PSDs are bimodal. The calculation involves minimizing the errors between the measurements and their theoretical predictions. When analyzed by combined MDLS-T, the contamination of Latex 1 involved number fraction 0.6% and particle diameter 865 nm. The T average diameter is a function of the measurement wavelength, and the highest deviations of this average to an increasing contamination by large particles were always observed at the higher wavelengths. The DLS average diameter is a function of the measurement angle, but in this case it is impossible to determine a priori the angle of observation that provides the largest deviation of this average diameter to an increasing contamination.

Journal Article↗

PubMed2004

Quantification of groundwater contamination in an urban area using integral pumping tests.

In this paper, the integral groundwater investigation method is used for the quantification of PCE and TCE mass flow rates at an industrialized urban area in Linz, Austria. In this approach, pumping wells positioned along control planes perpendicular to the groundwater flow direction are operated for a time period on the order of days and sampled for contaminants. The concentration time series of the contaminants measured during operation of the pumping wells are then used to determine contaminant mass flow rates, mean concentrations and the plume shapes and positions at the control planes. The three control planes used in Linz were positioned downstream of a number of potential source zones, which are distributed over the field site. By use of the integral investigation method, it was possible to identify active contaminant sources, quantify the individual source strength in terms of mass flow rates at the control planes and estimate the contaminant plume position relative to the control planes. The source zones emitting the highest PCE and TCE mass flow rates could be determined, representing the areas where additional investigation and remediation activities will be needed. Additionally, large parts of the area investigated could be excluded from further investigation and remediation activities.

Austria↗

PubMed2005

Contamination potential of nitrogen compounds in the heterogeneous aquifers of the Choushui River alluvial fan, Taiwan.

This study aimed to analyze the contamination potential associated with the reactive transport of nitrate-N and ammonium-N in the Choushui River alluvial fan, Taiwan and to evaluate a risk region in developing a groundwater protection policy in 2021. In this area, an aquifer redox sequence provided a good understanding of the spatial distributions of nitrate-N and ammonium-N and of aerobic and anaerobic environments. Equiprobable hydraulic conductivity (K) fields reproduced by geostatistical methods characterized the spatial uncertainty of contaminant transport in the heterogeneous aquifer. Nitrogen contamination potential fronts for high and low threshold concentrations based on a 95% risk probability were used to assess different levels of risk. The simulated result reveals that the spatial uncertainty of highly heterogeneous K fields governs the contamination potential assessment of the nitrogen compounds along the regional flow directions. The contamination potential of nitrate-N is more uncertain than that for ammonium-N. The high nitrate-N concentrations (> or =3 mg/L) are prevalent in the aerobic environment. The low concentration nitrate-N plumes (0.5-3 mg/L) gradually migrate to the mid-fan area and to a maximum distance of 15 km from the aerobic region. The nitrate-N plumes pose a potential human health risk in the aerobic and anaerobic environments. The ammonium-N plumes remain stably confined to the distal-fan and partial mid-fan areas.

Environmental Monitoring↗

PubMed2005

Modeling and interpreting bioavailability of organic contaminant mixtures in subsurface environments.

Bioavailability often controls the fate of organic contaminants in surface and subsurface aquatic environments. Bioavailability can be limited by sorption, mass transfer, and intrinsic biodegradation potential and can be further altered by the presence of other compounds. This paper reviews current perspectives on the processes influencing subsurface contaminant bioavailability, how these processes are modeled, and how the relative role of the various processes can be assessed through bioavailability indices. Although these processes are increasingly well understood, the use of sophisticated models and indices often are precluded by an inability to estimate the many parameters that are associated with complex models. Nonetheless, the proper representation of sorption, mass transfer, biodegradation, and co-solute effects can be critical in predicting bio-attenuation. The influence of these processes on contaminant fate is illustrated with numerical simulations for the simultaneous degradation of toluene (growth substrate) and trichloroethylene (nongrowth cometabolite) in hypothetical, aerobic, solid-water systems. The results show how the relative impacts on contaminant fate of the model's various component processes depends upon system conditions, including co-solute concentrations. Slow biodegradation rates increase the inhibition effects of a cometabolite and suppress the rate enhancement effects of a growth substrate. Irrespective of co-solute effects, contaminant fate is less sensitive to biodegradation processes in systems with strong sorption and slow desorption rates. Bioavailability indices can be used to relate these findings and to help identify appropriate modeling simplifications. In general, however, there remains a need to redefine such indices in order that bioavailability concepts can be better incorporated into site characterization, remediation design, and regulatory oversight.

Absorption↗

PubMed2006

Modelling of iron cycling and its impact on the electron balance at a petroleum hydrocarbon contaminated site in Hnevice, Czech Republic.

