Heavy metals, occurrence and toxicity for plants: a review

Environmental Chemistry Letters (Impact Factor: 1.91). 09/2010; 8(3):199-216. DOI: 10.1007/s10311-010-0297-8

ABSTRACT Metal contamination issues are becoming increasingly common in India and elsewhere, with many documented cases of metal toxicity
in mining industries, foundries, smelters, coal-burning power plants and agriculture. Heavy metals, such as cadmium, copper,
lead, chromium and mercury are major environmental pollutants, particularly in areas with high anthropogenic pressure. Heavy
metal accumulation in soils is of concern in agricultural production due to the adverse effects on food safety and marketability,
crop growth due to phytotoxicity, and environmental health of soil organisms. The influence of plants and their metabolic
activities affects the geological and biological redistribution of heavy metals through pollution of the air, water and soil.
This article details the range of heavy metals, their occurrence and toxicity for plants. Metal toxicity has high impact and
relevance to plants and consequently it affects the ecosystem, where the plants form an integral component. Plants growing
in metal-polluted sites exhibit altered metabolism, growth reduction, lower biomass production and metal accumulation. Various
physiological and biochemical processes in plants are affected by metals. The contemporary investigations into toxicity and
tolerance in metal-stressed plants are prompted by the growing metal pollution in the environment. A few metals, including
copper, manganese, cobalt, zinc and chromium are, however, essential to plant metabolism in trace amounts. It is only when
metals are present in bioavailable forms and at excessive levels, they have the potential to become toxic to plants. This
review focuses mainly on zinc, cadmium, copper, mercury, chromium, lead, arsenic, cobalt, nickel, manganese and iron.

KeywordsHeavy metals-Environment-Toxic effects-Plants-Anthropogenic activities

  • Source
    Bulletin UASVM Horticulture. 01/2013; 70(1):8.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Many crop plants are exposed to heavy metals and other metals that may intoxicate the crop plants themselves or consumers of the plants. The rhizotoxicity of heavy metals is influenced strongly by the root cell plasma membrane (PM) surface's electrical potential (ψ0). The usually negative ψ0 is created by negatively charged constituents of the PM. Cations in the rooting medium are attracted to the PM surface and anions are repelled. Addition of ameliorating cations (e.g., Ca2+ and Mg2+) to the rooting medium reduces the effectiveness of cationic toxicants (e.g., Cu2+ and Pb2+) and increases the effectiveness of anionic toxicants (e.g., SeO42- and H2AsO4-). Root growth responses to ions are better correlated with ion activities at PM surfaces ({IZ}0) than with activities in the bulk-phase medium ({IZ}b) (IZ denotes an ion with charge Z). Therefore, electrostatic effects play a role in heavy metal toxicity that may exceed the role of site-specific competition between toxicants and ameliorants. Furthermore, ψ0 controls the transport of ions across the PM by influencing both {IZ}0 and the electrical potential difference across the PM from the outer surface to the inner surface (Em,surf). Em,surf is a component of the driving force for ion fluxes across the PM and controls ion-channel voltage gating. Incorporation of {IZ}0 and Em,surf into quantitative models for root metal toxicity and uptake improves risk assessments of toxic metals in the environment. These risk assessments will improve further with future research on the application of electrostatic theory to heavy metal phytotoxicity in natural soils and aquatic environments.
    International Journal of Molecular Sciences 12/2014; 15(12):22661-22677. · 2.46 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Graphene manganese ferrite (MnFe2O4-G) composite was prepared by a solvothermal process. The as-prepared graphene manganese ferrite composite was tested for the adsorption of lead (Pb (II)) and cadmium (Cd(II)) ions by analytical methods under diverse experimental parameters. With respect to contact time measurements, the adsorption of Pb and Cd ions increased and reached equilibrium within 120 and 180 mins at 37 °C with a maximum adsorption at pH 5 and 7 respectively. The Langmuir model correlates to the experimental data showing an adsorption capacity of 100 for Pb (II) and 76.90 mgg−1 for Cd (II) ions. Thermodynamic studies revealed that the adsorption of Pb and Cd ions onto MnFe2O4-G was spontaneous, exothermic and feasible in the range of 27°- 47 °C. Cytotoxicity behavior of graphene against bacterial cell membrane is well known. To better understand its antimicrobial mechanism, the antibacterial activity of graphene and MnFe2O4-G nanocomposite was compared. Under similar concentration and incubation conditions, nanocomposite MnFe2O4-G dispersion showed the highest antibacterial activity of 82%, as compared to graphene showing 37% cell loss. Results showed that the prepared composite possess good adsorption efficiency and thus could be considered as an excellent material for removal of toxic heavy metal ions as explained by adsorption isotherm. Hence MnFe2O4-G can be used as an adsorbent as well as an antimicrobial agent.
    Applied Surface Science 02/2015; 327:27. · 2.54 Impact Factor


Available from
Jun 2, 2014