Contents
| AIR HYGIENE REPORT no. 10 | |
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Contents |
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From the foregoing chapters it is evident that plants have a role in the biomonitoring of air pollution. A wide range of plant groups, species and techniques are available. Analysis of plant tissue provides direct quantitative information on relative concentration loads. Alternatively, observing plant responses is a simpler and less expensive technique and can be used as early warning systems.
Lichens, bryophytes, fungi, algae and higher plants have been used in biomonitoring of air pollution. Lichens and bryophytes are the most widely used plant groups in air pollution monitoring. These groups contain tolerant species with effective bioaccumulating properties and sensitive species which show pronounced responses to air pollutants. Passive and active air quality monitoring using these groups can include quantitative evaluations allowing relative pollution assessments to be made. Fungi may have a potential role in the assessment of air pollution impact on forest ecosystems. Algae are useful in the monitoring of nitrogen deposition.
In higher plants the assessment of foliar symptoms are probably the most widely used bioindication techniques. This is particularly true for ozone. The presence or absence of foliar injury has been used to establish zones of impact, while the type of foliar injury has been used to discriminate among various possible air pollutants. However, visible damage is not always specific to a particular pollutant or other environmental stress. In addition not all species have been exposed to all known pollutants to establish their symptom expression.
Traditionally, biomonitoring programmes have been developed in relation to local and industrial sources of pollution. Bioindication programmes on the local scale require less effort due to a relatively easily located point source from which contamination generally follows a gradient. In this instance cause and effects relationships are often obvious. In large-scale surveys other factors such as uneven spatial distribution and pollutant mixtures become more significant. However such large-scale standard monitoring programmes are important in providing data on long-term temporal and spatial trends of air pollutants.
Biomonitoring using plants can be a simple and inexpensive process which lends itself as a potential, adaptable method of assessing air quality in developing countries. However, due to climatic and edaphic differences additional considerations may be necessary. For example, in arid areas cryptogamic flora may be less sensitive to air pollution because of low humidity. Biological monitoring becomes highly applicable in remote areas where continuous, direct air sampling is expensive and impractical.
Laboratory and/or artificial field investigations are often necessary to establish the role of individual pollutants, the synergistic effects of pollutant mixtures, biological responses and tolerances. These studies can be used to establish parameters of biological monitoring programmes conducted under natural conditions. References
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