Search

Although the use of the water resources in Uzbekistan is strongly limited by their quality, it has to be noted that there is a lack of information and data within the international scientific literature with regard to the water chemical characteristics of the Amu Darya River, one of the main water resources in Central Asia. To add to such knowledge, this paper examines the spatial and temporal variation of the water quality of the Amu Darya River in order to assess its degree of degradation and the main causal factors. The functional relationships of the pollutants with respect to the flow regime are investigated. Finally an "opportune temporal window" for water withdrawal for filling the reservoirs, in relation to human consumption, will be indicated. The high salinization levels of the waters are mainly due to the presence of sulphates and chlorine. At the up-stream site salinity, although presenting elevated concentrations, does not exceed palatability levels; after the 450 km point the opportune temporal window for water withdrawal with acceptable salinity values is reduced to the period from May to September. Two main driving forces govern the temporal variation of the salinity of the Amu Darya water: a low drainage density of the area which limits the salt loads induced by the natural runoff processes, and snow and glacier melting in the upper catchment area which promotes dilution of the dissolved salts during the high-flow period. During low-flow periods salinity is strongly influenced by the return of waters used for land washing and irrigation. © 2006 Elsevier Ltd. All rights reserved.

A preliminary investigation has been carried out on the occurrence and effects of antibiotics used in Italian aqua-culture with the objective of identifying priorities for monitoring programmes. According to the information available on the most pertinent and diffuse fish diseases and their related therapies, the presence of flumequine and oxytetracycline in sediments sampled from two trout farms and three sea-bass farms and in their surrounding environments was selected for an analytical investigation. The concentrations of oxytetracycline and flumequine varied up to a maximum of 246.3 and 578.8 mug/kg d.w., respectively. Flumequine was seen to have the highest toxicity in a bioluminescence assay with EC50 values varying within the range of 12-15 mg/l, while the EC50 values for oxytetracycline were within the range of 121-139 mg/l. The results of the present study indicate flumequine and oxytetracycline as priority chemicals to be monitored for possible environmental side effects of aquaculture in Italy. Apart from peak concentrations the chronic presence of flumequine and oxytetracycline in sediments both inside and outside farms should also be considered. In spite of the potential risks related to the use of antibiotics, the concentrations found in the sediments of the studied fish farms are significantly lower than those found in other areas. (C) 2003 Elsevier Ltd. All rights reserved.

For the control of the aquatic stage of the blackfly vector of the onchocerciasis in West Africa, rivers had been partially sprayed weekly with insecticides from 1974 to 2002 on an area over 1 million km2, as part of the onchocerciasis control programme (OCP). To evaluate the possible short- and long-term effects of insecticides on non-target fauna, an aquatic monitoring programme was set-up and carried on for over 20 years. A number of papers have been published concluding that biological variations found are ecologically acceptable. In this paper, by means of a new elaboration of a subset of data, the authors discuss value and limitations of the data analysis methodologies utilised in the ecological assessment. Multivariate analysis, rank-abundance curves and diversity indices are applied to evaluate the modification occurred in invertebrate community taxa richness and evenness. These methodologies allow to decompose the variance between insecticides effects and seasonal biological variations, to evidence the relative toxicological potency and to show the fingerprint of action among various insecticides.

Comprehensive and contemporary evaluations of physical, chemical and toxicological endpoints have been performed on bed sediments of the Po River, the major Italian watercourse. Two extensive sampling campaigns were conducted in summer and winter low-flow conditions. Composite sediment samples were collected from ten reaches of the main river: the first was located in the upper region (ambient control), and the others downstream of the confluences of nine principal tributaries. The two sampling programs were paralleled by contemporary investigations on the macroinvertebrate community. The particle-size composition along the Po River showed a relatively uniform distribution of fine sand, a progressive downstream decrease of coarse sands and a corresponding increase of fine materials. The levels of polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), extractable organo halides (EOX), Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in sediment fine particles (63 microm), and showed marked changes across the ten river reaches. Their longitudinal trends, as those of organic carbon and total nitrogen, were very similar and largely independent of the survey season. Sediment quality benchmarks were used to evaluate sediment chemistry, and, although the overall level of contamination was from moderate to low, the reaches located downstream of the tributaries Dora Riparia, Dora Baltea, Lambro and Oglio were considered to be at risk. Sediments were tested for toxicity on Oncorhynchus mykiss, Ceriodaphnia dubia, Raphidocelis subcapitata and Vibrio fischeri. The toxicity tests were conducted both with sediment extracts and whole samples. Sediment extracts showed toxic potentials that were consistent with the spatial distribution of contaminants. Whole-sediment toxicity showed moderate/low effects which also included false positives and negatives. Alterations of the macroinvertebrate community were found for many kilometers downstream of Dora Riparia, and with a seasonal dependence, also in other reaches of the Italian river. Principal component analysis (PCA) was used to describe the longitudinal and temporal changes of the Po River, and allowed the selection of the most useful and discriminating indicators.

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.

In West Africa different insecticides had been applied in selected river areas for the reduction of the blackfly populations vectors of Onchocerca volvulus, a parasite causing blindness. To evaluate the possible long term effects of the larvicides on the non target fauna an aquatic monitoring programme has been up from the initial phase of the project. Addressing the attention to the invertebrates data collected in four countries during a maximum period ranging from 1977 to 1996, this paper shows and discusses the data analysis strategy for the measure and interpretation of the biological variation. In particular the application of quantitative ecological analysis methods: Principal Component Analysis, rank abundance models and the community diversity indexes, is critically discussed and comments are given to the ecological interpretation of the results. ©1998 Elsevier Science Ltd. All rights reserved