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761.
The study of ecological differences among coexisting microparasites has been largely neglected, but it addresses important and unusual issues because there is no clear distinction in such cases between conventional (resource) and apparent competition. Here patterns in the population dynamics are examined for four species of Bartonella (bacterial parasites) coexisting in two wild rodent hosts, bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus). Using generalized linear modeling and mixed effects models, we examine, for these four species, seasonal patterns and dependencies on host density (both direct and delayed) and, having accounted for these, any differences in prevalence between the two hosts. Whereas previous studies had failed to uncover species differences, here all four were different. Two, B. doshiae and B. taylorii, were more prevalent in wood mice, and one, B. birtlesii, was more prevalent in bank voles. B. birtlesii, B. grahamii, and B. taylorii peaked in prevalence in the fall, whereas B. doshiae peaked in spring. For B. birtlesii in bank voles, density dependence was direct, but for B. taylorii in wood mice density dependence was delayed. B. birtlesii prevalence in wood mice was related to bank vole density. The implications of these differences for species coexistence are discussed. 相似文献
762.
In June 1990, scientists from the US Environmental Protection Agency's (EPA) Office of Radiation Programs (ORP), and the Woods Hole Oceanographic Institution (WHOI), travelled to Sevastopol in the Soviet Union to work with radioecologists and marine scientists from the USSR Institute of Biology of the Southern Seas (IBSS). the purpose of this cooperative programme was to conduct a monitoring survey for radioactivity in the northwestern Black Sea. Samples of sediment, surface and in-situ water, and biota were collected from fourteen stations for post-survey radionuclide analyses to determine levels of radioactivity in the Black Sea environment resulting from the Chernobyl nuclear power plant explosion and subsequent transport of radioactivity via the Dnepr and Danube rivers. This paper presents the preliminary data for caesium-137 and caesium-134 in sediment samples analyzed by the EPA/ORP. Caesium-137 was measured at four shallow (20-114 m) stations on the shelf near the mouth of the Dnepr and Danube Rivers, but was not detected in sediments from comparable depths at stations further off shore or in slope sediments at depths of 510-1288 meters. Caesium-134 was detected only in sediments from the shallow-water station nearest to the Danube River. 相似文献
763.
This paper uses an environmental partitioning model to evaluate the concentration of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) in various environmental media. These concentrations are then used to estimate the amount of TCDD entering the food chain and the average daily intake of TCDD by the general population of the US. The food chain accounts for 98% of human exposure to TCDD. The model estimated the average daily intake of TCDD to be 0.05 ng/day. 相似文献
764.
Integrating Bioassessment and Ecological Risk Assessment: An Approach to Developing Numerical Water-Quality Criteria 总被引:1,自引:0,他引:1
Bioassessment is used worldwide to monitor aquatic health but is infrequently used with risk-assessment objectives, such as supporting the development of defensible, numerical water-quality criteria. To this end, we present a generalized approach for detecting potential ecological thresholds using assemblage-level attributes and a multimetric index (Index of Biological Integrity—IBI) as endpoints in response to numerical changes in water quality. To illustrate the approach, we used existing macroinvertebrate and surface-water total phosphorus (TP) datasets from an observed P gradient and a P-dosing experiment in wetlands of the south Florida coastal plain nutrient ecoregion. Ten assemblage attributes were identified as potential metrics using the observational data, and five were validated in the experiment. These five core metrics were subjected individually and as an aggregated Nutrient–IBI to nonparametric changepoint analysis (nCPA) to estimate cumulative probabilities of a threshold response to TP. Threshold responses were evident for all metrics and the IBI, and were repeatable through time. Results from the observed gradient indicated that a threshold was 50% probable between 12.6 and 19.4 g/L TP for individual metrics and 14.8 g/L TP for the IBI. Results from the P-dosing experiment revealed 50% probability of a response between 11.2 and 13.0 g/L TP for the metrics and 12.3 g/L TP for the IBI. Uncertainty analysis indicated a low (typically 5%) probability that an IBI threshold occurred at 10 g/L TP, while there was 95% certainty that the threshold was 17 g/L TP. The weight-of-evidence produced from these analyses implies that a TP concentration > 12–15 g/L is likely to cause degradation of macroinvertebrate assemblage structure and function, a reflection of biological integrity, in the study area. This finding may assist in the development of a numerical water-quality criterion for TP in this ecoregion, and illustrates the utility of bioassessment to environmental decision-making. 相似文献
765.
