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11.
The Estuarine Quality Paradox, Environmental Homeostasis and the difficulty of detecting anthropogenic stress in naturally stressed areas 总被引:2,自引:0,他引:2
Estuaries have long been regarded as environmentally naturally stressed areas because of the high degree of variability in their physico-chemical characteristics, for example oxygen, temperature and salinity in the water column and bed sediment dynamics. However, their biota is well-adapted to cope with that stress and so the areas may be regarded as resilient because of that inherent variability; their ability to absorb stress without adverse effects is regarded here as Environmental Homeostasis. Hence these areas may only be regarded as stressful for marine or freshwater-adapted organisms and that for estuarine organisms this environmental stress is regarded as a subsidy whereby they successfully capitalise on the stressful conditions. In addition, using examples of the estuarine fauna and flora, this article indicates that the characteristics of natural stress in estuaries are similar to those for anthropogenic stress. An over-reliance on ecosystem structural features, such as diversity, in quality indicators therefore makes the detection of the anthropogenic stress more difficult. This difficulty is termed the Estuarine Quality Paradox. Because of these difficulties, the article argues that functional characteristics either as well as or rather than structural ones should be used in detecting environmental perturbations in estuaries. 相似文献
12.
Historically, the arid conditions of La Rioja, Argentina have been the main controlling factor in its development. The shortage
of surface water, which is fully used, makes groundwater a potential source for development. The government encouraged investment
in early 1979, resulting in a 20-fold increase of groundwater extraction by 1998 (0.076–1.450 m3/s, respectively) to cover related needs of agriculture, industry and population growth. This extraction created unjustified
uncertainties derived from negative results obtained in hydrological balances. However, a 0.5 m lowering of the water-table
surface was experienced. A knowledge of groundwater functioning was required to establish a reliable frame of reference for
development and, at the same time, to find possible scenarios of feasible economic activities in harmony with accessible water
resources and aptitude of the environment. The flow regime was found to be composed of three main systems: a regional, an
intermediate and several local. The intermediate system provides water for the extraction boreholes, and discharges naturally
in Salina La Antigua. From the chemical perspective the intermediate system has three groundwater groups. Group I has an outstanding
fluoride concentration (1.98–3.10 mg/l) defined to the north of the City of la Rioja and the highest temperature (26.8–33.0°C),
the lowest lithium content (0.029–0.059 mg/l) and moderate arsenic (≤0.038 mg/l). Group II has the moderate arsenic content
(≤0.38 mg/l) detected to the south of the City of La Rioja and high lithium (0.024–0.085 mg/l), Group III has the lowest TDS
(456–931 mg/l) and arsenic (0.007–0.012 mg/l) and the highest lithium (0.067–0.141 mg/l). to A regional flow is represented
by Group IV with one order of magnitude higher strontium (4.870 mg/l), lead (0.021 mg/l) and uranium (0.362 mg/l) content
than the other groups. Results provide evidence to eliminate several well-established hydro-myths such as “the boreholes are
getting dry” and “boreholes are getting saline water”. The aquifer (granular Tertiary and Quaternary material) thickness (≈750m)
was defined with the aid of the geological framework, geothermometers and Modflow modelling. The aquifer extent extends far
beyond the limits of the study area. Several economic activities were found to be feasible with available groundwater resources
and without bordening the environment (fish farming, bottled-water marketing, SPA activities and farming of endangered species). 相似文献
13.
利用微生物来降解土壤中的石油类污染物,是当前应用前景最好的土壤石油处理方法。多种因素同时制约着石油类污染物的生物降解。为了定量化各因素对彼此的影响,探求促进正向作用、抑制负向作用的途径,为各因素制定适宜的施用时间顺序以及施用量,以最大限度地加快降解速度,笔者设计了本文中的生物降解实验。结果表明,使用多因素复合处理方法可以在土壤石油处理中收到很好的效果;在实验的不同阶段,各影响因素的重要性及最优水平也会不同程度地变化。 相似文献
14.
In a recently published paper, Worm et al. [Impacts of biodiversity loss on ocean ecosystem services. Science 2006;314:787–90.] project “the global collapse of all taxa currently fished” by 2048. Using their criteria and data, this paper shows that the number of not-collapsed fisheries actually increased over time to a plateau of about 5600 in 1985–2003. Furthermore, if trends are projected into the future, more than half of the world's fisheries would always be in a recovered state. 相似文献
15.
