Khamis, 22 November 2012

LOGAM BERAT DI KERAK BUMI


LOGAM BERAT DI KERAK BUMI

Kandungan di bawah ini saja diambil dari wikipedia supaya kita berfikir. Firman Allah dalam Quran menyuruh manusia berfikir! Sekarang ini banyak sekali permukaan bumi digondolkan buat menjadi samada kawasan perumahan atau kawasan sawit atau getah. Masalahnya timbul apabila permukaan yang botak tidak lagi berupaya menghalang hakisan air hujan! Sebenarnya banyak logam berat terjadi secara semulajadi di atas permukaan bumi. Berbagai jenis logam berat ditahan dari pada masuk ke dalam sungai oleh rumput2, pokok pokok dan tumbuh tumbuhan di atas permukaan bumi. Sekiranya permukaan bumi telah digondolkan, apakah lagi daya yang dapat menahan logam berat yang memudaratkan kesihatan manusia daripada dihanyut masuk oleh hujan ke dalam aliran sungai? Sila lah ikuti ...

The Earth formed from the same cloud of matter that formed the Sun, but the planets acquired different compositions during the formation and evolution of the solar system. In turn, the natural history of the Earth caused parts of this planet to have differing concentrations of the elements. The mass of the Earth is approximately 5.98×1024 kg. It is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. Due to mass segregation, the core region is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.[10]

Earth's bulk (total) elemental abundance

 [show]Number
Name
Symbol
ppm (μg/g)
ppb (atoms)
8
oxygen
O
297000
482,000,000.00
12
magnesium
Mg
154000
164,000,000.00
14
silicon
Si
161000
150,000,000.00
26
iron
Fe
319000
148,000,000.00
13
aluminum
Al
15900
15,300,000.00
20
calcium
Ca
17100
11,100,000.00
28
nickel
Ni
18220
8,010,000.00
1
hydrogen
H
260
6,700,000.00
16
sulfur
S
6350
5,150,000.00
24
chromium
Cr
4700
2,300,000.00
11
sodium
Na
1800
2,000,000.00
6
carbon
C
730
1,600,000.00
15
phosphorus
P
1210
1,020,000.00
25
manganese
Mn
1700
800,000.00
22
titanium
Ti
810
440,000.00
27
cobalt
Co
880
390,000.00
19
potassium
K
160
110,000.00
17
chlorine
Cl
76
56,000.00
23
vanadium
V
105
53,600.00
7
nitrogen
N
25
46,000.00
29
copper
Cu
60
25,000.00
30
zinc
Zn
40
16,000.00
9
fluorine
F
10
14,000.00
21
scandium
Sc
11
6,300.00
3
lithium
Li
1.10
4,100.00
38
strontium
Sr
13
3,900.00
32
germanium
Ge
7.00
2,500.00
40
zirconium
Zr
7.10
2,000.00
31
gallium
Ga
3.00
1,000.00
34
selenium
Se
2.70
890
56
barium
Ba
4.50
850
39
yttrium
Y
2.90
850
33
arsenic
As
1.70
590
5
boron
B
0.20
480
42
molybdenum
Mo
1.70
460
44
ruthenium
Ru
1.30
330
78
platinum
Pt
1.90
250
46
palladium
Pd
1.00
240
58
cerium
Ce
1.13
210
60
neodymium
Nd
0.84
150
4
beryllium
Be
0.05
140
41
niobium
Nb
0.44
120
76
osmium
Os
0.90
120
77
iridium
Ir
0.90
120
37
rubidium
Rb
0.40
120
35
bromine
Br
0.30
97
57
lanthanum
La
0.44
82
66
dysprosium
Dy
0.46
74
64
gadolinium
Gd
0.37
61
52
tellurium
Te
0.30
61
45
rhodium
Rh
0.24
61
50
tin
Sn
0.25
55
62
samarium
Sm
0.27
47
68
erbium
Er
0.30
47
70
ytterbium
Yb
0.30
45
59
praseodymium
Pr
0.17
31
82
lead
Pb
0.23
29
72
hafnium
Hf
0.19
28
74
tungsten
W
0.17
24
79
gold
Au
0.16
21
48
cadmium
Cd
0.08
18
63
europium
Eu
0.10
17
67
holmium
Ho
0.10
16
47
silver
Ag
0.05
12
65
terbium
Tb
0.07
11
51
antimony
Sb
0.05
11
75
rhenium
Re
0.08
10
53
iodine
I
0.05
10
69
thulium
Tm
0.05
7
55
cesium
Cs
0.04
7
71
lutetium
Lu
0.05
7
90
thorium
Th
0.06
6
73
tantalum
Ta
0.03
4
80
mercury
Hg
0.02
3
92
uranium
U
0.02
0.002
49
indium
In
0.01
0.002
81
thallium
Tl
0.01
0.002
83
bismuth
Bi
0.01
0.001

An estimate[11] of the elemental abundances in the total mass of the Earth. Note that numbers are estimates, and they will vary depending on source and method of estimation. Order of magnitude of data can roughly be relied upon. ppb (atoms) is parts per billion, meaning that is the number of atoms of a given element in every billion atoms in the Earth.

