خيارات البحث
النتائج 1 - 10 من 55
Risk of tuberculosis in high-rise and high density dwellings: An exploratory spatial analysis النص الكامل
2013
Lai, Poh C. | Low, Chien-Tat | Tse, Wing-Sze Cindy | Tsui, Chun-Kan | Sun Ra, | Hui, Pak-Kwan
Studies have shown that socioeconomic and environmental factors have direct/indirect influences on TB. This research focuses on TB prevalence of Hong Kong in relation to its compact urban development comprising of high-rise and high-density residential dwellings caused by rapid population growth and limited land resources. It has been postulated that occupants living on higher levels of a building would benefit from better ventilation and direct sunlight and thus less likely to contract infectious respiratory diseases. On the contrary, those on lower floors amid the dense clusters of high-rises are more susceptible to TB infection because of poorer air quality from street-level pollution and lesser exposure to direct sunlight. However, there have not been published studies to support these claims. As TB continues to threaten public health in Hong Kong, this study seeks to understand the effects of housing development on TB occurrences in an urban setting.
اظهر المزيد [+] اقل [-]Ecotoxicity of nanoparticles of CuO and ZnO in natural water النص الكامل
2010
Blinova, I. | Ivask, A. | Heinlaan, M. | Mortimer, M. | Kahru, A.
The acute toxicity of CuO and ZnO nanoparticles in artificial freshwater (AFW) and in natural waters to crustaceans Daphnia magna and Thamnocephalus platyurus and protozoan Tetrahymena thermophila was compared. The L(E)C50 values of nanoCuO for both crustaceans in natural water ranged from 90 to 224 mg Cu/l and were about 10-fold lower than L(E)C50 values of bulk CuO. In all test media, the L(E)C50 values for both bulk and nanoZnO (1.1–16 mg Zn/l) were considerably lower than those of nanoCuO. The natural waters remarkably (up to 140-fold) decreased the toxicity of nanoCuO (but not that of nanoZnO) to crustaceans depending mainly on the concentration of dissolved organic carbon (DOC). The toxicity of both nanoCuO and nanoZnO was mostly due to the solubilised ions as determined by specific metal-sensing bacteria. Natural waters remarkably reduced the toxicity of nanoCuO but not nanoZnO.
اظهر المزيد [+] اقل [-]Heavy metal contamination in surface sediments of Yangtze River intertidal zone: An assessment from different indexes النص الكامل
2009
Zhang, Weiguo | Feng, Huan | Chang, Jinna | Qu, Jianguo | Xie, Hongxia | Yu, Lizhong
Surface sediments (0-5 cm) from 59 stations within the Yangtze River intertidal zone (YRIZ) were sampled for metal contamination analysis in April and August 2005. The concentrations ranged (in mg kg-¹ dry weight): Al, 40,803-97,213; Fe, 20,538-49,627; Cd, 0.12-0.75; Cr, 36.9-173; Cu, 6.87-49.7; Mn, 413-1,112; Ni, 17.6-48.0; Pb, 18.3-44.1; and Zn, 47.6-154; respectively. Among the 59 sampling stations, enrichment factors (EF) indicate enrichment of Cd (52 stations), Cr (54 stations), Cu (5 stations), Ni (26 stations), Pb (5 stations) and Zn (5 stations). Geoaccumulation indexes (Igeo) also suggest individual metal contamination in localized areas. This study indicates that Cd, Cr and Ni enrichment in the YRIZ sediment is widespread whereas Cu, Mn, Pb and Zn enrichment is localized or nonexistent. Factor and cluster analyses indicate that Cd is associated with total organic carbon whereas Cu, Cr, Ni, Pb and Zn have a close association with Mn. Surface sediment metal enrichment is evidenced for Cd, Cr and Ni in the Yangtze River intertidal zone.
