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4 Mining, Milling Processes and Industrial Wastes

4 Mining, Milling Processes and Industrial Wastes

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Soil Amendments for Heavy Metal Immobilization Using Different Crops



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The transition metals, lanthanoids, actinoids and metalloids, all have high density

and are categorized as heavy metals. Their on-site disposal severely affects the

growth and development of different plant organs. Similarly, petroleum gas leaks,

leaded paint manufacturing, and leather processing industries top the list as a risk

for living objects. Generally very high concentrations of lead and zinc are determined in the plants and soils adjacent to smelting works (El-Shahawi et al. 2014).



3.5



Airborne Sources of Fly Ash



Airborne sources for heavy metals include stack or duct emissions of air, gas, or

vapors from storage areas or waste piles. These are generally released as particulates. Many metals can volatilize at high-temperatures forexample; arsenic, cadmium and lead. They get distributed by natural air currents and on condensation

precipitate on large areas, which lead to soil and air pollution at the sites quite

away from the source. The major source of lead is combustion of petrol, containing

tetraethyl lead; zinc and cadmium are generally added to the soils adjacent to

roads, the sources being tyres and lubricant oils. Luo et al. (2009) has reported in

his work conducted in China that, 43–85% of pollutants like lead, arsenic, zinc,

mercury and cadmium can be accepted as the major pollution contributors from the

industry.



4



Global Overview of Soil Contamination



Approximately 1,400,000 land resources have been recorded to contain heavy metals in the Western Europe; of this total area, a very large number of sites are recorded

as polluted (McGrath et al. 2001). There are 400,000 polluted sites in Germany, Uk,

Denmark, Spain, Italy, Netherlands and Finland, whereas in Sweden, France,

Hungary, Slovakia and Austria the number of contaminated land sites is reported to

lie around 200,000. Nearly 10, 000 contaminated areas have been recorded from

Greece and Poland and less than this number in Ireland and Portugal (Perez 2012).

Recently, the Ministry of Environmental Protection (MEP) and the Ministry of

Land and Resources of the People’s Republic of China have issued a joint report on

the current status of soil contamination in China. According to the report, soils in

some areas, especially those surrounding mining and industrial activities are seriously contaminated, while the quality of farmland soils is also of particular concern.

The report is based on extensive surveys of soils conducted between 2005 and 2013,

covering more than 70% of China’s land area. According to the report approximately 16.1% of the farmland soils in the country are rich in heavy metals, and their

level has exceeded the environmental quality standard set by the MEP; for agricultural soils the percentage of exceedance is reported as 19.4% (equivalent to nearly

26 million ha; assuming that that the area is proportional to the number of survey



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samples). Contamination by heavy metals and metalloids accounts for 82.4% of the

soils, which are classified as being contaminated and the rest of the contamination

comes from the organic contaminants. Among the heavy metals and metalloids,

cadmium ranks as the first in the percentage of soil samples (7.0 %) exceeding the

MEP limit (MEP and MRL, PRC 2015). One-sixth of the total agricultural lands in

China is suffering from heavy metal pollution, and approximately 40% is reported

to be disturbed by erosive activities and rapid deforestation (Liu et al. 2005; Hang

Zhou et al. 2014). It The calculations have shown that cultivated agricultural lands

irrigated with polluted water in China comes to about 7.3% of the total irrigated

cropland. There is no control over the quantity of contaminated water (Luo et al.

2009). Similarly paddy fields in Korea are reported to suffer from pollution of heavy

metals like cadmium, lead, and zinc amounting to 0.11 mg kg − 1. Likewise, concentration in Japanese paddy fields has been assessed to lie around 22.9 mg kg−1,

75.9 mg kg−1 and 3.71 mg kg−1.

