A study on the application of phytoremediation ecological technology of heavy metals in water using E. fluctuans: A medicinal plant adapting to climate change

Abstract

Phytoremediation can be used as a different approach to absorb heavy metals because of environmentally friendly and potential cost-effective. E. fluctuans is one species of herbaceous, semi-aquatic, widely distributed in Vietnam, South and Southeast Asia, and tropical Africa. Its leaves, used as edible vegetables, are also used in traditional medicine to treat a number of ailments. This paper aims to test the effectiveness of E. fluctuans in removing heavy metals  from the aquatic environment. The experiments were performed using healthy, young, and acclimatized E. fluctuans. Water containing 0.5 mg/L cadmium, 0.5 mg/L arsenic, 2 mg/L lead, 5 mg/L zinc, and 5 mg/L copper concentrations were experimented with 100 g of E. fluctuans in 30-liter foam containers. The experiments were repeated three times. Throughout the course of the trial, water samples were tracked and their heavy metal concentrations were examined every 10, 20, and 30 days. Through the use of inductively coupled plasma-mass spectrometry, the heavy metals were identified. After 30 days, E. fluctuans could remove Cd at 83.4%, As at 60.8%, Pb at 60.4%, Zn at 40.5%, and Cu at 58.7%. Thus, the E. fluctuans show a high potential for effectively extracting heavy metals from industrial effluent.

INTRODUCTION

One of the most important resources for human survival and daily activities is water 1 . When the global population continuously increases, it is also increasing the food demand and intensive activities of industry and urbanization leading to the requirement of water owing steadily increasing. However, the quantities of water are gradually degraded in many areas due to the expanded volume of huge amounts of dangerous chemicals from intensive agriculture and industries as well as human activities that of contaminated waste and wastewater released directly into the natural environment 2 . Especially, ollution from heavy metals is an emergency impact to the environment and human health because of their toxic properties, tendency, and persistent in nature 3 , 4 , 5 . Specifically, excessive levels of heavy metals including Cd, A, Pb, Zn, and Cu in wastewater will pollute water sources and easily accumulated in the human body by drinking the water without or un-well treatment. Those heavy metals can cause deleteriously affecting human health even though at very low concentrations 6 .

Among the most appealing research areas is the development of environmentally friendly and effective wastewater treatment systems. Phytoremediation is acknowledged as an ecological remediation technology that is climate change-adapted and is thought to be a viable technique for removing contaminants from wastewater 7 .

Aquatic plants are essential for maintaining water resources in the phytoremediation system, as a part to absorb energy, organic matter, and heavy metals in the water, which is greatly improving the water quality 8 . Previous researches have found a number of aquatic plants improving the water environment such as Water Lily , Cyperus Alternifolius , Phragmites Australis , Water Hyacinths , Water Spinach , Typha Orientalis ... Besides, E. fluctuans is considered as a potential aquatic plant remove heavy metals in water.

E. fluctuans commonly known as helencha or harkuch is a tropical herb. It is belonging to Asteraceae family which is importance species for therapeutic process. This herbaceous vegetable plant, which is edible and semi-aquatic, has serrated leaves and is widely grown in Vietnam. The plant is a prostrate herb with 1-3 inch long, opposing sessile, linear oblong leaves. The herb is often pubescent and glandular, with a glabrous texture. The stems have a length of 0.3–0.6 m and can either simply extend or divide at the nodes. The leaves have a hint of bitterness, and they are good for treating smallpox, bronchitis, leucoderma, nervous affliction, laxative, and inflammation. The nutritional worth of plants, such as β-carotene, saponins, cholesterol, glucoside, and enhydrin, among others. Moreover, E. fluctuans ’s fuel extract contains antioxidant, hepatoprotective, CNS depressant (Central Nervous System (CNS) depressants), analgesic, and Antidiarrheal activity 9 , 10 , 11 .

Vietnam is a tropical country with year-round high temperatures and humidity. The country has a long coastline of 3,260 km with more than 2,360 rivers and streams and thousands of lakes and ponds 12 . This water source is the habitat of animals, plants, and millions of people and is also the main source for production. However, overuse and various levels of pollution are causing these water resources to be severely damaged and destroyed. Even many rivers, river sections, ponds, and lakes are “dead” by the volume of waste, garbage and wastewater discharged into the environment without being treated.

