Phytoremediation assessment of Gomphrena globosa ... - Springer Link

Environ Monit Assess (2015) 187: 387 DOI 10.1007/s10661-015-4618-z

Phytoremediation assessment of Gomphrena globosa and Zinnia elegans grown in arsenic-contaminated hydroponic conditions as a safe and feasible alternative to be applied in arsenic-contaminated soils of the Bengal Delta A. J. Signes-Pastor & S. Munera-Picazo & F. Burló & M. Cano-Lamadrid & A. A. Carbonell-Barrachina

Received: 8 January 2015 / Accepted: 19 May 2015 / Published online: 29 May 2015 # Springer International Publishing Switzerland 2015

Abstract Several agricultural fields show high contents of arsenic because of irrigation with arseniccontaminated groundwater. Vegetables accumulate arsenic in their edible parts when grown in contaminated soils. Polluted vegetables are one of the main sources of arsenic in the food chain, especially for people living in rural arsenic endemic villages of India and Bangladesh. The aim of this study was to assess the feasibility of floriculture in the crop rotation system of arsenic endemic areas of the Bengal Delta. The effects of different arsenic concentrations (0, 0.5, 1.0, and 2.0 mg As L−1) and types of flowering plant (Gomphrena globosa and Zinnia elegans) on plant growth and arsenic accumulation were studied under hydroponic conditions. Total arsenic was quantified using atomic absorption spectrometer with hydride generation (HG-AAS). Arsenic was mainly accumulated in the roots (72 %), followed by leaves (12 %), stems (10 %), and flowers (0.05) and then by plants treated with 2.0 mg As L−1 (Fig. 2). The reason for the positive growth response of the As-treated plants might be related to the interaction between As and phosphorus in the plant metabolism. Due to the similar chemical properties, arsenate and phosphate are taken up by the common carrier and compete during the uptake in the plant system (Meharg et al. 1994; Sharples et al. 1999; Asher and Reay 1979). However, the phosphate/arsenate plasma membrane carrier has a much higher affinity for phosphate than arsenate (Meharg and Macnair 1990, 1992; Burló et al. 1999), which leads to beneficial plant growth by enhancing the phosphorus uptake (Tu and Ma 2003; Cao et al. 2009). Total arsenic content and distribution Most of the As taken up into the flowering plants from the nutrient medium was accumulated in the root system. The highest As concentrations in the root systems were 85 and 82 mg As kg−1 of dry weight (d.w.) for Globe amaranth and Zinnia, respectively. Much lower As concentrations were progressively found in stems

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A

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Dry Biomass (g d.w plant )

Fig. 2 Effect of As concentration in the nutrient medium (0, 0.5, 1.0, or 2.0 mg As L−1) and sampling time on dry biomass (g d.w.) per plant (Globe amaranth (a) and Zinnia (b))

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and leaves and finally flowers. Figure 3 shows the mean distribution of As (%) in the different parts of the plants under this study. Arsenic accumulation showed the following values (mean of both Globe amaranth and Zinnia plants treated with all As concentrations): 72 % of the t-As accumulated in plants was located in the root system, 10 % in the stems, 12 % in the leaves, and finally less than 1 % in the flowers. A similar distribution was also reported for tomato plants: 85 % in the root system, 14 % in shoots (leaves and stems), and only 1 % in tomatoes, and allowed researchers to classify tomato plants as highly tolerant to As (Burló et al. 1999). In fact, the most extended mechanism involved in plant

tolerance is limiting upward As transportation by accumulating the metalloid onto the root surface system, absorbing it with phytochelatins (Smith et al. 2008; Carbonell-Barrachina et al. 1997, 1999a, b; Meharg and Macnair 1991). It has been assumed that biochemical As-detoxification occurs within the plants by methylation and that both tolerant and non-tolerant plants are capable of biologically detoxifying As but at a different ratio (PeraltaVidea et al. 2009). The two types of flowering plants studied (Globe amaranth and Zinnia) did not show any As-phytotoxic signs and grew and bloomed well, which means that

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Environ Monit Assess (2015) 187: 387

Fig. 3 As distribution (%) within Globe amaranth and Zinnia plants (roots, stems, leaves, and flowers)

(%) ution in Plant Arsenic Distrib

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both could be considered as As-tolerant plants. This was one of the main finding of this experiment and supports the fact that flowering plants could be economically grown in As-polluted agricultural soils. Figure 4 shows that As content in plants (addition of the As accumulated in roots, stems, leaves, and flowers) increased with the As concentration in the nutrient solution. Despite the significant increase in As accumulation, the flowering plants evaluated did not show any As-phytotoxic signs. This highlights that biochemical As detoxification might help in neutralizing the phytotoxic effect (Peralta-Videa et al. 2009). Figure 4 shows the effect of As concentration (0, 0.5, 1.0, or 2.0 mg As L−1) and sampling time on total As content (mg kg−1 d.w.) accumulated by Globe amaranth (A) and Zinnia (B). The Globe amaranth plants showed the highest As concentration at the third sampling when treated with 1.0 mg As L−1 (35.337, 36.528, and 49.172 mg As L−1 for the first, second and third sampling, respectively; P < 0.05) and 2.0 mg As L−1 (58.000, 67.000, 95.357 mg As L−1 for the first, second, and third sampling, respectively; P