Crude open dumping of sewage sludge and industrial effluents in the close proximity is regular practice in the countries like. Pakistan, India, Bangladesh and Sri

Lanka. There are no sufficient number of treatment plants for the final disposal of

hazardous hospital, municipal and industrial wastes, as a result crude open dumping

in fresh water bodies is widespread (Lone et al. 2008). Approximately 600, 000

Brownfield sites in America show heavy metal pollution. The most of the soil and

land contamination in America can be attributed to the crude disposal of waste from

poultry farms. The number of chicken broilers has crossed 200 million in 2007,

unchecked chicken waste disposal has resulted in an alarming increase in soil and

water contamination in USA. In Pacific Islands (Cook Islands), about 9000 cubic

meters of solid waste are dumped in the close proximity of land areas and fresh

water bodies, resulting in massive pollution. If tourism keeps on increasing at the

current pace, pollution is expected to increase 10-times in the coastal areas (Convard

et al. 2005). The use of fertilizers, pesticides, herbicides, tourism and fossil fuel

combustion in the Kiribati, Fiji, Nauru, Niue and Marshall Islands release an excessive quantity of solid wastes which are dumped unchecked into the oceans. On the

other hand the polluted irrigation waters are continuously used for irrigating croplands (Convard et al. 2005).



5



Commonly Used Extraction Techniques



The heavy metals in the soil may exist in different forms and show different ways of

bindings. In uncontaminated soils, HMs are mainly fixed to primary minerals and

silicate making relatively immobile species but, in contaminated sites heavy metals

are generally more mobile and fixed to other soil phases. In environmental science

the assessment of the different ways of binding gives good information on the heavy

metal availability together with their toxicity and mobility, as compared to their

total concentration. Though an assessment of the different ways of binding is challenging and often impossible,various methods have been used for this purpose in



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soils, a large number based on contaminant desorption from the solid phase; whereas

others focus on contaminant adsorption from solution to the solid phase. Leaching

and desorption procedures are the most broadly accepted and applied among these

approaches.

In soil science, the extraction procedures based on a single extraction are commonly used. These techniques are aimed to dissolve a phase in which heavy metal

concentration correlates with the availability of the elements to plants. This approach

is recognized for nutrients and macro elements and it is generally used in fertility

science and quality of crops, for assessing deficiency or surplus quantity of the element in the soil, for forecasting essential element uptake. To a lesser extent, these

are used for HMs. The usage of extraction techniques for contaminated soils is

specifically focused to determine the mobility and potential bioavailability of

contaminants.

Different extraction techniques for extractable HMs in soil have been developed

and modified in recent years. There are two categories of extraction, i.e. the single

extraction method, one extraction solution and on soil sample, whereas in the

sequential extraction method, many extraction solutions are used step by step in the

same sample. These two kinds of extraction are employed using not only different

extraction protocols, but also different laboratory conditions.

Sequential extraction schemes are commonly used to determine the redistribution or partitioning of heavy metals in different chemical forms, i.e. adsorbed

(exchangeable), soluble, organic occluded and precipitated (Table 1). With each

successive step of the scheme, the bioavailability and solubility of HMs in the soil

reduces, though the extraction methods differ (Basta and Gradwohl 2000; Zakir and

Shikazono 2011). Specific chemical species measured through chemical extraction

procedures have been successfully linked with plant metal uptake in assuming the

plant availability of metals in soils (Abedin et al. 2012).

Lead has been associated with pathological changes of organs and damnification

of the central nervous system, leading to decrements of intelligence quotients (IQ)

in children. It is an abundant toxic metal responsible for soil, water as well as air

pollution, and poses a serious threat to humans, animals and plant systems. In

humans it is stored in soft tissues, bones and teeth (95 %), affecting nervous system

and brain, skeletal, circulatory, enzymatic, endocrine, immune systems and delay in

physical and mental development (Kasten-Jolly et al. 2012) (Zhang et al. 2012). It

can also cause abdominal cramps, anemia, ataxia, stunted growth, infertility in both

genders, high blood pressure, encephalopathy, hepatitis, nephritic syndrome and

weakness of the joints if the levels exceed those recommended by WHO (2000,

2011) and the allowable standard of 0.15 mg/L.

Mercury particularly in its organic form, mainly exhibits neurotoxicity and teratogenicity (Jarup 2003; Oskarsson et al. 2004). It can easily enter cell membranes

including the brain, where it can interfere with fetal development and cause autism

in neonates (Camargo 2002; Shi et al. 2014). Hg has high tendency for binding to

proteins and mainly affects the renal and nervous systems (Martínez-Juárez et al.

