Abstract
Cadmium (Cd) is known to be toxic to plants and animals and can be transported to both ground and surface water through specific physical mechanisms. The chemical dynamics of Cd and other similar (heavy) metals in the soil environment is controlled by its interactions with both solid and aqueous phases of soil. The concentration of Cd and other metals in soil solution is highly influenced and regulated by processes such as adsorption-desorption, ion exchange, precipitation-dissolution, and soil and solution phase composition. Such processes, in turn, are function of soil properties such as pH, charge density and distribution, thickness of diffuse double layer and the activity of Cd present in solution. This report intends to provide a comprehensive and critical review to the effect of such properties on Cd transport.
1. Introduction
Historically, the discover of Cadmium (Cd) goes back to the eighteenth century (1817) by the German scantiest Friedrich Stromeyer who found it as an impurity in zinc carbonate. In the modern world, Cd is used in many industrial, urban, and agricultural applications ([1], [2]) and is often found together at sites contaminated with heavy metals. As Cd is a toxic metal to humans [3] and animals alike, the environmental and soil contamination with Cd is becoming of great concern in the last few decades. Therefore, it is important for chemists, environmental scientists and engineers to understand the chemistry of Cd interactions in soils to understand its bioavailability.
Millions of tonnes of hazardous waste containing CD are generated in the world on yearly basis. Because of the inefficient waste handling techniques and hazardous waste leakage in the past, thousands of sites, es...
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...in terms of two basic mechanisms: specific adsorption, which is characterized by more selective and less reversible reactions including chemisorbed inner-sphere complexes, and nonspecific adsorption (or ion exchange), which involves rather weak and less selective outer-sphere complexes [14]. It is established that specific adsorption brings about strong and irreversible binding of heavy metal ions with organic matter and variable charge minerals while nonspecific adsorption is an electrostatic phenomenon in which cations from the pore water are exchanged for cations near the surface. Cation exchange is a type of outer-sphere complexation with only weak covalent bonding between metals and charged soil surfaces. The process is naturally reversible and occurs rather quickly as it is typical for reactions which are diffusion-controlled and of electrostatic nature [14].
Soil pollution due to Arsenic (As) has been grabbed much attention in recent years due to its intimidation to human health and unfavorable effects on the growth of animals and plants (Duker et al , 2005; Williams et al., 2005). Volcanisms released Arsenic in the air which is brought to the earth surface by the rain water and contaminate the soil. Arsenic is also produced by the weathering of arsenic-containing minerals and ores, and by Sources commercial or industrial processes.
Human activities releasing the most EDC’s into water, soil and air include metal and crude oil processing, plastic, pharmaceuticals and food manufacturing, and use of pesticides and fertilizers to increase agricultural productivity (Rhind 2009). A rapid increase in human population, expansion of human settlement and technological advances lead to a surge in environmental pollution and bioaccumulation of the pollutants in terrestrial and aquatic environments. Many EDC’s ...
“Waste Management Overview.” World Nuclear Association. World Nuclear Association. Nov. 2013. Web. 22 Apr. 2014. >.
Dispersion of fine soil particles is controlled by a similar mechanism, dispersion is directly influenced by ions adsorbed on particle surfaces, particularly clay minerals. The presence of high sodium, especially at the low salt concentration in the soil water, causes dispersion and movement of fine particles within the pores. The particles may then become lodged in smaller pores, blocking water or air.
Lead (Pb), a heavy metal element is found in the Earth, in small amounts in ore along with other metals. Lead due to its high abundance is also an environmental pollutant found in lead-based paints, soil, fuel, some toys and jewelry, and metal pipes and toxic if ingested [1]. Another environmental pollutant is 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), also known as dioxin. TCDD is the most toxic organic pollutant in the polychlorinated dibenzo-p-dioxins(PCDD) family. TCDD is produced from the unwanted byproduct of industrial processes and combustions emissions and has no known function for industrial or commercial use. TCDD is found throughout the environment in low levels but main exposure is caused by consuming dairy, meat and fish products,
This essay concentrates on the heavy metal cadmium, and its occurrence in the environment, its pathways into and out of the human body and its movement into and out of Sewage sludge. Firstly, I will provide a clear definition of the Heavy Metal Cadmium.
