ATMOSPHERE IMPACT ON ACIDITY OF BARK SOME WOODY PLANTS
a
M. Ruščić, bM. Bralić, cD. Mirić and cI. Veletić
a
Facutly of Philosophy, University of Split, 21000 Split, Croatia
b
c
Faculty of Chemical Technology, University of Split, 21000 Split, Croatia
Students
Abstract
Fast technological and industrial development in the last two decades has caused
accumulation of harmful matters in the air, water and on soil which nowadays have negative
impact on climate and consequently on eco systems.
In this paper we have presented the results of determination of acidity and buffer
capacity in six plant species. Three plants belong to evergreen plants (Nerium oleander,
Viburnum tinus, Pyracantha coccinea) and other three to deciduous plants (Celtis australis,
Ficus carica, Sophora japonica).
Total of 240 samples has been analyzed during 2004 and 2005. Mean pH value of tree
bark from each locality varied from 5,13 to 6,32; while mean pH value of analyzed plants
from all localities ranged from 4,94 (Nerium oleander) to 5,96 (Sophora japonica). Statistical
analysis has shown significant difference among mean pH values (F=2,91; p=0,024).
Buffer capacity varied from 4,97 (Pyracantha coccinea) to 7,7 (Celtis australis), with
recorded significant difference among plants on all sites (F=7,96; p<0,001).
Key words: Environmental quality indicator, woody plants, pH value, buffer capacity
a
Coresponding author. Tel. ++385 21 386 122
E-mail address: mrus@ffst.hr
1
1. Introduction
Air pollution has negative impact on accumulation of toxic matter in the plant body
and provokes destruction of its protoplasm. Physiological consequences such as decreased
transpiration for 1-2 times, inhibition of photosynthesis, accelerated process of getting old and
low resistance, what especially in urban areas leads to the shorter plant life (Jablanović and
Rožaja 1980).
All chemical compounds or elements that are released into atmosphere as main result
of human activities and are harmful to living organisms are commonly called air pollutants
(Moriarty 1999). Majority of heavy metals, sulfuric oxides and nitrogen are included among
pollutants deriving from anthropogenic sources (Whelpdale et al.1998, Pacyna 2001).
Air quality can be recorded by measurements of pollutants directly from air by
implantation of models that illustrate spreading of pollution or by using bio-monitors
(Markert et al. 2003). Direct measurements give objective data about pollution level, while
bio-monitors give data about pollutant quantity and their impact on occurrence frequency and
the state of bio-monitors.
A good indicator of air pollutant accumulation must comply the following conditions
(Conti and Cecchetti 2001):
i)
pollutants from the air must be accumulated in the same way and in the same
quantity under different conditions,
ii)
pollutants must be easily measured; measurements must give data about level of
pollutant sedimentation
iii)
types of used organisms must be common and available for collecting in the same
area through a year,
iv)
in order to establish the state of eco-system in relation to studied pollutant,
researchers must be aware of state of the control eco-system (Seaward 1995).
Control level is usually taken as “natural” level at which the emissions have the least possible
impact (Conti and Cecchetti 2001). However, the control level differs according to plant
species. Pollutants may passively accumulate on the bark surface (as a part of water solution,
in gaseous state or tighten to particles) or it may be absorbed through process of ion exchange
in the outer parts of dead cork tissue (Walkenhorst et al.1993, Schulz et al. 1997). Ion
exchange is a quick physiological-chemical process during which cations and anions are
bonded to functional organic groups in cell wall (Tyler 1990, Brown and Brûmelis 1996).