2012). The outbreak of Minamata disease was caused by consuming the fish rich in

mercury leading to Hg poisoning. Higher intake of Hg in food can lead pulmonary



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Table 1 Commonly used sequential extraction methods

Extraction techniques

BCR-3STEP sequential extraction

Modified BCR- 3STEP sequential extraction

Modified tessier extraction

Tessier extraction step

BCR-3STEP sequential extraction

4- Step sequential extraction

3-Step sequential extraction

BCR-Sequential step

BCRSEP optimized

BCRSEP optimized

BCRSEP

New SEP developed

Na2-EDTA 0.1 M

Sposito’s procedure

Kerstner–Forstner sequential extraction scheme

H2O, 0.1 N Ca (NO3)2 and 0.05 N EDTA

Ahnstrom and parker extraction scheme

DTPA/TEA method

Deionized water & 0.1 M Ca (NO3)2 extraction

DTPA, CaCl2, EDTA & ammonium acetate extraction

scheme

USEPA TCLP method 1311

Aqua regia extraction



References

Guevara-Riba et al. (2004)

Cuong and Obbard (2006)

Esslemont (2000)

Wepener and Vermeulen (2005)

Yuan et al. (2004)

Pempkowiak et al. (1999)

Usero et al. (1998)

Morillo et al. (2004)

Zhang et al. (2003)

Elass et al. (2004)

Pueyo et al. (2003)

Fuentes et al. (2004)

Mahavi et al. (2005)

Soumia et al. (2005)

Katasonov et al. (2005)

Garau et al. (2007)

Silveira et al. (2006)

Contin et al. (2008)

Sang-Hwan et al. (2009)

Tica et al. (2011)

Rabindra et al. (2012)

Sik et al. (2011)



dysfunction (chest pain) and dyspnea (Bernard 2008; Martínez-Juárez et al. 2012;

Mathialagan and Viraraghavan 2002). It is lethal if ingested in very minute quantity

in any of the available form found in the environment (Shi et al. 2014). The permissible limit of Hg is 2 μg L−1 (2 ppb) in drinking water (US EPA 2009). The ingestion

of methyl mercury is said to cause delay in the onset of walking, talking and diminish learning ability (US EPA 2004, 2009; Moreno et al. 2005).

The main anthropogenic activities, like waste product discharge, fertilizer applications, mining activities, paint and dye industries are the main sources responsible

for the copper release into the environment. It is present in human body in very trace

amount and is required for many enzymatic reactions like production of blood

hemoglobin in our body. In plants Cu plays a vital role in seed production, disease

resistance and regulation of water. Higher human intake of Cu can however, lead to

central nervous system irritation, GI disorders, haemolysis, anemia, liver and kidney damage (Wuana and Okieimen 2011).

Arsenic is carcinogenic in nature at higher concentrations, but toxicity depends

on the chemical form and solubility. It is available as arsenate and arsenite in nature;

reported as the main contaminant originating from anthropogenic activities and



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ending up with the arsenic pollution (Rathinasabapathi et al. 2006). Human exposure to arsenic can lead to diarrhea, vomiting and abdominal pain, skin darkening,

cardiac, circulatory and respiratory diseases. The cancer-causing ability of arsenic

is due to mono and dimethyl-arsenous acids, which are genotoxic, leading to the

inhibition of DNA repair (Butcher 2009; Scragg 2006).

Chromium can be found in two oxidation states (CrIV and CrIII). Chromium (VI)

can be reduced to Cr (III) by soil organic matter. Major Cr (VI) species include

chromate (CrO4 2−) and dichromate (Cr2 O7 2−). Chromium (III) is the dominant form

of Cr at acidic pH (<4), while leachability of Cr (VI) increases at alkaline pH. Cr

(VI) is highly soluble in water and causes digestive tract and lung cancer, epigastric

pain, nausea, vomiting, severe diarrhea, allergic dermatitis and hemorrhage

(Sugasini et al. 2014; Scragg 2006).

Selenium in trace amount is essential as it is part of important enzymes and proteins. However, at higher levels it is lethal. It can incorporate into the amino acids

and protein leading to a change in their activity by replacing sulphur (Hamilton

2004; Jarzynska and Falandysz 2011; Milovanović et al. 2014).

The dietary intake of zinc is 15 mg day−1, beyond this level its consumption has

toxic effects on humans (Lemire et al. 2008). Zinc, when consumed in large quantities, can cause respiratory and GI disorders, as well as damage to the heart, brain

and kidneys (Schwartz et al. 2003). At higher concentrations Zn can cause nausea,

epigastric pain, vomiting and diarrhea. Higher intake affects the nervous system and

iron balance, leading to the problems with cholesterol metabolism (Mertens et al.

