Metal

Acid Mine Drainage (AMD) is presently the chief pollutant of surface H2O in the middle Atlantic part. AMD is caused when H2O flows over or through sulphur-bearing stuffs organizing solutions of net sourness. AMD comes chiefly from abandoned coal mines and presently active excavation. AMD degrades more than 4,500 watercourse stat mis in the middle Atlantic part with the loss of aquatic life, and restricts watercourse usage for diversion, public imbibing H2O and industrial H2O supplies (U.S. Environmental Protection Urgency, 2009:27)

South Africa is a water-stressed state. Security of H2O supply has become a cardinal strategic issue every bit good as driver for continued and sustained economic growing and service bringing to the people of South Africa. The South African excavation sector is one of the critical pillars and drivers of the South African economic system.

However, excavation activities are besides associated with environmental taint such as acid mine drainage (AMD). AMD is extremely acerb H2O, normally incorporating high concentrations of metals, sulfides, and salts as a effect of excavation activity. The major beginnings of AMD include drainage from belowground mine shafts, overflow and discharge from unfastened cavities and mine waste mopess, shadowings and ore reserves, which make up about 88 % of all waste produced in South Africa. Drain from abandoned belowground mine shafts into surface H2O systems (decant) may happen as the mine shafts fill with H2O. Although the chemical science of AMD coevals is straightforward, the concluding merchandise is a map of the geology of the excavation part, presence of microorganisms, temperature and besides of the handiness of H2O and O. These factors are extremely variable from one part to another, and, for this ground, the anticipation, bar, containment and intervention of AMD must be considered carefully and with great specificity.

The gold excavation industry in South Africa (chiefly the Witwatersrand Goldfield) is in diminution, but the post-closure decant of AMD is an tremendous menace, and this could go worse if remedial activities are delayed or non-implemented. For illustration, acid mine H2O started to pour from defunct flooded belowground mine workings near Krugersdorp on the West Rand in August 2002, taking to contaminated surface H2O. Randfontein and the Wonderfontein Spruit are besides debatable. These instances have received significant media attending, which has been critical of the attempts so far to turn to the jobs. In the absence of redress, there is likely to be well more decant in future, with potentially terrible deductions for aquatic systems.

AMD from coal excavation is debatable in the Highveld Coalfield in Mpumalanga, and has been reflected by media attending on the effects of terrible pollution seen in the Loskop Dam and the Olifants River Catchment. It is likely that new coal excavation in the Waterberg Coalfield (Limpopo Province) will take to similar jobs in that country in the hereafter (CSIR: Briefing Note 2009/02 August 2009)

Acid Mine Drainage

Mine drainage is metal-rich H2O formed from chemical reaction between H2O and stones incorporating sulphur-bearing minerals. The overflow formed is normally acidic and often comes from countries where ore or coal excavation activities have exposed stones incorporating fool’s gold, a sulfur bearing mineral. Metal-rich drainage can besides happen in mineralized countries that have non been mined.

Acid Mine Drainage occurs as follows:

• Mine drainage is formed when fool’s gold, an Fe sulfide, is exposed and reacts with air and H2O to organize sulfuric acid and dissolved Fe;
• Some or all of this Fe can precipitate to organize the ruddy, orange, or xanthous deposits in the underside of watercourses incorporating mine drainage;
• The acid overflow further dissolves heavy metals such as Cu, lead, quicksilver into land or surface H2O;
• The rate and grade by which acid-mine drainage returns can be increased by the action of certain bacteria.

Impacts of Acid Mine Drainage are as follows:

• Contaminated imbibing H2O;
• Disrupted growing and reproduction of aquatic works and animate beings
• Corroding effects of acid on parts of substructure such as Bridges

The badness of, and impacts from, AMD/ARD are chiefly a map of the mineralogy of the stone stuff and the handiness of H2O and O some dissolved metals may stay in solution. Dissolved metals in acid drainage may include lead, Cu, Ag, manganese, Cd, Fe, and Zn, among other metals. Elevated concentrations of these metals in surface H2O and groundwater can prevent its usage as imbibing H2O or aquatic home ground (Banister et al., 2002:4) .

