Oxidants/amendments

W. Hartley, R. Edwards, and N.W. Lepp, Arsenic and Heavy Metal Mobility in Iron Oxide-amended Contaminated Soils As Evaluated by Short- and Long-term Leaching Tests, Environ. Pollut. 131(3), 495-504, Oct. (2004). 

Within 6 months after enactment of the Qean Air Act Amendments of 1990, and at least every 3 years thereafter, the Administrator shall review and, if necessary, revise, the methods ( emission factors ) used for purposes of this Act to estimate the quantity of emissions of carbon monoxide, volatile organic compounds, and oxides of nitrogen from sources of such air pollutants (including area sources and mobile sources). In addition, the Administrator shall permit any person to demonstrate improved emissions estimating techniques, and following approval of such techniques, the Administrator shall authorise the use of such techniques. Any such technique may be approved only after appropriate public participation. Until the Administrator has completed the revision required by this section, nothing in this section shall be construed to affect the validity of emission factors established by the Administrator before the date of the enactment of the Clean Air Act Amendments of 1990. 

The reduction of atmospheric concentrations of the sulfur and nitrogen oxides blamed for acid rain was a major issue in the debate that led to the 1990 Clean Ail-Act Amendments (CAAA). The final legislative action is one of the most complex and comprehensive pieces of environmental legislation ever written. 

Public concerns about air quality led to the passage of the Clean Air Act in 1970 to amendments to that act in 1977 and 1990. The 1990 amendments contained seven separate titles covering different regula-toiy programs and include requirements to install more advanced pollution control equipment and make other changes in industrial operations to reduce emissions of air pollutants. The 1990 amendments address sulfur dioxide emissions and acid rain deposition, nitrous oxide emissions, ground-level ozone, carbon monoxide emissions, particulate emissions, tail pipe emissions, evaporative emissions, reformulated gasoline, clean-fueled vehicles and fleets, hazardous air pollutants, solid waste incineration, and accidental chemical releases. 

The regulation is still in use, with amendments covering the purity of mixed carotene from algae, Sunset Yellow FCF, and titanium oxide. ... 

During ISCO, oxidants and any necessary amendments are introduced to the treatment area with one or more of the available delivery approaches. Pilot-scale testing is often used to determine the type of amendment and delivery system used at a given site. Some of the key considerations for the common oxidants and delivery approaches are summarized below. 

Lance injection, jetting, and fracturing—Use of a high-pressure lance can create microfractures in soils that increase soil permeability and allow for direct injection of oxidants and amendments into a desired treatment area without the need for an existing or new groundwater well. 

Manganese in uncontaminated Israeli arid soils is predominantly in the easily reducible oxide fraction (35-40% of the total-HN03 Mn), followed by the carbonate fraction (18-25%), and the residual fraction (14-25%) (Han and Banin, 1996) (Table 5.4). Manganese in the organic fraction amounts to 9-12% and in the reducible oxide fraction to 5-11%. The exchangeable fraction of Mn in the soils is very low. In the sludge-amended calcareous soils of Southeast Spain, the residual and the carbonate bound Mn fractions are the major solid-phase (Moral et al., 2005). In comparison, the Mn in fine-textured soils from the southeastern United States is... 

Drying and remoistening air-dry soils greatly lowers their ability to oxidize Cr (Bartlett and James, 1980). Since Cr3+ has a similar ionic radius (0.64 x 10 10 m) to Mg (0.65 x 10 10 m) and trivalent Fe (0.65 x 10 ° m), it is possible that Cr3+ could readily substitute for Mg in silicates and for Fe3+ in iron oxides. This explains the high proportion of Cr found in the residual fraction in the native arid soil. On the other hand, humic acids have a high affinity for Cr (III) (Adriano, 1986). Thus, present results show that when soluble Cr was added to soils, Cr3+ was initially and immediately bound to the organic matter fraction. Due to its slow conversion into the reducible oxide and residual fractions, Cr in the amended soils departed and remained removed from the quasi-equilibrium. However, Cr approached the quasiequilibrium with time. 

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