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41.
Marc Niggemann Jens Jetzkowitz Stefan Brunzel Matthias C. Wichmann Ronald Bialozyt 《Ecological modelling》2009,220(9-10):1339-1346
Distribution patterns of plants are affected by human activities such as creation, destruction or modification of habitats. However, another important question is to what extent humans shape plant distributions by acting as dispersal vectors. In order to answer this question we developed a simulation model for the spread of plant species between human settlements. This was done on the basis of extensive sociological and ecological data on a regional scale. With regard to the sociological data, human movement behaviour defined the amount of exchange between the settlements. Gardening types represented the potential habitat in our model. The ecological data was derived from a vegetation survey carried out in 2003, which was a repeat of a survey between 1974 and 1981 along the same transects. From these surveys, we studied the distributions of 13 species in 67 settlements. In our model, the earlier survey provided the data for the initial distribution. The simulated pattern was consequently compared with the distribution pattern in 2003. In the model, dispersal kernels based on patterns of human movement between settlements led to a better match with the distribution patterns than a null model simulating pure distance dependent dispersal for all species. This was statistically significant for seven of the thirteen species. A striking result was that alien species seem to benefit more from human dispersal than native species. We emphasize the importance of the sociological data on human movement behaviour in parameterizing our regional scale model. This study provides quantitative evidence on the impact of human movement behaviour on the distribution of plant species in suburban areas. 相似文献
42.
Stefan Gelcich Miriam Fernández Natalio Godoy Antonio Canepa Luis Prado Juan Carlos Castilla 《Conservation biology》2012,26(6):1005-1015
Territorial user rights for fisheries have been advocated as a way to achieve sustainable resource management. However, few researchers have empirically assessed their potential as ancillary marine conservation instruments by comparing them to no‐take marine protected areas. In kelp (Lessonia trabeculata) forests of central Chile, we compared species richness, density, and biomass of macroinvertebrates and reef fishes among territorial‐user‐right areas with low‐level and high‐level enforcement, no‐take marine protected areas, and open‐access areas in 42 100‐m subtidal transects. We also assessed structural complexity of the kelp forest and substratum composition. Multivariate randomized permutation tests indicated macroinvertebrate and reef fish communities associated with the different access regimes differed significantly. Substratum composition and structural complexity of kelp forest did not differ among access regimes. Univariate analyses showed species richness, biomass, and density of macroinvertebrates and reef fishes were greater in highly enforced territorial‐user‐right areas and no‐take marine protected areas than in open‐access areas. Densities of macroinvertebrates and reef fishes of economic importance were not significantly different between highly enforced territorial‐user‐right and no‐take marine protected areas. Densities of economically important macroinvertebrates in areas with low‐level enforcement were significantly lower than those in areas with high‐level enforcement and no‐take marine protected areas but were significantly higher than in areas with open access. Territorial‐user‐right areas could be important ancillary conservation instruments if they are well enforced. Derechos de Usuario Territoriales para Pesquerías como Instrumentos Accesorios para la Conservación Marina Costera en Chile 相似文献
43.
Stefan Bachu Mehran Pooladi-Darvish Huifang Hong 《International Journal of Greenhouse Gas Control》2009,3(4):468-473
Laboratory experiments reported in a companion paper were carried out to examine the chromatographic partitioning of impurities contained in a stream of CO2 injected into a deep saline aquifer. The solubility of the impurity gas in the CO2 stream compared to that of CO2, the in situ conditions of pressure, temperature and water salinity, and the concentration of the impurity gas affect the partitioning of the two gases. For CO2 streams containing H2S, numerical simulations reported here have successfully replicated the laboratory results including the breakthrough of CO2 ahead of H2S. Sensitivity analysis performed with the numerical model has shown that flow conditions, controlled by such parameters as medium permeability, pressure gradient, dispersion, gas mobility and flow direction, affect the breakthrough time and separation of the two gases, leading to delayed or earlier breakthrough, and increasing or decreasing the time lag between the breakthrough of the two gases. Vertical bottom-up flow leads to earlier breakthrough, while top-down flow leads to delayed breakthrough. These results are important in establishing monitoring strategies at CO2 storage sites and in evaluating the risks associated with the possible leakage of injected CO2 that contains impurities. 相似文献
44.
