Theoretical Considerations Regarding Hazards And Risks Environmental Sciences Essay

The cognition of natural and technological hazards is of the extreme importance for carry oning hazard and impact appraisal surveies, every bit good as land usage planning and exigency response planning. This whole mechanism significantly contributes to the society ‘s sustainable development.

For the overall comprehension of this issue, it is extremely relevant to specify the repeating constructs of this work, viz. jeopardy and hazard.

The jeopardy construct

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To get down with, a short ethimological analysis of the word “ jeopardy ” is necessary. This term has been taken by the Gallic from Arabic, where it means dice game ( Mac and Petrea, 2002 ) . Harmonizing to the Longman Dictionary of Contemporary English, 2010, ” jeopardy ” means “ something that may be unsafe, or cause accidents or jobs ” .

In 1992, the United Nations International Decade for Natural Disaster Reduction secretariat published a multilingual lexicon so as to clear up and unite the significances of such footings. In this dictionary, jeopardy is defined as “ a baleful event or the possibility for a phenomenon with destructive potency to look in a individual part and in a given period of clip ” .

Another definition is offered by the Grand Larousse Dictionary, volume V, cited by ZA?voianu and Dragomirescu in 1994: “ accidental and, by and large, unforeseeable interface between two or more causal series, whose common dealingss are purely defined in every minute and whose comparative independency can merely be attributed to our ignorance and impotence ” .

Scheidegger, 1994, cited by ArmaAY , 2003 defined jeopardy as “ the chance of rapid alteration of a system ‘s province or stable conditions ” . In 1997 Grecu defined this construct as “ the possibility that a potentially annihilating phenomenon appears in a certain period of clip and in a certain part. ”

In 1999 Octavia Bogdan and Elena Niculescu specify jeopardy as “ a random phenomenon on a big graduated table, unpredictable, a deficiency of finding between clip and infinite, a qualitative lap, a threshold in the system ‘s development, downloading immense energy and doing upset, instability on the natural environmental development ‘s graduated table, in its manner towards a new province of equilibrium ” .

In 2000 Ozunu defines the construct under treatment as aˆza state of affairs with the potency of an accident ” ; in 2001, BA?lteanu states that jeopardy is aˆza endangering event, stand foring the possibility for a potentially detrimental phenomenon to go on. ” Harmonizing to him, harm to people, goods and the environment occur.

Alexander, 2000, cited by Thywissen, 2006, defines hazard as aˆzan utmost geophysical event that can do a catastrophe. aˆsExtreme ‘ refers to an either positive or negative characteristic, harmonizing to the tendency it is related to. The jeopardy ‘s cardinal properties are: location, clip, magnitude and frequence. Many utmost phenomena are perennial in clip and predictable in footings of location. We define hazard as an utmost event arising from the biosphere, lithosphere, hydrosphere or atmosphere. ”

Mac, 2003, considers hazard as aˆzthe beginning of an utmost event with energy discharge in a certain minute and with a instead unforeseeable magnitude. In fact, jeopardy can be referred to as aˆza phenomenological class that refers to objects and phenomena ( air multitudes, H2O, lithomass, biomass, people, twisters, epidemics, temblors, avalanches etc. ) , to their actions ( inundations, clay flows, landslides, illness etc. ) every bit good as to their characteristics ” ( Mac, 2003 ) .

In 2003, Cardona, cited by Thywissen, 2006, offers another definition of the term: aˆzthe possibility for a natural and unsafe event to go on in a certain clip and infinite ” . Generally, the construct of jeopardy is used to mention to a latent danger or to an external hazard factor of a system or exposed capable.

A jeopardy is composed of three basic elements ( C. A. Ericson, 2005 ) :

1. Dangerous belongings – the basic beginning of the danger that creates the jeopardy, i.e. a unsafe energy beginning etc.

2. Initiation mechanism – the event that triggers or initiates the happening of the jeopardy, transforming the jeopardy from a inactive province to an active 1.

3. Target and menace – the individual, object, state of affairs vulnerable to damage caused by the materialisation of the jeopardy.

