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排序方式: 共有133条查询结果,搜索用时 15 毫秒
41.
研究了光照和温度对菹草石芽萌发的影响及菹草的生长机理。结果表明:1在模拟秋冬季温度条件下不同光照强度对石芽萌发率的影响无规律性,即光照并未对菹草石芽的萌发起促进作用;2石芽在一定时间的低温作用后,恢复常温使石芽的萌发速度和萌发率明显提高,说明石芽的萌发受温度的影响,这也更好地解释了菹草的越冬生长习性及春季部分水体菹草大规模爆发的现象;3石芽随水面波动可吸附大量悬浮物,一般5-7天即可增加足够的重量下沉至水体底部,石芽吸附的悬浮物含有一定的营养成分,能促进石芽的萌发。石芽的萌发机制可为菹草石芽繁殖的影响因素研究提供依据,对栽培菹草具有重要的实践意义。 相似文献
42.
Retrieval of chlorophyll a and suspended solid concentrations by hyperspectral remote sensing in Taihu Lake, China 总被引:1,自引:0,他引:1
Chlorophyll α(ch1-α) and suspended solid concentrations are two frequently used water quality parameters for monitoring a lake. Traditional measurement of ch1-α and suspended solids, requiring laborious laboratory work, which is often expensive and time consuming. Hyperspectral remote-sensing measurement provides a fast and easy tool for estimating water trophic status. In situ hyperspectral data on March 7-8, July 6-7, September 20 and December 7-8, 2004 and the corresponding water chemical data were used to regress the algorithm of water quality parameters. Results showed that the peak of water leaving radiance around 700 nm (R700) varied proportionally with ch1-α concentration, and moved to infrared when algal bloom occurred. The reflectance ratio of R702/R685 was well correlated with ch1-α when water surface in no algal bloom case and the correlation coefficient was better if absorption of phycocyanin was considered. The reflectance ratio R620/R531 was highly correlated to the concentration of suspended solids. The relationship between suspended solids and other band groups were also compared. Secchi disk depth could be calculated by non-linear correlation with suspended solids concentration. 相似文献
43.
Electrogeochemical sampling with
Reinhard W. Leinz Donald B. Hoover David L. Fey David B. Smith Thaxson Patterson 《Journal of Geochemical Exploration》1998,61(1-3)
Electrogeochemical extraction methods are based on the migration of ions in an electric field. Ions present in soil moisture are transported by an applied current into fluids contained in special electrodes placed on the soil. The fluids are then collected and analyzed. Extractions are governed by Faraday's and Ohm's laws and are modeled by the operation of a simple Hittorf transference apparatus. Calculations show that the volume of soil sampled in an ideal electrogeochemical extraction can be orders of magnitude greater than the volumes used in more popular geochemical extraction methods, although this has not been verified experimentally.
is a method of in-situ electrogeochemical extraction that was developed in the former Soviet Union and has been tested and applied internationally to exploration for buried mineral deposits. Tests carried out at the United States Geological Survey (
) indicated that there were problems inherent in the use of
technology. The cause of the problems was determined to be the diffusion of acid from the conventional electrode into the soil. The
electrode incorporates two compartments and a salt bridge in a design that inhibits diffusion of acid and enables the collection of anions or cations. Tests over a gold-enriched vein in Colorado and over buried, Carlin-type, disseminated gold deposits in northern Nevada show that there are similarities and differences between
results and those by partial extractions of soils which include simple extractions with water, dilute acids and solutions of salts used as collector fluids in the electrodes. Results of both differ from the results obtained by total chemical digestion. The results indicate that
responds to mineralized faults associated with disseminated gold deposits whereas partial and total chemical extraction methods do not. This suggests that faults are favored channels for the upward migration of metals and that
may be more effective in exploration for the deposits. It defines anomalies that are often narrow and intense, an observation previously made by
researchers. The field tests show that
is less affected by surface contamination. A test over the Mike disseminated gold deposit indicates that the method may not be effective for locating deposits with impermeable cover. Faradaic extraction efficiencies of 20–30%, or more, are frequently achieved with
and the method generally shows good reproducibility, especially in extraction of major cations. However, ions of other metals that are useful in exploration, including Au and As, may be collected in low and temporally variable concentrations. The reason for this variability is unclear and requires further investigation. 相似文献
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44.
通过研究,发现在大样本(N=335)的情况下MODIS 500 mB1-B3与太湖悬浮物浓度具有较好的线性关系(R2=0.659)。同时,运用实测光谱深入分析悬浮物的敏感波段,进一步揭示了采用B1-B3估测的理论依据,并建立了适用于各个季节的太湖悬浮物通用遥感估测模型。 相似文献
45.
46.
Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry
and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO3 is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering
aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO4 and PO4 at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica,
relatively high (Na+K)/TZ+ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering
of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season,
reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive
correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite
is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water
favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher
than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting
that there is no pollution from these metals in Damodar River sediments.
Received: 21 January 1998 · Accepted: 4 May 1998 相似文献
47.
Danièle Valdes Jean-Paul Dupont Nicolas Massei Benoît Laignel Joël Rodet 《Comptes Rendus Geoscience》2005,337(15):1365-1374
In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005). 相似文献
48.
This study aims at determining the macroscopic strength of porous materials having a Drucker–Prager solid phase at microscale and two populations of saturated pores with different pressures at both micro and meso scales. To this end, and taking account of the available results by Maghous et al. (2009), we first derive a closed‐form expression of approximate criterion for a dry porous medium whose matrix obeys to a general elliptic criterion. The methodology to formulate this criterion is based on limit analysis of a hollow sphere subjected to a uniform strain rate boundary conditions. The obtained results are then implemented in a two‐step homogenization procedure, which interestingly delivers analytical expression of the macroscopic criterion for dry double porous media whose solid phase at microscale obeys to a Drucker–Prager criterion. After a brief discussion of the results, we propose an extension to double porous saturated media, allowing therefore to quantify the simultaneous effects of the different pore pressures applied on each voids population. The results are discussed in terms of the existence or not of effective stresses. Finally, they are assessed by comparing them to recently available results. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
49.
《水文科学杂志》2013,58(1):166-170
Abstract Freshwater and sediment are crucial to the development and health of aquatic and wetland ecosystems in deltaic coastal regions. This study examines the long-term freshwater inflow (1940–2002) and total suspended solid loading (1978–2001), and their relationships with climate variables in three major river watersheds to Lake Pontchartrain, the largest inland estuary in the USA. The results show an average total annual freshwater inflow of 5.04 km3 and an average total annual sediment loading of 210 360 t, with the highest contributions from the Amite River watershed. Over 69% of annual inflow occurred within the six months from December to May. About 66–71% of the annual total suspended solid loading occurred within the four months from January to April. An increasing trend of annual water inflow and sediment discharge was found in the Amite River watershed over the past 60 years, coinciding with the fastest population growth in this upper Lake Pontchartrain basin. 相似文献
50.