Trace metal uptake by the grass <Emphasis Type="Italic">Melinis repens</Emphasis> from roadside soils and sediments,tropical Australia |
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Authors: | C Pratt B G Lottermoser |
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Institution: | (1) School of Earth and Environmental Sciences, James Cook University, P.O. Box 6811, Cairns, QLD, 4870, Australia;(2) Present address: Institute of Technology and Engineering, Massey University, Turitea Campus, Palmerston North, New Zealand |
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Abstract: | This study reports on trace metal uptake by the grass species Melinis repens, growing in roadside soils and sediments in tropical northeastern Australia. Median total Cu, Pb, Ni and Zn concentrations
were significantly (P < 0.05) higher in road edge soils (Cu = 61.1 mg/kg, Pb = 97.3 mg/kg, Ni = 28.6 mg/kg, Zn = 729 mg/kg) than in background
soils collected away from roads (Cu = 5.8 mg/kg, Pb = 11.2 mg/kg, Ni = 3.7 mg/kg, Zn = 21 mg/kg). Significantly (P < 0.05) elevated Zn values were recorded in the stems of the M. repens specimens growing on roadside soils (231.6 mg/kg dry weight of tissue) compared with those of grasses growing on background
soils (40.8 mg/kg dry weight of tissue). Moreover, median Cu, Ni and Zn values in the roots of roadside grasses (Cu = 29.1 mg/kg,
Ni = 2.73 mg/kg, Zn = 169 mg/kg) were significantly (P < 0.05) higher than their respective levels in the roots of background M. repens samples (Cu = 5.98 mg/kg, Ni = 0.70 mg/kg, Zn = 22 mg/kg). A greenhouse experiment showed that Cu and Zn in road sediments
are labile and are available for uptake by M. repens. The studied roadside soils and sediments were leached with a diethylenetriaminepentaacetic acid–CaCl2–triethanolamine–HCl extraction solution, which proved to be a rudimentary indicator of Zn availability and uptake to the
root tissue of M. repens. The results demonstrate that trace metals in roadside grasses have the potential to be directed up the food-chain as grasses
are consumed by herbivores. In addition, bioavailable metal contaminants hosted by road sediments have the capacity to impact
on ecosystems downstream of roads because these sediments are mobilised by road runoff waters from road surfaces into adjoining
catchments. |
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Keywords: | Traffic Metals Bioavailability Melinis repens Australia |
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