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41.
莱州湾东岸的海底地下水主要分布在浅海区的第四纪松散沉积物中,明显有别于海水,目前已被大量开采利用。从内陆向海区分别取地下水样化验分析,其pH值、密度、钠吸附比(SAR)、rCl/rBr等化学特征值呈现出从陆向海逐渐变化的规律,内陆含水层地下水中较高的硝酸盐类污染物,在海底地下水中也有明显的反映,地下水的水化学类型也由ClCa·Na·Mg型转变为ClNa·Mg型和ClNa型。另一方面,海底地下水的主要组分、浓度和矿物相组成也有自己的特点。研究发现,从内陆向海区,地下水的离子强度和矿物质的饱和指数均呈现出一定的变化规律。地下水中的这些离子以及矿物相在空间上的水岩交换变化,使地下水逐渐从淡水演化为微咸水和咸水,构成了海岸带地下水地球化学演化的一般模式。鉴于海底地下水与内陆地下水的紧密联系,今后陆地含水层一旦被污染,地下水向海区的化学输移将带来一定的环境效应。这应当引起我们足够的重视。  相似文献   
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In order to improve understanding of the fate of septic tank or individual sewage disposal system (ISDS) effluent in regolith overlying fractured-rock aquifers, effluent from an ISDS in such a setting was tracked via geophysical, hydrological, and geochemical methods. Under typical precipitation conditions, the effluent entered the fractured bedrock within 5 m of the boundary of the constructed infiltration area. During a period of unusually high spring recharge, the plume migrated between 50 and 100 m within the regolith before infiltrating the fractured bedrock. The chemical signature of the effluent is similar to that required to account for the decline in water quality, suggesting a causative relationship (as estimated from mass-balance models of the surface-water chemistry near the mouth of the basin). The elevated salt content of the effluent during periods of high natural recharge to the infiltration area correlates with elevated salt concentrations in surface and groundwater at the basin scale, suggesting that some of the effluent salt load may be stored in the unsaturated zone during dry periods and flushed during periods of elevated natural recharge.  相似文献   
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Migration and remittances characterise many small Pacific islands, where local livelihoods are limited, and the need for money has increased. A majority of Paamese have left the island of Paama, in the central island chain of Vanuatu, and more now live in the capital city, Port Vila, than on Paama. Remittances are bidirectional, between the island and Vila, a duality that has rarely been discussed in Melanesia. Almost every household on Paama and in Vila is involved in sending and receiving remittances. Remittances usually involve food: ‘modern’ foods (such as rice) flowing from Vila, and island foods (yams and laplap) travelling to Vila. While such transfers make little formal economic sense, they emphasise a constant process of negotiating and manipulating social relationships. Food, as an expression of identity and locality, is a powerful and repetitive reminder of moral obligations and rural–urban kinship connections. The material significance of exchange is thus less than its affective significance, within the field of reciprocity that structures kin relationships. Food and remittances have become metaphors for defining the experience of migration, as their meaning and function are more than to merely provide a source of nutrition. They have also become the means of structuring a translocal moral economy.  相似文献   
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This study explored the utility and performance of chironomid (Diptera: Chironomidae) autecology in the investigation of prehistoric farming impacts on freshwater lake systems. Chironomid subfossils, lake sediment geochemistry (δ13C, δ15N and C:N), pollen and macroscopic charcoal analyses were used in a comparative limnological assessment of three archaeologically rich study sites in northwest Ireland. At all three study sites, pastoral farming and its associated nutrient inputs, as represented by non-arboreal pollen indicative of grassland/pasture (NAPp) and lake sediment geochemistry, are concomitant with increases in eutrophic chironomid taxa. Redundancy analysis (RDA) and partial RDAs established that δ15N and NAPp were controlling factors of chironomid community compositional change during the Neolithic (4000–2500 BC) and Bronze Age (2500–600 BC). Bronze Age farming had a considerably greater impact on the lake systems than Neolithic farming, as indicated by a higher proportion of eutrophic taxa and increases in δ15N, C:N and δ13C values, consistent with increased erosion and agricultural inputs. Findings emphasise the importance of identifying the natural, pre-impacted state of a lake system to determine the extent of agricultural impact accurately. The timing and magnitude of change show that Neolithic and Bronze Age farming exhibited a strong control over chironomid communities at all three sites.  相似文献   