Researchers attempting to integrate socio-economic data in watershed planning often draw on nationally collected census data. However, there are critical limitations to the usefulness of this type of data for decision makers operating at the watershed scale. In this paper we demonstrate the relevance of spatially referenced socio-economic data collected using mail surveys to random selections of rural landholders. The issue explored was dryland salinity management in two large watersheds in the Murray-Darling Basin of south-eastern Australia. Contrary to the assumptions underlying public policy in Australia, but consistent with the literature on farmer knowledge, comparisons of expert maps and landholder identified salinity sites suggested that landholders in these watersheds had excellent knowledge of the current extent of salinity on their property. Our research also suggested that salinity education was a sound investment by governments. At the same time, the expert maps failed to predict half of the saline affected sites identified by landholders. Accurately mapping the extent of salinity would seem a first step in addressing this nationally significant land degradation issue. 相似文献
766.
Grassroots watershed associations have formed as an avenue to facilitate public involvement in protecting watersheds. Growth in the number of watershed associations has created a need to evaluate whether their existence enhances environmental protection by local communities. In this research, environmental protection was measured by the number of watershed protection activities conducted and amount of funding directed towards protecting surface waters by non-profit, volunteer organizations. Regression models were utilized to examine the influence of population demographic and watershed characteristics variables to explain the formation of watershed associations along with watershed protection activities and funding. Regression results showed that the presence of watershed associations had positive impacts on both the number of activities and financial resources acquired. The results confirm that watershed associations enhance the ability of communities to obtain funding and to implement watershed protection actions. Thus, watershed associations serve as an effective institution for promoting environmental protection. 相似文献
767.
Summary This article presents a brief overview of the more severe problems which must be addressed by natural resource planners and managers in the eighties.Professor Fred Curtis is senior author of this paper which, although written in a style which offers light reading, serves as a reminder from Canada that the resource problems of the '70s are ever present today in the '80s. The address given is that of Prof. Curtis. Paul Simpson-Housley is a member of staff in the Department of Geography, York University, 4700 Keele Street, Downsview, Ontario M3J 1P3 and Messrs Kent and Blakely maybe contacted through the senior author. 相似文献
768.
Elisabeth Mathijs Ambroos Stals Leen Baert Nadine Botteldoorn Sarah Denayer Axel Mauroy Alexandra Scipioni Georges Daube Katelijne Dierick Lieve Herman Els Van Coillie Mieke Uyttendaele Etienne Thiry 《Food and environmental virology》2012,4(4):131-152
Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII.4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed. 相似文献
769.
Xiaoliang Wang Curtis Robbins S. Kent Hoekman Judith C. Chow John G. Watson Dennis Schuetzle 《Frontiers of Environmental Science & Engineering in China》2011,5(3):320-330
Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising
energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important
to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling
system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks:
a BioMax?15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that
uses rice hulls and woodchips as feedstocks. PM2.5 mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m−3, which were significantly lower than the maximum level for catalyst protection (500 μg·m−3) and were 2–3 orders of magnitude lower than those in BioMax?15 syngas (2247–4835 μg·m−3). Ultrafine particle number concentration and PM2.5 chemical constituents were also much lower in the IBR syngas than in the BioMax?15. The dilution sampling system enabled
reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at
very low concentrations (∼1 μg·m−3), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars
in raw syngas (∼1 g·m−3). 相似文献
770.
Lore Lannoo Karuna R. M. van der Meij Mireille N. Bekker Luc De Catte Sarah Deckers Koenraad Devriendt Nele Roggen Robert-Jan H. Galjaard Janneke Gitsels-van der Wal Merryn V. E. Macville Linda Martin Erik A. Sistermans Kristel Van Calsteren Joachim Van Keirsbilck Neeltje Crombag Lidewij Henneman 《黑龙江环境通报》2023,43(3):294-303