Discipline:

Microbial Diversity and

Bioremediation

“Heavy Metals” and Persistent Organic

Compounds: Effects and Mechanisms of Toxicity

Professor Luciana Maria Saran

Technology Department

School of Agricultural and Veterinarian Sciences

São Paulo State University

Jaboticabal, SP, Brazil

lmsaran@fcav.unesp.br

1

2

1. Major Environmental

Pollutants

• About Pollutant:

“A substance or energy introduced into the

environment having undesired adverse effects and

possibly causing long- or short-term damage by

changing the growth rate of plants or animal species,

or by interfering with human amenities and health is

called pollutant”.

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

1. Major Environmental

Pollutants

• “Heavy metals”.

• Polyciclic aromatic hydrocarbons (PHAs).

WHY?

• Because their persistent nature and tendency to

spread into ground as well as surface water.

3

4

1. Major Environmental

Pollutants: Sources

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

5

1. Major Environmental

Pollutants: Generalized View of

the Effects of Toxic Metals and

PHAs on the Human Body

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

6

1. Major Pollutants in Nature,

Their Source, Route of

Exposure, Level of

Contamination, Health Effects

Compound Source of

Exposure

Major Route

of Exposure

Environmental

Level

Health Effects

Arsenic, As

Food, air,

drinking water

Oral

• Air: 1-3 ng/m3

(rural areas);

20-100 ng/m3

(urban areas).

• Drinking water: 2

µg/L.

• Soil: 0.1-97 mg/kg.

Lung cancer,

cardiovascular

effects, and

encephalopathy

Cadmium, Cd

Food, cigarette,

smoking, drinking

water, and air

Oral, inhalation,

and dermal

• Air: 0.1-5 ng/m3

(rural areas);

2-15 ng/m3 (urban

areas).

• Drinking water:

< 5 µg/L.

• Soil: 0.06-1.1

mg/kg; 0.27 mg/kg

(agricultural).

Glomerular

damage, bone

mineralization, and

emphysema

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

7

1. Major Pollutants in Nature,

Their Source, Route of

Exposure, Level of

Contamination, Health Effects

Compound Source of

Exposure

Major Route

of Exposure

Environmental

Level

Health Effects

Lead, Pb

Contaminated

food, drinking

water, lead-

based paint

Inhalation

• Air: < 0.05 µg/m3.

• Water: 5-10 µg/L.

• Soil: < 10-30 g/kg.

Elevated blood

pressure, colic in

children,

neuropathy,

reduced fertility

Mercury, Hg

Water, air,

dental

amalgam

fillings, waste

incinerators

Inhalation and

oral

•Air: < 0.9-1.5 ng/m3.

• Water: 0.5-100 ng/L.

• Soil: 6-17 mg/kg.

Diarrhea and/or

abdominal pain,

kidney damage,

and acrodynia

PHAs

Air and food

Inhalation and

oral

•Air: < 0.9-1.5 ng/m3.

• Water: 0.5-100 ng/L.

• Soil: 6-17 mg/kg.

Cancer, mutation,

and skin irritation

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

2. Major Environmental

Pollutants: “Heavy Metals”

• There are 14 essential metals for human beings: Ca,

K, Na, Mg, Fe, Zn, Cu, Sn, V, Cr, Mn, Mo, Co and Ni.

• Some metals considered toxic at high concentrations,

such as Zn, Cu, Cr and Ni, are fundamental to the

metabolism in low concentrations.

8

2. Major Environmental

Pollutants: “Heavy Metals”

• Influence of the metal concentration on the development of

a living being: (a) essential metal and (b) non-essential

metal.

