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排序方式: 共有82条查询结果,搜索用时 171 毫秒
51.
韩光辉 《中国人口.资源与环境》1997,7(3):25-29
水库区是水库水面与周边陆地的区域复合体。本文以山东大中型水库区为例,在调查研究的基础上,探讨了库区贫困的根源及库区脱贫的出路,并提出了库区发展的战略构想。 相似文献
52.
2011~2013年通过小区试验种植小白菜和萝卜,以再生水灌溉和污泥施肥,采用修正的BCR法测定了再生水、污泥、土壤、蔬菜中Zn的5种形态含量,分析Zn在再生水(污泥)-土壤-蔬菜体系中的迁移和累积特征。结果表明:2011~2013年水样中Zn含量均未超出国家《农田灌溉水质标准(GB5084—2005)》中Zn的标准。水样中水溶态B0比例较大。污泥中B0含量极少,残渣态B4含量较高。土壤中Zn的本底含量较少,经过3年的蔬菜种植和灌溉,土壤中Zn含量有增高的趋势。蔬菜中5种形态均有分布,地上部分中水溶态B0和可氧化态B3含量较高,地下部分中残渣态B4含量也较高。小白菜中Zn的含量高于萝卜。灌溉水中B0的含量对Zn在土壤和蔬菜中的迁移产生了较大影响。适当的再生水灌溉和污泥施肥可以改善土壤的缺Zn状况。 相似文献
53.
Effects of pore size and dissolved organic matters on diffusion of arsenate in aqueous solution 总被引:1,自引:0,他引:1
Presented here is the influence of membrane pore size and dissolved organic matters on the diffusion coefficient(D) of aqueous arsenate, investigated by the diffusion cell method for the first time. The p H-dependent diffusion coefficient of arsenate was determined and compared with values from previous studies; the coefficient was found to decrease with increasing p H, showing the validity of our novel diffusion cell method. The D value increased dramatically as a function of membrane pore size at small pore sizes, and then increased slowly at pore sizes larger than 2.0 μm. Using the Exp Assoc model, the maximum D value was determined to be 11.2565 × 10~-6cm~2/sec. The presence of dissolved organic matters led to a dramatic increase of the D of arsenate, which could be attributed to electrostatic effects and ionic effects of salts. These results improve the understanding of the diffusion behavior of arsenate, especially the important role of various environmental parameters in the study and prediction of the migration of arsenate in aquatic water systems. 相似文献
54.
Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(8):1311-1319
Protandry reflects the earlier arrival of males than females to the site of reproduction. Such protandry is hypothesised to
arise from sex differences in costs and benefits of early arrival. I investigated temporal patterns of arrival date of male
and female barn swallows Hirundo rustica and temporal patterns of selection to test the hypothesis that sex differences in selection account for sex differences in
arrival date. Mean arrival date of male barn swallows but not of females advanced during the last 33 years, giving rise to
an increasing sex difference in arrival date. Early arrival was favoured by increasingly better survival in males, while females
showed an opposite pattern that did not reach significance, although the effect differed between sexes. Early arrival increased
fecundity in both sexes equally.The sex difference in viability selection in relation to arrival date changed from positive
to negative as the degree of protandry increased in recent years, although there was no similar significant relationship for
fecundity selection. Furthermore, sex differences in viability selection in a given year affected the degree of protandry
in the following year through differential survival of certain phenotypes over others. Finally, temporal changes in sex difference
in viability selection and protandry were related to an increase in the interval between first and second clutches, as the
duration of the breeding season increased because of climatic amelioration. These findings suggest that arrival date is under
divergent selection in the two sexes, providing a mechanism for the evolution of protandry. 相似文献
55.