Acid Drainage Generation

Acid is generated at mine sites when metal sulphide minerals are oxidized and sufficient H2O is present to mobilise the sulfur ion. Metal sulfide minerals are common components in the host stone associated with metal excavation activity.

Prior to excavation, oxidization of these minerals and the formation of sulfuric acid is a map of natural weathering procedures. The oxidization of undisturbed ore organic structures followed by the release of acid and mobilisation of metals is slow. Natural discharge from such sedimentations airss little menace to having aquatic ecosystems except in rare cases. Mining and mineral extraction operations greatly increase the rate of these same chemical reactions by taking big volumes of sulphide stone stuff and exposing increased surface country to air and H2O. Materials/wastes that have the possible to bring forth ARD as a consequence of metal excavation activity include mined stuff, such as spent ore from pile and dump leach operations, shadowings, and waste stone units, every bit good as overburden stuff. AMD coevals in the mines themselves occurs at the cavity walls in the instance of surface excavation operations and in the belowground workings associated with belowground mines.

The potency for a mine or its associated waste to bring forth acid and release contaminations depends on many factors and is site-specific. These site-specific factors can be categorized as coevals factors, control factors, and physical factors.

Coevals factors determine the ability of the stuff to bring forth acid. Water and O are necessary to bring forth acid drainage ; certain bacteriums enhance acerb coevals. Water serves as a reactant, a medium for bacteria, and the conveyance medium for the oxidization merchandises. A ready supply of atmospheric O is required to drive the oxidization reaction. Oxygen is peculiarly of import in keeping the rapid oxidization catalyzed by bacteria pH values below 3.5. Oxidation of sulfides is significantly reduced when the concentration of O in the pore infinites of mining waste units is less than 1 or 2 per centum. Different bacteria are better suited to different pH degrees and physical factors (discussed below). The type of bacteria and population sizes change as growing conditions are optimized (Wade et al, 2002:5)

Chemical control factors determine the merchandises of oxidization reaction. These factors include the ability of the coevals stone or having H2O to either neutralize the acid (positive consequence) or to alter the wastewater character by adding metals ions mobilized by residuary acid (negative consequence) . Neutralization of acid by the alkalinity released when acid reacts with carbonate minerals is an of import agencies of chairing acerb production and can function to detain the oncoming of acerb production for long periods or even indefinitely. The most common neutralizing minerals are calcite and dolomite. Merchandises from the oxidization reaction, such as H ions and metal ions, may besides respond with other non-neutralizing components. Possible reactions include ion exchange on clay atoms, gypsum precipitation, and disintegration of other minerals. The disintegration of other minerals contributes to the contaminant burden in the acid drainage. Examples of metals happening in the dissolved signifier include aluminum, manganese, Cu, lead, Zn, and others (Pulles et al. , 2005:7).

Physical factors include the physical features of the waste or construction, the manner in which acid-generating and acid-neutralizing stuffs are placed, and the local hydrology. The physical nature of the stuff, such as atom size, permeableness, and physical weathering features, is of import to the acerb coevals potency. Though hard to weigh, each of these factors influences the potency for acerb coevals and is, hence, an of import consideration for long term waste direction. Particle size is a cardinal concern because it affects

To look into the significance of metal bar during the Bronze Age within the Mediterranean trade industry.

Chapter I: Introduction

The significance of the metal bars in the Bronze Age has long been recognized in the development of metallurgical engineering, societal organisation and the primary focal point of this research, the Mediterranean trade industry.

