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Amount of Air Ions Depending on Indoor Plant Activity

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Literature sources and earlier researches state that plants may be able to produce a variety of air ions, including negative light ions. In this article, the regularity of influence of plants on the number of ions in the room is being proved, basing on a series of experiments performed with the following plants: Spathiphyllum, Scindapsus, Strobilanthes, Chlorophytum and Pinus mugo. It was concluded that plants, in general, are able to stabilize the indoor ion concentration and reduce its fluctuations. The plants help to increase the concentrations of negative ions and decrease the concentration of positive ones, however the optimal and “healthy” ion concentration was not reached. Plants without artificial illumination work more as ion reducers, not producers.
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Environment. Technology. Resources, Rezekne, Latvia
Proceedings of the 10th International Scientific and Practical Conference. Volume II, 267-273
ISSN 1691-5402
© Rezekne Higher Education Institution (Rēzeknes Augstskola), Rezekne 2015
DOI: http://dx.doi.org/10.17770/etr2015vol2.247
Amount of Air Ions Depending on Indoor
Plant Activity
Natālija Siņicina, Andris Skromulis, Andris Martinovs
Rezeknes Augstskola, Faculty of Engineering,
Address: Atbrivosanas aleja 76, Rezekne, LV-4601, Latvia
Abstract. Literature sources and earlier researches state that plants may be able to produce a variety of air ions,
including negative light ions. In this article, the regularity of influence of plants on the number of ions in the room is
being proved, basing on a series of experiments performed with the following plants: Spathiphyllum, Scindapsus,
Strobilanthes, Chlorophytum and Pinus mugo. It was concluded that plants, in general, are able to stabilize the indoor
ion concentration and reduce its fluctuations. The plants help to increase the concentrations of negative ions and
decrease the concentration of positive ones, however the optimal and “healthy” ion concentration was not reached.
Plants without artificial illumination work more as ion reducers, not producers.
Keywords: air ions, plants, microclimate.
I INTRODUCTION
Under normal circumstances (temperature 0°С,
pressure 760 mmHg), one cubic meter of air contains
2,5.1025molecules. They are in a constant thermal
motion, moving randomly and colliding continuously
with each other. Very soon, the light atomic or
molecular ion attracts conglomeration of molecules
and becomes intermediate ion with a much greater
mass and lower mobility [1]. When settling on micro-
particles, aerosols, dust, etc., these ions are converted
into heavy and super-heavy air ions having a large
mass and even smaller mobility. These are not ions
any more but rather charged aerosols whose
concentration depends entirely on the purity of the
ionized air [2].
Small air ions are constantly being produced in
nature by radioactive components of the soil, by
cosmic rays, by the shearing of water droplets, etc. In
clean air they can exist for several minutes, but their
numbers are depleted by air pollutants, by stray
electrical fields and by the mere presence of occupants
in a room. Almost always there is a fluctuating
equilibrium between ion formation and ion loss [3].
Under normal conditions there is a small difference
between the positive and negative ions on the ground
oor level in the atmosphere. Any disturbance of ion
balance has direct impact on living organisms [4].
The presence of negative air ions (NAI) in the
inhaled air is essential for normal functioning of
human and animal organisms [5]. Scientific research
indicates that the air within homes and other public or
office buildings can be more seriously polluted than
the outdoor air. Public concern about the effects of
indoor air pollution on health has resulted in expanded
research of the topic [6]. Some countries have already
elaborated legal framework for air ion concentration
in work rooms. On 16 June 2003, sanitary and
epidemiological rules and regulations “Hygienic
Requirements for the Air-Ion Level of Industrial and
Public Facilities SanPin 2.2.4 1294-03” [7]
(Санитарно-эпидемиологические правила и
нормативы "Гигиенические требования к
аэроионному составу воздуха производственных и
общественных помещений СанПин 2.2.4 1294-03")
entered into force in the Russian Federation.
According to these Requirements, optimal
concentration of light negative ions amounts to 3000 –
5000, while concentration of positive ions should be
half as much. However in most cases, the
concentration of favorable light, negative air ions
indoors does not exceed few dozens, while the
concentration of harmful positive ions is growing
rapidly, especially if there are people, TVs, computer
monitors and similar devices in the room [8].
