Gold mines and impact of heavy metals on the environment

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 6, Issue 2, February (2015), pp. 62-69© IAEME
70
GOLD MINES AND IMPACT OF HEAVY METALS ON
THE ENVIRONMENT
BADER A. HAKAMI
Faculty of Earth Sciences, King Abdul Aziz University, Jeddah, Saudi Arabia
ABSTRACT
This research report puts light on the research and the study of gold mining plant in Oman
and its assessment and its contribution of gold mining into various other environmental media on the
basis of heavy metals. In this research study, various samples were collected from crop plants,
stream waters and soil of the plant area of gold mining. In this research the collected samples were
further examined for thirteen heavy metals such as barium (Ba), iron (Fe), strontium (Sr), aluminum
(Al), zinc (Zn), lead (Pb), cobalt (Co), cadmium (Cd), copper (Cu),nickel (Ni), manganese (Mn),
Chromium (Cr), vanadium (V). During the investigation, the acid evaporation pond, the water
showed a high amount of concentration of iron as well as a few of the residual quantities of zinc,
vanadium and aluminum, on the other hand water for the citizens showed the concentrations all
above Who standards and Omani. The water on the surface area indicated high concentrations of
copper and major concentrations of manganese, nickel, aluminum, iron and zinc. Whereas the desert
plant species growing nearby the gold pit showed large concentrations of heavy metals such as
manganese, aluminum, nickel, iron, zinc as well as vanadium, also some of the other plants of the
same desert plant species utilize as a control indicated only a few concentrations of all heavy metals.
After analyzing the whole research study of heavy metals, the researcher discovered that few of the
toxic metals engaged by plants showed by restriction of major metal.
Keywords: Gold Mines, Pollution, Heavy metals, mining.
INTRODUCTION
Mining is one of the activities of human that puts a negative impact on the quality of the
environment. Mining is the main source of destruction of natural ecosystems that is done by soil and
vegetation removal, as well as burial under the waste disposable sites. The wastage in mining can be
divided into two categories such as waste rock generated while removing the body of the ore, and
mine tailings occurrence in the processed ore doling out. There are many mineral processing
methods like ores and rocks, recovery of the ores, disposal of wastewaters and tailings around the
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND
TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 6, Issue 2, February (2015), pp. 70-80
© IAEME: www.iaeme.com/IJMET.asp
Journal Impact Factor (2015): 8.8293 (Calculated by GISI)
www.jifactor.com
IJMET
© I A E M E

