خيارات البحث
النتائج 451 - 460 من 1,324
Nitrogen deposition and its ecological impact in China: An overview النص الكامل
2011
Liu, Xuejun | Duan, Lei | Mo, Jiangming | Du, Enzai | Shen, Jianlin | Lu, Xiankai | Zhang, Ying | Zhou, Xiaobing | He, Chune | Zhang, Fusuo
Nitrogen (N) deposition is an important component in the global N cycle that has induced large impacts on the health and services of terrestrial and aquatic ecosystems worldwide. Anthropogenic reactive N (Nᵣ) emissions to the atmosphere have increased dramatically in China due to rapid agricultural, industrial and urban development. Therefore increasing N deposition in China and its ecological impacts are of great concern since the 1980s. This paper synthesizes the data from various published papers to assess the status of the anthropogenic Nᵣ emissions and N deposition as well as their impacts on different ecosystems, including empirical critical loads for different ecosystems. Research challenges and policy implications on atmospheric N pollution and deposition are also discussed. China urgently needs to establish national networks for N deposition monitoring and cross-site N addition experiments in grasslands, forests and aquatic ecosystems. Critical loads and modeling tools will be further used in Nᵣ regulation.
اظهر المزيد [+] اقل [-]Assessing the relationship between global warming and mortality: Lag effects of temperature fluctuations by age and mortality categories النص الكامل
2011
Yu, Weiwei | Mengersen, Kerrie | Hu, Wenbiao | Guo, Yuming | Pan, Xiaochuan | Tong, Shilu
Although interests in assessing the relationship between temperature and mortality have arisen due to climate change, relatively few data are available on lag structure of temperature–mortality relationship, particularly in the Southern Hemisphere. This study identified the lag effects of mean temperature on mortality among age groups and death categories using polynomial distributed lag models in Brisbane, Australia, a subtropical city, 1996–2004. For a 1 °C increase above the threshold, the highest percent increase in mortality on the current day occurred among people over 85 years (7.2% (95% CI: 4.3%, 10.2%)). The effect estimates among cardiovascular deaths were higher than those among all-cause mortality. For a 1 °C decrease below the threshold, the percent increases in mortality at 21 lag days were 3.9% (95% CI: 1.9%, 6.0%) and 3.4% (95% CI: 0.9%, 6.0%) for people aged over 85 years and with cardiovascular diseases, respectively. These findings may have implications for developing intervention strategies to reduce and prevent temperature-related mortality.
اظهر المزيد [+] اقل [-]The effect of atmospheric thermal conditions and urban thermal pollution on all-cause and cardiovascular mortality in Bangladesh النص الكامل
2011
Burkart, Katrin | Schneider, Alexandra | Breitner, Susanne | Khan, Md. Mobarak Hossain | Krämer, Alexander | Endlicher, Wilfried
This study assessed the effect of temperature and thermal atmospheric conditions on all-cause and cardiovascular mortality in Bangladesh. In particular, differences in the response to elevated temperatures between urban and rural areas were investigated. Generalized additive models (GAMs) for daily death counts, adjusted for trend, season, day of the month and age were separately fitted for urban and rural areas. Breakpoint models were applied for determining the increase in mortality above and below a threshold (equivalent) temperature. Generally, a ’V’-shaped (equivalent) temperature–mortality curve with increasing mortality at low and high temperatures was observed. Particularly, urban areas suffered from heat-related mortality with a steep increase above a specific threshold. This adverse heat effect may well increase with ongoing urbanization and the intensification of the urban heat island due to the densification of building structures. Moreover, rising temperatures due to climate change could aggravate thermal stress.
