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排序方式: 共有349条查询结果,搜索用时 281 毫秒
291.
292.
Claude Schummer Elodie Mothiron Anne-Laure Rizet Maurice Millet 《Environmental pollution (Barking, Essex : 1987)》2010,158(2):576-8129
Atmospheric samples have been collected in Strasbourg between April 18 and May 29, 2007 and were analyzed for 71 current-use pesticides, of which 38 were detected. Average concentrations ranged from 0.09 ng m−3 for Fenarimol to 110.42 ng m−3 for Dimethachlor, which was slightly higher than the concentrations reported from other, comparable agricultural regions.Significant temporal variations were observed for 30 pesticides, and for most of them it could be shown that these were linked to time, temperature or atmospheric pressure. In several cases this helped to identify pesticide application just before or at the beginning of the sampling period, or ongoing treatment. Humidity, in contrast to previous reports, could not be linked to these variations. For the other 8 pesticides, only very little temporal variations were observed. Generally, these concentrations were low (less than 1 ng m−3), and it was assumed that they are not in use in Alsace at present. 相似文献
293.
294.
青岛近岸海域二甲基硫排放和大气中二甲基硫浓度变化 总被引:7,自引:1,他引:6
为研究我国受人为干扰严重的近岸海域DMS排放规律,利用固体吸附-解吸的富集采样方法和冷却预浓缩的分析方法,分别在2001年夏秋季和2002年春秋季,对青岛近岸海域海水和大气中的二甲基硫进行了采样和分析.结果表明,海水中DMS浓度和海气排放通量呈现明显的空间分布和季节变化.夏季,青岛近岸的海水DMS平均浓度最高,达1169.47 ng·L-1;春季最低,只有226.99 ng·L-1.河口区、风景旅游区和奥运赛场区在夏季有显著的从高到低的浓度梯度变化,而春秋季不明显.DMS海气排放通量主要由海水浓度决定,因此两者呈现一致的变化规律.海洋大气中的DMS也呈现夏季较高(256.44 ng·m-3),秋季较低(195.64 ng·m-3)的季节变化.文中还初步探讨了大气DMS的日变化情况. 相似文献
295.
Lake Sapanca is exposed to heavy urbanization and industrialization because of its natural beauty and its proximity to the
metropolitan İstanbul, Turkey. In this study, it was aimed to investigate seasonal changes of some heavy metals (Pb, Cr, Cu,
Mn, Ni, Zn and Cd) concentration of surface sediment. Nine different stations were chosen as sampling points. Samples were
taken every three months and the seasonal and annual average concentration of the elements were determined. Seasonal highest
values of heavy metals were observed as follows; Cr, Cu, Mn, Ni and Zn in Summer, Cd in Autumn. There was no seasonal difference
for Pb, Cr and Cd. It seems that Lake Sapanca has not been polluted yet. However, it was found that Cu and Ni concentrations
in surface sediment exceed lowest effect level. 相似文献
296.
The spring waters of Tuzla–Icmeler are on the Marmara Sea coast in Tuzla town of Istanbul city. The springs discharge a natural
sodium chloride mineral water that consumed for ages for therapeutic purposes attributed to their chemical properties. Development
of springs commenced during the Ottoman times and a surface collection structure was built at the discharge point of the main
spring. Two deep wells were drilled to tap mineral water within the past decades. The bottled water of these springs is also
sold for a couple of years and its consumption as a beverage is increasing. The geochemical properties of these springs were
investigated by several researchers in the past. This study comprises geochemical and geophysical measurements performed between
July 2001 and July 2002 in order to construct a conceptual hydrogeological model for environmental and land use planning purposes.
The seasonal evaluation of Tuzla–Icmeler (mineral spring) shows that the chemical properties fluctuate from the beginning
of summer until the beginning of winter. This indicates that the overdraft of water during the summer season causes the movement
and mix of normal groundwater with the mineralized groundwater. As a result, mixing of less mineralized groundwater decreases
the salinity of mineralized groundwater. Using the site-specific hydrogeological, geochemical and geophysical data, zones
of protection areas were delineated in order to prevent a possible pollution access to the springs and surroundings from nearby
dockyards, dwellings and vehicle traffic. For this purpose, a new land use plan was proposed using the existing settlement
sustainability plans. 相似文献
297.