71
metal mines WHO (2006). The heavy metals are discharged in soil, water and sediment that is also
known as environmental media. According to the changes in chemical and physical properties in the
Lithosphere, heavy metals in tailings are dispersed, transferred and collected from animals and plants
are further passed up on the food chain to the human beings as last and the final consumer. Heavy
metals are present in tailings and few toxic and harmful contaminants that are present in the soil that
put a harmful effect on the ecosystem near the metal mines. Soil contamination, water and biota by
heavy metals, sediments all these are the main concern in the mining sites for the reason of their
toxicity, collection of food chains and persistence (Akabzaa & Banoeng,2005). Heavy metals that are
connected with mining are of particular attention for various reasons. Heavy metals have a tendency
of collection of soils and sediments, also have long persistence time that is not biodegradable.
Another reason is omnipresent in the soils and sediments that come from natural as well as not
natural sources inherited from big parent rocks, water applied in local and long range atmosphere
with deposition of dust and mining emissions (Sengupta, 2002). These heavy metals enter the food
chain followed by human beings, including animals and plants. Heavy metals with low
concentrations play an important role as nutrients for animals and plants as well as humans, these are
present in the high quantity in different forms which is not only harmful but also put adverse effects.
An example of toxic in high concentration is zinc and copper that are also important for normal
metabolic Olade (2009). Human organs can get damaged when the zinc and copper quantities
increase, it is very harmful. Lead, cadmium, arsenic causes cancer, metabolic disorders, neural and
various other diseases and disorders. Arsenic is amongst the most essential contaminants of drinking
water in the world as it is believed to cause kidney problems, urinary bladder, lungs and skin
problems. Another heavy metal that is lead is responsible for brain failure, nerve, kidney and liver
damage in adults, cadmium causes blood damage, bone, liver and kidney failure in long term
exposure. Heavy metals are responsible for oxidative damage in plants, metal stress put harmful
effect on the stomatal resistance, chlorophyll fluorescence as well as photosynthesis and reproductive
processes lead decreases the production of chlorophyll while arsenic comes in contact with the
metabolic processes, hence the growth of the plant is decreased (Adimado & Amegbey,2003). There
are ample of case histories that are related with the health problems which are formed due to the
adsorption of the heavy metals which were reported and studied from various parts of the world.
Major important issues concerned and connected with the metal mining activities is acid mine
drainage. Acid mine drainage is formed by the oxidation of metallic sulphides and pyrite. The origin
and the beginning of the major chemical, physical and biological factors of acid drainage are
involved in the process which is studied by many investigators all around the world (Meili,2003).
Gold is a precious metal which is found in very small quantities in the gold mines, for this gold
mining operations are performed to extract or take out gold in the areas which further results in the
environmental damage in geographical term. The procedure of m mining is not easy but a difficult
process which releases and produces many other harmful and toxic pollutants (Ogwuegbu &
Muhanga,2005). Mining of gold is not an easy task, it negatively affects the environment and is
harmful to the environment when digging is done for mining of gold, in the deposition of the leftover
residue various chemicals are released which is also harmful (Afal & Wiener,2014).Chemical
processes are formed in the procedure of the gold mining or the process of extraction of gold. The
recent technique used for the extraction of gold from the gold mines is cyanide leaching which
consumes energy as well as water in very large quantity, it also puts in global warming, produces
wastage, discharges hydrogen cyanide. Air pollution, water and land all these are by-products of gold
mining when done with the method or technique of cyanide leaching technique. After the completion
of the process of gold mining often leads to the damage and destruction of the villages and the
communities have to relocate to a new location. Whole landscape gets disturbed by gold mining,
geographical stability gets imbalanced, the water table gets disturbed and the ecosystem. All this is
done because of the procedure of the removal large amount of ore to obtain gold. Water systems and

72
underground water get highly disturbed with mining of gold. All the wastage and toxic waste is
formed which is very harmful and hazardous for the environment. One more method is used before
digging of gold that is blast operation with the help of heavy vehicles which produces heavy noise,
and noise results in noise pollution. Mines can be open as well as underground, dust exposure is at
the same levels in both (Seyire,2005). This dust is very harmful, the workers who all are involved in
the process gets affected. Another pollution is the pollution of land which is the contamination of the
land by the wastage and the solid waste materials on land. Land pollution is the most harmful type of
pollution for the people who live in those polluted areas or in any particular polluted location. People
living on the polluted land, people gets sick, their organs gets damaged which sometimes results in
death. Pollution of air is when the toxic chemicals gets mixed and comes in contact in the
atmosphere, many harmful gases gets mixed in the environment (Ogwuegbu & Ijioma ,2003). All
the harmful gases enter into the atmosphere and cause acid rain, further results in global warming.
Open mining of gold disturbs the water level of the area around the pit because the water in the area
of the pit is emptied, and water is extracted and the area is dried to perform the operation. Cyanide is
very harmful for the fishes in the water. Open mines are easily polluted and affected badly.
PROCESSING PLANT
At the processing plant, with the technique of cyanide leaching, gold is extracted, in this
method ores are crushed and soaked in the solution of cyanide (Tarras & Wahlberga,2001) The
procession of ore involves the following steps that are : grinding and crushing of the ore, pumping of
the barren to the storage facility of tailings, adding water to form tailings, detaching the metals from
carbon with the help of acid wash and cyanide solution, adding carbon to dissolve metals and help in
further formation of the tailings, applying the electrowinning in the operation, adding lime to the ore
and solution of cyanide to extract gold from the solution, separating and forming metal products in
form of bars etc.
These stages in more detailed form is explained here under :
• Grinding and classification of the size of the ore which further transforms into fine particle
size (Aas & Breivik,2005).
• Absorbing and discharging procedure is done for the extraction of the precious metals from
the rock( Kumar & Abbas,2013).
• Mending of gold for the production of gold bars (Petruzelli, 2011).
PROCESS OF CRUSHING
The process of crushing by putting the ore in the hooper with the help of a loader, with heavy
speed and pressure the ore is then drawn towards the feeder and then moves towards the crushing
part. After the crushing part is done, then the crushing is moved to the jaw crusher and moved
immediately to the ball mill (Saxena & Misra,2010).
PROCESS OF GRINDING AND SIZING
In the process of grinding and sizing, categorization is done on the basis of the procedure of
the reduction of the ore to finest particle size. In this method or in this procedure the ore is directly
transferred from the jaw crusher to the ball mill. The ball mill has the maximum amount of share in
the steel balls which helps in the assistance in the grinding procedure (Flachier & Lanec,2001).
Water is added inside the ball mill and the reduction of the ore procedure starts. Cyclones are formed
after the discharge of the mill, then the cyclone gravity flows backwards for further grinding
procedure, it flows back to the leaching and the absorbing area also on the trash screen as well. For

