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991.
Passy SI 《Environmental monitoring and assessment》2007,127(1-3):409-417
Diatom assemblages from 83 epilithic samples taken from the Mesta River, Bulgaria, were regressed against three sets of predictor
variables, i.e. environmental, spatial, and temporal. Redundancy analysis (RDA) of species and environmental data explained
36% of the diatom variance and extracted several important gradients of species distribution, associated with a downstream
increase in nutrient levels, pH, temperature, and organic pollution. The inclusion of spatial and temporal variables in the
RDA model captured additional 24% of the diatom variance and revealed three more gradients, a spatial gradient represented
by higher order polynomial terms of latitude and longitude, and two temporal gradients of annual and seasonal variation. Partial
RDAs demonstrated that the unique contribution of each predictor set to the explained diatom variance was the highest in the
spatial dataset (16%), followed by the environmental (9%), and the temporal (7%) datasets. The remaining 28% of the variance
was explained by the covariance of the predictor sets. This suggests that in biomonitoring of single stream basins, the cheap
and simple account of space and time would explain most of the variance in assemblage composition obviating the necessity
of expensive and time-consuming environmental assessments. The nature of the underlying environmental mechanisms can be easily
inferred from the diatom composition itself. 相似文献
992.
Previous work has shown that arsenic can accumulate in drinking water distribution system (DWDS) solids (Lytle et~al., 2004) when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or
chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary
objective of this work was to examine the impact of pH and orthophosphate on the chemical release (i.e. desorption) of arsenic
from nine DWDS solids collected from utilities located in the Midwest. Arsenic release comparisons were based on the examination
of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168~hours. Results
showed that arsenic was released from solids and suggested that arsenic release was a result of desorption rather than dissolution.
Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in
the test range of 7 to 9). Finally, orthophosphate (3 and 5 mg PO4/L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic
present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting
in elevated levels at the consumer's tap. 相似文献
993.
Budziak D Richard L Beltrame E Carasek E 《Environmental monitoring and assessment》2007,127(1-3):435-444
Formation of trihalomethanes (THM) was monitored at the Laboratório de Camarões Marinhos (LCM) from the Universidade Federal de Santa Catarina. THM could be present because chlorinated effluents from disinfection are discharged from the different hatchery rooms. THM quantification was done through an analytical methodology using Purge&;Trap coupled with a gas chromatograph equipped with an electron capture detector. Relative standard deviation (RSD), limit of detection (LOD) and limit of quantification (LOQ) for the methodology corresponded to the ranges of 8–17%; 0.01–0.03 μg L?1 and 0.03–0.08 μg L?1, respectively. Linear working range was of 0.1–8.0 μg L?1 for all compounds. Enrichment and recovery method was applied to evaluate possible matrix effects and the results varied from 71.2% to 107.9%. LCM was monitored between August and December, 2004. This study showed that THM did not increase with the increase in postlarvae production and also that the aquatic life and the surrounding environment were not affected. 相似文献
994.
Almeida CA Quintar S González P Mallea MA 《Environmental monitoring and assessment》2007,133(1-3):459-465
A study of the water quality of the Potrero de los Funes River (San Luis – Argentina) was carried out in order to evaluate
the possible effect of the anthropogenic activities on the river developed in the homonymous town. Samples were collected
during the period March 2000–November 2005 at three selected sampling sites (RP1, RP2 and RP3). Different physicochemical and bacteriological parameters (turbidity, pH, conductivity, suspended solids, alkalinity, potassium,
sodium, calcium, magnesium, chlorides, nitrates, phosphates, sulphates, chemical oxygen demand (COD), 5-day biological oxygen
demand (BOD5), dissolved oxygen, total coliforms, Escherichia coli and total heterotrophic bacteria) were analysed according to the Standard Method for the Examination of Water and Wastewater.
When comparing the values of total coliforms, E. coli, total heterotrophic bacteria, COD, BOD5 and phosphates from the zone without anthropogenic influence (RP1) and the urban zones (RP2 and RP3) an important variation in the parameters was observed. These results indicate that the urban activity produces a serious
and negative effect on the water quality, thus constituting a sanitary risk and may have a major impact on the trophic status
of the Potrero de los Funes dam. As case study, we report on the use of General Quality Index (GQI) to evaluate spatial and
seasonal changes in the water quality of Potrero de los Funes River. Results revealed a significant degradation of the water
quality at RP2 and RP3. 相似文献
995.
