THE RULES OF THE ECOSYSTEM
The environment is a system of physical-chemical-biological-cultural processes
that interactive in space and in time, to which the survival of every being is tied.
The environment, characterised by a structure, an operation and a temporal
circumstance, can be studied at the level of individuals, population, community,
ecosystem…up to superior organisations such as BIOMI and Biosphere. The
ecology studies the structure and the operation of nature and, while the levels of
biologic organisation differ for structure, the biologic processes are very similar.
The ecosystem is defined by component and factors: sometimes the former play
the role of the rather in fact BIOCENOSE (constituted by all the living beings) and
physical-chemical BIOTYPE (features of the air, water and ground) are the
COMPONENTS/FACTORS of the ecosystem. The factors are divided in:
physiographical factors (geographical, topographical, geomorphologic position);
physical factors (climate, dynamics of the atmosphere, physical characters of
water);
- chemical factors(composition and concentration of the substances in the
air…);
- biological factors (relationship within single specie and between different
species).
The main parameters defining the conditions of development of the ecological
system are: light(defined as radiant energy) temperature, atmospheric gases, the
contents of the nourishing substances, structure of the ground, presence of living
beings…
Every factor influences the other and all is articulated by the time. Thanks to its
structure it is possible to understand the variability of an environment, as the
ecosystem is originated by the interactions of all its components and
factors(human communities too live in symbiosis with the nature adapting
themselves, to survive, to the possible changes).
Therefore we can sum up the rules and the principles are follows:
- every thing has a use(dependence between living beings, concept of multiple
use);
- the components of a system are tightly connected and there are some limits
that condition their life;
- space, resources, growth are independent from each other and for a
population there are conditions of development, beyond which, however, their
relationship can collapse;
- the process that take place in the environment go towards stability(concept of
homeostasis);
- energy flows in the system and the matter circulates in it according to a close
and cyclical circuit;
- a system tends to change in time, that means the adaptation and evolution of
a population(concept of succession).
Important are the relationships between individual and environment as the living
beings that have an area Of Tolerance, must act within the maximum and
minimal limit of the factors of the ecosystem; the ability of ADAPTING(or absolute
value).
So it is defined a species with low value(with a small area of tolerance)used as
biological indicator and only the study of various living species allows the
analysis of their behaviour and their requirements(for example food and shelter).
-
Referring then, to the animal or vegetable populations, considered as a group of
organisms of the same kind that occupies a certain space in a certain moment
and that reacts to the environmental factors collectively, we know that their
structure is defined by the number of individuals and their operation is based on
two biological mechanisms (births and mortality) and two social ones(immigration
and emigration).We mustn't forget that the factors that regulate the diffusion and
density some are independent from this climatic variations or the action of the
man)others are dependent on them and therefore are divided into intraspecifics
(as the competition) and interspecifics (as the predation).It's evident, however,
that the essential search for nourishment makes more populations enter in
competition and the most efficient species prevents the other from surviving;
therefore the populations interact (among them), in the ecosystem, for the control
of the efficiency. The relationships between predators, consumers and
decomposers favour the circulation, accumulation, the transformation of the
matter and the flow of energy. Beginning from the reserves in the atmosphere,
hydrosphere, lithosphere the elements and the chemical compounds enter in
circulation, absorbed, recycled and then expelled by the living beings according to
specified biogeochemical cycles. This interchange is continuous and it occurs
within the various levels of the food chain; the cycles have their own mechanisms
to control and regulation(homeostasis)that they tend to prevent possible
alternations of disturb of the balance of the system. This process is defined
NEGATIVE FEEDBACK and it is a system of self regulation whose missed working
limits the quality of the system. Yet the working of the cycles of oxygen, water,
carbon dioxide is very fragile and a wrong management by man can bring about
a modification of the biosphere. Therefore man must maintain them efficient to
avoid their wiping out the effects of the disturbance. The individuals adapt
themselves to the environment and all together they continually influences the
evolution of population modifying the territory. An ecosystem modifies its aspect
in time(PERIODISM, example the seasons)and in the space(DINAMISM)in other
words the biocenose varies. The evolution of the species takes the name of
Ecological Succession, and is checked specie by community, without external
interferences, for this reason we can say that it self-evolve. The variations of
environmental conditions favour the settlement of a species and the
disappearance of others. The species have an elevated reproductive ability, even if
the species with smaller biotic potential but with great competitive ability are
favoured. Communities are able to check the possible perturbations, but
nevertheless external interferences can occur. The environments differ for
structure but the working process is similar: a city works like a wood, as both
need energy and they produce refuse although with different structures. The
refusae of the wood are secondary materials that enter into a ciclicity, while in the
city they follow a linearity that leads to their accumulation. The man has the
tendency to transform a net and a ciclicity into a linear process tending to
simplify the ecosystem(reducing stability, destroying diversity) to benefit his
economic differences. To avoid this it is necessary to consider some fundamental
points:
- nature is important for the defence of the ground from the erosion;
- the vegetation favours the atmospheric exchange;
- the living beings are indicators of environmental conditions;
- every biological component develops a role that has a repercussion on the
man himself .
