**1. Introduction**

Heavy metals refer to a group of toxic elements that are very important both biologically and industrially. According to definition, heavy metals are naturally occurring metals having an atomic number greater than 20 and an elemental density greater than 5 g/cm [1]. The rapid developments of industrialization and unplanned urbanization have introduced heavy metals into the environment through improper dumping of industrial wastes directly on land and near water sources [2]. Pollution of soil and water sources with heavy metals is one of the most severe environmental problems that can seriously affect the quality of the environment and human health [3]. Today, the entry of heavy metals into water and soil sources from various natural and anthropogenic sources has been confirmed. Although the formation process of environmental pollution has a long history, the growth of this abnormality after the industrial revolution grew increasingly due to the very significant use of heavy metals in various industrial technologies [4]. Today, the amount of global production of heavy elements in various industries is very high. Heavy metals found in soils and water resources include nickel, chromium, lead, cadmium, arsenic, copper, cobalt, zinc, manganese, aluminum, mercury and antimony. Among the mentioned heavy

metals, arsenic, cadmium, lead, and mercury are among the 20 most dangerous substances that have been determined by the Agency for Toxic Substances and Disease Registration and the US Environmental Protection Agency (USEPA). Among the effects of environmental pollution with heavy metals is the occurrence of bio-toxicity and its effects on the biological degradation process [5]. One of the ways of entering heavy elements into the environment, especially agricultural soils, is the use of different fertilizers that contain heavy elements as impurities. Excessive accumulation of heavy metals in agricultural soils causes more uptake of these metals by food crops and vegetables, which in turn can cause serious risks to human health [6]. The entry of, including cardiovascular diseases, cancer, Alzheimer's, chronic anemia, cognitive impairment, kidney damage, skin problems, memory loss, Aplastic anemia, infertility and nervous system weakness [7]. With the continuous entry of heavy metals into water and soil sources, there has been a concern that the concentration of these metals will exceed the permissible limits and disrupt the majority of biological activities. In addition, with the growth of public awareness, people have become sensitive to the contamination of soil and water sources with toxic elements and have understood that these compounds can have very important effects on the quality and quantity of their lives [3]. As a result of growing public awareness and sensitizing societies to the threats ahead, innovations and technologies have been formed that can be effective in cleaning and reducing the risk of sites contaminated with heavy metals. The distinguishing feature of pollution related to heavy metals is that, unlike organic pollution, these pollutants are not degradable and are resistant to biological and chemical processes [8]. Therefore, due to the fact that these compounds are resistant to decomposition, the extent of contaminated areas increases every year. There are about 100,000 contaminated areas in the United States, while the extent of contaminated agricultural land in China reaches more than 3.5 million hectares [9]. Of course, it is estimated that there are 2.5 million other contaminated areas in this country. For the decontamination of these areas, more than 6 billion euros should be spent annually [10]. If proper information of contaminated sites in other countries of the world are prepared, the cost of their decontamination will probably exceed thousands of billions of euros. The purification of soils, sediments, and polluted water has been the subject of a lot of research, and scientists have suggested a variety of technologies. The effectiveness and efficiency of methods used to treatment the contaminant from different sources is a critical aspect. Here, we will review some of the various purification methods that have been suggested for soil and water pollution, as well as an emphasis on more modern methods.

The technologies used for the treatment of contaminated areas can be divided into two main category: In-situ technologies and ex-site technologies. In the in-situ technology, the process of remediation and treatment of pollution is carried out at the place of its origin. The purpose of this type of treatment is to remove pollutants from soil, water and sediments without moving the soil and sediment. In ex-site technologies, drilling, refining, and treatment of contaminated materials are done outside the contaminated sites [10]. In the in-situ remediation process, the costbenefit ratio is generally higher than the ex-situ remediation method. While removal or extraction the pollutant from soil and water is much better than immobilization or containment the pollutant. In addition to the above, in the in-situ remediation process, the contact of workers and people with the polluted environment is less and the possibility of contamination spreading to other areas is reduced [11]. To become more efficient and economical, these techniques can sometimes be used simultaneously [3].

*New Advancements in the Field of Pollution Treatment, Including Contamination of the Soil… DOI: http://dx.doi.org/10.5772/intechopen.109955*
