4 Chalcophile (As, Cd, Cu, Hg, Ni, Pb, Zn) …
63
The correlation analysis (see the Appendix, Tables A1 and A2) showed moderate
and significant correlations (r = 0.4 − 0.6, p < 0.05) of Mo with lithogenic elements
such as Zn, V, W, Li, Rb, Cs, Ca, Sr, LREE, Th and Fe by indicating strong effect
of long-range transport of the pollutants throughout the country. It shows weak and
significant correlation (r = 0.3 − 0.4, p < 0.05) with As, Cu, Pb, Sb, Cl, I and Se that
is probably derived by marine environment and geogenic factors of sulfide minerals.
Se shows weak and significant correlation (r = 0.3 − 0.4, p < 0.05) with V, Sb, Mo
and Sr. Selenium is probably affected by stronger impact of the marine environment
compared to the geogenic influences in moss samples.
4.9 Silver, Ag and Gold, Au
Ag is a naturally occurring rare element. The Ag content in the earth’s crust is
estimated as 0.07 mg/kg and is predominantly concentrated in basalt (0.1 mg/kg) and
igneous rocks (0.07 mg/kg) (Howe and Dobson 2002). It is often found in association
with other elements (ATSDR 1990) such as Cu, Ni, Pb and Zn ores, and Pt and Au
deposits. Silver is released to the environment by natural and anthropogenic sources,
long-range transport of fine particles in the atmosphere, wet and dry deposition, and
sorption to soils and sediments (ATSDR 1990). It may be emitted to the atmosphere
by anthropogenic sources such as coal burning, metal smelting, mining industry,
metal wastes disposal and photo-processing industry.
Gold (Au) is a noble element that is very scarce in the earth. It occurs in different
rocks and geological settings. Au is found as a free metal and almost associated with
pyrite and/or some other sulfides, and in the alluvial deposits (UNEP 2013). It is
extremely resistant to weathering and its content in the seawater ranged between 0.1
and 2 µg/L (UNEP 2013). The Au contents in moss samples varied from 0.00045 to
0.051 mg kg
−1 or 0.45 to 51 µg kg
−1 , with an average content of 0.0046 mg kg
−1 .
The concentration data of Au in moss samples of this study showed a high
disparity (CV% = 191%) followed by high positive values of skeweness and kurtosis.
Ag content in moss samples is more stable. Its contents varied from 0.036 to
0.451 mg kg
−1 , with an average content of 0.094 mg kg
−1 . The concentration data
of Ag show a moderate variation (CV% = 63%) followed by high positive values of
skeweness and kurtosis that indicate the data are skewed right. The spatial analysis of
Ag (Fig. 4.9a) and Au (Fig. 4.9b) show different distribution throughout the country.
Ag shows an increase from the south to the North (Ag = 0.0753 + 0.00046 × n)
with a strong anomaly at St. 30, Puka area, and two weak anomalies at St. 43 and
47. Au shows a decline from the south to the North (Au = 0.00777 − 0.000127 ×
n), with a strong anomaly at St. 8 and another one in St. 20 both in the vicinity of
oil and gas industry areas. All these findings are probably indicating Au and Ag are
mostly sourced from longe range transport of trace elements. Local anomalies of Au
are mostly originated from marine environment and geogenic factors. The median
concentration (0.084 mg kg1 ) of Ag is similar with Ag content in the earth’s crust
63
The correlation analysis (see the Appendix, Tables A1 and A2) showed moderate
and significant correlations (r = 0.4 − 0.6, p < 0.05) of Mo with lithogenic elements
such as Zn, V, W, Li, Rb, Cs, Ca, Sr, LREE, Th and Fe by indicating strong effect
of long-range transport of the pollutants throughout the country. It shows weak and
significant correlation (r = 0.3 − 0.4, p < 0.05) with As, Cu, Pb, Sb, Cl, I and Se that
is probably derived by marine environment and geogenic factors of sulfide minerals.
Se shows weak and significant correlation (r = 0.3 − 0.4, p < 0.05) with V, Sb, Mo
and Sr. Selenium is probably affected by stronger impact of the marine environment
compared to the geogenic influences in moss samples.
4.9 Silver, Ag and Gold, Au
Ag is a naturally occurring rare element. The Ag content in the earth’s crust is
estimated as 0.07 mg/kg and is predominantly concentrated in basalt (0.1 mg/kg) and
igneous rocks (0.07 mg/kg) (Howe and Dobson 2002). It is often found in association
with other elements (ATSDR 1990) such as Cu, Ni, Pb and Zn ores, and Pt and Au
deposits. Silver is released to the environment by natural and anthropogenic sources,
long-range transport of fine particles in the atmosphere, wet and dry deposition, and
sorption to soils and sediments (ATSDR 1990). It may be emitted to the atmosphere
by anthropogenic sources such as coal burning, metal smelting, mining industry,
metal wastes disposal and photo-processing industry.
Gold (Au) is a noble element that is very scarce in the earth. It occurs in different
rocks and geological settings. Au is found as a free metal and almost associated with
pyrite and/or some other sulfides, and in the alluvial deposits (UNEP 2013). It is
extremely resistant to weathering and its content in the seawater ranged between 0.1
and 2 µg/L (UNEP 2013). The Au contents in moss samples varied from 0.00045 to
0.051 mg kg
−1 or 0.45 to 51 µg kg
−1 , with an average content of 0.0046 mg kg
−1 .
The concentration data of Au in moss samples of this study showed a high
disparity (CV% = 191%) followed by high positive values of skeweness and kurtosis.
Ag content in moss samples is more stable. Its contents varied from 0.036 to
0.451 mg kg
−1 , with an average content of 0.094 mg kg
−1 . The concentration data
of Ag show a moderate variation (CV% = 63%) followed by high positive values of
skeweness and kurtosis that indicate the data are skewed right. The spatial analysis of
Ag (Fig. 4.9a) and Au (Fig. 4.9b) show different distribution throughout the country.
Ag shows an increase from the south to the North (Ag = 0.0753 + 0.00046 × n)
with a strong anomaly at St. 30, Puka area, and two weak anomalies at St. 43 and
47. Au shows a decline from the south to the North (Au = 0.00777 − 0.000127 ×
n), with a strong anomaly at St. 8 and another one in St. 20 both in the vicinity of
oil and gas industry areas. All these findings are probably indicating Au and Ag are
mostly sourced from longe range transport of trace elements. Local anomalies of Au
are mostly originated from marine environment and geogenic factors. The median
concentration (0.084 mg kg1 ) of Ag is similar with Ag content in the earth’s crust