Ions are particles of the air that have either positive
or negative electrical charge. In natural environment
they are usually produced to maintain a healthy ratio,
but in articial environment of air conditioning,
electrical equipment, uorescent lighting and even
synthetic clothing the balance can be seriously
affected [9]. NAI concentration decreases
considerably or even falls to zero in the polluted air of
cities, in closed and air-conditioned rooms, near
operating household and ofce equipment. The
absence of NAI in the air may cause health disorders,
whereas inhaling the NAI-enriched air improves
health and human comfort [10]. Besides, practical
field testing reveals that the somnolence, apathy,
Natālija Siņicina, et al./ Environment. Technology. Resources, (2015), Volume II, 267-273
268
headaches, etc. ascribed to the "dead" air in enclosed
spaces can be conquered effectively by supplying
moderate concentrations of negative ions [3]. Air ions
may be healing or may harmfully affect human health.
This effect depends on ion concentration in the air and
on proportions of positive and negative ions. These
proportions are characterized by unipolarity
coefficient
n
Kn
, (1)
where n+ and n- mean concentration of positive and
negative cluster ions.
Interaction of air ions and plants may be expressed
in various ways, and nowadays this topic is being
studied. Artificially controlled environment of air ions
in greenhouses is experimentally used to harvest more
vegetables [11] because ionized air particles
contribute to a faster exchange of substances in plants
[12]. However, numerous cases show that air ions in
combination with strong anthropogenic atmospheric
pollution can also enhance negative effects on plants.
Air ions of different classes, products of radon gas
decay and charged aerosol particles which are spread
in the atmosphere are considered to be factors causing
damages of tree foliage and trunk [13].
Plants are reported to be able to produce various
air ions, including NAI, under normal conditions [14].
Most plants emit different types of volatile organic
compounds (Bio VOCs) and even micro-amount of
Bio VOCs has a great impact on formation processes
of cluster ions [15]. This effect is reinforced when
volatile compounds are emitted from the plant in ionic
form, e.g., Bio VOCs emitted from the needles of
conifers are ionized because of charges accumulated
in the sharp tips of the needles. Ions of volatile
compounds are very good condensation nuclei in the
atmosphere that contribute to further formation of mist
and clouds. Thus, coniferous forests can even affect
the global climate [16]. To a certain extent, most of
the plants are air ion generators. Intensity of such
generation depends on the daily intensity cycle of
metabolic process in these plants [17].
Indoor plants improve quality of the air. Some
plants effectively clean the air from organic
contaminants [18], while other plants reduce the
amount of micro-organisms in the air because of
phytoncide effect. Plants produce oxygen and absorb
carbon dioxide [19,20]. Many plants humidify
intensely the air of the room. As elements of phyto-
design, houseplants have a positive impact on the
psycho-emotional state of the occupants. As a
consequence of people staying indoors, the indoor air
is saturated with anthropogenic organic, microbial and
aerosol pollution to a greater extent than the natural
air. The indoor air contains less small oxygen ions
than the natural air [21].
Light-absorbing pigments in photo-organisms
capture photons of certain colors and reflect other
colors. The energy of a photon is transferred through a
long chain of molecules to the reaction center, which
splits water to produce high-energy electrons for
biochemical reactions. The process of photosynthesis
(especially the light phase) is directly related to
changes in the difference of potentials on the
thylakoid membranes of chloroplasts [22,23].
In chloroplasts, thioredoxin is restored by taking
electrons from the recovered molecules of ferredoxin.
The recovered thioredoxin is oxidized, giving, in its
turn, the electrons to the molecule of enzyme. Thus,
during the transition from darkness to light, when the
circuit of electron transportation begins in the
chloroplasts and the recovery of the molecules of
ferredoxin takes place, several enzymes are being
activated [18].
Productivity of the photosynthesis of plants is
determined by two major parameters: the total surface
of leaves (assimilative surface) and the intensity of
photosynthetic processes per unit of leaf surface [24].
