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511.
K.R. Spurny 《Environment international》1980,4(1):39-46
A size-selective procedure was developed for the preparation of fiber fractions of uniform size of chrysotile, crocidolite, amosite, and glass. The raw material was first ground to a suitable fineness, then suspended in liquids by ultrasonic agitation and separated by fiber diameter by means of slow sedimentation. The fractionation by fiber length was done by a vibrating sieve method. Fibrous aerosols of different size distributions could be prepared by using a vibrating bed aerosol generator. 相似文献
512.
This paper attempts to explain regional differences in fertility rates in the standard metropolitan statistical areas of the United States through socioeconomic factors and air pollution. An important feature of this study is that it uses the most recent data pertaining to a homogeneous sample of observations within a country rather than using data for different countries. Statistical results suggest that given other factors, fertility and the level of air pollution have an inverse relationship. This quantitative effect is statistically significant but the absolute impact is rather low. Our results also suggest that an increase in the level of income, relative education of females, temperature, and the availability of physicians would in the long run reduce fertility rates in the urban areas of the United States. 相似文献
513.
The significant processes controlling the fate of particulates are convection an dispersion on one hand, and sedimentation on the other hand. Due to inteparticulated reactions, larger aggregates can be formed from smaller units thus changing the sedimentation characteristics. These phenomena are summarized in a mathematical model whereby hydrodynamic effects as well as the control mechanisms of the dissolved phase are included. A relationship was derived on the basis of energy considerations leading to the formulation of a critical sedimentation velocity of the suspensa, which determines the transport capacity of the flowing system. The sedimentation term is calculated from the above discussed transport capacity, hydro-dynamic parameters and suspending media properties. Aggregation effects are taken into account as an increase of sedimentation velocities of the particles. The equations are solved in a particular computational routine such that the horizontal distribution of suspended solids in a natural system can be describe as function of the above discussed phenomena. The model was tested with in situ-measurements. It was found that the observed processes are described satisfactorily by this model. 相似文献
514.
Diesel exhaust particles were used to compare methods and techniques used in the preparation of particulate matter for microbial mutagenesis testing. Investigated in this study were extraction, concentration, and solvent exchange methodologies as they affected recovery of mutagenic material from diesel samples using a Salmonella typhimurium plate incorporation assay. Solvent removal methods applicable for use in determining the mass concentration of extracts were also evaluated. Results indicated that particle samples Soxhlet extracted with dichloromethane yielded higher levels of mutagenic activity than did comparative samples utilizing sonication. No difference was seen between rotary evaporation or Kuderna-Danish macro concentration of extracts to volumes > 50 mL. In comparison of micro concentration techniques to volumes < 10 mL, vortex evaporation was found to be more efficient than a modified micro Kuderna-Danish method in recovery of mass and mutagenicity. Solvent exchanged samples were found to yield higher recoveries of mutagenic activity than samples taken to dryness and then reconstituted in the bioassay solvent. A dry mass weighing procedure utilizing desiccation was found to be more acceptable than either the use of an infrared heat lamp or nitrogen blowdown for solvent removal. 相似文献
515.
S. Chidambaram R. Thilagavathi C. Thivya U. Karmegam M. V. Prasanna AL. Ramanathan K. Tirumalesh P. Sasidhar 《Environment, Development and Sustainability》2017,19(3):1015-1040
The occurrence of arsenic in drinking water and its detrimental effects have drawn much attention in recent years. Several studies have been conducted in the deltaic plains of River Ganga, NE part of the India, and in other countries, but no systematic study was conducted in South India on occurrence of arsenic in groundwater. The main aim of this study is to determine the level of arsenic in groundwater and to understand the relation with other geochemical parameters of groundwater in the south-eastern coastal aquifer at Kalpakkam region, India. This region is represented by three different lithologies, viz. charnockites, flood plain alluvium and marine alluvium. Twenty-nine representative samples of groundwater were collected and analysed for major ions, metals and isotopes such as 2H and 18O. In addition, geophysical method was also attempted to understand the subsurface condition. The spatial variation in arsenic (As) indicates that higher concentration was observed around the landfill sites and irrigated regions, which was supported by geochemical, statistical and isotopic inferences. The variation in the As with depth, lithology and sources has been clearly brought out. Though the values of As does not exceed the drinking water permissible limit (10 mg/l), it has reached a near permissible level of 8.7 ppb. Hence, it is essential to understand the geochemical behaviour of As for a proper future management of the water resource in the study area. 相似文献
516.
Stephanie K. H. Janssen Jan P. M. van Tatenhove Arthur P. J. Mol Henriëtte S. Otter 《Regional Environmental Change》2017,17(2):551-563
Greening flood protection (GFP) is increasingly recognized as an adaptive and flexible approach to water management that is well suited to addressing uncertain futures associated with climate change. In the last decade, GFP knowledge and policies have developed rapidly, but implementation has been less successful and has run into numerous barriers. In this paper, we address the challenge of realizing green flood protection goals by specifically considering knowledge in the decision-making of a Dutch flood protection project in Lake Markermeer. In this project, an ecological knowledge arrangement and a traditional flood protection knowledge arrangement are compared and their interactions analysed. The analysis provides insight into the specific difficulties of implementing GFP measures and identifies ways to realize GFP goals. The primary challenge is twofold: First, a self-reinforcing cycle of knowledge production and decision-making in the flood protection domain inhibits the introduction of innovative and multifunctional approaches such as GFP; second, the distribution of power is severely unbalanced in terms of ecological enhancement and flood protection, favouring the latter. Implementation of GFP requires structural change and the integration of ecological and flood protection knowledge and policy. Potentially rewarding routes towards this integration are the exploration of shared interests in GFP and the creation of mutual dependency between knowledge arrangements. The case study and the insights it provides show that GFP is far from mainstream practice and that implementation requires serious effort and courage to break with historical practices. 相似文献
517.
518.
M. L. Gitarskiy D. G. Zamolodchikov V. A. Mukhin V. A. Grabar D. K. Diyarova A. I. Ivashchenko 《Russian Journal of Ecology》2017,48(6):539-544
Studies in three typical forest biotopes of the Valdai Upland were performed to evaluate the stocks and surface area of coarse woody debris from spruce and birch (in linear transects), its colonization by xylotrophic fungi (during reconnaissance surveys), and CO2 emission (by a chamber method). The stock and surface area were minimum in a paludal birch forest (46.4 m3/ha and 960 m2/ha) and maximum in a decay area of spruce forest (256.1 m3/ha and 3761 m2/ha, respectively). The assemblages of wood-decay fungi had a composition typically found in southern taiga forests. The total CO2 flux varied from 145 kg C-CO2/ha per year in the paludal birch forest to 462 kg C-CO2/ha per year in small herb–green moss spruce forest. It is concluded that air temperature is an informative predictor of seasonal C-CO2 flux rate from coarse woody debris. 相似文献
519.
520.
Consideration is given to changes in the vegetation and climatic conditions on the eastern slope of the Northern Urals in the second half of the Holocene as reconstructed on the basis of integrated palynological, botanical, paleocarpological, and radiocarbon analysis of material from a peat bog section in the floodplain of the Loz’va River. The results show that the northern taiga zone of the study region in the period between approximately 5000 and 700 years BP was occupied by forests of southern taiga facies, as the climate was significantly warmer than it is today. 相似文献