However, there have been a few studies in Vietnam about the ability of aquatic plants to treat wastewater pollution. Furthermore, it is still no research about using E. fluctuans to treat heavy metal pollution in wastewater, especially in industrial wastewater. It is necessary to investigate the research on the use of E. fluctuans - A medicinal plant with potential in phytoremediation of water contaminated by heavy metals. The study will send the significant theory and practical results of uptake heavy metals contaminants from industrial wastewater by E. fluctuans.

PHARMACOLOGICAL ACTIVITY OF E. FLUCTUANS

Medicinal plants are a class of plants that are used for medicinal purposes and have specific active medicinal components together with certain traits or attributes that allow them to be used as drugs or therapeutic agents 13 .

A small genus of marsh herb known as E. fluctuans (Family: Asteraceae) is found in tropical and subtropical regions . The plant is an annual herb that spreads to the prostate. This is another edible, semi-aquatic herbaceous vegetable plant that grows throughout Vietnam and has serrated leaves 14 Between november and january, the wet roadside canals and marshy waste areas are the primary habitats for E. fluctuans 13 . It is a plant with medicinal potential in Bangladesh, Malaysia, Srilanka, Zambia, Zimbabwe, India, China, Thailand, Indonesia, Southeast Asia, Tropical Africa, and Vietnam. From ancient times, folk medicine has been used in all of E. fluctuans to treat a wide range of illnesses, with different countries having different indications. The pharmacological activity of E. fluctuans are detailed in Figure 1 .

Figure 1 . The pharmacological activity of E. Fluctuans

E. Fluctuans may have some anti-cancer properties. Though it has only been shown against Swiss Albino Mice with Ehrlich's Ascites Carcinoma (EAC). Therefore, more investigation is required to ascertain the anti-cancer potential of the plant extracts 15 . In addition to its antioxidant qualities, it possesses antimicrobial, cytoprotective, anti-inflammatory, analgesic, CNS depressant (Central Nervous System (CNS) depressants), and thrombolytic characteristics. The abundance of biomolecules in the database suggests that more study will advance the pharmaceutical industry.

MATERIALS- METHODS

Chemicals and instruments

Standard solutions containing 100 µg/mL of copper, zinc, lead, arsenic, and cadmium were made. All of the compounds were pure substances produced by Merck Chemical in Darmstadt, Germany. The water used to make the solutions was double-distilled.

The research employed various instruments such as an analytical balance with a precision of 0.0001 mg, a flask, a test tube, an electric stove, and a micropipette. ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) equipment made by Perkin Elmer ELAN 9000 was used to analyze the samples.

Experimental Setup

100 g of E. fluctuans were utilized in the pot for the course of the 30-day trials. Thirty-liter foam containers were used for planting, after they had been cleaned with distilled water to remove any dust and soil (Plant with a 35-cm body length that is selected based on a set of characteristics, such as the absence of insects and the roots being three months old). According to the ational technical regulation on industrial wastewater in Vietnam (QCVN 40:2011/BTNMT), concentration selection tests were conducted based on the allowed threshold levels for Cd, As, Pb, Zn, and Cu in aquatic environments. Three to five times the permitted threshold was exceeded by the experimental concentration. E. fluctuans was cultivated in irrigation water that had chosen concentrations of the heavy metals Cd (II), As (III), Pb (II), Cu (II) and Zn (II). Table 1 shows the concentrations selected for performing the experiment.

Table 1 Concentration selected for experiment

Plants in distilled water were planted as a matched plant control sample.

Heavy metals (Cd, As, Pb, Zn, and Cu) in water were the analyzed parameters.

Analysis Sample

Following planting, three analyses of the heavy metal concentration in the water were conducted on the sample at 10, 20, and 30 day intervals in order to track the evolution of the amount of metal in the treated water with E. fluctuans . Through the use of inductively coupled plasma-mass spectrometry, the heavy metal content of the plants was determined to be Cd, As, Pb, Zn and Cu.

Analyzing Data

The researched data were evaluated and contrasted with the most recent tandards for Vietnam (QCVN 40:2011/BTNMT). Software from Statgraphics and Excel were used to process the data.

