EFFECT OF PLANTS ON THE BIOAVAILABILITY OF METALS AND OTHER CHEMICAL PROPERTIES OF BIOSOLIDS IN A COLUMN STUDY

Abstract

The effects of metal-accumulating plants (Salix x reichardtii and Populus balsamifera) on the chemical properties and dynamics of metals in biosolids were investigated using different techniques including diffusive gradients in thin films (DGT), sequential extraction procedures and partitioning coefficient (K_d). Plants could effectively extract Cd, Ni, and Zn and decreased dissolved organic carbon (DOC). The presence of plants increased the potential bioavailability of these metals, as assessed by an increase in the ratio of metal measured by DGT and metals in the solution. The plants affected the Cd, Ni, and Zn pools (soluble/exchangeable; Fe/Mn oxide and organic matter bound) characterised by sequential extraction and K_d but did not reduce the total metals in either substrate. However, plants had no effect on Cu, presumably because of the effective buffering of available Cu by organic matter in both solution and solid phases. A high density of plant roots was associated with increased leaching of metals.

KEY WORDS::

• bioavailability
• biosolids
• column study
• metals

ACKNOWLEDGMENTS

We acknowledge Melbourne Water Corporation for research funding through the ARC-Linkage Project LP0560294. Thanks are given to Malinda Godino and Augustine Doronila for their assistance with aspects of the experimental work.