The nature and the man identify with the environment and the breaking off of
this system of relationships happens when the living beings don't perceive such
relationship and therefore move away from it.
WHAT AIR DO WE BREATHE?
There is not any doubt that among all the environmental problems the air
pollution, besides being one of the most important, is one of those about which
people care more and ask for curing interventions.
The increasing awareness of the problems connected with air pollution derives
from the real concern involving most of the population. Just think about people
living in great urban centres or near huge industrial settlements. There are also
problems on a national and international scale, like acid rains, greenhouse effect
and the thinning of the stratospheric ozone layer that are a source of concern
because of the severe and diffuse damages that constitute an impending menace
for the whole mankind.
On a local level the problems to be faced are:
- urban pollution, caused by vehicular traffic, house heating and, in many
cases, industrial and energetic plants.
- polluting substances produced, both routine and accidentally, by industrial
plants;
- indoor pollution.
On a national and international level:
- the sour deposition caused by long-distance transports and of chemical
transformation of nitrogen and sulphur oxides, emitted by the high chimneys
of industries and thermoelectric plants;
- CO2 and other greenhouse effect (increase of hearth's surface temperature)
generator gases, among which we can mention clorofluorocarburis, nitrous
oxide, ozone and methane;
- the accumulation of dusts in the atmosphere, that can have some implications
on the climate of our planet too.
- emissions of clorofluorocarburis (substances used as propellant in spray
bottles and as coolers and solvents, but also in plastic foams and in the
extinguishers) are responsible for the destruction of stratospheric ozone,
besides having the above mentioned effects.
There is no doubt that the solution to all these problems requires the planning of
suitable strategies that involve different spatial systems.
By atmospheric pollution we mean every single modification of the normal
composition of the physical state of the atmospheric air caused by the presence of
one or more substances that, because of their quantity or characteristics can:
- affect the normal environment conditions and the healthiness of the air;
- constitute a danger for man’s health;
- compromise leisure activities and other rightful uses of the environment;
- alterate biological resources and both public and private material good.
By analysing a champion of pure air in dry state that is without aqueous steam
and without mixture of other elements we’ve found the following gases:
- nitrogen:78,8%;
- oxigen:20,95%;
- argon:0,93%;
- carbonic anidride:0,03%;
- noble gas:0,01%.
There are also aqueous steam and atmospheric dust.
The champion of air, going through the process of human respiration changes its
composition as follows:
- the nitrogen remains unchanged (78%);
- the oxygen decreases, passing from 21% to 16%;
- the carbonic anhydride increases; passing from 0,03% to 5%;
- the content of aqueous vapour is considerably higher.
The air pollutants can include every substance that can be dispersed in the
atmosphere to take part in diffusion and transport processes, of transformation
and of the ground deposition. It is very rare that a situation of air deterioration is
determined by only one pollutant: a number of substances usually are usually
involved in different physical and chemical forms.
Certainly a few polluting agents remain unchanged once released in the
atmosphere. Thermal and photochemical reaction, sometimes made easier by the
presence of gases or solid or liquid surfaces, cause a continuos change in the
global system and in his constituents.
It is important to understand that there isn’t just one air pollution problem, on
the contrary, there are several problems interacting with one another.
At the origin of the various forms of atmospheric pollution there are the emissions
of gaseous substances, both volatile and particles, let in the atmosphere by the
chimneys of the industrial and civil plants and by the exhaust pipes of the means
of transport, and the emission deriving from the reservoirs, valves, pumps,
compressors and other components of machine plants.
The production and the use of fuels, the chemical and metalworkers industrial
processes, the extraction of minerals, the waste incineration and agricultural
activity cause the emission of polluting substances in a quantity which depends
on the adopted technologies .
The five great categories of pollutants are:
- sulphur oxides (above all sulphur dioxide);
- nitrogen oxides (nitrogen dioxide and monoxide);
- carbon monoxide;
- hydrocarbons;
- organic compound chlorinated and fluorinated, acid and alkali.
The emission of atmospheric pollutants can be either of anthropic or natural
origin.