RESULTS AND DISCUSSIONS

Growth of E. fluctuans in heavy metals polluted water

Normally, when the concentration of a metal in water is not higher than the critical tolerance value of the plant, it does not affect the growth and height of the plant, so the biomass of the plant will not affect the plant growth. Because lant growth necessitates specific heavy metals and upkeep 16 . However, when the metal concentration in the water exceeds the limit value, the plant growth will be inhibited and manifest external states such as yellow leaves, which reduces its height and biomass 17 . Depending on the specific heavy metal involved in the process, different heavy metals have different effects on plant growth. Table 2 displays the impact of water contaminated with heavy metals on E. fluctuans plant growth. The changes in plant growth in these samples could plausibly be explained by significant differences in height growth rates. (p < 0.05).

Table 2 Effect of heavy metal polluted water on plant growth of E. fluctuans

Table 2 presents the results, which indicate that one of the key indicators for evaluating the growth of plants containing various heavy metals in the environment (Cd, As, Pb, Zn, and Cu) is height. The plants' ability to absorb nutrients determined the E. Fluctuans ’ height growth rate. The heavy metals in the water, in the following order: Cd > As, Cu > Pb > Zn, were correlated with the decreasing height. The following is a description of the growth condition:

The growth of plants in the environment with 0.5 mg/L Cd and As content. E. fluctuans showed good Cd and As absorption capacity, the plants were less likely to die, had good growth ability. There was an increase in height.

Growth of plants in a water environment with 2 mg/L of lead. E. fluctuans grew and developed well. However, after 15 days, it was observed that the plants had yellowing of leaves.

The plants in the water containing 5 mg/L of zinc showed symptoms of stunted growth; the stems and leaves had gone yellow. Ninety percent of the plants had softened leaves and stems by day 20 due to yellowing. The plants began to wilt, turn yellow, and show no signs of survival at the end of the experiment. The plants in 5 mg/L of Cu in water demonstrated that the growth of the plants was still maintained and there was growth in height. However, at the end of experimental period, many foliage had turned to yellow.

When plants are grown in water contaminated with heavy metals, their growth is reduced as a result of altered physiological and biochemical activities. This is particularly true when the heavy metal in question has no favorable effect on the growth and development of plants 18 . It is therefore clear from the height of the E. fluctuans in each pot that height growth was taken into consider. However, the various metals had varying effects on the E. fluctuans' height growth; some even wilted, perished, and failed to develop young plants. After that, the pot's biomass was drastically decreased.

Potential of E. fluctuans to accumulate heavy metals

Plant species with the potential to process heavy metals must meet at least two of the following conditions: (i) have the ability to accumulate large amounts of pollutants (100 times greater than normal plants); (ii) capable of generating large biomass under the simplest cultivation conditions 19 , 20 .

Removing potentially hazardous metals from the environment through phytoremediation is thought to be an efficient, aesthetically pleasing, economical, and environmentally benign approach. Through their roots, plants in phytoremediation gather pollutants, which they then transfer to the portion of their bodies above ground 21 , 22 . Many terms, including agro-remediation, green remediation, vegetative remediation, green technology, and botano remediation 23 , 24 are used to refer to phytoremediation.

E. fluctuans was used in a phytoremediation procedure with the aim of evaluating its efficacy in treating heavy metals. In order to track the amount of metal in water that E. fluctuans has treated over time, the sample was planted and the heavy metal concentration in the water was tested three times, after 10, 20, and 30 days. Table 3 presents the findings.

Table 3 Results of analysis of heavy metal concentrations in water over time.

According to the experimental procedure, the findings indicate that as the duration of treatment with E. fluctuans increased, the amounts of Cd, As, Pb, Zn, and Cu in the water steadily reduced. In particular, the starting levels of Cu, Zn, Pb, As, and Cd in the water were 0.5 mg/L, 0.5 mg/L, 2 mg/L, 5 mg/L, and 5 mg/L, correspondingly. The amounts of Cd, As, Pb, Zn, and Cu in the water were 0.304 mg/L, 0.392 mg/L, 1.617 mg/L, 4.087 mg/L, and 3.261 mg/L, respectively, ten days after the E. fluctuans was planted. The concentration of heavy metals (Cd, As, Pb, Zn, and Cu) dramatically dropped by day 30 of the experiment.