Isoprene is a dominant constituent of the global biogenic volatile organic compounds budget. It plays an important role in
regulating the atmospheric trace gas composition including tropospheric ozone concentrations. In this study, monthly measurements
of isoprene emission rates were carried out over a 1-year period (December 2002–November 2003) from four Indian deciduous
tree species, namely Ficus relegiosa, Ficus infectoria, Pongamia pinnata, and Morus alba, using branch enclosure method. Significantly high monthly variations in isoprene emission rates were observed in all four-plant
species. Also, each plant species exhibited pronounced seasonal variation in isoprene emission. Maximum isoprene emissions
were observed during summer and minimum during the winter or spring months. 相似文献
298.
Simultaneous ground-based measurements of ozone and carbon monoxide were performed at Oki, Japan, from January 2001 to September 2002 in order to investigate the O(3) and CO characteristics and their distributions. The observations revealed that O(3) and CO concentrations were maximum in springtime and minimum in the summer. The monthly averaged concentrations of O(3) and CO were 60 and 234 ppb in spring and 23 and 106 ppb in summer, respectively. Based on direction, 5-day isentropic backward trajectory analysis was carried out to determine the transport path of air masses, preceding their arrival at Oki. Comparison between classified results from present work and results from the year 1994-1996 was carried out. The O(3) and CO concentration results of classified air masses in our analysis show similar concentration trends to previous findings; highest in the WNW/W, lowest in N/NE and medium levels in NW. Moreover, O(3) levels are higher and CO levels are lower in the present study in all categories. 相似文献
299.
渤海和北黄海有色溶解有机物(CDOM)的分布特征和季节变化 总被引:1,自引:0,他引:1
采集了2016年的4、8、12月和2017年2月渤海和北黄海表、中、底海水样品,分析了海水中有色溶解有机物(CDOM)的紫外-可见光吸收光谱和三维荧光光谱,探讨了渤海和北黄海海域CDOM的分布特征、影响因素和季节变化.结果表明,不同季节CDOM分布相似,呈近岸高、远海低的分布特征.吸收系数a(355)和光谱斜率S275-295呈显著负相关,说明CDOM受到陆源输入的显著影响.垂直分布上,8月,受强烈的光降解作用影响,表层CDOM含量最低. 2月,底层CDOM含量最低,这可能与受光照影响的初级生产力在水下分布不均匀有关.从2016年4月~2017年2月,CDOM含量先上升后下降,12月含量最高,2月含量最低. CDOM的季节变化主要受陆源输入和浮游植物生物量的季节变化控制.以光谱斜率S275-295表征CDOM的平均分子量,2月由于陆源输入最少,CDOM平均分子量最小.夏季光降解强烈,将部分大分子量有机物降解成小分子量有机物,小分子量有机物增加,因此,8月CDOM的平均分子量小于4月和12月. 相似文献
300.
In this study, a denitrification (DN)–partial nitritation (PN)–anaerobic ammonia oxidation (Anammox) system for the efficient nitrogen removal of mature landfill leachate was built with a zone-partitioning self-reflux biological reactor as the core device, and the effects of changes in seasonal temperature on the nitrogen removal in non-temperature-control environment were explored. The results showed that as the seasonal temperature decreased from 34°C to 11.3°C, the total nitrogen removal rate of the DN-PN-Anammox system gradually decreased from the peak value of 1.42 kg/(m3?day) to 0.49 kg/(m3?day). At low temperatures (<20°C), when the nitrogen load (NLR) of the system is not appropriate, the fluctuation of high NH4+-N concentration in the landfill leachate greatly influenced the stability of the nitrogen removal. At temperatures of 11°C–15°C, the NLR of the system is controlled below 0.5 kg/(m3?day), which can achieve stable nitrogen removal and the nitrogen removal efficiency can reach above 96%. The abundance of Candidatus Brocadia gradually increased with the decrease of temperature. Nitrosomonas, Candidatus Brocadia and Candidatus Kuenenia as the main functional microorganisms in the low temperature. 相似文献