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Vol. 11 No. 2 - April 2005

Biomonitoring of Air Pollutants with Plants*

By: Ludwig De Temmerman, J. Nigel, B. Bell, Jean Pierre Garrec,

Andreas Klumpp, Georg H.M. Krause & Alfred E.G. Tonneijck

Since the Industrial Revolution at the end of the 19th century it has been recognized that air pollutants can cause dramatic effects on plants. However, the first recognition in print of air pollution damage to vegetation is in John Evelyn’s book “Fumifugium” published in 1661.

Biomonitoring consists of the use of responses of individual plants or plant associations at several biological organization levels in order to detect or predict changes in the environment and to follow their evolution as a function of time. Some plant species are sensitive to single pollutants or to mixtures of pollutants. Those species or cultivars are likely to be used in order to monitor the effects of air pollutants as bioindicator plants. They have the great advantage to show clearly the effects of phytotoxic compounds present in ambient air. As such, they are ideal for demonstration purposes. However, they can also be used to monitor temporal and spatial distributions of pollution effects. Standardization of methods is crucial in order to develop air quality standards based on effect monitoring.

Many plants are useful as bioaccumulators and the choice of species depends on the aims of biomonitoring. Mosses and lichens accumulate heavy metals and other compounds very efficiently because of their large specific surface and slow growth. As such they serve mostly as passive biomonitors to provide an indication of the pollutant impact at the ecosystem level. On the other hand, field crops and vegetables can serve as an immediate step to detect effects on food and fodder quality and safety. Bioaccumulators are not only used to measure deposits of heavy metals but also radionuclides, polycyclic aromatic hydrocarbons, dioxins and all kinds of aerosols which can also be accumulated efficiently. As far as contaminants of food and fodder crops are concerned, they are a crucial step to evaluate the potential transfer to consumers.

The idea of biomonitoring goes back to the 19th century when NYLANDER (1866) used the abundance of lichens as a measure for air pollution effects. For the purpose of surveying ambient air quality, biological indicators were used the first time in 1958 in the basin of Los Angeles, US; however, the low cost of this method in comparison to the chemical-analytical methods was the decisive factor by otherwise similar objective targets (HECK 1966). HEGGESTAD & DARLEY (1969) reported work with tobacco (Bel–W3) on the detection of ambient oxidant effects in California and VAN RAAY (1969) used indicator plants to study the effect of HF and SO2 in the Netherlands. However, it was SCHONBECK et al. (1970) who pointed out for the first time, that biological indicators gain effects-related information which cannot be assessed by means of chemical analytical methods of air pollution monitoring systems.

The significance of biomonitoring air pollution burden by plants offers some important results from different abilities:

  • Plants show an integrated response to the pollution climate, thus giving information even on the potency of complex pollutant mixtures, occurring simultaneously or alternatively in a stochastic pattern, reacting only to the effective part of a given pollution situation. This allows largely realistic estimates of the given risk potential with regard to the objectives to be protected.

  • Plants react to an ambient air pollution burden (often with a strongly fluctuating pattern) with an assessable and verifiable reaction, while modeling of dose-effects renders information with a much lesser degree of confidence due to e.g. random distribution of pollutants in time and space.

  • Different levels of organization of the plant can be used for biomonitoring, ranging from the single plant (leaf or even plant cell) to the plant association and the ecosystem. The response that is obtained at the community level (e.g. shift in species composition) is a result of an integration of different factors over a relatively long period experienced by competitive plant species and as such cannot be detected on the basis of physical and chemical measurements.

  • Some air pollutants have very low ambient concentrations and are difficult to measure accurately with physical and chemical methods. Plants can accumulate those pollutants to a level that is easier to analyze.

  • Effects are expressed in sensitive plant species as visible injury (leaf injury or changes in habit), and in less sensitive species (even pollution-tolerant species) in the accumulation of pollutants; both providing an important tool in recognizing air pollution effects (making the invisible visible) and/or the transfer of trace pollutants within the biological chain.

Many of these attributes render biomonitoring as being particularly suitable for developing countries. In such places there is generally only a very limited air monitoring network and biomonitoring offers the opportunity to determine the large scale pattern of pollutant distribution, as well as temporal changes. Continuous physico-chemical monitoring requires the use of expensive equipment and skilled personnel, as well as ready access to maintenance of the former and access to spare parts. These are invariably in short supply in most developing countries and in many cases effectively non-existent.

There are several possible goals when carrying out biomonitoring of air pollutants.

  • Spatial distribution of air pollutants in order to map pollution effects on regional or supra-regional scale. This can be carried out for air pollution effects with bioindicators and for deposits of particulate and gaseous pollutants with bioaccumulators.

  • Temporal distribution of air pollutants (time series) can also be done to assess effects of particulate deposition as well as gaseous pollutants.

  • Source monitoring is a lot easier than large scale monitoring and is applicable to a broader range of pollutants when they reach phytotoxic levels. The climatic differences between the different measuring locations are almost negligible on a regional scale.

  • At the ecosystem level, the plant community is a very interesting tool to study the pressure of air pollution on plant communities and ecosystems and to detect effects on biodiversity.

  • Bioindicator plants are also very useful to draw public awareness to air pollution problems, since they can demonstrate the visibility of otherwise invisible air pollutants, especially in city environments and in developing countries where industrialisation and urbanisation are increasing.

  • Plants could probably serve as health indicators. Comparisons of biomonitoring work on trace elements and the occurrence of epidemiological disturbances in human health can be helpful, but are not yet convincing and need to be developed further. Bioaccumulator plants are particularly valuable in order to study the transfer of airborne chemicals to the food chain as crops can be used for this purpose.

  • Biomonitoring offers a support and scientific background for the elaboration of effect-based limit values and directives on air quality.

Ludwig De Temmerman, Veterinary & Agrochemical Research Centre, Tervuren, Belgium 

Nigel Bell, Imperial College, London, U.K. 

Jean-Pierre Garrec, INRA Nancy, Champenoux, France 

Andreas Klumpp, Institute for Landscape & Plant Ecology, University of Hohenheim, Stuttgart, Germany 

Georg H.M. Krause, Landesumweltamt Nordrhein-Westfalen, Essen, Germany

Alfred E.G. Tonneijck, Wageningen University& Research Centre, Wageningen, The Netherlands 

(*Condenced from “Urban Air Pollution, Bioindication & Environmental Awareness” edited by Andreas Klumpp, Wolfgang Ansel & Gabriele Klumpp & published by Cuvilier Verlag, Gottingen, 2004)


This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.


 

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