What are heavy metals pdf

Many researchers believe that this phenomenon will provide an economical alternative for removing toxic heavy metals from industrial wastewater and aid in environmental remediation. Schiewer et. The heavy metal removal capacity between the rice hull and saw dust was studied and compared by Asadi et.

Biosorption and desorption studies on chromium VI by novel biosorbents of raw rutin and rutin resin were studied by Fathy et. The hydroxyl, carboxyl and carbonyl groups were the main functional groups attached to the resin for the chromium removal from waste water. Utilizing chemically modified agricultural waste okra biomass for removal of toxic heavy metal ions from aqueous solution was put forward by Singh et.

A comparison of low-cost biosorbents such as seaweed Ascophyllum nodosum , sawdust and reed plant Phragmites australis root demonstrated that seaweed has the highest adsorption capacity out of three for cadmium whereas sawdust showed a very good adsorption capacity for lead Akunwa et.

The removal of heavy metals through biosorption depends on the functional group attached to the biosorbents as different groups helps in the biosorption of different mentals like silica group shows more affinity towards cadminum, zinc and copper; hydroxyl group shows more affinity towards chrominum and nitro group shows more affinity towards lead. No work is done in scaling up the process and making it available for the industry.

The researchers have just concentrated on whether that material is applicable for heavy metal removal and if yes then they have calculated the capacity to remove the heavy metal. No detail study is done on desorption process and disposal of adsorbent used for heavy metals removal. As many of them have claimed that adsorbents such as industrial waste material, agricultural and biological waste also show good adsorption capacity for the removal of heavy metals and are also easily available at low cost but requires a pretreatment and high handling cost for sludge disposal.

It is seen that use of low-cost adsorbents is the keen interest of research for heavy metals removal, more study is required to focus on reducing the cost of pretreatment, regeneration and disposal.

Finally, technical applicability, plant simplicity and cost- effectiveness are the key factors that play major roles in the selection of the most suitable adsorbent for the process. References 1. Bernard E. O, Heavy metals removal from industrial wastewater by activated carbon prepared from coconut shell, Research Journal of Chemical Sciences 3 8 : 3 — 9 2.

Barakat, New trends in removing heavy metals from industrial wastewater, Arabian Journal of Chemistry 4 : — 5. Sandhya Babel, Tonni Agustiono Kurniawan, Low-cost adsorbents for heavy metals uptake from contaminated water: a review, Journal of Hazardous Materials B — 6. Ali Sdiri, Teruo Higashi, Fakher Jamoussi, Samir Bouaziz, Effects of impurities on the removal of heavy metals by natural limestones in aqueous systems, Journal of Environmental Management 93 1 : — 7.

Shavandi, Z. Haddadian, M. Ismail, N. Abdullah, Z. Mehmet Emin Argun, Sukru Dursun, A new approach to modification of natural adsorbent for heavy metal adsorption, Bioresource Technology 99 7 : — Tarek S. Jamil, Hanan S. Ibrahim, I.

Abd El-Maksoud, S. El-Wakeel, Application of zeolite prepared from Egyptian kaolin for removal of heavy metals: I. Optimum conditions, Desalination : 34—40 Tamer M. Belgin Bayat, Comparative study of adsorption properties of Turkish fly ashes I. Ricou-Hoeffer, I. Lecuyer and P. Le Cloirec, Experimental design methodology applied to adsorption of metallic ions onto fly ash, Water Research 35 4 : — Namasivayam, D.

Sangeetha, R. Gunasekaran, Removal of anions, heavy metals, organics and dyes from water by adsorption onto a new activated carbon from Jatropha husk, an Agro-Industrial solid waste, Process Safety and Environmental Protection 85 2 : — Suthipong Sthiannopkao, Siranee Sreesai, Utilization of pulp and paper industrial wastes to remove heavy metals from metal finishing wastewater, Journal of Environmental Management 90 11 : Download Download PDF.

Translate PDF. Avian tissues are usefully used indicator because the concentration level of heavy metals in their tissues reflects their exposure and may also be indicative for trend of the past exposure.

Initially, internal organs were collected after sacrificing a live bird, but more recently the demand of noninvasive technique leads to the use of feathers, eggs, and feces for biomonitoring of heavy metals Burger Feathers and eggs are very special for metal accumulation studies not only because they can be collected without affecting the life of a bird but also for they have certain important information which is not possible to acquire otherwise Dauwe et al.

The use of feathers and eggs for heavy metal monitoring in soil has their own respective limitations, but eggs have certain several advantages over the other noninvasive biomonitoring matrices because they are easier to collect and can be preserved for a long time.

