**2.1 Natural sources**

Trace metals are found in excess levels in the environment, they are formed by geographical processes such as volcanic eruptions, weathering of rocks, and leaching into rivers, lakes, and oceans due to the action of water [25]. The presence of heavy metals in water depends on the local geology, hydrogeology, and geochemical characteristics of the aquifer [26]. One of the main sources of pollution is weathering. The weathering of the sedimentary rocks such as limestone or dolomite or shale makes the water contaminated or polluted. When there is an interaction of water with rock element, it also leads addition of these elements into the water; thus, contamination occurs. Examples of such elements are granite, syenite, basalt, gabbro, nepheline, and andesite. Due to the particular ore or the minerals, the element level increases. Elements examples are magnetite, hematite, goethite, siderite, calcite, cuprite, malachite, azurite, chromite, kaolinite, montmorillonite, arsenic trioxide, orpiment, arsenopyrite, calamine, smithsonite, pyrolusite, and rhodochrosite [27–30]. The sulfide deposition also increases as it is associated with the mineralization of the gold and hydrous iron oxide ores [31].


#### **Table 2.**

*Major sources of some heavy metal ions in water [24].*

#### **Figure 1.**

*Contamination of water through different sources.*

### **2.2 Anthropogenic sources**

Anthropogenic events, in which human settlement replaced the natural forest and agricultural activities have increased the environmental impacts. Such activities have contaminated the aquatic ecosystems, which include spring waters from the river like the Amala and Nyangores, tributaries of Mara River, Indonesia in Mau Complex. The maximum of forest land is converted into human settlement and agriculture. People

### *Heavy Metal Contamination of Water and Their Toxic Effect on Living Organisms DOI: http://dx.doi.org/10.5772/intechopen.105075*

who live near the Mara River Basin use that spring water for the purpose of animal and agricultural purposes [21]. The water carrying capacity has decreased with the rapid increase in industrialization and urbanization. Hg concentration in water has increased with agriculture activities and human activities. Activities like domestic sewage into the water, solid waste burning, coal and oil combustions, and pyrometallurgical processes and mining are the main reason for this. Water, by either snow or rain, brings the contaminated soil with Hg into the adjacent water areas [32, 33]. The source of Ni is the corroded metal pipes and containers [34]. The major source of lead in water majorly comes from additives of paints and petrol and aerosol precipitation, which is formed due to the high temperature used in industrial processes for the purpose of coal combustion, smelting, and cement production [35], and chloralkali, batteries, fluorescent lamps, thermometers, and electronic switches production. Chemical industries are some industrial activities through which Hg pollutes the water system and these activities are the largest contributor to Hg contamination in the environment [36].

### **2.3 Domestic sewage**

Huge amount of untreated sewage from domestic is thrown into the river. This untreated waste from domestic has the presence of toxins. These toxins are due to the presence of solid waste or from the litter of plastic, or the contamination of bacteria due to the presence of these the water can get polluted. Domestic untreated water is thrown directly into the water resource and this majorly causes pollution inside the water and harms the ecosystem [37]. These pollutants majorly depend upon what kind of industry has thrown those pollutants. When these toxic metals get inside the water, they decrease the quality of the water [38]. Around 25% of pollution inside the water is caused only by these industries [39]. When the water gets contaminated, the water gets enriched by the nitrogen and phosphorous elements. With the presence of these nutrients, the growth rate of algae gets multiplied, and then it competed with the surrounding aquatic biota for the dissolved oxygen in water [40]. The presence of nitrite and nitrate anions leads to a major threat to the exposed organisms; examples of such threats are methemoglobinemia. It is more common in small children, and the symptoms caused by this are cyanotic color in the skin due to blood alterations [41]. Water sources that get deposited by this sewage also become anions rich, due to the presence of chlorine in urine, and NaCl is used in the human diet. On the side of the sea, there is the presence of chloride in high concentrations due to the leakage of salt into the sewerage system. It also may be increased by industrial processes [42].

### **2.4 Industrial source**

Contamination of heavy metals in the aquatic environment is very harmful since these elements cannot be degraded and they get accumulated inside the living organisms [43]. Residue from the industry is the major source through which these heavy metals get into the aquatic ecosystems, and their accumulation in water varies with the type of wastewater treatment used [44]. Effects known as deleterious can be observed when the metal particles are introduced into the water system [45, 46]. Different metals from the Amazon River (Brazil) and the Yukon River (Alaska) were analyzed in the solid-state only. Plants have the presence of these metals in water. In tissue, the concentration of several metals is slow, and their concentration should be kept in less range only as more concentration can be harmful to the biological

development of the pant [47]. Through the food chain, fish contaminants can reach man [48]. Effluent from industries, water tank leakages, dumping beside marines, and due to radioactive waste and atmospheric deposition, are some sources of water contamination. Disposed of heavy metals and waste from industries they get accumulated in rivers and lakes thus causing harmful impacts on animals and humans. For suppression of the immune, reproductive failure and acute poisoning toxins are responsible [49]. Then there is direct damage to plant or animal nutrition at that time human health is affected. The pollutants that are polluting the water are killing marine organisms such as mollusks, marine birds, fishes, and other organisms that live in the sea [50].