2007; Lemire et al. 2008). It may also increase the acidity of water. The fishes found

in the waters polluted with zinc are able to biomagnify it up the food chain.

Nickel is an element that occurs in the environment only at very low levels and

is essential in small doses, but it can be dangerous when the maximum tolerable

amounts are exceeded. It is mostly used in metal plating industries, combustion of

fossil fuels, and nickel mining and electroplating (Khodadoust et al. 2004).

Generally released into the environment by power plants and incinerators, which

precipitate on the soil surface. Ni mostly affect the soil microbial activities, but usually microorganisms develop resistance to Ni. Its biomagnifications in plants has not

been investigated fully.



6



Effects on Plant and Soil Microbial Activities



HMs catalyze different enzymatic and redox reactions, carry electron and are the

main component of DNA and RNA metabolism. However, some of these such as Cd

and Pb are not necessary for plant growth, especially their high levels can adversely

affect plant growth (Miransari 2011). Soils contaminated with Cd, Pb, Hg, As, Cu

and Mn can lead to reduction in Urease (50.1 %), Acid phosphatase (47.4 %),

Dehydrogenase (39.8 %) in soil (Akmal. et al. 2005; Lee et al. 2002; Oliveira and



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Pampulha 2006). The existence of HMs shows deleterious effects on flora, fauna

and lead to groundwater pollution through leaching. They reduce the quality of

agricultural products and pose a serious threat for public health and biota (Khosravi

et al. 2009; Mohsenzadeh and Shahrokhi 2014). The heavy metals can also severely

reduce the biomass production, seed, essential oil and leaf area of major crops.

Furthermore they can disturb the cell metabolism, cause leaf abscission and senescence, lower the photosynthesis and plant nutrition and hamper the production of

enzymes in plants (Chibuike and Obiora 2014; Ghani 2010; Liu et al. 2012; Moradi

et al. 2012).

The introduction of HMs in the soil by anthropogenic and natural processes, not

only affect the human and plant health, but also the soil ecology. Soil microbial

population contributes in nitrogen fixation, assimilation and degradation of organic

residues, to release nutrients (fertility) for plant growth and development. An enrichment of HMs in the soil decreases the litter decomposition, nitrogen fixation and

nitrogen transformation, decrease in carbon mineralization and fixation, disturb

nutrient cycling and impair enzyme synthesis and activity in soil, sediments and

water. Soil enzymatic activities are known as receptive and early signs of natural

and anthropogenic disturbances. Molecular techniques can provide better results

about the qualitative and quantitative measures of microbial diversity in undisturbed

and contaminated soils. Soil microbial community is considered as the most sensitive bio-indicator of pollution effects on bioavailability and biogeochemical processes. Long term toxic effects have been reported on biologically mediated soil

processes by certain HMs (Lee et al. 2002; Li et al. 2014). The pollutants can reduce

the soil microbial biomass, enzyme activities and microbial community structure

(Reid et al. 2000, 2001; Keurentjes et al. 2011).

However, the metal exposure also leads to tolerance in the microbial community

(Friedlova 2010). Fungi and actinomycetes are more tolerant to heavy metal stresses

in polluted soils than bacteria. These metal tolerant microbial populations can be

used as potential agents in remediation of the environments contaminated with

HMs. The resistant bacteria, which can cope with the higher metal concentration of

Pb (2000 ppm & 160 ppm) and Cd (6 ppm), in the soil in lab experiment (Al Gaidi

2010; Sobolev and Begonia 2008). (Zarei et al. 2010) have been isolated. 1 out of 9

AMF from higher Pb and Zn contaminated environments, which can resist higher

concentration of Pb and Zn. Such isolates of fungi can prove effective for future

remediation processes.)



