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Perspectives of Heavy Metals as Toxicant: a Review

M. R. R. Miah
Department of Entomology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh

S. M. K. Alam
Pathology Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

N. K. Dutta
Entomology Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

A. K. M. Z. Rahman
Entomology Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

Abstract/ Executive Summary:

The ecotoxicity or toxic effects of heavy metals has been studied mainly in a few groups of soil animals notably insects, earthworms, nematodes and bacteria. Heavy metals are dispersed into the environment especially to the soil environment from different sources either anthropogenic or natural sources and cause environmental pollution; eventually exert harmful effects to animal and human beings. Metal toxicity affects soil organism both directly and indirectly. Direct toxic effects are associated with uptake of free acidic water from the environment by some soil animals and with consumption of polluted food by others. The toxicity of metals depends on the bioavailability of metals and the bioavailability depends on several factors such as pH, temperature, organic matter, soil microbial population, soil texture etc. The metal toxicity to an organism is exhibited through abnormal growth, affected reproduction and mortality and emitting less light in presence of suitable biosensors. Metals may be toxic at both lethal and sub-lethal levels. The toxicity of metals singly or in combination (mixture) may vary. The toxicity mixtures of certain metals to different organisms could be additive, synergistic or antagonistic depending on the levels of organisms.

Keywords: Heavy Metals and Toxicant

Location:

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Contamination of soil

Objectives:

To identify the heavy metals into the environment especially to the soil environment from different sources either anthropogenic or natural sources.

Methodology:

Heavy Metals and Their Sources: Heavy metals are those metals with a specific gravity greater than 5. The term heavy metals is generally used by the ecotoxicologists to refer to those metals that have been proven to cause environmental problems and the important ones are Cd, Hg, Zn, Cu, Ni, Cr, Pb, Co, V, Ti, Fe, Mn, Ag, Sn. Sources of heavy metal in the environment are both natural and anthropogenic sources. Natural Sources of heavy metals includes the atmosphere, agricultural soils, other natural such as volcanic eruptions, forest fires and vapour-phase outgasing of relatively volatile compounds from water and terrestrial receptors are considered as sources of heavy metals. For the selection of heavy metals and their sources considering these way such as Important consequences of metal pollution and Bioavailability of heavy metals, Ecotoxicity of heavy metals: Toxicity of metals to invertebrates, Toxicity to Insects, Toxicity to earthworms, Growth and reproduction, Mortality, Toxicity of metals to microorganisms, Toxicity of metals to nematodes, Nematode community and their activities, Toxicity of metals to Bacteria, Effect on specific bacterial groups and Metal tolerance or resistance and Toxicity of mixtures of metals:

Source of Information: The Agriculturists 2( 1): 43-60 (2004); A Scientific Journal of Krishi Foundation.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It can be concluded that the toxicity of heavy metal to different organisms vary depending on organisms, concentrations of metals and condition (singly or mixture) and sometimes this toxicity might be used for the betterment of agriculture.

Knowledge Management: Journal