The metal metal bars, peculiarly those made from Cu and Sn became an of import facet in the Bronze Age trade, as they were the majority of the ship ‘s lading. Furthermore the location of these metal ores occur in geographically localized countries, which would hold limited entree of prehistoric communities to metals, which hence encouraged long distance trade between them. ( Jones, 2007, 1 ) Copper was particularly an of import natural stuff as it was used for doing tools, arms and status-enhancing luxury goods. Furthermore, Cu was the chief constituent within the sea trade. Evidence found on Mesopotamia and Dilmun, Egypt, Levant, the Aegean and subsequently the cardinal Mediterranean suggests ladings were much easier to transport by sea than by overland. The shipwrecks at Uluburun ( c.1300B.C ) and Cape Gelidonya ( c.1200B.C ) provide direct grounds for the conveyance of Cu metal bars by sea. This has hence influenced Mediterranean civilizations to increase nautical trade and established interregional contacts for Cu and Sn entree. This besides applies for metals such as gold, Ag and led which besides played a function in long-distance trade, thought non in the same measures as Cu.

There have been many arguments for the exact nature of this trade. Muhly references that the metal metal bars would supply us “ a proper apprehension of the nature and the range of this trade. ” ( 1977, 73 ) However, we can non establish our hypothesis on understanding Bronze Age trade on the metal metal bars entirely as “ The metals trade would hold differed considerable in volume and organisation in different parts, depending on locally available resources, geographics, established trade paths, local metallurgical engineering, and assorted societal and political factors. ” ( Jones, 2007, 3 ) The most direct grounds for an analysis of early trade comes from Tell el Amarna. The three-hundred-eighty-two clay tabular arraies found within the metropolis, where records of elusive communicating with foreign powers. These clay tablets provide grounds that the function of the metal metal bars in the development of long-distance trade in metals varied over clip. However they provide no grounds for the beginnings of Sn and Cu which suggest that they must hold been imported from states such as Cyprus.

Cyprus is by and large known for its laterality within the Cu production. “ This historical state of affairs is well-known among Cypriot and Mediterranean archeologists, and the Cu ingots represent the terminal merchandise of a complex procedure affecting the excavation, smelting and casting of Cu. “ ( Knapp, Kassianidou, Donnelly, 2001, 204 ) However this ‘historical state of affairs ‘ was really complex and ill understood. Nevertheless the grounds shows that the Cypriots played a dominant function within the Cu industry. Sites, such as the Troodos Mountains in western and cardinal Cyprus, contained the largest measure of Cu ore in the Mediterranean ; therefore becomes an of import beginning within the Cu metallurgy in the Late Cypriot societies.

Other sites in Cyprus were besides important in understanding the Cu metallurgy. By the Late Cypriot period ( c.1400-1100B.C. ) many sites became affluent regional Centres ; sites such as Enkomi, Hala Sultan Tekke, Kition and several other colonies. These metropoliss were of import in understanding trade, due to their part in Cu production and export. These metropoliss nevertheless, did non bring forth any paperss affecting trade like the castles ; a few Bronze Age letterings found called ‘Cypro-Minoan ‘ . These were undeciphered syllabic books which have been suggested to incorporate economic texts, votive letterings, or for case the clay balls from Enkomi and Kition contained short fables. However a figure of archeologists believe that the map of these books is yet to be known. Nonetheless epigraphers suggested that these texts show marks from a Cypro-Minoan alphabet, which may be identified on trade points such as the Cypriot and Mycenaean clayware and a assortment of oxhide metal bars. This connexion between the books and the goods has late been well-established.

Equally of import as Cyprus was within the Cu production, archaeologists struggled to bring out grounds for Bronze Age smelting activities. Virtually all the scoria sedimentations discovered on the excavation countries dated to periods after the Bronze Age. “ While more grounds for Middle and Late Cypriot Cu excavation and metallurgical production is available today, unluckily this grounds is by and large fragmental and hard to construe. ” ( Jones, 2007, 6 )

However, the led isotope analysis proved to be really successful and accurate, as it measured the stable isotopes of lead utilizing a mass spectrometer in order to qualify peculiar samples. This method severally measured the samples ‘ radioactive concentration harmonizing to the geological age of the lead ores. This analysis would supply archeologists with near-conclusive grounds that Cypriot Cu was exported on a important graduated table. The chemical and metallographic analysis show high measures of pre Cu within the oxhide metal bars. This analysis suggests a high demand and production for Cu in the Bronze Age.

