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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