اظهر المزيد [+] اقل [-]Effects of compositional heterogeneity and nanoporosity of raw and treated biomass-generated soot on adsorption and absorption of organic contaminants النص الكامل
2011
Chen, Baoliang | Huang, Wenhai
A biomass-generated soot was sequentially treated by HCl-HF solution, organic solvent, and oxidative acid to remove ash, extractable native organic matter (EOM), and amorphous carbon. The compositional heterogeneity and nano-structure of the untreated and treated soot samples were characterized by elemental analysis, thermal gravimetric analysis, BET-N₂ surface area, and electron microscopic analysis. Sorption properties of polar and nonpolar organic pollutants onto the soot samples were compared, and individual contributions of adsorption and absorption were quantified. The sorption isotherms for raw sample were practically linear, while were nonlinear for the pretreated-soot. The removal of EOM enhanced adsorption and reduced absorption, indicating that EOM served as a partitioning phase and simultaneously masked the adsorptive sites. By drastic-oxidation, the outer amorphous carbon and the inner disordered core of the soot particles were completely removed, and a fullerene-like nanoporous structure (aromatic shell) was created, which promoted additional π–π interaction between phenanthrene and the soot.
اظهر المزيد [+] اقل [-]Contamination by arsenic and other trace elements of tube-well water along the Mekong River in Lao PDR النص الكامل
2011
Chanpiwat, Penradee | Sthiannopkao, Suthipong | Cho, Kyung Hwa | Kim, Kyoung-Woong | San, Vibol | Suvanthong, Boukeo | Vongthavady, Chantha
Arsenic and other trace element concentrations were determined for tube-well water collected in the Lao PDR provinces of Attapeu, Bolikhamxai, Champasak, Savannakhet, Saravane, and Vientiane. Water samples, especially from floodplain areas of central and southern Laos, were significantly contaminated not only with As, but with B, Ba, Mn, U, and Fe as well. Total As concentrations ranged from <0.5μgL⁻¹ to 278μgL⁻¹, with over half exceeding the WHO guideline of 10μgL⁻¹. 46% of samples, notably, were dominated by As(III). Samples from Vientiane, further north, were all acceptable except on pH, which was below drinking water limits. A principal component analysis found associations between general water characteristics, As, and other trace elements. Causes of elevated As concentrations in Lao tube wells were considered similar to those in other Mekong River countries, particularly Cambodia and Vietnam, where young alluvial aquifers give rise to reducing conditions.
اظهر المزيد [+] اقل [-]Ethylenediurea (EDU): A research tool for assessment and verification of the effects of ground level ozone on plants under natural conditions النص الكامل
2011
Manning, William J. | Paoletti, Elena | Sandermann, Heinrich, Jr | Ernst, Dieter
Ethylenediurea (EDU) has been widely used to prevent ozone (O₃) injury and crop losses in crop plants and growth reductions in forest trees. Successful use requires establishing a dose/response curve for EDU and the proposed plant in the absence of O₃ and in the presence of O₃ before initiating multiple applications to prevent O₃ injury. EDU can be used to verify foliar O₃ symptoms in the field, and to screen plants for sensitivity to O₃ under ambient conditions. Despite considerable research, the mode of action of EDU remains elusive. Additional research on the mode of action of EDU in suppressing O₃ injury in plants may also be helpful in understanding the mode of action of O₃ in causing injury in plants.
اظهر المزيد [+] اقل [-]Outdoor and indoor cadmium distributions near an abandoned smelting works and their relations to human exposure النص الكامل
2011
Spurgeon, David J. | Lawlor, Alan | Hooper, Helen L. | Wadsworth, Richard | Svendsen, Claus | Thomas, Laura D.K. | Ellis, James K. | Bundy, Jacob G. | Keun, Hector C. | Jarup, Lars
The relationship of measured or modelled Cd concentrations in soil, house dust and available to plants with human urinary Cd concentrations were assessed in a population living around a Cd/Pb/Zn smelter in the UK. Modelled air concentrations explained 35% of soil Cd variation indicating the smelter contributed to soil Cd loads. Multi-variate analysis confirmed a significant role of biological and life-style factors in determining urinary Cd levels. Significant correlations of urinary Cd with soil, house dust and modelled plant available Cd concentrations were not, however, found. Potential reasons for the absence of clear relationships include limited environmental contact in urban populations; the role of undefined factors in determining exposure; and the limited spatial scope of the survey which did not sample from the full pollution gradient. Further, the absence of any significant relationship indicates that environmental measures provide limited advantage over atmospheric model outputs for first stage human exposure assessment.