Another of import facet of Bronze Age trade were the shipwreck finds, particularly those found at Uluburun and Cape Gelidonya. Each of these shipwrecks provide of import information for the nature and organisation of the Cu trade within the period of 1300-1200B.C. The Uluburun and Cape Gelidonya ladings contained the largest measures of Cu metal bars, particularly Uluburun which about contained over 10 dozenss of Cu and one ton of Sn metal bars. The three-hundred and 54 metal bars found within this lading exceed old ladings found on land and on submerged sites. Other important goods found within the Uluburun lading include a big figure of glass metal bars, about one ton of terebinth rosin in Canaanite jars, Cypriot clayware in several pithoi, and a broad assortment of luxury goods plus other points such as the personal ownerships of the crew and riders which bordered the ship. These goods were besides notable as they are an indicant for directional trade ; points such as the Nefertiti Scarabaeus sacer.

On the other manus the Cape Gelidonya ship is significantly different. This complete digging contained in its vessel 34 complete Cu oxhide ingots every bit good as other ingot types. The Cape Gelidonya ship seems to hold a lower position that the Uluburun ship as it was a great trade smaller in size that the Uluburun ship and the goods it contained and transported have a lower value.

These shipwrecks raise a figure of theories which are of import in understanding Bronze Age trade. How important was the position of the goods found within the ladings? Are the smaller ladings, for case the one found at Cape Gelidonya, more typical that the larger 1s? How common was the transit of the Cu and Sn metal bars? How does this alter our position on the Bronze Age trade? This inquiry besides applies to land-based transit. The most appropriate would be that the production and circulation of metals occurred in several different ways to one another. However this response is really by and large used, as there are a figure of possibilities to differences between Cu and Sn metal bars. However the most dominant accounts are the fluctuations of trade mechanisms, the geological and geographical factors, the societal organisation of societies involved and the utilizations to which the metals were employed. These are a few of the accounts used to assist us associate Cu and Sn metal bars to Bronze Age trade and let us to understand the differences between each metal bar. Furthermore we could now do the theory that by analyzing these metal bars in deepness would let us to acknowledge the trade paths within the Mediterranean.

There are a scope of grounds which describe the trade and production of Cu, Sn and other metals in the Bronze Age. The most common are the textual grounds of Tell el Amarna, Mesopotamia, Aegean, Syria-Palestine and Anatolia. However the iconographic grounds is besides of equal importance as several civilizations such as the Egyptians, Cypriots and Mycenaean ‘s represented their oxhide metal bars in pictural signifiers. These “ Representations of oxhide metal bars demonstrate a cultural group ‘s acquaintance with Cu metal bars in this signifier and therefore their entree to interregional trade paths connected with the beginning or beginnings of Cu used to do oxhide metal bars. ” ( Jones, 2007, 9 ) Iconographic grounds such as the pictures and reliefs found at Sahure ‘s burial temple represent the ships ‘ crews. This provides information on the ship ‘s beginning and information on the different foreign groups involved within the Mediterranean trade.

INTRODUCTION

Lead is a type of metal that is extremely toxic. It is used in the industries for the manufacture of various products like paint, gasoline etc. The chemical is also a component of products like ammunitions and batteries. Lead is a problem because of its dangerous and irreversible hazards. In the industry for instance, workers who are in constant touch with paints and gases stand a high risk of illness as a result of this chemical. It also poses danger especially on children whose weak bodies become vulnerable due to the devastating effects of lead. The control of lead levels and exposure to materials containing the chemical is inevitable. But with the application of the OSHA standards, it is anticipated that employees would not find their way into contact with this material. These standards require that employers should make their workplaces free of lead and other hazardous materials.

Background

Lead is a bluish chemical (when fresh) but grey (when exposed to the atmosphere). Its usage traces back to more than 6000 years. The metal does not easily rust and is also a poor conductor of electricity. It is found in the earth’s crust as an ore together with their metals like copper and zinc.

