Soil contaminants, chemistry

Remediation is a process of restoration. In order to conduct remedial activities, we must first understand both the process which generated the contaminants, the contaminant chemistry, the soil geology, the site hydrology, and the nature and kind of interactions between the soil, water, and the contaminants. In this brief exposition, weTl discuss a couple of different types of sites and see the limits of remediation technology. 

Barnhart J. 1997. Chromium chemistry and implications for environmental fate and toxicity. Journal of Soil Contamination 6(6) 561-568. 

The purpose of this chapter is to introduce the various technologies and mechanisms used to treat AD or heavy-metal-rich solutions and to demonstrate the use of soil-water chemistry principles for generating and/or improving contaminant treatment technologies. 

Jardine, P.M. and Taylor, D.L., Fate and Transport of Ethylenediaminetetraacetate Chelated Contaminants in Subsurface Environments, in Soil Environmental Chemistry, D.L. Sparks, Ed., Elsevier Science Publishers, Amsterdam (Geoderma, 67, 125), 1995b. 

In saline soils and soils contaminated with geothermal brines, the ionic strengths of the soil solution may exceed 0.5 M. This fact poses the necessity of using equations which have been developed to describe the activity coefficients of ions in concentrated, multicomponent electrolyte solutions. As part of a study on the chemistry of ore-forming fluids, Helgeson (50) has proposed that the true individual ion activity coefficients for ions present in small concentrations in multicomponent electrolyte solution having sodium chloride as the dominant component be approximated by a modified form of the Stokes-Robinson equation. The equation proposed is ... 

Zhu Y., Yu H., Wang J., Fang W., Yuan J., Yang Z. Heavy metal accumulations of 24 asparagus bean cultivars grown in soil contaminated with Cd alone and with multiple metals (Cd, Pb, and Zn). Journal of Agricultural and Food Chemistry 2007 55(3) 1045-1052. 

Mackay D. 1988. The chemistry and modeling of soil contamination with petroleum. In Calabrese E, Kostecki P, eds. Soils contaminated by petroleum. New York, NY John Wiley and Sons, 5-18. 

The substantial changes include more emphasis on organic chemistry, soils, contaminants in continental water and remediation of contaminated land. T> do this effectively, the terrestrial environments chapter from the first edition has been split into two chapters dealing broadly with solids and water. We have reorganized the box structure of the book and have placed some of the original box material, augmented by new sections, to form a new chapter outlining some of the basic chemical principles that underpin most sections of the book. 

The chemistry of soil contaminants is also an important factor determining the success of a barrier layer. Chemical attack on soil surface covers by low-pH soils, and the deflocculation of clays by oils and tars, may also cause failure of the integrity of the barrier, leading to upward migration of the contaminants (Muller-Kirchenbauer et al., 1988). To minimize the risk of exposure due to barrier failure. Tiller (1992) suggests that surface barriers can be used in conjunction with a less sensitive land use that poses the least risk to public health if the barrier fails. 

Soil contamination also can be very difficult to detect. New analytical methods have made it possible to detect and analyze dioxins, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Analytical techniques have made it possible to detect the presence of these substances, determine whether remediation is needed, and evaluate the extent to which it has been carried out. Chemistry has provided or contributed to the remediation technologies that have been developed,... 

The problem of soils contaminated with mixed heavy metals and organic compounds is even complex because of the different chemistry of heavy metals and organic compounds (Chapter 15). Some studies have shown that there may be some synergistic effects that retard the contaminant transport and removal, but few other studies show the behavior of heavy metals and organic compounds similar to that observed with either heavy metals or organic compounds. 

The extent of sorption to soils is governed by a variety of physico-chemical properties of both the soil and the contaminant. The soils heterogeneous chemistry and physics resulting from the varying proportions of the major... 

Furthermore, the restrictions on operating voltage that apply to titanium in a marine enviroment are not always relevant to titanium in soils free of chloride contamination. Coke breeze is, however, an integral part of the groundbed construction and ensures a lower platinum consumption rate. However, for some borehole groundbeds, platinised niobium is preferred, particularly in the absence of carbonaceous backfill or in situations where the water chemistry within a borehole can be complex and may, in certain circumstances, contain contaminants which favour breakdown of the anodic Ti02 film on titanium. In particular, the pH of a chloride solution in a confined space will tend to decrease owing to the formation of HOCl and HCl, and this will result in an increase in the corrosion rate of the platinum. 

Models of chemical reactions of trace pollutants in groundwater must be based on experimental analysis of the kinetics of possible pollutant interactions with earth materials, much the same as smog chamber studies considered atmospheric photochemistry. Fundamental research could determine the surface chemistry of soil components and processes such as adsorption and desorption, pore diffusion, and biodegradation of contaminants. Hydrodynamic pollutant transport models should be upgraded to take into account chemical reactions at surfaces. 

Several factors influence the efficiency of removing contaminants from soils by EO. The first factor is the chemistry generated at the electrodes. Low-pH conditions generated at the anode cause... 

In recent years the interest of environmental analytical chemistry was turned to the so-called emerging contaminants or new unregulated contaminants including pharmaceuticals, endocrine disruptors, detergents, personal care products, plasticizers, flame retardants, gasoline additives, etc. These compounds are released continuously to the environment and can be found in water, sediments, soils, etc. In most of the cases they are found at trace level concentration (ng/L) therefore, powerful analytical capabilities are required for their determination. 

The use of nanomaterials is important in environmental science and technology in terms of their applications in green chemistry, pollution prevention, remediation of contaminated soils and water, and sensing and detection of pollutants. These applications are directed towards environmental improvement and pollution control. 

The book focuses on the biogeochemistry of trace elements in arid and semiarid zone soils and includes an introductory chapter on the nature and properties of arid zone soils. It presents an updated overview and a comprehensive coverage of the major aspects of trace elements and heavy metals that are of most concern in the world s arid and semi-arid soils. These include the content and distribution of trace elements in arid soils, their solution chemistry, their solid-phase chemistry, selective sequential dissolution techniques for trace elements in arid soils, the bioavailability of trace elements, and the pollution and remediation of contaminated arid soils. A comprehensive and focused case study on transfer fluxes of trace elements in Israeli arid and semi-arid soils is presented. The book concludes with a discussion of a quantitative global perspective on anthropogenic interferences in the natural trace elements distributions. The elements discussed in this book include Cd, Cu, Cr, Ni, Pb, Zn, Hg, As, Se, Co, B, Mo and others. This book is an excellent reference for students and professionals in the environmental, ecological, agricultural and geological sciences. 

Bailey G.W., Akim L.G., Shevchenko S.M. Predicting chemical reactivity of humic substances for minerals and xenobiotics use of computational chemistry, scanning probe microscopy, and virtual reality. In Humic Substances and Chemical Contaminants, C.E. Clapp, M.H.B. Hayes, N. Senesi, P.R. Bloom, P.M. Jardine, eds. Madison, WI Soil Science Society of America, Inc., 2001. 

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