Jenny Bergqvist Stefan Gunnarsson 《Journal of Agricultural and Environmental Ethics》2013,26(1):75-99
The aim of this review is to assess the ethical implications of finfish aquaculture, regarding fish welfare and environmental aspects. The finfish aquaculture industry has grown substantially the last decades, both as a result of the over-fishing of wild fish populations, and because of the increasing consumer demand for fish meat. As the industry is growing, a significant amount of research on the subject is being conducted, monitoring the effects of aquaculture on the environment and on animal welfare. The areas of concern when it comes to animal welfare have here been divided into four different stages: breeding period; growth period; capturing and handling; and slaughter. Besides these stages, this report includes a chapter on the current evidence of fish sentience, since this issue is still being debated among biologists. However, most biologists are at present acknowledging the probability of fish being sentient creatures. Current aquaculture practices are affecting fish welfare during all four of the cited stages, both on physical and mental levels, as well as on the ability of fish to carry out natural behaviors. The effect fish farming has on the environment is here separated into five different categories: the decline of wild fish populations; waste and chemical discharge; loss of habitat; spreading of diseases; and invasion of exotic organisms. There is evidence of severe negative effects on the environment when looking at these five categories, even when considering the difficulty of studying environmental effects, due to the closely interacting variables. The ethical arguments and scientific evidences here reviewed have not all come to the same conclusions. Nevertheless, the general agreement is that current aquaculture practices are neither meeting the needs of fish nor environment. Thus, the obvious environmental and animal welfare aspects of finfish aquaculture make it hard to ethically defend a fish diet. 相似文献
45.
Panagiotou Constantinos F. Stefan Catalin Papanastasiou Panos Sprenger Christoph 《Environmental science and pollution research international》2023,30(6):14424-14438
Environmental Science and Pollution Research - A quantitative microbial risk assessment was conducted to assess the health risks associated with the exposure of agricultural workers to tertiary... 相似文献
46.
Bernhard Wimmer Marlies Hrad Marion Huber-Humer Andrea Watzinger Stefan Wyhlidal Thomas G. Reichenauer 《Waste management (New York, N.Y.)》2013,33(10):2083-2090
Stable isotopic signatures of landfill leachates are influenced by processes within municipal solid waste (MSW) landfills mainly depending on the aerobic/anaerobic phase of the landfill. We investigated the isotopic signatures of δ13C, δ2H and δ18O of different leachates from lab-scale experiments, lysimeter experiments and a landfill under in situ aeration. In the laboratory, columns filled with MSW of different age and reactivity were percolated under aerobic and anaerobic conditions. In landfill simulation reactors, waste of a 25 year old landfill was kept under aerobic and anaerobic conditions. The lysimeter facility was filled with mechanically shredded fresh waste. After starting of the methane production the waste in the lysimeter containments was aerated in situ. Leachate and gas composition were monitored continuously. In addition the seepage water of an old landfill was collected and analysed periodically before and during an in situ aeration.We found significant differences in the δ13C-value of the dissolved inorganic carbon (δ13C-DIC) of the leachate between aerobic and anaerobic waste material. During aerobic degradation, the signature of δ13C-DIC was mainly dependent on the isotopic composition of the organic matter in the waste, resulting in a δ13C-DIC of ?20‰ to ?25‰. The production of methane under anaerobic conditions caused an increase in δ13C-DIC up to values of +10‰ and higher depending on the actual reactivity of the MSW. During aeration of a landfill the aerobic degradation of the remaining organic matter caused a decrease to a δ13C-DIC of about ?20‰. Therefore carbon isotope analysis in leachates and groundwater can be used for tracing the oxidation–reduction status of MSW landfills.Our results indicate that monitoring of stable isotopic signatures of landfill leachates over a longer time period (e.g. during in situ aeration) is a powerful and cost-effective tool for characterising the biodegradability and stability of the organic matter in landfilled municipal solid waste and can be used for monitoring the progress of in situ aeration. 相似文献
47.
