On the Speciation of Iodine in Marine Aerosol

We have compiled and analyzed a comprehensive data set of field observations of iodine speciation in marine aerosol. The soluble iodine content of fine aerosol (PM₁) is dominated by soluble organic iodine (SOI; ∼50%) and iodide (∼30%), while the coarse fraction is dominated by iodate (∼50%), with nonnegligible amounts of iodide (∼20%). The SOI fraction shows an equatorial maximum and minima coinciding with the ocean "deserts," which suggests a link between soluble iodine speciation in aerosol and ocean productivity. Among the major aerosol ions, organic anions and non-sea-salt sulfate show positive correlations with SOI in PM₁. Alkali cations are positively correlated to iodate and negatively correlated with SOI and iodide in coarse aerosol. These relationships suggest that under acidic conditions iodate is reduced to HOI, which reacts with organic matter to form SOI, a possible source of iodide. In less acidic sea-salt or dust-rich coarse aerosols, HOI oxidation to iodate and reaction with organic matter likely compete.

Comparative studies of atmospheric trace elements: improvements in air quality near a copper smelter

Measurements of trace element concentrations, including heavy metals in the atmosphere near a copper smelter in Port Kembla, New South Wales, have shown improvements in air quality, attributed mainly to modernisation of the plant, with more than 85% decrease (for each element) in airborne Cr, Zn, Se, Ag, Cd, Sb, Au and Pb, associated with 74% reduction in Cu concentration. This data was obtained by analysis of air particulate sampled in 2001-2002 for comparison with measurements at the same location in 1978. As expected, measurements of Na and Cl derived from the marine aerosol at this coastal location showed no corresponding change. The recent analysis of air particulate shows significant correlations between the monthly concentrations of Cu, Zn, Se, Ag and Pb, associated with industry, hence giving a high enrichment in airborne particulate by reference to the element/Sc ratios in 'average' soil. These enrichments, shown by heavy metals in particular, were two orders of magnitude greater than the values recorded in the atmosphere of rural areas; however, it is clear that air quality at Port Kembla is much improved and predominantly related to the modernisation of the smelter.

Sources of halogens in the environment, influences on human and animal health

Of the halogens, fluorine has the highest crustal abundance (544 mg/kg) while iodine has the lowest (0.25 mg/kg), however, chlorine is by far the most abundant halogen in the cosmos. The geochemistries of the four naturally occurring halogens have some similarities with fluorine, chlorine and bromine being classified as lithophile elements while iodine is more chalcophile in nature. Bromine and iodine behave in a similar fashion in the secondary environment and could be classified as biophile elements being concentrated in organic matter. Chlorine, bromine and iodine are strongly enriched in the sea while iodine and to a lesser extent bromine are further concentrated in the marine algae.Apart from the occurrence of fluorine in fluorite (CaF2) there are few commonly occurring minerals which contain the halogens as essential constituents. In the igneous environment fluorine and chlorine tend to occupy hydroxyl lattice sites in micas, amphiboles, apatites etc., while in sediments clays can contain appreciable quantities of these elements. Bromine and iodine, however, would be unlikely to fit into the lattice sites of common rock-forming minerals.Bromine, like iodine, is probably volatilised from the marine environment and is carried on to land surfaces. This behaviour of iodine and bromine is reflected in the increased I/CI and Br/CI ratios of surface run-off in continental compared with near coastal environments.Limited information on the soil geochemistry of the halogens suggests that the soil contents of chlorine, bromine and iodine are influenced by proximity to the sea. Soil fluorine, however, is generally dependent on its content in the parent material. In some areas pollutant sources of the halogens contribute appreciably to their concentration in the environment.Iodine and chlorine are essential elements for mammals and fluorine has been shown to have beneficial effects on bone and tooth formation. However, excess quantities of dietary fluorine can be harmful. It is possible, in view of its ubiquitous occurrence in the biosphere, that bromine has a hitherto unknown function in human and animal health.

The geochemistry of iodine - a review

Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect.Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks its concentration is fairly uniform and averages 0.24 mg/kg. Sedimentary rocks tend to have higher concentrations with average iodine contents of:-recent sediments 5-200 mg/kg, carbonates 2.7 mg/kg, shales 2.3 mg/kg and sandstones 0.8 mg/kg. Organic-rich sediments are particularly enriched in iodine.Soils, generally, are much richer in iodine than the parent rocks with the actual level being decided mainly by soil type and locality. Little soil iodine is water-soluble and much iodine is thought to be associated with organic matter, clays and aluminium and iron oxides. Most iodine in soils is derived from the atmosphere where, in turn, it has been derived from the oceans. Seawater has a mean iodine content of 58 μg/L, while non-saline surface waters have lower and very variable levels. Subsurface brines and mineral waters are generally strongly enriched in iodine.Marine plants are frequently enriched in iodine while terrestrial plants have generally low contents. Iodine is essential for all mammals.Consideration of the geochemical cycle of iodine reveals that its transfer from the oceans to the atmosphere is probably the most important process in its geochemistry.

Environmental metallic carcinogens: an overview of exposure levels

Exposure levels of the principal carcinogenic and potential carcinogenic metal and mettalloid pollutants in the environment (e.g., arsenic, beryllium, chromium, nickel, cadmium, and lead) are primarily reviewed with emphasis on their environmental sources both natural and manmade. There is a general paucity of definitive information concerning aspects of material balance and chemical transformations of these elements in various chemical forms in the environment, primarily the atmosphere. Estimates of both exposure levels and risk to populations other than industrial workers of the above metals have been in most instances quite difficult to obtain and generally speculative. The trend for the immediate future appears to be of greater exposure to these metals not only as a result of generally increased usage patterns, but also because of prospective enhanced use of fossil fuels for space heating and electricity generation.