Methods for integrated assessment

Integrated assessment is an approach that seeks to involve all disciplines in policy-relevant assessment. The process aims to encompass environmental science, technology and policy problems. The aim is to establish an overview of the environmental issue in question that attempts to avoid the mistakes of the past associated with narrow, one-sided or unidimensional approaches. A number of methods are available for such assessments. However, they are also subject to a number of limitations, difficulties and dilemmas. Integrated methods are inherently complicated and the tradition is that only experts are involved. New more inclusionary procedures have to be devised in order to involve all stakeholders. They have to be involved in the framing of the issue and in the value judgements associated with the approach. The dilemmas cannot be solved by integrated approaches, but they can be mitigated via proper identification, analysis and evaluation of the gains and losses involved. In structuring the analysis the existence of ignorance has to be accounted for and communicated to the managers and the political decision makers. The ignorance/uncertainty aspects can be partially accommodated for via an intensification of feasible monitoring and research so as to minimise the risks of unpleasant surprises. Electronic Publication     

Uncertainty aspects in process safety analysis

Uncertainties of input data as well as of simulation models used in process safety analysis (PSA) are key issues in the application of risk analysis results. Mostly, it is connected with an incomplete and uncertain identification of representative accident scenario (RAS) and other vague and ambiguous information required for the assessment of particular elements of risk, especially for determination of frequency as well as severity of the consequences of RAS. The authors discuss and present the sources and types of uncertainties encountered in PSA and also methods to deal with them. There are different approaches to improve such analysis including sensitivity analysis, expert method, statistics and fuzzy logic. Statistical approach uses probability distribution of the input data and fuzzy logic approach uses fuzzy sets. This paper undertakes the fuzzy approach and presents a proposal for fuzzy risk assessment. It consists of a combination of traditional part, where methods within the process hazard analysis (PHA) are used, and “fuzzy part”, applied quantitatively, where fuzzy logic system (FLS) is involved. It concerns frequency, severity of the consequences of RAS and risk evaluation. In addition, a new element called risk correction index (RCI) is introduced to take into account uncertainty concerned with the identification of RAS. The preliminary tests confirmed that the final results on risk index are more precisely and realistically determined.     

Flammability of heat transfer fluid aerosols produced by electrospray measured by laser diffraction analysis

Accidental release of pressurized high flash point heat transfer fluids can result in fire and explosion hazard scenarios in the process industry. An experimental investigation on ignition of aerosols of a heat transfer fluid is carried out, and characterization of aerosol and its ignition process by non-intrusive laser diffraction technique is reported. Propagation speed of the aerosol combustion flame front as analyzed from the laser diffraction measurement agrees with high-speed visual camera observation. Flammability of the aerosol, which is based on the chances of the global flame appearance in the aerosol, is mainly controlled by aerosol droplet size and the droplet volume concentration.     

Risk measures constituting a risk metrics which enables improved decision making: Value-at-Risk

In this work, a novel approach is proposed for expressing the risks of process plants consisting of a large number of scenarios, in the form of a risk metrics of leading indicators to prevent potential high profile industry accidents. The methodology includes: 1) risk estimation of a portfolio by CPQRA (or QRA), 2) monetization of the tangible risks with the inclusion of the lost time of production, 3) estimation of the maximum portfolio loss using Value-at-Risk approach, 4) inclusion of intangible risks using FN-curve and, 5) generation of F$-curve of tangible risks. The proposed methodology can particularly help in understanding the stakes at risk by performing the overall cost-benefit analysis, for identifying the most risky scenarios and identifying critical equipments to enable better risk-informed decision making in order to adopt appropriate risk mitigation measures. This work establishes the groundwork for developing measures for understanding and comparing the large number of risk values derived from QRA studies for large portfolios. It will aid in less subjective decision making as it enables the decision maker to choose the most preferred portfolio option among alternatives. Decisions made with the accurate understanding of the consequences of risks can significantly reduce potential work-related fatalities, property losses and save millions of dollars.     

An ecological economics approach to the management of a multi-purpose coastal wetland

Three interrelated management problems—eutrophication of multiple use shallow lakes, sea level rise and flood risk mitigation and tourism pressures—are analysed in the context of an internationally important wetland area, the Norfolk and Suffolk Broads in the UK. The ecological-economic research findings presented should provide essential information to underpin the regulatory and management process in this internationally important conservation area. The relevant authority somehow has to integrate the maintenance of public navigation rights, nature conservation, and tourism promotion in a highly dynamic ecosystems setting. Because of the stakeholder conflicts, potential and actual, a more inclusionary decision-making procedure is required, and is currently being implemented.     

Direct coupling of supercritical fluid extraction-supercritical fluid chromatography for the determination of selected polycyclic aromatic hydrocarbons in aqueous environmental samples

A rapid and simple method is described for the quantitative determination of polycyclic aromatic hydrocarbons in aqueous environmental samples. A microscale on-line supercritical fluid extraction-supercritical fluid chromatography system using carbon dioxide is employed. The extract is analysed using capillary supercritical fluid chromatography with UV detection. Detection was carried out at 254 nm. An extraction efficiency of as high as 91% was obtained for the PAHs.     

Nutrient leaching from conifer needles in relation to foliar apoplast cation exchange capacity

Limited evidence to date suggests that acidic precipitation promotes leaching of nutrient cations from conifer foliage. In order to evaluate the relative contribution of the apoplast cation exchange complex and symplast nutrient pools to the leached ions, the magnitude of foliar leaching in response to acidic solutions was compared to foliar apoplast cation exchange capacity (CEC) for two conifer tree species (Pseudotsuga menziesii and Picea engelmanii). Leaching potential was determined by immersing detached needles in acidic solutions (pH5.6, 3.1, 2.1) over a range of time intervals (1, 4, 8, 24 h) and foliar apoplast cation exchange capacity was determined by potentiometric titration. Leaching increased with decreasing pH and increasing time of immersion. At pH values 2.1 and 3.1, equivalents of H+ depleted from the acidic solutions approximated equivalents of base cations gained by the solutions. Maximum amounts leached were less than 40 microeq g(-1) dry weight of needles for the combination of calcium, magnesium and potassium. Measured foliar apoplast CEC for these species was approximately 120 microeq g(-1) dry weight of needles. These relative magnitudes indicate that the apoplast rather than the symplast provided the leached ions. Because the apoplast foliar cation exchange capacity appears to be large relative to the rates of H+ diffusion across the cuticle, it may help to insulate the symplast nutrient reservoir from exposure to the H+ of acidic solutions bathing the foliage.