Phytoremediation Potential of Sesuvium Portulacastrum on Remediating Salt Affected Soil

Sesuvium portulacastrum is a salt hyper accumulating plant and pioneer plant species used for desalination and phytoremediation. The plant tolerates abiotic constraints such as salinity and drought. It grows under severe salinity and it can be used for the remediation and restoration of salt contaminated soils affected from industrial effluents. Among the major water demanding industries, the textile industry has biggest impact on the environment related to primary water consumption and waste water discharge. Textile effluent has a large range of organic chemicals of high salinity, high colour and low biodegradability. Salinity exerts negative effects on plant growth and affects the biological stability of ecosystems.The experiment on salt uptake through salt enrichment study was conducted and also to assess the potential of Sesuvium portulacastrum collected from Pitchavaram in Chidambaram District of Tamil Nadu, India for the remediation of dye and textile contaminated area in Andipalayam, Mangalam and Palayakottai villages of Tirupur District of Tamil Nadu was studied upto 70Days After Planting (DAP). The results of the soil analysis revealed that, the initial EC of soil 13.04 dSm-1 is reduced to 7.37 dSm-1(30 Days after planting (DAP) and 5.34 dSm-1(60DAP). The plant shoot length and root lengths were increased to 74% and biomass was increased to 94% in 5000mg/kg of Na enriched soils. The electrical conductivity and sodium content were decreased in Sesuvium grown soil enriched with different concentrations of Na. 77.8% of Sodium was removed from the soil in a span of 90 days. Current world environment Journal Website: www.cwejournal.org ISSN: 0973-4929, Vol. 12, No. (3) 2017, Pg. 687-694 ConTACT Jayashree Ramasamy jayashree.r@tnau.ac.in Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore-641 035, India. © 2017 The Author(s). Published by Enviro Research Publishers This is an Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted NonCommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. To link to this article: http://dx.doi.org/10.12944/CWE.12.3.20 Article history Received: 07 August 2017 Accepted:16 November 2017

introduction Soil and environment are under tremendous pressure due to industrial expansion and discharge of effluents.During the past few decades industrial activities have increased greatly with rapid economic growth, this accomplished severe environmental pollution.Textile industry is a diverse sector in terms of raw materials, processes, products and equipment and has a very complicated industrial chain.Its biggest impact on the environment is related to primary water consumption (80-100 m 3 /ton of finished textile) and waste water discharge (115-175 kg of COD/ton of finished textile, a large range of organic chemicals, low biodegradability, color and salinity).Therefore, reuse of the effluents represents an economical and ecological challenge for the overall sector 1 .The textile effluents have a high concentration of salts, through their accumulation in different trophic levels of ecosystem ultimately cause serious environmental impact in the neighboring receptors like agricultural land and water bodies 2 .
Salinity is one of the major abiotic constraints, manifesting as osmotic stress at an early phase and ionic stress at later phases of plant growth, consequently affecting plants survival mechanisms at cellular, tissue and whole plant level 3,4 .More than 45 million hectares of irrigated land are affected by salt which account for 20% of total land and 1.5 million ha of land are taken out of production each year owing to high salinity level 5,4 .So, it is essential to reclaim the contaminated soil by natural way of using plants.Among the many feasible techniques, phytoremediation is a cost-effective and environmentally sound technology for remediation of salt affected sites.
Sesuvium portulacastrum (L.), a member of the family Aizoaceae, is an important halophyte in the category of "salt accumulator" plants which accumulates high salt concentration in their cells and tissues and overcomes salt toxicity by developing succulence.This plant has a distinct molecular and physiological flexibility that enables it to adapt and survive under various abiotic stress conditions [6][7][8][9][10][11][12][13][14][15][16][17] .It has been observed that the growth characteristics of Sesuvium were improved upon exposure to optimum NaCl concentrations (100 to 400 mM) under in vitro and an increase in growth rate and halosucculence status (200 mM of NaCl) under ex vitro conditions 6,7,8,9,10,11 .
The ability of S. portulacastrum to survive in adverse environmental conditions recognizes it as a possible candidate for the environmental protection 12,6,8,10,[13][14][15][16][17] .The evidence for the ability of this halophyte to desalinise an experimentally salinised agricultural soil (grown for 189 days) is provided 7 and confirmed the growth potentials of test culture Hordeum vulgare (barley) on the desalinised soil.There was a marked absorption of Na + ions by S. portulacastrum roots and their accumulation in the above-ground biomass up to 872 mg plant −1 and 4.36 g pot −1 (about 1 t ha −1 ).Similarly in a study among six species of halophytes studies, S. maritime and S. portulacastrum exhibited greater accumulation of salts in their tissues and higher reduction of salts in the saline land (upto 504 and 474 kg of sodium chloride respectively from the saline land from 1ha in 4 months time).Thus the characteristic feature of Sesuvium to accumulate high amount of salt in its tissues may be exploited for reducing salt levels in the potential agriculture soil and in the arid and semiarid regions by repetitive cultivation and harvesting of this plant in these areas.Hence, the present study aims to assess the phytoremediation potential of Sesuvium plant for the removal of salt from contaminated and salt enriched sites.

Sampling location
Tamil Nadu textile city Tirupur, which has nearly 720 dyeing units, is ranked topmost in terms of generating hazardous waste.According to Tamil Nadu Pollution Control Board, an estimated 8,33,365.75tons of hazardous waste is generated every year in Tirupur.Soil samples were collected from Andipalayam, Mangalam and Palayakottai villages of Tirupur District(Fig.1)

Soil Sample Collection
The Bulk soil samples were collected from dye and textile effluent contaminated sites, for conducting pot culture experiment.These villages represent the pollution status of Tirupur District and recorded high EC values (4.5 to 8.5 dSm -1 ).The initial physicochemical characteristics of the soils samples were analysed by standard operating procedures 22 .

