6 Source and Fate of Perchlorate in the Environment: A Grave …
139
In this chapter, different aspects of ClO 4
− such as (a) brief history of ClO 4
−
contamination; (b) sources of ClO 4
− : natural and anthropogenic; (c) fate of ClO 4
−
in water; (d) probable effect of ClO 4
− on different life forms; (e) standard and
measuring methods for ClO 4
− and (f) its degradation and remediation strategies
have been discussed.
6.2 Brief History of Perchlorate Contamination
In 1985, ClO 4
− was first detected in wells at industrial sites in California, USA. But
it was first observed as a chemical of concern in 1996, when fertilizers containing
NaClO 4 and KClO 4 have negative health impact on certain agricultural crops (Nzengung et al. 1999). From 1997 onwards, with advancement of more sophisticated
analytical methods, detection and identification of ClO 4
− in groundwater, surface
water, soil and food become easier (Rice et al. 2007).
6.3 Origin and Sources of Perchlorate
By origin, ClO 4
− is either natural or synthetic and is either naturally occurring chemical substance or chemical derivative of anthropogenic activities. Natural ClO 4
−
assemblages are mostly found in arid and semi-arid regions of earth (Rao et al. 2007)
and are of atmospheric or geogenic in origin (Cao et al. 2019). In arid and semi-arid
regions, due to less precipitation, net infiltration is also less, and therefore, mobilization of ClO 4
− to groundwater is restricted. In addition, higher evapotranspiration
rate leads to higher ClO 4
− accumulation on the ground of semi-arid and desert parts
of the world compared to other regions (Albright et al. 2008).
6.3.1 Natural Perchlorate
6.3.1.1 Origin and Occurrence
Natural atmospheric process is responsible for formation of natural ClO 4
− . Most
probably the chloride in the form of NaCl from sea or terrestrial chloride composites
blown towards atmosphere, and photochemically reacts with atmospheric ozone to
produce ClO 4
− (Trumpolt et al. 2005). In the marine environment, the photolysis
of ozone occurs in the presence of sea salt which is expected to create chlorine
(Cl 2 ) and hypochlorous acid (HOCl) (Oum et al. 1998). In the course of time, the
chlorate (ClO 3
− ) formation has been predicted in the stratosphere (Von Clarmann
2013). The formation of hypochlorite radicals (OCl
− ) occurs when molecular chlorine (Cl 2 ) dissolute in water (Siddiqui 1996). The addition of oxygen molecule to
139
In this chapter, different aspects of ClO 4
− such as (a) brief history of ClO 4
−
contamination; (b) sources of ClO 4
− : natural and anthropogenic; (c) fate of ClO 4
−
in water; (d) probable effect of ClO 4
− on different life forms; (e) standard and
measuring methods for ClO 4
− and (f) its degradation and remediation strategies
have been discussed.
6.2 Brief History of Perchlorate Contamination
In 1985, ClO 4
− was first detected in wells at industrial sites in California, USA. But
it was first observed as a chemical of concern in 1996, when fertilizers containing
NaClO 4 and KClO 4 have negative health impact on certain agricultural crops (Nzengung et al. 1999). From 1997 onwards, with advancement of more sophisticated
analytical methods, detection and identification of ClO 4
− in groundwater, surface
water, soil and food become easier (Rice et al. 2007).
6.3 Origin and Sources of Perchlorate
By origin, ClO 4
− is either natural or synthetic and is either naturally occurring chemical substance or chemical derivative of anthropogenic activities. Natural ClO 4
−
assemblages are mostly found in arid and semi-arid regions of earth (Rao et al. 2007)
and are of atmospheric or geogenic in origin (Cao et al. 2019). In arid and semi-arid
regions, due to less precipitation, net infiltration is also less, and therefore, mobilization of ClO 4
− to groundwater is restricted. In addition, higher evapotranspiration
rate leads to higher ClO 4
− accumulation on the ground of semi-arid and desert parts
of the world compared to other regions (Albright et al. 2008).
6.3.1 Natural Perchlorate
6.3.1.1 Origin and Occurrence
Natural atmospheric process is responsible for formation of natural ClO 4
− . Most
probably the chloride in the form of NaCl from sea or terrestrial chloride composites
blown towards atmosphere, and photochemically reacts with atmospheric ozone to
produce ClO 4
− (Trumpolt et al. 2005). In the marine environment, the photolysis
of ozone occurs in the presence of sea salt which is expected to create chlorine
(Cl 2 ) and hypochlorous acid (HOCl) (Oum et al. 1998). In the course of time, the
chlorate (ClO 3
− ) formation has been predicted in the stratosphere (Von Clarmann
2013). The formation of hypochlorite radicals (OCl
− ) occurs when molecular chlorine (Cl 2 ) dissolute in water (Siddiqui 1996). The addition of oxygen molecule to