Biomedical subjects

E Wirth

Publications and source records attributed to E Wirth.

14 recordsLinked to original sources

PubMed2006

An evaluation of contaminated estuarine sites using sediment quality guidelines and ecological assessment methodologies.

Toxic contaminants may enter estuarine ecosystems through a variety of pathways. When sediment contaminant levels become sufficiently high, they may impact resident biota. One approach to predict sediment-associated toxicity in estuarine ecosystems involves the use of sediment quality guidelines (ERMs, ERLs) and site-specific contaminant chemistry while a second approach utilizes site-specific ecological sampling to assess impacts at the population or community level. The goal of this study was to utilize an integrated approach including chemical contaminant analysis, sediment quality guidelines and grass shrimp population monitoring to evaluate the impact of contaminants from industrial sources. Three impacted sites and one reference site were selected for study. Grass shrimp populations were sampled using a push-netting approach. Sediment samples were collected at each site and analyzed for metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides. Contaminant levels were then compared to sediment quality guidelines. In general, grass shrimp population densities at the sites decreased as the ERM quotients increased. Grass shrimp densities were significantly reduced at the impacted site that had an ERM exceedance for chromium and the highest Mean ERM quotient. Regression analysis indicated that sediment chromium concentrations were negatively correlated with grass shrimp density. Grass shrimp size was reduced at two sites with intermediate levels of contamination. These findings support the use of both sediment quality guidelines and site-specific population monitoring to evaluate the impacts of sediment-associated contaminants in estuarine systems.

Animals↗

PubMed2000

Separation of Tc-99 in soil and plant samples collected around the chernobyl reactor using a Tc-selective chromatographic resin and determination of the nuclide by ICP-MS

Technetium (Tc) is known to have high mobility in a soil-water system and also high bioavailability for plants, because the most stable form of Tc in natural surface environment is thought to be TcO4- which is highly soluble. The chemical form of Tc, however, changes with environmental conditions. Thus, it is necessary, for realistic assessment, to obtain transfer parameters, such as transfer factors, under natural conditions. However, it is difficult to obtain these parameters using global fallout 99Tc in actual fields due to its low concentration. In this study, 99Tc concentrations in surface soil and plant leaf samples collected from forest sites within the 30-km zone around the Chernobyl reactor were measured for the first time. In the case of soil samples, a simple and rapid analytical method for determination of 99Tc is used which consists of volatilizing and trapping Tc in a combustion apparatus, purifying the Tc with an extraction chromatographic resin, and measuring it by inductively coupled plasma mass spectrometry (ICP-MS). For plant samples, a wet digestion method in combination with the resin is applied and the 99Tc is measured by ICP-MS. Concentrations of 99Tc in organic soil samples and leaves of strawberry (Fragaria vesca) range from 1.1-14.8 Bq kg(-1) dry weight and 0.2-6.0 Bq kg(-1) dry weight, respectively. Our results indicate that soil-to-plant transfer factors for Tc are similar to those for Cs.

Journal Article↗

PubMed1999

Determination of 99Tc deposited on the ground within the 30-km zone around the Chernobyl reactor and estimation of 99Tc released into atmosphere by the accident.

Technetium-99 was determined in samples from the 30-km zone around the Chernobyl reactor. Concentrations of 99Tc in soil samples taken from three forest sites ranged from 1.1 to 14.1 Bq kg-1 dry weight for the organic soil layers, and from 0.13 to 0.83 Bq kg-1 dry weight for the mineral soil layers. In particular, for the organic layers, the measured 99Tc concentrations were one or two orders of magnitude higher than those due to global fallout 99Tc. The 99Tc depositions (Bq m-2), based on the sum of the depositions measured in organic and mineral layers, ranged from 130 Bq m-2 within the 10-km zone to about 20 Bq m-2 close to the border of the 30-km zone. Taking the corresponding measured 137Cs depositions into account, it was found that the activity ratio of 99Tc/137Cs ranged from 6 x 10(-5) to 1.2 x 10(-4). It was estimated that about 970 GBq of 99Tc had been released by the Chernobyl accident. This figure corresponded to 2%-3% of the total 99Tc inventory in the core.

