Toxic Effect of Metal Ions in Water Resources
Water is the most important resource. Without water life is not possible. From a chemical point of view, water, H2O, is a pure compound, but in reality, you seldom drink, see, touch or use pure water. Water from various sources contains dissolved gases, minerals, organic and inorganic substances. This photograph of Guilin shows the beauty of natural water. The rain curved an interesting landscape out of the lime stones in the area. Natural waters are often important parts of wonders of the world. The total water system surrounding the planet Earth is called the hydrosphere. It includes freshwater systems, oceans, atmosphere vapors, and biological waters. The Arctic, Atlantic, Indian, and Pacific oceans cover 71% of the Earth surface, and contain 97% of all water. Less than 1% is fresh water, and 2-3 % is ice caps and glaciers. The Antarctic Ice Sheet is almost the size of North America continent. These waters dominate our weather and climate, directly and indirectly affecting our daily lives. They cover 3.35×108 km2. The four oceans have a total volume of 1.35×109 km3. Groundwater is an important part of the water system. When vapor is cooled, clouds and rain develop. Some of the rain percolates through the soil and into the underlying rocks. The water in the rocks is groundwater, which moves slowly. Dust particles and ions present in the air are nucleation center of water drops. Thus, waters from rain and snow also contain such ions: Ca2+, Mg2+, Na+, K+, NH4+. These cations are balanced by anions, HCO3-, SO4-, NO2-, Cl-, and NO3-. The pH of rain is between 5.5 and 5.6. Rain and snow waters eventually become river or lake waters. When the rain or snow waters fall, they interact with vegetation, top soil, bed rock, river bed and lake bed, dissolving whatever is soluble. Bacteria, algae, and water insects also thrive. Solubilities of inorganic salts are governed by the kinetics and equilibria of dissolution. The most common ions in lake and river waters are the same