These three elements compose the jeopardy trigon shown in figure 2.1:

Figure 2.1 – The jeopardy trigon ( C. A. Ericson, 2005 )

The jeopardy trigon illustrates that all three above mentioned are interlinked. All three constituents are necessary in order to organize a jeopardy. The remotion of one portion of the trigon consequences in the riddance of the jeopardy, because it can non take to an incident.

By extenuating the induction mechanism the chance of the incident to happen is reduced, and accordingly by extenuating an component of the unsafe belongings or mark and menace the badness of the incident will be reduced. These theoretical facets and categorization prove to be important in any undertaking refering jeopardy designation, extenuation, and hazard and impact appraisal.

The basic construct of jeopardy theory can be summarized as follows ( C. A. Ericson, 2005 ) :

Hazards are deterministic entities and non a random 1s ;

Hazards are constituted accidentally in systems ;

Hazards are predictable and hence can be controlled and prevented ;

Hazards can be identified by their constituents ;

Hazards will happen taking history of the constituents involved ;

Hazards consequence in incidents.

One of the term ‘s most recent definitions is the 1 offered in 2009 by the International Strategy for Disaster Reduction Secretariat: “ a unsafe phenomenon, substance, human activity or status that may do loss of life, hurt or other wellness impacts, belongings harm, loss of supports and services, societal and economic break, or environmental harm. ”

As it can be noticed from the above-named definitions, jeopardy is characterized through certain parametric quantities, such as geographical location, strength ( magnitude ) , frequence and its chance to go on. In many of these definitions, one can detect the accent lies upon entropy, deficiency of determinacy and capriciousness ( Mac 2003 ) . In order to measure these phenomena ‘s possibility to go on, surveies refering their extreme values are considered. Furthermore, in all these definitions the construct of jeopardy has a instead negative intension, since it implies a certain grade of danger. Hazard can take the signifier of some remarkable phenomena or of some combines 1s, in footings of infinite and clip.

Hazard appraisal purposes at identifying: the likeliness of a specified jeopardy to go on in the hereafter, in a certain period of clip, its magnitude and impact country ( Pine, 2009 ) . For the appraisal of certain jeopardies such as inundations, temblors and vents there are good established, predefined methods. The consequences of these ratings are extremely relevant in footings of lucubrating land usage planning schemes and in implementing accident bar steps.

Hazard vs. hazard

The term “ jeopardy ” is closely related with the term “ hazard ” . Not few are the instances when confusion arises between the significances of these two constructs. This is why it is necessary to separate between them. Hazards are phenomena whose manifestations can barely be predicted and controlled. They have negative effects on population and on the environment. Imputing the characteristic of jeopardy to a natural or anthropic phenomenon is non conditioned by the production of material harm or by the being of victims, but by the potency of these effects to go on. ( Baldea, 2007 ) .

Merely when that jeopardy or phenomenon exceeds certain critical values, taking to material harm or casualties, does it go hazard. Therefore, a jeopardy is the menace that an event might go on and non the event itself. Should it impact a human community, to a certain extent, it becomes hazard.

It must be mentioned that the term “ hazard ” is attributed assorted significances, being used in different contexts. Its definitions have societal, economic, political and environmental values. In order to better understand its deductions, a short diachronic analysis is necessary.

To get down with, the term under treatment was foremost used in the fifteenth century, when it referred to the trade ‘s fiscal danger ( Proske, 2008 ) . Initially, this construct was associated with economic activities, being so used in the theory of chance and gaming. In the nineteenth century it is integrated in economic system, experiential doctrine and determination theory, whereas in the twentieth century it was used as political term in atomic engineering in order to gauge the degree of security that was acceptable for people.

Until the 8th decennary of the old century constructs such as hazard, jeopardy and hazard direction were associated with natural phenomena. Hazard and natural or anthropic jeopardies analysis became an interdisciplinary kingdom of survey with its specific nomenclature merely in the last 30 old ages.

The Longman Dictionary for Contemporary English, 2010, defines hazard as “ the possibility that something bad, unpleasant, or unsafe may go on ” .