اظهر المزيد [+] اقل [-]Organic phosphorus species in surface sediments of a large, shallow, eutrophic lake, Lake Taihu, China النص الكامل
2009
Bai, Xiuling | Ding, Shiming | Fan, Chengxin | Liu, Tao | Shi, Dan | Zhang, Lu
Organic phosphorus (P) fractions in surface sediments from a large shallow, eutrophic Lake Taihu, China, were extracted with 0.1 M NaOH after pre-treatment of the sediments with a solution composed of 0.1 M EDTA and 2% (w/v) Na₂S₂O₄. Composition of organic P in the extracts was then characterized by ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR). Several P species, including phosphonates, orthophosphate, orthophosphate monoesters, phospholipids, DNA, pyrophosphate and polyphosphate, were detected in the NaOH extracts. The proportion of extracted organic P to total P in sediments was negatively correlated with total P in the water column, as were the proportions for orthophosphate monoesters and DNA. This implies that the majority of organic P in surface sediments is likely stabilized in some way, and does not directly contribute to the internal loading of P from sediments. Organic phosphorus species in surface sediments of Lake Taihu.
اظهر المزيد [+] اقل [-]Water quality in the Tibetan Plateau: Metal contents of four selected rivers النص الكامل
2008
Huang, Xiang | Sillanpaa, Mika | Duo, Bu | Gjessing, Egil T.
The water used by 85% of the Asian population originates in Tibetan Plateau. During April and May of 2006, water samples were collected from four major Asian rivers in the Plateau (i.e. the Salween, Mekong, Yangtze River and Yarlung Tsangpo) and analyzed for Cu, Pb, Zn, Ag, Mo, Cd, Co, Cr, Ni, Li, Mn, Al, Fe, Mg and Hg. The results showed that elements such as Mg were rather high in Tibetan rivers, giving a mean electrical conductance of 36 mS/m. In a few locations, the results also showed relatively high concentrations of Al and Fe (>1 mg/L). However, the concentrations of Cu, Zn, Ag, Cd, and Cr were generally low. Contamination with Pb was identified at a few locations in the Salween and Ni at a few sites in the Yangtze River. For the first time, total dissolved metal contents in source water of four major Asian rivers were evaluated at the same time.
اظهر المزيد [+] اقل [-]New Miscanthus hybrids cultivated at a Polish metal-contaminated site demonstrate high stomatal regulation and reduced shoot Pb and Cd concentrations النص الكامل
2019
Rusinowski, Szymon | Krzyżak, Jacek | Clifton-Brown, John | Kane, Elaine | Mos, Michal | Webster, Richard | Sitko, Krzysztof | Pogrzeba, Marta
The increased bioeconomy targets for the biomass share of renewable energy production across Europe should be met using land unsuitable for food production. Miscanthus breeding programs targeted the production of plants with a diverse range of traits allowing a wider utilization of land resources for biofuel production without competing with arable crops. These traits include increasing tolerances to drought, chilling, and to metal(loid)s excess. Two novel Miscanthus hybrids, GNT41 and GNT34, were compared against Miscanthus x giganteus (Mxg) on metal-contaminated arable land in Poland. This study aimed at evaluating their yield, biomass quality and quantifying seasonal differences in photosynthetic and transpiration parameters. A secondary objective was to identify key physiological mechanisms underlying differences in metal accumulation between the investigated plants. The new hybrids produced a similar yield to Mxg (13–15 t ha−1 yr−1), had shorter shoots, higher Leaf Area Index and stem number. Based on gas exchange measurements, GNT34 exhibited isohydric (water-conserving) behavior. The stomatal response to light of the new hybrids was at least twice as fast as that of Mxg, a trait that is often associated with increased seasonal water use efficiency. This contributed to the almost 40% reduction in shoot Pb and Cd concentrations for the new hybrids as compared to Mxg. This suggested that promoting stomatal regulation in conjunction with improved water conservation may be a target for improving plants for wider use on metals contaminated land.
اظهر المزيد [+] اقل [-]Detection of phosphorus species in sediments of artificial landscape lakes in China by fractionation and phosphorus-31 nuclear magnetic resonance spectroscopy النص الكامل
2009
Liu, Jinyong | Wang, Hui | Yang, Haijun | Ma, Yanjun | Cai, Ouchen
Phosphorus (P) pollution in the sediments of seven artificial landscape lakes was studied via fractionation and phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. The lake sediments accumulated significant amounts of P from supplementation with reclaimed water and from runoff from the golf course lawns. The differences in total sediment P among lakes were correlated to the varied pollution extent from the lawns. One striking feature of the artificial lake sediments was the insufficiency of NaOH-extracted Al, which plays an important role in avoiding internal P release during anoxia. Another characteristic was the dominance of orthophosphate in the NaOH-EDTA extractants of the sediments, due to the heavy external P pollution. Phytate, considered prevalent in many soils and lake sediments, as well as polyphosphates and phosphonates which have appeared in some natural lake sediments, was not detected. The rank order of present biogenic P species was monoester-P > DNA-P > pyrophosphate > lipid-P. Mineral fixation and biological conversion of phosphorus were investigated in artificial lake sediments in China.