In addition, eggs are relevant to a specific portion of the population, called as egg-laying female birds; they are formed during a specific duration of the life of a female and hence proven as a very good indicator for local exposure.

Prior to egg laying, females of all the bird species from temperate and M. Sherameti, A. Varma eds. Hashmi et al. Unlike feathers, the composition of an egg is advantageous because its composition is highly consistent which does not change with size, age, or the position of the body. Eggs have been widely used for many of the recent biomonitoring studies, and it has been a proven fact that collecting a single egg in favorable circumstance has produced negligible effects on population parameters of the species Furness Soil is an important medium to support the life on earth.

It is an essential part of biosphere which provides space for animal and plant anchorage and growth and regulates the cycles of nutrients and water. Since the advent of industrial revolution, the concentration of heavy metals increases alarmingly in the soil.

As a result of rampant discharge of agricultural and industrial waste, the concentration level of heavy metals like most of the pollutants suddenly touched to the threatening threshold. Municipal waste, ore smelting, and the use of pesticide and fertilizers are the major anthropogenic sources through which toxic heavy metals are intro- duced in the soil Meli et al.

Soil is the ultimate medium which receives heavy metals from different sources and deposits them for a long time. Being the largest supporting medium for heavy metal deposition, soil and sediments serve as an archive and reservoir for metal deposition and their subse- quent dissemination in plants and animal body parts through their feed. Elevated concentration of heavy metals in soil greatly affects the capability of the soil to sustain its biological productivity, regulate the local environment, and provide the best condition for the growth of animals and plants and betterment of human health.

Heavy metals present in soil are taken by plants and animals through absorption and ingestion, respectively. Birds being the agile group of vertebrates receive metals during their lifetime exposure to soil. The concentration level in eggs of a species is a very good indicator for local exposure to soil. This is because of the reason that an egg is the only development in birds which is produced during a particular period of time by an egg-laying female fraction of a population.

For breeding, birds are either sedentary remain in their same habitat or migratory migrate toward their breeding grounds for breeding. Burger and Gochfeld reported that the concentration of metals in eggs represents the circulation level of respective metals in the blood which in turn reflects the recent exposure. Similarly, Burger said that eggs are the most vulnerable part to be affected with heavy metals and it exhibits the local exposure of the adult female which has laid them.

The concentration of metals such as Pb and Cd concentration was found to be correlated in the soil and egg which suggests that soil is an important source for these elements Waegeneers et al.

In this way, an egg has been proven as a very useful biomonitoring tool for heavy metal contamination in soil. The concentration of heavy metals in eggs in relation to soil may be affected by several factors. As this relation is much dependent on food of the organism, difference in the food chain may exist. It also depends on the dietary preferences of the species during breeding period. Interspecies differences and spatiotemporal differences were recorded in several studies Akearok et al.

The difference between the eggshell and egg contents also gives useful information. Usually, for toxic trace metals such as Pb, Cd, Se, and Hg, the eggshell has been suggested to be a better indicator, while egg contents could be used as a best indicator for essential elements such as Fe, Mn, Zn, etc.

Dauwe et al. Moreover, it is suggested that data for egg metals for the same species should be collected for a period of consecutive years to identify the addition or deletion of any point or nonpoint pollution source and also to record the past trends of exposure Burger and Gochfeld This chapter relates the metal concentra- tion in eggs which is indicating the pollution level at different habitats, factors which affect the soil to egg metal ratio and the inexplicability of egg to soil metal relation.

Further, this chapter also discusses the pros and cons for an egg as a biomonitoring tool for metal contamination and its scope for future biomonitoring research. In terrestrial ecosystems, the ambient environment is usually soil Burger et al. Once metals get into soil or sediment, they have long residence times before they are eluted to other compartments. Acidity has a marked effect on the solubility of metals in soils and water.

The mobility of metals in soils is dictated largely by the clay contents, amount of organic matter, and pH. In water, the solubility of metals is strongly pH dependent. Unlike organochlorides another known family of pollutants , which are distrib- uted widely among body tissues, largely in relation to their lipid contents, heavy metals tend to be held in one particular tissue at much higher levels than the others. The site specificity of metals has an important influence on the choice of tissue for monitoring studies.

For example, although females can excrete mercury into eggs, the amount they shed in this way is usually small compared to the amount put into feathers during molting Honda et al.

There are several different approaches for measuring bioavailability. In vivo tests use an animal to measure absolute bioavailability and toxicity. In vitro tests are performed outside the organism Furman et al. Chemical use is increasing in our envi- ronment and may pose a threat to some species and populations.

The levels of many chemicals have been elevated in aquatic ecosystems wetland, islands, marine land, and coastal areas and terrestrial ecosystems agriculture, forest, rural and urban by using eggs Table 7. Hence, terrestrial ecosystems are major hotspot for the chemical deposition from anthropogenic activities agriculture and industrial and natural processes.