In 2007 ISDR defines hazard as “ the combination of the chance of an event and its negative effects ” . In 1999 Octavia Bogdan and Elena Niculescu define hazard as “ the existent chance or possibility for a phenomenon to go on ” . This event is someway expected and has negative reverberations, in response to which world can merely be inactive.

Another definition is offered by Ozunu in 2000: “ the chance that the existing jeopardy turns into an accident ” .

Alwang, 2001, cited by Thywissen, 2006, defines hazard as “ the possible distribution of some known or unknown events. These are characterized by magnitude, frequence, continuance and history ” .

In the same twelvemonth, Peduzzi, cited by Brauch, 2005, considers risk aˆza step of possible losingss generated by a jeopardy of a certain magnitude, produced in a certain part and period of clip ” .

It must be stated that natural events can turn into social hazards when they surpass the immediate capacity of being counteracted or absorbed. They are, in most of the instances, utmost events. An utmost natural event is any event or series of events that shows a fleeting or durable fluctuation as compared to its common values. ( White, cited by ArmaAY , 2003 )

The widely accepted definition of hazard as the merchandise between the chance for an event to go on and the negative effects it may hold is expressed as follows:

R= F x C ( Eq. 2.1 )

where:

R- hazard ( losses/unit of clip ) , F- frequence of happening ( no. of events/unit of clip ) , C- effects ( losses/event ) .

Hazard can besides be defined as “ the chance of human exposure, of semisynthetic goods and of the environment to the action of a jeopardy of a certain magnitude and their exposure towards it ” ( BA?lteanu, 2005 ) .

For Petrea, 2009, hazard is “ the possibility that some negative effects for human communities or losingss ( human lives, hurts, diminished agencies of subsistence, goods, harm of the environmental constituents ) appear as an interaction between natural or anthorpic jeopardies and territorial exposure ” .

This expression associates two distinguishable elements, viz. the jeopardy and the receiving system ( in most of the instances, a certain population ) .

In most of the instances, the undermentioned expression is used:

R= Hazard x Vulnerability ( Eq. 2.2 )

This underlines the relation between an event and its effects. In a certain country, the hazard is comparatively changeless. What differs is community exposure, in footings of its reaction to menaces or its degree of readiness to confront them. Harmonizing to the above-named expression, hazard may match to a high-frequency jeopardy and a low exposure or to a low-frequency jeopardy and high exposure. The disadvantage of this expression is that it does non see the population denseness, i.e. its exposure to hazard. Mitchell, 1990, cited by Brauch, 2005, completes this expression, sing jeopardy as a map of hazard, exposure, exposure and response:

Hazard= degree Fahrenheit ( hazard ten exposure x exposure x response ) ( Eq. 2.3 )

where:

hazard – the chance that negative effects appear,

exposure – the size and characteristics of the open population,

exposure – the potency of harm to bring forth and response refers to the enforced steps for hazard decrease.

Another definition is given by Ozunu and Anghel in 2007:

R = F x C x V ( Eq. 2.4 )

where:

R – hazard ;

F- frequence ;

C – effects ;

V- exposure ( – ) .

The harm produced as a consequence of a catastrophe is really the consequence of the interaction among physical environmental factors ( clime, H2O, landscape etc. ) , population ( societal categories, civilization etc. ) and the built environment ( edifices, substructure etc. ) ( Mileti, 1999 ) . Therefore, jeopardy can be considered the pre-disaster state of affairs, when hazard does non look. A phenomenon ‘s development has three phases, more precisely: the jeopardy one, when merely hazard appears, the hazard phase, when jeopardy can impact human society and, eventually, the catastrophe. ( Alexander, 1993 )

In decision we can province that there are two types of hazards, viz. an acceptable one, where losingss are tolerable for the population and catastrophe, when losingss can non be tolerated by the local community.

Categorization of jeopardies and hazards

As antecedently mentioned, jeopardies and hazards are defined and characterized in multiple ways. In this chapter, a categorization is presented harmonizing to the most relevant features: beginning, effects, frequence, affected surface, etc.

