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731.
Baptista MS Vasconcelos MT Cabral JP Freitas MC Pacheco AM 《Environmental pollution (Barking, Essex : 1987)》2008,151(2):408-413
This work aimed at comparing the dynamics of atmospheric metal accumulation by the lichen Flavoparmelia caperata and bark of Platanus hybrida over different periods of time. Transplants were exposed in three Portuguese coastal cities. Samples were retrieved (1) every 2 months (discontinuous exposure), or (2) after 2-, 4-, 6-, 8- and 10-month periods (continuous exposure), and analysed for Cu, Ni and Pb. Airborne accumulation of metals was essentially independent of climatic factors. For both biomonitors [Pb]>[Ni]>[Cu] but Pb was the only element for which a consistent pattern of accumulation was observed, with the bark outperforming the lichen. The longest exposure periods hardly ever corresponded to the highest accumulation. This might have been partly because the biomonitors bound and released metals throughout the exposure, each with its own dynamics of accumulation, but both according to the environmental metal availability. 相似文献
732.
Rush SA Borgå K Dietz R Born EW Sonne C Evans T Muir DC Letcher RJ Norstrom RJ Fisk AT 《Environmental pollution (Barking, Essex : 1987)》2008,153(3):618-626
To assess geographic distributions of elements in the Arctic we compared essential and non-essential elements in the livers of polar bears (Ursus maritimus) collected from five regions within Canada in 2002, in Alaska between 1994 and 1999 and from the northwest and east coasts of Greenland between 1988 and 2000. As, Hg, Pb and Se varied with age, and Co and Zn with gender, which limited spatial comparisons across all populations to Cd, which was highest in Greenland bears. Collectively, geographic relationships appeared similar to past studies with little change in concentration over time in Canada and Greenland for most elements; Hg and Se were higher in some Canadian populations in 2002 as compared to 1982 and 1984. Concentrations of most elements in the polar bears did not exceed toxicity thresholds, although Cd and Hg exceeded levels correlated with the formation of hepatic lesions in laboratory animals. 相似文献
733.
Atmospheric radioactivity is monitored for the verification of the Comprehensive Nuclear-Test-Ban Treaty, with xenon isotopes 131mXe, 133Xe, 133mXe and 135Xe serving as important indicators of nuclear explosions. The treaty-relevant interpretation of atmospheric concentrations of radioxenon is enhanced by quantifying radioxenon emissions released from civilian facilities. This paper presents the first global radioxenon emission inventory for nuclear power plants, based on North American and European emission reports for the years 1995–2005. Estimations were made for all power plant sites for which emission data were unavailable. According to this inventory, a total of 1.3 PBq of radioxenon isotopes are released by nuclear power plants as continuous or pulsed emissions in a generic year. 相似文献
734.
Dragutin T. Mihailovic Kiran Alapaty Zorica Podrascanin 《Environmental science and pollution research international》2009,16(2):144-151
Background, aim, and scope Improving the parameterization of processes in the atmospheric boundary layer (ABL) and surface layer, in air quality and
chemical transport models. To do so, an asymmetrical, convective, non-local scheme, with varying upward mixing rates is combined
with the non-local, turbulent, kinetic energy scheme for vertical diffusion (COM). For designing it, a function depending
on the dimensionless height to the power four in the ABL is suggested, which is empirically derived. Also, we suggested a
new method for calculating the in-canopy resistance for dry deposition over a vegetated surface.
Materials and methods The upward mixing rate forming the surface layer is parameterized using the sensible heat flux and the friction and convective
velocities. Upward mixing rates varying with height are scaled with an amount of turbulent kinetic energy in layer, while
the downward mixing rates are derived from mass conservation. The vertical eddy diffusivity is parameterized using the mean
turbulent velocity scale that is obtained by the vertical integration within the ABL. In-canopy resistance is calculated by
integration of inverse turbulent transfer coefficient inside the canopy from the effective ground roughness length to the
canopy source height and, further, from its the canopy height.
