Long-term assessment of insecticides treatments in West Africa: aquatic entomofauna

For the control of the Onchocerca volvulus vector in West Africa, up to 18,000 km of rivers from 1975 and up to 50,000 km from 1989 had been partly sprayed weekly with insecticides as part of the Onchocerciasis Control Programme (OCP). To evaluate the possible short-term and long-term effects of the application of insecticides on the non-target fauna, an aquatic monitoring programme was set up during the initial phase of the programme. By analysing the invertebrate data, which were collected using various sampling strategies from four different countries between 1977 and 1996, this paper evaluates the long-term changes of the invertebrate populations with respect to their taxonomic composition as well as their trophic structures. The discussed results of the applied numerical analysis strategy suggest that neither the taxonomic nor the trophic structures are greatly altered from the range of biological, flow-related variation that normally occurs in the studied river systems. This allows us to conclude that the biological variation found here is ecologically acceptable.     

Inhibition of laccase activity from Trametes versicolor by heavy metals and organic compounds

Due to the numerous biotechnological applications of laccase enzyme, it is essential to know the influence of different agents usually present in the natural environment on its enzymatic action, especially for in situ treatment technologies. In the present work, a simple and rapid method to determine the inhibitory or inducer effect of different compounds on laccase activity was developed. The compounds tested were copper-chelating agents and heavy metals. It was found that using syringaldazine as a substrate, all copper-chelating agents (except EDTA) highly inhibited laccase activity (around 100%) at an inhibitor concentration lower than 20 mM. Moreover, 40% of inhibition, which was detected at a concentration of 20 mM for both Cd(2+) and Cu(2+) increased with concentration until nearly complete inhibition at 80 mM.     

Sources of pesticides in surface waters in Switzerland: pesticide load through waste water treatment plants--current situation and reduction potential

Concentrations of pesticides in Swiss rivers and lakes frequently exceed the Swiss quality goal of 0.1 microg/l for surface waters. In this study, concentrations of various pesticides (e.g., atrazine, diuron, mecoprop) were continuously measured in the effluents of waste water treatment plants and in two rivers during a period of four months. These measurements revealed that in the catchment of Lake Greifensee, farmers who did not perfectly comply with 'good agricultural practice' caused at least 14% of the measured agricultural herbicide load into surface waters. Pesticides, used for additional purposes in urban areas (i.e. protection of materials, conservation, etc.), entered surface waters up to 75% through waste water treatment plants.     

Carbon Tetrachloride Marine Risk Assessment with Special Reference to the Osparcom Region: North Sea

Accurate estimates of stressor levels in unsampled streams would provide valuable information for managing these resources over large regions. Spatial interpolation of stream characteristics have rarely been attempted, partly because defining separation distances between distinct stream samples is not straightforward. That is, conventional Eulerian definitions of separation distance may not apply to stream networks where information flows along distinct paths. A two-stage model for estimating stressor levels in unsampled streams is presented. Mean characteristics within streams are predicted usign a generalized additive model and residual variation is estimated using a conventional application of spatial statistics. The model is developed and tested using stream survey data collected in the state of Maryland, USA. Model efficiency is compared for three stream variables (nitrate concentration, sulfate concentration, and epifaunal substrate score) known to be associated with biological impairments in streams. Accounting for spatial autocorrelation in the residual variation improved model R2 from 0.71 to 0.81 for nitrate, from 0.29 to 0.63 for sulfate, and from 0.21 to 0.31 for epifaunal substrate score.     

1,4-Dichlorobenzene Marine Risk Assessment with Special Reference to the Osparcom Region: North Sea

This risk assessment on 1,4-dichlorobenzene was carried out for the marine environment, following methodology given in the EU risk assessment Regulation (1488/94) and Guidance Document of the EU New and Existing Substances Regulation (TGD, 1996). Data from analytical monitoring programs in large rivers and estuaries in the North Sea area were collected and evaluated on effects and environmental concentrations. Risk is indicated by the ratio of predicted environmental concentration (PEC) to predicted no-effect concentration (PNEC) for the marine aquatic environment. In total, 17 data for fish, 9 data for invertebrates and 7 data for algae were evaluated. Acute and chronic toxicity studies were taken into account and appropriate assessment factors used to define a final PNEC value of 20 microg/l. Recent monitoring data indicate that 1,4-dichlorobenzene levels in coastal waters and estuaries are below the determination limit of 0.1 microg/l used in monitoring programs. The worst case value recorded in river water is below 0.45 microg/l. Using these values, calculated PEC/PNEC ratios give safety margins of about 40-200, taking no account of dilution in the sea. Environmental fate and bioaccumulation data indicate that current use of 1,4-dichlorobenzene poses no risk to the aquatic environment.     

