What is lead?
Lead is a dense metal that is resistant to corrosion and is easily molded and shaped. Its atomic number is 82 and its chemical symbol on the periodic table is Pb, an abbreviation of plumbum. It appears as a silvery metal with a slight shade of blue. Rare in its pure form, lead is usually found in galena (lead sulfide; PbS), anglesite (lead sulfate; PbSO4), cerussite (lead carbonate; PbCO3), and mimetite(Pb5(AsO4)3Cl).
What is it used for?
Lead has been used by humans since ancient times. Lead was used in water pipes during the age of the Roman Empire and in the cosmetic kohl, which the ancient Egyptians used to darken their eyelids.
Before the 1900's the United States used lead in ammunition, ceramic glazes, paint, pewter, and water lines and pipes. After World War I, the use of lead rose with the production of motorized vehicles, which used lead-acid batteries. It was also used as radiation shielding in medical analysis and video display equipment and as a part of gasoline. Later on, in the 1980's, the use of lead changed in compliance with environmental regulations being put into action. Lead was replaced by other materials in gasoline, paint, and water systems.
Today, lead is more commonly used lead-acid batteries, ammunition, and oxides in glass and ceramics. The video below describes some of lead's other properties and uses.
Before the 1900's the United States used lead in ammunition, ceramic glazes, paint, pewter, and water lines and pipes. After World War I, the use of lead rose with the production of motorized vehicles, which used lead-acid batteries. It was also used as radiation shielding in medical analysis and video display equipment and as a part of gasoline. Later on, in the 1980's, the use of lead changed in compliance with environmental regulations being put into action. Lead was replaced by other materials in gasoline, paint, and water systems.
Today, lead is more commonly used lead-acid batteries, ammunition, and oxides in glass and ceramics. The video below describes some of lead's other properties and uses.
Where is lead found?
Lead is found in the Earth's crust at about 130 parts per million. Lead is produced mainly in Australia, China, the United States, Canada, Mexico, Peru, and Sweden. 90% of lead in the United States comes from Missouri.
Lead is obtained mainly from three types of deposits-that will be explained below.
Sedimentary Exhalative (SedEx) Deposits
More than 50% of the world's lead comes from these deposits. They are formed when hot liquids rich in metal are released into a water-filled basin (usually an ocean) or in basin sediments, which results in the precipitation of ore-bearing material within basin-floor sediments. A notable example of this type of deposit is the Sullivan Mine in Kimberly, British Columbia in Canada.
Mississippi Valley Deposits
These deposits, less commonly called carbonate hosted lead zinc ore deposits, are found throughout the world and get the name "Mississippi Valley from deposits that occur in the Mississippi Valley region of the United States. The deposits are set apart by ore mineral replacement of the carbonate host rock; they are often found in a single stratigraphic layer and extend over hundreds of square kilometers. Mississippi deposits were a major source of lead in the United States from the 19th century through the mid-20th century. An important example of this type of deposit is the Southeast Missouri Lead District, also known as the Lead Belt. It produces around 70% of the United State's primary lead supply.
Volcanogenic Massive Sulfide Deposits
In contrast to SeDex and Mississippi deposits, volcanogenic massive sulfide (VMS) deposits have a clear association with submarine volcanic processes. They also can bear impressive amounts of copper, gold, and silver, and zinc, aside from lead. The "black smoker" sea vents discovered during deep ocean expeditions are examples of VMS deposits being formed on the sea floor today. A notable example of this type of deposit is the Wolverine deposit of Yukon, Canada.
Lead is obtained mainly from three types of deposits-that will be explained below.
Sedimentary Exhalative (SedEx) Deposits
More than 50% of the world's lead comes from these deposits. They are formed when hot liquids rich in metal are released into a water-filled basin (usually an ocean) or in basin sediments, which results in the precipitation of ore-bearing material within basin-floor sediments. A notable example of this type of deposit is the Sullivan Mine in Kimberly, British Columbia in Canada.
Mississippi Valley Deposits
These deposits, less commonly called carbonate hosted lead zinc ore deposits, are found throughout the world and get the name "Mississippi Valley from deposits that occur in the Mississippi Valley region of the United States. The deposits are set apart by ore mineral replacement of the carbonate host rock; they are often found in a single stratigraphic layer and extend over hundreds of square kilometers. Mississippi deposits were a major source of lead in the United States from the 19th century through the mid-20th century. An important example of this type of deposit is the Southeast Missouri Lead District, also known as the Lead Belt. It produces around 70% of the United State's primary lead supply.
Volcanogenic Massive Sulfide Deposits
In contrast to SeDex and Mississippi deposits, volcanogenic massive sulfide (VMS) deposits have a clear association with submarine volcanic processes. They also can bear impressive amounts of copper, gold, and silver, and zinc, aside from lead. The "black smoker" sea vents discovered during deep ocean expeditions are examples of VMS deposits being formed on the sea floor today. A notable example of this type of deposit is the Wolverine deposit of Yukon, Canada.
How is lead mined?
Lead is mined through the typical way that comes to mind when people think of mining. Usually underground mines are established, with shafts leading to the surface for entry and movement of materials. Lead can also be mined on the surface. Deposits of lead can be found by observing where plant life struggles to survive. This may point to the presence of lead, as it is poisonous to most life. Lead is also found in other mines intended for different resources.
How does lead mining affect the environment?
Lead mining requires the disruption of the disruption of the area around where it is mined, whether it be near the surface or deep underground. On the surface, vegetation is cleared to make room for mining equipment. Underground, the solid foundation is damaged. There is also waste produced from the process of lead mining and separating lead from the ore it is in.
What are the effects of lead on people?
Most of lead exposure occurs due to water systems containing pipes made of lead. Undesirable levels of lead in the bodies of children can lead to permanent damage to the brain and nervous system, which can lead to learning and behavior problems, lower IQ, and hearing problems. In pregnant women, it can lead to reduced growth of the fetus, premature birth, and miscarriage. In adults, it can lead to nervous system effects, cardiovascular problems such as blood pressure, decreased kidney function, and reproductive problems. All of this has lead to regulations being enforced to reduce exposure to lead in everyday life. A specific example being the regulations on lead paint on children's toys.
Works Cited
http://geology.com/usgs/lead/
http://www.enotes.com/lead-reference/lead-177335
http://www.epa.gov/lead/learn-about-lead.html#found
http://www.lenntech.com/periodic/elements/pb.htm
http://education.jlab.org/itselemental/ele082.html
http://www.infomine.com/minesite/minesite.asp?site=mountisa
http://portal.hud.gov/hudportal/HUD?src=/program_offices/healthy_homes/enforcement/regulations
http://www.enotes.com/lead-reference/lead-177335
http://www.epa.gov/lead/learn-about-lead.html#found
http://www.lenntech.com/periodic/elements/pb.htm
http://education.jlab.org/itselemental/ele082.html
http://www.infomine.com/minesite/minesite.asp?site=mountisa
http://portal.hud.gov/hudportal/HUD?src=/program_offices/healthy_homes/enforcement/regulations