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121.
Maria Andréasson Göran Dave 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1995,4(4):221-230
Uptake and biliary excretion of metals were studied in rainbow trout, Oncorhynchus mykiss, exposed through spiked sediment to a mixture of seven heavy metals. Metal concentrations and toxicity of bile and blood plasma were used as indicators of exposure. Among the seven metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) only three (Cu, Hg, and Pb) were concentrated in the bile (bile-plasma ratio >1). Bile-plasma ratios in the rainbow trout were similar to those found in rats for Cu and Hg. Daphnia magna bioassays were used to determine toxicity of bile and blood plasma in the same trout. Toxicity of bile and blood plasma increased after treatment with acid. An analysis of variance (ANOVA) showed that toxicity of bile and blood plasma to D. magna in metal-exposed trout was significantly correlated with (1) bile and blood plasma test concentration, (2) acid treatment of bile and blood plasma (hydrolysis of metal-plasma and metal-bile complexes) and (3) sediment concentration of metals during exposure of trout. In order to significantly detect the magnitude of the exposure to a xenobiotic the biomarker must respond in a dose- or time-dependent manner. Therefore, the potential use of bile toxicity as a biomarker of heavy metal exposure in fish is probably limited by the low bioconcentration of many of these toxicants in bile. 相似文献
122.
In order to investigate the effect of large isoform of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activase (RuBPCO-A)
on photosynthesis, cDNA of the enzyme (rca) was transferred to rice cultivars (Oryza sativa f. japonica cv. Nipponbare) under the control of RuBPCO small subunit gene promoter (rbcS) via Agrobacterium tumefaciens-mediated transformation. Transgenic rice plants were identified by polymerase chain reaction (PCR) and Southern and Western
blot analyses. Net photosynthetic rate (P
N) values of the T1 transgenic lines 34 (T34) and 40 (T40) were 45.26 and 46.32 % higher than that of the control plants, respectively. At the
same time, their carboxylation efficiency and RuBPCO initial activity, quantum yield of electron transport in photosystem
2 (ΦPS2), and steady state photochemical fluorescence quenching (qP) increased. In addition, heading time of the transgenic rice was advanced. Thus increasing the amount of large isoform of
RuBPCO-A in the transgenic rice might have a stimulatory effect on both photosynthesis and plant growth. 相似文献
123.
A process-orientated design and performance assessment methodology for passive mine water treatment systems 总被引:1,自引:0,他引:1
The aim of this paper is the development of a methodology for assessing the iron removal efficiency of passive mine water treatment settling lagoons and reed beds. Previous work in the design and sizing of coal mine drainage lagoons and wetlands has focussed on the use of standard hydraulic residence times or using the 10 g m−2 d−1 metric, these criteria have been applied without regard to the fundamental physical and chemical processes controlling iron removal in the system, namely the pH dependent rates of Fe(II) oxidation and physical settling of the particulate Fe(III). In this study field water quality data have been collected from lagoons and reed beds. These data are examined alongside data from the UK Coal Authority database and combined with simple mathematical formulations to provide a framework through which to understand passive treatment schemes from a process-orientated perspective. It is demonstrated that for the sites studied reed beds are more efficient for iron removal. This paper recommends that judgements of iron removal performance should be based on a derived treatment efficiency index (?) and that the modelling approach espoused in this paper should be used when designing passive mine water treatment schemes. 相似文献
124.
Liming Yan Yiqi Luo Rebecca A. Sherry Jesse E. Bell Xuhui Zhou Jianyang Xia 《Global Change Biology Bioenergy》2014,6(5):556-565
The efficiency of a terrestrial ecosystem to use rainfall in production is critical in regulating the ecological functions of the earth system under global change. However, it remains unclear how rain use efficiency (RUE) will be altered by changes in climate and human activities such as biofuel harvest. In this study, we used RUE data from a long‐term experiment in a tallgrass prairie to analyze the effects of warming and biofuel harvest (clipping). From 2000 to 2011, experimental warming enhanced RUE in most years, with larger positive effects in normal and wet than dry hydrological years. Clipping decreased RUE in dry and normal hydrological years, but had no impact on RUE in wet years. The observed RUE responses resulted from treatment‐induced changes in both biologically ineffective (i.e., runoff and soil evaporation) and effective (i.e., transpiration) parts of precipitation. For example, litter cover was increased in warming plots, but reduced by clipping, leading to negative and positive effects on runoff and soil evaporation, respectively. The dominance of C4 species, which usually have higher water use efficiency than C3 species, was enhanced by warming, but reduced by clipping. Moreover, RUE was positively correlated with ratios of rainfall in the late growing season (June–August), when the growth of C4 plants was most active, relative to that in the other seasons. Our results indicate that RUE is positively influenced by climate warming, but negatively affected by biofuel harvest in tallgrass prairie of the Great Plains. These findings highlight the important roles of plant community structure and temporal distribution of precipitation in regulating ecosystem RUE. 相似文献
125.
