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301.
Pablo Andrés Domenech Patrick Saint-Pierre Georges Zaccour 《Environmental Modeling and Assessment》2011,16(6):519-539
We adopt viability theory to assess the sustainability of the world’s forests while taking into account some of the competing
economic, social, and environmental uses of these forests, namely, timber production, poverty alleviation through agriculture,
and air quality as well as the negative externalities that these uses create. We provide insights on the different trade-offs
faced to achieve sustainability and draw some policy implications as to what is the path leading to sustainability in the
long run. 相似文献
302.
Kim K Steuerwald AJ Parsons PJ Fujimoto VY Browne RW Bloom MS 《Journal of environmental monitoring : JEM》2011,13(9):2413-2419
Humans are exposed to concentrations of multiple trace elements through a variety of background sources; many are suspected reproductive toxicants. Prior to investigating associations between trace elements and human reproductive health, potential biomarkers of exposure should be characterized by sources of variability in the population at risk. Factors influencing elemental exposure should also be identified to ensure their consideration as potential confounding variables. The principal aim of this study is to characterize sources of variability for 19 trace elements measured in urine specimens collected from 55 women and 36 male partners completing a 1st cycle of in vitro fertilization (IVF). Urine specimens were analyzed using a biomonitoring method based on inductively coupled plasma-mass spectrometry (ICP-MS). Randomly selected urine specimens (~6%) were analyzed in duplicate, and these data were used to characterize sources of variability. Nine trace elements including As, Ba, Cd, Cs, Co, Cu, Mn, Mo, and Zn, were quantified in most specimens, indicating their utility in future epidemiologic studies of trace elements exposure and IVF outcomes. With few exceptions, normalizing urine using the traditional creatinine-correction procedure, or an alternative approach based on a linear regression model, increased residual variability only slightly. Sex and race appear to be important factors to consider in epidemiologic studies conducted in this population. Urine concentrations for most elements are similar to those reported in the 2005-2006 National Health and Nutrition Examination Survey (NHANES); however, differences in others may indicate regional trends or a unique exposure history for this infertile study population. 相似文献
303.
In mark-recapture studies, various techniques can be used to uniquely identify individual animals, such as ringing, tagging
or photo-identification using natural markings. In some long-term studies more than one type of marking procedure may be implemented
during the study period. In these circumstances, ignoring the different mark types can produce biased survival estimates since
the assumption that the different mark types are equally catchable (homogeneous capture probability across mark types) may
be incorrect. We implement an integrated approach where we simultaneously analyse data obtained using three different marking
techniques, assuming that animals can be cross-classified across the different mark types. We discriminate between competing
models using the AIC statistic. This technique also allows us to estimate both relative mark-loss probabilities and relative
recapture efficiency rates for the different marking methods. We initially perform a simulation study to explore the different
biases that can be introduced if we assume a homogeneous recapture probability over mark type, before applying the method
to a real dataset. We make use of data obtained from an intensive long-term observational study of UK female grey seals (Halichoerus grypus) at a single breeding colony, where three different methods are used to identify individuals within a single study: branding,
tagging and photo-identification based on seal coat pattern or pelage. 相似文献
304.
Rapid incorporation and short-term distribution of a nonylphenol isomer and the herbicide MCPA in soil-derived organo-clay complexes 总被引:1,自引:0,他引:1
Patrick Riefer Timm Klausmeyer Jan Schwarzbauer Andreas Sch?ffer Burkhard Schmidt Phillipe F. X. Corvini 《Environmental Chemistry Letters》2011,9(3):411-415
Organo-clay complexes in soil are a major sink for xenobiotics and, thus, often enhance their persistence dramatically. However,
the knowledge on environmental processes of non-extractable residue formation on a short time scale is very restricted. Therefore,
this study examined the distribution of 4-(3,5-dimethylhept-3-yl)phenol (NP) and 4-chloro-2-methylphenoxyacetic acid (MCPA)
in soil over a short time period of 48 h and in different soil sub-fractions. The overall proportion of organo-clay-associated
bound residues was not only abundant but also in the same range for both substances (MCPA: 8%; NP: 11% of applied 14C-radioactivity). However, a more detailed view revealed two different distribution patterns: a higher proportion of clay-associated
NP was accompanied by a lower content of bound residues, whereas a smaller fraction of clay-associated MCPA was characterized
by a higher proportion of non-extractable residues. Further on, a selective accumulation of bound residues among clay-associated
humic fractions was observed. NP residues were linked predominantly to humic acids, whereas MCPA residues tended to be incorporated
more into fulvic acids. It was evident that the overall distribution was influenced primarily by the physico-chemical properties
of the contaminants. This study demonstrates in detail a rapid initial incorporation accompanied by a specific distribution
into soil sub-fractions for selected xenobiotics in soil and points to a complex interaction of clay-associated organic matter
with low molecular weight compounds. 相似文献
305.