These anthropogenic activities and natural pro- cesses have not only affected terrestrial ecosystem services but also other living things human, animals, etc. Several research articles reported eggs as a suitable bioindicator of agricultural areas Hashmi et al. Table 7. Aquatic ecosystems such as wetlands, islands, marine lands, and coastal areas provide breeding habitats for egrets, herons, and waterfowls and receive untreated effluents from agriculture and industries and cities from point and nonpoint sources of pollution.

Hence, wetlands, islands, marine lands, and coastal areas act as a depository reservoir of organic as well as inorganic pollutants. Species that forage in aquatic environments are particularly vulnerable because of the potential for the rapid movement of contaminants in water, com- pared to the movement in terrestrial environments, and because chemicals can be stored in sediments in intertidal environments, providing a pool for years to come.

Organisms that live in these estuarine systems can bioaccumulate organic and certain inorganic substances over time and are at risk from both lethal and sublethal effects, as their body burdens increase. Several studies used eggs as a biomonitor of heavy metal contamination in the soil and sediments of wetland ecosystems Shahbaz et al. However, most of the published literature focused on the island and wetland ecosystems to monitor the heavy metal contamination by using eggs than the other ecosystems.

Several factors such as age and health of the female, diet preferences during breeding season, taxonomic affiliation, and the trophic level of the species and metal concentration level in the surrounding environment either singly or synergistically influence the overall metal burden in egg of different bird species. Heavy metal accumulation in eggs of different species largely depends upon the metal availabil- ity, metal intake, and physiological mechanisms for metal circulation, accumula- tion in the parts of the body, regulation, and subsequent excretion.

Differences of heavy metal concentrations in the eggs of different species have been reported in several studies Akearok et al. There are several possible reasons for interspecific metal variation in eggs. In this way, an egg has been proven as a very useful biomonitoring tool for heavy metal contamination in soil. The concentration of heavy metals in eggs in relation to soil may be affected by several factors. As this relation is much dependent on food of the organism, difference in the food chain may exist.

It also depends on the dietary preferences of the species during breeding period. Interspecies differences and spatiotemporal differences were recorded in several studies Akearok et al.

The difference between the eggshell and egg contents also gives useful information. Usually, for toxic trace metals such as Pb, Cd, Se, and Hg, the eggshell has been suggested to be a better indicator, while egg contents could be used as a best indicator for essential elements such as Fe, Mn, Zn, etc. Dauwe et al. Moreover, it is suggested that data for egg metals for the same species should be collected for a period of consecutive years to identify the addition or deletion of any point or nonpoint pollution source and also to record the past trends of exposure Burger and Gochfeld This chapter relates the metal concentra- tion in eggs which is indicating the pollution level at different habitats, factors which affect the soil to egg metal ratio and the inexplicability of egg to soil metal relation.

Further, this chapter also discusses the pros and cons for an egg as a biomonitoring tool for metal contamination and its scope for future biomonitoring research. In terrestrial ecosystems, the ambient environment is usually soil Burger et al. Once metals get into soil or sediment, they have long residence times before they are eluted to other compartments.

Acidity has a marked effect on the solubility of metals in soils and water. The mobility of metals in soils is dictated largely by the clay contents, amount of organic matter, and pH.

In water, the solubility of metals is strongly pH dependent. Unlike organochlorides another known family of pollutants , which are distrib- uted widely among body tissues, largely in relation to their lipid contents, heavy metals tend to be held in one particular tissue at much higher levels than the others. The site specificity of metals has an important influence on the choice of tissue for monitoring studies.

For example, although females can excrete mercury into eggs, the amount they shed in this way is usually small compared to the amount put into feathers during molting Honda et al. There are several different approaches for measuring bioavailability. In vivo tests use an animal to measure absolute bioavailability and toxicity. In vitro tests are performed outside the organism Furman et al. Chemical use is increasing in our envi- ronment and may pose a threat to some species and populations.

The levels of many chemicals have been elevated in aquatic ecosystems wetland, islands, marine land, and coastal areas and terrestrial ecosystems agriculture, forest, rural and urban by using eggs Table 7. Hence, terrestrial ecosystems are major hotspot for the chemical deposition from anthropogenic activities agriculture and industrial and natural processes.

These anthropogenic activities and natural pro- cesses have not only affected terrestrial ecosystem services but also other living things human, animals, etc. Several research articles reported eggs as a suitable bioindicator of agricultural areas Hashmi et al. Table 7. Aquatic ecosystems such as wetlands, islands, marine lands, and coastal areas provide breeding habitats for egrets, herons, and waterfowls and receive untreated effluents from agriculture and industries and cities from point and nonpoint sources of pollution.