73
obtaining the finest size of the precious metal from the ore, cyanide is required and is responsible
totally.
Figure 1: Plant for gold mining
PROCESS OF LEACHING, ABSORBING AND FILTERING
Leaching of the tanks and adsorption of the tanks with the cyanide solution is done to help in
the dissolving of the gold into the cyanide solution and changing the flow of the solution from the
last adsorption tank to the first adsorption tank. Carbon is mixed into the circuit of the tank in the
opposite direction so that gold particles move towards the surface of the carbon (Millard &
Neerchal,2001).The barren passes the adsorption tank to the filter needle tank, and then the filter
cake is dropped in the downward direction till the filter press on the ground, the barren slurry is
removed with the help of the front end loader, then it is loaded into trucks and later dumped into tails
dam and the gravity which has been filtered flows till the water process tank.

74
PROCESS OF ELUTION
Figure 2: Open Pit Figure 3: Jaw Crusher
Figure 4: Ball Mill
When the carbon gets loaded with the gold, the air gets lifted with the help of the first
adsorption tank, then it is pumped out with the help of the elution circuit, on the place where gold is
washed and heated with the help of water, the solution that is washed is then passed to the circuit
which is known as electro winning circuit. The carbon that is remained is again charged and
activated by washing it with acid and sent backwards to the last adsorption tank( Shrestha &
Kazama,2007). Original photographs of the open pit, ball mill and jaw crusher are shown here under:
MATERIALS AND METHOD
Study of the materials and method
Table 1: Sampling Location

75
Table 2: Heavy Metal concentration in soil samples
The plant is located in Oman, production of the gold per month is around 20 kg, where the pit
is a terrain which is mountainous with raw soil at the bottom of the pit, the raw soil is cut until it
reaches the ground water table (Michael,2013). Samples are arranged, collected and studied of
different areas which can be easily understood with the table shown below:
SAMPLING AND REAGENTS
Deionised ultrapure water that is 18 ohm-SG water, Germany has been used for mixing
samples and standards. Analytical grade is 37 percent HCL ( Aldrich) , nitric acid is 70 percent,
(Sigma Aldrich). ICP multi standards 1 and 2 used to make a curve of calibration which helps in
quantifying the samples (Park,2013). Microwave oven digestion proves as one of the appropriate tool
and technique for the identifying the samples from the complex matrices and is used in digestion of
ashed plants as well as samples of the soil. All the samples of soil and ashed plants are digested in
Teflon bombs by using the technique of EPA 30508 in microwave oven that is ETHOSEL,
Milestone Microwave System USA, on the set program of eight minutes in phase one as well as four
minutes in phase two at two hundred degree temperature. The digested samples are filtered with the
help of Whatman filter paper which is then transferred to hundred ml volumetric flask (Lanec,2001).
After the collection of the samples, the samples are studied with the help of PerkinElmer Inductively
Coupled Plasma-Optical Emission S spectrometer that is ICP-OES).All the remaining six blanks are
studied along with the samples which do not show any significant considerable or major
contamination ( Aster,2013). The samples of the plant are first air dried up, then grounded with the
help of the sieved and pestle as well as mortar (100 um). The sieved sample is further ashed into the
muffle furnace at five hundred degree temperature. At last acid is digested with the help of ultrapure
hydrochloric Thirthy seven percent as well as nitric acid seventy percent in same proportion in a
microwave oven in both first and second phases (Jung & Myung,1996).