Sulfur dioxide is accumulated in tree bark causing the changes in bark acidity and buffer
2
capacity. Majority of studies confirm significant correlation between bark pH and SO2
concentration in the atmosphere (Grodzińska 1971, Lötschert and Köhm 1973, Kienzl 1978),
showing that higher atmospheric concentration of sulfur dioxide is followed by increased
acidity of the bark. There is also established interdependence between pH and cation
concentration in the tree bark (Farmer, et al. 1991). If the bark pH is low, than the quantity of
exchangeable cations is also very low and vise versa. Besides different pollutants which affect
pH of the plants, there are also other important factors, such as type of plant, tree age, health
state of the plant, weather conditions, substrata and thickness of taken sample (Staxäng 1969,
Grodzińska 1982). Among all indicators taken into consideration, the pH value of tree bark
and buffer capacity are very good and reliable indicators of atmospheric pollution. The
highest concentrations are found in surface layers of outer bark, while the lowest
concentrations are found in the core of the tree (Schulz et al. 1997). According to Kosmus and
Grill (1986) in Graz (Austria) established that microclimate has also important impact on the
pollutant quantity and consequently on bark saturation with air pollutants. Since tree bark is
present even in the most densely populated areas, it is considered to be a very useful
biomonitor in urban zones. Bigger Croatian towns and their surroundings due to medium
population density have adequate biomonitors, while European cities in the middle Europe
lack such biomonitors.
In this paper are shown the results obtained from investigating of atmosphere impact
on acidity and buffer capacity of woody plants in wider area of the town Split (Croatia) as
continue of the earlier researches ( Bačić and Ruščić, 1994).
2. Materials and methods
2.1. Bark characteristics
According to expanded definition of the International Association of tree anatomist bark
is extremely complex, heterogeneous material, which includes all plant tissues that are on
outer side of cambium.
Formation of bark initiates with cell division of cambium, which forms ksilem on wooden
(inner) side and floem primary tissue of the bark, on the outer side (Schulz et al. 1999). Since
the quality of bark varies depending on wall composition of ritidome and thickness of outer
and inner layer of the bark. Usually, dead bark is included in bio-monitoring studies.
3
The bark of studied plants has the following characteristics (Pejčinović et al. 1977):
Sophora japonica L. – bark of the young plant is smooth, gray-green color, later becomes
brown, comes off in scales; Ficus carica L. – bark is smooth, ash-gray color, older plants peel
off in form of bigger plates; Viburnum tinus L. – bark of the young plant is smooth and has
reddish-brown thin bark, while older plants have thick gray color bark; Pyracantha coccinea
Röm. – bark is gray, with fuzzy cover, older plants have brown-reddish naked bark; Nerium
oleander L. – bark is smooth, ash-gray color and has entirety surface, it peels off as very old
plant with small lamina; Celtis australis L. – outer bark is yellowish and extremely hard, but
porous in the end outer layer.
2.2. Sites characteristics
Interpretation of biomonitoring results is much harder to carry out in regional research
than in cases when the research is headed in immediate vicinity of pollution sources.
Narrower part of Croatian coastal area, especially bigger Dalmatian towns such as Split, is
ideal for this type of research due to low height difference and sea vicinity, so the whole area
belongs to the Mediterranean zone regarding climate and vegetation. Consequently, plant
species adequate for research could be found in urban areas along the coast.
According data on air quality from Public Health Institute for Split-Dalmatian County
there is a visible correlation between pH values and mean annual concentration of sulfates in
total sediment matter what indicates the increase of pH values followed by higher
concentration of sulfates (sulfur) in the air (Table 1).
Bark samples were taken from the following localities (Fig. 1): streets: Gundulićeva ulica
and Poljička cesta – town centre, high traffic intensity, town zone-Meje – town area, lower
traffic intensity, green spots, zone- Dujmovača – north part of the town, industrial zone,
Kaštel Sućurac – in immediate vicinity of cement factory, Kaštel Kambelovac – in immediate
vicinity of plant of plastic products „Adriakem“, Dugi Rat – big traffic and ex-industrial zone,
Brač – island were plants are living in unpolluted environment.
2.3. Sampling
Bark samples were taken from five trees of every studied plant species on each locality.
Total of 240 bark samples were collected. Surface of taken bark samples varied between 25
4
and 35 cm2, with 3 to 5 mm depth, and height from 1.5 to 2.5 m above ground on the tree side
that is facing pollution source. Sampling took place in 2004 and 2005.