Categorization after beginning

The categorization of jeopardies harmonizing to their beginning is presented in table 2.1:

Table 2.1 – Categorization after beginning ( BA?lteanu, 2005 ) :

Natural jeopardies

Endogenous

Volcanic eruptions, seismicity

Exogenous

Climatic

Cyclones, twister, storms, lightning, hail, hoar, drouth, etc.

Geomorphologic

Mass supplanting, eroding

Hydrologic

Flash-floods

Oceanographic

Rise of planetal ocean, El Nino

Biological

Epidemics, viruses, insect invasions

Anthropogenetic jeopardies

Technological

Industrial, agricultural, transport accidents

Human

( Benedek, 2002 )

Social

Poverty, unemployment, urbanisation, life style

Medical

Infectious, viral, chronic, degenerative diseases

Demographic

Emigration, population growing, aging of population

Political

Territorial, political differences

2.3.2 Classification harmonizing to the manifestation manner

The categorization of jeopardies harmonizing to their manifestation manner is presented in table 2.2 ( GoA?iu and Surdeanu, 2008 ) :

Table 2.2 – Hazards categorization harmonizing to their manifestation

Violent jeopardies

– temblors

– vents

– severe storms, twister, etc.

– local storms with hail etc.

– catastrophic landslides, avalanches

Hazards with progressive development

– Mediterranean disturbances ( Mediterranean cyclones with retrograde development )

Hazards with slow development

– drouth

– severe drouth

– radiation and vaporization mists

2.3.3 Categorization after continuance

Hazards can besides be classified harmonizing to their temporal development. Harmonizing to ArmaAY , 2008 the categorization after the continuance of jeopardies is presented in table 2.3:

Table 2.3 – Hazards categorization harmonizing to their continuance

With sudden happening and rapid development

Endogenous, tectonic jeopardies, sudden mass supplantings, flash – inundations

With long continuance

Terrain debasement, drouths, desertification

2.3.4 Categorization after affected surface, and continuance of effects

Hazards can endanger assorted extents of a district. Within the affected surface the effects can prevail for assorted sums of clip. Harmonizing to Chardon, 1990 and Grecu, 1997 a categorization after the affected surface and the continuance of effects is presented in table 2.4:

Table 2.4 – Hazards categorization harmonizing to affected surface and continuance of effects

Calamity type

Affected surface

Duration of effects

Examples

Giga calamity

100 – 510 mil. km2

several old ages

volcanic eruptions

Mega calamity

1 – 100 mil. km2

several months

big temblors

volcanic eruptions

tropical drouths

Meso calamity

10.000 – 1.000.000 km2

several hebdomads – a few months

volcanic eruptions

temblors,

cold moving ridges

tropical storms

Calamity

100 – 10.000 km2

a few hebdomads

little temblors, twister

exceeding rains

Local phenomena

under 100 km2

a few yearss – a few hebdomads

landslides

hail storms

The present thesis focuses on the appraisal with optoelectronic engineerings of two major jeopardies from the above mentioned categorizations:

Natural jeopardies – volcanic ash by active and inactive remote feeling

Technological jeopardies – monitoring and patterning the impact of SO2 emanations associated with big burning workss.

NATECH jeopardies

This thesis focuses both on natural and anthropogenetic jeopardies individually. In order to develop efficient schemes for measuring hazards and impact, the NATECH ( natural jeopardies which trigger technological accidents ) rule is necessary to be considered when measuring either of the two above mentioned types of jeopardy. Current EU ordinances in the field of hazard appraisal and catastrophe direction ( European Commission, 2010 ) stress the necessity of a multi-risk and multi-hazard attack in all natural and anthropogenetic jeopardy and hazard surveies.

Therefore, there is a turning involvement in the scientific community and among stakeholders sing natural jeopardies which trigger technological accidents ( NATECHs ) . NATECHs have important negative effects on human wellness, the environment and the economic system. The addition in the figure of such events is closely linked with the exponential technological development of the past decennaries, due to the variegation of engineerings, the turning figure of personal exposed, and the substances used in the technological procedures. The effects of NATECH events have become more terrible within this timeframe chiefly due to the exposure of the population life near these installations.

