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131.
Total mercury concentrations in different tissues of frigate tuna fish (Auxis thazard thazard) was determined by the cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer. A mixture
of HNO3, HClO4 and H2SO4 was used for complete oxidation of organic tissue. The concentration of mercury obtained was in the order Gills < Stomach
< Gonads < Intestine < Heart < Duodenum < Liver < Muscle. The concentration of total mercury detected in the edible muscle
tissue of the tuna fish tested ranged from 0.044 to 0.201 μg g−1 (mean = 0.108 μg g−1) wet weight. These levels are all within the maximum allowed/recommended level in fish (0.5 μg g−1 wet weight) set by the Food and Agriculture Organisation/World Health Organisation (FAO/WHO) and are therefore unlikely to
constitute any significant mercury exposure to the general population because of consumption of tuna fish. The results of
the study suggest a relatively clean marine environment that has not been significantly impacted by mercury contamination
probably due to minimal industrial activity in the region. 相似文献
132.
Guiling?L.?ZhangEmail author Jing?Zhang Jie?Xu Jingling?L.?Ren Sumei?M.?Liu 《Water, Air, & Soil Pollution: Focus》2007,7(6):645-654
CH4 concentrations in both the surface and bottom waters of Jiaozhou Bay were determined during four surveys in 2003, which showed
variability with both seasons and tidal cycles. Atmospheric fluxes of CH4 in Jiaozhou Bay showed obvious seasonal and spatial variations, with the highest values occurring in summer and the lowest
in winter. The annual emission of CH4 from Jiaozhou Bay was estimated to be . CH4 in the water column of Jiaozhou Bay was found to come from several land-sources including riverine water input, sewage water
input and groundwater input. The spatial and temporal variation in distributions and atmospheric fluxes of CH4 in Jiaozhou Bay was influenced mainly by the input of polluted river waters and the sewage effluents along the eastern coast,
which highlights the effects of human impacts on CH4 emission rates. 相似文献
133.
Ambient particles vary greatly in their ability to affect visibility, climate and human health. The fine fraction of aerosol
is responsible for greater and wider effects on human health; thus, investigation of this fraction is very important. Continuous
measurements of PM2.5 (particulate matter below 2.5 μm in size) concentrations at the Preila monitoring station started in
2003. During a period of 2 years, the episodes of high daily and semi-hourly concentrations of PM2.5 were measured. These
episodes did not depend on the season or time of day. The substantial role of long-range transport of pollutants to these
increases in concentration was shown using chemical and statistical analysis. It was found that most of the severe episodes
occurred when air masses came from a specific site besides it was established that air masses of different origin were characterized
by different mixing layer depth. Lower mixing depth was observed in air masses characterized by higher observed concentrations
at the measuring site and vice versa. PM2.5 concentrations showed diurnal and seasonal variations whose pattern reflected
the regional origin of the aerosol. The regional pollution level was evaluated by the statistical analysis of PM2.5 concentrations.
The background annual average of PM2.5 mass concentration for the eastern coast of the Baltic Sea was 15.1 ± 0.8 μg m−3. 相似文献
134.
Yazvenko SB McDonald TL Blokhin SA Johnson SR Meier SK Melton HR Newcomer MW Nielson RM Vladimirov VL Wainwright PW 《Environmental monitoring and assessment》2007,134(1-3):45-73
Exxon Neftegas Limited, operator of the Sakhalin-1 consortium, is developing oil and gas reserves on the continental shelf
off northeast Sakhalin Island, Russia. DalMorNefteGeofizika (DMNG), on behalf of the Sakhalin-1 consortium, conducted a 3-D
seismic survey of the Odoptu license area during 17 August–9 September 2001. A portion of the primary known feeding area of
the endangered western gray whale (Eschrichtius robustus) is located adjacent to the seismic block. The data presented here were collected as part of daily monitoring to determine
if there was any measurable effect of the seismic survey on the distribution and abundance of western gray whales. Mitigation
and monitoring program included aerial surveys conducted between 19 July and 19 November using the methodology outlined by
the Southern California High Energy Seismic Survey team (HESS). These surveys provided documentation of the distribution,
abundance and bottom feeding activity of western gray whales in relation to seismic survey sounds. From an operations perspective,
the aerial surveys provided near real-time data on the location of whales in and outside the feeding area, and documented
whether whales were displaced out of an area normally used as feeding habitat. The objectives of this study were to assess
(a) temporal changes in the distribution and abundance of gray whales in relation to seismic survey, and (b) the influence
of seismic survey, environmental factors, and other variables on the distribution and abundance of gray whales within their
preferred feeding area adjacent to Piltun Bay. Multiple regression analysis revealed a limited redistribution of gray whales
southward within the Piltun feeding area when the seismic survey was fully operational. A total of five environmental and
other variables unrelated to seismic survey (date and proxies of depth, sea state and visibility) and one seismic survey-related
variable (seg3d, i.e., received sound energy accumulated over 3 days) had statistically significant effects on the distribution and abundance
of gray whales. The distribution of two to four gray whales observed on the surface (i.e., about five to ten whales in total)
has likely been affected by the seismic survey. However, the total number of gray whales observed within the Piltun feeding
area remained stable during the seismic survey.