Develo

pm

en

t

Concentration

Deficient Optimum Toxic Letal

(a)

Develo

pm

en

t

Concentration

Toxic Letal Tolerable

(b)

9

2.1 Sources of

“Heavy Metals” in the

Environment

Natural Sources Anthropogenic Sources

• Volcanic eruptions • Mining

• Earthquakes • Energy and Fuel

Production

• Floods • Eletrocplating

• Storms • Waste water sludge

treatment

• Nuclear fuels

• Agricultural wastes

10

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

2.2 Biogeochemical Cycles

of Heavy Metals in the

Environment

11

Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

2.3 Arsenic, As

• It is one of the most toxic elements.

• It occurs naturally in the earth's

crust.

• Present in the atmosphere, soil,

rocks, freshwater and living

organisms.

12

• In nature: it exists in various chemical forms (organic

and inorganic species).

• Oxidation states: As5+, As3+, As0 e As3-

2.3 Arsenic, As: Main

Species Reported

in the Literature

Source: Souza, J.M.O. Quim. Nova, 2014. 38(1), 118-127. 13

Inorganic Species

Organic Species

2.3 Arsenic, As: Main

Species Reported

in the literature

Source: Souza, J.M.O. et al. Quim. Nova, 2014. 38(1), 118-127. 14

Organic Species

2.3 Arsenic, As: Main

Species Reported

in the Literature

Species that may occur in water:

• In natural water arsenite, As(III); arsenate, As(V);

monomethylarsonic ion (MMA) and dimethylarsinic

ion (DMA).

• In ground water arsenite, As(III) and arsenate,

As(V) .

• In sea water, ponds, lakes and where there is

possibility of biomethylation: arsenite, As(III) and

arsenate, As(V) occur together with MMA and DMA.

Source: Barra, C.M. et al. Quim. Nova, 2000. 23(1), 58-70. 15

2.3 Arsenic, As:

Main Anthropic Sources

• Mining activity.

• Use of fossil fuels.

• Herbicides, insecticides and defoliants containing As

and used in agriculture.

• As is used in the manufacture of some glass,

semiconductor materials and photoconductors.

• As is used as a feed additive for poultry and cattle.

Sources: Barra, C.M. et al. Quim. Nova, 2000. 23(1), 58-70.

Montoya, E.A.R. et al. Terra Latinoamericana , 2015. 33(2), 103-118.

16

2.3 Arsenic, As: Cycle

Source: Langdon, C.J. et al. Environmental Pollution , 2003.124(3), 361-373. 17

2.3 Arsenic, As:

Toxicological Aspects

• Inorganic compounds are 100 times more toxic than

the partially methylated forms (monomethylarsonic

acid, MMA or MMAA and dimethylarsinic acid, DMA or

DMAA).

Source: Farias, J.S.F et al. Quim. Nova, 2012. 35(7), 1401-1406.

18

• As(III) and As(V): most toxic

species.

• As(III) is 60 times more toxic than

As(V).

2.3 Arsenic, As:

Toxicological Aspects

• Order of toxicity of arsenic compounds:

organic compounds of As5+

organic compounds of As3+

inorganic compounds of As5+

inorganic compounds of As3+

To

xic

ity In

cre

as

ing

Ord

er

Source: Farias, J.S.F et al. Quim. Nova, 2012. 35(7), 1401-1406.

19

2.3 Arsenic, As:

Toxicological Aspects

• Absorption of arsenic compounds oral via and

inhalation.

• It can also occur by dermal via.

• Main route of elimination by the human body urine.

• Inorganic arsenic methylation in the human body is a

detoxification process that occurs in the kidneys:

As(V) As(III) MMA(V) MMA(III) DMA(V)

Source: Barra, C.M. et al. Quim. Nova, 2000. 23(1), 58-70. 20

2.3 Arsenic, As:

Toxicological Aspects

• Exposure to arsenic may lead to:

# Cardiovascular problems (hypertension and

arrhythmias).

# Conjunctivitis.

# Hyperkeratosis.

# Hyperpigmentation and gangrene in the limbs.

# Cancer (lung, skin, bladder and kidney) in humans

may be caused by As inorganic species.