7



Conventional Approaches for HMs Removal



Every year the concentration of HMs is exceeding in the natural environment

(Govindasamy et al. 2011). According to Meers et al. (2010) the atmospheric deposition of Zn, Pb and Cd has contaminated 700 km2 in the Netherlands and the

Champagne region in Belgium. Approximately 3.88 × 106 ha of the area in China is

reported to have gotten polluted as a consequence of mining. It also includes an



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average area of 46,700 ha destroyed annually. These degraded areas, although covered by vegetation, but severe soil contamination is eventually leading to erosion

(Xia 2004). Therefore, remediation of heavy metal polluted soils is dire need of the

time to reduce the possible effects on ecological systems. Technical and financial

implications have made soil remediation a difficult exercise (Barcelo and

Poschenrieder 2003; Purkayastha et al. 2014). Over the year, several biological,

physical and chemical approaches have been used to achieve this task. The traditional soil cleanup methods include; soil incineration, soil vitrification, landfill and

excavation, soil flushing, soil washing, stabilization and electrokinetic solidification

(Sheoran et al. 2011; Wuana and Okieimen 2011). Usually, the chemical and physical approaches confront with limitations, i.e. intensive labor, high cost, disturbance

of indigenous soil microflora and irreversible changes in soil physicochemical properties. Hence, more intensive studies are required to introduce efficient, cost effective, environmentally sustainable approaches for detoxification of heavy metal

contaminated soils. One such an innovative method is phytoremediation which is

perceived as a solar energy driven eco-friendly solution to the soil contaminated

with heavy metals.



8



Immobilization of HMs Using Soil Amendments



Many efforts have been made in developing remediation technologies to minimize

or control, HMs contaminations in soil. Immobilization of toxic heavy metals can

be achieved mainly through precipitation, complexation and adsorption reactions

which result in the redistribution of metals from solution phase to a solid phase, thus

reducing their transport and bioavailability in the soil (Bolan et al. 2003a; Porter

et al. 2004).



8.1



Phosphate Compounds



Various studies have reported convincing evidences for remediative significance for

both water-soluble (diammonium phosphate, DAP) and water-insoluble (apatite,

also known as PR) P compounds to immobilize metals in soils, thus decreasing their

bioavailability for plant uptake, as their transport becomes immobile (Bolan et al.

2003b, c). Phosphate compounds increase the immobilization of metals in soils by

different processes, such as, direct metal absorption/substitution of phosphate compounds, precipitation of metals with phosphate solution as metal phosphates. An

application of phosphate compounds to the soil can cause direct adsorption of metals through increased phosphate anion-induced metal adsorption and increased surface charge of these compounds depending upon the sources.

Precipitation as metal–phosphate has proven one of the main ways for the immobilization of HMs in soils (Bolan et al. 2014). These fairly stable metal–phosphate



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compounds have extremely low solubility over a wide pH range, which makes phosphate application an attractive technology for managing heavy metal contaminated

soils, but phosphate is also a fossil source and high application rates cause eutrophication of water resources. In typical arable soils, precipitation of heavy metals is

unlikely, but in modest metal contaminated soils, this process can play a major role

in the immobilization of such metals.

Chrysochoou et al. (2007) have reported the potential of apatite to immobilize

heavy metals in contaminated soils or solution by metal-phosphate precipitation.

The precipitants are usually termed as chloropyromorphite or as hydroxypyromorphite. Two methods have been recommended for the reaction of dissolved Pb with

apatite. Firstly, in apatite, Pb (II) can be substituted for Ca (II), thereby, through

adsorption of Pb or by dissolution of hydroxyapatite (Ca10 (PO4)6 (OH) 2), (Ca, Pb)

apatite could be formed followed by co-precipitation of mixed apatite. Secondly,

followed by precipitation of pure hydroxypyromorphite (Pb10 (PO4)6(OH) 2), Pb2+

can react with apatite through hydroxyapatite dissolution.

A substitute process, which happens to be significant in temperate soils, involves

metal-ligand complexation in solution and followed the reduction in cation charge,

that most likely decreases adsorption. The formation of soluble Cd-Phosphate complexes reduces Cd (II) sorption in soils in the occurrence of phosphate. Free Cd (II)

activity, rather than total dissolved Cd (II) value, is a regulatory factor in Cd (II)

sorption. The efficacy of phosphate-induced metal immobilization can be improved

by enhancing solubility of phosphate compounds in the soil. The combination of

rock phosphate and phosphoric acid, potentially immobilizes Pb. To enhance heavy

metal immobilization in soil, phosphate solubilizing bacteria have been used which

gradually release phosphate from insoluble phosphate rock (Park et al. 2011a, c).

