排序方式: 共有67条查询结果,搜索用时 354 毫秒
21.
Ana María Murgida Marcela Hebe González Holm Tiessen 《Regional Environmental Change》2014,14(4):1387-1394
Regional change under agricultural expansion in the Chaco of Argentina is determined by interactions of rainfall change, infrastructure development, socio-economic actions and values, and the social perceptions of change. Our study focused on adaptation in the socio-environmental system which is the key to understanding opportunities, uncertainties and risk in the context of historical change. Change in land use from extensive grazing through mixed farming and on to industrial-scale soybean production was made possible by a trend of increasing rainfall that reduced the risk of crop failure from drought since the 1970s. Rainfall change coincided with a period in which the Chaco forest was suffering extensive degradation from long-term extractive use. The degradation aided agricultural expansion since the degraded state of the ecosystem justified public policies of deforestation. In parallel to these resource-based processes, public policy changed in the late 70s and 80s toward favoring privatization of state land and exclusion of small producers. This permitted the land concentration needed for industrial-scale production. Technological innovation in both water and land resource management reinforced the process of concentration because small producers rarely have the financial or educational capital to develop or implement emerging technologies. One of the results of the intensification and expansion of agriculture is that soil surface sealing, waterlogging and flood risk are now effective at a landscape scale. To address these risks, private enterprise and government efforts must now come together toward innovative policies in integrated landscape management. 相似文献
22.
23.
Marcela Rojas Felipe Quintero Witold F. Krajewski 《Journal of the American Water Resources Association》2020,56(4):568-585
This paper explores the performance of the analysis‐and‐assimilation configuration of the National Water Model (NWM) v1.0 in Iowa. The NWM assimilates streamflow observations from the United States Geological Survey (USGS), which increases the performance but also limits the available data for model evaluation. In this study, Iowa Flood Center Bridge Sensors (IFCBS) data provided an independent nonassimilated dataset for evaluation analyses. The authors compared NWM outputs for the period between May 2016 and April 2017, with two datasets: USGS streamflow and velocity observations; Stage and streamflow data from IFCBS. The distribution of Spearman rank correlation (rs), Nash–Sutcliffe efficiency (E), and Kling–Gupta efficiency (KGE) provided quantification of model performance. We found the performance was linked with the spatial scale of the basins. Analysis at USGS gauges showed the strongest performance in large (>10,000 km2) basins (rs = 0.9, E = 0.9, KGE = 0.8), with some decrease at small (<1,000 km2) basins (rs = 0.6, E = ?0.25, KGE = ?0.2). Analysis with independent IFCBS observations was used to report performance at large basins (rs = 0.6, KGE = 0.1) and small basins (rs = 0.2, KGE = ?0.4). Data assimilation improves simulations at downstream basins. We found differences in the characterization of the model and observed data flow velocity distributions. The authors recommend checking the connection of USGS gauges and NHDPlus reaches for selected locations where performance is weak. 相似文献
24.
Application of water quality indices and analysis of the surface water quality monitoring network in semiarid North-Central Chile 总被引:4,自引:0,他引:4
Espejo L Kretschmer N Oyarzún J Meza F Núñez J Maturana H Soto G Oyarzo P Garrido M Suckel F Amezaga J Oyarzún R 《Environmental monitoring and assessment》2012,184(9):5571-5588
Surface water quality has increasing importance worldwide and is particularly relevant in the semiarid North-Central Chile, where agriculture and mining activities are imposing heavy pressure on limited water resources. The current study presents the application of a water quality index in four watersheds of the 29°-33°S realm for the period 1999-2008, based on the Canadian Council of Ministers for the Environment approach and the Chilean regulation for irrigation water quality. In addition, two modifications to the index are tested and a comprehensive characterization of the existing monitoring network is performed through cluster analysis. The basins studied show fairly good water quality in the overall, specially the Limarí basin. On the other hand, the lower index values were obtained for the headwaters of Elqui, associated with the El Indio mining district. The first modification of the indicator (i.e., to consider parameters differentially according to their effect on human health or the environment) did not produce major differences with respect to the original index, given the generally good water quality. The second modification (i.e., to consider as threshold values the more restrictive figures derived from a set of regulations) yielded important differences in the indicator values. Finally, an adequate characterization of the monitoring network was obtained. The results presented spatial coherence and the information can be used as a basis for the optimization of the monitoring network if required. 相似文献
25.
Dias Marcela França Leroy-Freitas Deborah Machado Elayne Cristina da Silva Santos Leticia Leal Cintia Dutra da Rocha Fernandes Gabriel de Araújo Juliana Calábria 《Environmental science and pollution research international》2022,29(24):36088-36099
Environmental Science and Pollution Research - Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and... 相似文献
26.
The efficacy of ozonation and of photocatalysis processing in the treatment of pulp mill ECF (elementary chlorine free) bleaching and textile effluents was evaluated by determining total organic carbon reduction (TOC) and the toxicity. The chronic toxicity of the effluents was evaluated by the ability to inhibit the growth of algae Selenastrum capricornutum. Cultured hamster V79 fibroblasts were used to assess the cytotoxicity of effluents submitted to different detoxification processes. Two endpoints were measured in V79 cells: 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) reduction and neutral red uptake (NRU). Both treatment processes were able to reduce the TOC, although ozonization was less effective for pulp mill ECF bleaching. The pulp mill ECF bleaching and textile effluents reduced the growth of S. capricornutum by 39% and 27%, respectively. However, at the highest concentration tested, the textile effluents treated by photochemical process for 60 min showed increased cytotoxicity in V79 cells compared to the untreated effluent when assessed by the NRU and MTT reduction assays (increases of 30% and 40%, respectively). Pulp mill ECF bleaching effluent treated by ozonization had a similar cytotoxicity to that of untreated effluent in the NRU assay. In contrast, the MTT reduction assay indicated that effluents treated with ozone were around 20% more cytotoxic than untreated effluents. These results show that cultured fibroblasts may be useful for studying cellular responses to pollutants and may be included in tests to monitor the efficiency of effluent detoxification processes. 相似文献
27.
