Contents
| AIR HYGIENE REPORT no. 10 | |
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Contents |
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Herbs and trees have been used in biomonitoring both as bioaccumulators and bioindicators by exhibiting symptoms of visible injury.
Taylor et al. (1990) reported acute injury symptoms and growth abnormalities of ethylene. Most of this information has been obtained from laboratory studies. The age of tissue, presence of other pollutants and temperature will affect plant sensitivity to ethylene.
In conifers, yellow tips on needles are a common response to ethylene. Necrosis and abscission of cones has also been recorded. Abscission of leaves and flowers in broad-leaved trees usually occurs. Loss of bark has been observed in elm.
Various effects have been observed in herbs, grasses and crops. These include curling and twisting of leaves prior to abscission in lily, tulip and hyacinth. Chlorosis followed by necrosis has been detected in rose plant leaves while beet and radish have exhibited red/purple discolouration. With regard to flowers, delayed opening, premature opening, inhibition of flowering, promotion of flowering, flower close, loss of petals, necrosis and male flowers becoming female flowers have all been observed in different species. Bushy plants and promotion of senescence are general features observed in many herb, grass and crop species in response to ethylene exposure. References
Felsot et al. (1996) used injury symptoms in pea, bean and corn seedlings to assess the exposure of non-target crops to atmospheric deposition of herbicide residues from drift or localised transport of herbicide residues. The most frequently observed symptom was chlorotic spots on the upper leaf surfaces on exposure to sulfonylurea herbicides. Exposure to phenoxyacetate herbicide caused stem kinking and abnormal twisting with leaf cupping. Bright green veins appeared on leaves exposed to the herbicide aminophosphonate while discrete necrotic circular spots characterised exposure to bipyridilinium.
Most studies involving plants as bioacccumulators involve passive monitoring.
In France, Granier and Chevreuil (1992) used tree leaves from the plane tree Plantanus vulgaris as bioindicators of aerial organochlorines. Plants absorb PCBs mainly from the surrounding atmosphere and not from the roots. However this may not be true for other organic compounds. The authors calculated air/leaf bioconcentrations factors of 105 for PCBs and 104 for lindane. PCBs showed spatial and temporal variation throughout Paris. The authors recommended the use of tree leaves in both point source emission assessment and on larger scale studies. References
Kylin et al. (1994) developed an analytical method for the determination of PCB in pine needle wax. This was applied to pine needle samples collected as part of a mapping distribution programme of organochlorines in Europe. The importance of this technique is that it allows specific and precise measurement of PCBs in needles of varying age classes, enabling not only spatial but temporal trends to be established.
Herbs have also been recognised in organic biomonitoring. Goldenrods, a widely distributed indigenous weed, are excellent accumulators of PCB (Weinstein and Laurence, 1989). References
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