Air Pollutants, Radioactive↗

PubMed1999

Comparative study of the PARK and ASTRAL post-accidental decision support software.

The French radioecological assessment model ASTRAL and the German model PARK have been developed to evaluate the radiological situation in the case of an accidental release of radionuclides and a widespread contamination of the environment. For decision makers it is of importance that the results on foodstuff contamination and on dose to humans are in fairly good agreement, when areas of the common border are affected. Therefore a comparative study has been done for two scenarios, assuming accidental releases on 1 June and 1 October. The study indicates that the models' structures and the transfer parameters are in good agreement. Only model principles for root vegetables are different in both models. Significant differences in results on the contamination of foodstuff and on dose to humans by ingestion are caused by different assumptions on dates of harvest and feeding methods of animals. A corresponding harmonization is essential with respect to decision making.

Animal Feed↗

PubMed1997

Characteristics of human fetal spinal cord grafts in the adult rat spinal cord: influences of lesion and grafting conditions.

The present study evaluated the growth potential and differentiation of human fetal spinal cord (FSC) tissue in the injured adult rat spinal cord under different lesion and grafting conditions. Donor tissue at 6-9 weeks of gestational age was obtained through elective abortions and transplanted either immediately into acute resection (solid grafts) or into chronic contusion (suspension and solid grafts) lesions (i.e., 14-40 days after injury) in the thoracic spinal cord. The xenografts were then examined either histologically in plastic sections or immunocytochemically 1-3 months postgrafting. Intraspinal grafts in acute lesions demonstrated an 83% survival rate and developed as well-circumscribed nodules that were predominantly composed of immature astrocytes. Solid-piece grafts in chronic contusion lesions exhibited a 92% survival rate and also developed as nodular masses. These grafts, however, contained many immature neurons 2 months postgrafting. Suspension grafts in chronic contusion lesions had an 85% survival rate and expanded in a nonrestrictive, diffuse pattern. These transplants demonstrated large neuronally rich areas of neural parenchyma. Extensive neuritic outgrowth could also be seen extending from these grafts into the surrounding host spinal cord. These findings show that human FSC tissue reliably survives and differentiates in both acute and chronic lesions. However, both the lesion environment and the grafting techniques can greatly influence the pattern of differentiation and degree of host-graft integration achieved.

Animals↗

PubMed1996

Development of a general equation to determine the transfer factor feed-to-meat for radiocesium on the basis of the body mass of domestic animals.

Transfer factors from feed to meat (T f), taken from literature for monogastric animals and ruminants have been correlated to their corresponding animal body mass (mb). Taking all data into account, a close relationship between both transfer factor and body mass becomes evident, yielding a regression function of T f = 8.0 x mb(-0.91) (r = -0.97). For monogastric animals (including poultry), the corresponding relationships are T f = 5.8 x mb(-0.70) (r = -0.97), for ruminants T f = 1.9 x mb(-0.72) (r = -0.78). The equations offer the opportunity to estimate the transfer factor for individual animals more precisely taking individual body masses into account. They are of interest for animals, on which no or only poor data concerning radiocesium transfer factors are available. The determination of radiocesium transfer factors are reduced to a simple weighing process.

Animals↗

PubMed1985

The suitability of transfer coefficients used for stochastic calculations in radioecology.

In radioecology, stochastic calculations are used to an increasing extent. It is shown that transfer coefficients which are defined as concentration ratios are not suited for stochastic calculations, at least for essential elements and their antagonists. The reason is that essential elements are regulated in plants and animals whereby their concentrations vary within narrow limits, rather independent of the concentrations in the source compartment. For a more accurate description of the transfer of radionuclides, it is proposed to include the concentrations of the essential elements in the source and target compartments into the transfer equation which leads to the specific activity model. This model has already been proposed by Comar et al. in 1956. It seems to work accurately for the transfer into animals and their products as well as into plants. Examples of its applicability are presented and discussed. Furthermore stochastic calculations seem to be more reasonable with this model.

Animals↗

PubMed1982