Environmental monitoring with arboreal bioindicators at urban areas

The environment condition at urban territories is of the highest importance for all people living there. Environmental monitoring conducted by state authorities and enterprises gives information about the presence of pollution in major components of the urban environment and in food products, physical and radioactive pollution. But these data do not give the full picture of the environment condition, as living organisms react to all changes of environment quality in complex, but not separately to each of them. Therefore it is almost impossible to predict the health risks imposed by the existing environment pollution. So, there is a need to find the indicator, which will provide the information about reaction of biological system to all negative impacts. For this purpose various biological objects and their properties are used as primary receptors of environment pollution to study their reactions and make prognosis about the reaction of human organism exposed to the same factors. Advantages of biomonitoring include reliability and objectivity: the condition of biota is determined by the interaction of environment factors. But adequately reflecting the degree of negative influence on the whole, the bioindicators do not explain, which impact has created the response.
Biological indicators are species used to monitor the health of environment or ecosystem. A good bioindicator will indicate the presence of the pollutant and give rough evaluation of the amount and exposure intensity by the level of reaction. Bioindicators can tell about the cumulative effects of different pollutants in the ecosystem and about how long a problem may have been present, which physical and chemical testing cannot tell. These organisms (or communities of organisms) deliver information on alterations in the environment or the quantity of environmental pollutants by changing in one of the following ways: physiologically, chemically or behaviourally.
Depending on the organism selected and their use, there are several types of bioindicators: plant, animal, microbial and macroinvertebrate indicators. Each of them has their advantages and disadvantages. Therefore the choice of bioindicator must be based on specific conditions of the study area and properties of living organism chosen for investigation. So, the investigation was aimed at choice of the most appropriate for urban conditions indicator organisms or their combination. The applied techniques of biomonitoring were developed by Bogach Y. et al. [1], Voskresenskaya O.I. et al. [2] and Fedorova A.I. [3]. At the same time the first attempts to develop integral scale for biomonitoring results interpretation was performed by Kamanina I.Z. et al. [4]. Now it is possible to combine various methods and approaches to develop multicomponent system of bioindication for urban areas environment control.
Animal bioindication cannot be well applied at urban territories as they are not rich in fauna. Furthermore, this type of biomonitoring involves active search and may give the subtle results due to constant relocation of animals. Therefore, the most appropriate group of indicators, which should be used at urban areas, is plants. The presence or absence of certain plant or other vegetative life in an ecosystem can provide important clues to the environment health assessment.
There are several types of plant bioindicators, including mosses, lichens, tree bark, bark pockets, tree rings, leaves, and fungi. On the whole arboreal plants, both coniferous and deciduous, are the best choice, because they are not too sensible and too tolerant to contamination; they have a prolonged life cycle; and they are wide-spread, but at the same time are linked to certain locality. Another important advantage is that they provide a plenty of material for sampling, first of all, leaves, branches and needles. The biomonitoring using arboreal indicators should involve the following stages.
1. Evaluation of the overall state of plant associations. The condition of trees is determined visually by the sum of basic biomorphological signs: crown density, foliation or level of defoliation, size and color of leaves (needles), presence or absence of deviations and deformations in the structure of trunk, crown and sprout, presence and share of dry sprouts in the crown or dry top, integrity and state of bark. All these signs are produced by negative natural and anthropogenic environmental factors and can be interpreted using the following two scales [3]. First, trees are divided into three quality groups in city planting regulations: good, satisfactory and unsatisfactory conditions. Secondly, there are 6 categories of trees viability: 1 – trees without the signs of weakening, weak, extremely weak, drying, dead trees of current year (dried in the current year), dead trees of past years. This type of assessment can be conducted for big territories and accompanied with sampling for further investigations.
2. Study of the urban environment condition based on the state of coniferous plants. Coniferous trees are known to be the more sensitive to environment pollution. The characteristic signs of environment deterioration and especially air pollution are the appearance of different sorts of chlorosis and necrosises, diminishing of organs sizes (length of pine-needle, sprouts of current and past years, their thickness, size of cones, reduction of size and number of final buds). The last is pre-condition of branching diminishing. Due to slowed growth of sprouts and needles at polluted areas the distance between needles is reduced (there are more needles per 10 cm of a sprout at polluted areas comparing to those of clean areas). Duration of needles life also diminishes (1-3 year at polluted area and 6-7 years at clean). Influence of pollutants also causes sterility of seed (reduction of their germination). All these signs are not specific; however, their sum gives the objective picture.