2.4. Analysis
Samples were thoroughly brushed and abraded with knife in order to remove eventual
epiphytes and left to dry for 24 hours in desiccators at temperature of 105 °C. Afterwards
from each sample we took 12 g of dry bark and pulverized it in mortar with pestle. Obtained
powder was mixed with distillated water. Suspension was mixed and left for 48 hours at room
temperature in hermetically closed dish (to prevent the contact with CO2 and fungus). pH
values were measured with pH-meter and glass electrode, type CyberScan 510, but were
previously mixed and homogenized with electromagnetic mixer type MM-530. After
measurement pH suspension was divided into two parts. To the first part we added 0.1000
mol/L HCl, while to the other part was added 0,1000 mol/L NaOH. Right after each adding of
acid i.e. alkali the suspension was thoroughly mixed with electric mixer and the pH values
were read after mixing.
2.5. Statistical elaboration of data
Results of measurements are statistically elaborated with ANOVA test, Student t-test and
Bonferroni post hoc test with significance level 0.05.
3. Results
In this paper we have presented the results of determination of acidity and buffer
capacity in six plant species taken from eight different study areas in wider Split town area
(Croatia). Three plants belong to evergreen plants (Nerium oleander, Viburnum tinus,
Pyracantha coccinea) and other three to deciduous plants (Celtis australis, Ficus carica,
Sophora japonica).
Results of analysis have shown that the bark of almost all studied species on all
localities has low level of acidity (Fig. 2). The lowest pH value had Nerium oleander (4.13)
species on the island of Brač, while the highest pH value had Sophora japonica (7.22) species
in Kaštel Sućurac (Fig.2). Comparing values of single plant species on all localities (Fig. 3) it
5
is evident that the lesser changes of pH values occur for the species Pyracantha coccinea, and
the biggest changes occurred for Sophora japonica species.
Analyzed samples show that on some localities mean pH values vary from 5.13 to 6.32
(Table 2) while there is no statistically significant difference between pH values of the plant
bark (F=1.84, p=0,105).
While analyzing media pH values of bark of some plant species on all localities has been
established that between studied plants species exists statistically significant difference
(F=2.91 p=0.024). The lowest pH value had Nerium oleander (4.94) species, while the highest
pH value had Sophora japonica (5.96) species, Table 3.
In our research buffer capacities are expressed by changes in pH bark value after crashing
with precisely determined concentration and volume of hydrogen chloride acid and sodium
hydroxide.
While comparing buffer capacity of Sophore japonice (deciduous trees) and Pyracanthe
coccineae (evergreen trees) on all localities we have found out that statistically significant
higher buffer capacity has Pyracanthe coccinea in comparison to Sophora japonica (4.97 to
6.13); t=3.24; p=0.014 (Table 4).
Buffer capacities of all 6 studied plant species on all localities varied from 4.74 (Kaštel
Sućurac) to 6.4 (Dujmovača, Dugi Rat). Statistical elaboration did not show significant
difference between mean values of buffer capacities of all plants on researched localities
(F=1.17, p=0.341) Table 5.
4. Discusion
Based on available data from literature, in some European regions in the last 40 years
research on changes in pH values of bark pointed out that these changes in plant bark were
result of higher concentration of SO2 in the air (Staxang 1969, Grodzinska 1971, Van Dobben
and Ter Braak 1998). Majority of studies show an important correlation between pH value of
bark and concentration of SO2 in the atmosphere which results with higher bark acidity in
relation to samples of the same species and similar age found in the environmentally clean
surroundings. This proves that pH value of the bark can be used as very good indicator of air
pollution.
6
Ilijanić (1989) did similar research in Croatia, determining pH value of the bark for
the plants specific for the continental area. That type of research was performed in coastal
area too (Bačić and Ruščić 1994). This paper contains following up of atmosphere impact on
bark acidity.
The lowest media pH value was found on locality Dugi Rat (5.13), while the highest was
found in Kaštel Sućurac (6.32) Table 2. Bačić and Ruščić 1994 found out the lowest pH value
on Radničko šetalište street (4,50), while the highest was found in Solin (6.11).
We presume that the obtained media pH values are relatively high due to presence of
alkali particles from the sea in the atmosphere that bond SO2 and SO3 preventing significant
decrease of pH values. The highest pH value found in Kaštel Sućurac can be explained by
presence of cement particles in the air.
