Date of Award
Multidisciplinary Studies - Individualized Option, M.A.
Geography and Planning Department
Thomas Murphy, Ph.D., Sc.D.
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Thomas Murphy, Ph.D., Sc.D.
Kimberley N. Irvine, Ph.D.
Elisa Bergslien, Ph.D.
Laboratory facilities in developed countries provide a variety of options for analysis of environmental samples and commercial commodities that could impact human health. The same is not true in developing countries and there is a great need to identify technologies that could be used to provide robust, accurate, cost-effective analysis that minimizes the need for extensive technical training. An X-ray Fluorescence (XRF) analyzer seems to be an analytical technique that could be such a tool for developing countries. Therefore, the objective of this thesis was to assess the performance and utility of a handheld, portable XRF unit in analyzing different types of environmental and commercial commodity samples in Cambodia. Because a number of different materials were analyzed, this thesis has a slightly different format than typical. Each of the following three chapters has its own methodology, results and discussion sections. This approach was taken because the materials analyzed and methods for sampling the materials were so different, it was clearer to separate the analyses into separate, individual chapters. This abstract provides a brief overview of each chapter.
1. Chapter One
The need to have a more robust, cost effective and less time-consuming form for environmental samples in the field where samples could not be brought in for the laboratory analysis led to the manufacture of a first X-ray fluorescence (XRF) analyzer. This first chapter outlines the theory of the XRF, its advantages and limitations, and provides some QA/QC of a handheld XRF (XL3t 900, Billerica, MA) on skin whiteners, which were purchased and donated by university students for mercury levels.
The results showed that up to 98 samples (16%) of creams analyzed contained mercury higher than 20 ppm, and 64 concoctions out of 192 samples were contaminated with more than 20 ppm mercury. Although there were suppressions (20%) of mercury at concentrations near 15,000 ppm (i.e. an under-estimation), the XRF proved to be an excellent tool capable of detecting metals; particularly mercury in semi-solid solutions.
2. Chapter Two
Phnom Penh, the capital city of Cambodia, is home to some 1.4 million people and undergoing urbanization. In spite of its urbanization, Phnom Penh has yet to have a primary wastewater treatment plant and adequate sewage drainage system in place. There are two main interceptor sewer channels that drain wastewater and storm water from the southern part of the city into a natural wetland, Boeung Cheung Ek. These two sewer channels are the Tum Pun Sewer System and the Meanchey Sewer System. These are open sewer systems which collect all types of industrial, hospital, institutional and household wastes, and in turn discharge into the wetland. In Cambodia data related to metals contamination in sediment and street dust are very limited. So, this chapter of the thesis seeks to determine metal concentrations, spatial patterns and sources in sewer, wetland and street dust samples. Metals levels also are compared with United States Environmental Protection Agency (USEPA), New York State Department of Environmental Conservation (NYSDEC), and Provincial Sediment Quality (PSQ), Ontario, Canada guidelines.
The results showed that although there are elevated metal concentrations in the sewer and wetland sediments and street dust samples, they are still lower than those reported elsewhere such as in Hong Kong, Greece, China, Korea, the US, and Malaysia. One sewer site (M1) had significantly higher metals levels than any other site of the two sewer systems, because it is geographically surrounded by industries and factories. The metal concentrations, especially Pb, Zn, and Cu, decreased with distance from this site. The levels of Pb in street dust appeared higher in high-density traffic areas and decreased with distance from the busy traffic streets. Although leaded gasoline can be a source of lead in street dust and sediments, Cambodia apparently complies with the EU guideline on the level of lead use in gasoline. In addition to leaded gasoline, diesel fuel can also contain metals but the levels are subject to further analysis. Other sources of metals in street dust include tire abrasion, brake lining and transmission oil. To reduce the levels of metals, the two sewer systems should be dredged periodically. The dredging also would increase channel flow capacity during storm events. Source tracking of metals should be conducted in more detail to inform management strategies. For the management of street dust, street sweeping and washing may be effective means to allay the metal toxicity levels.
3. Chapter Three
Lead (Pb), which is a potentially hazardous toxicant, can be an additive agent of jewelry items and children’s toys. It is added to polyvinylchloride (PVC) pipes, so that it would provide rigidity, lower manufacturing costs and resistance to sunlight. Lead also has been a paint additive and this is of great concern in North America. Cambodia imports most of its consumer goods from other countries, but the regulatory inspection on imported products is not strictly enforced due to the lack of customs inspection tools, facilities and trained professionals. The purpose of this chapter is to assess jewelry items, children’s toys and paints for potential metal contamination from various markets in Phnom Penh, Cambodia and Bangkok, Thailand by means of the handheld X-ray fluorescence (XRF) analyzer.
The results indicated that significant levels of Pb were used in the products (up to 43% in jewelry items and 4.3% in paints). These findings suggested that more restrictive regulations on the sales and use of toxic products should be imposed, so that health risks can be minimized.
The XRF was manufactured, and over the years, has been re-engineered to provide the features necessary to operate in the field where laboratory-based assays not are suited. The XRF has some limitations for some elements like Cr and Hg in soils, the analyses of which necessitate laboratory-based verification such as an AAS or ICP. It also does not have the capacity to assess the degree of dermal and oral absorption of metals, although these aspects are still evolving. Nonetheless, the XRF would be an ideal tool for on-site and in situ investigation in Cambodia; particularly for customs officers, environmental researchers and engineers.
Lim, Sereyrath, "X-Ray Fluorescence (XRF) Analyzer - Theory, Utility, and QA/QC for Environmental and Commercial Product Samples in Cambodia" (2013). Multidisciplinary Studies Theses. 8.