field effects of las enriched sludge on soil fauna

National Environmental Research Institute Department of Terrestrial Ecology

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Field effects of LAS enriched sludge on soil faunaPaul Henning KroghJohn JensenMartin HolmstrupNational Environmental Research Institute

Kristian K. BrandtVeterinary and Agricultural University

Georgio CassaniCONDEA Augusta Italy

Kaj HenriksenAalborg University


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Aims

• Is LAS toxic under field condition?• How does the laboratory results

agree with field results?• How can we explain the field

results?


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Mixing LAS into sludge


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Laying down stringof sludge in soil groove


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LAS in sludge stimulates plant growth


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Experimental design

19 m

12 m

Blok 2 Blok 3 Blok 4 Blok 5Blok 1

Aerobic sludge + LAS g kg-1

4 cm

cm 2

4

0

50“0” 10


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Plant roots grow in whole bundles through the sludge


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LAS disappearance from sludge

0

20

40

60

80

100

MAY JUN JUL

LA

S %

rem

ain

ing

of

init

ial


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Digging up a soil block for determination of earthworm abundance


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A. caliginosa


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Enchytraeids in sludge


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Enchytraeids in soil


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F. fimetariaIn

div

idu

als

10

3 m

-2


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Willemia sp.In

div

idu

als

10

3 m

-2


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M. macrochaetaIn

div

idu

als

10

3 m

-2


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Prostigmatid mitesIn

div

idu

als

10

3 m

-2


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Gamasid mites (predators)In

div

idu

als

10

3 m

-2


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Astigmatid mitesIn

div

idu

als

10

3 m

-2


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Summary of resultsShort term: • Colonisation of all soil invertebrates

studied is inhibited by LAS (except two groups of mites)

Long term:• Collembolans and earthworms have

recovered from LAS• Enchytraeids did not recover from LAS

after 5 months• Mites and M. macrochaeta are

stimulated by LAS


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Lab toxicity of LAS in soilE

C50

rep

rod

uct

ion

, mg

kg

-1

0

100

200

300

400

500H. assimilis

F. fimetaria

H. aculeifer

A. caliginosa

A. longa

E. albidus


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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


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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

field effects of las enriched sludge on soil fauna

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