Fig. 1: Sampling location Plant Sample Collection and identification
Pichavaram is the second largest Mangrove forest in the world.The salty marsh area of Pichavaram supports many halophytes.Sesuvium being a coastal plant also act as an inland plant and a mangrove associate and has shown to have nursing effects in mangroves.Salt hyper accumulating plant Sesuvium portulacastrum samples were collected for remediating the salt contaminated soils.The collected salt hyper accumulating plant was identified and confirmed as Sesuvium portulacastrum through Botanical Survey of India and used to assess the salt removal potential.The chemical constituents of the Sesuvium plant was analysed by standard operating procedures 22,26 .Scanning electron microscope image of Sesuvium portulacastrum was also taken to observe the physiology of the plant (Fig. 2).

Salt enrichment
Soil was enriched with different concentration (2000, 3000, 4000 and 5000 mg kg -1 ) of NaCl.A control without any salt addition was maintained to study the salt uptake by the plants.Sesuvium portulacastrum plants were planted in the salt enriched soils and further observation on salt uptake, physico-chemical characteristics of soil and physiological changes in the plant were observed.

Statistical Analysis
The data on various characters studied during the investigation were statistically analysed by the method given by 24 at a (P<0.05).

Results and Discussion
Establishment of Sesuvium portulacastrum in dye and textile effluent contaminated soils (Andipalayam, Mangalam and Palayakottai villages) of Tirupur District was observed and the growth of the plant was good in contaminated soil.At periodical intervals (Month) the soil and plant samples were collected and analysed for physico-chemical characteristics and the role played by Sesuvium plants to remove the salt level was also studied (Fig 3 and 4).
At periodic intervals the role played by Sesuvium plants to remove the salt level was also studied by analyzing the plant characteristics such as pH, EC, Na, K, Ca and Mg (Fig. 4).
The initial EC of the S. portulacastrum plant collected from Pitchavaram is 12.09 dSm -1 which increased to 19.93 dSm -1 in Mangalam village soil (30 DAP), 19.87 dSm -1 in Andipalayam village soil (30 DAP) and 17.59 dSm -1 in Palayakottai village soil (30 DAP).The initial sodium content of the S. portulacastrum plant is 3.2% which increased to 4.4% in Mangalam village soil (30DAP), 3.7% in Andipalayam village soil (30 DAP) and 3.5% in Palayakottai village soil (30 DAP) (Fig. 4).On comparing, it is found that the uptake of salts by Sesuvium plants collected from Pitchavaram was high in soil from Mangalam village than other village soils-Na: 3.2% to 4.4%, K: 1.2% to 1.5%, Ca: 0.06% to 0.14%, Mg: 0.05% to 0.24%.The evidence for the ability of this halophyte to desalinize an experimentally salinised agriculture soil is provided 7 and confirmed the growth potentials of test culture Hordeum vulgare on the desalinized soil.There was a marked absorption of Na + ions by S. portulacastrum roots and their above ground biomass up to 872 mg plant -1 4.36 g pot -1 .Thus the characteristic feature of Sesuviumto accumulate high amount of salts in Fig. 3: influence of S. portulacastrum on soil eC and sodium its tissue may be exploited for reducing salt levels in the potential agricultural soil and in the arid and semi arid regions by repetitive cultivation and harvesting of this crop in these areas 21 .

Salt enrichment Study
Sesuvium portulacastrum plants were planted in the salt enriched soils and further observation on salt uptake, physico-chemical characteristics of soil and physiological changes in the plant were observed.
The EC of the soil was found to considerably decrease throughout the study period of 90 days at four increasing concentrations of Na salt (Table 1).At a NaCl concentration of 2000 mgkg -1 80% reduction in soil EC was seen in 90 days interval.The highest EC reduction was observed in soil enriched with 4000 mgkg -1 of saltupto 82.5 % on the 90 th day.It was also observed that among the four different concentrations of salt enriched soil, the EC reduction was upto 50.6% in the soil enriched with 4000 mgkg -1 NaCl compared to other salt concentrations.Sesuvium plants established in salt enriched soils favored salt uptake which was evident in the decrease in Na in the soil (Table 1).The highest salt removal was seen in soil enriched with 3000 mgkg -1 of NaCl salt upto 81.82 % in 90 days next to which 77.4% removal was observed in soil enriched with 2000 mgkg -1 of NaCl salt.[28][29][30][31][32][33][34] .Sesuvium plants accumulate the inorganic salts in the vacuole, mainly NaCl and organic solutes in the cytoplasm.Na + uptake into vacuoles requiresNa + /H + antiporters in the tonoplast andH + AT Pases and perhaps PPIases to provide the proton motive force.Halophytes vacuoles may have a modified lipid composition to prevent the leakage of Na + back to the cytoplasm 12 .

Conclusion
Sesuvium portulacastrum is a salt hyper accumulating halophyte which compartmentalizes the toxic Na + in the vacuoles and therefore membrane bound transport system regulating cytosolic (Na + ,K + and Ca ++ ) and ion accumulation by increasing the vacuolar volume.Environmentally, the plant's potential has been checked for its survival under different abiotic stress conditions that includes salinity, drought and heavy metal accumulation which makes Sesuvium a useful species as a heavy metal pollution indicator and for predicting soil salinity.Thus the characteristic feature of Sesuvium to accumulate high amount of salt in its tissues may be exploited for reducing salt levels in the potential agriculture soil and in the arid and semiarid regions by repetitive cultivation and harvesting of this plant in these areas.