Phytoremediation is characterized by the use of vegetative species for in situ treatment of land areas polluted by a variety of hazardous substances. (Sykes et al., 1999) Plants are especially useful in the process of bioremediation because they prevent erosion and leaching which can spread the toxic substances to surrounding areas. (United States Environmental Protection Agency, 2001) There are several types of phytoremediation being used today. These include phytoextraction, which relies upon a plant’s natural ability to take up certain substances (such as heavy metals) from the environment and sequester them in their c...
Soil and rock are the main composition of the planet’s crust. Rock is often considered a consolidated material but soil is described as an unconsolidated remains and deposits of solid particle that have been formed by the breakdown of rocks. Soils can be grouped into two categories depending on the method of deposition. Residual soils have formed from the weathering of rocks and remain at the location of their origin. Residual soils can include particles having a wide range of sizes, shapes and compositions depending on amount and type of weathering and the minerals of parent rock. Transported soils are soils that have been relocated from their original place. Transportation may have resulted from the outcome of gravity, wind, water glaciers or human activities. Transported soil particles are often segregated according to size during the transportation process. The method of transportation and deposition has significant effect on the
On the ground crust estimated concentration 16 parts per million (ppm) was found in zinc and aluminum ores as well as Germinate (sulfide copper ores))
Soil is composed of minerals, soil organic material (SOM), water, and air, according to the Montana State University’s soil scientists, Ann McCauley. The actual composition of these various components within soil has a big influence on the porosity; i.e., the composition affects the movement of water into and through the soil (McCauley, 2005), and the movement of water into and through soil is absolutely necessary for productive crops, and healthy ecosystems. The binding together of soil particles is called “aggregation” and when water passed into the soil aggregation, if it is healthy, will keep the porosity and water movement slow and productive, which “improves fertility and carbon sequestration in the soil” (avoiding erosion at the same time) (McCauley).
When the water comes into contact with the pyrite, the chemical reactions that take place causes the water to increase in pH which will dissolve heavy metals which stay in solution. However, when the pH levels reach a certain stage, the iron can then precipitate out, coating sediments with the characteristic yellow, red or orange colourings (D.E.P. 2, 2002; U.S.G.S.; U.S.E.P.A., 2002). The rate that A.M.D. advances is also influenced by the presence of certain bacteria (Doyle; U.S.G.S). A.M.D that has dissolved heavy metals such as copper, lead and mercury can contaminate ground and surface water. Especially at risk are mines that are located above the water table (Keller, 2000; D.E.P. 2, 2002). The sources of water that get polluted can be surface water that permeates into the mine, shallow ground water flowing through the mine or any water that comes into contact with the waste tailings produced by mines.
- Oades, J. Malcolm, Gavin P. Gillman, and Goro Uehara with Nguyen V. Hue, Meine van Noordwijk, G. Philip Robertson and Koji Wada. " Interactions of Soil Organic Matter and Variable-Charge Clays" IN: " In: David C. Coleman, J. Malcolm Oades and Goro Uehara (eds.), Dynamics of Soil Organic Matter in Tropical Ecosystems: Hawaii, NifTAL Project University of Hwawii Press, 1989. p. 69 - 95.
In the chart above, you can clearly see a plot was misplaced. It’s because the initial mass of the zinc was so high, and then the final mass was so low. Maybe to improve to increase the accuracy of this experiment, we could leave the metal in the acid in a longer period of time or we could use different types of metal with the same mass or the same metal, same mass, but different “forms” (Crushed up zinc, block of zinc…). Maybe we also could’ve changed the type of liquid we put the zinc in (such as soda or tomato juice) instead of half being water and acid. This experiment showed me that chemical weathering does have an impact on nature. I read in an article about how the ocean is becoming more acidic because of chemical weathering. Since the ocean is becoming more acidic, it’s destroying aquatic life. For example, it’s destroying shells since the ocean is becoming more acidic. So, when we put the metal in the acid, the acid broke the metal
Phytoremediation is a novel, efficient, environmentally friendly, low-cost technology, which uses plants and trees to clean up soil and water contaminated with heavy metals and/or organic contaminants such as solvents, crude oil, polyaromatic hydrocarbons and other toxic compounds from contaminated environments. This technology is useful for soil and water remediation.
As a result of this process, the mine sites "do not develop normal soil structure or support the establishment of a plant cover". Many mine sites have...