21

2.4 Mercury, Hg

• It occurs in nature in three oxidation states: Hg0, Hg2+

(mercury ion) and Hg2+ (mercuric ion).

22 So

urc

es

: M

icaro

ni, R

.C.C

.M.

et

al. Q

uim

. N

ova

, 2

00

0. 2

3(4

), 4

87

-49

5.

Bis

ino

ti, M

.C;

Ja

rdim

, W

.F. Q

uim

. N

ova

, 2

00

4. 2

7(4

), 5

93

-60

0.

• Hg0 is a liquid metal and argent

at room temperature.

• In nature it is associated with

other elements (HgS).

• Hg0 is obtained by heating the HgS followed by

condensation.

2.4 Mercury, Hg:

Main Sources

• Natural sources:

. Volcanic eruptions;

. Natural evaporation and mercury mines.

23

2.4 Mercury, Hg:

Main Sources

• Anthropogenic Sources:

. Fossil fuel burning;

. Electrolytic production of chloro-soda;

. Acetaldeído production;

. Waste incinerators;

. Paper pulp production;

. Inks;

. Pesticides;

. Fungicides.

24

So

urc

es

: M

icaro

ni, R

.C.C

.M.

et

al. Q

uim

. N

ova

, 2

00

0. 2

3(4

), 4

87

-49

5.

Bis

ino

ti, M

.C;

Ja

rdim

, W

.F. Q

uim

. N

ova

, 2

00

4. 2

7(4

), 5

93

-60

0.

2.4 Mercury, Hg:

Chemical Species

• Inorganic species: elementary Hg (Hg0); mercury ion

(Hg22+), little stable in environmental systems and

mercuric ion (Hg2+).

• Organic species (alkylmercury compounds):

methylmercury (CH3Hg+) and dimethylmercury

[(CH3)2Hg)] are the most commun.

• Increasing order of solubility in water of some

mercury compounds: Hg0, Hg2Cl2, Hg(CH3)2 and

HgCl2.

25 Sources: Micaroni, R.C.C.M. et al. Quim. Nova, 2000. 23(4), 487-495.

Bisinoti, M.C; Jardim, W.F. Quim. Nova, 2004. 27(4), 593-600.

2.4 Mercury, Hg:

Global Cycle

26

27

2.4 Mercury, Hg:

Global Cycle

• Hg2+ conversion to organic forms:

Hg2+ + organic matter CH3Hg+ and (CH3)2Hg

H2O, bacteria

Hg2+ HgS Hg2SO4 CH3Hg+

H2S

Eutropic condition

aeration

Less

soluble

More

Soluble

Source: Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical Sciences, 2007. 2(5), 112-118.

2.4 Mercury, Hg:

Toxicological Aspects

• Occupational exposure to mercury human

contamination occurs through the respiratory tract.

• Occupational contamination Hg0 and mercury salts

are mainly responsible.

• Environmental contamination caused by ingestion

of fish (from freshwater or salt water), affects the

bloodstream and causes problems in the central

nervous system.

• Organic mercury compounds, mainly methylmercury,

are responsible for environmental contamination. 28

So

urc

es

: M

icaro

ni, R

.C.C

.M.

et

al. Q

uim

. N

ova

, 2

00

0. 2

3(4

), 4

87

-49

5.

Bis

ino

ti, M

.C;

Ja

rdim

, W

.F. Q

uim

. N

ova

, 2

00

4. 2

7(4

), 5

93

-60

0.

2.4 Mercury, Hg:

Toxicological Aspects

Mercury bioaccumulation

or biomagnification

29

2.4 Mercury, Hg:

Toxicological Aspects

• Toxic effects of Hg0 occur after oxidation of this

specie.

• Due to the high affinity of Hg for sulfhydryl groups of

proteins and for phosphoryl, amide and amine

groups.

• It interferes with cell metabolic functions, causes

damage to the cell membrane and in the transport

through the membrane.