There are some drawbacks related to the usage of phosphate compounds for metal

immobilization; after the phosphate treatment, the leaching of phosphate must be

considered. A mixture of soil with a phosphate addition in the molar ratio of H3PO4:

hydroxyapatite of 0.75:1 is suggested to be optimum to reduce phosphorus

leaching.

The second problem concerns the influence of bacteria on the stability of pyromorphite. It is assumed that the microbes enhance the dissolution of mineral P,

promoting its transformation into pyromorphite. The controversy of the method

stems from the need of introducing a living, extraneous strain of bacteria in an

uncontrolled environment, although the long-term effect of such a treatment is

unknown. Park et al. (2011a, b) showed that PSB (phosphate-solubilizing bacteria)

can affect the stability of pyromorphite and that the effectiveness of the process

depends on the availability of dissolved phosphates in solution. However, the interaction between microbes and minerals are complex and some aspects of the potential involvement of PSB in remediation treatments remain unclear. There is some

evidence that various organic compounds, microbial metabolites and plant activity

may increase the dissolution of pyromorphite and cause a secondary Pb release

(Formina et al. 2004; Manecki and Maurice 2008; Debela et al. 2010, 2013; Topolska

et al. 2013).



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8.2



385



Lime Treatment



Lime is basically used to ameliorate soil acidity, but at the same time it is getting

wide acceptance as a potential option among the scientific community to reduce

metal poisoning in the soil. Liming materials are in a diverse range with a difference

in their potential to neutralize the acidity. Over the years, liming has been employed

as a regular traditional practice to decrease levels of heavy metals in the edible parts

of agricultural crops. Liming increases sorption of metals by decreasing the H+ concentration and enhancing negatively charged ions. Lime and red mud as the addition

of alkaline material to enhance the concentration of the residual fraction of heavy

metals in the contaminated soil. The precipitation of metals results due to an increase

in pH by lime and red mud (Garau et al. 2007).

The competition between Ca (II) and metal ions and reduced mobility in soils by

precipitation and adsorption result in reducing metal uptake by plants due to the

effect of liming on the root surface. An in-situ field trial of heavy metal remediation

in contaminated soil proved that by combing red mud and lime soil pH increases

and metal bioavailability is reduced, thus resulting in the appearance of a vegetative

cover in Pb and Cd contaminated soils (Gray et al. 2006).

Lime can be employed with the combination of other amendments to decrease

metal availability is soil amendments. When lime is mixed with biosolids, it

decreases electrical conductivity (EC) and enhances pH by precipitation of soluble

ions (Fang et al. 2014). Lime also effectively increases pH when lime is added during composting, it decreases leaching and bioavailability of metals (Singh and

Kalamdhad 2013).



8.3



Cement-Based Solidification/Stabilization



Soil contaminated with HMs usually need solidification/stabilization (s/s) prior to

use, in order to lower the leaching rate and bioavailability. Cement is the most

adaptable binder currently available for their immobilization. The selection of

cements and operating parameters depends upon an understanding of the chemistry

of the system (Chen et al. 2009). Cement-based stabilization/solidification technology is an attractive option for the management of soils polluted with toxic metals to

facilitate land use and reduce the release of contaminants into the environment. The

efficacy of cement-based solidification/stabilization can be improved by modifying

cement phase compositions and controlling temperature, water/solid ratios, particle

size, and other factors which affect setting and strength development and long-term

durability of solidified waste forms. The potentially dangerous HMs may adversely

affect the cementing matrix; pretreatment to render such substances harmless,

e.g., by adsorbent adding, is necessary in some cases (Jang and Kim 2000).

Portland cement (15 %, w/w) was used for solidification/stabilization (S/S) in the

HMs contaminated soils from the former industrial sites. Soils formed solid



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monoliths with cement. Concentrations of cadmium and lead in water extracts from

S/S soils generally decreased. Their concentrations in the TCLP extracts from S/S

soils were lower than from original soils (Voglara and Leˇstan 2010). Formulations

of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement

(CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta extra

(PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF),

polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an

industrial Brownfield contaminated with up to 157, 32 mg kg − 1 of cadmium and

lead respectively. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of cadmium and lead into

deionized water below the limit of quantification and into TCLP solution by up to

55 and 185 times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times respectively (Voglara and

Leˇstan 2010). It appears that there are several attractive areas for further investigation in the field of cement-based solidification/stabilization of cadmium and lead in

contaminated soils. For example, the phased development of cement pastes in the

presence of cadmium and lead, the dissolution and precipitation of stoichiometries

phases and of solid solutions, and surface phenomena controlling cadmium and

lead immobilization.



