Explain Why Heavy Metals Are Not Removed From The Environment

     Heavy metals, such as copper, lead, mercury, and selenium are another group of toxins that pollute the water as well as the rest of the environment. The source of many of these pollutants are industries, automobile exhaust, mines, and even natural soil.

Researches involving the use of association between legumes and PGPBs (Plant Growth Promoting Bacteria) in heavy metals phytoremediation process were mainly performed for soils highly contaminated. However, even in agriculture soils, with moderate or low contamination levels, plants can accumulate high rates of heavy metals. So, food chain contamination by these metals presents a real thread to animal and human health.

Most people are surprised to learn that their bodies are contaminated with heavy metals. This is a little-known problem that has grown into a widespread issue. There are many different ways your body becomes contaminated with heavy metals, such as through the type of cookware you use, the tap water you drink and the fillings you have in your teeth. Fortunately, there are natural ways to cleanse your body of these harmful toxins, such as with chlorella. This is an algae found in nature and is oftentimes used in integrative medicine by naturopathic doctors in Arizona.

Unfortunately, these pollutants can be carried in the atmosphere by weather systems. Thus, they can travel for hundreds of miles causing damage as they go. Acid deposits in the soil can have devastating affects in the forest. It gradually causes the loss of plant nutrients, calcium and magnesium. This leads to dying off of trees in the forest. Also, acid deposits in lakes and streams have led to a drop in fish production. Mercury is another source of pollution which can be harmful to humans and wildlife. It comes from the emissions of coal-burning power plants and is deposited into the air and water. This chemical damages the nervous system, and has a detrimental affect on reproduction and prenatal development.

Tap water contains a wide variety of organic and inorganic materials, most of which are innocuous. However, some trace constituents in water, including heavy metals such as copper, zinc, cadmium and lead, are more problematic. Water leaving a drinking water purification plant will ordinarily contain negligible levels of lead and other harmful metals. These metals enter the water during distribution, through the corrosion of service pipes and plumbing in a process called leaching. Metals such as lead can leach from pipes, old solder or fixtures. Although some corrosion of plumbing is inevitable, the severity of leaching depends on the material of the pipes, the corrosivity and temperature of water and the amount of time water is stagnant

Physico-chemical methods such as chemical precipitation, chemical oxidation or reduction, filtration, ion exchange, electrochemical treatment, reverse osmosis, membrane technology and evaporation recovery have been widely used to remove heavy metal ions. These technologies usually produce wastes with high concentrations of metals which are a significant source of environmental pollution. Furthermore, the above methods may be ineffective or expensive, especially when the heavy metal concentrations

However, when Pb and As were added to Cd-spiked soil one after another, intestinal bioaccessibility of Cd in KBA and TAA soils increased relative to soils spiked with single Cd at the early stage of aging (data in Table 4.5 marked with *). In contrast, bioaccessibility of As and Pb were not influenced by the presence of Cd. Compared to binary mixtures of As, Cd and Pb, the co-existence of As, Cd and Pb in the same soil sample may lead to competitive sorption on soils due to the increased loading of metals/metalloid. Prior studies have noted that Pb was absorbed in preference to Cd thus increasing the observed solubility of Cd (Serrano et al., 2005; Appel et al., 2008). In this study, this preference was reflected on the observation that bioaccessibility of Pb in four types of soils was stable after 7 days aging, which indicates fast reaction between Pb and soil components. Besides, strong affinity of As to organic carbon, Fe oxide and Al oxide has been extensively reported (Solaiman et al., 2009; Komarek et al., 2013). Therefore, there was a high

The metals/ elements include cadmium, lead, copper, zinc and chromium which have been found at much higher quotas than they should be at (Kihampa). As humans grow and expand and industrialization increases so does the amount of chemicals in our water supply. As industrialization creates more compounds and chemicals that can be spilled or used in construction, these same chemicals are being increased in our water supplies such as magnesium and calcium (Kaur). Most of these chemicals come from construction waste or from power plants that use bodies of water to dump their waste; the reason industrial waste causes such disastrous problems is because the power plants and other companies don’t take the time to treat the waste and get rid of the harmful pollutants within the waste before dumping it into our water systems (Skariyachan, et al).

The contaminated sites are directly treated using the microorganisms. Underground petroleum pipes sometimes have leakages. Such sites of contamination are directly treated with microorganisms that can degrade petroleum hydrocarbons. The same is applicable in case of oil spills and heavy metal contamination. Phytoremediation is brought about by certain special plants which can take up the pollutants and make them less available in the soil. Some examples of such plants are mustard, alpine pennycress, hemp and pigweed. When the soil which is to be treated with the microorganisms is stimulated by providing it with oxygen, it is known as bioventing. Bioleaching is a process where living organisms or microorganisms are used to extract metals from their respective ores. This process ensures that there is not much expenditure of both chemicals and energy to bring about the extraction. Land farming refers to amending the soil with organic amendments like vermicompost, bulking agents etc which are tilled into

Heavy metals are elements that exhibit metallic properties. It mainly includes the transition metals, basic metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight, and some on chemical properties or toxicity (Duffus, 2002). Example for some heavy metal are iron (Fe), zinc (Zn), copper (Cu), lead (Pb), mercury (Hg), cadmium (Cd) etc.

Heavy metal contamination is one of the most serious and widespread forms of soil pollution [1, 2]. Many industrial and urban areas are polluted with

elements are not necessarily harmful to a person’s health. However, when they are combined in

It is recognized that accumulation of any metal into any lived organism depends more strongly on the fraction of metal that is available for uptake rather than the total metal concentration (Spurgeon and Hopkin, 1996). By their unique mechanism to feed mixed soil with organic matter by passing it through worms gut, where enzyme and surfactant are secreted into the content (Ma et al., 2017), particles are ground and mucus stimulate microbial activities by providing sugar (Martinkosky et al., 2017), earthworm species are widely recognized as suitable organisms for biomonitoring the effects of heavy metals in contaminated soils (Lemtiri et al., 2016; Maboeta et al., 2004).

The inorganic metals that often plague brownfields include arsenic, cadmium, zinc, nickel and copper. However, the bioavailability of other problematic metals such as lead and chromium are very low and require more advanced resources and strategies in order to be extracted. In addition to these toxic metals, it has been suggested that phytoextraction techniques can be used to remove radionuclides that exist in sites with mixed wastes. Radionuclide refers to any element that emits radiation and that can cause cancer through drinking water that it contaminates. In addition to the environmental and health concerns that brownfields pose, there are also many sociological impacts associated with them.

It is always difficult to remove contaminations from soils because it contains many toxic chemicals such as (Pb, As, Cu, Cd, Cr, Ni, Hg and Zn). This chemicals mixed with the soil after burning of industrial waste, electronics waste or uses of agricultural technology. Then rain water makes it seep deep into the soil and cause soil pollution. This makes it so difficult and time consuming to remove, particularly when the affected area is on a large scale. Soil is made of by two components which are organic and inorganic solid constituent, water and mixture of different gasses present in various proportions. The mineral component in the soil varies, according to the parent material which the soils had been developed due to the issue of different type of climate conditions. Also, soil can also be classified into three different properties, physical, chemical and biological properties. Physical properties of soil are being controlled by soil water movement, such as texture and soil structures. The soil moisture have high tendency in controlling solute movement, salt solubility, chemical reaction and microbiological activities and most importantly the bioavailability of metal ions. In this situation, a successful phytoremediation program must be considered as an alternative in the specific site. In the past lots of researchers have tried different method in order to mitigate or reclaim the heavy metals polluted soils, but so far phytoremediation is the best of all because it is