Given these facts, there is an pressing demand for raising consciousness about bar and readiness steps refering these high effect low chance events ( Cruz and Okada, 2008 ) . Due to the complexness of NATECH events, their word picture is instead hard, and many NATECHs are analyzed and assessed as separate natural or technological events ( Embelton and Embelton-Hamann, 1997 ) . One needs to take into history that the effects of such an event differ in complexness from the effects of the two events taken individually ( Cruz and Krausmann, 2008 ) . Therefore, there is a demand for scientific research on the interactions and dealingss between natural jeopardies and technological accidents. Addressing NATECHs requires a combined attempt of industrial and technological hazard direction specializers working together with specializers concentrating on natural jeopardy probes.

The specific features of a NATECH event ( Domino impacts, multiple effects ) need specific steps for the bar, response and recovery after such an event. An integrated hazard and impact direction scheme must include the possibility of NATECHs to happen, and necessitate specialised planning for extenuation, response, and recovery ( Ozunu et al. , 2011 )

The Activities Report On the Collaboration Agreement between the International Strategy for Disaster Reduction of the United Nations and the Directorate General Joint Research Center of the European Commission proposes a scheme for the extenuation of NATECH events by:

iˆ Industry hazard direction specifically turn toing the possible impacts of natural jeopardies on technological installings. Additional hazard direction processs ( Figure 2.2 ) in order to cut down the exposure to NATECHs: the usage of excess safety systems, natural jeopardy resistant designs, guidelines to inform industry about NATECH planning, and strategic arrangement of risky substances inside a unit.

Figure 2.2 – Catastrophe Management processs ( Torok et al. , 2009 )

Efficient Emergency planning, including bar and extenuation, and response planning for NATECHs at all degrees of authorities. The purpose of the Risk Analysis procedure is to cut down uncertainnesss by increasing safety degrees by developing more efficient Emergency Plans, offering immediate determinations, detailed, accurate and steady instructions ( ( Torok et al. , 2009 ) iˆ Land usage planning, as an of import tool for setting-up insularity margins in order to protect occupants populating near risky installations. ( Christou et al.,2006 quoted by Torok et Al. 2011c ) . Article 13 of the SEVESO III Directive ( Directive 2012/18/EU ) provinces that: “ Member States shall guarantee that the aims of forestalling major accidents and restricting the effects of such accidents for human wellness and the environment are taken into history in their land-use policies or other relevant policies ”

Information and instruction of the populace, authorities bureaus and all stakeholders involved in exigency direction, including decision-makers.

iˆ Public engagement in NATECH hazard decrease planning, in order to better understand the perceptual experience of the degree of the NATECH hazard and the degree at which this hazard is considered acceptable ( Ozunu et al. , 2011 )

Qualitative and quantitative methods for placing jeopardies and measuring hazards

A systematic designation of possible environmental impacts atmospheric pollutants have, every bit good as a strict analysis of their magnitude is required. The intent of such a procedure can be divided in two major issues, on one manus to bring forth quantitatively accurate appraisal of peculiar hazard and a comprehensive list of possible environmental impacts, and on the other manus produce a principle for doing public policy determinations that is both good reasoned, and recognized as legitimate and acceptable by the socio-economical factors.

A complex environmental impact appraisal ( EIA ) and hazard appraisal ( RA ) methodological analysis requires assorted sets of informations about beginning footings, emanations, imissions, exposure, local weather forecasting, terrain informations etc.. Most of the air scattering theoretical accounts have been developed for the anticipation of lee concentration of air pollutants and for the appraisal of short-run and medium-term effects of these pollutants. The quality of consequences obtained utilizing these patterning systems depend largely on the versatility and quality of input informations and the right pick of the theoretical account ( Torok et al. , 2011a ) .

