Industrial hemp (Cannabis sativa L.) growing on heavy metal contaminated soil:: fibre quality and phytoremediation potential

Hemp (Cannabis sativa L.) was used to examine its capability as a renewable resource to decontaminate heavy metal polluted soils. The influence of heavy metals on the fibre quality was of special interest, Determination of heavy metal content was carried out by means of atomic absorption spectroscopy (AAS). Four different parts of the plant were examined: seeds, leaves, fibres and hurds. In each case, the concentration relation was Ni > Pb > Cd. However, the heavy metal accumulation in the different parts of the plant was extremely different. All parts of hemp plants contain heavy metals and this is why their use as a commercially utilisable plant material is limited. We found that the highest concentrations of all examined metals were accumulated in the leaves. In this field trial, hemp showed a phytoremediation potential of 126 g Cd (ha vegetation period) (-1). We tested the fibre quality by measuring the pure fibre content of the stems and the fibre properties after mechanical separation. In addition, the fibre fineness was examined using airflow systems and image analysis. The strength was measured by testing single fibre bundles with a free clamping distance of 3.2 num using a universal testing device. Finally, we compared the results from the stems and fibres from trials on heavy metal polluted ground with hemp stems and fibres from non-polluted ground. Since there was no comparable unpolluted area near the polluted one. reference values were taken from an area quite far away and subsequently with a different soil composition and also exposure to different meteorological conditions, Thus, the observed differences are only partially caused by the heavy metal contamination. (C) 2002 Elsevier Science B.V. All rights reserved.