Results This combination of schemes provides a less rapid mass transport out of surface layer into other layers, during convective
and non-convective periods, than other local and non-local schemes parameterizing mixing processes in the ABL. The suggested
method for calculating the in-canopy resistance for calculating the dry deposition over a vegetated surface differs remarkably
from the commonly used one, particularly over forest vegetation.
Discussion In this paper, we studied the performance of a non-local, turbulent, kinetic energy scheme for vertical diffusion combined
with a non-local, convective mixing scheme with varying upward mixing in the atmospheric boundary layer (COM) and its impact
on the concentration of pollutants calculated with chemical and air-quality models. In addition, this scheme was also compared
with a commonly used, local, eddy-diffusivity scheme. Simulated concentrations of NO2 by the COM scheme and new parameterization of the in-canopy resistance are closer to the observations when compared to those
obtained from using the local eddy-diffusivity scheme.
Conclusions Concentrations calculated with the COM scheme and new parameterization of in-canopy resistance, are in general higher and
closer to the observations than those obtained by the local, eddy-diffusivity scheme (on the order of 15–22%).
Recommendations and perspectives To examine the performance of the scheme, simulated and measured concentrations of a pollutant (NO2) were compared for the years 1999 and 2002. The comparison was made for the entire domain used in simulations performed by
the chemical European Monitoring and Evaluation Program Unified model (version UNI-ACID, rv2.0) where schemes were incorporated. 相似文献
735.
Integrated water management of the Brahmaputra basin: Perspectives and hope for regional development
Water is strongly linked with the overall development framework of the Brahmaputra basin. However, the absence of integrated management of Brahmaputra water resources and lack of coordination among the riparian states constitutes an ongoing threat to future development plans within the basin. Brahmaputra's abundant hydropower potential can help give riparian countries a safer energy future that is the key driving force behind the prospect of potential cooperation. This paper analyses the current status of Brahmaputra water resources and identifies the perspectives of riparian countries regarding the development of the Brahmaputra basin. It also identifies the opportunities for cooperation and regional development through integrated water development and management of the Brahmaputra basin. It is essential to develop an integrated water resources management approach involving all riparians to foster regional development and overcome the prospect of severe water conflict along the Brahmaputra basin. 相似文献
736.
汽油无铅化的关联问题 总被引:4,自引:1,他引:4
在实施汽油无铅化的过程中,一个值得引起重视的问题是,要防止“污染替代”发生,即在消除铅污染的同时,防止另一些对环境和健康构成严重威胁的污染物被引入。该文在调研大量中外文献的基础上,综述了目前研究较多的苯、芳烃、烯烃、甲基叔丁基醚等汽油组成和汽油蒸气压对汽车排放正、负方面的影响,提出了制定汽油燃料环保标准,汽油无铅化和安装催化转化器同步进行等建议。 相似文献
737.
通过建立大气环境容量的数学模型测算出城区大气环境容量,以此为依据提出各功能区及各污染源污染物排放量的分配方案,达到充分开发和合理利用大气环境资源;根据现有和未来主要行业发展特点,确定控制的主要污染项目,为政府决策提供科学依据,达到为我市今后经济可持续发展服务的目的。 相似文献
738.
南京台数字水准仪往返观测误差分析 总被引:1,自引:0,他引:1
2006年初,省局给台站更换了DiNi12数字化水准仪,通过近几个月观测,观测数据测线观测数据上午往测观测高差偏大,下午返测观测高差偏小的现象,经分析认为:造成这种现象的主要原因与仪器受温度、太阳光照射影响有关. 相似文献
739.
740.
贵州农用地土壤在长期的耕作过程中,承载大量的重金属污染物,影响土壤质量。采集了贵州东部、南部、中部、北部主要农业非点源重金属污染区土壤样品进行检测。结果表明,贵州农业非点源重金属污染物主要是Hg、Pb,贵州省农业非点源污染土壤中重金属累积污染程度Hg>Pb>Cd>As>Cr。各地区污染物种类和程度不同,重金属As污染为中部地区较高,农业土壤Hg、Pb污染主要集中在中部和东部地区,Cd污染主要发生在南部区域。 相似文献