Research article
Phytoremediation capacity, growth and physiological responses of Crambe abyssinica Hochst on soil contaminated with Cd and Pb

https://doi.org/10.1016/j.jenvman.2020.110342Get rights and content

Highlights

  • Crambe plants have great potential for phytoextraction of cadmium and phytostabilization for lead.

  • Although the photosynthetic system is hampered by contamination, crambe removed significant amounts of metals from the soil.

  • Pb is accumulated in roots, while Cd is distributed among plant tissues, especially in aerial part.

Abstract

The search for vegetal species regarding effectiveness in the phytoremediation of soils is of great importance, mainly in function of the great environmental problems, such as soil contamination with heavy metals, the necessity of producing more food, among others that mankind face today. This work aimed (i) to evaluate phytoremediation capacity of Crambe abyssinica Hochst and its growth in soil artificially contaminated with Cd and Pb, and (ii) to evaluate the possible impacts of crambe cultivation in contaminated soil conditions, in order to evaluate, to test, and to question the Brazilian CONAMA 420, providing important information that can be useful for governmental and environmental purposes. Two simultaneous experiments were developed, one for each metal. The soils were contaminated with salts of CdCl2 and PbCl2H2O in five doses based on the investigation values (IV) of CONAMA Resolution 420, resulting in 0; 1.5; 3; 9 and 30 mg kg−1 for Cd and 33; 90; 180; 540 and 1800 mg kg−1 for Pb. Gaseous exchange, development, nutritional composition and production of plant components, as well as phytoavailability of metals, were evaluated. The contamination with metals reduced photosynthesis, increased breathing as well as leading to a negative effect on the mineral nutrition and productivity in general; Plants cultivated in soil with Cd presented higher phytoavailability when compared to those cultivated in the Pb conditions, being found metals in all parts of the crambe plants from 1.5 mg kg− 1 of Cd in the soil; and Pb was retained only in roots, not being translocated in the plant. Cd showed higher phytoavailability, being found in all parts of the plant and Pb was retained only in the roots. Cd showed a higher phytoavailability when compared to Pb, also being found in all parts of crambe plants from dose 1.5 mg kg-1 of Cd in soil, which is an environmental problem, since in these concentrations the cultivation of crops is allowed by Brazilian legislation CONAMA 420.

Introduction

Toxic metals are polluting elements that have adverse effects on ecosystems, causing physical and chemical changes to water, soil and air, in addition to promoting the decrease of soil quality and the fauna and flora mortality, thus harming human health (Gonçalves Jr. et al., 2014; Lago-Vila et al., 2019).

Among these metals, Cd and Pb are between the most troubling, due to the properties of high toxicity, high cumulative values and low biodegradability (Gupta, 2016).

According to Bassegio et al. (2019), once these elements are in the soil, they can lead to denaturation of proteins and oxidative stress in plants, resulting in damage to the membranes, reduction in enzyme activity and photosynthesis, chlorosis, among many other metabolic changes, in addition to changes in the mineral nutrition and the water balance, by modifying its hormonal state.

Furthermore, the contaminated food can be one of the main sources of Cd and Pb to humans, since there is the risk of being deposited in different plant tissues, including grains (Yu et al., 2019). In humans, the main target of these metals toxicity is the nervous system, not only in adults but also in children, and that exposure, even when small, leads to problems of blood pressure, especially in middle-aged and older people, anemia; and when in high levels, these metals may seriously damage the brain and kidneys, and may even lead to death (CDCP - Centers for Disease Control and Prevention, 2014).

According to Amine et al. (2018), the use of fossil fuels also contributes to the contamination of soil by Pb, because this metal was used in many countries to increase the levels of octane, releasing high levels of Pb into the environment.

The crambe (Crambe abyssinica) cultivation has been presented as an alternative, since its seed has 38% oil, which has as main compound the erucic acid, representing 57% of the oil content, component that allows to use it beyond the biodiesel production, in different industrial products such as cosmetics, lubricants, among others (Stolarski et al., 2019).