Probabilistic human health risk of PCDD/F exposure: a socioeconomic assessment

The aim of the present study was to assess the human health risks (carcinogenic and non-carcinogenic) of PCDD/F exposure for the adult population living in two different areas (industrial and residential) of Tarragona (Catalonia, Spain), as well as to compare these risks according to the socioeconomic status of the population. Two pathways were considered for PCDD/F exposure: direct (air inhalation, dermal contact and ingestion from soils and dust) and dietary. Although environmental exposure was higher for the population living in the neighborhood of the industrial area (mainly lower socioeconomic group subjects), it only accounted 1.05%. On the other hand, PCDD/F exposure through dietary intake was more important for those individuals of an upper socioeconomic level. This was due to the fact that their diet is richer in those foodstuffs containing higher PCDD/F concentrations. Consequently, taking together direct and dietary exposure to PCDD/Fs, the result is that upper socioeconomic group populations are more exposed to these toxic pollutants. In any case, the current levels of PCDD/F exposure would not mean significant carcinogenic and non-carcinogenic risks for the population living in the industrial and residential areas of Tarragona.     

Land district,ecophysiographic units and areas: The landscape mapping of the Ministère des Ressources naturelles du Québec

In 1985, the Ministère des Ressources naturelles established a Forest Ecological Survey Program for Southern Québec. One component of the program was the mapping of land districts, which provide a physiographically-based territorial reference system. The land districts have an average surface area of between 100 and 300 sq km. Since its inception, the department has further refined the methodologies and standardized the results. The current methodologies are based on inventory and analysis of the geographical distribution of permanent environmental components (e.g., relief, surficial deposits, geology, hydrography). The products include 1:50 000 maps of surficial deposits, 1:250 000 maps of the land districts and physiographic systems, and a computerized data bank.To date, 500 000 km square have been covered, and the estimated completion date for the work is 1999. To facilitate use of the products and to encourage the development of new applications, a guide for forest managers and other users has been recently published. The guide assists with forest management planning strategies based upon the physical environment, in particular the production and use of interpretation grids and maps. The products of the mapping process are, for many regions of Southern Québec, the only source of information on permanent environmental components.Currently, the Ministère des Ressources naturelles is planning to develop landscape maps of Southern Québec which identify ecophysiographic units (1:1 250 000) and ecophysiographic areas (1:2 500 000). These maps are based upon the integration of critical physiographic features and the synthesis of land regions.     

Fitting Data to Linear Combinations of Covariograms

We pursue a regression model for spatially-indexed data whose spatial correlation is determined by a linear combination of simple covariograms. The main interest lies in the estimation of the spatial parameters. As several common techniques appear ineffective for this setting, an algorithm is proposed to obtain parameter estimates and is assessed through simulation. It is found to provide greater stability than other methods of estimation. We discuss the influence of parametrization and site location on the efficacy of the estimation algorithms, and develop some guidelines as to the placement of sampling sites to improve the algorithm's performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Oxidative degradation of 2,4-xylidine by photosensitization with 2,4,6-triphenylpyrylium: homogeneous and heterogeneous catalysis

The possibility of using zeolites containing the 2,4,6-triphenylpyrylium cation as photocatalysts for the degradation of pollutants has been tested on aqueous xylidine (2,4-dimethylaniline) solutions as models for contaminated wastewaters. The influence of the photocatalyst and substrate concentrations on xylidine oxidation has been investigated in homogeneous solution, by performing a series of experiments chosen according to the experimental design methodology (Doehlert uniform array). The empirical models and the corresponding response surfaces obtained from data analysis have been used for simulating and predicting degradation efficiency. The results have shown that conversion increases with increasing amounts of photocatalyst and decreasing concentration of the model pollutant. The fluorescence of 2,4,6-triphenylpyrylium was quenched by xylidine with a rate constant k(q) of 3.1x10(9)M(-1)s(-1). This result suggests a direct electron transfer between the excited pyrylium salt and xylidine. Because of the limited stability of the photocatalyst in homogeneous media, a pyrylium containing Y-zeolite has been tested for the photocatalytic oxidation of xylidine under heterogeneous conditions. The results suggest that the supported catalyst has a much improved stability and that xylidine oxidation rates remain nearly constant during the whole reaction time. An additional advantage of the pyrylium containing zeolite photocatalyst is that it can be recycled and used for further experiments.     

Study of the biodegradation process of polychlorinated biphenyls in liquid medium and soil by a new isolated aerobic bacterium (Janibacter sp.)

We have isolated and characterised a novel aerobic bacterial strain, designated MS3-02, belonging to the genus Janibacter sp. The capability of this new strain to degrade polychlorinated biphenyls (PCBs) in a commercial mixture (Aroclor 1242) in liquid medium and in soil (sterile and non sterile soil), under laboratory scale, has been evaluated. MS3-02 was isolated from the soil around of an incinerator, located in the east of Madrid (Spain). Gas-chromatographic analysis showed that MS3-02 was able to reduce most peaks observed in the chromatogram between 70% and 100% after seven days of incubation in a culture mineral medium containing yeast extract, but without the addition of biphenyl. The presence of biphenyl in the culture medium decreased the rate of PCB degradation by this bacterium. Comparing the performance of the MS3-02 in liquid culture medium and in soil, degradation was less efficient in sterile soil and still less efficient in non sterile soil. Under the best conditions (sterile soil and 20 weeks of incubation) MS3-02 was able to reduce, between 50% and 100%, nine of the main gas-chromatographic peaks in Aroclor 1242.