Heavy Metal Accumulation Potential of Some Wetland Plants Growing Naturally in the City of Kolkata, India

Abstract

Freshwaters are not only used locally in many developing countries but they are often over exploited for domestic purposes, agriculture and disposal of industrial wastes which result in an overload of excess nutrients, harmful chemicals and heavy metals. Plant species together with sediments and water samples collected from eleven aquatic water bodies in the vicinity of industrial units in Kolkata were studied for their potential to uptake Pb, Cd and Cr under field conditions. Cd and Cr concentrations in the sediments were higher than background values considered to be toxic.Alternanthera philoxeroides and Eichhornia crassipes were the two invasive species present, with the former being more widely distributed. Among native plants, Ipomoea aquatica was the most abundant. Metal uptake in the plants differed among species, tissues and sites. Pb and Cd accumulation in root tissues for all plants in most sites suggested an exclusion strategy for metal tolerance. Since I. aquatica is widely consumed in many parts of SE Asia, its metal content should be checked before use since it was found to efficiently translocate both Pb and Cd from roots to shoots.The potential of A. philoxeroides as a metal excluder needs to be explored further since it translocates less to its shoots as compared to E. crassipes and I. aquatica.

Biomonitoring of Heavy Metals Level in Wetland Plants of Lagos Lagoon, Nigeria

“…N. lotus, C. benghalensis, and P. stratiotes (TF>1) also exhibited considerable translocation potential for Ni (1.68), Cr (1.21) and Cr (2.50) respectively. This study corroborates the results of Jha et al (2016) who suggested that A. philoxeroides shows considerable promise not only as an efficient accumulator of Pb and Cd in its roots but its ability to rapidly uptake heavy metals even at very low ambient levels could also make it an efficient indicator of the aquatic ecosystem quality. Table 4: Bioaccumulation factor and Translocation factor * TF greater than 1, a BAF less than 10, h BAF greater than 10…”

“…Pb level in the roots was highest in Eichonia crassipes (5.69 mg/kg) and least was in the roots of Ludwigia adscendens (0.15 mg/kg). All the plants harvested for this study were healthy and did not show any toxicity symptoms, however, excess Pb in plants had been reported to inhibit growth while Cd can inhibit photosynthesis and mineral assimilation causing leaf chlorosis, necrosis, and abscission (Adesuyi et al, 2015a;Jha et al, 2016). Ipomoea involucrata also had the highest level of Cd in its shoots (0.45 mg/kg) while the shoots of Phragmites australis, Eichonia crassipes, Ludwigia adscendens, and Phragmites australis all had the least Cd level (0.01 mg/kg) in their shoots.…”

“…In this study, the general trend of higher concentration of heavy metals in plants roots than in shoots was obvious which seems to indicate bioaccumulation. Heavy metal species can have different bioavailability to wetlands plants because of physiological differences with respect to uptake sites and uptake mechanisms (Jha et al, 2016). Soil geochemistry influences metal speciation in soils and sediments while plant physiology and genotypic differences control the ability of plants to accumulate plant-available forms of metals (Brook and Robinson, 1998).…”

“…Bio-accumulation Factor (BAF) is used to quantify the toxic element accumulation efficiency in plants by comparing the concentration in the plant part and an external medium (Rezvani1and Zaefarian, 2011). BAF has been categorised as: <1 excluder, 1 -10 accumulator and >10 hyperaccumulator (Jha et al, 2016). It can be seen from table 4 that the extent of accumulation of heavy metals by individual plants differed not only with the type of metal but also with the sampling points.…”

“…Transfer factors for most of the plants species were less than 1, indicating that metals accumulated by these plants were largely retained in the roots. High accumulation of heavy metals in roots and low translocation in shoots may indicate appropriateness of a plant species for phytostabilisation (Archer and Caiwell, 2004).This mechanism of partitioning is a common strategy of plants to concentrate harmful ions in the roots in order to prevent toxicity to the leaves which is the site of photosynthesis and other metabolic activities (Jha et al, 2016). A. philoxerrides had translocation factor greater than one for Ni (10.30), while for Cr was 1.25 and 1.40.…”