• Causes mental deterioration in highly contaminated

individuals. 30

So

urc

es

: M

icaro

ni, R

.C.C

.M.

et

al. Q

uim

. N

ova

, 2

00

0. 2

3(4

), 4

87

-49

5.

Bis

ino

ti, M

.C;

Ja

rdim

, W

.F. Q

uim

. N

ova

, 2

00

4. 2

7(4

), 5

93

-60

0.

31

2.5 Chromium, Cr

• It´s found in trace amount in most rocks and soils.

• In nature it is found in a higly insoluble form.

• All the common soluble forms due to the

contamination of industrial effluents.

• Cr(VI) is carcinogenic.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

32

2.5 Chromium, Cr:

Chemical Species

• Cr can exist in several chemical forms displaying

oxidation numbers from 0 to VI.

• Cr(III) and Cr(VI) are stable enough to ocurr in the

environment.

• In natural waters: Cr exists in its two stable oxidation

states, Cr(III) and Cr(VI).

• Under anoxic or suboxic conditions, Cr(III) should be

the only form.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

33

2.5 Chromium, Cr:

Chemical Species

• In soils: Cr is present mostly as insoluble Cr(OH)3 or

as Cr(III) adsorbed to soil components.

• In neutral-to-alkaline soils: Cr(VI) exists monstly in

soluble (e.g. Na2CrO4) but also in moderately-to-

sparingly soluble chromates (e.g. CaCrO4, BaCrO4,

PbCrO4).

• In more acid soils (pH < 6): HCrO4- becomes a

dominant form.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

34

2.5 Chromium, Cr in

Waters: Sources

• Natural sources:

- Weathering of rock constituents;

- Wet precipitation;

- Dry fallout from the atmosphere;

- Run-off from the terristrial systems.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

35

2.5 Chromium, Cr in

Waters: Sources

• Anthropic sources:

- Discharge of wastewater from the metallurgical

industry;

- Electroplating and tanning industries;

- From sanitary landfill leaching;

- Water cooling towers;

- Tanning industries.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

36

2.5 Chromium, Cr in Soil

Systems: Sources

• Main sources of Cr in natural soils: weathering of their

parent materials.

• An increase in local concentration in soils originates

from:

- fallout and washout of atmospheric Cr-containing

particles;

- refuse from industrial activity.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

37

2.5 Chromium, Cr in

Atmospheric Systems:

Sources

• Natural sources:

- Volcanic eruptions;

- Erosion of soils and rocks;

Souce: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

38

2.5 Chromium, Cr in

Atmospheric Systems:

Sources

• Anthropic sources:

- Metallurgical industries;

- Refractory brick prodution;

- Eletroplating;

- Combustion of fuels;

- Production of Cr chemicals (chromates, dichromates,

pigments, Cr trioxide and Cr salts).

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

39

2.5 Chromium, Cr:

Toxicological Aspects

• Inhalation and retention of Cr(VI)-containing materials

can cause perforation of the nasal septum, asthma,

bronchits, pneumonitis, inflamation of the larynx and

liver and increase incidence of bronchogenic

carcinoma.

• Skin contact of Cr(VI) compounds can induce skin

allergies, dermatitis, dermal necrosis and dermal

corrosion.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

40

2.5 Chromium, Cr:

Toxicological Aspects

• Toxic properties of Cr(VI) arise from:

- the possibility of free difusion across cell

membranes;

- strong oxidative potential;

- formation of free radicals during the reduction of

Cr(VI) to Cr(III) occurring inside the cell Cr(III) in a

significant concetration cause adverse effects.

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

41

2.5 Chromium, Cr:

Toxicological Aspects

Cr(III)

Capability to coordinate

various organic compounds

Resulting in inhibition

of ome metallo-enzyme

systems

Source: Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

42

2.6 Cadmium, Cd

• Cd is a naturally occurring metal, usually being found

as an impurity in Zn or lead (Pb) deposits.