John R. Thene Heinz G. Stefan Ekaterini I. Daniil 《Journal of the American Water Resources Association》1989,25(6):1189-1198
ABSTRACT: A method to evaluate the effect of hydropower development on downstream dissolved oxygen (DO) is presented for a low head dam. Water, previously aerated during release over spillways and under gates, is diverted through the hydropower facility without further aeration. The oxygen transfer that occurs as a result of air entrainment at the various release points of a dam is measured. Oxygen transfer efficiencies are calculated and incorporated into an oxygen transfer model to predict average release DO concentrations. This model is used to systematically determine the effect of hydropower operation on downstream DO. Operational alternatives are investigated and a simple operational guide is developed to mitigate the effects of hydropower operation. Combinations of reduced generation and optimal releases from the dam allow the hydropower facility to operate within DO standards. 相似文献
48.
Heinz G. Stefan .Ruochuan Gu 《Journal of the American Water Resources Association》1991,27(6):967-978
ABSTRACT: Forced artificial mixing of temperature-stratified ponds, or small lakes or reservoirs, by liquid jets can enhance water quality and can also be energy efficient. Based on previous studies of jet mixing mechanics of stratified water bodies, a conceptual design approach is presented. The main “operational” and “system” design parameters are considered in the proposed method. Using minimization of a total cost estimate as a criterion, an iterative method for the selection of the number and size of the jets is developed and illustrated. 相似文献
49.
John B. Erdmann Heinz G. Stefan Patrick L. Brezonik 《Journal of the American Water Resources Association》1994,30(6):1043-1053
ABSTRACT: Suspended solids and ammonium concentration profiles measured at five locations in Duluth-Superior Harbor during July-October 1985 were analyzed to quantify wind and ship effects on sediment resuspension and resulting harbor water quality. Wind components from the SE quadrant correlated strongly with depth-averaged suspended solids concentrations that were unaffected by ship passage or thermal stratification. Winds from that quadrant have the largest fetch in the harbor. The highest correlation (r2= 0.93) was with the 6-hour average of the ESE wind velocity component. Multiple linear regression analysis of data from post-ship passage concentration profiles yielded numerical estimates of settling velocities of 0.08 to 0.25 cm s?1, typical of ship-resuspended sediments, and vertical eddy diffusivities of 4 to 13 cm2 s1. The results suggest that ambient vertical eddy diffusivities in the harbor are less than 4 cm2 s?1 in the absence of ship passages and with winds less than 5 m s?1 (10 knots). 相似文献
50.
Model simulations of dissolved oxygen characteristics of Minnesota lakes: Past and future 总被引:1,自引:0,他引:1
A deterministic, one-dimensional, unsteady numerical model has been developed, tested, and applied to simulate mean daily
dissolved oxygen (DO) characteristics in 27 lake classes in the state of Minnesota. Reaeration and photosynthesis are the
oxygen sources, while respiration, sedimentary, and biochemical water column oxygen demand are the sinks of oxygen in the
model. The lake classes are differentiated by surface area (A
s), maximum depth (H
max), and trophic status expressed as Secchi depth (Z
s). Because lake stratification is most important to lake oxygen dynamics, simulated DO characteristics are plotted in terms
of a stratification parameterA
s/H
max
0.25
and Secchi depthZ
s. Simulations provide DO profiles on a daily time scale. Specific DO characteristics of ecological and environmental interest
are epilimnetic DO, hypolimnetic DO, DO gradient from surface to bottom, and DO minima and maxima. Specific results are as
follows: Simulated mean daily and weekly DO values in the epilimnion of all lakes for both past and future climate scenarios
are near saturation over the summer season. Hypolimnetic DO values depend strongly on lake morphometry, trophic status, and
time throughout the summer season. Future climate conditions are specified as the historical records from 1955 to 1979, adjusted
(monthly) by the 2 × CO2 GISS model output to account for doubling of atmospheric CO2. With this climate change, weekly averaged epilimnetic DO is projected to drop by less than 2 mg/liter, and will remain above
7 mg/liter throughout the open water season. The hypolimnetic DO reductions after climate change are on the order of 2–8 mg/liter.
Periods of anoxia are longer by as much as 80 days. Those changes would alter water quality dynamics in lakes and have a profound
effect on lake ecosystems including indigenous fishes. The results presented are useful for evaluating environmental management
options. 相似文献