Lead Pollution in Soils

The long distance transportation of lead is a significant source of Pb in terrestrial systems. This is because lead from mining can be attached to dust and transported by winds over long distances. Upon precipitation, lead in dust is deposited on soils and can be adsorped by soil colloids or transported by flows to water bodies.

Serious health problems such as nerve damage and vision impairment occurs from Pb poisoning as shown in the figure below. 

Figure showing the possible effects of lead poisoning. Available at: http://brickleyenv.com/what-is-lead-poisoning/

One important source of Pb poisoning is from the consumption of food which is contaminated with pb from soils. This has been postulated in China as high levels of pb were found in children’s blood and agriculture soils (Bale 2014) 

However, researchers have been in dispute over the source of anthropogenic Pb contamination in soils, as a 'generally accepted tool that would unmistakably prove the importance of air pollution relative to local geogenic sources has not been available' (Steinnes, E. et al. 2005:1399).  Reimann et al. (2001) explained the increase in Pb in the O horizons as the result of “plant pumping and organic binding” and not related to atmospheric deposition. 

Steinnes, E. et al. (2005) thus quantified pollution lead in forest soils (sodic) of Norway. This study focuses on the atmospheric deposition of pb on soils, which is determined by using the stable pb isotope. They concluded that in Norway, overwhelming part of Pb in the humus layer of natural soils is derived from air pollution, as strongly suspected from previous studies. This result directs the need to curb anthrogpogenic Pb production sources in order to reduce the Pb contamination in soils. 

However, there is also the need to include the factor of acidity when using data from Steinnes, E. et al. (2005) for studies in acidic soils, such as in China. The leaching of Pb into deeper soil horizons makes it difficult to gauge degree of Pb contamination and its potential consequences to water sources and food security issues, and that Pb found in these areas of soil depth should include anthropogenic activities as a source of pollution. 

References

Bale, R. (2014) China’s other pollution problem – its soil. Available at: http://www.revealnews.org/article-legacy/chinas-other-pollution-problem-its-soil/

Brickley Environmental (2014) What is lead poisoning? Available at: http://brickleyenv.com/what-is-lead-poisoning/

Reimann, C., G. Kashulina, P. de Caritat, and H. Niskavaara. 2001. Multi-element, multi-medium regional geochemistry in the European Arctic: Element concentration, variation and correlation. Appl. Geochem. 16:759–780.

Steinnes, E. et al, (2005) Quantification of Pollutant Lead in Forest Soils. Soil Sci. Soc. Am. J. 69:1399–1404 (2005).