Earlier research performed by Ruščić and Bačić, 1994 pointed out that the bark on all
localities was more acidic in relation to control locality, which is Island of Brač. This
observation was not established in this paper.
Bačić and Ruščić 1994, have recorded the lowest pH value for Ficus carica (4.93), while
the highest pH value had Pyracantha coccinea (5.30).
Established differences of buffer capacity on each locality point to the fact that bigger
buffer capacity appears on more polluted localities what could be explained by plant
adaptation to air pollution. Media buffer capacities of single plants on all localities varied
between 4.97 (Pyracantha coccinea) and 7.7 (Celtis australis). Bačić and Ruščić (1994) have
reported that buffer capacity is highest on the localities that have higher level of air pollution.
On the other hand our research from 2005 did not confirm statistically significant difference
between mean buffer capacities on each locality.
Statistical analysis has showed significant difference between media values of buffer
capacities of single plants on all localities (F=7.96; p < 0.001) (Table 6).
Comparison of media values of buffer capacities of evergreen plants (Pyracantha
coccinea, Viburnum tinus, Nerium oleander) and deciduous plants (Sophora japonica, Ficus
carica, Celtis australis) points out to the fact that evergreen plants have higher media values
of buffer capacities (5.46) than deciduous plants (6.34), what confirms earlier reports by
Rasmussen (1978), Härtel and Grill (1972).
7
Based on comparison of research results (Bačić and Ruščić, 1994) with this paper results
the conclusion is that in last 12 years in study area occurred decrease of air pollution due to
close down of some big and obsolescent industrial plants (shoe factory, plastic products plant,
ironworks, ferroalloy plant in Dugi Rat). Generally speaking, there is very evident correlation
between pH of tree bark and pH of sedimentary dust in the air i.e. sulfur concentration, what
has been confirmed in the previous research. Undoubtedly, the fact that our area is
particularly windy is contributing to lesser air pollution and consequently pollution of tree
bark.
5. Conclusion
Results of analysis show that pH values and buffer capacities are specific characteristics
for every plant species. Mean pH values of plant species bark on all localities are statistically
very different. The lowest mean pH value of the bark was found in Nerium oleander species,
while Sophora japonica had the highest mean pH value. Mean pH values and buffer capacity
of plant species according to localities did not significantly differ. Obtained results for mean
buffer capacity values of single plants on all localities varied significantly at evergreen in
relation to deciduous trees.
Acknowledgements
Authors thank to the Institute of Adriatic cultures and land improvement of the karst and
the Institute for Public Health in Split for their help given in preparation of this paper.
5. References
Bačić T. and Ruščić M. 1994. Acidification and buffer capacity of bark in five deciduous
plants from the region of Split (Croatia). Acta Biologica Cracoviensa XXXVI: 51-56
Brown D.H. and Brûmelis G. 1996. A biomonitoring method using the cellular distribution of
metals in moss. The Science of the Total Environment 187: 153-161.
8
Conti M.E. and Cecchetti G. 2001. Biological monitoring: lichens as bioindicators of air
pollution assessment – a review. Environmental Pollution 114: 471-492.
Farmer A.M. Bates J.W. and Bell J.N.B. 1991. Seasonal variations in acidic pollutant inputs
and their effects on the chemistry of stemflow, bark and epiphyte tissues in three oak
(Quercus petraea) woodlands in N.W. Britain. New Phytologist 118: 441-451.
Grodzińska K. 1971. Adification of tree bark as a measure of air pollution in southern Poland,
Bulletin de L´Academie Polonaise des Sciences, Serie des sciences biologiques Cl. II. Vol.
XIX, No 3: 189-195.
Grodzińska K. 1982. Monitoring of air pollutants by mosses and tree bark, In: Steubinga L.
and Jägera H.-J. Monitoring of air pollutants by plants. Dr. W. Junk Publishers, The Hague:
33-42
Härtel O. and Grill D. 1972. Die Leitfähigkeit von Fichtenborken-Extrakten als
empfindlicher Indikator für Luftverunreinigungen. European Journal of Forest Pathology 2:
205-215.
