Bio-accumulation and distribution of heavy metals in fibre crops (flax, cotton and hemp)

Abstract

Flax, hemp and cotton, grown in industrially polluted region, were included in the present research. The experimental plots were situated at different distances (0.5 and 15 km) from the source of pollution-the Non-Ferrous-Metal Works (MFMW) near Plovdiv. We investigated the level of pollution and the way heavy metals enter the fibre crops, by taking soil and plant samples. The contents of heavy metals in plant materials (roots, stems, leaves, seeds, flowers) were determined after the method of the dry mineralization. The quantitative measurements were carried out with inductively-coupled plasma (ICP). A clearly distinguished species peculiarity exists in the accumulation of heavy metals in the vegetative and reproductive organs of flax, hemp and cotton. Flax is the crop that most strongly absorbs and accumulates heavy metals from the soil, followed by hemp and cotton. The distribution of the heavy metals along the plant axis of the studied crops seems to be selective, therefore their contents in flax and hemp are decreasing in the following order: roots > stems > leaves > seeds, while in cotton: leaves > seeds > roots > stems. A strongly exhibited tendency towards decrease of the contents of heavy metals in the fibre crops is observed as the distance from the NFMW increases. Flax and hemp are cultures, suitable for growing in industrially polluted regions-they remove considerable quantities of heavy metals from the soil with their root system and can be used as potential crops for cleaning the soil from heavy metals.