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41.
Ika Paul-Pont Xavier de Montaudouin Patrice Gonzalez Philippe Soudant Magalie Baudrimont 《Environmental science and pollution research international》2010,17(4):987-998
Introduction
Within the last decade, numerous studies have investigated the role of environmental history on tolerance to stress of many organisms. This study aims to assess if Manila clams Ruditapes philippinarum may react differently to cadmium exposure and trematode parasite infection (Himasthla elongata) depending on their origin and environmental history in Arcachon Bay (France). 相似文献42.
Monica Lipscomb Smith Weiqi Zhou Mary Cadenasso Morgan Grove Lawrence E. Band 《Journal of the American Water Resources Association》2010,46(2):429-442
Smith, Monica Lipscomb, Weiqi Zhou, Mary Cadenasso, Morgan Grove, and Lawrence E. Band, 2010. Evaluation of the National Land Cover Database for Hydrologic Applications in Urban and Suburban Baltimore, Maryland. Journal of the American Water Resources Association (JAWRA) 46(2):429-442. DOI: 10.1111/j.1752-1688.2009.00412.x Abstract: We compared the National Land Cover Database (NLCD) 2001 land cover, impervious, and canopy data products to land cover data derived from 0.6-m resolution three-band digital imagery and ancillary data. We conducted this comparison at the 1 km2, 9 km2, and gauged watershed scales within the Baltimore Ecosystem Study to determine the usefulness and limitations of the NLCD in heterogeneous urban to exurban environments for the determination of land-cover information for hydrological applications. Although the NLCD canopy and impervious data are significantly correlated with the high-resolution land-cover dataset, both layers exhibit bias at <10 and >70% cover. The ratio of total impervious area and connected impervious area differs along the range of percent imperviousness – at low percent imperviousness, the NLCD is a better predictor of pavement alone, whereas at higher percent imperviousness, buildings and pavement together more resemble NLCD impervious estimates. The land-cover composition and range for each NLCD urban land category (developed open space, low-intensity, medium-intensity, and high-intensity developed) is more variable in areas of low-intensity development. Fine-vegetation land-cover/lawn area is incorporated in a large number of land use categories with no ability to extract this land cover from the NLCD. These findings reveal that the NLCD may yield important biases in urban, suburban, and exurban hydrologic analyses where land cover is characterized by fine-scale spatial heterogeneity. 相似文献
43.
Flavio S. Silva Joyce Cristale Paulo A. André Paulo H.N. Saldiva Mary R.R. Marchi 《Atmospheric environment (Oxford, England : 1994)》2010,44(39):5133-5138
In Brazil, sugarcane fields are often burned to facilitate manual harvesting, and this burning causes environmental pollution from the large amounts of soot released into the atmosphere. This material contains numerous organic compounds such as PAHs. In this study, the concentrations of PAHs in two particulate-matter fractions (PM2.5 and PM10) in the city of Araraquara (SE Brazil, with around 200,000 inhabitants and surrounded by sugarcane plantations) were determined during the sugarcane harvest (HV) and non-harvest (NHV) seasons in 2008 and 2009. The sampling strategy included four campaigns, with 60 samples in the NHV season and 220 samples in the HV season. The PM2.5 and PM10 fractions were collected using a dichotomous sampler (10 L min?1, 24 h) with Teflon? filters. The filter sets were extracted (ultrasonic bath with hexane/acetone (1:1 v/v)) and analyzed by HPLC/Fluorescence. The median concentration for total PAHs (PM2.5 in 2009) was 0.99 ng m?3 (NHV) and 3.3 ng m?3 (HV). In the HV season, the total concentration of carcinogenic PAHs (benz(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene) was 5 times higher than in the NHV season. B(a)P median concentrations were 0.017 ng m?3 and 0.12 ng m?3 for the NHV and HV seasons, respectively. The potential cancer risk associated with exposure through inhalation of these compounds was estimated based on the benzo[a]pyrene toxic equivalence (BaPeq), where the overall toxicity of a PAH mixture is defined by the concentration of each compound multiplied by its relative toxic equivalence factor (TEF). BaPeq median (2008 and 2009 years) ranged between 0.65 and 1.0 ng m?3 and 1.2–1.4 ng m?3 for the NHV and HV seasons, respectively. Considering that the maximum permissible BaPeq in ambient air is 1 ng m?3, related to the increased carcinogenic risk, our data suggest that the level of human exposure to PAHs in cities surrounded by sugarcane crops where the burning process is used is cause for concern. 相似文献
44.
