Hydrogeochemistry Essay

CHAPTER SIX

6. HYDROGEOCHEMISTRY

6.1. General

Hydrogeochemistry is a sub discipline of hydrogeology, which referred to as Chemical hydrogeology in some references (Domenico and Schwartz, 1990), and Groundwater geochemistry in some others (Merkel and Planer-Friedrich, 2005). One may also points to "Contaminant hydrogeology" used by Fetter, (1998) as another term that carries the same syllabus as Hydrogeochemistry. In all fields of science and engineering, sub-disciplines are develop to accomplish some missions, fulfill some requirements, and supplement the base subject. The same is true with Hydrogeochemistry. This sub-discipline is developing to deal with quality, contamination, chemistry, chemical processes, and reactions that take place

For instance, Prasanna et al. (2011) clearly demonstrates that the study of quantity of water alone is not sufficient to solve the water management problems because its uses for various purposes depend on its quality. The atmosphere derives its water from evaporation of the ocean and to a lesser extent from water at the land surface of the continents (Stumm and Morgan, 1970).

Origin of solute in groundwater is derived from either input from precipitation, incorporation during weathering processes and water rock interaction with the aquifer matrix or mixing of water from different origin. Therefore, understanding the geochemistry of the groundwater is crucial to understand geochemical processes within the aquifer, to define the pathway of chemical evolution, to identify source and amount of recharge, differentiate mixing and interconnection of groundwater and surface water, etc.

Solute dissolved in rainwater progressively enriched towards inland derived from dissolution of dust particles (calcium), gaseous emissions from plants and soil (ammonium and sulfate), burning of fossil (sulfur and nitrogen oxide) which result in the formation of sulfuric acid and nitric acid in rain (Drever,

It’s also acts as water is a function of the types and quantities of dissolved substances in water, but there is no universal linear relation between total dissolved substances and conductivity.

Since the electrical conductivity is a measure to the capacity of water to conduct electrical current, it is directly related to the concentration of salts dissolved in water, and therefore to the Total Dissolved Solids (TDS). Salts dissolve into positively charged ions and negatively charged ions, which conduct electricity. Since it is difficult to measure TDS in the field, the electrical conductivity of the water is used as a measure. EC for drinking water must be changed and converted to TDS using the following calculation (http://www.lenntech.com/applications/ultrapure/conductivity/water-conductivity.htm#ixzz2E4EauDf, 2012):

TDS (mg/l) or (ppm) = 0.5 X EC (dS/m or mmho/cm) or = 0.5 * 1000 x EC (μS/cm)

The electrical conductivity (EC) for all water samples varied from 25 - 1,108 μs/cm reflecting the different amounts of the total dissolved ions in