Coastal areas are known to be sequestration points for various pollutants generated from industrial and urban activities. Diverse anthropogenic pollutants are typically delivered to coastal sediments via atmospheric or fluvial processes. Heavy metals, such as chromium, copper, manganese, zinc, and lead, are some of the toxic contaminants of greatest concernbecause of their well-established detrimental effects on the marine environment. In recent years, Saudi Arabia has encouraged activities to bring about economic development, particularly along the Red Sea. Jeddah is located on the Red Sea and is the second largest city in Saudi Arabia, famous for its beautiful coral reef.
In this dissertation, a variety of studies were applied not only to in situ sediment samples but also to aerosol particulate matter. The primary goal of the work is to determine the degree of heavy metal pollution in the region and, for key contaminants, identify their sources. The research plan in the dissertation included three phases that are discussed in the first chapter. The first phase included review of the literature, a field survey to design a sampling plan and identify thecollection sample points, and meetings with officials, including a Coast Guard representative to obtain the necessary permissions. The second phase involved collecting sediments and air filter samples and preparing the samples for laboratory analysis. The third phase comprised interpreting the results to obtain valuable relations between measured indices, and to determine the principal sources of pollution.
Chapter 2 of this dissertation investigated the state of pollution in eighty sediments focusing on six heavy metals: chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), and lead (Pb). The study also quantified the degree of pollution in sediments using various risk indices, including Geo-accumulation Indices (Igeo), Enrichment factors (Ef), Contamination factors (Cf), Pollution Load Indices (PLI), Potential Ecological Risk Indices (PERI) and Potential Toxicity Response Indices (RI). Results showed that the majority of the polluted sediments were recorded in the Middle and Southlocations, and Pb showed the highest concentration of the metals in the study area (77.34 mg/kg). The Igeo values for Pb in the Middle stations showed that 10% of the stations were categorized as moderately polluted, whereas 20% of the South location was classified as moderately polluted. The RI values in the South stations, especially the northern stations within the South location, indicate high Pb pollution in the area. This study recommended that appropriate management strategies should be applied for the Jeddah Coast to control potential pollution sources and prevent permanent hazards to marine ecology currently documented elsewhere. Additionally, the study implicated that the area needs more tracer studies such as isotopic and speciation studies that could be used to investigate the sources of the Pb in sediments, water, and even in airborne aerosols near the shoreline.
The findings of chapter 2 led us to study Pb isotopes in the sediment samples and the results are described in chapter 3. For the first time in the Red Sea area, the Pb isotopic ratios of 206Pb, 207Pb, and 208Pb were examined to evaluate the sources of Pb. A two end-member model and a three component fractional contribution model were both used to identify possible Pb sources and their percentage contributions in the study area. The isotopic data and modeling show that natural and anthropogenic sources such as gasoline and an identified unknown source contribute to the Pb load of Jeddah's sediments. The most obvious finding to emerge from this study is that different activities were controlling the Pb isotopes for each location. The study concluded that the Middle location was the most effected location by the Pb from different sources, and the Ef outcomes revealed that 80% of the sediment samples were considered extremely severely enriched with Pb. This study has raised many topics of concern in need of further investigation, including the ratio of Pb isotopes in air samples to Pb isotopes in the soil and isotopic variance with time, presumably recorded in sediment cores.
Finally, in chapter 4, the concentration of the heavy metals of particulate matter (PM) with a size less than 2.5micrometers is determined. The results of this study indicate that the PM2.5 concentration was higher in the North location,and the Pb concentration was higher in the Middle location. The results of the backward trajectory analysis help us understand the sudden concentration increase of PM on August 2 and September 13, 2017. On those dates, Jeddah'satmosphere was affected by a massive dust storms originating in the Tokar Desert in northeastern Sudan. According to Principle Component Analysis (PCA) results, the four principal sources of the heavy metals in the Jeddah ambient air were particles originating from the marine aerosol and re-suspension of soil-derived particles, particles originating from the land in addition to the anthropogenic contribution of Fe, particles originating from oil combustion, and particles originating from incineration and fossil fuel combustion.
The outcomes of the dissertation provide the spatial mapping of the distribution of heavy metals as well as their possible sources. This will help develop pollution control measures and serve as a resource for choosing optimum remediationmethods for water and sediments on the Saudi Arabian coast of the Red Sea. Taken together, the findings of each chapterare impactful and have many important implications for future practice.
Civil and Environmental Engineering
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Halawani, Riyadh, "Spatial Distribution, Sources, and Associated Risks of Toxic Metals In Red Sea Sediments Near Jeddah, Saudi Arabia" (2020). Civil and Environmental Engineering Theses and Dissertations. 8.