Environmental conceptual model

Figure 1. Conceptual model illustrating examples of major anthropogenic contaminant sources and contaminants, their distribution within the abiotic environmental media, their movement into biota with potential food chain contamination, and potential effects at the organismal, population, conmiunity and ecosystem level of organization.

CONCEPTUAL MODEL FOR THE ENVIRONMENTAL RISK ASSESSMENT OF POLLUTANTS ENTERING THE CASPIAN SEA... 

The effort of this presentation is to assess the links between environment and security based on conceptual model. This model will show the different factors, which have the influence on the relationship between the environmental change and security as the triggers, catalysts or interactors. 

This research presents a conceptual model describing the links between environment and security. This model uses the different factors (i.e., triggers, catalysts, or indicators) that influence the relationship between environmental changes and security. 

Environmental factors and security are tightly linked. Each affects the other. Because of multiple factors, linkages, and causalities, the relationships are complex and often difficult to understand. The use of a conceptual model, such as the one suggested in this paper, can help in managing the resolution of security issues caused by environmental stress. 

The US Environmental Protection Agency (USEPA 1998) describes problem formulation as an iterative process with 4 main components integration of available information, definition of assessment endpoints, definition of conceptual model, and development of an analysis plan. These 4 components apply also to probabilistic assessments. In addition, it is useful to emphasize the importance of a 5th component dehnition of the assessment scenarios. The relationships between all 5 components are depicted in Figure 2.1. Note that the bidirectional arrows represent the interdependency of the different components and imply that they may need to be revised iteratively as the formulation of the problem is rehned. 

As a result of the well-documented environmental concerns posed by coal combustion, and the disposal of CCPs, a large body of research has focused on characterizing the mechanisms of mobilization and attenuation of trace elements in coal and its ash. Based on their reported distribution in the solid phases of both source coals and coal ash, knowledge of the thermal transformations that occur to major mineral constituents during coal combustion, and a limited number of studies that have identified discrete solid phases of trace elements, a conceptual model of the chemical and mineralogical characteristics of trace elements in coal ash has been developed. 

Schuessler, W., Artinger, R., Kienzler, B. KlM, J. I. 2000. Conceptual modeling of the humic colloid-borne americium(III) migration by a kinetic approach. Environmental Science and Technology, 34, 2608-2611. 

The discussion above provides a brief qualitative introduction to the transport and fate of chemicals in the environment. The goal of most fate chemists and engineers is to translate this qualitative picture into a conceptual model and ultimately into a quantitative description that can be used to predict or reconstruct the fate of a chemical in the environment (Figure 27.1). This quantitative description usually takes the form of a mass balance model. The idea is to compartmentalize the environment into defined units (control volumes) and to write a mathematical expression for the mass balance within the compartment. As with pharmacokinetic models, transfer between compartments can be included as the complexity of the model increases. There is a great deal of subjectivity to assembling a mass balance model. However, each decision to include or exclude a process or compartment is based on one or more assumptions—most of which can be tested at some level. Over time the applicability of various assumptions for particular chemicals and environmental conditions become known and model standardization becomes possible. 

Develop a conceptual model of the environmental hazard to be investigated... 

The outputs of Step 1 illustrated for the case studies in a box on the next page include a list of the planning team members and their roles identification of decision makers a concise description and a conceptual model of the environmental problem in question and a summary of available resources and relevant deadlines for the project, such as the budget, personnel, and schedule. 

A second obvious line of research for the future must be that related to the development and improvement of computer-based simulation of long-term environmental behaviour of radionuclides. Most currently available models are still comparatively simple compared with the physical, chemical and biological complexity of environments they purport to represent but, as noted in Section 13.5, our ability to construct ever more complex conceptual models for predicting the future behaviour of radionuclides is improving. However, the more complex the model, the more demands it places on the basic thermodynamic data and knowledge of likely speciation. The challenge for the future will therefore be to produce high-quality data for model construction and to devise realistic ways to validate those models once produced. 

Boeston JJTI, Kopp H, Adriaanse PI, Brock TCM, Forbes VE. 2007. Conceptual model for improving the link between exposure and effects in the aquatic risk assessment of pesticides. Ecotoxicology and Environmental Safety 66 291-308. 

A conceptual site model is useful in helping to determine the type of environmental samples that is required. A conceptual model emphasizes the type and extent of the contamination, defines the pathways for contaminant migration, and identifies potential receptors (e.g., well users, surface water bodies, and food and feed material) (US EPA, 2002). 

The final component of the conceptual model is the temporal dimension whereby we shift from exposure near the point of chemical use and release to exposure through our food supply via environmental pathways. We postulated this for PCBs but lacked data on human exposure during peak usage. However, we are now in the midst of this shifting temporal trend for PBDEs. The temporal trends for PBDEs are discussed in Chapter 2. 

Sarmiento, G. 1992. A conceptual model relating environmental factors and vegetation formations in the lowlands of tropical south America. Pages 583-601. in P. A. Furley, J Proctor, and J. A. Ratter, editors. Nature and Dynamics of Forest-Savanna Boundaries. Chapman and Hall, London. 

Exposure assessment includes both qualitative and quantitative evaluations of the potential for exposure to site-related chemicals to occur. Assessments commonly address both current and likely future uses of the property (e.g., residential, commercial, industrial, and agricultural). Typically, a conceptual model is developed that summarizes how site-related chemicals may contact receptors (e.g., humans, wildlife, and ecological). The model includes identification of chemical sources, impacted media, potential movement through the environment, identification of the appropriate exposure scenarios, and identification of the points at which contact between receptors and site-related chemicals are likely to occur. Chemical concentrations in environmental media may be estimated based on site data and using statistical analyses and/or fate and transport modeling. An estimate of the dose (intake) attributable to contact with environmental media through significant and completed pathways is made for chemicals of concern at... 

The framework consists of three major phases (1) problem formulation, (2) analysis, and (3) risk characterization. Problem formulation is a planning and scoping process that establishes the goals, breadth, and focus of the risk assessment. Its end product is a conceptual model that identifies the environmental values to be protected (the assessment endpoints), the data needed, and the analyses to be used. 

An effective conceptual site model is essential for the identification of risk-based and non-risk remedial action objectives. The conceptual model should identify source areas complete, potentially complete, and incomplete exposure pathways and receptors. In addition, the conceptual model should identify contaminants, affected environmental media, and specific areas within the affected environmental media to be addressed by the selected remedial action. Although a conceptual model should be developed prior to initiation of the risk-based remedy selection process, the conceptual model should be updated as needed during the remedy selection process to reflect any changes in the understanding of the site. ASTM (2003), Standard Guide for Developing Conceptual Site Models for Contaminated Sites, provides guidance for the development of an effective conceptual model. 

It is important to note that in some cases environmental tracer data not only help to constrain model parameters, but also can indicate weaknesses of the conceptual model that underlies a numerical model. Reilly et al. (1994) and Sheets et al. (1998) showed that... 

Schneider, T., Vermeulen, R., Brouwer, D.H., Cherrie, J.W., ICromhout, H., and Fogh, CL. (1999). Conceptual model for assessment for dermal exposure. Occupational and Environmental Medicine. 56, 765-773. 

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