Metals and Metalloids in Water

Sulfide minerals are one of the most important natural sources of arsenic in groundwater. Oxidation of arsenopyrite (FeAsS), in analogous fashion to pyrite (FeS2), may release high coneentrations of arsenie into solution. 

Although trivalent inorganic arsenic, with its propensity for binding to the SH group of enzymes, is acknowledged to be more toxic to humans than pentavalent inorganic arsenic, it must be recognized that As can be converted to As in the human body as part of the reduction/biomethylation pathway of excretion 

2 Lead in Drinking Water. The naturally soft, slightly acidic, plumbosolvent water of the Loch Katrine water supply for the Glasgow area was recognized many years ago to release lead from the lead pipes and tanks in the domestic plumbing of the Victorian and subsequent (even post-World War II) eras.  

Essentially, elemental lead becomes soluble in acidic conditions due to its oxidation by dioxygen. Furthermore, compounds such as carbonate and hydroxycarbonate compounds of lead, i.e. PbC03 and Pb3 (C03)2(0H)2, that may coat the pipes, will dissolve under acid conditions. 

In view of the concern over detrimental effects of exposure to lead upon human health, in particular the possible impact upon intelligence 

---

Treatment of Heavy Metals and Metalloids in Water by Heterogeneous Photocatalysis... 

Behra, R., Genoni, G. P., and Sigg, L. (1994) Scientific Basis for Water Quality Criteria for Metals and Metalloids in Running Waters, Report No. 6 EAWAG. 

This chapter outlines current approaches for characterizing elements in settled dust and indoor air, factors influencing the geochemistry of household dust, potential indoor and outdoor sources, and the need for reliable bioavailability data to improve assessments of residential exposures to metals. The emphasis of this chapter is on studies that examine a variety of metals and metalloids in indoor environments. For information on individual elements, the reader is referred to the elemental chapters in Part III, and for information on other indoor sources and pathways (e.g., food and drinking water) and potential effects on human health, the appropriate chapters in Part I and II should be considered. 

Microbial leaching of metals from ores is a promising adjunct to more aggressive metal recovery technologies (77), but is generally achieved by oxidative processes that generate very acidic waters. It seems unlikely that similar approaches will be of much value in removing contaminant metals and metalloids from soils. 

Metals and metalloids that form alkyl compounds, eg, methylmercury and methylarsenic acid, tributjltin, deserve special concern because these compounds are volatile and accumulate in cells they are poisonous to the central nervous system of higher organisms. Because methylmercury or other metal alkyls may be produced at a rate faster than it is degraded by other organisms, it may accumulate in higher organisms such as fish. Hg species are also reduced to elementary Hg which is soluble in water but lost by volatilization to the atmosphere (40). 

Pollution of soils and waters by human activities is an important and widespread problem. This pollution by, organic and inorganic substances can affect individual organisms, human populations, and ecosystems, each in its own unique way. In particular former military installations, often used for weapons production and nuclear power plants represent a ongoing and substantial threat to environment and human health because of the specific pollutants that can be released Solvents, explosives, fuels, radionuclides, heavy metals, and metalloids all have been identified in the environment around these installations. Remediation technologies for these contaminated sites have been developed based on conventional systems utilising physical and chemical treatments, such as excavation and incineration, pump-and-treat methods, ultraviolet oxidation, soil washing, etc. 

Figure 4 illustrates the effect of different binding mechanisms on the porewater concentrations of metals and metalloid species in relation to the solid-phase concentrations. First, if a certain component were very soluble and not bound to the solid in any way, the pore water concentration at equilibrium would equal the total concentration in the system. However,... 

---