Maurice Juma Ogada Dianah Muchai Germano Mwabu Mary Mathenge 《Environment, Development and Sustainability》2014,16(5):1065-1076
Smallholder agriculture dominates Kenya’s agricultural landscape, accounting for 75 % of total agricultural output and 70 % of the marketed agricultural produce. As a result, the Government of Kenya, with the support of development partners, has invested in production and dissemination of productivity-enhancing technologies such as high-yielding varieties and inorganic fertilizers targeting the smallholders. Adoption of these technologies has remarkably improved, especially in the maize sub-sector. However, productivity has been declining or, at best, stagnating. Productivity is attributable to not only technological improvements but also technical efficiency. Consequently, this study sought to determine the technical efficiency of the country’s smallholder food crop farmers and establish how it correlates with environmental factors. The study used a two-stage nonparametric approach on household panel data to estimate the efficiency levels of the smallholders and establish the sources of its variation across households. Controlling for endogeneity and incorporating geographic information system-derived measures of environmental factors in the analysis, the study finds that technical efficiency differentials are influenced by environmental factors, production risks and farmer characteristics. The policy implication is that the country has room to improve agricultural productivity by addressing environmental and farm-level constraints. Viable options include switching from rain-fed to irrigated agriculture, entrenching land tenure security, improving transport network among farm communities and setting up smallholder credit schemes. 相似文献
45.
Ariamalar Selvakumar Mary Ellen Tuccillo Swarna Muthukrishnan Asim B. Ray 《补救:环境净化治理成本、技术与工艺杂志》2009,19(2):135-142
Several compositions of Fenton's Reagent and hydrogen peroxide alone were used to disinfect combined sewage samples from a wastewater treatment facility. The presettled samples contained suspended solids (SS) and dissolved organic carbon (DOC) at concentrations of 28 and 290 mg/L, respectively. Disinfection with Fenton's Reagent was carried out at a pH between 5.90 and 6.0 and at a temperature of 25°C. All disinfected samples contained residual oxidants. Under all reaction conditions studied, complete inactivation of E. coli was achieved within one minute of the addition of Fenton's Reagent. Disinfection with hydrogen peroxide alone under similar conditions is incomplete even under much longer contact times. © 2009 Wiley Periodicals, Inc. 相似文献
46.
Michael A. Mallin Mary I. Haltom Bongkeun Song Mary E. Tavares Stephen P. Dellies 《Journal of environmental management》2010,91(12):2748-2753
Fecal contamination of water bodies causes a public health problem and economic loss. To control such contamination management actions need to be guided by sound science. From 2007–2009 a study was undertaken to determine the sources of fecal bacteria contamination to the marine waters adjoining the Town of Wrightsville Beach, North Carolina, USA. The research effort included sampling for fecal coliform and Enterococcus bacteria, sampling for optical brighteners, dye studies, and use of molecular bacterial source tracking techniques including polymerase chain reaction (PCR) and terminal restriction fragment polymorphism (T-RFLP) fingerprinting of the Bacteroides–Prevotella group. Of the 96 samples collected from nine locations during the study, the water contact standard for Enterococcus was exceeded on 13 occasions. The T-RFLP fingerprint analyses demonstrated that the most widespread source of fecal contamination was human, occurring in 38% of the samples, with secondary ruminant and avian sources also detected. Optical brightener concentrations were low, reflecting a lack of sewage line leakage or spills. A lack of sewer leaks and lack of septic systems in the town pointed toward discharge from boat heads into the marine waters as the major cause of fecal contamination; this was supported by dye studies. Based on these data, the Town initiated action to have the U.S. Environmental Protection Agency declare the coastal waters (out to 3 nautical miles), the nearby Atlantic Intracoastal Waterway and its tributaries a no-discharge zone (NDZ) to alleviate the human fecal pollution. The Town garnered supporting resolutions from other local communities who jointly petitioned the North Carolina Department of Environmental and Natural Resources. This State regulatory agency supported the local government resolutions and sent an application for an NDZ to the EPA in April 2009. The EPA concurred, and in February 2010 the coastal waters of New Hanover County, NC, became the first marine area on the U.S. eastern seaboard between Delaware and the Florida Keys to be declared a no-discharge zone. 相似文献
47.
