Rehabilitation of the nematode fauna in a phytostabilized,heavily zinc-contaminated,sandy soil |
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Authors: | Bouwman Lucas A Vangronsveld Jaco |
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Institution: | (1) Alterra, Green World Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands;(2) Limburgs Universitair Centrum, Environmental Biology, Universitaire Campus, B-3590 Diepenbeek, Belgium |
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Abstract: | Background Aim and Scope The Maatheide in Lommel, Belgium, is an extremely metal contaminated, sandy area where vegetation has disappeared over ca.
130 hectares due to the activities of a former pyrometallurgical zinc smelter. To reduce the environmental impact of this
area a rehabilitation strategy had to be developed. Therefore, in the centre of this area, an experimental phytostabilization
(grass) field of three hectares had been installed in 1990. After a grass cover had been established, the development of the
nematode fauna in the phyto-stabilized soil was studied. Nematodes act at various levels in soil ecosystems: herbivorous species
extract their food from plant roots, bacterivorous and fungivorous species feed on microbes, predatory species consume other
nematodes, and omnivorous species have mixed diets. In a mature soil ecosystem that normally exercises its manifold functions,
a diverse nematode fauna occurs, reflecting the intactness of the ecosystem. As such, this fauna is indicative of crop growth,
vegetative diversity, organic matter decomposition, microbial activity and diversity, and the maturity of the soil ecosystem.
Methods A metal immobilizing soil amendment (beringite) and municipal waste compost (to improve the nutrient status and water-retaining
capacity) were incorporated in the soil and metal tolerant ecotypes of grasses were sown. Soil samples for nematode analyses
were taken four times.
Results As a result of the treatment, pH of the soil increased and the water extractable amount of Zn was strongly reduced. Grass
growth revitalized the impoverished soil ecosystem, organisms as well as metabolic processes. The nematode fauna of the experimental
field in the Maatheide has been studied since 1997 and the recovery of the various feeding guilds and taxa was checked again
in 2002. Nematode densities and feeding guilds have normalized, with omnivores and predators as the last guilds to reappear.
Up to 27 species with a current diversity were observed in the grass-covered experimental plot, but a number of ubiquitous
species, present at a comparable site at some distance, remained absent.
Conclusion It can thus be concluded that rehabilitation of an impoverished soil ecosystem is possible in heavily contaminated soils by
means of phytostabilization, but there are some limitations on rehabilitation, since a number of common nematode species remained
absent. Further research should indicate if this absence is indicative of a loss of essential processes in the soil.
Recommendation and Perspective. Phytostabilization of heavily zinc-contaminated, sandy soil also remediates impoverished soil
ecosystems. In particular, the recovery of nematode feeding categories is indicative for the normalization of soil life. The
absence/presence of a number of ubiquitous taxa should be checked again after some time to verify if recovery is completed. |
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Keywords: | Heavy metals nematodes phytostabilization soil ecosystem soil pollution zinc zinc-tolerant grasses |
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