Environments in Pakistan are subject to increasing pollution, but previous studies were very scanty. During 1999 and 2000, we assessed trace element contamination at three wetlands, Karachi Harbour (with presumed industrial-urban pollution), Taunsa Barrage (agricultural pollution), and Haleji Lake (relatively unpolluted), using as indicators the eggs and the feathers of colonial waterbirds, particularly Little Egrets, their prey, and the sediments collected within their foraging areas. The concentrations of As, Cd, Cr, Pb, Hg, Mn, Se, and Zn were generally within the normal background level, and mostly below the threshold that may affect bird survival or reproduction. However, somewhat high concentrations were found in fish from Karachi, for Pb that was at levels that may harm fish reproduction, and for Hg that was at limit concentration for human consumption. Alarming concentrations were found for Cr and Se in sediments from Karachi, that were above the critical levels for contaminated soil, and Se in eggs, that may affect egret reproduction. The differences among the three wetlands were less marked than hypothesized. The egret species within the same area differed in the concentration of certain elements in their eggs, possibly because females may have foraged in different habitats before breeding, whereas no interspecies difference was found in chick feathers, presumably because their food had been collected in similar habitats around the colony. High bioaccumulation from sediments to organic samples occurred for Hg, while Cd, Se, and Zn exhibited low accumulation; for all these elements, feathers of predatory birds such as the egrets are the best indicators of environmental contamination. On the other hand, As and Cr did not bioaccumulate, and the sediments, or the organisms low in the food chain, like fish or crustaceans, are better indicators of their presence in the environment than predatory birds.

No abstract

The rapidly developing Asian countries may face threatening environmental contamination, that however remains largely unassessed. We studied persistent trace elements in three wetlands, Poyang Lake, relatively unpolluted, and Tai Lake, and Pearl River Delta, selected as hotspots of pollution in Central China. We adopted as indicator the Little Egret, a widespread colonial waterbird, and during 1999 and 2000 we collected and analysed the same samples as for a parallel study we conducted in Pakistan, e.g. eggs, body feathers of chicks, prey spontaneously regurgitated by the chicks, and sediments at the areas most used by foraging egrets. The levels of trace-metals at our three study areas were similar, or within the range, of those found in the few other studies for East Asia, with few exceptions. The concentrations of the various elements were below the threshold that may affect the survival or reproduction of the birds, and even the highest concentrations relative to background, i.e. Se in eggs, and Hg in feathers at Pearl Delta, do not pose toxic hazards. In sediments, the levels of trace elements were lower than the critical levels assumed for contaminated soil, except for alarming high levels of As at Poyang. These results do not confirm our expectation, that Poyang was relatively uncontaminated, while Tai and Pearl were polluted. Although trace metal concentration differed significantly among the three study areas, these differences were minor and were not consistent among elements and samples. The bioaccumulation ratios from sediments through prey, feather and egg, were consistent with our previous findings for Pakistan. Only Hg exhibited high bioaccumulation, while Se and Zn had low accumulation, and the other elements no accumulation. This reasserts that feathers of predators such as egrets, may be more sensitive indicators of environmental contamination for the elements subject to bioaccumulation, whereas the sediments or the organisms low in the food chain are better indicators for the other elements.

No abstract

Round Robin Coals-1972. At these ppm levels, the NAA-LEPD analysis is rapid, easy, and accurate to perform. The accuracy of the values obtained in Table II was checked against another NAA method coupled with radiochemical solvent extraction and the values were ±5% of each other.As sources of error, consideration should be given to two possible problems-that of matrix absorption of low energy photons and the diffusion of the fission fragment 133I through the walls of the polyethylene vials used in the irradiation. The first problem can easily be solved by using, where possible, standards which duplicate in size, volume, and composition the sample matrix. Solids can best be counted as stable, thin layers distributed on the bottom of a thin plastic container covering the active diameter of the detector. The possible problem of 133I loss due to diffusion through the plastic vials did not appear in our research. This probably was due to the chemical absorption of the 133I on the coal; and to a lesser extent in the other samples, the competition of a very small concentration of iodine vs. the chemical binding possibilities of a much larger matrix. At higher 133I levels, this might not hold true, thus necessitating appropriate corrections to data.There are several other points in favor of the LEPD emphasized by the analysis of the various materials in Table I. These were: 1) The analysis of uranium in sea water which is noted for its 24Na gamma activity interference (upon reactor irradiation) with standard GeLi and Nal detectors was not hampered by using the LEPD detector. 2) Four abundant X-rays and low energy gammas from 133I decay Table II.