To make normal growth of plants possible, the light is
needed. Almost all greenhouse use partial
supplementary lighting of plants with a help of lamps
[25].
As any process involving photochemical reactions,
photosynthesis is also characterized by the lowest
amount of light needed to begin the process. Starting
from this point, the dependence of photosynthesis on
the intensity of the light can be showed with a help of
logarithmic curve. Initially, increase of the light
intensity leads to a proportional growth of
photosynthesis (area of the maximum effect). Within
this level of lighting, the speed of photosynthesis is
limited by the light. With further raise of the light
intensity, photosynthesis continues to increase, but the
process is slower (area of weakened effect). Finally,
the light intensity increases, but photosynthesis
remains the same (area of light – plateau) (Fig.1) [26].
Fig. 1. Photophilic and shade tolerant plants light saturation (the
plateau)
Natālija Siņicina, et al./ Environment. Technology. Resources, (2015), Volume II, 267-273
269
II MATERIALS AND METHODS
We used the same plant species [26] and found
similar species-dependent differences in the ability to
generate NAI. The data presented in this paper prove
that the capacity of plants to generate NAI differs. The
aim of the experiments was to find the species with
the most expressed capability to generate NAI.
In order to perform this study, several plants were
selected which, by their nature and taking into account
the impact of external factors, can affect the air ion
concentration indoors. Therefore, plants with the
following characteristics were chosen: large area of
leaves, leaves with a pointed tip and hair shaft;
developed transpiration function (as a result of
transpiration a lot of water is vaporized from plants),
dust particle absorption, expressed phytoncide
features.
Fig. 2. Scheme of Measuring Devices and Groups of Indoor Plant.
Phyto-Module of Strobilanthes.
2.1. Five Plant Phyto-Module
Phyto-module of five plants (Fig.2) (a complex of
specially selected plants for environmental
improvements) was created basing on the following
five plants (Table 1.). The size of the phyto-module is
approximately 800x800x800 mm.
Air ion concentration was measured with the portable
bipolar air ion counter "Sapfir-3м". This device
provides simultaneous measuring of positive and
negative air ions with minimum resolution of 10 ions
per 1 cm3 . The device measures air ion concentration
in the air (mobility k 0.4 cm2V-1s-1). This mobility
interval is close to the class of cluster ions [27].
During the measurements, air ions, according to their
polarities, are channelized to positive or negative
aspiration collector in aspiration chamber and, after
coming into contact with this collector, the ions are
discharged. Afterwards, the charge is sent to
amplifiers and then the impulses are counted and
displayed. The device counts the charges of air ions,
therefore if an ion has more than one charge, it is
counted as several ions.
TABLE 1.
PLANTS VARIETIES
L
atin name
P
roperties [27]
R
equirements for
lightning Size,
H
/D,cm
Spathiphyllum Reduces the
amount of benzene
and
trichloroethylene,
high efficiency of
phytoncides
Bright, scattered
in spring 35/40
Scindapsus Reduces the
amount of benzene
and formaldehyde,
average efficiency
of phytoncides
Indirect, bright 40/50
Strobilanthes Reduces the
amount of
formaldehyde
average efficiency
of phytoncides
Indirect, bright 35/45
Chlorophytum Reduces the
amount of benzene
and formaldehyde,
high efficiency of
phytoncides
Indirect, bright 35/45
Pinus mugo Reduces the
amount of benzene
and formaldehyde,
high efficiency of
phytoncides
Indirect, bright 50/55
Indoor climate parameters were determined using
the multi-meter "Easy Sense Q". Systematic
measurement error of this device for temperature is ±
0.3 ° C, whereas error for relative humidity is ± 5%.
Error for lighting is not specified. The total amount of
radioactive α, β and γ radiation was measured in
μSv•h-1 with the portable device "Gamma-Scout" with
systematic measurement error less than 5%. For all
devices, the average value of each measurement point
was 10 minutes. Each time the measuring devices
were placed in a distance of approximately 40 cm
from the phyto-module, at a height of 120 cm from the
floor.
The measurements were carried out in automatic
mode for each photo-module individually. During the
first 48 hours, microclimate parameters of the room
were measured without any plants. Afterwards, phyto-
modules of each plant species were measured, the
measuring process was identical for each plant.