M. W. Newcomer, Deceased. 相似文献
135.
压入式局部通风工作面风流分布数值模拟研究 总被引:7,自引:1,他引:6
笔者应用三维k -ε紊流模型描述压入式局部通风工作面风流的流动过程 ,并采用控制容积法导出了描述流体流动方程的离散化方程式 ;用计算流体力学的方法求得了三维k -ε紊流模型的数值解。采用SIMPLE(压力耦合方程式的半阴解法 )算法解算流场 ;TDMA(三对角线算法 )和Gauss Seidel法结合通过线顺法求解离散方程。利用弱松弛法防止非线性方程组迭代求解过程中的发散现象 ,获得了掘进工作面空间的速度分布 ;并将模拟解算结果与在具有实际尺寸的拱形巷道模型中测得的实验结果进行了对比。数值计算结果与模型实验测定结果非常一致 ,验证了笔者的数学模型和数值模拟方法的正确性。 相似文献
136.
Within-nest temporal polyethism in the honey bee 总被引:1,自引:1,他引:0
Brian R. Johnson 《Behavioral ecology and sociobiology》2008,62(5):777-784
A well-regulated division of labor has been one of the core adaptations leading to the success of the social insects. Honeybee
division of labor has been classically viewed as a sequence of age-related changes in task performance. Kolmes questioned
this view arguing that his studies did not support the existence of any age-related within-nest specialization. To resolve
this controversy, Kolmes and Seeley conducted a joint study with mixed results. They found support for a cell cleaning caste,
but diverged on whether their results supported distinct nursing and middle age castes. In this paper, I follow up on their
work to resolve the question of caste number in within-nest honey bees. To determine whether nurses (typically aged 4–12 days)
and middle-aged bees (aged 12–20 days) have distinct task repertoires, I conducted focal animal observations on a large number
of workers in both age groups working within the same nests at the same time. The results support their being two castes of
within-nest bees. Young bees specialized on brood care tasks, while middle-aged bees specialized on nectar processing and
nest maintenance. Middle-aged bees were observed caring for brood in less than 1% of the observations. Moreover, both castes
exhibited movement patterns that correspond to the traditional view that nurses stay within the broodnest, while middle-aged
bees move around a great deal in search of work throughout the nest. A review of studies conducted since the debate of Seeley
and Kolmes supports the reliability of these results. This work has relevance for proximate models of temporal polyethism,
as it is often assumed by such models that there is only one within-nest caste in the honeybee. 相似文献
137.
土壤重金属来源及空间分布是土壤学及环境学研究的热点问题。地统计学是土壤元素空间变异研究的有效方法以昆山市土壤重金属分布为例,先利用多元回归分析方法,提取与重金属含量显著相关的因子,再利用协同克里格方法研究了土壤理化性质和土壤重金属含量的相互关系,最后比较协同克里格与普通克里空间预测的精度。研究表明Hg、As、Cu、Pb的精度分别提高了2.75%、2.13%、0.17%和0.43%,cr、Zn和Cd 3种元素空间预测精度没有显著提高。 相似文献
138.
139.
2012年6月13~14日对温州三垟湿地水质进行连续24h的采样监测,并运用对数型幂函数普适指数公式评价了监测站点1天内连续的水质变化情况。研究目的是揭示城市湿地水体中水质参数是否存在昼夜变化、昼夜变化的幅度大小和变化原因。结果表明:温度、pH、溶解氧、化学需氧量和叶绿素a表现出明显的昼夜变化,由于影响营养盐的因素复杂,营养盐指标没有表现出明显的昼夜变化。运用对数型幂函数普适指数公式评价监测站点的水质情况,评价结果显示在连续24h的实验中,水体的富营养化程度都处于"极富"营养状态而且呈现出白天营养状态综合指数下降,夜间升高的趋势。 相似文献
140.
Theoretical approaches, such as the Lotka-Volterra framework, enable predictions about long term species coexistence based on stability criteria, but generally assume temporal constancy of system equations and parameters. In real world systems, temporal variability may interfere with the attainment of stable states. Managed grassland ecosystems in Northwestern Europe experience structural periodic fluctuations in environmental conditions: the seasons. In addition, periodic disturbances such as cutting are very common. Here we show, using a Lotka-Volterra system applied to grassland species with empirically derived parameters, that seasonal variability can result in a time dependent equilibrium and redirection of displacement processes.Parameter estimates differed between species and - in most cases - between the seasons. As a result, five of the fifteen tested species combinations had different outcomes of species interactions between seasons. This indicates that systems remain in dynamic transience over the year as the equilibrium changes and the species composition of the system follows the equilibrium without ever attaining it. The non-attainment of the steady state enables coexistence of species even if there is competitive exclusion in one of the seasons. For three of the fifteen species combinations, cutting frequency affected the long-term coexistence patterns. Cutting resets the biomass of competing species and favours during regrowth those species that have a high growth rate, which can alter species coexistence in comparison to a Lotka-Volterra model without cutting. The Lotka-Volterra framework with seasonally changing empirical parameters predicts coexistence as a possible outcome of systems that in component seasons are characterised by exclusion, and vice versa. 相似文献