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41.
Broad relationships between weather and human health have long been recognized, and there is currently a large body of research examining the impacts of climate change on human health. Much of the literature in this area examines climate–health relationships at global or regional levels, incorporating mostly generalized responses of pathogens and vectors to broad changes in climate. Far less research has been done to understand the direct and indirect climate-mediated processes involved at finer scales. Thus, some studies simplify the role of climate and may over- or under-estimate the potential response, while others have begun to highlight the subtle and complex role for climate that is contingent on other relevant processes occurring in natural and social environments. These fundamental processes need to be understood to determine the effects of past, current and future climate variation and change on human health. We summarize the principal climate variables and climate-dependent processes that are believed to impact human health across a representative set of diseases, along with key uncertainties in these relationships.  相似文献   
42.
The impacts of urbanization on soil erosion in the Loess Plateau region   总被引:1,自引:0,他引:1  
The accelerated urbanization has resulted in new soil erosion in the Loess Plateau region since the 1980s. A concept of urban erosion and its impacts on environment are discussed. The experimental studies and field investigations show that those loose silt and earth piles formed by urban construction can be eroded seriously: Under stormy rain, the amount of sediment from steep man-dumped slope is 10.8-12.2 times that of from uncovered slope land; the result of experiments with the wind tunnel also shows that the damage to the surface structure of dry loess can cause serious soil erosion by wind in some cities of the region. Even if in the urban built-up area, there are many loose sandy soil, mud and silt, which are washed into rivers by city’s ground flow in the rainy season. So, anthropogenically induced soil erosion has made soil erosion more serious around the urban areas. And the urban eroded environment has several characteristics such as fragility, complexity, seasonality and quick variability. Urban areas witness a quick economic growth and have more construction projects than rural areas, which brings more intensive changes of environments during a short period of time or adds some new elements to the erosion system. Therefore erosion has experienced more intensive impact by human activities. So, the possible impact of urbanization on erosion environment must be taken into consideration when designing or planning to exploit natural resources or to develop urban areas in the Loess Plateau.  相似文献   
43.
Increased human activities since discovery of gold in northern California have changed the structure and function of many ecosystems. To reconstruct the changes in watershed environmental conditions, sediment cores were collected from three montane marshes in northern Sierra Nevada, CA. Pollen analysis was conducted, and water content, bulk density, ash, carbon, nitrogen, phosphorus, major cations, and lead concentrations of sediments were determined. Cores were dated by the 210Pb method. Pollen analyses showed changes in plant communities in this region due to severe logging in the late-1800s and moderate logging in the 1900s. The local changes were more clearly recorded in small marsh pollen profiles than regional changes. The water milfoil (Myriophyllum spicatum L.) introduction into Tahoe Basin was inferred from the pollen record and 210Pb dating. Road construction and maintenance activities were recorded in physical and chemical characteristics, such as increases in sodium, calcium, and magnesium concentrations. Pollen and physical and chemical records also documented the time line of the expansion of dry meadow, and the decrease of pine forest in one of the watersheds. This study showed that sediments in small marshes were especially useful to reconstruct local disturbance by human activities.  相似文献   
44.
Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km2), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for 100,000 localresidents. We retrieved a core that extends to about 1100 14Cyr BP. 210Pb ages, organic mater, CO3, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until 1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.  相似文献   
45.
河流梯级开发对生态环境影响的研究进展   总被引:4,自引:0,他引:4       下载免费PDF全文
河流梯级开发在满足社会需求的同时,还对区域生态环境具有一定的作用。针对河流水电开发对生态环境的影响,从河川流量、泥沙输移、水环境以及水生物等几个方面,将国内外的研究状况进行综合评述,并探讨了今后重点研究的几个方面:①如何应用可持续理念指导水资源开发与调度;②水利工程建设对河流水沙变化影响的量化研究;③失衡生态系统的自适应和自恢复机理研究;④水体富营养化最小临界流速研究;⑤如何通过水库联合调度,解决河流水电开发造成的环境胁迫问题的研究。  相似文献   
46.
In spite of raising Asian per capita food production by 27% and making India food self-sufficient, the Green Revolution has received much criticism for its environmental and socio-economic impacts. Taking on board post-development critiques of ‘speaking for’ Third World ‘others’, this paper seeks to examine the Green Revolution from the points of view of people directly affected by it. Comparative, historically-informed research in three villages for which 1972 baseline data exist reveal that the Green Revolution has ensured, in the words of one marginal farmer that ‘nobody sleeps with an empty stomach nowadays’. Most villagers associate the Green Revolution with increases in living standards and weakening community-based wealth hierarchies. Nevertheless, socio-economic inequalities between certain Scheduled Castes and other villagers are still very apparent.  相似文献   
47.
