Towards enhancing tidally-induced water renewal in coastal lagoons

Environmental Fluid Mechanics - In order to address the problem of limited water renewal in restricted lagoons of moderate size having at least two tidal inlets, a method is proposed to enhance...     

Polychlorinated biphenyls in marine sediments from the southern North Sea and Scheldt estuary: a ten-year study of concentrations, patterns and trends

The paper reports the concentrations and patterns of CBs in sediments of the Belgian part of the southern North Sea and the Scheldt estuary for the period 1991-2001. The long-term analytical performance was well within the quality assurance boundaries set at the outset of the study and is consistent with the state of the art for this type of analysis. The CB concentrations (given as the median of the sum of IUPAC Nos 28, 52, 101, 118, 138, 153 and 180) vary between 0.1 microg kg(-1) and 50 microg kg(-1) dry weight in the total sediment and it could be demonstrated that CB patterns in the fine fraction of the sediment were closely similar throughout the investigated area. Isolation of the fine fraction (<63 microm) by sieving can be regarded as a physical normalisation to reduce the differences in sediment granulometric composition. It allows for a better understanding of CB distribution and patterns and improves the trend analysis. A significant downward trend could not be found at any of the stations, which suggests that CB levels have not been changing in the area of interest in the past decade.     

Vegetation as an indicator of environmental changes

Composition of the vegetation and the properties of its environment are related, as was shown by research. In these, mostly statistical-correlative studies, both the vegetation and some growth factors, such as plant nutrients and moisture supply were analyzed and studied on interdependence. At present the environmental conditions can be estimated in the field from the floristic composition with regard to differences both in the combination of plant species and in their relative biomass production. With a vegetation survey the spatial pattern of the different environmental conditions can be indicated. For instance, the places where moisture supply gradients occur can be detected, also a better understanding is obtained of the environmental equalization and the decreasing number of plant species and spatial diversity. Conclusions can be drawn about changes in the vegetation to be expected, from the combined occurrence of, a terrestrial vegetation indicating an eutrofied environment and a water vegetation indicating a relatively oligotrophic environment. By comparing vegetation recordings of the past and present, environmental changes that have occurred in the same place can be indicated. By vegetations situated in different places in relation with soil profile properties the consequences of environmental changes can be predicted. For instance, lowering of the ground water table and intensifying the agricultural use. On the other hand, measures can be suggested to increase the biological value of land and water, for instance, indication of seepage areas and floristically rich areas in the field.     

Identifying optimal agricultural countermeasure strategies for a hypothetical contamination scenario using the strategy model

A spatially implemented model designed to assist the identification of optimal countermeasure strategies for radioactively contaminated regions is described. Collective and individual ingestion doses for people within the affected area are estimated together with collective exported ingestion dose. A range of countermeasures are incorporated within the model, and environmental restrictions have been included as appropriate. The model evaluates the effectiveness of a given combination of countermeasures through a cost function which balances the benefit obtained through the reduction in dose with the cost of implementation. The optimal countermeasure strategy is the combination of individual countermeasures (and when and where they are implemented) which gives the lowest value of the cost function. The model outputs should not be considered as definitive solutions, rather as interactive inputs to the decision making process. As a demonstration the model has been applied to a hypothetical scenario in Cumbria (UK). This scenario considered a published nuclear power plant accident scenario with a total deposition of 1.7x10(14), 1.2x10(13), 2.8x10(10) and 5.3x10(9)Bq for Cs-137, Sr-90, Pu-239/240 and Am-241, respectively. The model predicts that if no remediation measures were implemented the resulting collective dose would be approximately 36 000 person-Sv (predominantly from 137Cs) over a 10-year period post-deposition. The optimal countermeasure strategy is predicted to avert approximately 33 000 person-Sv at a cost of approximately 160 million pounds. The optimal strategy comprises a mixture of ploughing, AFCF (ammonium-ferric hexacyano-ferrate) administration, potassium fertiliser application, clean feeding of livestock and food restrictions. The model recommends specific areas within the contaminated area and time periods where these measures should be implemented.     

Rat metabolism of polychlorinated dibenzo-p-dioxins

In rats, dibenzo-p-dioxin, 1-chlorodibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin, 2,3-dichlorodibenzo-p-dioxin, 2,7-dichlorodibenzo-p-dioxin, 1,2,4-trichlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin are metabolized to mono- and dihydroxy derivatives, whilst in case of dibenzo-p-dioxin and both the two monochloro isomers, also sulphur containing metabolites are excreted. Primary hydroxylation exclusively takes place at the 2-, 3-, 7- or 8-position in the molecule. In none of the experiments metabolites resulting from fission of the C-O bonds (ortho, ortho'-dihydroxychlorodiphenyl ethers, chlorocatechols) or hydroxylated derivatives thereof, were detected. No metabolites were found from octachlorodibenzo-p-dioxin.     

Determination of metoxuron and 3-chloro-4-methoxyaniline via direct derivatization with heptafluorobutyric anhydride and GC-ECD

The phenylurea herbicide metoxuron and its main metabolite, 3-chloro-4-methoxyaniline, can be determined rapidly in aqueous samples via extraction, derivatization with heptafluorobutyric anhydride (HFBA), washing with an aqueous bufferof pH 8, and analysis by capillary GC with electron capture detection. Linear calibration curves are obtained over two orders of magnitude, and the detection limit for the HFB derivatives is about 0.5 pg. The method has successfully been applied to several types of water samples.