Hence, wetlands, islands, marine lands, and coastal areas act as a depository reservoir of organic as well as inorganic pollutants. Species that forage in aquatic environments are particularly vulnerable because of the potential for the rapid movement of contaminants in water, com- pared to the movement in terrestrial environments, and because chemicals can be stored in sediments in intertidal environments, providing a pool for years to come.

Organisms that live in these estuarine systems can bioaccumulate organic and certain inorganic substances over time and are at risk from both lethal and sublethal effects, as their body burdens increase. Several studies used eggs as a biomonitor of heavy metal contamination in the soil and sediments of wetland ecosystems Shahbaz et al. However, most of the published literature focused on the island and wetland ecosystems to monitor the heavy metal contamination by using eggs than the other ecosystems.

Several factors such as age and health of the female, diet preferences during breeding season, taxonomic affiliation, and the trophic level of the species and metal concentration level in the surrounding environment either singly or synergistically influence the overall metal burden in egg of different bird species.

Heavy metal accumulation in eggs of different species largely depends upon the metal availabil- ity, metal intake, and physiological mechanisms for metal circulation, accumula- tion in the parts of the body, regulation, and subsequent excretion. Differences of heavy metal concentrations in the eggs of different species have been reported in several studies Akearok et al.

There are several possible reasons for interspecific metal variation in eggs. A study reported by Boncompagni et al. The next question in this regard may be that why eggs of different species exhibit different concentrations of metals inhabiting the same location? There is no straightforward answer yet being provided through research.

But it is described by the physiological mechanism differences for the circulation, regulation, excretion, and replenishment of metals for different species. In general, one can say that both of the abovementioned factors, i. Shahbaz et al. They also deduced that unlike feathers, the concentration of heavy metals in eggs is more influenced by the environmental condition and food items.

Similarly, elevated concentrations of Pb and Cd in the diet and sediments were found to be directly associated with the higher concentra- tion of these metals in herons of Korea Kim et al. The higher concentration of strontium in the eggshell of passerine birds from Arizona was probably associ- ated with the higher deposition of Sr in the surrounding of the nesting sites of these birds.

These passerine birds feed on certain invertebrates and insects which were associated with the recycling of Sr in the soil Mora While studying the accumulation of Hg in different species, Burger found that larger fish-eating birds tend to accumulate more metals in their eggs when compared to small fish eaters. Similarly, in comparison with carnivores, omnivores and invertebrate-eating species accumulate lower metal accumulation in their eggs and showed that for birds, certain metal concentration increases with the increase in the trophic position.

But this is not true for all the metals nor for all species. Being higher on the food web, the concentration of Hg in the eggs of common tern Sterna hirundo was found twice than those of duck species Akearok et al. Boncompagni et al.

So the birds which feed on the prey which largely relies on metal-rich soil for their food should have more metal concentration in their eggs. In general, one can say that the concentration level of heavy metals increases with the increase in the trophic position of the species, but one has to keep in mind the respective food chain and food web to get a meaningful result.

Temporal variation in the egg metal level provides information that can be useful for understanding the sudden shift of metals which in turn can be used to find any new addition in the metal pollution source Burger and Gochfeld It is usually recommended to collect year-wise data for the same species for consecutive years to get a better understanding about the trends of metal accumulation.

Significant differences in the concentration of heavy metals such as Pb, Cd, Se, and Hg were recorded in eggs of herring gulls Larus argentatus between the years and But the concentration level of metals in eggs rarely remains consistent for any metals between the years because of the changing metal pollution level for the location which the female is visiting for foraging prior to egg laying Burger Furthermore, seasonal variation in the availability of heavy metals is obvious, so the exposure varies between different species and seasons.

This is because the onset of breeding period is not the same for all the species, so the female of the different species may be exposed to the varying levels of heavy metals and hence accumulate different levels of metals in their egg. Seasonal bioavailability of heavy metals in soil is largely based on soil characteristics and local environmental condition and weather attributes.

Besides inter-clutch variation in metal concentration, intra- clutch variation has also been observed for several metals. Custer et al. Usually, the early laid egg has higher concentration of metals than later ones. Conversely, the concentration of several trace metals varied significantly between the home-produced chicken eggs in autumn and spring, but this temporal discrep- ancy of metals has not solely depended upon the concentration of these metals in soil Waegeneers et al.

Similarly, temporal trends were recorded as spatial and temporal variations of Hg in the egg contents of gannet Morus bassanus between the years and from Bass Rock North Sea and Ailsa Craig eastern Atlantic Pereira et al.