اظهر المزيد [+] اقل [-]Inorganic arsenic speciation at river basin scales: The Tinto and Odiel Rivers in the Iberian Pyrite Belt, SW Spain النص الكامل
2009
The Tinto and Odiel rivers are heavily affected by acid mine drainage from mining areas in the Iberian Pyrite Belt. In this work we have conducted a study along these rivers where surface water samples have been collected. Field measurements, total dissolved metals and Fe and inorganic As speciation analysis were performed. The average total concentration of As in the Tinto river (1975 μg L-1) is larger than in the Odiel river (441 μg L-1); however, the mean concentration of As(III) is almost four times higher in the Odiel. In wet seasons the mean pH levels of both rivers (2.4 and 3.2 for the Tinto and Odiel, respectively) increase slightly and the amount of dissolved total arsenic tend to decrease, while the As(III)/(V) ratio strongly increase. Besides, the concentration of the reduced As species increase along the water course. As a result, As(III)/(V) ratio can be up to 100 times higher in the lower part of the basins. An estimation of the As(III) load transported by both rivers into the Atlantic Ocean has been performed, resulting in about 60 kg yr-1 and 2.7 t yr-1 by the Tinto and Odiel rivers, respectively. Total arsenic concentration decreases along the water basins, however the As(III)/(V) ratio increases.
اظهر المزيد [+] اقل [-]Occurrence and behaviour of selected hydrophobic alkylphenolic compounds in the Danube River النص الكامل
2009
Micić, Vesna | Hofmann, Thilo
Six hydrophobic alkylphenolic compounds were investigated for the first time simultaneously in four different matrices in the Danube River. Maximum sediment concentrations were 2.83, 2.10, 0.28, and 0.035 mg kg⁻¹ for nonylphenol, nonylphenol monoethoxylate, nonylphenol diethoxylate and octylphenol. Maximum levels in suspended particulate matter (SPM) were 0.18, 0.12, 0.10, and 0.003 mg kg 1. No correlation between concentrations in SPM and sediments was found. Octylphenol monoethoxylate and octylphenol diethoxylate were recorded only in sediment at one location. In mussels and water only nonylphenol and octylphenol were found. Nonylphenol concentrations in mussels (up to 0.34 mg kg⁻¹) correlate with concentrations found in SPM and indicate a slight bioaccumulation. Concentrations in water were close to the limit of quantification. We assume in situ formation of nonylphenol monoethoxylate and nonylphenol in sediments at some locations. In some cases nonylphenol in sediments exceeded the provisional EU environmental quality standards.
اظهر المزيد [+] اقل [-]Long-term nitrate increases in two oligotrophic lakes, due to the leaching of atmospherically-deposited N from moorland ranker soils النص الكامل
2008
Tipping, E. | Thacker, S.A. | Wilson, D. | Hall, J.R.
During the last 50 years nitrate concentrations in Buttermere and Wastwater (Cumbria, UK) have risen significantly, by 70 and 100%, respectively. By estimating contemporary nitrate fluxes in the lakes' catchments and in sub-catchments and comparing them with the fractional areas of different soil types, it is deduced that the surface water nitrate is derived almost entirely from organic-rich ranker soils that have a limited ability to retain atmospherically-deposited nitrogen. Little or no nitrate leaches from the other major soil type, a brown podzol, despite it having a lower C:N ratio (12.0 g g-1) than the ranker (17.0 g g-1), nor is there much contribution from the small areas of improved (chemically fertilised) grassland within the catchments. Although some nitrate leaching is occurring, total N losses are appreciably smaller than atmospheric inputs, so the catchment soils are currently accumulating between 3 and 4 g N m-2 a-1. Increases in lakewater nitrate concentrations over 50 years are due to the limited ability of ranker soils to retain atmospherically-deposited nitrogen.
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