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Field effects of LAS enriched sludge on soil fauna. Paul Henning Krogh John Jensen Martin Holmstrup National Environmental Research Institute Kristian K. Brandt Veterinary and Agricultural University Georgio Cassani CONDEA Augusta Italy Kaj Henriksen Aalborg University. Aims.
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Field effects of LAS enriched sludge on soil fauna Paul Henning Krogh John Jensen Martin Holmstrup National Environmental Research Institute Kristian K. Brandt Veterinary and Agricultural University Georgio Cassani CONDEA Augusta Italy Kaj Henriksen Aalborg University
Aims • Is LAS toxic under field condition? • How does the laboratory results agree with field results? • How can we explain the field results?
Blok 1 Blok 2 Blok 3 Blok 4 Blok 5 12 m 19 m Experimental design Aerobic sludge + LAS g kg-1 “0” 10 50 4 cm 2 0 4 cm
100 80 60 40 20 0 MAY JUN JUL LAS disappearance from sludge LAS % remaining of initial
Digging up a soil block for determination of earthworm abundance
F. fimetaria Individuals 103 m-2
Willemia sp. Individuals 103 m-2
M. macrochaeta Individuals 103 m-2
Prostigmatid mites Individuals 103 m-2
Gamasid mites (predators) Individuals 103 m-2
Astigmatid mites Individuals 103 m-2
Summary of results Short term: • Colonisation of all soil invertebratesstudied is inhibited by LAS (except two groups of mites) Long term: • Collembolans and earthworms have recovered from LAS • Enchytraeids did not recover from LASafter 5 months • Mites and M. macrochaeta are stimulated by LAS
Lab toxicity of LAS in soil H. assimilis 500 F. fimetaria , mg kg-1 H. aculeifer 400 300 EC50 reproduction 200 A. caliginosa A. longa E. albidus 100 0
How does laboratory results agree with field results? • Inhibitory effects both in lab and field to all soil invertebrates except gamasid mites • Enchytraeids were the most sensitive species in both lab and field • Earthworm and enchytraeid populations were not more sensitive to LAS compared with microarthropods • Recovery of earthworms and collembolans
Conclusion LAS in sludge has a short term toxic effect to soil invertebrates in sludge, but recovery has been attained for allmost all soil invertebrates, except enchytraeids that had just started to recover