10 research outputs found
The local deposition of heavy metal emissions from point sources in Antarctica
Surface snow samples have been analysed for the heavy metals Cd, Cu, Pb and Zn to investigate the spatial scale of local sources of pollution in Antarctica. Samples from around an isolated petrol generator showed vastly increased levels (up to 800,000 times background) directly under the exhaust. Concentrations fell sharply with distance from the exhaust, reaching background levels at 40 m, even in the downwind direction. Snow was also collected at various distances from a manned scientific station. The data are more difficult to interpret, but the influence of the station could not be detected beyond 10 km. These findings indicate the areas that are influenced by local emissions, and that are therefore unsuitable for air and snow sampling intended to study larger-scale pollution input
Preconcentration method for electrothermal atomic absorption spectrometric analysis for heavy metals in Antarctic snow at sub ng kgâ1 levels
An improved technique for concentrating heavy metals onto the surface of tungsten wires, prior to analysis by electrothermal atomic absorption spectrometry, is reported. Ultraclean methods and materials, described here, have enabled improvements in detection limits to be realised. With the new procedure, detection limits of 0.01 ng Cd kgâ1, 0.47 ng Cu kgâ1, 0.22 ng Pb kgâ1 and 0.24 ng Zn kgâ1 are obtained. These are low enough to allow analysis of ancient and modern. Antarctic snow, except perhaps for cadmium. A comparison with samples injected directly into the graphite furnace shows good agreement, confirming that the method is suitable for the simple polar snow matrix
Seasonal input of heavy metals to Antarctic snow
Cadmium, copper, lead and zinc concentrations have been measured on a sequence of snow blocks covering 2 yearsâ accumulation at a site on the east coast of the Antarctic Peninsula. Careful collection and analysis techniques have ensured good data quality despite the very low concentrations, which averaged Cd 0.08 ng kg-1, Cu 4 ng kg-1, Pb 4 ng kg-1, Zn 0.4 ng kg-1. The elements show significant variations through the year. Pb has peaks in the autumn/winter period when both the crustal and marine aerosol are also at their maxima; despite a probable pollutant origin, Pb appears to be associated with natural aerosol in long range transport. No clear seasonal signal is observed for the other metals. At this site, the marine contribution to the concentrations of some metals may be significant
Glycerol/Glyoxal: A New Boron Fixation System for Wood Preservation and Dimensional Stabilization
Estudos histomorfomĂ©trico e histolĂłgico das lesĂ”es Ăłsseas causadas por flĂșor em aves Histomorphometric and histological evaluations of the bone lesions caused by fluoride in chickens
Fluoreto de sĂłdio foi administrado na ĂĄgua de 2 grupos de 25 aves, fĂȘmeas, da raça Shaver. O grupo A recebeu flĂșor do 1 ao 120 dia de idade e o grupo B do 61 ao 120 dia de idade. Cada grupo foi dividido em 5 nĂveis de tratamento: 0, 25, 50, 200 e 400 ppm de flĂșor, com 5 animais por tratamento. Todos os animais foram sacrificados aos 120 dias de idade. Para o estudo histomorfomĂ©trico foram coletados o fĂȘmur e a tĂbia esquerdos, e para o estudo histolĂłgico foram coletados fĂȘmur e tĂbia direitos. No estudo histomorfomĂ©trico do osso compacto observou-se um discreto aumento da porosidade cortical, que nĂŁo foi estatisticamente significativo. A espessura do osso cortical aumentou nos animais tratados com flĂșor (p<0,05, r2 = 0,59). No osso trabecular, do grupo A, houve um aumento da espessura trabecular (ET) (p<0,05, r2 = 0,63) e do volume trabecular Ăłsseo (VTO) (p<0,05, r2 = 0,72) atĂ© a dose de 200 ppm; e, na dose de 400 ppm, ocorreu um decrĂ©scimo, demonstrado pela regressĂŁo quadrĂĄtica obtida na anĂĄlise de regressĂŁo. No grupo B houve um aumento progressivo da ET (p<0,05, r2 = 0,98) e do VTO (p<0,05, r2 = 0,77) diretamente relacionado com a dose de flĂșor. A superfĂcie de osteĂłide (SO) apresentou, tambĂ©m, um aumento gradativo relacionado com a dose, nos animais tratados com flĂșor (p<0,001, r2 = 0,80). Esses resultados sugerem que o flĂșor estimula a