Exposure to lead can lead to the damage of the nerves. It can also contribute to kidney problems especially nephrosis. Besides this, the chemical is also believed to be one of the greatest contributors to brain damages and also blood disorders. In children, an even low level of lead in their blood is harmful. It can cause retarded growth, IQ problems and hearing problems. It can ultimately lead to death of the infant.

Sampling methods

In order to find the lead levels in humans, sampling is carried out. Various methods are used like OSHA, MOSH, etc.

THE OSHA METHOD OF SAMPLING LEAD

This method incorporates filters that have got sampling pumps. After collection of these samples, analysis is done through emission spediometry or flame atomic absorption.

Detection of specific metals can be through minute or bunk quantities.

Tetramethyl and Tetraethyl compounds of lead can be analysed using In-House method as the stop gap procedure.

Advances in techniques and different levels of exposure limits may render a given OSHA method inapplicable.

The first step in analysis is to make bunk particles lesser i.e. grinding, or crushing to powder form. The samples are mixed with strong acid concentrates or if possible using de ionised water. The sample solution is then diluted, and exposed to atomic absorption or spectrophotometer rays.

Through the measure of characteristic wavelength, it is possible to determine the element but after atomization and achievement of the excited stage of the atoms.

Samples may be from the skin surface like the arms, hands or neck. A wise packet is torn open without touching the wire and given to the worker being evaluated. Employee is to remove the wipe from the package and unfold it. In the case of the hand, a person wipes the palms first and both sides of hand. This wiping is done for not less than 30 seconds using both sides of wire.

For samples not from the skin, gloved hands are used to open wipe packet and unfold the wire.

The designated surface for sampling is wired through repeated horizontal motions. The second wire is done at right angles to the first wire.

The designated surface for sampling is wiped through repeated horizontal motions. The second wire is done at right angles to the first wire.

It was noted that the employees did not wear separate work clothing or boots while at work. There is a common neglect of washing hands before drinking, eating or smoking. Some employees smoked near lead dust and fumes. Most of the times ,dry sweeping was done. The respirators worn at work were ill fitting, and worn out.

The Californian lead exposure for workers in workplaces shows only 2.7% of facilities have participated in lead environment monitoring, laboratory based surveillance for lead poisoning in employees may mislead on the number of employees exposed. The Californian facilities that use lead are about 53,000. Around 240,000 employees in these factories are in lead related plant processes. This is only about 2.5% of the total Californian work force.

Only 1.4% of lead- using process facilities and 2.6% facilities have the lead monitoring program. Employees in storage battery manufacture potentially exposed to lead are 1,950. Exposed individuals in the ship building repair, industry are 1,099 wending repair 312 people. Significantly 107,322 employees are exposed below lead action level. However, 88,262 are exposed above action level/

Table showing lead exposure levels in air sampling data:

The control measures recommended are to avoid spillage of lead-based oils and gasoline fumes be stored with facilities that have adequate ventilation systems. Lead process plants be enclosed and employees have sufficient respirator systems. Protective systems like using wet sweeping should be done and exposure to naked eye welding avoided. Consistent supervision, while encouraging minimum exposure to lead and prohibiting of eating, drinking, smoking or cosmetic application in the working place should be some of the control measures.

Administrative controls may target the schedule of working. Risk-prone, lead exposure e processes may be done when there are fewer workers at the facility. Also to protect the unborn, pregnant women may be assigned other work stages away from this (lead) contaminant.

CONCLUSION

The lead poisoning exposure levels are quite high given that about the employees exposed the results postulated show a figure that is not as accurate since less than half the facilities were sampled. Lead, a heavy metal is absorbed into the digestive system whenever inhaled. Smaller particles of lead reach deeper in the lungs into the broad system. Lead damages body ability to make red blood cells. Lead poisoning for the unborn and children can affect the child’s ability to use vitamin D and calcium. It can retard the kid’s brain, nervous system and red bone marrow.

Individuals having lead exposure levels that are active levels require chelate treatment.

