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Physical Models of Contaminant Transport
Published in Robert C. Knox, David A. Sabatini, Larry W. Canter, Subsurface Transport and Fate Processes, 1993
Robert C. Knox, David A. Sabatini, Larry W. Canter
Numerous reports of ground water pollution have caused considerable attention to be given to assessing and/or quantifying subsurface transport and fate processes. A large number of research-oriented field studies of the transport and fate of selected contaminants have been conducted or are ongoing. Laboratory-oriented microcosm studies can be used in lieu of, or as a supplement to, field studies. In this context, a microcosm can be defined as a controlled laboratory system which attempts to simulate, on a small scale, a portion of a real world subsurface environment. Pritchard and Bourquin (1983) have indicated that a microcosm study involves the establishment of a physical model or simulation of part of the ecosystem in the laboratory within definable physical and chemical boundaries under a controlled set of experimental conditions. Microcosm studies have been conducted on terrestrial, surface water, and ground water systems; the emphasis of this chapter will be on the use of such studies for examining organic contaminants in ground water and subsurface environment systems.
Natural attenuation in contaminated soil remediation
Published in Katalin Gruiz, Tamás Meggyes, Éva Fenyvesi, Engineering Tools for Environmental Risk Management – 4, 2019
A more sophisticated concept is the use of a microcosm, i.e. a small-scale artificial ecosystem, when a natural or similar artificial ecosystem is placed into the contaminated water, sediment, or soil under study and monitored. In such microcosms, complex natural processes can be simulated and detailed information can be obtained on natural attenuation in a contaminated environmental matrix: processes, trends and rates can be measured. The impacts of the planned interventions can also be estimated based on the response of the small-scale artificial ecosystem (see more in Gruiz et al., 2015c).
Data Analysis Methods for Assessing Eutrophication
Published in Michael Karydis, Dimitra Kitsiou, Marine Eutrophication A Global Perspective, 2019
Michael Karydis, Dimitra Kitsiou
The information collected during field work in the marine environment is valuable because it refers to the real system. However, it is difficult to understand complex ecosystem processes in the marine environment and the way system variables interact with each other. In addition, it is not possible to repeat an experiment in nature as environmental conditions are changing constantly. A useful tool for understanding ecosystem processes and interpreting field data in a better way is the use of microcosms. The advantage of using microcosms is that researchers can design experiments, repeat them and work with multispecies cultures simulating phytoplankton communities. The most widely accepted definition of microcosms has been given by NAS (1981). Microcosms can be defined “as samples from natural ecosystems housed in artificial containers and kept in laboratory environment. These systems are generally initiated by taking whole samples from ecosystems into the laboratory”. A microcosm system according to UNESCO should fulfill the following three criteria (Anonymous, 1991): (a) it has to be physically confined (b) it is preferable to be of multitrophic character and (c) the volume of the microcosm system should be sufficient so as to allow meaningful sampling; the usual volume of laboratory microcosms varies from 10–20 l up to 1 m3. Microcosm systems have had a significant contribution to understand phytoplankton dynamics, competition experiments, testing aspects of community theory and modelling natural processes (Karydis, 2015). Methodological aspects are given in Table 2.5. Although it seems to be a relatively simple approach, both the design of a microcosm system and the running of the experiment should be carried out with caution Alcazar et al. (1989). Microcosms should not be considered as small scale reproductions of the natural environment but only as a tool to understand physical, chemical and biological aspects related to eutrophication. Spatial scaling (volume of microcosm) and time scaling (duration of the experiment) are the main reasons that make replication of the natural conditions impossible. During planning, the researcher should take into account and make decisions on: boundary conditions, light, temperature, depth, ecological complexity and conditions referring to system’s initiation. A microcosm system is a system less complex than the natural environment but more complex than a unialgal or bialgal laboratory culture. The idea for researchers is to simplify the natural system mainly by reducing noise; at the same time to increase the complexity of a microcosm by carrying out multispecies experiments until a compatibility between the field information and the understanding of ecological processes can be achieved. A flow chart (Figure 2.5) explains the evolvement of ecological hypotheses, testing by combining field information with understanding marine processes in multispecies experiments.
Degradation of polypropylene-poly-L-lactide blends by Bacillus isolates: a microcosm and field evaluation
Published in Bioremediation Journal, 2022
Kimi Jain, H. Bhunia, M. Sudhakara Reddy
Microcosm experiments are ecosystem models, which contain natural biotic communities maintained under controlled conditions. This approach firmly establish the relationship between a toxicant and its effects on microbial communities (Caracciolo, Bottoni, and Grenni, 2013). The growth of bacteria increased with increase in time in inoculated microcosm experiments (Table 1). However, maximum log cfus were observed when inoculated with bacterial consortia compared to individual bacterial isolates. In general, log cfus are more in soil inoculated with bacteria without polymeric blends compared to polymer blends. The log cfus were also observed in sterilized soil though their numbers were significantly lower compared to inoculated ones (Table 1). Significant variation among the bacterial isolates and the polymeric blends were observed at all time periods. The interaction between polymers and bacterial inoculation was significant at 2 months only but not at 4 and 6 months period (Table 2). The less number of bacteria in polymeric blend samples compared to control might be due to formation of biofilm by bacteria in polymeric blend samples. Similar results was reported by us in our earlier studies, when these bacteria were grown in minimal media under laboratory condition in polymeric blend samples (Jain, Bhunia, and Reddy 2018).
Application of microcosm and species sensitivity distribution approaches in the ecological hazard assessment of 4-tert-butylphenol
Published in Chemistry and Ecology, 2018
Lei Wang, Jianmei Liu, Jining Liu, Lili Shi, Zhen Wang
Hazard assessment, exposure evaluation and risk characterisation are the general procedures for chemical ecological risk assessment [1]. As the first step of ecological risk assessment, hazard assessment is to qualitatively and/or quantitatively evaluate the potential impacts of chemicals on organisms, communities and populations. Traditional hazard assessment is based on standardised laboratory toxicity testing with standard test species. On the first tier, the outcome of the most sensitive species test is chosen and divided with an assessment factor to screen the chemical candidates with the potentially high hazard [2–4]. To further confirm the candidates’ hazards, the species sensitivity distribution (SSD) approach and the microcosm/mesocosm are adopted as the higher-tier approaches. Among the two, the SSD approach has been widely applied in the chemical ecological risk assessment [5–7]. The microcosm/mesocosm, consisting multiple species and environmental media, is considered to be a useful approach to determine the potential impact on ecosystems under more environmentally realistic conditions before admittance can further be evaluated. In recent years, different types of microcosms/mesocosms have been constructed to assess the chemical environmental risk assessment [8–15].