8.4



Animal Manure and Biosolids



Animal manures and biosolids are the significant sources of organic composts.

Biosolids are considered traditionally as one of the key sources of metal contamination in the soil. Recent developments in the industrial wastewater and sewage treatment technologies have successfully decreased metal contamination in biosolids.

Moreover, alkaline materials are used for stabilizing metals in biosolids. Zeolites

are also valuable as metal scavengers in the metal contaminated biosolids. Heavy

metals are stabilized by natural zeolites which transform them in the exchangeable

and carbonate to residual fractions (Zorpas et al. 2000).

Cattle, poultry and dairy are key sources of global animal manure byproducts.

Majority of the manure products are less contaminated with metals except arsenic

in poultry and, zinc and copper in swine manure respectively. However, recent

developments in the manure as a byproduct treatment has brought a reduction in the

bioavailability of metals. For example, treatment of poultry manure with alum

[Al2(SO4)3] has reduced the concentration of water soluble cadmium. Low metal

contaminated manure byproducts can be employed in stabilizing metals in the soil.

Various studies have assessed the role of biosolids in the HM contamination in the

soil, only few studies have documented the advantageous impact of organic amendment as a sink of the stabilization of toxic metals in the soil (Brown et al. 2003;

Li et al. 2000). Alkaline-stabilized biosolids are known as designer sludge with



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exceptional quality of low metal bioavailability, and can be employed as potential

sinks for decreasing metal bioavailability in the sediments and soil. Complexation,

redox reaction and adsorption are the immobilization processes accomplished

through such amendments.

Metals make both soluble and insoluble complexes with organic constituents in

the soil, the mechanisms specially depend on the type of the organic matter. The

organic constituent of soil component has great affiliation with metal cations due to

the existence of functional groups or legends which can form chelates with metals.

The alcoholic, phenolic, carbonyl and carboxyl functional groups dissociate due to

increasing pH, thus enhancing legand ions affinity towards metal cations. Through

the prevention of sulfide oxidation/hydrolysis, the decrease in the metal concentrations can be credited to an increase in soil pH (Hartley et al. 2004). Likewise, compost amendment has increased the growth of Lupinus albus (white lupin) together

with a decrease in the uptake of lead by reducing metal bioavailability in the soils

(Castaldi et al. 2005). High fulvic and high compost humic acid concentrations are

credited for the high metal binding capacities of compost (O’Dell et al. 2007;

Perminova and Hatfield 2005).



8.5



Oxides of Metals



The oxides of iron, aluminium and manganese play an important role in metal geochemistry in soils. Atmospheric nature and highly active surface area make them

potential for immobilization and sorption of diverse soil contaminants.

Co-precipitation, forming inner-surface complexes and specific sorption result in a

strong metal binding by metal oxides. Similarly synthesized industrial by-products

and naturally occurring oxides have been worked upon for their potentiality to be

employed for soil remediation. Recent developments in the application of metal

oxides and its precursors for chemical immobilization of metals in contaminated

soils have been investigated at length (Komarek et al. 2013).

Oxides of manganese (birnessite and a phyllomanganates group of minerals),

oxyhydroxides (goethite, ferrihydrite, lepidocrocite, feroxyhite and akaganeite) and

oxides of iron (magnetite, hematite and maghemite) mostly occur in soil. AsO4 3−

and Pb (II) form inner sphere surface complexes with hydrous ferric oxide and lead

and cadmium form mononuclear complexes on goethite and ferrihydrite surfaces

(Knox et al. 2001). The surfaces of oxides of iron hydrous have a significant role to

play in metal retention. The lead and cadmium have been immobilized with the

amalgamation of iron (II) and (III) sulfates (Hartley et al. 2004). The useful re-use

of iron oxides-based residue of drinking water treatment may be a beneficial soil

amendment for various cations and anions. Oxides of manganese exist in soil, i.e.

cryptomelane, todorokite, hausmannite and birnessite. Out of these birnessite exhibits the highest adsorption capacity on cadmium and lead among all. The sequence of

greatest sorption capacity by birnessite was Pb (II) > Cd(II) and the maximum



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4 Mining, Milling Processes and Industrial Wastes

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