The entity of the emission of pollutants of anthropic origin depends on the
geographic location.
On a planetary level, the emissions of sulphur dioxide of anthropic origin are
clearly higher than those of natural origin.
These prevail when there are compound as nitrogen oxide, carbon monoxide and,
above all, of the hydrocarbons.
The problem of the air pollution began with the appearance of man on earth.
Man started to use fire and fuels like wood for his elementary activities so
provoking the emission of combustion gases in the atmosphere.
The demographic growth, the advent of industrial activities, the use of motor
vehicles considerably increased the outlet of gas in the atmosphere, and, in the
end, its pollution.
During the respiration the atmospheric pollutants go through our lung tissues
and enter the blood circulation reaching all the parts of our body.
The numerous effects of the pollution are:
- ACID RAINS
- GREENHOUSE EFFECT;
- OZONE HOLE.
THE SOUR RAINS
Gases coming from the use of fossil combustibles by industries, thermoelectric
plants, heating plants and motorised vehicles polluting emissions contain, among
the other pollutants, SO2, that reacts first with oxygen:
2SO2+O2
2SO3
and then with the air:
SO3+H2O
H2SO3
forming sulphuric acid.
Such phenomenon, besides from sulphuric sour is also caused from nitric acid
formed by the combination of nitrogen oxides, emitted from unloading gases of
motorcars with water.
Falling, sour rains make the water of rivers and lakes so sour that doesn't allow
every form of life. They cause serious damage to forests, monuments, buildings
and they corrode the metallic structures of the constructions.
THE GREENHOUSE EFFECT
The enormous quantity of CO2 introduced into the atmosphere from man
activities cause another serious effect on the environment: the greenhouse effect.
Earth heated by solar rays would disperse its heat if not surrounded by a gaseous
atmosphere constituted mainly by oxygen, nitrogen and dioxide of carbon.
This last one has a great insulating power, and because of this an excessive
presence of CO2 inhibits too much the heat dispersion, causing a global increase
of the Earth's temperature . The emissions of CO2 in the air grow with civil and
technological progress: it is foreseen that in 2020 the quantities of CO2 emitted in
the atmosphere will be nearly doubled.
THE HOLE OF THE OZONE
In these last years a new environmental problem has risen, besides from those
already existing: the hole of the ozone. The greatest part of gases used as
propellant for sprays is constituted from h fluoreclorites hydrocarbons. It
concerns very stable mixtures that can’t react with any other substance, so they
go in various zones of the atmosphere where there’s a band of ozone that winds
earth for a thickness of around 5 kms at the distance of 30 km from the surface.
These gases are able to react with ozone causing its destruction that is revealed
like a kind of hole. Through this hole UV rays that come from the sun can easily
reach the Earth’s surface causing cancer of the skin, the weakening of the
immunity system and serious damages to the fish fauna.
In a city like, for example, Voghera has been shown that the
origin of the pollutants is above all of character autovehicolar:
- CO emitted by engines and from vehicles in a queue;
- SO2 that comes above all from diesel engines and from the gasoline used for
heating;
- hydrocarbons resulting from an incomplete combustion;
- NO emitted from engines at elevated temperature;
- NO3 that comes from the oxidation of NO in the air;
- O3 produced from the photochemical reactions that happen in the atmosphere
in presence of NO,NO2 and solar energy.
THE TOXIC EFFECTS OF THE MAIN POLLUTING
Sulphur Dioxide
The sulphurous anidride causes harmful effects at level of the pulmonary
apparatus. The conversion of sulphurous anidride in sulphuric acid can be
started from soot and from traces of metal.
Carbon monoxide
The toxicity of carbon oxide is due to its ability to link itself to haemoglobin,
taking oxygen place, transforming it in carboxidhaemoglobine.
Suspended total particulate
Elevated concentrations of suspended total particulate (superior to 1 mg/ms)
can be extremely harmful for the respiratory apparatus.
Benzene
In big doses the benzene can bring to the leukaemia.
Nitrogen dioxide
The nitrogen dioxide is an irritant of the respiratory apparatus and it
causes effects similar to those of the ozone.
Ozone
The ozone, present in higher concentration in the polluted atmosphere is
an irritant of the bellows.
LIMIT OF LAW
For the guardianship of public health and the environment a threshold of
attention have been established, beyond which the concentration of pollutants
becomes worrisome and a threshold of alarm beyond which they intervenes to
bring the values to normality. The monitoring is done through fixed
nets that work automatically.
Catalytic Combustors
The combustion is the only primary source of energy that until now has been
used by the man for the lighting of steam machines.