F. Lynn Carpenter Mark A. Hixon Robert W. Russell David C. Paton Ethan J. Temeles 《Behavioral ecology and sociobiology》1993,33(5):297-304
Summary Three age-sex classes of rufous hummingbirds (Selasphorus rufus) overlap temporally and defend feeding territories during migratory stopovers in the Sierra Nevada of California. We demonstrate that these classes differ in their ability to secure and maintain high-quality feeding territories for refueling, and that these differences result in differences in resource use. Data on acquisition of territories, territory characteristics, and responses of territory owners to intruders suggest that several mechanisms are involved in determining dominance, involving sex- and age-related differences in wing disc loading, coloration, and experience. We discuss the implications of these results for understanding intraspecific variation in migration strategies.
Correspondence to: F.L. Carpenter 相似文献
56.
Mrinal K. Ghose 《Environment, Development and Sustainability》2008,10(6):857-869
To achieve 8% growth of the Indian economy, the industrial sector must grow at 10% rate. The vision statements of various
core sectors of the country show that the mining sector will have to expand greatly. India is among the top ten mineral producing
nations in the world and the Indian mining industry indicates almost the full range of extractive mineral products. Small-scale
mining is quite prevalent in India. Such mines constitute about 90% of total number of mines, 42% of the total non-fuel minerals
and metals, 5% of the fuel minerals. Some 3,000 small-scale mines account for a work force of about 0.5 million people. Yet
this sector is a neglected sector in Indian economy and still considered as an unorganized sector. This article examines the
community and state interests in small-scale mining and the contribution of small-scale mines to employment, national mineral
production, practices, and Indian policy on small-scale mining. It identifies drawbacks in the existing Government policy
and discusses a possible role for the Government to upgrade the sector. This paper highlights the impacts of mining on women
community, the socioeconomic characteristics of women as miners and on the productive roles that women play in mining. It
also discusses how the pursuit of sustainable livelihoods, poverty alleviation, indigenous peoples right and gender equity
in artesianal and small-scale mining be more effective when these communities are disadvantaged or neglected by government
policies. The respective roles of the indigenous people and migrant workers in the social organization of ASM sectors in different
parts of the country are discussed.
Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
57.
Kim Broholm Peter R. Jrgensen Asger B. Hansen Erik Arvin Martin Hansen 《Journal of contaminant hydrology》1999,39(3-4)
The transport in macroporous clayey till of bromide and 25 organic compounds typical of creosote was studied using a large intact soil column. The organic compounds represented the following groups: polycyclic aromatic hydrocarbons (PAHs), phenolic compounds, monoaromatic hydrocarbons (BTEXs), and heterocyclic compounds containing oxygen, nitrogen or sulphur in the aromatic ring structure (NSO-compounds). The clayey till column (0.5 m in height and 0.5 m in diameter) was obtained from a depth of 1–1.5 m at an experimental site located on the island of Funen, Denmark. Sodium azide was added to the influent water of the column to prevent biodegradation of the studied organic compounds. For the first 24 days of the experiment, the flow rate was 219 ml day−1 corresponding to an infiltration rate of 0.0011 m day−1. At this flow rate, the effluent concentrations of bromide and the organic compounds increased very slowly. The transport of bromide and the organic compounds were successfully increased by increasing the flow rate to 1353 ml day−1 corresponding to 0.0069 m day−1. The experiment showed that the transport of low-molecular-weight organic compounds was not retarded relative to bromide. The high-molecular-weight organic compounds were retarded significantly. The influence of sorption on the transport of the organic compounds through the column was evaluated based on the observed breakthrough curves. The observed order in the column experiment was, with increasing retardation, the following: benzene=pyrrole=toluene=o-xylene=p-xylene=ethylbenzene=phenol=benzothiophene=benzofuran<naphthalene<1-methylpyrrole<1-methylnaphthalene=indole=o-cresol=quinoline<3,5-dimethylphenol=2,4-dimethylphenol<acridine<carbazole<2-methylquinoline<fluorene<dibenzofuran<phenanthrene=dibenzothiophene. This order could not be predicted from regularly characteristics as octanol/water-distribution coefficients of the organic compounds but only from experimentally determined data. The results indicate that a thin clayey till cover of the type described in this paper does not protect groundwater against contamination by low-molecular-weight organic compounds. 相似文献
58.