Earth's crustal elemental abundance



 

Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number. The rarest elements in the crust (shown in yellow) are the most dense. They were further rarefied in the crust by being siderophile (iron-loving) elements, in the Goldschmidt classification of elements. Siderophiles were depleted by being relocated into the Earth's core. Their abundance in meteoroid materials is relatively higher. Additionally, tellurium and selenium have been depleted from the crust due to formation of volatile hydrides. This graph illustrates the relative abundance of the chemical elements in Earth's upper continental crust, which is relatively accessible for measurements and estimation. Many of the elements shown in the graph are classified into (partially overlapping) categories:

  1. rock-forming elements (major elements in green field, and minor elements in light green field);
  2. rare earth elements (lanthanides, La-Lu, and Y; labeled in blue);
  3. major industrial metals (global production >~3×107 kg/year; labeled in red);
  4. precious metals (labeled in purple);
  5. the nine rarest "metals" — the six platinum group elements plus Au, Re, and Te (a metalloid) — in the yellow field.

Note that there are two breaks where the unstable elements technetium (atomic number: 43) and promethium (atomic number: 61) would be. These are both extremely rare, since on Earth they are only produced through the spontaneous fission of very heavy radioactive elements (for example, uranium, thorium, or the trace amounts of plutonium that exist in uranium ores), or by the interaction of certain other elements with cosmic rays. Both of the first two of these elements have been identified spectroscopically in the atmospheres of stars, where they are produced by ongoing nucleosynthetic processes. There are also breaks where the six noble gases would be, since they are not chemically bound in the Earth's crust, and they are only generated by decay chains from radioactive elements and are therefore extremely rare there. The twelve naturally occurring very rare, highly radioactive elements (polonium, astatine, francium, radium, actinium, protactinium, neptunium, plutonium, americium, curium, berkelium, and californium) are not included, since any of these elements that were present at the formation of the Earth have decayed away eons ago, and their quantity today is negligible and is only produced from the radioactive decay of uranium and thorium.

Oxygen and silicon are notably quite common elements. They have frequently combined with each other to form common silicate minerals.

Rare-earth elemental abundance

"Rare" earth elements is a historical misnomer. The persistence of the term reflects unfamiliarity rather than true rarity. The more abundant rare earth elements are each similar in crustal concentration to commonplace industrial metals such as chromium, nickel, copper, zinc, molybdenum, tin, tungsten, or lead. The two least abundant rare earth elements (thulium and lutetium) are nearly 200 times more common than gold. However, in contrast to the ordinary base and precious metals, rare earth elements have very little tendency to become concentrated in exploitable ore deposits. Consequently, most of the world's supply of rare earth elements comes from only a handful of sources. Furthermore, the rare earth metals are all quite chemically similar to each other, and they are thus quite difficult to separate into quantities of the pure elements.

Differences in abundances of individual rare earth elements in the upper continental crust of the Earth represent the superposition of two effects, one nuclear and one geochemical. First, the rare earth elements with even atomic numbers (58Ce, 60Nd, ...) have greater cosmic and terrestrial abundances than the adjacent rare earth elements with odd atomic numbers (57La, 59Pr, ...). Second, the lighter rare earth elements are more incompatible (because they have larger ionic radii) and therefore more strongly concentrated in the continental crust than the heavier rare earth elements. In most rare earth ore deposits, the first four rare earth elements – lanthanum, cerium, praseodymium, and neodymium – constitute 80% to 99% of the total amount of rare earth metal that can be found in the ore.


Main article: Earth science


Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four solar terrestrial planets in size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity, the strongest magnetic field, and fastest rotation,[63] and is probably the only one with active plate tectonics.[64]

Chemical composition of the crust[74]
Compound
Formula
Composition
 
Continental
Oceanic
 
SiO2
60.2%
48.6%
 
Al2O3
15.2%
16.5%
 
CaO
5.5%
12.3%
 
MgO
3.1%
6.8%
 
FeO
3.8%
6.2%
 
Na2O
3.0%
2.6%
 
K2O
2.8%
0.4%
 
Fe2O3
2.5%
2.3%
 
H2O
1.4%
1.1%
 
CO2
1.2%
1.4%
 
TiO2
0.7%
1.4%
 
P2O5
0.2%
0.3%
 
Total
99.6%
99.9%
 

Chemical composition


The mass of the Earth is approximately 5.98×1024 kg. It is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. Due to mass segregation, the core region is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.[75]

The geochemist F. W. Clarke calculated that a little more than 47% of the Earth's crust consists of oxygen. The more common rock constituents of the Earth's crust are nearly all oxides; chlorine, sulfur and fluorine are the only important exceptions to this and their total amount in any rock is usually much less than 1%. The principal oxides are silica, alumina, iron oxides, lime, magnesia, potash and soda. The silica functions principally as an acid, forming silicates, and all the commonest minerals of igneous rocks are of this nature. From a computation based on 1,672 analyses of all kinds of rocks, Clarke deduced that 99.22% were composed of 11 oxides (see the table at right), with the other constituents occurring in minute quantities.[76]

Internal structure

Main article: Structure of the Earth

The interior of the Earth, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties, but unlike the other terrestrial planets, it has a distinct outer and inner core. The outer layer of the Earth is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity, and the thickness of the crust varies: averaging 6 km (kilometers) under the oceans and 30-50 km on the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, and it is of the lithosphere that the tectonic plates are comprised. Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 410 and 660 km below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core.[77] The inner core may rotate at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1–0.5° per year.[78]

 

 

 

Tiada ulasan:

Catat Ulasan

Nota: Hanya ahli blog ini sahaja yang boleh mencatat ulasan.

Catat Ulasan