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排序方式: 共有3397条查询结果,搜索用时 838 毫秒
331.
陈祖义 《生态与农村环境学报》2005,21(4):72-73
论述了稀土元素在动物脑部的蓄积性、对脑的毒性以及稀土区人群的脑部毒性效应,分析了稀土农业应用和稀土厂“三废”对生态环境和人群健康的潜在危害。 相似文献
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1 IntroductionAseveryoneknown ,chelatingresincontainingheteroatomsuchassulfur,nitrogen ,andoxygenpossessexcellentadsorptionandselectivitypropertiesformetalions,especiallyfornoblemetallicions.Therefore ,manyeffortshavebeendonetopreparetheabove mentionedre… 相似文献
335.
生态环境质量物元可拓评价及实例分析 总被引:15,自引:0,他引:15
生态环境质量评价属于环境质量评价的重要方面。为了探索建立生态环境质量评价的方法,尝试运用物元可拓的方法来建立生态环境质量评价模型,并且通过用该方法对土壤生态环境质量评价实例验证物元可拓方法的可行性,得到该土壤生态环境质量评价等级值为3.73。从而为尚处在探索发展阶段的生态环境质量评价方法提供一种新思路。 相似文献
336.
Length of maternal care, i.e. the interval between successfully raised litters, is the most important factor explaining the variation in reproductive rate among brown-bear (Ursus arctos) populations. In this paper, we examine the variation in length of maternal care in radio-marked brown bears and its effect on their offspring in northern Sweden. Young stayed with their mothers for 1.4–1.5 or 2.4–2.5 (in one case 3.5) years and were weaned with body masses varying from 17 to 69 kg. The probability of yearling litters staying with their mother for a 2nd year increased with decreasing yearling body mass, and was higher for litters with two offspring than for litters with one or three to four offspring. Staying with their mothers for a 2nd year had a positive effect on mass gain in yearlings and this effect was more pronounced in litters with two than three to four offspring. Body mass of 2-year-olds was not related to age of weaning, suggesting that keeping offspring for an additional year mainly compensated for low yearling body mass. If large offspring body mass positively affects later offspring survival and reproduction, mothers may be able to optimize the length of maternal care according to the litter size and the size of their yearlings.Communicated by F. Trillmich 相似文献
337.
Urban Geochemistry: A Multimedia and Multielement Survey of a Small Town in Northern Europe 总被引:7,自引:0,他引:7
The concentrations and distributions of chemical elements (Ag, Al, As, Au, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, Tl, U, V, W and Zn) were studied in till, humus and urban soil in Jakobstad, a small town (20,000 inhabitants) in W. Finland. The analyses were performed with ICP-MS after aqua regia leaching of till (n = 37), urban topsoil (n = 32) and subsoil (n = 32), and HNO3 leaching of humus (n = 37). The till and humus samples, collected at the same sites, were divided into urban and rural samples. The urban till was not significantly enriched in metals. In contrast, a majority of the elements occurred in higher concentrations in the urban than the rural humus samples. Statistical and spatial interpretations of the humus data revealed that traffic (Pb, V and Ni), metal industry (Pb, Zn, Bi, Sb and Cr), an abandoned shooting range (Pb and Sb) and other sources contribute to higher metal levels in the urban humus. The urban soil samples were collected at parks, yards, abandoned industrial sites, roadsides, etc. The topsoil samples were enriched in most elements, also by elements not enriched in the urban humus (e.g. Cd). At several sites, the concentrations far exceeded the limit concentrations for contaminated soils in Finland. A large variety of sources were identified or indicated. 相似文献
338.
天津市土壤元素背景值的地域差异及成因分析 总被引:3,自引:0,他引:3
论述了天津土壤中Cu,Pb等13种微量元素背景值在行政区,土壤类型中的差异规律,并分析了引起元素背景值地域差异的原因。 相似文献
339.
污水土地处理磷污染物迁移转化模拟讨论分析 总被引:6,自引:0,他引:6
根据磷在土壤中的迁移转化机理,进行了以土柱试验为基础的“污水土地处理条件下磷的迁移转化模拟试验”,总结了污水中的磷在土壤中迁移转化的规律,提出了定量模拟这一规律的迁移转化联合模型。联合模型为研究磷在土壤中的运动提供了定量化依据,避免了已有研究中将迁移和转化割裂研究造成的误差,丰富并完善了不同形态磷的迁移转化模型。 相似文献
340.
Body mass is a consistent individual trait that characterises the state of adult birds and mammals and is positively related
with long-term reproductive success. However, whether and to what extent body mass changes over lifetime in long-lived birds
is poorly studied. In this paper, we investigate how individual body mass varies with age. Furthermore, we try to separate
possible effects of age and experience on body mass. This study was conducted in a Common Tern colony on the German Wadden
Sea coast. Transponders allowed registration of individuals throughout the breeding season and consecutive years with an antenna
system combined with electronic balances for recording individual body-mass changes within and between years. Individual body
masses of males and females were measured during three stages of the breeding season: at arrival, during incubation and chick
rearing when mass was lowest in both sexes. Individual-based longitudinal analyses clearly showed that body mass during arrival,
incubation and chick rearing increased up to an age of 5 or 6 years. First-time breeders had lower body mass than experienced
breeders. Experience had stronger effects on incubation mass than age. Recruiting age also affected body-mass development
of breeders: Three-year-old recruits showed a stronger increase in mass with experience than 4-year-old recruits. We assume
that increasing experience enables birds to cope better with the physiological challenge of reproduction. To explain the general
phenomenon of higher body mass in older birds, our results support the constraint hypothesis rather than either the selection
or restraint hypothesis. 相似文献