Response of algal metrics to nutrients and physical factors and identification of nutrient thresholds in agricultural streams 总被引:1,自引:0,他引:1
Robert W. Black Patrick W. Moran Jill D. Frankforter 《Environmental monitoring and assessment》2011,175(1-4):397-417
Many streams within the United States are impaired due to nutrient enrichment, particularly in agricultural settings. The present study examines the response of benthic algal communities in agricultural and minimally disturbed sites from across the western United States to a suite of environmental factors, including nutrients, collected at multiple scales. The first objective was to identify the relative importance of nutrients, habitat and watershed features, and macroinvertebrate trophic structure to explain algal metrics derived from deposition and erosion habitats. The second objective was to determine if thresholds in total nitrogen (TN) and total phosphorus (TP) related to algal metrics could be identified and how these thresholds varied across metrics and habitats. Nutrient concentrations within the agricultural areas were elevated and greater than published threshold values. All algal metrics examined responded to nutrients as hypothesized. Although nutrients typically were the most important variables in explaining the variation in each of the algal metrics, environmental factors operating at multiple scales also were important. Calculated thresholds for TN or TP based on the algal metrics generated from samples collected from erosion and deposition habitats were not significantly different. Little variability in threshold values for each metric for TN and TP was observed. The consistency of the threshold values measured across multiple metrics and habitats suggest that the thresholds identified in this study are ecologically relevant. Additional work to characterize the relationship between algal metrics, physical and chemical features, and nuisance algal growth would be of benefit to the development of nutrient thresholds and criteria. 相似文献
306.
Andrew J. Collins Kasi Bharath Vegesana Michael J. Seiler Patrick O’Shea Prasanna Hettiarachchi Frederic McKenzie 《The Environmentalist》2013,33(3):427-439
Many mathematical programs have been developed over the past 50 years to aid agricultural experts and other farming decision-makers. The application of these mathematical programs has seen limited success because their development has focused on mathematical theory as opposed to the requirements needed for application. This paper describes the development of two mathematical programs that were designed to integrate with a visualization simulation that aids a nontraditional group of agricultural decision-makers: illiterate Sri Lankan subsistence farmers. The simulation was designed to help these illiterate farmers make business decisions about their crop selection choices which, in turn, will help them develop their business plans required for obtaining bank micro-loans. This paper’s focus is on the use of linear programming as a potential tool to demonstrate the benefits of crop diversification and rotation to the farmer based on various available crop types. It also highlights the issues using such an approach. 相似文献
307.
Summary Two alternative hypotheses which attempt to predict how females within harems in polygynous species should behave toward one another were examined in a population of yellow-headed blackbirds (Xanthocephalus xanthocephalus). The hypothesis that females within a harem are co-operative was not supported. Females in large harems did not enjoy higher reproductive success than those in smaller harems and females within a territory did not initiate their nests close in time or space. The alternative hypothesis that females within a harem are competitive was also not supported. Nest density did not have a negative effect on female reproductive success, females within a territory did not initiate their nests far apart in time or space, and resident females were not very aggressive toward intruding female mounts during the settling period. The data support the idea that females settled independently of one another and had no effect on one another's reproductive success. 相似文献
308.
Concetta Tigano Adriana Canapa Venera Ferrito Marco Barucca Isabella Arcidiacono Alan Deidun Patrick J. Schembri Ettore Olmo 《Marine Biology》2006,149(6):1539-1550
Nine populations of Aphanius
fasciatus Nardo, 1827 from the central Mediterranean were analysed by examining the mitochondrial control region and the morphology of the bony elements of the skull and vertebral column, to study the degree of intraspecific differentiation of A. fasciatus considering the level of isolation of the different populations and the palaeogeographic history of the central Mediterranean area. Both the molecular and morphological analyses differentiate between the populations, even if the topologies of the two trees are different. Molecular and osteological investigations have consistently demonstrated a well-supported differentiation of the south-eastern Sicilian populations both within the same group (Tigano et al. in Ital J Zool 71:1124–1133, 2004a; Tigano et al. in Abstract volume XI European Congress of Ichthyology, Tallin, Estonia, 2004b), and from the populations from western Sicily, Tunisia and the island of Malta. The molecular results show that the nine populations are characterised by haplotypes that are well defined in relation to a probably limited gene flow; while, as regards the morphological data the differentiation found could be explained in terms of the geographic isolation of the various populations, although the influence of environmental factors, which differ greatly between the various sites where the populations live, cannot be ruled out. 相似文献
309.
310.
L. Joseph. Bachman Patrick J. Phillips 《Journal of the American Water Resources Association》1996,32(4):779-791
ABSTRACT: Base-flow samples were collected from 47 sampling sites for four seasons from 1990–91 on the Delmarva Peninsula in Delaware and Maryland to relate stream chemistry to a “hydrologic landscape” and season. Two hydrologic landscapes were determined: (1) a well-drained landscape, characterized by a combination of a low percentage of forest cover, a low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained landscape, characterized by a combination of an elevated percentage of forest cover, an elevated percentage of poorly drained soil, and low channel slope. Concentrations of nitrogen were significantly related to the hydrologic landscape. Nitrogen concentrations tended to be higher in well-drained landscapes than in poorly drained ones. The highest instantaneous nitrogen yields occurred in well-drained landscapes during the winter. These yields were extrapolated over the part of the study area draining to Chesapeake Bay in order to provide a rough estimate of nitrogen load from base flow to the Bay and its estuarine tributaries. This estimate was compared to an estimate made by extrapolating from an existing long-term monitoring station. The load estimate from the stream survey data was 5 ± 106 kg of N per year, which was about four times the estimate, made from the existing long-term monitoring station. The stream-survey estimate of base flow represents about 40 percent of the total nitrogen load that enters the Bay and estuarine tributaries from all sources in the study area. 相似文献