The experiment was taking place in a room of 12
m2 and 36m3. The room has one window towards East.
The room is located on the first floor, it is closed and
without forced ventilation. During the measurements,
people were present in the room only once a day to
switch on the devices, to turn on online mode for
measuring or to change phyto-modules.
Natālija Siņicina, et al./ Environment. Technology. Resources, (2015), Volume II, 267-273
270
When carrying out measurements in natural (non-
controlled) lightening, difference in light intensity was
a disturbing factor, because the experiment was
carried out within a period of several days (some of
them were sunny, while other days were cloudy),
therefore the level of lightening in the room changed.
As a result, it was decided to carry out an experiment
when micro-climate parameters were measured under
circumstances of controlled lightening.
2.2. Controlled Light
The experiment was carried out in the same room.
The window was closed with an opaque tissue not to
let the light in. The phyto -module was created of five
plant species used in the previous experiment as well.
The total number of plants: 30 items. The total surface
of the phyto-module amounted to 2 m2. Arrangement
of plants and devices remained the same (Fig.2).
Measuring of micro-climate parameters was carried
out using the same instruments: in the room with and
without plants for 24 hours without lighting (in the
dark), 24 hours with fixed lighting (1000 lx). During
this experiment, gas concentration in the air was not
measured. Meteorological data on ultraviolet radiation
provided by Rucava Station were also taken into
account [28]. The experiment was carried out
repeatedly.
2.3. Phyto-Module of Pinus Mugo
For the needs of the experiment, a phyto-module
was created of the coniferous plant Pinus mugo. The
experiment was carried out in the above mentioned
room without lighting (in the dark). The mode of
experiment remained the same.
III RESULTS AND DISCUSSION
After carrying out experiments with five plants, it
is not possible to select one particular species that
would be the best generator of negative ions. On the
first day of the experiment, the best results were
shown by Pinus Mugo, but later its capacity to
generate ions decreased. The overall conclusion is that
the capacity of plants to produce air ions is fluctuating
and requires a much longer study period than a few
days. Supposedly, air ion balance indoors is also
affected by other unintentional and uncontrolled
factors.
The experimental data (see Fig.3) show that the
number of positive air ions in the given rooms is
higher than the number of negative air ions: 20-29%
(without houseplants) and 23-68% (with houseplants).
Maximum / minimum concentration of positive air
ions: 159cm3/76 cm-3 (without houseplants) and
180cm3/30cm3 (with houseplants). Maximum /
minimum concentration of negative air ions:
110cm3/54 cm3 (without houseplants) and 115 cm-
3/33cm3 (with houseplants). These data reveal that,
basing on the air ion concentration and unipolarity
coefficient, the room used for the experiments is not
recommended for human health (if not ventilated).
The room has very low concentration of positive and
negative air ions and inadequate unipolarity
coefficient, because, basing on the SanPin 2.2.4 1294-
03, minimal admissible concentration of positive air
ions is 400 cm3, negative air ions 600 cm-3, admissible
values of unipolarity coefficient 0.4 < K < 1.0. During
the day, the room temperature increases and relative
humidity decreases because of the sunlight. The
measured average ambient temperature in the room
without plants is about 30C higher than in the room
with plants. The average humidity is up to 6% higher
in the room with plants than in the room without
plants. It means that plants increase the air humidity
(the water is evaporated through leaf pores).
3.1. Five Plant Phyto-Module
During the research of phyto-modules of five
plants, analysis of data provided by the air ion counter
showed that at night the total number of ions is 5 –
15% less than in the daytime.
A significant increase in negative ions was observed
during the study of the phyto-module of conifer Pinus
Mugo, i.e. Mountain pine. This increase amounted to
5% if compared to a room without plants and to 30%
if compared to the indexes obtained during the work
with other phyto-modules. Low concentrations of air
ions were recorded when working with the phyto-
module of Hlorofitum, although this plant is
considered to have a positive effect on the
environment and to reduce the air pollution. Decrease
in the number of air ions was observed on the second
day of the study in the presence of plants in the room.