76
DISCUSSION AND RESULTS
Table 3: Concentration of heavy metals in open pit
Table 4: Heavy metal concentration in crop plant

77
Table 5: Analysis of well water
Table 6: Analysis of water from acid evaporation and slurry sample
The trace elements are considered for the study of vanadium (V), barium (Ba), Iron (Fe),
Strontium (Sr), Aluminium (Al), Zinc (Zn), lead (Pb), Cobalt (Co), Cadmium (Cd), Nickel (Nil),
Manganese (Mn) and Chromium (Cr) (Pezzarossa & Gorini, 2011).In this research study , the feed
soil of the plant of gold is analyzed for the concentration of metal, which also gives indication of the
higher concentrations of iron that is 1.4 percent, aluminum that is 10.8 percent, manganese that is
0.29 percent and copper that is 0.32 percent, whereas with the lesser concentrations of cobalt, lead,

78
vanadium, chromium, zinc and nickel, shown in table 2. The mineral rocks contains appropriate
amount of sulphide minerals and pyrites, where sulphide minerals are harmful because they causes
oxidation of pyrites with formulation of the acid solutions on heavy metals, heavy metals become
highly mobile when acid rain occurs in the particular region. In the table 3, the analysis of soil and
water in open pit is shown in which light blue coloured surface water gets collected
(Agyemang,2010). There are very high concentrations of copper that is 4.4 percent. Open pit when
compared with the metal concentrations of the feed soil also have higher concentrations of cadmium,
lead, cobalt and molybdenum. The surface water is of light blue colour with high concentration of
copper. High residual concentration of aluminum, manganese, nickel, zinc, iron, cadmium, cobalt
and lead has been analyzed. When these metals such as cobalt, copper, lead, cadmium, zinc which
contains mine tailings comes in contact of the scarce rain fall water then it causes pollution in the
environment. After this process metals are leached out and then moved to downstream where the
water washes the tailings (Notman,2014). Whereas the metals become mobile in neutral pH
conditions, at that time leaching is accelerated in lower pH conditions for they are formulated in
metals solution (Cobbina & Myilla,2013). In table no. 4, analysis of same vegetation has been done
where the plants are taken near the gold pit and also the control plant is collected and gathered more
closer to the water well of the citizens about hundred meters in the north direction of the mine.
Analysis of the desert plant which is near to the gold pit shows increase in almost all of the trace
elements such as ( Fe, Mn, Al, Zn, Cu, Cr, Co, Ba, V, Ni) as well as lead decreases with
molybdenum concentrations on comparison with the desert plant (Essumang & Zugle,2010). In the
boron plant concentrations showed decrease by 1.77 percent to 0.07 percent when analyzed and
comparison performed to control. Even though the plants are collected and selected from the same
genus, and the metal immobilization capabilities are dependent on the availability of the metal
concentrations present in the soil because it is responsible for the explanation of growth and
difference between the metal concentrations (Saxena & Misra,2010). The concentrations of lead
around 80 mg Kg-1 has been keenly observed in the tailings with very high levels of lead in the
growing plants which are near to the gold mines or near to the gold mining area. The plants which
are downstream or little far from the gold mines have very less concentrations of heavy metals. From
this research study, it indicates that with the location of the plants, metal rich soils can be identified.
Toxic and heavy metals are present in all the plants but in different quantities and it totally depends
on the area. Humans near the mining area can get ample number of health problems and should keep
away from such toxic areas. The toxins enter the soil with the medium of heavy rains, then it enters
the water table and then it goes to the surface. Toxic metals like lead (Pb) with high concentrations
are not only present in the soil but also in the plants and the surroundings as well with the acid
evaporation ponds (Akabzaa & Seyire,2005).The soil contains very high amount of the metals which
is very harmful in spite of the excessive phytotoxicity presented in the soil (Duffus, 2002). The
citizens get water from the water resources which are located near about five hundred to one
thousand in the north direction in downstream of the mine which is up to Who standards and also up
to the Omani Standards of drinking water. The table number five shows the water samples and its
results acquired from the citizens of that location near about five hundred to one thousand meters to
the north side of the gold plant (Tetteh & Golow,2010).This water is used in agricultural purposes.
With the change in the chemical as well as change in the physical state the metal contaminants cause
soil substrate as well as ground water pollution which is very harmful. All the heavy metals in
tailings are transported and sent or dispersed to the accumulation of animals and plants and later on
passes from the food chain to the human beings (Thornton & Iain 1996). In the table number six, the
water analysis from the acid evaporation pond indicates and shows how the mining procedure adapts
certain measures to keep away the harmful toxins and prevent environmental pollution. From the
acid evaporation pond, samples are taken of the soil, other samples are taken from the slurry sample
from the tailing dump which are then studied and keenly observed which shows the concentrations of