The use of these crops can improve environmental conditions in these areas, in addition to the opportunity to generate their products, constituting income sources for these sites (Bassegio et al., 2019), or even waste that can be used in the remediation of other environments (Gonçalves Jr. et al., 2013).

Consequently, the crambe crop with a dual purpose can consist of an option to remediate these environments where, in addition to performing the phytoremediation of the metals from soil (Souza et al., 2014), the extraction of its oil generates a new waste, what could be considered a problem for the environment, but the crambe meal exhibit an excellent potential for the remediation of water bodies (Rubio et al., 2013), acting as a natural adsorbent water contaminated with Cd and Pb (Gonçalves Jr. et al., 2013).

Considering all that was mentioned, the main problem occurs when these contaminated areas are used for agronomic purposes, mainly because the environmental legislation of Brazil, in CONAMA 420 (BRAZIL, 2009) allow the use of contaminated areas with metal for production of food. It is worth of mention that in many other countries, the same problem occurs, where considerable levels of metals in soils do not restrict its use for agronomic purposes (Gonçalves Jr. et al., 2014).

Therefore, this study aimed (i) to evaluate the Crambe abyssinica Hochst development in contaminated soils with Cd and Pb as well as its phytoremediation capacity, phytoavailability and distribution of these toxic metals in plant parts, (ii) to evaluate the possible impacts of crambe cultivation in stress situations, such as toxic metals in soil, by means of artificial contamination of soil parcels (in controlled environments), in order to evaluate, to test, and to question the Brazilian CONAMA 420, providing important information that can be useful for governmental and environmental purposes.

Section snippets

Material and methods

Two experiments were conducted simultaneously in a greenhouse belonging to the State University of Western Paraná, located at longitude 54° 22′ W, latitude 24° 46′ S and average altitude of 420 m, with one experiment for each metal (Cd and Pb).

The soil used in the experiments, according to the classification of the Brazilian Agricultural Research Corporation (EMBRAPA) (Santos et al., 2013) was a “LATOSSOLO VERMELHO Eutroférrico” and its correspondent according to USDA (USDA, 2015) “Red

Results

The crambe plants showed development both in its canopy height as in stem diameter, having significant differences over time. However, in relation to the contamination levels it is possible to visualize differences in the both canopy height cases (Fig. 1a and b), as to stem diameter (Fig. 1c and d), the obtained values decrease as the levels of soil contamination increase, thus with the highest values for plants grown in non-contaminated soil and the lowest values for plants cultivated in soils

Discussion

The height reduction and number of tillers (Fig. 1) can be justified by the effects that these metals have on the vital processes of plants, thereby reducing their development and consequently leading to lower diameter height. This can explain the differences of 56.0 and 21.0 cm height as well as 2.8 and 2.5 mm diameter to Cd and Pb, respectively (Bhardwaj et al., 2009).

The obtained results in Table S1, corroborate with several authors as indicate that the presence of metals reduces the

Conclusions

Soil contamination with Cd and Pb reduced photosynthesis, increased crambe breathing and had a negative influence in mineral nutrition and crambe yield.

Cd showed a higher phytoavailability when compared to Pb, also being found in all parts of crambe plants from 1.5 mg kg−1 of Cd in the soil, which is an environmental problem, since in these concentrations the cultivation of crops is allowed by Brazilian legislation CONAMA 420.

Pb was retained only in the roots not being translocated to the

Autor's statement

Affonso Celso Gonçalves Jr. The main author was responsible for the conceptualization of the whole experiment and project. Dr. Gonçalves Jr. was the Principal Investigator of this research, the one who wrote the first draft of the project and was the responsible for the association with the founding agency. Besides, was involved in the methodology definition and validation of the results. At last, the first author is also the correspondent author of the manuscript, in function of its major

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

To the CNPq for the financial support and Scientific Productivity Fellowship and also to CAPES, since this study was financed in part by the Coordination for the Improvement of Higher Education Personnel, with the Finance Code 001.

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