This paper examines the importance of the correlation between hydraulic conductivity (K) and degradation rate constant (k) during the transport of reactive contaminants in heterogeneous aquifers. We simulated reactive transport in an ensemble of two-dimensional heterogeneous aquifers. Two sets of transport simulations were conducted: one in which a perfect positive correlation was assumed between ln(K) and ln(k), and one in which a perfect negative correlation was assumed. We found that the sign of the correlation has important consequences for the contaminant transport. Qualitatively, a negative correlation leads to significantly more pronounced "fingering" of the contaminant plume than does a positive correlation, with potentially important consequences for downgradient receptors. Quantitatively, the expected behavior (as quantified by the contaminant mass remaining in the aquifer) is statistically different between the positive and negative cases: on average, more contaminant mass persists when K and k are negatively correlated. Also, the negative correlation leads to more variability between realizations of the ensemble, whereas a positive correlation induces relatively little variability between realizations. We discuss the implications of these findings for the management of contaminated aquifers. 相似文献
996.
This investigation conducted a full-scale survey the drinking water distribution system in Kaohsiung city, Taiwan. The aim
was to investigate whether the distribution system was capable of maintaining high water quality from the water treatment
facilities through to the end user. The results showed that the distribution system can maintain high water quality, except
for suitable chlorine residuals. The authors plotted chlorine residual contour maps to identify areas with low chlorine residuals,
helping them prioritize sections that must be flushed or renewal. The contour maps also provide sufficient and clear information
for locating booster chlorination stations. Contour maps enable water facilities to identify how water quality decays in the
distribution systems and the locations of such decay. Water quality decay can be caused by properties of pipeline materials,
hydraulic conditions, and/or biofilm thickness. However, understanding the exact reasons is unnecessary because the contour
maps provide sufficient information for trouble-shooting the distribution systems. 相似文献
997.
Sustainable development planning must be based on environmental and biophysical baseline indices that effectively define comparative development potential and environmental constraints. As such, indices must define the comparative advantage of the natural resource base and measure the fundamental capacity to sustain production rates of natural resource goods and services used to create societal well being. Complex biophysical and socioeconomic characteristics affect the identification and selection of sustainable development strategies. When derived from effective baseline indicators, indices may be used to define the spatial and temporal distribution of economically viable production opportunities and may be expressed in derived indices that realistically describe basic production opportunities and guide the selection of feasible, long-term development strategies. Specifically, representative indices are critical in the identification of development goals and realistic objectives and can be used to evaluate, select and implement sustainable development strategies and plans. It is stressed that the relevancy and effectiveness of public policies depend on the identification of representative evaluation models and baseline indices to define development strategies that are both environmentally sustainable and economically viable. In this context, the role of baseline indicators that define natural resource production capacities is discussed. This includes potential resource uses, derived benefits and their economic and environmental impacts. Key thematic indicators are suggested that may be especially useful in identifying development alternatives and impacts. This suggested that clearly defined environmental pollution limits or impact standards be used to define public risk tolerance limits and carrying capacity constraints. It is argued that these measures may be more effective in directing policy choices than economic valuation of non market goods and services that represent environmental externalities associated with resource exploitation options and economic development strategies. To this end, examples of thematic indicators and derived indices are introduced that may prove effective in resource assessment, economic evaluation and strategic development planning. 相似文献
998.
Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive
rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental
study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or
female was offered a choice between two mates with either a small or a large difference in body length representing a small
or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or
not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred
large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR.
Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with
their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative
PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one
important factor explaining the observed sex difference in choosiness.
Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000 相似文献
999.
Most studies of social polygyny in birds have examined male provisioning on the basis of the number of feeding visits. This
may be misleading if males compensate for infrequent visits by bringing larger prey at each visit. We investigated nestling
provisioning in the socially polygynous great reed warbler, Acrocephalus arundinaceus, in south Central Sweden in 1996–1997. We collected data on rate of feeding visits, prey size and the amount of biomass delivered
by males and females. Males had lower rates of feeding visits and provided smaller prey to nestlings in secondary than in
monogamous and primary nests. Secondary females had higher rates of feeding visits and brought larger prey than monogamous
and primary females. These results confirm that secondary females face a potential cost of polygyny through a lower rate of
male feeding, and that this cost was reinforced by the significantly lower male provisioning rate (biomass h–1) at secondary nests. Secondary females compensated for the lack of male assistance by increasing their rate of feeding and
bringing larger prey. As a result, offspring in nests of secondary females received as much food as did those in nests of
primary females. Prey load size increased with the parent’s proportion of feeding visits, suggesting that parents use different
feeding strategies depending on their amount of responsibility for nestling provisioning. We suggest that parents which take
the main responsibility for nestling feeding have to forage further away from the nest, and based on optimal-foraging theory,
they should then on average bring larger prey to their nest.
Received: 4 April 1999 / Received in revised form: 12 October 1999 / Accepted: 23 October 1999 相似文献
1000.
文章论述了家庭生活水的氡浓度水平、生活用水对室内氡的贡献、水的使用过程中室内氡行为以及含氡水的使用与辐射照射剂量的关系等问题。指出家庭生活水的氡浓度高时,是室内氡的一个不可忽视的来源。对氡浓度特别高的家庭用水,建议先用活性炭等进行吸附后再使用。 相似文献