79
the heavy metals such as lead, copper, zinc and copper (Bánfalvi, 2011). All these concentrations of
the toxins are transported downstream in the season of rains which are further transferred with the
help of human food chain and with the help of plants.
CONCLUSION
The main threat for the environment is the mineralized rocks which are exposed to open pits
and also exposed to the waste dumps. The chemistry of water studied in the area indicates that all the
materials have very high capacity of generation of acid drainage with the release of harmful elements
and other harmful toxins (Ezeh & Chukwu,2011)These harmful elements are ( Pb, Cd, Cu, Cr, Ni).
The high metal waters may contaminate the local groundwater with the help of solubillisation of the
metals which are toxicated metals. When the study in the area of the water chemistry performed,
then it showed that there is high capacity of acid drainage. The groundwater gets contaminated with
these heavy metals which are toxic. As per the standards of the WHO and Omani , the drinking water
with such high concentrations aluminum and heavy metals and toxics is very harmful and it must be
considered in the future prevention plans ( Banoeng-Yakubo,2005).Tailings are also very injurious to
health because of the presence of cyanide and high metal in it. Restriction on such area is must,
Contamination of the food chains can be stopped with a check on the presence of human beings or
any living beings near the mining area or location. When there is any absence of the toxins in the soil
then vegetation is at minimum risk n vice versa.
REFERENCES
1. Aas W, Breivik K (2005). Heavy metals and POP measurements 2003. Kjeller, Norwegian
Institute for Air Research (EMEP-CCC Report #9/2005).
2. Adimado A., A.; Amegbey N., A. (2003). Incidents of cyanide spillage in Ghana, Mineral
Processing and Extractive Metallurgy. (Trans. IMMC) 112, 2.
3. Afal A & Wiener SW 2014, Metal Toxicity, Medscape.org, viewed 21 April 2014
4. Agyemang, I. (2010) Population Dynamics and Health Hazards of Small Scale Mining
Activity in the Bolgatanga and Talensi-Nabdam Districts of the Upper East Region of Ghana.
Indian Journal of Science and Technology, 3.
5. Akabzaa, T. M., Banoeng - Yakubo, B. K. And Seyire, J. S. (2005): Impact of Mining
Activities on Water in the Vicinity of the Obuasi Mine.
6. Bánfalvi G 2011, 'Heavy Metals, Trace Elements and their Cellular Effects', in G Bánfalvi
(ed.), Cellular Effects of Heavy Metals, Springer, Dordrecht, pp. 3–28,ISBN 9789400704275
7. Cobbina, S.J., Myilla, M. and Michael, K. (2013) Small Scale Gold Mining and Heavy Metal
Pollution: Assessment of Drinking Water Sources in Datuku in the Talensi-Nabdam District.
International Journal of Scientific & Technology Research, 2, 96.
8. Duffus JH 2002, '"Heavy Metals"—A Meaningless Term?', Pure and Applied Chemistry, vol.
74, no. 5, pp. 793–807
9. Jung, Myung Chae; Thornton, Iain (1996). "Heavy metals contamination of soils and plants
in the viscinity of a lead-zinc mine, Korea". Applied Geochemistry 11: 53–59.
10. Kumar V, Abbas AK & Aster JC 2013, 'Environmental and nutritional diseases,' in V Kumar,
AK Abbas & JC Aster (eds), Robbins Basic Pathology, 9th ed., Elsevier, Philadelphia,
PA, ISBN 978-1-4377-1781-5
11. Meili M et al. (2003b). Critical loads and limits of heavy metals in ecosystems: some
Swedish contributions to European modelling efforts. Background document contributed to
the Editorial Meeting of the Expert Panel on Critical Loads of Heavy Metals under
UN/ECECLRTAP-ICP Modelling and Mapping, Paris, 9–10 April 2003.