Needles examined through the magnifying glass, show the presence and character (point, spotted, mosaicism, massive) of chlorosis, necrosises of needle tags and their area should be related to the total total surface of needles. The most sensible young needles are damaged more frequently. The color of damages can be also different: red-brown, yellow-brown, brown-grey and these tints are informative quality signsfor the definition of potential reasons and sources of damage. The mass and density of absolute dry needles (1000 ps.) also diminishes with the increase of anthropogenic pressure and level of pollution
The biggest advantage of coniferous is that they could be used as bioindicators during the whole year. They are also very often found in the composition of protecting green belts and therefore may be used to assess environmental impacts of industrial enterprises or highways.
3. Investigation of biomorphological parameters of leaves. Deciduous trees their own advantage: they change their leaves every year, so deviations from normal environment state detected with their help will be related to very specific period of time. These investigations involve the study of their condition based on the phenomena of asymmetry [2]. In this case, any species, for which bilateral symmetry is typical, can be chosen as a test-object. Differences in width of left and right halves of leaf, length of vein of the second order, distance between the bases of the first and second veins of the second order, distance between the ends of the same veins and angle between the main vein and the second order vein of the leaf. These values could be converted into numbers and thus quantitive assessment of bioindicators will be performed and the results will look more reliable and could be easily compared.
Further it is possible to evaluate the level of technogenic pressure at the area of investigations by studying signs of leaves damage. The thing is that tissues of arboreal plants leaves, damaged as a result of anthropogenic pollution of air, do not take part in photosynthesis and stop to execute the basic functions: synthesis of organic substances, oxygen and phytoncydes production. The dust retaining role of urban plant is also weakened, as dust settles down on slightly moist surface of living leaves. The photosynthesis function highly depends on the area of leaf surface (leaf index). So, the area of leaves is an important bioindicating parameter, which can be easily compared with that of background trees. The visual methods of leaves area estimation and percent of damages of leaf tissues are not very exact, although on the whole they reflect the general picture of damages and green plantations condition. Application of simple reagents (acids) gives possibility to distinguish really dead tissues from others and thus increases accuracy of the results.
4. Application of lab techniques for the investigation of tree leaves resistance to high and low temperatures, dusting and salinization, which gradually deteriorate under the influence of anthropogenic pressure at urban territories.
5. Definition of plant diversity at the study area is a supplementary investigation for the evaluation of environmental factors favorability. Number and condition of grasses is an important for the assessment of environment quality of cities. The most important parameter would be diversity of grasses, their average height and average length of leaves. These should be also compared with the corresponding parameters of grasses, grown in natural conditions.
The results obtained in the course of the offered sequence of urban biomonitoring must be evaluated based on comparative scale, which could be supplemented with point scores. The scale ranges the values of studied parameters to reflect the level of environmental disbalance in the following order – minor, low, medium, high, catastrophic. The corresponding score is made of points obtained for each parameter, if minor level is equal to 0 or 1, low – 2, medium – 3, high – 5, catastrophic – 7. Depending on the number of parameters evaluated, the environmental situation at the study area will be interpreted. The proposed biomonitoring order includes 20 parameters, thus, the most favorable environmental conditions will be at urban areas with the score below 20, 21-40 stand for normal conditions, 41-60 corresponds acceptable situation, 61-80 marks the disturbed condition, 80-100 means that the environment condition imposed high risks for population and if the score is over 100, then the ecosystem is ruined and dangerous for population.
All the results obtained in the course of biomonitoring at certain territory will be subjected to certain criticism due to mostly qualitative character and absence of strong theoretical grounds for their interpretation. However, if the investigation is based on a range of methods applied and indicators studied, as it was offered above, then the result will have higher credibility. Based on combination of various parameters of living bioindicators it is possible to define the level of environmental disbalance and develop a range of recommendations for further degradation prevention.


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Environmental monitoring with arboreal bioindicators at urban areas  [Електронний ресурс]  / Radomska M.M. // Режим доступу: http://eco.com.ua/

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