Over a period of several decades multiple leaks of large volumes from storage facilities located near Hnevice (Czech Republic) have caused the underlying Quaternary aquifer to be severely contaminated with nonaqueous phase liquid (NAPL) petroleum hydrocarbons. Beginning in the late 1980's the NAPL plume started to shrink as a consequence of NAPL dissolution exceeding replenishment and due to active remediation. The subsurface was classified geochemically into four different zones, (i) a contaminant-free zone never occupied by NAPL or dissolved contaminants, (ii) a re-oxidation zone formerly occupied by NAPL, (iii) a zone currently occupied by NAPL, and (iv) a lower fringe zone between the overlying NAPL and the deeper underlying contaminant-free zone. The study investigated the spatial and temporal variability of the redox zonation at the Hnevice site and quantified the influence of iron-cycling on the overall electron balance. As a first step inverse geochemical modelling was carried out to identify possible reaction models and mass transfer processes. In a subsequent step, two-dimensional (forward) multi-component reactive transport modelling was performed to evaluate and quantify the major processes that control the geochemical evolution at the site. The study explains the observed enrichment of the lower fringe zone with ferrihydrite as a result of the re-oxidation of ferrous iron. It suggests that once the NAPL zone started to shrink the dissolution of previously formed siderite and FeS by oxygen and nitrate consumed a significant part of the oxidation capacity for a considerable time period and therefore limited the penetration of electron acceptors into the NAPL contaminated zone.

Biodegradation, Environmental↗

PubMed2006

Comment on "Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume" by Allelign Zeru and Gerhard Schäfer.

We consider the results of a recent paper in this journal [Zeru, A. and Schäfer, G., 2005. Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume. Journal of Contaminant Hydrology 81 (2005) 106-124], which addresses the field-scale characterisation of contaminant plumes in groundwater. There, it is concluded that contaminant concentration gradients can bias Integral Pumping Test (IPT) interpretations considerably, in particular if IPTs are conducted in advective fronts of contaminant plumes. We discuss implications of this setting and also argue that the longitudinal and transverse dispersivities used in the examples of Zeru and Schäfer (2005) of up to 30 m and 3 m, respectively, are generally very high for the here relevant capture zone scale (<20 m). However, regardless of both longitudinal and transverse concentration gradients, we further show through a counter-example that IPT results are unbiased as long as the concentration attenuation along the flow direction is linear over the capture zone extent.

Bias↗

PubMed2004

Bioremediation of soils contaminated with explosives.

The large-scale industrial production and processing of munitions such as 2,4,6-trinitrotoluene (TNT) over the past 100 years led to the disposal of wastes containing explosives and nitrated organic by-products into the environment. In the US, the Army alone has estimated that over 1.2 million tons of soil have been contaminated with explosives, and the impact of explosives contamination in other countries is of similar magnitude. In recent years, growing concern about the health and ecological threats posed by man-made chemicals have led to studies of the toxicology of explosives, which have identified toxic and mutagenic effects of the common military explosives and their transformation products (Bruns-Nagel et al., 1999a; Fuchs et al., 2001; Homma-Takeda et al., 2002; Honeycutt et al., 1996; Rosenblatt et al., 1991; Spanggord et al., 1982; Tan et al., 1992 and Won et al., 1976). Because the cleanup of areas contaminated by explosives is now mandated because of public health concerns, considerable effort has been invested in finding economical remediation technologies. Biological treatment processes are often considered, since these are usually the least expensive means of destroying organic pollution. This review examines the most important groups of chemicals that must be treated at sites contaminated by explosives processing, the chemical and biological transformations they undergo, and commercial processes developed to exploit these transformations for treatment of contaminated soil. We critically examine about 150 papers on the topic, including approximately 60 published within the past 5 years.

Biodegradation, Environmental↗

PubMed2004

Spatial assessment of the economic feasibility of short rotation coppice on radioactively contaminated land in Belarus, Ukraine, and Russia. I. Model description and scenario analysis.

The economic feasibility of short rotation coppice (SRC) production and energy conversion in areas contaminated by Chernobyl-derived (137)Cs was evaluated taking the spatial variability of environmental conditions into account. Two sequential GIS-embedded submodels were developed for a spatial assessment, which allow for spatial variation in soil contamination, soil type, and land use. These models were applied for four SRC production and four energy conversion scenarios for the entire contaminated area of Ukraine, Belarus, and Russia and for a part of the Bragin district, Belarus. It was concluded that in general medium-scale SRC production using local machines is most profitable. The areas near Chernobyl are not suitable for SRC production since the contamination levels in SRC wood exceed the intervention limit. Large scale SRC production is not profitable in areas where dry and sandy soils predominate. If the soil contamination does not exceed the intervention limit and sufficient SRC wood is available, all energy conversion scenarios are profitable.

Bioelectric Energy Sources↗

PubMed2006

An integrated fuzzy-stochastic modeling approach for risk assessment of groundwater contamination.