Lead exposed men have been noted to have problems like low fertility, erectile dysfunction and brain defects. Among women, incidences of still births, miscarriages and social skill problems in the offsprings are rampant.

Substitution of lead for safer elements and change of process to minimize lead exposure for employees at the facility is necessary. Ventilation systems should be installed to reduce the amount of lead in air or dust. Isolation can be done by reducing the number of people present during lead processing. Good hygiene should be enforced. Most importantly, protective clothing, detection gadgets should be applied.

REFERENCES

Binns HJ, Kim D, Campbell C. Targeted screening for elevated blood lead levels: populations at high risk.2002, Mc ghill, USA. Gorstein J, Sullivan K, Yip R, et al. Issues in the assessment of nutritional status using anthropometry. Bull World Health Organ 1994; PubMed-Cental, USA.
United Nations System/Standing Committee on Nutrition. Nutrition information in crisis situations. Geneva, Switzerland: Secretariat of the UNS/SCN; May 2004.
US Consumer Product Safety Commission. Ban of lead-containing paint and certain consumer products bearing lead-containing paint, American public health Association, USA.
 

Important characteristics required for materials in Automotive Engineering Polymers have been used in the automotive industry for many decades. It is regarded as an efficient material as it is very durable and could significantly reduce production costs. However, as technology advances, new polymers are found and better alternatives are paved for the automotive industry. The vehicles we see today are very different than that of the yesteryears. This proves how far the automotive industry has advanced through technology. This eventually improved the built quality of vehicles in terms of safety, comfort, and performance.

Plastics have greatly contributed to the advancement of the automotive industry. Although some may perceive that plastics yield a poorer built quality (though in some cases, it may be true), it actually is a better alternative in an engineer’s point of view. The reason why we have a contrast of opinions regarding the use of plastics is because of the type of plastics being used. Therefore, the characteristics of the material are a very important factor in achieving good built quality. The automotive industry is constantly looking for alternatives to keep the production costs low.

In order to achieve that, the engineers adapted to the use of plastics on certain parts. The question was – was this a good idea? Over the years, it became evident that it really is. Hence, we see modern cars with plastic bumpers, plastic door handles, plastic mirror housing, etc. The engineers had to bear in mind that what they require is a durable and robust plastic material. They had to consider something that is able to deform upon minor collisions, and be able to return back to its original shape (reversibly deformable). The benefit of this idea is so that vehicle owners do not have to change the bumper for minor accidents.

However, plastics have a limit to their reversible-deformation property. It could tolerate impacts of up to a certain degree, but beyond that, it would be a permanent deformation. But then again, it is a lot better than to repair a bumper made of metal isn’t it? Thus, the bumpers are made of materials that are able to withstand light and medium impacts. Considering the fact that plastic parts are relatively lighter than metal or wooden parts, this would improve a vehicle’s performance, which will eventually make the machine more efficient.

As of today, plastic parts are known to be the most effective material that could save weight and yet be strong and durable. Cost has always been a challenge in the automotive industry. For many years, engineers have been working on alternative materials. A good example is the use of wood for certain parts like the steering. It would certainly be cheaper than steel, but come to think about the time taken to craft a circular shape out of wood, it would in the long run cost more than the latter.

Thus today, we find polymers used to replace these parts because it is in fact a lot cheaper and a lot easier to build. Some car owners of the 50’s and 60’s experienced this little problem when they park their cars out in the sun. They would return to their car and grab their stainless steel door handle and “ooh!! ”. Yes, it is a very good heat conductor. Very obviously, replacing a stainless steel door handle or gear knob or steering wheel with a plastic material is a brilliant idea. But the problem is whether or not it is able to withstand the heat.

Many first perceived plastic products to be inferior to high temperatures. However, technology proved them wrong. We have cars today with many plastic exterior parts that are able to withstand heat for years. It is indeed very important to analyze the feasibility of the use of a different material which has not been tested before. Many considerations are taken so that the parts used are well suited for its intended purpose. Plastics have proved to be a great alternative in automotive engineering, paving a bright path towards the future.