and leads to chromium pollution of water in and around the area (CGWB 2014).
1.6.3.1 Health Impact
Chromium (III) has a particular transportation mechanism; because of this, only limited quantities of it pass in the cells. However, numerous in vitro studies specified that higher levels of Cr (III) in the cell could cause DNA impairment. Reasonable uptake of Cr (III) via dietary supplements causes no risk, whereas its severe oral toxicity varies between 1.5 and 3.3 mg/kg.
The severe toxicity of chromium (VI) is because of its strong oxidation properties. Once it enters the bloodstream, it harms the kidneys, the liver, and blood cells by oxidation reactions (CGWB 2014). Excess Cr (VI) can cause damage to the nervous system, fatigue, irritability, skin allergies, dermatitis, dermal necrosis, and dermal corrosion (Singh et al. 2011).
1.6.4 Remediation of Heavy Metals
Heavy metal can be eliminated from groundwater by applying various chemical, biological/biochemical, and physicochemical remediation technologies. Chemical methods include a reduction (by using dithionites, H2S gas, iron‐based technologies such as zerovalent ion, iron salts), chemical flushing (using soil washing, chelate flushing, ion exchange) and in situ chemical fixation. Biological/biochemical remediation has been carried out by biological activity in the subsurface, biosorption (by using biosurfactant, metal uptake by the organism, cellulosic material and agricultural wastes) and enhanced bio restoration. Physico‐chemical remediation applied by using adsorption/absorption/filtration (using surfactants, membrane separation, synthetic activated carbon, industrial byproducts and waste, ferrous materials, iron‐based soil amendments, mineral products), electrokinetic treatment and permeable reactive barriers, which include sorption (in red mud, activated carbon, zeolite, iron sorbent), precipitation via zero‐valent ion, complexing agents, atomized slag, caustic magnesia, and biological barriers (denitrification and sulphate reduction, microbes) (Hashim et al. 2011).
1.7 Selenium
Selenium is a crucial element, but at higher concentrations, it is toxic (Sharma et al. 2015). Natural sources of Se account for 50–65% of total emissions, globally. Natural sources of atmospheric selenium are crustal erosion, which causes its suspension in soil and dust, biologically originated volatile organo‐selenium compounds, volcanoes, and aerosol particles related with sea spray (Nriagu and Pacyna 1988; Sharma et al. 2015). Sedimentary rocks have a higher concentration of Se than the igneous rocks. Its concentrations in underlying rocks are strongly correlated with its concentration in soils. Soils rich in Se are frequently originated from marine deposits. In the oxic environment of surface soils, the main species of Se are selenite (Se (IV)) and selenate (Se (VI)) (Sharma et al. 2015).
It is a minor constituent of natural waters, and its level in water is generally found to be less than 10 mg/L (Sohrin and Bruland 2011). Laboratory studies suggested that a nonvolatile dimethyl selenonium ion can probably be changed into volatile dimethyl selenide at neutral pH (Cooke and Bruland 1987). This can be attributed as its pathway for the in‐situ origin of dimethyl selenide in natural waters. Selenium chemistry in groundwater is controlled by four crucial variables. These are the prime source, the transportation in solution, the courses of mobilization, and retaining at the water–solid interface and its level in groundwater under a semiarid and arid environment (Nicolli et al. 2012). Selenium in groundwater is restricted to particular locations and has been reported from dispersed areas in Himachal Pradesh and Punjab (CGWB 2014; Lapworth et al. 2017).
1.7.1 Health Impact
It has been observed that acute oral doses of selenite and other selenium compounds cause symptoms such as nausea, diarrhoea, abdominal pain, chills, tremor, numbness in limbs, irregular menstrual bleeding, and marked hair loss. The higher level of selenium in humans leads to hair loss and nail drop, whereas in plants, it causes snow‐white chlorosis which appears on juvenile leaves and sheaths. Some of these leaves changed to light pink or developed purple‐white tips having green mid‐veins (Aulakh et al. 2009). In northwestern India, its toxicity caused snow‐white chlorosis in wheat and sugar cane while chronic selenosis in faunas and humans (CGWB 2014).
It accumulates in the tissues of organisms and shows the biomagnification at a higher trophic level. Se accumulates in the animals when they ingest large quantities of plants that are uptaking higher concentrations of selenium. In many areas, Se concentration is found to be very high in aquatic organisms because of irrigation runoff. Selenium could cause reproductive failure and birth imperfections at an elevated concentration in animals. The most reliable clinical appearance indicated by animals is losing body state and hair loss, necrosis of the tip of the tail, reluctance to move, stiff gate, and overgrowth of hoof followed by progress of cracks and irregularities in horn development. Food or water are common exposure pathways of selenium in human beings. Typical symptoms of selenium toxicity in humans are hair and finger‐ and toenail loss, continuous worsening of health, queasiness, headache, tooth deterioration, tint of teeth, and nails with fragility and longitudinal strips (CGWB 2014).
Table 1.1 Geogenic contaminants in different parts of the country (India).
| Study area | As | F | SO4 | Na | Cl | Se | Cr | Mn | Fe | References |
|---|---|---|---|---|---|---|---|---|---|---|
| Cuttack City, Odisha, India | 0.03–1.5 ppm | Achary (2014a) | ||||||||
| Bhuvaneshwar City, Odisha, India | 0.32–7.7 ppm | Achary (2014a) | ||||||||
| Gangetic Plain, Jharkhand, India | 1–133 ppb in premonsoon, 2–98 ppb in monsoon and 7–115 ppb in postmonsoon | Alam et al. (2016) | ||||||||
| Punjab, India | 4–688 ppb | 0–10.09 ppm | 0.2–69.5 ppb | Aulakh et al. (2009) | ||||||
| Tripura, India | 0.025 ppm | 58.53 ppm |
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