Growing E. fluctuans in water that contains heavy metal contamination (Cd, As, Pb, Zn, and Cu) has been shown to allow the plant to grow and flourish to a certain extent. The effects of various heavy metals on plant growth and development vary depending on the particular heavy metal involved in that process. Metals like Pb, Cd, and As have been demonstrated to negatively affect plant growth even at extremely low concentrations and to play no beneficial role in plant growth 18 . The examination of the water's content of heavy metals revealed a trend of gradually declining concentration. As a result, E. fluctuans is highly effective at cleaning water tainted with heavy metals.

Heavy m etal r emaining ercentages in w ater and r emoval e fficiency ercentage

Figure 2 displays the percentage of removal efficiency for the plants' capacity to take up heavy metals (Cd, As, Pb, Zn and Cu) in the water over time.

Figure 2 . Heavy metal removal efficiency percentage in water

Cadmium has the best absorption performance among metals. Zinc is the metal with the worst absorption performance. Over the course of the 30-day trial, E. fluctuans was able to achieve treatment efficiencies for Cd, As, Pb, Zn, and Cu of 83.4%, 60.8%, 60.4%, 40.5%, and 58.7%, respectively. These results corresponded to the beginning concentrations of 0.5 mg/L, 0.5 mg/L, 2 mg/L, 5 mg/L, and 5 mg/L. All heavy metals (Cd, As, Pb, Zn, and Cu) had cleaning rates of 40.5–83.4% for E. fluctuans by the end of the 30-day survey period. The analysis results show that after 30 days compared with the values in column B QCVN 40:2011/BTNMT, the Cd content (reaching the treatment rate of 83.40%) is within the allowable limit.

The findings demonstrate that, in comparison to the initial concentrations, after 30 days, E. fluctuans' capacity to accumulate heavy metals steadily declined with the residual heavy metal contents in the water in the order Cd < As < Pb < Cu < Zn. In particular, the residual percentage of cadmium was just 16.6%, meaning that the initial concentration was 0.1 mg/L.

According to the study, E. fluctuans has a strong capacity to absorb heavy metals in wastewater, including lead, zinc, copper, cadmium, and arsenic. The analysis's findings supported the buildup of various metals within E. fluctuans and the related decline in metal levels in the water. As has been noted in a number of other macrophyte species, E. fluctuans exhibits a high capacity for heavy metal removal from the aqueous medium. This capacity may be facilitated by their greater biomass, quick development, and capacity for metal absorption from the aqueous medium.

CONCLUSIONS

As opposed to other environmental pollutants, heavy metals are now the main cause for concern. because heavy metals can’t be destroyed by degradation. So, choosing a low-cost, environmentally friendly technology is a top priority. An additional option as a green method to treat areas affected by heavy metals is phytoremediation. Choice of the appropriate plant is the most significant feature in phytoremediation.

E. fluctuans was evaluated as a possible plant for the removal of Cd, As, Pb, Zn, and Cu based on the amounts of heavy metals in water using phytoremediation technology. E. fluctuans was able to lower the concentrations of Cd by 83.4%, As by 60.8%, Pb by 60.4%, Zn by 40.5%, and Cu by 58.7%, per the experiment results. Sixty-eight percent less heavy metal was present overall. Furthermore, E. fluctuans is a medicinal plant that has been useful in the treatment of a wide range of illnesses. These characteristics, along with its capacity for fragmentation-based asexual propagation, make it a plant that is worthwhile investigating for its potential use in both safe and environmentally friendly wastewater treatment methods that integrate natural ecosystems and phytoremediation of heavy metal-contaminated water.

CONFLICT OF INTEREST

There is no conflict of interest declared by the authors.

ACKNOWLEDGEMENTS

We acknowledge the support of time and facilities from Thu Dau Mot University for this study. A.T.H thank the Department of Environmental Engineering, Dayeh University, Taiwan for favorable conditions for me to research in Taiwan.

AUTHOR CONTRIBUTIONS

(A.T.H) Original draft writing, writing reviews, editing, conceptualization, methodology, research, and experimentation. The conceptualization, review, and supervision were completed by (TMD).