اظهر المزيد [+] اقل [-]Combined effects of titanium dioxide and humic acid on the bioaccumulation of cadmium in Zebrafish النص الكامل
2011
Hu, Xialin | Chen, Qiqing | Jiang, Lei | Yu, Zhenyang | Jiang, Danlie | Yin, Daqiang
The combined effects of titanium dioxide (TiO₂) nanoparticles and humic acid (HA) on the bioaccumulation of cadmium (Cd) in Zebrafish were investigated. Experimental data on the equilibrium Cd bioaccumulation suggest that only the dissolved Cd effectively contributed to Cd bioaccumulation in HA solutions whereas both the dissolved and TiO₂ associated Cd were accumulated in TiO₂ or the mixture of HA and TiO₂ solutions, due likely to the additional intestine uptake of the TiO₂-bound Cd. The equilibrium Cd bioaccumulation in the mixed system was comparable to that in the corresponding HA solutions, and significantly lower than that in the corresponding TiO₂ solutions (n = 3, p < 0.05). The presence of either HA or TiO₂ (5–20 mg L⁻¹) in water slightly increased the uptake rate constants of Cd bioaccumulation whereas combining HA and TiO₂ reduced the uptake rate constants.
اظهر المزيد [+] اقل [-]Contaminants in the coastal karst aquifer system along the Caribbean coast of the Yucatan Peninsula, Mexico النص الكامل
2011
Metcalfe, Christopher D. | Beddows, Patricia A. | Bouchot, Gerardo Gold | Metcalfe, Tracy L. | Li, Hongxia | Lavieren, Hanneke van
Intensive land development as a result of the rapidly growing tourism industry in the “Riviera Maya” region of the Yucatan Peninsula, Mexico may result in contamination of groundwater resources that eventually discharge into Caribbean coastal ecosystems. We deployed two types of passive sampling devices into groundwater flowing through cave systems below two communities to evaluate concentrations of contaminants and to indicate the possible sources. Pharmaceuticals and personal care products accumulated in the samplers could only have originated from domestic sewage. PAHs indicated contamination by runoff from highways and other impermeable surfaces and chlorophenoxy herbicides accumulated in samplers deployed near a golf course indicated that pesticide applications to turf are a source of contamination. Prevention and mitigation measures are needed to ensure that expanding development does not impact the marine environment and human health, thus damaging the tourism-based economy of the region.
اظهر المزيد [+] اقل [-]Responses of evergreen and deciduous Quercus species to enhanced ozone levels النص الكامل
2011
Calatayud, Vicent | Cerveró, Júlia | Calvo, Esperanza | García Breijo, Francisco José | Reig-Armiñana, José | Sanz, María José
Plants of one evergreen oak (Quercus ilex) and three deciduous oaks (Q. faginea, with small leaves; Q. pyrenaica and Q. robur, with large leaves) were exposed both to filtered air and to enhanced ozone levels in Open-Top Chambers. Q. faginea and Q. pyrenaica were studied for the first time. Based on visible injury, gas exchange, chlorophyll content and biomass responses, Q. pyrenaica was the most sensitive species, and Q. ilex was the most tolerant, followed by Q. faginea. Functional leaf traits of the species were related to differences in sensitivity, while accumulated ozone flux via stomata (POD₁.₆) partly contributed to the observed differences. For risk assessment of Mediterranean vegetation, the diversity of responses detected in this study should be taken into account, applying appropriate critical levels.
اظهر المزيد [+] اقل [-]