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The fossil diatom records preserved in radiometrically dated sediment cores from four shallow lakes in the Norfolk Broads, UK (Barton Broad, Rollesby Broad, Wroxham Broad and Upton Broad) were analysed. A weighted-averaging partial least squares (WA-PLS) diatom-total phosphorus (TP) transfer function, based on a training set of 152 mostly shallow (maximum depth < 3 m) lakes in northwest Europe, was applied to the full diatom dataset for each core to reconstruct the past TP concentrations of the lakes. Owing to the dominance of non-planktonic Staurosira, Pseudostaurosira and Staurosirella spp. (formerly classified in the genus Fragilaria) throughout the diatom records, the quantitative diatom inferred TP (DI-TP) concentrations did not adequately reflect the changes that occurred in the lakes as indicated by shifts in the other diatom taxa, or as reported in the literature. This was most apparent at Barton Broad and Rollesby Broad, where there was a marked increase in the importance of planktonic taxa associated with highly nutrient-rich waters but no increase in DI-TP. The modern and fossil data were thus square-root transformed to downweight the dominant taxa and the new transfer function was applied to the cores. An improvement was seen only in the reconstruction for Barton Broad. Finally, the Staurosira, Pseudostaurosira and Staurosirella spp. were removed from the modern and fossil diatom data, and the transfer function was re-applied. The trends in DI-TP became less clear, particularly for Upton Broad and Barton Broad, owing to a paucity of data for calibration once these taxa were deleted from the counts data. The problems associated with reconstructing trophic status and determining TP targets for restoration from fossil diatom assemblages in these systems are discussed.  相似文献   
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Summary The aim of this paper is to contribute towards a better understanding of the contemporary position of commons as a land resource, and to evaluate whether commons have a distinct role to play in today's 'post-productivist' countryside. Following the government's recent recognition of the multi-functional role of commons, the paper sets out to investigate whether this can be achieved through existing agri-environmental schemes. A case study of commons in the Cambrian Mountains (Wales) enables an assessment of the compatibility of one recent agri-environmental scheme, the ESA scheme, with commons management. It is concluded that new legislation and policy are needed, and that agri-environmental policy may provide an opportunity to develop a framework within which the management of common land can be improved to meet conservation and amenity as well as farming objectives.  相似文献   
48.
Summary A study of mean wind speeds and directions has been completed in the Snowy Range of Southern Wyoming, U.S.A. It was conducted in a subalpine ecosystem at an altitude of 3 200 m to 3 400 m above sea level during the summers of 1988 and 1989. Indexes of deformation and axes of asymmetry due to wind shaping of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) are related to wind speeds and directions on a 100 m × 100 m grid spacing over the 300 ha research site. Isotach and airflow patterns are drawn to represent climatological near-ground-level winds.A statistical analysis of the wind data and deformation indexes indicates that the indexes estimated independently by three of the authors were not significantly different at the F0.025 level. Two methods of calculating wind speeds were applied. At lower mean wind speeds in Engelmann spruce, results from the Wade-Hewson method were not significantly different from the Griggs-Putnam method at the F0.025 level. In slightly higher wind speeds in subalpine fir, the Wade-Hewson method produced significantly lower wind speeds than the Griggs-Putnam method.With 3 Figures  相似文献   
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Responding to China's major environmental challenges, researchers are increasingly exploring dynamics between international non-governmental organisations, the nation-state, and local communities. Much less understood are domestic environmental non-governmental organisations (eNGOs) and their interactions with actors across scales. This paper responds by exploring domestic eNGOs and interactions with institutional actors, including international donors, and with levels of Chinese government. The practices of eNGOs in China are influenced by interactions at various scales. Rather than being directly influenced by international partners and simply constrained by state regulations, Chinese eNGOs are embedded in more complex power relations. These interrelationships are exemplified in the operations of Green Watershed, a domestic eNGO working in Yunnan Province. Green Watershed has extensive interactions with international donors and various levels of government as a result of its national campaign and long-term local projects. Relationships between eNGOs’ international donors and the Chinese government are significant in influencing eNGO practice. NGO–government relations in China are inconsistent and constantly changing owing to the diverse interests and priorities of the various levels of government. The impacts of the local practice of Chinese eNGOs are deeply informed by their relationships both at and beyond the local level. Complex interrelationships make it difficult to achieve bottom-up, participatory resource management in China.  相似文献   
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