48.
Chemical defenses are thought to contribute to the invasion success and impacts of many introduced plants; however, for most
of these species, little is known about these compounds and how they vary in natural environments. Plant allelochemical concentrations
may be affected by a variety of abiotic and biotic factors, including soil nutrients and herbivores. Moreover, such quantitative
variation is likely to play an important role in species interactions involving these invasive plants. The purpose of this
study was to examine patterns of variation in iridoid glycoside concentrations of the invasive plant Linaria dalmatica (Plantaginaceae). We conducted a greenhouse experiment to investigate the effect of soil nitrogen availability on iridoid
glycoside concentrations. Results from this experiment showed that plant iridoid glycoside concentrations decreased with increased
nitrogen availability. Additionally, plants were collected from multiple field sites in order to characterize the influence
of population, soil nitrogen availability, and herbivore attack on iridoid glycoside variation. Results from field studies
indicated that plants demonstrated considerable seasonal variation, as well as variation within and among populations, with
iridoid glycoside concentrations ranging from approximately 1 to 15% dry weight. The relationship between soil nitrogen and
plant iridoid glycosides varied among populations, with a strong negative correlation in one population, a marginally significant
negative relationship in a second population, and no relationship in the remaining two populations. Additionally, we found
a negative relationship between iridoid glycoside concentrations and plant injury by an introduced biocontrol agent, the stem-mining
weevil Mecinus janthinus (Cucurlionidae). These results show that plant allelochemical concentrations can vary widely in natural environments and
suggest that levels of plant defense may be reduced by increased soil nitrogen availability and herbivore attack in this invasive
plant species. 相似文献
49.
Analysis of bank erosion on the Merced River,Yosemite Valley,Yosemite National Park,California, USA 总被引:1,自引:0,他引:1
Channel changes from 1919 to 1989 were documented in two study reaches of the Merced River in Yosemite National Park through
a review of historical photographs and documents and a comparison of survey data. Bank erosion was prevalent and channel width
increased an average of 27% in the upstream reach, where human use was concentrated. Here, trampling of the banks and riparian
vegetation was common, and banks eroded on straight stretches as frequently as on meander bends. Six bridges in the upper
reach constrict the channel by an average of 38% of the original width, causing severe erosion. In the downstream control
reach, where human use was minimal, channel widths both decreased and increased, with a mean increase of only 4% since 1919.
Bank erosion in the control reach occurred primarily on meander bends. The control reach also had denser stands of riparian
vegetation and a higher frequency of large woody debris in channels. There is only one bridge in the lower reach, located
at the downstream end. Since 1919, bank erosion in the impacted upstream reach contributed a significant amount of sediment
(74,800 tonnes, equivalent to 2.0 t/km2/yr) to the river. An analysis of 75 years of precipitation and hydrologic records showed no trends responsible for bank erosion
in the upper reach. Sediment input to the upper reach has not changed significantly during the study period. Floodplain soils
are sandy, with low cohesion and are easily detached by lateral erosion. The degree of channel widening was positively correlated
with the percentage of bare ground on the streambanks and low bank stability ratings. Low bank stability ratings were, in
turn, strongly associated with high human use areas. Channel widening and bank erosion in the upper reach were due primarily
to destruction of riparian vegetation by human trampling and the effect of bridge constrictions on high flow, and secondarily
to poorly installed channel revetments. Several specific recommendations for river restoration were provided to park management. 相似文献
50.
This paper describes new environmental policies and expanded administrative agencies which in recent years have been adopted by many governments faced with a continuing decline in the quality of their environments. In a number of developed and developing countries, devising a far reaching environmental policy for sustainable development of the natural resources sector is a national priority. Specific environmental policies may be classified according to objectives, timeframe, mechanisms for implementation, whether or not they are binding, and the nature of sanction. This paper provides some generalizations about certain features common to most environmental policies. In the first section an examination is made of some of the most pressing problems which environmental policies relating to natural resources seek to address. The second section discusses environmental policies themselves. The third section, which makes up the main body of the paper, assesses the strengths and weaknesses of a variety of mechanisms available for implementing environmental policies to promote sustainable development in the natural resources sector. 相似文献