Ilijanić LJ. 1989. Influence of Air Pollution on the Bark pH – values in the region of
Zagreb and Sisak, Acta Botanica Croatica, 48: 63-73.
Jablanović M. and Rožaja D.1980. Zagađivanje i zaštita životne sredine, Zavod za udžbenike i
nastavna sredstva
Kienzl I. 1978. Baumborke als Indikator für SO2-Immissionen. Diss, Karl-Franzens-Univ,
Graz: 272.
Kosmus W. and Grill D. 1986. Die Bedeutung verschiedener Parameter bei der Beurteilung
von Immissionen anhand von Borkenanalysen am Beispiel des Stadtgebietes von Graz.
Mitteilungen des Naturwissenschaftlichen Vereines für Steiermark 116: 161-172.
Lötschert W. and Köhm H.J. 1973. pH-Wert und S-Gehalt der Baumborke in
Immissionsgebieten. Oecologia Plantarum 8: 199-209.
Markert B.A., Breure A.M. and Zechmeister H.G. 2003. Definitions, strategies and principles
for bioindication/biomonitoring of the environment. Bioindicators and biomonitors, Elsevier,
Oxford. 3-39
Moriarty F. 1999. Ecotoxicology - the study of pollutants in ecosystems, 3rd edition.
Academic Press, San Diego: 347.
9
Pacyna J.M. and Pacyna E.G. 2001. An assessment of global and regional emissions of trace
metals to the atmosphere from anthropogenic sources worldwide. Environmental Reviews 9:
269-298.
Pejčinović D., Marinović R. and Hundozi B. 1977. Anatomija biljaka, Zavod za udžbenike i
nastavna sredstva.
Rasmussen L. 1978. Element content of epiphytic Hypnum cupressiforme related to
element content of the bark of different species of phorophytes. Lindbergia 4: 209-218.
Seaward M.R.D. 1995. Use and abuse of heavy metal bioassays in environmental monitoring.
The Science of the Total Environment 176: 129.-134.
Schulz H., Popp P., Huhn G., Stärk H.J. and Schûrmann G. 1999. Biomonitoring of airborne
inorganic and organic pollutants by means of pine tree barks. I. Temporal and spatial
variations. The Science of the Total Environment 232: 49-58.
Schulz H., Huhn G., Schûrmann G., Niehus B. and Liebergeld G. 1997. Determination of
through fall rates on the basis of pine bark loads: results of a pilot field study. Journal of the
Air and Waste Management Association 47: 510-516.
Staxäng B. 1969. Acidification of bark of some deciduous trees. Oikos 20: 224-230.
Tyler G. 1990. Bryophytes and heavy metals: a literature review. Botanical Journal of the
Linnean Society 104: 231-253.
Van Dobben H.F. and Ter Braak C.J.F. 1998. Effects of atmospheric NH3 on epiphytic
lichens in the Netherlands: the pitfalls of biological monitoring. Atmospheric Environment,
32.(3) 551-557.
Whelpdale D.M., Summers P.W., and Sanhueza E. 1998. A global overview of atmospheric
acid deposition fluxes. Environmental Monitoring and Assessment 48: 217-247.
Walkenhorst A., Hagemeyer J., Breckle S.W. and Markert B. 1993. Passive monitoring of
airborne pollutants, particularly trace metals, with tree bark, In: Markerta B.(ed) Plants as
biomonitors: Indicators for heavy metals in the terrestrial environment. VCH VerlagsGesellschaft: 523-540.