The employment of fossil fuels causes heavy damages to both human health
and the environment.
In order to control the hydrocarbon emissions, the first responsible of greenhouse
effect, a catalyst has been set.
Some catalysts, that facilitate the oxidation at low temperatures, are inserted
inside the combustor: this process, thanks to the thermic recombination of
nitrogen and oxygen, allows to avoid the formation of NOx
Among the innovative systems studied to decrease the emission of toxic gases
during the combustion, we take into consideration those composed by modified
alluminate (such as barium esalluminates) that succeed in transforming the
metallic ions in structures.
While CO2 is a primary product of combustion, NOx and SOx are secondary
products. Even if their emission is very low if compared to that of CO2, they are
very harmful. The emissions of CO2 NOx SOx depend mainly on the sources of
production. If this emissions increased , the number of circulating vehicles
should be limited . Since these gases enormously pollute the environment,
precise and deepened studies have been done.
CO2 emissions can be limited using vegetal fuels and increasing the output of
the transformations that lead to the production of energy.
-the Sox emissions can be reduced lowering the quantity of sulphur in the
mixtures, using natural gas or methods to the reduce of sulphur quantity.
-the Nox can be reduced through primary catalytic methods, such as for example
the catalytic pots and the “scr” , that is the “selective catalytic reduction”.
There are three principal methods that lead to the formation of Nox:
-the “thermal Nox”: method that requires very high temperatures , arriving up to
2000 °K.
-the “prompt Nox”: mechanism that happens for interaction between nitrogen and
CHs radicals and requires temperatures of 1600 °K.
-the “fuel Nox”: formation due to the presence of organic nitrogen into the fuel
and depends essentially on the relationship air/fuel and on the temperature.
Finally, in the case of “clean fuels”(natural gases and oils containing low
percentiles of nitrogen mixtures) the formation of Nox can be obtained by two
methods :
-reducing the temperature of combustion
-reducing the concentration of oxygen in the zones where the temperature is
maximum.
Such requisites are realised through the introduction of inactive gases ( N2 , H2 )
in the combustion chamber , by the employing of premiscelate-flames burners
to decrease the temperature or by the stage-combustion . This type of
combustion has a first stage of oxidation at high temperatures, with relative
formation of Nox , which is followed by a lowering stage , in which, by a flow of
fuel, the nitrogen oxides are transformed into N2.There is, finally, a third
necessary post-combustion stage eliminate CO and the remaining fuel from the
second section. In the combustors for whirlwind, the premixed-flame burners
constitute the most efficient method.
The premixed-flame burners mix the air with the fuel on the top of the
combustion chamber , where is possible to maintain a uniform temperature and
relatively low. For the primary methods it was seen that the demands of reduction
of Nox and of incombusted fuel are in contrast , because the elimination of the
nitrogen oxides pushes to a lowering of the times of residence in the combustion
chamber and the temperature of the flame up to levels in which the formation of
CO results favoured.
Catalytic combustion
The catalytic combustion represents a valid tool for energy production from
whirlwind fed by gas. The advantages added to the traditional combustion consist
in:
-lowering of combustion temperature , that limits the emissions of Nox allowing
the almost complete elimination of CO and UHC.
-use of great-thermal-stability materials , that can guarantee the maximum
efficiency in every stage of the combustion.
-possibility to associate homogeneous and heterogeneous combustion reactions.
There are three typologies of catalytic systems. The three models share the use of
catalysts that consist in a series of segments with honey-combed-sections (about
200 cells of 3 x 20 mm per segment ) composed by cordierite supports on which
are pellicles (called washcoats) of palladium, alumina and zirconium. It is
possible to find segments composed by reduced exalluminates of manganese in
some catalysts , denser
than the previous. The catalytic function is developed by the palladium, a little
volatile element and therefore proper to operate at high temperatures. Especially
in the combustion of the methane, the palladium oxidises thanks to the action of
alumina and
zirconium: when the temperature is lowered to 800°C, the
palladium oxide decomposes in palladium and oxygen. This reversing procedure
is important ,
because it is able to control the combustion temperature , that keeps on low
levels limiting in such way the production of Nox.
These are the three possible configurations of catalytic combustion systems :
-the mixture air/fuel is channelled in the catalyst where it is completely burned
at low temperatures. This combustion system is the less efficient.
-only a part of mixture, composed by fuel and by a small percentage of air, is
introduced in the catalyst and here is heated to temperatures under 1000°C. The
rest of the mixture, composed mostly from residual air , is channelled in a
traditional combustion chamber , where it is homogeneously burnt. The
emissions of Nox are reduced to less than 5 ppm and those of CO and UHC
under the 9 ppm.
