5. Conclusion
By increasing the nitrogen supply, sewage sludge may have
indirect effects on plant growth. Any bioaccumulated TM would be
diluted in the presence of greater biomass tissue, at which point no
adverse effects would occur. In this study, SS application increased
the nutrient and TM amounts in the soils which were less
susceptible to leaching toward deeper soil layers. However, a
distinction should be made between the sludge rates with respect
to nutrient availability in order to avoid excessive application of
sludge. Since the differences between the 30S and 60S treatments
were not significant, the lower rate should be sufficient to fertilize
young larch. Though this study establishes the benefits of
municipal SS and demonstrates that the risks involved are
minimal, further studies are needed to determine long-term TM
behavior in the soil–plant continuum, with emphasis on assessing
the potential transfer into groundwater and from there into the
food chain.
5. ConclusionBy increasing the nitrogen supply, sewage sludge may haveindirect effects on plant growth. Any bioaccumulated TM would bediluted in the presence of greater biomass tissue, at which point noadverse effects would occur. In this study, SS application increasedthe nutrient and TM amounts in the soils which were lesssusceptible to leaching toward deeper soil layers. However, adistinction should be made between the sludge rates with respectto nutrient availability in order to avoid excessive application ofsludge. Since the differences between the 30S and 60S treatmentswere not significant, the lower rate should be sufficient to fertilizeyoung larch. Though this study establishes the benefits ofmunicipal SS and demonstrates that the risks involved areminimal, further studies are needed to determine long-term TMbehavior in the soil–plant continuum, with emphasis on assessingthe potential transfer into groundwater and from there into thefood chain.
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