Atmospheric lead sources

The work of the Harrison group on alkylleads in air is perhaps the most persuasive of the reports as to the advocation of an environmental methylating process. Some of the sites whose atmospheric lead was sampled were very remote, such as Harris Island, Outer Hebrides, UK. Air reaching this site should not have any anthropogenic content but concentrations of alkylleads were found to be in the 3-7 ngm-3 range61. There was a higher than normal ratio of alkyl to total lead present here also (from 10-30%). A maritime source of volatile alkyllead was proposed61,62. 

Correlation of Atmospheric Soil and Atmospheric Lead in Three North American Cities Can Re-suspension of Urban Lead Contaminated Soil be a Major Source of Urban Atmospheric Lead and Cause Seasonal Variations in Children s Blood Lead Levels ... 

Correlation of atmospheric soil and atmospheric lead in three North American cities can re-suspension of urban lead contaminated soil be a major source of urban atmospheric lead and cause seasonal variations... 

A significant amount of lead emitted in a country is transported beyond the national borders contributing to the trans-boundary transport. In 2002 as much as 4.8 kt (around 60% of total anthropogenic emission) of atmospheric lead, emitted in Europe were involved in transport across state borders. Absolute magnitudes of lead transported outside countries vary substantially from country to country. It was calculated as difference between national emission and deposition to the country. This magnitude depends on national emission, size of the territory, climatic conditions and spatial distribution of emission sources within the country. 

The wide range of potential sources and their environmental persistence may well explain why PCDDs and PCDFs are ubiquitous. It is believed that there are two main routes by which PCDDs and PCDFs are released into the environment via the atmosphere leading to deposition on soil, water and plants and via solid or liquid waste with subsequent contamination of land (e.g. sewage sludge). These findings should help to reduce the already extensive effort needed to trace back the contamination to its sources, although the persistence of PCDDs and PCDFs in the environment for many years means that historical as well as current sources need to be taken into account. 

Bollhofer, A., and Rosman, K. J. R. (2000). Isotopic source signatures for atmospheric lead The Southern Hemisphere. Geochim. Cosmochim. Acta 64, 3251-3262. 

The APPI source is one of the last arrivals of atmospheric pressure sources [80,81]. The principle is to use photons to ionize gas-phase molecules. The scheme of an APPI source is shown in Figure 1.34. The sample in solution is vaporized by a heated nebulizer similar to the one used in APCI. After vaporization, the analyte interacts with photons emitted by a discharge lamp. These photons induce a series of gas-phase reactions that lead to the ionization of the sample molecules. The APPI source is thus a modified APCI source. The main difference is the use of a discharge lamp emitting photons rather than the corona discharge needle emitting electrons. Several APPI sources have been developed since 2005 and are commercially available. The interest in the photoionization is that it has the potential to ionize compounds that are not ionizable by APCI and ESI, and in particular, compounds that are non-polar. 

The relative contribution of mobile source emissions to atmospheric lead levels over the next decade is expected to decrease slightly for two reasons (1) the Federal government s imposition of a phasedown of lead content in gasoline, as called for in regulations promulgated in September 1976 (43) and (2) the incompatibility of leaded gasoline and the catalytic converter introduced in late 1974 for control of regulated (HC, CO, NO,) pollutants (44,45). 

Boutron et al. (1991) studied the change in atmospheric emissions of Cd, Pb, and Zn before and after 1971 by analyzing Greenland ice cores. They found that Pb values were 200 times higher in 1971 than before the industrial revolution, with 99% of the lead from anthropogenic sources. Since 197 and the introduction of unleaded gasoline, atmospheric lead values have declined by 7.5 times in the United States. The same authors also reported that Cd and Zn concentrations in the ice have... 

By far the greatest contribution to the atmospheric lead level comes from automotive lead emissions. In most countries strong efforts have been made to reduce or replace the amuont of lead in the gasoline, where it is added as tetraethyl lead. Another important source of atmospheric lead emission, estimated to be about 10 % [74], is contributed from industry by smelters and recovery operations. Significant values have been found in the proximity of primary and secondary smelters, e g. peak levels in excess of 200 pg/m are reported in the former Yugoslavia [75], whereas the standards are in the range of 1.5 - 0.5 pg/m3 (EPA). 

The level of lead in the earth s crust is about 20 mg/kg. Lead in the environment may drive from either natural or anthropogenic sources. Natural sources of atmospheric lead include geological weathering and volcanic emissions and have been estimated at 19 000 tons/year, compared to an estimate of 126 000 tons/year emitted to the air from mining, smelting and consumption of over three million tons of lead per year (WHO, 1989). 

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