Sediment pore water concentrations of Fe2+, Mn2+, NH
inf4
sup+
and CH4 were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station
with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4
mM m−2 day−1 (0.3 g m−2 day−1). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly
using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment
loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe2+ and CH4. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe2+ and Mn2+ to as high as 26% for NH
inf4
sup+
, and 30% for CH4. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this
station. 相似文献
126.
Estimation of Tissue Construction Cost from Heat of Combustion and Organic Nitrogen Content 总被引:13,自引:4,他引:13
Abstract. We present a method for estimating the construction costs of plant tissues from measurements of heat of combustion, ash content, and organic nitrogen content. The method predicts glucose equivalents, the amount of glucose required to provide carbon skeletons and reductant to synthesize a quantity of organic product. Glucose equivalents have previously been calculated from the elemental composition of tissue. We define construction cost as the amount of glucose required to provide carbon skeletons, reductant and ATP for synthesizing the organic compounds in a tissue via standard biochemical pathways. The fraction of the total construction cost of a compound or tissue (excluding costs of transporting compounds) that is reflected in its glucose equivalents is the biosynthetic efficiency ( E B ). This quantity varies between 0.84 and 0.95 for tissues with a wide range of compositions. Using the new method, total construction cost can be estimated to ± 6% of the value obtained from biochemical pathway analysis.
Construction costs of leaves of three chaparral species were estimated using the proposed method and compared to previously published values, derived using different methods. Agreement among methods was generally good. Differences were probably due to a combination of inaccuracy in the estimated biosynthetic efficiency and technical difficulties with biochemical analysis, one of the older methods of determining construction cost. 相似文献
Construction costs of leaves of three chaparral species were estimated using the proposed method and compared to previously published values, derived using different methods. Agreement among methods was generally good. Differences were probably due to a combination of inaccuracy in the estimated biosynthetic efficiency and technical difficulties with biochemical analysis, one of the older methods of determining construction cost. 相似文献
127.
Diurnal changes in needle gas exchange in alpine Pinus pumila during snow-melting and summer seasons
Atsushi Ishida Takashi Nakano Seikoh Sekikawa Emiko Maruta Takehiro Masuzawa 《Ecological Research》2001,16(1):107-116
Pinus pumila (Pallas) Regel. is a dominant dwarf tree in alpine regions of Japan. The possible factors limiting the net photosynthetic rate (Pn) of the needles of P. pumila were examined in the snow-melting (May) and the summer (August) seasons. In August, in situ maximum Pn was 20 mol kg–1 needle s–1 in the current-year needles and 25 mol kg–1 needle s–1 in the 1-year-old needles. Diurnal trends of Pn in August were positively related to fluctuations in photosynthetic photon flux density (PPFD) and no midday depression of Pn was found, indicating that a decrease in PPFD rather than an increase in needle-to-air vapor pressure deficit (W) might cause the reduction of Pn. Both stomatal conductance (gs) and Pn were lower in May than in August. In May, Pn and gs were almost zero in the morning, but gradually increased with decreasing W, reaching maximum Pn values (4 mol kg–1 needle s–1) and gs (60 mmol kg–1 needle s–1) at 16.00 hours. The daytime Pn in May was positively related to gs. Relative water content in the exposed needles above the snow in May was 83%, which was far above the lethal level. This indicates that the water flow from stems or soils to needles was enough to compensate for a small amount of water loss due to the low gs in May, although the water supplied to needles would be impeded by the low temperatures. Thus, the reduced gs in May would be important for avoiding needle desiccation, and would result in a reduced Pn. 相似文献
128.
129.
Jyotirmay Mathur Narendra Kumar Bansal 《The International Journal of Life Cycle Assessment》1999,4(2):113-116
This analysis can be called energy accounting of solar water heating systems. Five types of solar water heating systems have
been considered. With the help of material balance, energy content has been found in these systems. Yearly output of systems
has been found by conducting transient simulations using hourly data of radiation and ambient temperature. Such analysis has
been done separately for one representative city of each of six climatic zones of India. The energy payback for India ranges
from 0.73 to 4.16 years for the thirty cases considered here. 相似文献
130.
Thi Thuy Duong Michel Coste Agnès Feurtet-Mazel Dinh Kim Dang Caroline Gold Young Seuk Park Alain Boudou 《Hydrobiologia》2006,563(1):201-216
The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied
during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks.
To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used
on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were
applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers.
These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site
were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm2. Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices
gave similar results and indicate the Tolich River with the lowest values as a highly polluted site. 相似文献