• It generally exists as divalent cation (Cd2+),

complexed with other elements (e.g. CdCl2);

• Comercially, Cd is used in televisions screens, lasers,

batteries, paint pgiments, cosmetic, in galvanizing

steel, and as barrier in nuclear fission.

43

2.6 Cadmium, Cd

44

2.6 Cadmium, Cd

• Natural activities: volcanic activity, weathering and

erosion.

• Human activities: tobacco smoking, mining, smelting

and refining of non-ferrous metals, fossil fuel

combustion, incineration of municipal waste

(especially cadmium-containing batteries and

plastics) and manufacture of phosphate fertilizers.

• Application of municipal sludge to agricultural soil

can be a significant source of cadmium.

45

2.6 Cadmium, Cd

• Cd exposure occurs from ingestion of contaminated

food.

• Cd exposure from drinking-water is relatively

unimportant compared with exposure from the diet.

• Smoking tobacco is an important source of exposure.

46

2.6 Cadmium, Cd

• The kidney is the critical target organ. Cd

accumulates primarily in the kidneys and this

accumulation may led to renal dysfunction.

• High intake of Cd can lead to disturbances in Ca

metabolism and the formation of kidney stones.

• High inhalation exposure to cadmium oxide fume

results in peneuminitis.

• It can contribute to the development of lung, kidney

and prostate cancer.

47

2.7 “Heavy Metals”:

Biochemistry of Toxicity

• “Heavy Metals” when ingested, in the acid medium

of the stomach, they are convertes to their stable

oxidation states (Pb2+, Cd2+, As2+, As3+, Hg2+).

• “They combine with the body´s biomolecules such as

proteins and enzymes to form strong and stable

chemical bonds”.

Source: Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical Sciences, 2007. 2(5), 112-118.

48

2.7 “Heavy Metals”:

Biochemistry of Toxicity

• Heavy Metals´ reactions during bond formation with

the sulphydryl groups (-SH) of cysteine and sulphur

atoms of methionine (-SCH3):

Source: Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical Sciences, 2007. 2(5), 112-118.

49

2.7 “Heavy Metals”:

Biochemistry of Toxicity

• “Heavy Metals” can induce enzymatic inhibition for

example, toxic As3+ occurs in herbicide, fungicides

and inseticides and can attack –SH groups in

enzymes to inhibit their bioactivities.

Source: Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical Sciences, 2007. 2(5), 112-118.

50

2.8 “Heavy Metals” in

Drinking Water

Heavy metal Portaria MS N.

2.914/2011 (mg L-1)

WHO

(mg L-1)

Arsenic, As 0.01 0.01

Barium, Ba 0.7 1.3

Cadmium, Cd 0.005 0.003

Lead, Pb 0.01 0.01

Copper, Cu 2 2

Chromium, Cr 0.05 0.05

Mercury, Hg 0.001 0.006

Nickel, Ni 0.07 0.07

Selenium, Se 0.01 0.04

51

2.9 “Heavy Metals” in

Freshwater

Heavy metal CONAMA N. 357/2005

Classes 1 e 2 (mg L-1)

CONAMA N. 357/2005

Classe 3 (mg L-1)

Arsenic, As 0.01 0.033

Barium, Ba 0.7 1.0

Cadmium, Cd 0.001 0.01

Lead, Pb 0.01 0.033

Copper, Cu 0.009 0.013

Chromium, Cr 0.05 0.05

Mercury, Hg 0.0002 0.002

Nickel, Ni 0.025 0.025

Selenium, Se 0.01 0.05

52

2.10 “Heavy Metals” in

Wastewater

Heavy metal CONAMA N. 430/2011

(mg L-1)

Arsenic, As 0.5

Barium, Ba 5.0

Cadmium, Cd 0.2

Lead, Pb 0.5

Copper, Cu 1.0

Chromium, Cr 0.1 (Cr6+); 1.0 (Cr3+)

Mercury, Hg 0.01

Nickel, Ni 2.0

Selenium, Se 0.3

53

2.11 “Heavy Metals”

in Soil

• See CONAMA Resolution N. 420, December 28, 2009.

