Book with abstracts from the COST Action 0905 meeting in ... - UMB

CARBON AND TRACE ELEMENT FLUXES IN THE PORE WATER
OF AN URBAN SOIL FOLLOWING GREENWASTE COMPOST,
WOODY AND BIOCHAR AMENDMENTS, INNOCULTAED WITH
THE EARTHWORM LUMBRICUS TERRESTRIS
Luke Beesley 1 , Nicholas Dickinson 2
1 The James Hutton Institute, Craigiebuckler, Aberdeen. AB15 8QH, UK.
2 Department of Ecology, Lincoln University, Lincoln 7647, Canterbury, New Zealand
Keywords: Biochar, dissolved organic carbon, earthworms, heavy metals, soil carbon.
The benefits of adding composted organic materials to soils to enhance carbon storage and
ecological functionality could be countered by the mobilisation of some harmful pollutants
commonly found in frequently degraded urban soils. Carbon, nitrogen and trace element
fluxes in an urban soil’s pore water were studied in response to the surface mulch addition
and the incorporation into of greenwaste compost and two non-composted amendments; a
woody oversize material and biochar in the presence and absence of the earthworm
Lumbricus terrestris.
Both composted and non-composted amendments enhanced dissolved organic carbon
(DOC) in soil pore water to ~100-300 mg l -1 in the upper depth of the soil profile above
which they were applied as a mulch and similarly within the mesocosms in which they
were mixed. Dissolved organic carbon, dissolved nitrogen (DTN) and trace metals,
especially Cu and Pb, where enhanced to the greatest extent by greenwaste compost,
because of strong co-mobilisation of metals by DOC. Biochar enhanced As and Cu
mobility in the field profile and, additionally Pb in the mesocosms, with no effect on Cd.
The woody, oversize amendment neither greatly increased DOC nor As, Cu, Pb or Zn
mobility although, unlike the other amendments, earthworms increased DOC and Cd
mobility when soils were amended with this material.
Therefore the addition of non-composted materials to some urban soils, versus composted
greenwaste could reduce the risk of mobilising potentially harmful elements, whilst
usefully improving soil quality.