The Problem with Arsenic

Certainly, the AUES has the requisite arsenic and reactive metals available. For example, zinc, a highly reactive metal, was widely used in smoke mixtures and has been found in substantial levels at numerous places throughout the AUES. Because it is not very toxic, it has largely been ignored. The District of Columbia does not know what pH is necessary to cause nascent hydrogen to be formed from a reaction with zinc but with the acid in the air at one property on Glenbrook Road, acid rain and other sources of acidic conditions such as buried bottles of acid, this problem must be investigated. 

The more troublesome problem is the biotransformation of arsenic into arsine gas. Four common soil fungi, two anaerobic bacteria and algae in surface water can generate a methylated version of arsine. Generally, see Arsenic Speciation in the Enviromnent by W. R. Cullen and K. J. Reimer, Chemistry Review (1989) Arsenic in the Soil Environment by E. Smith, R. Naidu, and A. M. Alston, Advances in Agronomy (1998) and Arsenic Chemistry in Soils An Overview of Thermodynamic Predictions and Field Observations by Muhammed Sadiq, Water Air and Soil Pollution (1997). 

Municipal landfills producing nominal amounts of methane soil gas in the summer months can cause serious illness and death in the winter because the frozen soil has a chimney effect on the soil gas, causing it to migrate laterally and collect in nearby buildings. Thus, there is no dilution 

In years past, several Spring Valley residents and pets have come down with rare blood diseases at the time, the cause was unknown. One of these illnesses is aplastic anemia. The Merck manual lists two causes of aplastic anemia benzene and arsenic. Another illness is pernicious anemia. Medical literature suggests that arsenic toxicity can masquerade as pernicious anemia. 

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One of the problems associated with coal gasification is that in coal, many of the elements of the periodic table can be found in minor concentrations. An element of emerging concern is arsenic, which may be present in concentrations on the order of 1-10 ppmw in coal. Toxic elements are of no concern when they end up bound in the slag or in stable chemical compounds. The problem with arsenic is that under reducing conditions it forms the volatile compound AsHs. It is a known poison for... 

Extensive work has been done over the last twenty years on the removal of arsenic from heavy metal effluent streams. The most recent paper by Donnelly and Anderson (2) summarizes these developments and references more than 25 papers on this subject. One of the problems with arsenic precipitation is that arsenic will occur in two valence states, arsenate and arsenite. Using ferric sulfate as a precipitant, the pH regime for optimum precipitation is different for the two species. Figure 3 presents a graph which outlines the best pH for a mixture of the species. 

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