In instance of EIA surveies, the medium-term effects appraisal requires emanation and meteoric informations for several months in order to obtain a realistic distribution of the largely contaminated countries. The consequence of the complex terrain on the air motion in the commixture bed is important. Therefore the meteoric information for the modeling period should be calculated sing the air flow above the complex terrain.

For RA, the appraisal of immediate effects of ague exposure requires on-site informations for a short clip period. These informations sets must incorporate information about emitted substances ( type and concentration ) every bit good as real-time local meteorological informations, which along with terrain informations can be used in a rapid environmental and risk appraisal, which is a valuable tool for on-site exigency planning in instance of accidental or deliberated releases of toxic substances in the ambiance ( Torok et al. , 2011a ) .

In the field of hazard analysis and hazard appraisal there are differences of sentiment sing the usage of qualitative or quantitative hazard analysis methods. The qualitative-quantitative factor is the basic belongings of jeopardies analyses methods. Most of the analysis methods are developed in order to place jeopardies and to find the hazard of that jeopardy turning into an accident.

For finding the accident hazard of the identified jeopardy, a methodological analysis for the word picture of chance and magnitude parametric quantities must be used. There were developed both qualitative and quantitative methods, which are successfully used, each methods holding its specific advantages and disadvantages ( Torok et al. , 2011a ) .

Qualitative methods used in jeopardy analysis

A qualitative analysis implies the usage of qualitative standards, utilizing different classs for parametric quantities separation, with qualitative definition which set up the graduated table for each class. Besides, qualitative determinations are made, based on the field experience, in order to delegate elements into classs. This attack is subjective, but it allows a higher generalisation grade, being less restrictive.

2.5.1.1 Designation of jeopardies

The designation of technological jeopardies is the basic measure in hazard appraisal procedure. Hazards appear in the industry all the clip, due to the procedure and runing conditions of the installings and the physical, chemical and toxicological belongingss of the substances used in these procedures. This is why it is extremely of import to place the substances ‘ risky belongingss and the operating conditions that put at hazard these procedures, the series of events that may take to the materialisation of a jeopardy.

In order to develop an in-depth survey of jeopardies and hazard analysis, the risky belongingss of the substances must be identified and assessed in order to find conditions or non they pose a jeopardy to human life, the environment of the technological procedure.

From a qualitative point of position this can be achieved utilizing checklists. A comprehensive checklist used in the appraisal of jeopardies and hazards posed by substances is presented in table 2.5:

Table 2.5 – Hazardous belongingss of substances- Checklist ( Hyatt, 2003 )

Type

Property

General belongingss

Molecular construction

Freezing point

Melting point

Vapour force per unit area

Boiling temperature

Critical force per unit area

Critical temperature

Critical volume

Density

Specific heat

Viscosity

Thermal conduction

Fluid denseness

Latent vaporisation heat

Dielectric invariable

Electric conduction

Flammability

Explosion/ Flammability bounds

Explosion threshold

Auto ignition temperature

Minimal ignition energy

Overheating

Corrosion

Corrosive for building stuffs

Incompatibility with other stuffs

Polymerization

Decomposition

Features of polymerisation

Features of decomposition

Features of hydrolysis

Impurities

Impurities in equipment stuffs

Impurities in substance

Chemical reactions, detonations

Heat of formation

Heat of decomposition

Combustion heat

Thermal stableness

Resistance to impact

Potential energy jeopardies

Toxicity

Exposure bounds: IDLH ; ERPG1-2-3 ; AEGL 1-2-3 ; LC50 and LD50

Exposure effects ( inspiration, consumption, tegument and oculus contact )

Effectss of long-run exposure with little sums

Warning bounds ( odor threshold )

Radiation

Radiation bounds

I± , I? , I? atoms

Material toxicity

It must be stated that stuff toxicity depends on a series of physical and chemical factors, in the type of contact and on the interaction of substances with beings. The ways in which this penetrates the organic structure are assorted, viz. unwritten ( through the oral cavity, in the tummy ) , cuticular ( toxicity enters the tegument ) or by agencies of inspiration ( through the respiratory system ) .