80
12. Millard, S., P.; Neerchal, N., K. (2001). Environmental statistics with S-PLUS. CRC Press,
U.S.A
13. Notman N 2014, 'Digging Deep for Safer Water', Chemistry World, vol. 11, no. 4, pp. 54–57
14. Ogwuegbu MO, Ijioma MA (2003). Effects Of Certain Heavy Metals On The Population Due
To Mineral Exploitation. In: International Conference on Scientific and Environmental Issues
In The Population, Environment and Sustainable Development in Nigeria, University of Ado
Ekiti, Ekiti State, Nigerian, pp. 8-10
15. Ogwuegbu MOC, Muhanga W (2005). Investigation of Lead Concentration in the Blood of
People in the Copperbelt Province of Zambia, J. Environ. (1): 66 – 75.
16. Park CC 2013, Acid Rain: Rhetoric and Reality, Routledge, Abingdon, ISBN
9780415712767
17. Pezzarossa B, Gorini F & Petruzelli G 2011, 'Heavy Metal and Selenium Distribution and
Bioavailability in Contaminated Sites: A Tool for Phytoremediation', in HM
Selim, Dynamics and Bioavailabiliy of Heavy Metals in the Rootzone, CRC Press, Boca
Raton, FL, pp. 93–128, ISBN 9781439826225
18. Saxena P & Misra N 2010, 'Remediation of Heavy Metal Contaminated Tropical Land' in I
Sherameti & A Varma, Soil Heavy Metals, Springer-Verlag, Berlin, pp. 431–78, ISBN
9783642024351
19. Sengupta AK 2002, 'Principles of Heavy Metals Separation', in AK Sengupta
(ed.),Environmental Separation of Heavy Metals: Engineering Processes, Lewis Publishers,
Boca Raton, FL, ISBN 1566768845
20. Shrestha, S., & Kazama, F. (2007). Assessment of surface water quality using multivariate
statistical techniques: A case study of the Fuji river basin, Japan. Environmental Modelling
and Software 22: 464-475.
21. Tarras-Wahlberga, N.H.; Flachier, A.; Lanec, S.N.; Sangforsd, O. (2001). "Environmental
impacts and metal exposure of aquatic ecosystems in rivers contaminated by small scale gold
mining: the Puyango River basin, southern Ecuador".The Science of the Total
Environment 278: 239–261.
22. Tetteh, S., Golow, A.A., Essumang, D.K. and Zugle, R. (2010) Levels of Mercury, Cadmium
and Zinc in the Topsoil of Some Selected Towns in the Wassa West District of the Western
Region of Ghana. Soil and Sediment Contamination: An International Journal, 19, 635-643
23. Olade (2009) Dispersion of Cd, Pb and Zn in Soils and Sediments of a Humid Tropical
Ecosystem in Nigeria. In: Hutchinson, T.C., Ed., Lead, Mercury, Cadmium and Arsenic in
the Environment, John Wiley and Sons, New York.
24. WHO (2006) Guidelines for Drinking Water Quality. 4th Edition, World Health
Organization, Geneva.
25. Akabzaa, T.M., Banoeng-Yakubo, B.K. and Seyire, J.S. (2005) Impact of Mining Activities
on Water in the Vicinity of the Obuasi Mine. 79, 377-379.
26. Ezeh, H.N. and Chukwu, E.A. ( 2011) Small Scale Mining and Heavy Metals Pollution of
Agricultural Soils: The Case of Ishiagu Mining District, South Eastern Nigeria. Journal of
Geology and Mining Research, 3, 87-104.
27. Kpan, J.D.A. (2008) Studies on Levels of Mercury, Zinc and Cadmium in Soils in the
Vicinity of an Alluvial Goldmine at Dunkwa-on-Offin. Unpublished Thesis, University of
Cape Coast, Cape Coast.

Gold mines and impact of heavy metals on the environment

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

Similaire à Gold mines and impact of heavy metals on the environment

Similaire à Gold mines and impact of heavy metals on the environment (20)

Plus de IAEME Publication

Plus de IAEME Publication (20)

Dernier

Dernier (20)

Gold mines and impact of heavy metals on the environment