Ta Liu 《中国地理科学(英文版)》1994,4(3):219-231
刘塔URBANRENEWALANDDEVELOPMENTOFSHANGHAICITY¥LiuTa(NanjingInstituteofGeographyandLimnology,theChineseAcademyofsciences,Nanjing2... 相似文献
16.
运用沉积学、地层学、板块构造学等学科理论,分析了临清坳陷晚古生代沉积特征,采用单因素分析多因素综合作图法进行岩相古地理编图,总结出其盆地演化特征。研究结果表明:临清坳陷晚古生代沉积类型主要包括障壁—潟湖沉积、潮坪沉积、碳酸盐岩台地沉积、河控浅水三角洲沉积及曲流河—湖泊沉积。编制5张岩相古地理图,分析发现:本溪期以潮坪相和碳酸盐岩台地相沉积为主;太原期以碳酸盐岩台地相、障壁—潟湖相以及潮坪相沉积为主;山西期以河控浅水三角洲相沉积为主;下石盒子期主要是曲流河道和泛滥平原沉积为主;上石盒子期主要以曲流河与湖泊沉积为主。研究区盆地演化可以划分为3个阶段:第1阶段为晚石炭世至早二叠的本溪期与太原期,主要是陆表海充填沉积阶段;第2阶段为过渡环境沉积充填阶段,即二叠世山西期;第3阶段为陆相环境沉积阶段,包括上石盒子和下石盒子期。 相似文献
17.
在综合研究分析金川铜镍矿区前人资料的基础上,经现场地质调查、收集地质资料,总结了矿区的成矿规律,有针对性地在Ⅰ矿区的北东侧开展了地质-地球电化学-地球物理多元信息的深部边部成矿预测。根据地电化学数据的统计结果,对矿区元素共生组合和成矿作用、成矿期次等地球化学特征进行了探讨,以此确定了地电化学综合异常;在掌握矿区岩石、矿石物性特征的情况下,通过地球物理勘探推测在Ⅰ号矿体与F1断裂之间存在一隐伏的超基性岩体。最终对矿区进行地质-地电化学-地球物理特征的综合分析,圈定了测区的找矿远景区。 相似文献
18.
《Limnologica》2016
Nutrient enrichment and changes in riparian tree species composition affect many streams worldwide but their combined effects on decomposers and litter decomposition have been rarely assessed. In this study we assessed the effects of experimental nitrogen (N) enrichment of a small forest stream on the decomposition of three leaf litter species differing in initial chemical composition [alder (Alnus glutinosa), chestnut (Castanea sativa) and poplar (Populus nigra)], incubated individually and in 2-species mixtures during late spring-early summer. To better understand the effects of litter mixing on litter decomposition, component litter species were processed individually for remaining mass and fungal reproductive activity. Litter decomposition rates were high. Nitrogen enrichment significantly stimulated litter decomposition only for alder incubated individually. Differences among litter treatments were found only at the N enriched site where the nutrient rich alder litter decomposed faster than all other litter treatments; only at this site was there a significant relationship between litter decomposition and initial litter N concentration. Decomposition rates of all litter mixtures were lower than those expected from the decomposition rates of the component litter species incubated individually, at the N enriched and reference sites, suggesting antagonistic effects of litter mixing. Conidial production by aquatic hyphomycetes for each sampling date was not affected by nutrient enrichment, litter species or mixing. Aquatic hyphomycetes species richness for each sampling date was higher at the N enriched site than at the reference site and higher for alder litter than for chestnut and poplar, but no effect of mixing was found. Aquatic hyphomycetes communities were structured by litter identity and to a lesser extent by N enrichment, with no effect of mixing. This study suggests that nutrient enrichment and litter quality may not have such strong effects on decomposers and litter decomposition in warmer seasons contrary to what has been reported for autumn-winter. Changes in the composition of the riparian vegetation may have unpredictable effects on litter decomposition independently of streams trophic state. 相似文献
19.
20.
We examine the contemporary denudation cycles in the steppes of Khakassia, including the phase of integration of matter in the system and of the nival-proluvial removal, and the deflation phase of long-range transport of matter from the Minusinskaya depression. The cartographic model for the contemporary functioning of denudation systems is presented. 相似文献