The harmful belongingss of risky substances can be divided into the undermentioned classs ( Ozunu and Anghel, 2007 ) :

acute toxicity ( really toxic, toxic, harmful, annoying )

specific belongingss ( allergic, carcinogenic, with consequence on reproduction or familial consequence )

with harmful impact on the environment

Whereas the first two classs mentioned supra have direct inauspicious consequence on wellness, the last one acts indirectly on human existences by damaging the environment.

The harmful actions start when little sums of substances appear in the organic structure ; should larger sums appear, they can take to one ‘s decease. The most normally used indexs to find substance toxicity are ( Torok et al. , 2011c ) :

medium deadly dose- LD50 is the dosage at which half of the experimental population of animate beings ( or worlds, should human deceases be registered ) dice. LD50 index at consumption and at the skin degree is shown in milligram ( mgs ) of substance per kg of animate being organic structure, taking into history a individual disposal.

the medium deadly concentration – LC50: concentration for inspiration is measured in mgs of substance per litre of air breathed or in volumetric parts per million -ppm ( exposure clip differs depending on substance toxicity )

the immediate unsafe concentration for life and wellness – IDLH is inspiration with irreversible effects on wellness

These bounds of concentration are used as indexs in both the US and the EU statute law ( NIOSH, 2012 ) .

The bounds of toxicity for a series of substances are set in the Dangerous Substances Directive 67/548/ EEC. They are grouped harmonizing to some classs presented below. Each type of danger has a hazard phrase ( Rphrase ) consisting of a figure and of the appropriate hazard description ( Ozunu and Anghel, 2007 ; Directive 67/548/ EEC ) .

Table 2.6 – LD50 ( unwritten )

Class

LD50

( mg/kg )

Symbol

Rphrase

Very toxic

& lt ; 25

T+

R26, R27, R28

Toxic

25 – 200

Thymine

R23, R24, R25

Harmful

200 – 2000

Xn

R20, R21, R25

The current thesis focal points on two major jeopardies, natural 1s, with a instance survey on volcanic ash, and anthropogenetic 1s, with instance surveies on S dioxide ( SO2 ) .

Sing volcanic ash, the most serious jeopardies can be associated with its:

caustic belongingss on stuffs, i.e. aircraft engines, windscreens, etc. ,

runing point, the volcanic ash runing inside the turbine due to the high temperatures, and so solidifies in the ice chest parts of the engine s.

denseness, the denseness of volcanic ash is comparatively high, dry ash being up to 5 times, wet ash about 20 times denser than snow. This fact represents a major jeopardy to edifices when ash accumulates on the roofs in sufficient measures, taking to prostrations.

In the instance of SO2, the major jeopardies are associated with:

Quantitative methods used in hazard appraisal

Quantitative analysis implies the usage of numerical or quantitative informations and provides quantitative consequences. This attack is more nonsubjective and more precise. It must be mentioned that the quantitative consequences can be extremely affected by the preciseness and cogency of the input parametric quantities. Therefore, the quantitative consequences within the hazard analyses should non be taken into consideration as exact Numberss, but as estimations, with a variable graduated table depending on informations quality ( Torok, 2010 ) .

2.4.2.1. Modeling

The representation of world through mold is extremely relevant, since it offers one the possibility to analyze and analyze systems in footings of mathematics and technology. It must be mentioned that a system consists of a set of elements that interact with one another within some bounds. Furthermore, this system has a specific behavior. These bounds are really the 1s that separate the system from the other 1s. These theoretical accounts can be divided into two classs, viz. physical and abstract ( fanciful or mathematical ) theoretical accounts.

With respect to the physical theoretical accounts, they describe the system from a physical point of position, utilizing the physical Torahs that apply upon the system under treatment.

The mathematical theoretical account of a system describes it in footings of mathematical equations, utilizing simplifying hypotheses.

Abstractization works in both ways, i.e. from object to its representation ( theoretical account ) and so back to world. Still, it must be stated that this theoretical account does non picture world all the clip ; it tries to be as closer to it as possible. The more complex a system is, the more complicated the theoretical account becomes. In this context, the purpose of patterning systems and processes utilizing the computing machine is to make a theoretical account that contains a description realistic plenty for the given application.