10
Figure 1. Map of the study sites: 1) Brač, 2) Gundulićeva ulica, 3) Poljička cesta, 4) Meje, 5)
Dujmovača, 6) Kaštel Sućurac, 7) Kaštel Kambelovac, 8) Dugi Rat
Figure 2.
pH values of studied plant species on the localities: 1) Island of Brač,
2)Gundulićeva street, 3) Poljička street, 4) Dujmovača, 5) Meje, 6) Dugi Rat, 7) Kaštel
Sućurac, 8) Kaštel Kambelovac
Figure 3. pH values of single plant species on all localities: -Brač, -Gundulićeva, Poljička, -Dujmovača, -Meje, -Kaštel Sućurac, - Kaštel Kambelovac, -Dugi Rat
11
Table 1. Mean annual pH and sulfate value in total sediment matter during 2003
LOCALITIES
pH
SEDIMENT DUST
Restricted area of town Split
7,23
Dujmovača
7,77
Kaštel Kambelovac
7,42
Kaštel Sućurac
7,85
Dugi Rat
6,85
c (SO42-) [mg/m2/dan]
9,25
11,79
8,04
17,27
11,00
12
Table 2. Mean pH values of bark of all plant species on each locality
Locality
BRAČ
Split-Gundulićeva
Split-Poljička
Split-Dujmovača
Split -Meje
Kaštel Sućurac
Kaštel Kambelovac
Dugi rat
Number of
measurements
6
6
6
6
6
6
6
6
x±
SD
5,68± 1,02
5,28± 0,86
5,45± 0,36
5,54± 0,65
5,25± 0,35
6,32± 0,64
5,27± 0,83
5,13± 0,48
Minimum
Maximum
4,13
4,26
4,97
4,91
4,70
5,33
4,51
4,63
6,68
6,36
5,98
6,35
5,74
7,22
6,55
6,03
Legend: x±SD: arithmetical media value ±standard deviation
13
Table 3. Mean pH value of bark of single plant species on all localities
Plant
CELTIS
NERIUM
VIBURNUM
FICUS
SOPHORA
PYRACANTHA
Number of
measurements
8
8
8
8
8
8
x± SD
Minimum
Maximum
5,78± 0,62
4,94± 0,61*
5,08± 0,58
5,63± 0,69
5,96± 0,85*
5,55± 0,60
4,85
4,13
4,50
4,51
4,70
4,97
6,68
5,98
6,36
6,65
7,22
6,72
Legend: x±SD: arithmetical media value ±standard deviation, *: p=0,024)
14
Table 4. Mean value of buffer capacities of Sophore japonice and Pyracanthe coccineae on
all localities
Plant
SOPHORA
PYRACANTHA
Number of
measurements
8
8
x±
SD
6,13± 0,88
4,97± 0,88
Minimum
Maximum
4,09
3,32
6,86
5,88
Legend: x±SD: arithmetical media value ±standard deviation
15
Table 5. Mean value of buffer capacities of all 6 species on each locality
Locality
BRAČ
Split-Gundulićeva
Split-Poljička
Split-Dujmovača
Split -Meje
Kaštel Sućurac
Kaštel Kambelovac
Dugi rat
Number of
measurements
2
2
2
2
2
2
2
2
x±
SD
6,06± 1,14
5,90± 1,24
6,12± 0,66
5,99± 0,16
5,35± 0,97
4,14± 0,07
4,84± 2,15
6,01± 0,31
Minimum
Maximum
5,25
5,02
5,65
5,88
4,66
4,09
3,32
5,79
6,86
6,77
6,58
6,11
6,04
4,19
6,36
6,23
Legend: x±SD: arithmetical media value ±standard deviation
16
Table 6. Mean value of buffer capacities of single plant species on all localities
Plant
SOPHORA
PYRACANTHA
VIBURNUM
FICUS
CELTIS
NERIUM
Number of
measurements
8
8
8
8
8
8
x±
SD
6,13± 0,88a
4,97± 0,88b
5,77± 0,93c
5,19± 0,90d
7,70± 1,08a,b,c,d,e,
5,64± 1,16e
Minimum
Maximum
4,09
3,32
4,08
3,65
6,34
4,26
6,86
5,88
7,06
6,39
9,50
8,08
Legend: x±SD: arithmetical media value ±standard deviation Bonferroni post hoc test: a=0.037, b<0.001, c= 0.004,
d=<0.001, e= 0.002
17
16.5
16.8
43.6
8
7
Kaštela Bay
ČIOVO
5
2
4
3
Split
6
Brač Channel
ŠOLTA
1
BRAČ
0
43.3
10km
Figure 1.
18
pH
Locality
Figure 2.
19
pH
Figure 3.
20