An integrated fuzzy-stochastic risk assessment (IFSRA) approach was developed in this study to systematically quantify both probabilistic and fuzzy uncertainties associated with site conditions, environmental guidelines, and health impact criteria. The contaminant concentrations in groundwater predicted from a numerical model were associated with probabilistic uncertainties due to the randomness in modeling input parameters, while the consequences of contaminant concentrations violating relevant environmental quality guidelines and health evaluation criteria were linked with fuzzy uncertainties. The contaminant of interest in this study was xylene. The environmental quality guideline was divided into three different strictness categories: "loose", "medium" and "strict". The environmental-guideline-based risk (ER) and health risk (HR) due to xylene ingestion were systematically examined to obtain the general risk levels through a fuzzy rule base. The ER and HR risk levels were divided into five categories of "low", "low-to-medium", "medium", "medium-to-high" and "high", respectively. The general risk levels included six categories ranging from "low" to "very high". The fuzzy membership functions of the related fuzzy events and the fuzzy rule base were established based on a questionnaire survey. Thus the IFSRA integrated fuzzy logic, expert involvement, and stochastic simulation within a general framework. The robustness of the modeling processes was enhanced through the effective reflection of the two types of uncertainties as compared with the conventional risk assessment approaches. The developed IFSRA was applied to a petroleum-contaminated groundwater system in western Canada. Three scenarios with different environmental quality guidelines were analyzed, and reasonable results were obtained. The risk assessment approach developed in this study offers a unique tool for systematically quantifying various uncertainties in contaminated site management, and it also provides more realistic support for remediation-related decisions.

Fuzzy Logic↗

PubMed2005

A prognostic estimation of the area contaminated with alpha-emitting transuranium isotopes in Belarus following the Chernobyl accident.

As a result of the Chernobyl accident, some regions of Belarus have been contaminated with the plutonium isotopes (238,239,240,241)Pu. Considering the importance of the environmental impact of the alpha-emitting radionuclides we have carried out a prognostic estimation of the area contaminated with (238,239,240)Pu and (241)Am (the latter being a decay product of (241)Pu) in Belarus. The calculations were made using measurements of (238,239,240)Pu activity concentrations in soil samples from about 600 settlements in the affected region, together with the estimated activity ratio A((241)Am)/A((238,239,240)Pu). The area contaminated with alpha-emitting transuranium isotopes predicted for the year 2006 has been compared with that estimated for 1986. The results show that by 2006, the area of inhabited districts where contamination with (238,239,240)Pu and (241)Am exceeds the threshold level of 740 Bq/m(2), will be 3.7 times larger, reaching approximately 3.5 x10(3)km(2). Of this, almost 20% will have a contamination level of 1850--3700 Bq/m(2).

Americium↗

PubMed2005

Screening plant species native to Taiwan for remediation of 137Cs-contaminated soil and the effects of K addition and soil amendment on the transfer of 137Cs from soil to plants.

This study aims to screen plant species native to Taiwan that could be used to eliminate (137)Cs radionuclides from contaminated soil. Four kinds of vegetables and two kinds of plants known as green manures were used for the screening. The test plants were cultivated in (137)Cs-contaminated soil and amended soil which is a mixture of the contaminated one with a horticultural soil. The plant with the highest (137)Cs transfer factor was used for further examination on the effects of K addition on the transfer of (137)Cs from the soils to the plant. Experimental results revealed that plants cultivated in the amended soil produced more biomass than those in the contaminated soil. Rape exhibited the highest production of aboveground parts, and had the highest (137)Cs transfer factor among all the tested plants. The transfer of (137)Cs to the rape grown in the soil to which 100 ppm KCl commonly used in local fertilizers had been added, were restrained. Results of this study indicated that rape, a popular green manure in Taiwan, could remedy (137)Cs-contaminated soil.

Biodegradation, Environmental↗

PubMed2005

Weather-dependent change of cesium, strontium, barium and tellurium contamination deposited as aerosols on various cultures.

Various types of plants (wheat, bean, lettuce, radish and grass) were contaminated by dry deposition of radioactive aerosols ((137)Cs, (85)Sr, (133)Ba and (123 m)Te) in order to supplement the radio-ecological data necessary for operational post-accidental codes. A few days after deposition, rainfalls were applied to these cultures to evaluate the influence of some characteristics of the rain on the contamination of the culture over time. On the other hand, for wheat and bean, the influence of the humidity condition of the foliage at the contamination time was considered. For a given plant species at a given vegetative stage, the four radionuclides were intercepted in an identical way. The interception varied from 30% for bean (young sprout) to 80% for lettuce (near maturity). The global transfer factor values were dependent on both the radionuclides and the plant species; nevertheless, a higher value was obtained for cesium, regardless of the plant and the rainfall (from 0.006 m(2)kg(fresh)(-1) for wheat-grains - contaminated at the shooting stage - or for bean-pods - contaminated at the pre-flowering stage - to 0.1m(2)kg(fresh)(-1) for a whole lettuce). The analysis of the results allowed us on the one hand, to extract parameter values of the foliar transfer directly usable in operational codes, in particular those relating to barium and tellurium, unknown until then, and on the other hand, to lay the foundations of a future, more mechanistic model, taking into account the foliar processes in a finer way.