The basic stairss for the accomplishment of a mathematical theoretical account are as follows ( Savii and Savii, 2000 ) :

job designation and the pick of variables

building of mathematical dealingss among variables utilizing simplifying premises

the purchase of information sing the size, importance and interrelatednesss for each variable under treatment

the choice of input signals ‘ parametric quantities

constitution of province variables

proof of premises and dealingss

utilizing the right theoretical account harmonizing to the state of affairs.

2.4.2.2. Simulation

With the development of information engineering and computation equipment, the scrutiny of theoretical accounts utilizing simulations has become possible. Simulation allows proving those systems ‘ functionality theoretical accounts that have yet to be or are presently in design stage. Simulation is the lone possibility of analyzing the dynamic behavior of such a theoretical account. Discrete simulation, utilizing theoretical accounts of distinct systems, is of great aid for projecting production systems, where issues of optimisation appear ( Savii and Savii, 2000 ) .

In the present thesis we focus chiefly on the mathematical mold of the gas pollutants ‘ scattering in the ambiance.

Beginning theoretical accounts are used to specify the quantitative emanation scenario of substances by gauging their flow rate, the scattering of substance after release. Dispersion theoretical accounts turn the end products from beginning theoretical accounts into isoconcentration curves specifying concentration countries and cipher the development of concentration in clip.

The mass conveyance of molecular-scale fluid occurs through diffusion, with a changeless diffusion velocity throughout its motion. However, unstable scattering is a procedure different from molecular diffusion, since the mass conveyance occurs at assorted scale lengths of the disruptive motion. Disruptive scattering is much more efficient than molecular diffusion. The scattering rate is non changeless ; it depends on the size of the whirl and of that of the cloud of spread pollutant. These whirls can be of different sizes ; on a big graduated table, they determine the motion of the pollutant cloud, whereas on a little graduated table they contribute to its dilution. The energy and size of these whirls determine gas plumes scattering. Their continuance, length and strength are the chief factors that influence this procedure.

The mathematical mold of gas pollutants in the ambiance is based on equations of mass, energy and impulse preservation. Such an equation must be established for each pollutant. It represents the fluctuation of atoms ‘ denseness in clip and infinite. From these equations one can acquire a complex system of equations that can be solved by agencies of numerical methods, obtaining the existent behavior of concentration in clip and infinite.

A literature reappraisal reveals two chief methods used for picturing the behavior of pollutants released into the ambiance, viz. the Eulerian formalism and the Lagrangian 1. Both methods are used to depict the statistical belongingss of pollutant concentration.

The Eulerian formalism starts from ciphering fluid speeds in the ten, Y and omega waies, measured in fixed points in the fluid under treatment. Input information is comparatively easy to obtain from the measuring or mold of discharges, but work outing the mathematical equations system can be really complex, ensuing in inaccurate solutions. Dispersion coefficients can be retrieved utilizing the Pasquill-Gifford graduated table ( Pasquill, 1961 ) . After this, the imission map for a beginning point and meteoric scenario can be developed.

The Lagrangian formalism uses the statistical belongingss of some fluid atoms that move passively, freely. As compared to the Eulerian formalism, the mathematical equations system is easier to work out, therefore it is computationally really efficient, and merely the fraction of the sphere really involved in the scattering is simulated. Disruptive procedures are included in the theoretical account in a more natural manner, and there is no important numerical diffusion ( Stohl et al. , 2005 ) .

Still, the method ‘s pertinence is limited by the troubles encountered when finding the statistics of fluid atoms. The Lagrangian formalism is applicable upon long-distance scatterings, when the complex topography influences the flow of air-pollutant multitudes.

Although the scattering procedure is a typically Lagrangian one, about all information available refering the ambiance are based on Eulerian measurings. Therefore, a relation between the Eulerian belongingss and the Lagrangian 1s is ( widely ) accepted ( Sandu et al. , 2004 ) .