Although the principle of uniformitarianism may be applied to the Precambrian sedimentary record as a whole, certain periods of the Archaean and Palaeoproterozoic witnessed a changing pattern of prime influences controlling the depositional systems. This paper examines the major controls on sedimentation systems and environments during the Archaean and Palaeoproterozoic within the broader perspective of Earth evolution. Earth's earliest sedimentary system (4.4?-3.7 Ga) was presumably comprised of deep oceanic realms and probably influenced primarily by bolide impacts, major tsunamis, localized traction and global contour current patterns, and bathymetry. As continental crust began to form, the impact-dominated, tsunami type sedimentation gave way to wider varieties of sedimentary environments, known from the oldest sedimentary records. During early continental crustal evolution (c. 3.7–2.7 Ga), sedimentation was essentially of greenstone-type. Volcanic and volcaniclastic rocks were the major components of the greenstone belts, associated with thin carbonates, stromatolitic evaporites, BIF, pelites and quartzites and lesser synorogenic turbidites, conglomerates and sandstones. Volcanism and active tectonism (reflecting dynamic depositional settings during island arc and proto-continental nucleus formation) were the predominant factors influencing sedimentation during this phase of Earth evolution. Transgressions and regressions under the combined influence of tectonics and eustasy are reflected in fining- and coarsening-upwards successions from the proto-cratonic settings; low freeboard enabled the transgression to affect large areas of the proto-cratons. As the earliest, relatively stable craton formed, through a combination of plate tectonic and mantle-thermal processes, continents and supercontinents with the potential for supercontinental cycles started to influence sedimentation strongly. Major controls on Neoarchaean–Palaeoproterozoic sedimentation systems (2.7–1.6 Ga) were provided by a combination of superplume events and plate tectonics. Two global-scale ‘superevents’ at c. 2.7 Ga and c. 2.2–1.8 Ga were accompanied by eustatic rise concomitant with peaks in crustal growth rates, and large epeiric seas developed. The operation of first-order controls leading to development of vast chemical sedimentary platforms in these epeiric seas and concomitant palaeo-atmospheric and palaeo-oceanic evolution combined to provide a second-order control on global sedimentary systems in the Neoarchaean–Palaeoproterozoic period. The supercontinental cycle had become well established by the end of the Palaeoproterozoic, with the existence of large cratons across broad spectrums of palaeolatitude enabling erg development. The entire spectrum of sedimentary systems and environments came into existence by c. 1.8 Ga, prime influences on sedimentation and depositional system possibly remaining essentially uniform thereafter.  相似文献   
48.
Impacts of Coastal SST Variability on the East Asian Summer Monsoon   总被引:4,自引:0,他引:4  
The impacts of the seasonal and interannual SST variability in the East Asia coastal regions (EACRSST) on the East Asian summer monsoon (EASM) have been examined using a regional climate model (PδRCM9) in this paper. The simulation results show that the correlation between the EACRSST and the EASM is strengthened after the mid-1970s and also the variability of the EACRSST forcing becomes much more important to the EASM interannual variability after the mid-1970s. The impacts of the EACRSST on the summer precipitation over each sub-region in the EASM region become weak gradually from south to north, and the temporal evolution features of the summer precipitation differences over North and Northeast China agree well with those of the index of EASM (IEASM) differences.
The mechanism analyses show that different EACRSST forcings result in the differences of sensible and latent heat flux exchanges at the air-sea interface, which alter the heating rate of the atmosphere. The heating rate differences induce low level air temperature differences over East Asia, resulting in the differences of the land-sea thermal contrast (LSTC) which lead to 850 hPa geopotential height changes. When the 850 hPa geopotential height increases over the East Asian continent and decreases over the coast of East China and the adjacent oceans during the weakening period of weakens consequently. On the contrary, the EASM enhances during the strengthening period of the LSTC.  相似文献   
49.
《国际泥沙研究》2020,35(5):516-526
Heavy metal (HM) pollution in sediment is a serious concern particularly in developing nations, warranting an extensive survey to understand the current situation and propose possible remedial measures. This paper compiles the data of HMs cadmium (Cd), iron (Fe), cobalt (Co), manganese (Mn), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn) and nickel (Ni) in aquatic sediment from India from 1979 to 2017. It was found that mean values of Cu, Co, Zn, Pb, As, and Cr in Indian sediment were high in comparison to the Australian Interim Sediment Quality Guidelines, World Surface Rock Average, and the Threshold Effect Level for freshwater ecosystems. Anthropogenic activities, lithogenic factors, and sand intrusion are the main factors associated with HM pollution as observed using cluster analysis and principal component analysis. The results of contamination indices indicate that HM contamination ranged from average to high, in the sediment. The ecological risk assessment results showed that 11% HMs present very high risk. The cancer risk, due to the high contents of Cd, As, and Cr the ingestion pathway, showed high risk of cancer through food/water contaminated with sediment. At source reduction of HMs in industrial effluents by effluent treatment plants, and plantation of phytoremediating rooted macrophytes in sediment may help in HM mitigation of the sediment.  相似文献   
50.
旅游业的发展对丽江古城社会文化的影响   总被引:6,自引:0,他引:6  
旅游业的发展对旅游目的地的社会文化产生的影响是巨大的.丽江古城也遭受着同样的命运,这种影响集中表现在丽江古城功能的转变、社会网络的变迁和文化的涵化.这些影响都是由于旅游业的迅速发展引起的,而且还在加深.只有认识到以上的影响才能为下一步采取措施来控制这些影响提供前提保障.  相似文献   
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