função osteoblĂĄstica, resultando em aumento da SO, e consequentemente maior aposição Ăłssea. No entanto, nos animais tratados com 400 ppm, durante 120 dias, esse estĂmulo sobre a aposição Ăłssea nĂŁo foi tĂŁo evidente, sugerindo que o flĂșor determina alguma alteração funcional sobre os osteoblastos ou um aumento da reabsorção Ăłssea. Histologicamente, observou-se espessamento trabecular nos animais tratados com flĂșor, mais marcado nas doses de 200 e 400 ppm, em ambos os grupos. Sobre a superfĂcie trabecular, dos animais tratados com 200 e 400 ppm, evidenciou-se, principalmente, osteoblastos ativos e osteoclastos, sugerindo um aumento da remodelação Ăłssea. No osso cortical observou-se diminuição dos canais de Havers, prĂłximos a superfĂcie periosteal, e aumento das lacunas de reabsorção prĂłximas a superfĂcie endosteal.<br>Sodium fluoride was administered in the water to 2 groups of 25 Shaver female poultry. Group A received fluoride from 1 to 120 days of age and group B from 61 to 120 days. Each group was divided into 5 treatments, with 5 chickens each, which received 0, 25, 50, 200, and 400 ppm of fluoride in the water, respectively. All animals were killed at 120 days of age. For histomorphometric studies the left femur and tibia were used, and for histologic studies the right femur and tibia. In the cortical bone, cortical porosity was slightly increased by fluoride, but the differences with the control group were not significant. Cortical thickness increased in the animals treated with fluoride (p<0,05, r2 = 0,59 ). In the trabecular bone, of group A, trabecular thickness (TT) (p<0,05, r2 = 0,63) and trabecular bone volume (TBV) (p<0,05, r2 = 0,72) increased in treatments receiving 25-200 ppm, and decreased in the 400 ppm treatment, as it was demonstrated by quadratic regression analysis. In group B there was a positive linear correlation on TT (p<0,05, r2 = 0,98) and TBV (p<0,05, r2 = 0,77) with fluoride ingestion.The osteoid surface was also positively correlated with the amount of fluoride ingested by the animals (p<0,001, r2 = 0,80). These results suggest that fluoride improves osteoblastic function resulting in increased osteoid production and bone apposition. In the other hand, in the animals treated with 400 ppm of fluoride for 120 days bone apposition was reduced suggesting a functional alteration of the osteoblasts or improved bone resorption. In the histological study of bone tissue all animals that received fluoride showed an increased trabecular thickness which was more marked in the 200-400 ppm treatments. In chickens treated with 200-400 ppm of fluoride osteoblasts and osteoclasts were more numerous suggesting an increased bone turnover. In cortical bone Haversian canals were narrowed on the periosteal surfaces and resorption spaces were enlarged on the endosteal surfaces
Selected elements in surface waters of Antarctica and their relations with the natural environment
The aim of the study was to specify the concentration of selected chemical elements in surface waters of King George Island, off the western coast of the Antarctic Peninsula. The research encompassed six streams, a lake and an artificial water reservoir located on the western coast of Admiralty Bay. Measured hydrochemical parameters included pH, conductivity, total dissolved solids (TDS), and total and dissolved forms elements such as Al, Co, Ni, Cu, Zn, Cd, Pb, Mn, Fe, As and Se. The values of pH, conductivity and TDS had the following ranges: 6.09â8.21, 6.0â875 ”S cmâ1 and 7.0â975 mg/L, respectively, and were typical for surface waters of Antarctica. Wide disparities were discovered regarding concentrations of the investigated elements, ranging from <0.01 ”g/L for Cd to 510 ”g/L for Fe, and differing from one water body to another. The investigated elements are discussed with reference to environmental conditions and anthropogenic factors. Concentrations of total and dissolved forms of elements are considered in connection with the composition of soil in their surroundings and with atmospheric deposition, mostly such as that took place locally. The increased levels of Pb and Zn concentrations in the immediate proximity of a research station suggested anthropogenic contamination