Mariano B Cristian O Marcela P Porta A 《Environmental pollution (Barking, Essex : 1987)》2006,144(1):280-288
The use of organisms to monitor contamination allows the access to information that cannot be acquired by chemical methods. Limnoperna fortunei, mussel frequently found in Río de la Plata estuary, fulfils the requirements to be used as a biomonitoring organism. In this work we report that a polypeptide of 22 kDa of molecular weight (LF22) is induced when L. fortunei is exposed to Cd (II), Cu(II) and Hg(II) sublethal levels. To characterize LF22, mussels were sampled from a non-polluted region and whole soft tissue was homogenized, with and without previous exposure to 100 microg/L of Cd(II). The cytosolic proteins were evaluated by mono and bidimensional SDS-PAGE, and size exclusion chromatography. All the methods showed that LF22 triples its concentration in presence of Cd(II). Purification of LF22 was achieved by fractioned precipitation, salting-out, ionic exchange and size exclusion chromatography. We conclude that LF22 is a useful biomarker of heavy metal exposure. 相似文献
28.
Non-aggressive mate guarding by the blue-footed booby: a balance of female and male control 总被引:3,自引:1,他引:2
Thirteen pairs of blue-footed boobies (Sula nebouxii) were observed on their colony. Pairs courted frequently and, on average, copulated 24 times during the 30 days before laying,
with 38% of those copulations occurring in the last 5 days (presumed fertile period). Males and females increased attendance
at the nest site as laying approached. Seven females performed an average seven extra-pair copulations, with 1–2 paired male
neighbors, but these were less concentrated in the presumed fertile period than within-pair copulations, and the last two
copulations of all 7 females were with their social mates. Rates of female extra-pair copulations were six times lower when
their social mate was present, and during the presumed fertile period, no female performed an extra-pair copulation in the
presence of her mate. Males did not respond to infidelity of social mates with aggression, prompt copulation, retaliatory
copulation, or increase in copulation. Seven of 13 males performed an average of five extra-pair copulations, with 1–3 paired
female neighbors, before their own mates began egg-laying. The males' extra-pair copulations represented only 4% of their
total copulations during their own mates' presumed fertile periods. Females, the larger sex, apparently control sexual access
and copulate with extra males to achieve extra-pair fertilization. Males pursue a mixed strategy: they copulate with extra
females, mostly outside their own mate's presumed fertile period, and they copulate increasingly with their social mate as
laying approaches, probably assuring some paternity by mate guarding, involving attendance and courtship. Behavior of males
and females is also consistent with other hypotheses for extensive joint nest site attendance: pairbonding, copulation access,
and territory acquisition.
Received: 14 November 1997 / Accepted after revision: 16 May 1998 相似文献
29.
A System Dynamics Model for the Environmental Management of the Sepetiba Bay Watershed, Brazil 总被引:2,自引:0,他引:2
In the recent past, the Sepetiba Bay watershed, located in the Rio de Janeiro State, Brazil has experienced rapid industrial
development and population growth, as well as an increase in water pollution and environmental degradation. To analyze the
complex interrelationships among the agents affecting the Sepetibza Bay environment, a system dynamics model was developed.
The model builds on extensive studies conducted for the watershed, and simulates different hypotheses of economic growth and
of demographic expansion. Thus, it can be used as a decision support tool for the identification of investment priorities
and policy analyses under various scenarios. In order to provide a comprehensive approach to the environmental management
of the Sepetiba Bay watershed, the model had to consider only the most relevant aspects of the behavior and the key interactions
among agents operating in the watershed. In this article, the model’s structure is presented together with some of its main
results. 相似文献
30.
Marcela Soto-Beltran Luisa A. Ikner Kelly R. Bright 《Food and environmental virology》2013,5(2):91-96
Enteric viruses are often present in low numbers in various water matrices. Virus sampling therefore involves multiple concentration steps to condense large samples down to small volumes for detection by cell culture or molecular assays. The NanoCeram® Virus Sampler has been demonstrated to be effective for the recovery of viruses from tap water, surface waters, and seawater. The goal of this study was to evaluate a new method using NanoCeram® filters for the recovery of poliovirus 1 (PV-1) from treated wastewater. Activated sludge effluent samples were spiked with PV-1 and concentrated in side-by-side tests by two methods: (1) NanoCeram® filtration, elution with sodium polyphosphate buffer, secondary concentration via centrifugal ultrafiltration; and (2) 1MDS filtration, elution with beef extract, secondary concentration via organic flocculation. The virus retention and elution efficiencies did not differ significantly between the two methods. In contrast, the secondary concentrate volume was smaller for the NanoCeram® method (8.4 vs. 30 mL) and the secondary concentration efficiencies were different between the two methods with 98 % for centrifugal ultrafiltration (NanoCeram®) and 45 % for organic flocculation (1MDS). The overall method efficiencies were significantly different (P ≤ 0.05) with the NanoCeram® method yielding a 57 % and the 1MDS a 23 % virus recovery. In addition, there appeared to be less interference with viral detection via polymerase chain reaction with the NanoCeram® concentrates. This NanoCeram® method therefore is able to efficiently recover PV-1 from large volumes of wastewater and may serve as an inexpensive alternative to the standard 1MDS filter method for such applications. 相似文献