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Risk assessment and risk management for nitrate-contaminated groundwater supplies
Abstract
The overall aim of this study is to develop a risk-assessment/risk-management methodology for nitrate-contaminated groundwater supplies. For this study, the nitrate risk-assessment process consists of both exposure assessment and human health risk assessment. The exposure assessment identifies the source and amount of nitrate contamination and calculates the rate and magnitude of nitrate movement throughout both the unsaturated and saturated zones. The human health risk assessment determines the relationship between the level of nitrate exposure and the incidence of adverse health effects. Nitrate risk management describes the process of evaluating regulatory actions and, if action must be taken to reduce the human health risks, it includes the process of evaluating different nitrate risk-management strategies so that a proper strategy is determined. If action must be taken to reduce human health risks from nitrates in groundwater supplies, several nitrate risk-management strategies can be developed based on the acceptable levels of human health risks, the reasonableness of nitrate-control cost, and the technical feasibility of nitrate-control methods. High-cost strategies may provide a high degree of human health protection, while low-cost strategies may not provide adequate protection. That is, the objectives of maximizing the risk reduction while minimizing the cost are in conflict. Thus, the ultimate goal of nitrate risk management is to determine which strategy best satisfies considerations of risk, cost, and technical feasibility (i.e., a risk-cost-feasibility trade-off analysis). In this study, uncertainties related to the nitrate risk-assessment/risk-management process and their impact on results are characterized with an application of fuzzy-set theory and incorporated into the trade-off analysis. When a frequency-based estimation (such as cancer risk assessment) is available, a combined probabilistic/fuzzy-set analysis is used to reflect the uncertainty in the values represented by probability. The results of this study can be used to assist decision makers (such as local and state agencies) in: (1) performing a time-series analysis on groundwater nitrate levels that would result from each nitrate risk-management strategy, (2) estimating human health risks (i.e., methemoglobinemia and cancer risks) due to nitrate intake, (3) determining whether or not an action should be taken to reduce the health risks, and (4) selecting an appropriate nitrate risk-management scheme if action must be taken. (Abstract shortened by UMI.)
Subject Area
Civil engineering|Hydrology
Recommended Citation
Lee, Yong Woon, "Risk assessment and risk management for nitrate-contaminated groundwater supplies" (1992). ETD collection for University of Nebraska-Lincoln. AAI9314411.
https://digitalcommons.unl.edu/dissertations/AAI9314411