A common trend - without controlled lighting,
plants stabilize fluctuations of air ion concentrations
in the room. They become predictable, depending on
the natural day lighting modes, besides the amplitude
of fluctuations is smaller.
At the same time, in a room without plants the total
number of ions is 15 – 20% less at night than during
the day. The total number of ions in an empty room
without plants is 30 – 35% more than in a room with
plants (Fig.3).
3.2. Controlled-light
The experiment showed that, regardless of whether
there is artificially created dimming or constant
artificial lighting, there is a tendency of reduction of
the number of air ions during the night and the
increase of their number in the daytime. In a room
with lighting and plants, the number of ions was 15%
higher than in a room with plants and without light.
(Fig.4.,5.)
Natālija Siņicina, et al./ Environment. Technology. Resources, (2015), Volume II, 267-273
271
a
Fig.4. Concentration of negative and positive ions in the air with plants in the room with and without lighting.
Fig.
5
Concentration of negative and positive ions in the
room
with
out
plants in the room with and without lighting.
a
b
a
b
Fi
g
.3. Concentration of ne
g
ative ions in the air with five
p
hoto-modules and in the room without
p
lants.
Natālija Siņicina, et al./ Environment. Technology. Resources, (2015), Volume II, 267-273
272
Thus, it can be concluded that the light needed for
photosynthesis raises the capacity of plants to generate
air ions. Without lighting, metabolic processes in
plants are slower and less active, so the plants serve as
air ion absorbers rather than producers because of the
large total surface of their foliage.
TABLE 2.
AVERAGE IONS CONCENTRATION
Conditions/
Parameters
In the dark
With
controlled
lighting
Without
plants
With
plants
Withou
t
plants
With
plants
N - 115 92 103 111
N + 155 136 134 131
N (total) 270 228 237 242
K 1.35 1.47 1.30 1.18
In a dark room with plants, not only the total air
ion concentration is significantly lower if compared to
an artificially lit room; the value of the unipolarity
coefficient K is also lower, which is almost in
distinguishable from the K value in a room without
plants. It means that if there is no light, plants in the
room are not useful because their impact on air ion
concentration is minimum.
Analyzing the results obtained at constant artificial
light, it can be concluded that the presence of plants in
a room increases the concentration of negative air ions
and slightly reduces the concentration of positive ions,
thus stabilising the K value closer to zero. However,
in our experiment this effect did not appear to be
sufficient to reach the amount of air ions favorable for
human health with a help of plants and to ensure the K
< 0, which would be recommended from the medical
point of view. (Table 2).
It should be noted that even in the room without
lighting and without plants, there were still daily
fluctuations of the air ion concentrations, which
apparently do not depend only on the sunlight and the
presence of plants, but it is caused by other air ion
producing and loss mechanisms. Constant artificial
lighting slightly reduced these fluctuations by
increasing the concentration of ions at night, and
slightly decreasing it during the day.
3.3. Phyto-Module of Pinus Mugo
Experiments with Pinus Mugo, as probably one of
the plant species that significantly affect the air ion
microclimate indoors, deserve a lot of attention in
further studies (Fig.7). Analyzing our first study in a
room with shielded windows, it can be concluded that
this plant species is great in dealing with the rapid and
often chaotic air ion fluctuations caused by various
factors. Pinus Mugo decreased fluctuations of air ion
concentrations to almost constant level that almost
does not depend on external factors. It only remains to
find an opportunity to stimulate metabolic processed
in these plants with the help of adequate lighting and
other techniques, in order to achieve the required level
of air ion concentration indoors (Fig.6).
IV CONCLU
IV CONCLUSION
Our experiments have revealed that plants can work
as ion generators only in controlled or uncontrolled
lighting due to increased photosynthesis and
metabolism. In the dark, plants are rather ion
absorbers due to the large surface of their leafs.
Presence of plants in the room can significantly
stabilize uncontrolled fluctuations of ion concentra-
tion, however the necessary level of ionization was
not reached. Conifers, e.g. Pinus Mugo, might be the
best ion producers, however further continuous
experiments are needed to identify the plant species
that would the best in ion production.
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