Scientific Research

Dominic Joel Ombati

My PhD research is on Fate and Transport of Anthropogenic and Geogenic Lead (Pb) in the Arid Climate, San Bernardino County, California.

Fate and transport research project can be defined as the study of how chemicals degrade and where they travel in the environment when they are released intentionally or unintentionally. Transport is how chemicals move through the air, water and soil and fate is how the chemicals change in the environment  https://energyenvironment.pnnl.gov/projects/project_description.asp?id=177.

It has been established by the US department of energy that Fate and Transport analysis is the holistic way of studying chemicals in the environment. It has also been established by the United States Environmental Protection Agency (EPA) that successful studies of any ecosystem function require a detailed knowledge of fate and transport processes  https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.highlight/abstract/6005.

According to the United Nations environmental program, lead (Pb) is a heavy metal that is toxic even at very low exposure levels and has acute and chronic effects on human health. In the environment, lead is also toxic to plants, animals and micro-organisms. Lead (Pb) can originate from human activities (anthropogenic) or from natural sources (geogenic).

Lead (Pb) poisoning occurs when humans especially children are exposed even to low levels of lead (Pb). Lead (Pb) poisoning is a serious health problem globally and almost every county in United States has a childhood lead (Pb) poisoning prevention program.

In my study area, anthropogenic lead (Pb) along highways is mainly from leaded gasoline and it was deposited during the leaded gasoline era. Geogenic lead (Pb) is from the Lead Mountain mine. My PhD research focuses on the following projects:

  1. Transport mechanism of anthropogenic lead (Pb) along highways in Barstow, California. https://gsa.confex.com/gsa/2017AM/meetingapp.cgi/Paper/307634
  2. Fate of anthropogenic lead (Pb) along  highways in Barstow, California.
  3. Transport mechanism of geogenic lead (Pb) in the Lead Mountain area in Barstow, California.
  4. Fate of the transported geogenic lead (Pb) from Lead Mountain in Barstow, California.
  5. Lead isotopic signature of anthropogenic and geogenic lead from highways and Lead Mountain in Barstow, California.

I received partial funding for this research from the Geological Society of America Graduate Student Research Grant Program in 2017. Grant Number: 11828-17.

In most cases dust from disturbed or deteriorating lead-based paint on the walls, doors and windows of a home is the main cause of child lead (Pb) poisoning https://www.atsdr.cdc.gov/csem/csem.asp?csem=34&po=5. Studies carried out in Benin, Cameroon, Côte d’Ivoire, Egypt, Ethiopia, Guinea, Kenya, Morocco, Mozambique, Nigeria, Sudan, Tanzania, Togo, Uganda, and Zambia found some paints sold for home use containing extremely high lead levels of up to 100,000 parts per million (ppm) or more http://www.ipen.org/documents/africa-lead-paint. These concentrations are several times more than the 90 ppm United Nations recommended limit of lead (Pb) in paint.

Sustainable remediation of lead (Pb) contaminated environment requires a good understanding of lead (Pb) transport mechanism and its chemical behavior in various environmental media. It is generally recognized that lead (Pb)  mobility, toxicity, and bioavailability depend heavily on its chemical form (Davidson et al., 1998Gleyzes et al., 2002Kaasalainen and Yli-Halla, 2003Rauret et al., 1999Sutherland and Tack, 2003).  Understanding  lead (Pb) transport mechanism and chemical  behavior  of various chemical forms of lead (Pb) as related to mobility, toxicity and bioavailability is crucial for the sustainable management of  Lead (Pb) contaminated environment.

Sustainable lead (Pb) remediation of Lead requires solid scientific research on:

  1. Lead (Pb) transport mechanism- how it moves in the environmental (Transport)
  2. Lead (Pb) chemical fractionation – chemical change in the environment  (Fate)

References

Davidson, C. M., Duncan, A. L., Littlejohn, D., Ure, A. M., and Garden, L. M., 1998, A critical evaluation of the three-stage BCR sequential extraction procedure to assess the potential mobility and toxicity of heavy metals in industrially-contaminated land: Analytica Chimica Acta, v. 363, no. 1, p. 45-55.

Gleyzes, C., Tellier, S., and Astruc, M., 2002, Fractionation studies of trace elements in contaminated soils and sediments: a review of sequential extraction procedures: TrAC Trends in Analytical Chemistry, v. 21, no. 6, p. 451-467.

Kaasalainen, M., and Yli-Halla, M., 2003, Use of sequential extraction to assess metal partitioning in soils: Environmental Pollution, v. 126, no. 2, p. 225-233.

Rauret,G., López-Sánchez, J., Sahuquillo, A., Rubio, R., Davidson, C., Ure, A., and Quevauviller, P., 1999, Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials: Journal of Environmental Monitoring, v. 1, no. 1, p. 57-61.

Sutherland, R. A., and Tack, F. M., 2003, Fractionation of Cu, Pb and Zn in certified reference soils SRM 2710 and SRM 2711 using the optimized BCR sequential extraction procedure: Advances in Environmental Research, v. 8, no. 1, p. 37-50.

Regional report on  lead in solvent-based paints for home use in Africa, October 2017 http://www.ipen.org/documents/africa-lead-paint.

 

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