Aerosols↗

PubMed2006

Patterns and inventories of radioactive contamination of island sites of the Yenisey River, Russia.

The distribution of radioactive contamination at three island sites downstream from the Krasnoyarsk Mining and Chemical Combine (KMCC) was studied with the objectives of mapping contamination levels, interpreting radionuclide distributions through consideration of alluvial processes and determining radionuclide inventories. Contamination was measured using in situ gamma spectrometry and landforms characterised using topographic surveying methods. Maximum (137)Cs contamination densities (700 kBq m(-2)) were found on low- and middle-level floodplains and low-lying interconnecting areas of Beriozovy Island (16 km from the KMCC). On Mikhin Island (180 km from the KMCC) maximum total (60)Co, (152)Eu and (154)Eu activity concentrations (30-40 kBq m(-2)) occur in low-lying areas inundated during flooding. Maximum (137)Cs and total (60)Co, (152)Eu and (154)Eu contamination densities on Cheriomukhov Island (250 km from the KMCC) were 390 and 50 kBq m(-2), respectively. Estimated (137)Cs inventories were 145, 148 and 16GBq for Beriozovy, Mikhin and Cheriomukhov Islands, respectively.

Cesium Radioisotopes↗

PubMed2006

Assessment of state-of-the-art models for predicting the remobilisation of radionuclides following the flooding of heavily contaminated areas: the case of Pripyat River floodplain.

The performances of models are assessed to predict the wash-off of radionuclides from contaminated flooded areas. This process should be accounted for in the proper management of the aftermath of a nuclear accident. The contamination of the Pripyat River water following the inundation of a floodplain heavily contaminated by (90)Sr and (137)Cs of Chernobyl origin is used as the basis for modelling. The available experimental evidence demonstrated that remobilisation of radiostrontium is an important process implying a significant secondary radioactive load of water flowing over the contaminated floodplain. On the contrary, there is no empirical evidence of a similar behaviour for radiocaesium. In general, state-of-the-art models properly predicted the remobilisation of strontium, whereas they significantly overestimated radiocaesium concentrations in water. The necessary model improvements for a more accurate prediction of radiocaesium contamination levels include a reassessment of the values of the model parameters controlling the remobilisation process.

Cesium Radioisotopes↗

PubMed2003

Dielectric dispersion characteristics of sand contaminated by heavy metal, landfill leachate and BTEX (02-104B).

Experiments have been performed to investigate the dielectric properties of contaminated sand. The separate real and imaginary parts of a dielectric constant were investigated in the frequency range of 75 kHz to 12 MHz. The contaminated soils exhibit different complex dielectric dispersion from the uncontaminated soils. The variation in the real dielectric constant can be explained by a polarization mechanism while that in the imaginary dielectric constant by ionic conductivity loss mechanism. The differences of the dielectric behavior with contaminant types suggest that the monitoring of complex dielectric constant has the potential to classify contaminants. The additional analysis for the imaginary part of the dielectric constant can be recommended to obtain the clear information about the state of ionic contaminants in subsurface.

Benzene↗

PubMed2006

Use of cement and quicklime to accelerate ripening and immobilize contaminated dredging sludge.

In this study cement and quicklime are examined as binders to enhance the ripening process and immobilize contaminants in dredging sludge. Ripening comprises the drying in the open air till a dry matter content of 50-55% is reached. For this study, a dredging sludge of the highest contamination category was used. The binders speed up the ripening process substantially since the binders as such increase the dry matter content upon mixing, but they also modify the structure so that evaporation is facilitated. Furthermore, the reaction of cement and quicklime with water generates heat that also stimulates evaporation, and both binders, in combination with dredging sludge, bind water chemically (twice as much as expected). The total time for ripening could be reduced by 70%, which means that existing treatment depots can be used more effectively. The emission of contaminants was determined by a standard leaching test. The cement and quicklime had opposite effects on the leaching of constituents. The addition of cement had negative effects on sulphate, fluoride, and zinc, which were compensated by the addition of quicklime. On the other hand, cement reduced the emission of chloride, copper, and nickel, while quicklime seemed to increase the emission of these constituents. The concentration and emission of contaminants of the treated dredging sludge meet the requirements of the current legislation. It is therefore concluded that the presented method is able to produce, in a much shorter time, an applicable building material from contaminated dredging sludge.

Calcium Compounds↗