M. García Gutirrez J. Guimer A. Yllera de Llano A. Hernndez Benitez J. Humm M. Saltink 《Journal of contaminant hydrology》1997,26(1-4)
Tracer tests provide highly valuable information about the transport properties of saturated rocks which is essential to the characterization of a potential radioactive waste repository site. In the frame of El Berrocal project, a set of tracer tests was performed in a complex geometry of inclined boreholes, combined with highly fractured transmissive zones. The aims of the tracer test programme were to gain experience, knowledge and insight into field transport experiments. To achieve this a detailed programme of new instrumentation design, site characterization and laboratory tasks was developed. For field monitoring a new electronic system was developed. The system is able to measure up to 256 parameters per borehole, with surface equipment to control pumping rates and physical and chemical parameters at both injection and extraction boreholes. The experiments progressed from single borehole dilution tests under both natural flow and forced gradient conditions to convergent flow tracer tests. Dilution tests helped to discriminate the most suitable borehole sections at which to inject tracers. The tracers were selected by the results of the laboratory programme. Uranine (fluorescein), DTPA-gadolinium (diethylenetriaminopentacetic acid, gadolinium (III)), and deuterium were injected simultaneously in one borehole section and recovered at another borehole 20 m away, pumping at a flowrate of 0.1 1 min−1. First results showed a thickness porosity of 1.2 × 10−3 m and a longitudinal dispersivity of 17.0 m using uranine data acquired over a period of 4 d, at which point the recovery concentration had reached a maximum. However, gadolinium and deuterium appeared to travel faster, arriving at peak values after only 2 d of injection. 相似文献
59.
移民环境容量分析方法初探 总被引:2,自引:0,他引:2
提出预测区域环境容量的灰色线性规划模型,并用于岷江紫坪铺水库工程移民实际,对库区环境容量进行分析和评价,取得较好效果。 相似文献
60.
Shiwei Sun Shichang Kang Junming Guo Qianggong Zhang Rukumesh Paudyal Xuejun Sun Dahe Qin 《环境科学学报(英文版)》2018,30(6):130-142
The Tibetan Plateau(TP) is recognized as "Water Tower of Asia". Yet our understanding of mechanisms influencing incorporation of mercury(Hg) into freshwater in mountain glaciers on the TP remains quite limited. Extensive sampling of environmental matrices(e.g., snow/ice)were conducted on the East Rongbuk glacier on Mt. Everest and Zhadang glacier on Mt.Nyainqentanglha for Hg speciation analysis. Speciated Hg behaved quite different during snowmelt: a preferential early release of DHg(dissolved Hg) was observed at the onset of snowmelt, whereas PHg(particulate-bound Hg) and THg(total Hg) become relatively enriched in snow and released later. Small fraction of Hg in snow was lost during a snowmelt day(18.9%–34.7%) with a large proportion(58.1%–87.3%) contributed by PHg decrease, indicating that the deposited Hg is most likely retained in glacier snow/ice. Furthermore, THg were positively correlated with PHg and crustal major ions(e.g., Ca~(2+), Mg~(2+)) during snowmelt, indicating that Hg is mainly migrated with particulates. The main pathway of Hg loss during snowmelt was most probably associated with release of PHg with meltwater, which was greatly influenced by ablation intensity of snow/ice. This should be paid particular concern as Hg preserved in mountain glaciers will mostly enter aquatic ecosystem as climate warms, impacting on downstream ecosystems adversely. Obvious decrease of THg during the downstream transport from glacier was observed with a large proportion contributed by PHg decrease. The main removal mechanism of Hg was associated with sedimentation of PHg during the transport process. 相似文献