Heavy Metal Accumulation In The Plant Parts Of Cassia Fistula

Abstract

Metal pollution in soil poses a serious threat to the human health and safety of agricultural products. To study the entry of nine heavy metals in the medicinal plant Cassia fistula,a field survey was conducted in forest areas of Adilabad District, Telangana State, India and labstudies were carried out at Department of Botany, Osmania University, Telangana, India. The present investigation deals with the accumulation of heavy metals in plant parts of Cassia fistula belongs to family Fabaceae collected from the forest areas of the study area. From the ethnobotanical surveys, it is learnt that the bark of the above plant is used to treat hyperthyroidism in human beings which is the main reason for the selecting the particular plant. The results of the present study revealed that the used part bark shown the mean levels of the nine(9) heavy metals ( Cd, Mn, Fe, Cu, Pb, Ni, Co, Cr, Zn ) within the toxic limits given by WHO in plants. Atomic absorption spectrophotometer Buck Scientific 200 was used to analyse. The present findings provide us a clue for the selection of plant species for utilization in new drug production.

Introduction

Heavy metals are non-biodegradable and persistent environmental contaminants, which may be deposited on the soil surfaces and then adsorbed into tissues of vegetables. The metals classified as heavy metals include: Cu, Co, Cr, Cd, Fe, Zn, Pb, Sn, Hg, Mn, Ni, Mo, V, W. Plants take up heavy metals from the tissue parts exposed to the air in polluted environment as well as from contaminated soil (E.Gameh, 2001). Several studies have proved that roadside environments are polluted by heavy metals released during different operations of the road transport. Heavy metals such as Pb, Cd, Cu, and Zn have been reported to be released into the atmosphere during different operations of the road transport (Akbar KF, et al, 2006, Sharma S, Prasade FM, 2010). The majority of the heavy metals are toxic to the living organisms and even those considered as essential can be toxic if present in excess (Ayodele JT, Oluyomi CD, 2011). The heavy metals can impair important biochemical processes posing a threat to human health (Akbar KF, 2006). Exposure to dust particles with high concentration of toxic substances, especially potentially toxic metals, poses a serious threat to human health (J. Abah, et al., 2014). There are high incidences of occupational diseases and increase of mortality rate. For instance, life spans of such patients are generally less than 45 years (Jintao Liang, 2001). The heavy metals are kept today at top priority list among the water pollutants as they are water soluble, non-degradable, vigorously oxidizing agents and strongly bind to many biochemical units(Anand Kumar, et al., 2018). The present study on heavy metal accumulation in Cassia fistula thus provides useful information for quality control parameters for the pure drugs production. The heavy metal concentration in used plant parts i.e., bark is discussed here can be considered as identifying parameters to identify and authenticate the drug for any heavy metal contamination.

Materials And Methods

1. Plants sampling

Ten (10) plant samples of Cassia fistula were collected at different distances and along three different directions, west, north and north east from the centre of the study area i.e., Seethagondi, Adilabad district, Telangana, India. The plant samples were sampled at 15 cm depth rooting zone and mixed to form composite samples at each location. The choice of plant species collected was based on distance to the source of contamination and the availability at the point of collection as previously reported (Steinborn. M, Breen J, 2009). For each plant species, depending on the biomass, two to six replicate samples were collected from each location within the area of 4 m2. The samples were mixed to form a composite of the particular species, stored and transported in jute bags to the laboratory for detailed analysis.

2. Plant samples Pre-treatment

Plant samples collected from the field were washed under running tap water to remove adhered soil, and were then separated into parts including roots, stems and leaves. The samples were dried in an oven for 48 hrs at 80oC. The dried samples were ground using agate mortar and pestle, sieved to < 2 mm and transferred to bags for storage until further analysis.

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3. Plant analysis for heavy metals

The plant parts were analyzed for heavy metal content for Cd, Mn, Fe, Cu, Pb, Ni, Co, Cr, Zn. 1 g of < 2 mm fraction plant samples was weighed into porcelain crucibles and was ignited in a muffle furnace for 6 h at a temperature between 450 - 500oC. Grey white ash was obtained at the completion of the ashing. The ash samples were allowed to cool and then 10 mL of 2 M HNO3 was added to sample. The solution was evaporated to near dryness on a hot plate and the cooled residues were re-dissolved in 10 mL 2 M HNO3. The solutions were then filtered into 25 mL volumetric flasks. Both the crucible and the filter paper were washed into the flasks, made up to 100 ml with deionised water and then stored in glass test tubes for instrumental analysis. Atomic absorption spectrophotometer Buck Scientific 200 was used to analyze plant digests for the mentioned heavy metals at Central Facilities Research and Development (CFRD), Osmania University, INDIA.

Results And Discussions

The concentration of heavy metals not only vary from taxon to taxon but also vary from a particular part to the other of the same taxon (John &Laerhoevn, 1976) grown not similar or different environmental conditions.

In the bark powder of Cassia fistula, the concentration of Zinc is 0.544 mg/kg., while the Magnesium is 6.984 mg/kg., Cadmium is 0.017 mg/kg., whereas the Copper is 0.265 mg/kg. and Nickel is 0.988 mg/kg., but Cobalt is under detectable limits. Plants collected from the forest area have shown the variations in the concentration of different heavy metals as follows in the used plant part i.e., bark which is given in TABLE-1 and graph-1

Conclusion

Owing to the severe consequences brought by the heavy metal pollution in soil, it is urgent and necessary to control pollution. Based on the knowledge of the heavy metal accumulation in plants, it is possible to select those species of crops and pasturage herbs, for food cultivation and fodder for animals which accumulate fewer heavy metals. The results showed that the plant studied is highly acceptable for its purity pertaining to the heavy metal toxicity suggesting that the plant can be used for the purpose and also safe to produce new plant drug for human beings. These findings suggest that there is need for urgent attention to proffer far reaching solutions to the problems of the exposed contaminated site. To avoid the direct threats of heavy metals to humans, studies on the transfer and sub-chronic toxicity of heavy metals in the food-chain from water, soil, plant, animal to human should be enhanced.

References

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11. HEAVY METAL CONCENTRATIONS IN PLANT BARKS (mg/kg)
12. Cassia fistula zn mg cd cu ni mn fe Cb co 0.54400000000000004 0.98399999999999999 1.7000000000000001E-2 0.26500000000000001 0.98799999999999999 0.88500000000000001 0.997 0.43100000000000011 0 WHO zn mg cd cu ni mn fe Cb co 30 15 10 13 10 80 20 25 4 Heavy Metals