Cation and Anion

Calculating the cation–anion balance is used to examine the precision of chemical analyses of water samples. The sum of the major anions the sum of major cations should be equal. This examination is usually performed by calculating the ionic balance error of the major ions where (Hiscock, 2009):

An ionic balance error of less than 5% and certainly less than 10% is achievable with modern analytical equipment. Larger errors suggest that one or more analyses are in error and consequently, they are not acceptable.

3.4.2.2.1 Major Cations

1 Calcium

Calcium (Ca) is available in all water sources due to its abundance on the earth

which is around 4.9% of the Earth’s crust. The Ca concentrations are commonly less

than 20 mg/L in groundwater but it can reach as high as 200 mg/L and ~400 mg/L in seawater. Concentrations of Ca in surface water change greatly. Calcium is known as one of the essential elements for humans and plants. Direct toxic impacts related to high concentration of Ca in water are not observed except in drinking water, high concentration of Ca may cause to increase kidney stones’ risk (Li et al., 2010).

2 Iron

One of the most abundant metals on the crust of the Earth is Iron (Fe) that is found in natural fresh waters at levels varying from 0.5 to 50 mg/L (World Health Organization, 2004). Fe can be found in drinking water due to using iron coagulants or the corrosion of steel and cast iron pipes through water distribution. Dissolution of iron- containing minerals, and human activities and the decay of organic matters can be caused to the existence of Fe in water. Fe is known as an essential element in human nutrition, which particularly is in the iron oxidation state.

Dissolved Fe in groundwater is determined by the amount of oxygen in the water level of acidity. In deep aquifers, especially when the aquifer consists of organic matter,

the dissolved oxygen amount is commonly low. The decomposition of the organic matter depletes the oxygen in the water and the iron is dissolved as Fe2+. The dissolved iron is mostly accompanied by dissolved hydrogen sulphide or manganese, under this condition. If this water is excavated to the surface, the dissolved iron and oxygen reaction occurs in the environment, varies to Fe3+ and rust- colour iron minerals is formed (Drever, 1997).

3 Magnesium

The eighth most abundant natural element is Magnesium (Mg) that exists in all natural waters as one of the main cations in water. Mg is known as a one of main contributors to hardness of water. 2.5% of the crust of Earth contains Mg and is generally obtained in such minerals

The erosion of rocks for instance limestone and dolomite, and minerals, such as calcite and magnetite is the most typical source of magnesium in groundwater.

4 Sodium

Sodium (Na) is a highly soluble chemical element which is naturally found in groundwater. In water, Na has no smell although it may be tasted by most people at contents of 200 milligrams per liter (mg/L) or more. Pollution from point or non-point sources or salt water intrusion may occur with increasing of sodium in groundwater above ambient or natural degrees. Some sodium exists in all groundwater because most rocks and soils consist of sodium compounds because sodium is easily dissolved. There are common sources of elevated sodium levels in groundwater which are a) Erosion of salt deposits and sodium bearing rock minerals, b) Natural occurrence of brackish water of some aquifers naturally, c) Intrusion of salt water into wells in coastal areas, d)

Infiltration of surface water which is contaminated by road salt, e) Irrigation and precipitation leaching through soils which are high in sodium, f) Pollution of groundwater by sewage effluent, g) Infiltration of leachate from industrial.

5 Potassium

Potassium (K) is an important element for humans and is rarely, if ever, present in drinking water at degrees that is significant for humans health. Potassium exists broadly in the environment which consists of all natural waters. It considers also as a result of the use of potassium permanganate as an oxidant in water treatment, in drinking water (World Health Organization, 2004). Potassium exists usually in rocks and soils which includes appreciable content of clay. Dissolution of rocks release sodium and potassium slowly upon. Moreover, potassium is a significant element in chemical fertilizer (Yang et al., 2006). Though potassium can cause some health impacts in sensitive individuals, its consumption through drinking water is approved below the level at which adverse health effects may occur. Health issues would be dependent on the intake of drinking water that is potassium-based water treatment (World Health Organization, 2004).

3.4.2.2.2 Major Anions

1 Chloride

One of important anions in water is Chloride (Cl) and the salts of hydrochloric acid HCl include chloride ions and can also be known as chlorides. The concentrations of Cl are generally less than 100 mg/L in groundwater and its concentration can be as high as 19,000 mg/L in seawater (Boyd, 2000). Concentrations of Cl > of 250 mg/L are progressively likely and detectable by taste.

High Cl concentrations in the groundwater and surface water happen frequently due to the intrusion of saltwater, industrial and homemade wastes and dissolution of mineral. When Cl is combined with Na, chloride causes to increasing a salty taste to drinking water and it results in increasing the corrosiveness of water. Human health is not influenced by normal concentrations of chloride, although increasing salinity can have effects on freshwater aquatic organisms (Li et al., 2010).

In addition, Cl is applied as a reliable chemical indicator of river / groundwater faecal contamination because it is a ubiquitous and non-reactive solute to sewage and potable water.

2 Sulphate

Sulphur (S) and oxygen (O) build up Sulphate (SO42-) composition. Sulphate is

naturally in many formations of soil and rock. Moreover, human activities may be caused existing of sulphate in well water. Most sulphates in groundwater are produced from the minerals dissolution, such as gypsum and anhydrite. The intrusion of saltwater and drainage of acid rock are also found as sulphates sources in drinking water. Taste of water may change with presence of above 500 mg/L of sulphate in water. Sulphate in drinking water can have a laxative effect when it exceeds 1000 mg/L, though these degrees are not usually available in drinking water.

3 Nitrate

Nitrate (NO3-) as an important plant nutrient is available naturally in the

environment. It is a part of the nitrogen cycle and exists at changing contents in all the plants. Nitrate concentrations are generally less than 2 mg/L in natural groundwater and its contents can be reached over 100 mg/L in contaminated water. The oxidation of nitrogen comprises around 78% of the atmosphere, produces nitrate and nitrite (NO2‾).

It is carried out by micro-organisms in plants, soil or water and, to a lower degree, by electrical discharges such as lightning. Nitrite does not typically exist in remarkable concentrations except for in a reducing environment, due to the fact that nitrate is found in a steadier oxidation state (World Health Organization, 2004). Nitrate can reach both surface water and groundwater as a result of different procedures which is initially, agricultural activities such as excessive application of inorganic nitrogenous fertilizers and manures from wastewater disposal and then, from oxidation of nitrogenous waste products in human and animal excreta, such as septic tanks.