-all the mixture is introduced in a combustor , projected to allow a combustion
at low temperature inside , with great catalytic activity and outside a strong
heating of the gas that exits. The residual incombusts of the mixture are,
subsequently, burnt in a traditional combustion chamber. The above mentioned
system is the best among the catalysts : it allows a good reduction of the
emissions of NOx under the 3 ppm, of CO under the 2 ppm and of UHC under the
0,1 ppm.
STUDY OF
DIOXIDE
THE
DISTIBUTION
OF
NITROGEN
The objective we want to reach is to work out a study on the quality of the air
using passive samplers whose working is based on the principle of the molecular
diffusion. The choice of different stations for the survey of NO2 has enabled to
draw useful information as regards the knowledge of the concentration of
pollution, so underlining so high-risk areas.
DESCRIPTION OF THE METHOD
MATERIAL: acrylic pipes that have precise dimensions (length 7 cms, inside
diameter 1 cm) form the samplers. In every pipe, closed at the end by a polietilene
blue cork, two stainless steel round grates soaked of triethanolamine (substance
that absorbs NO2 effectively) have been inserted; the other end of the pipe has
been closed with a transparent cork easily removable.
POSITIONING OF THE SAMPLERS
The samplers prepared as described above have been set vertically on wooden
supports and placed in six stations on trees at an height of around 2.5 metres.
The transparent cork is removed in the low part of the sampler to allow the
circulation of the air and therefore the absorption of the NO2 inside it.
In the first station an impregnate white sampler has also been exposed but left
closed because it constitutes a parameter of reference.
At the end of the period of survey (a week) the pipes have been closed and taken
for the clorimetric analysis.
ANALYSIS
The used reagent is the liquid of Griess (solution sulfurylamide-orthophosphoric).
This has been introduced into the sampler in very little quantities (3 mls).
After having closed the pipe again this is left to rest for 30 minutes to allow the
formation of one salt of diazonium and to be able to determine therefore the
following formation of an azoic colouring agent.
Then an analysis by visual comparison has been carried out.
LIST OF THE STATIONS FOR THE SURVEY OF NO2
1)Gallini school
2)Viale Repubblica (at the junction with via Giotto)
3)Galilei school
4)Viale Repubblica (at the junction with via Zanardi)
5)Via Verdi
CHROMATIC SCALE
-White
colour
-Light pink colour
-Dark pink colour
-Fuchsia colour
Air quality: GOOD
Air quality: MEDIUM
Air quality: BAD
Air quality: VERY BAD
The observation of the colours assumed by the solutions contained in the
samplers of survey as brought to the conclusion that exist a middle-rate of
pollution due to NO2 in the selected stations.
However we must underline a slightly lower level of pollution near the Gallini
school.
We must specify that to have a correct valuation on the purity conditions of the
air it is necessary to effect analysis in the laboratory by means of colormeter (a
special instrument to measure the colour) that can furnish therefore exact
numerical values of concentration of the pollutants.
TEST ON SPOROBOLOMYCES ROSEUS
The experiment allows to notice the concentration of SO2 and other present
contaminants in the atmosphere.
The Sporobolomyces Roseus is a yeast particularly sensitive to the present
polluting load in the air. This yeast is normally present and alive like saprophyte
on the leaves of varied kinds of grassy or woody plants to short-lived or perennial
leaf. We have also chosen therefore to effect this search on dioicus urtica, plant
that introduce leaf vegetation during the whole year.
DESCRIPTION OF THE METHOD
Material: the ground of crop that we have used for the realisation of the
experiment has been prepared with sobauraud dextrose agar acidified with lactic
acid up to reach a level of ph equal to 4-4,5.
We have also used capsules petri monouso of the diameter of 9-10
cms and leaves of nettle.
Method: the leaves of nettle withdrawn in 5 stations have been carefully you glue
with the superior face to the cover of the petri capsule. The plates have been
incubated for 24 hours to temperature environment to make that the cells freed
on the ground the spores.
Spent the 24 hours the petri capsules have been turned in such way to position
the qagar aloft and you still leave in incubation for 72 hours to temperature
environment.
Reading: the reading has been effected after 4 days that it is the enough time to
have the colonies grown. For superior periods it is difficult to be able to
distinguish her the one from the other for their abundant presence have been
therefore you count the colonies colour pink cream for cmq.
Discussion: with this study we have individualised zones with different quality of
the air. Interior shot the urban entourage of the cities we have been always
noticed values of alteration raised; the peripheral zones show subordinates
instead to levels of pollution.