This resolution provides guiding values of quality

soil for the presence of chemical substances and

establishes guidelines for the environmental

management of areas contaminated by these

substances due to anthropic activities.

54

2.12 United State Environmental

Protection Agency (USEPA) Maximum

Contamination Levels for Heavy Metal

concentration in Air, Soil and Water

Source: Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical Sciences, 2007. 2(5), 112-118.

55

3. Persistent Organic

Compounds

56

3.1 Polyciclic Aromatic

Hydrocarbons (PHAs)

• PHAs are a large group of compounds formed during

incomplete combustion organic mater.

• PHAs highly hydrophobic in nature and tend to

adsorb into the surface of soil (or sediments in marine

environment).

• 16 PHAs have been listed as a toxic pollutants by the

US EPA (Environmental Protection Agency).

• Potent carcinogens and mutagenic. Source: Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9

3.1 Polyciclic Aromatic

Hydrocarbons (PHAs)

57

58

Biogeochemical Cycles of PHAs

Fo

nte

: D

as, S

. e

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59

3.2 Polyclorinated

Biphenyls (PCBs)

• They are produced by chemical synthesis.

• There is no natural processes can generate PCBs.

• PCBs good insulators.

60

3.2 Polyclorinated

Biphenyls (PCBs)

61

3.2 Polyclorinated

Biphenyls (PCBs): Sources

• Transformers, capacitors, and others eletrical

equipments PCBs have been used as coolants and

lubrificants.

• Control formulations of dedusting agents and in used

oil for dust supression.

• Burning of PCB-containing products.

62

3.3 Nitroaromatic

Compounds (NACs)

• NACs are recalcitrant due to the presence of the nitro

group.

63

3.3 Nitroaromatic

Compounds (NACs)

• They are introduced to the environment from

anthropogenic sources and synthesis.

• They are used as dyes, pesticides, explosives, and

fharmaceusticals.

• Vast aplication of them has led to the environmental

contamination of soil, ground water, and freshwater.

64

3.4 Phtalates

• They are used as plasticizers and

used to make plastic flexible and

resilient.

• They are in products like automobile

parts, toys, cosmetics, and food

packing.

• Phthalates cause developmental and reprodutive

toxicity. Chronic exposure to them causes cancer.

65

3.4 Polybrominated

Biphenyls (PBBs)

• PBBs are artificial chemicals.

• Persistent environmental pollutants.

• They are used as plastic additives to make products

like televisions, plastic foams, computer monitors, etc.

66

References

• Barra, C.M. et al. Quim. Nova, 2000. 23(1), 58-70.

• Bisinoti, M.C; Jardim, W.F. Quim. Nova, 2004. 27(4), 593-600.

• Das, S. et al. Bicrobial Biodegradation and Biorremediation, 2014.

DOI: http://dx.doi.org/10.1016/B978-0-12-800021-2.00002-9.

• Duruibe, J.O.; Ogwuegbu, M.O.C; Egwurugwu, J.N. International Journal of Physical

Sciences, 2007. 2(5), 112-118.

• Farias, J.S.F et al. Quim. Nova, 2012. 35(7), 1401-1406.

• Kotás, J.; Stasicka, Z. Environmental Pollution, 2000. 107, 263-283.

• Langdon, C.J. et al. Environmental Pollution , 2003.124(3), 361-373.

• Micaroni, R.C.C.M. et al. Quim. Nova, 2000. 23(4), 487-495.

• Montoya, E.A.R. et al. Terra Latinoamericana , 2015. 33(2), 103-118.

• Souza, J.M.O. Quim. Nova, 2014. 38(1), 118-127.