Ali Al-Turki - Academia.edu (original) (raw)

Papers by Ali Al-Turki

Sustainability, Nov 22, 2019

Efficient application of nanoscale zero-valent iron (nZVI) particles in remediation processes rel... more Efficient application of nanoscale zero-valent iron (nZVI) particles in remediation processes relies heavily on the ability to modify the surfaces of nZVI particles to enhance their stability and mobility in subsurface layers. We investigated the effect of sodium carboxy-methyl-cellulose (CMC) polymer stabilizer, pH, particle concentration, and flow rate on the transport of nZVI particles in sand columns. Breakthrough curves (BTCs) of nZVI particles indicated that the transport of nZVI particles was increased by the presence of CMC and by increasing the flow rate. The relative concentration (RC) of the eluted CMC-nZVI nanoparticles was larger at pH 9 as compared to RC at pH 7. This is mainly attributed to the increased nZVI particle stability at higher pH due to the increase in the electrostatic repulsion forces and the formation of larger energy barriers. nZVI particle deposition was larger at 0.1 cm min −1 flow due to the increased residence time, which increases the aggregation and settlement of particles. The amount of CMC-nZVI particles eluted from the sand columns was increased by 52% at the maximum flow rate of 1.0 cm min −1. Bare nZVI were mostly retained in the first millimeters of the soil column, and the amount eluted did not exceed 1.2% of the total amount added. Our results suggest that surface modification of nZVI particles was necessary to increase stability and enhance transport in sandy soil. Nevertheless, a proper flow rate, suitable for the intended remediation efforts, must be considered to minimize nZVI particle deposition and increase remediation efficiency.

Environmental Earth Sciences, 2017

The sources and the distributions of 23 polycyclic aromatic hydrocarbons (PAHs) in surface (0-5 c... more The sources and the distributions of 23 polycyclic aromatic hydrocarbons (PAHs) in surface (0-5 cm depth) and subsurface (5-10 cm depth) soil in Riyadh, Saudi Arabia, were studied. Isomeric diagnostic ratios of the PAHs (the (as (the (anthracene/(anthracene ? phenanthrene)), (benz(a)anthracene/(benz(a)anthracene ? chrysene)), (fluoranthene/(fluoranthene ? pyrene)), (indeno(1,2,3-cd)pyrene/(indeno(1,2,3-cd)pyrene ? benzo (g,h,i)perylene)), and (benzo(a)pyrene/benzo(g,h,i)perylene) concentration ratios) were used to determine which anthropogenic sources of PAHs were dominant in different areas. The study area included four areas characterized by different anthropogenic activities; an urban area, an area strongly affected by traffic, a bare area, and an industrial area. The PAHs in all four area types were mainly emitted from factories and other mixed sources. The PAHs concentrations and patterns in some areas reflected the roles of anthropogenic activities in causing environmental pollution, especially the role of infrastructure projects (through emissions during the building work itself and emissions from heavy machinery and transport to and from the site). In contrast, PAHs concentrations and patterns in southern Riyadh showed that the recent improvements in the road network, which has improved traffic flow, have led to decreases in PAHs contamination caused by fuel combustion.

Nanomaterials, 2020

Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium... more Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium carboxymethyl cellulose, CMC) is usually used to minimize aggregation, increase stability, and enhance transport of nZVI. We investigated the stability and dynamic aggregation of bare and CMC–nZVI as affected by variations in pH, ionic strength (IS), and nZVI particle concentration. CMC coating of nZVI resulted in smaller hydrodynamic size and larger zeta potential. The largest hydrodynamic size of nZVI was associated with bare nZVI at high IS (100 mM), pH close to the point of zero charge (PZC, 7.3–7.6), and larger particle concentration (1.0 g L−1). The increase in the zeta potential of CMC–nZVI reached one- to four-fold of that for bare nZVI, and was greater at pH values close to PZC, high IS, and larger particle concentration. The stability of CMC–nZVI was increased by 61.8, 93.1, and 57.5% as compared to that of bare nZVI at IS of 1, 50 and 100 mM, respectively. Calculations of Der...

Polycyclic Aromatic Compounds, 2016

The objective of this study was to assess the pollution levels, sources, and human health risk of... more The objective of this study was to assess the pollution levels, sources, and human health risk of polychlorinated biphenyls (PCBs) in soils of industrial areas of the central and eastern regions of Saudi Arabia. Therefore, the surface soil samples from industrial areas (cement kiln, oil refinery, electric power plant, steel industry, and desalination plant) were collected and analyzed by High-Resolution Gas Chromatography-Mass Spectrometry/Mass Spectrometry-Time of Flight (HRGC-MS/MS-TOF) to quantify the levels of 26 PCBs (including 12 dioxin-like PCBs and 14 indicator-PCBs). The investigated 26 PCBs were detected in all soil samples. The total PCBs concentration (from tri-CBs to hepta-CBs) ranged from 171 to 4892 pg g −1 with an average of 1369 pg g −1 in soils of the central region and of 142-1231 pg g −1 with an average of 302 in soils of the eastern region, showing higher values at cement factory and/or oil refinery sites. Overall, the indicator-PCBs were the main congeners and contributed dominantly to the total mass of PCBs in comparison with the dioxin-like PCB congeners, with the most abundant for PCB-180 in the soil samples of the central region. Among individual dioxin-like PCBs, PCB-126 had the highest average value of the toxicity equivalence (TEQ). The TEQ values of ࢣ12dioxin-like PCBs did not exceed the Canadian soil quality guidelines of dioxin (4 pg TEQ g −1). Based on human health risk assessment via ingestion, dermal contact, and inhalation, low adverse effects of PCBs could be expected as indicated by lower values of cancer risk (ࣘ10 −6). The principal component analysis indicated that there is a different source of PCBs with similar or different PCB profiles.

Bulletin of Environmental Contamination and Toxicology, 2016

This study was conducted to identify and quantify polychlorinated dibenzo-p-dioxins (PCDDs) and p... more This study was conducted to identify and quantify polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in soil samples collected from selected industrial areas in the central and eastern regions of Saudi Arabia. All the investigated compounds of PCDDs/PCDFs were identified in the studied locations. The average concentrations of PCDDs (sum of seven congeners measured) ranged from 11.5 to 59.6 pg g-1 , with a maximum concentration of 125.7 pg g-1 at an oil refinery station followed by 100.9 pg g-1 at a cement factory. The average concentrations of PCDFs (sum of 10 congeners measured) accounted for 11.68-19.35 pg g-1 , with a maximum concentration of 38.67 pg g-1 at the cement factory. It was generally observed that the soil samples collected from industrial areas have substantially high toxicity equivalence (TEQ) values of PCDDs/PCDFs compared to soils of remote areas. Principal component analysis revealed that the cement factories and oil refineries were the primary sources of PCDDs and PCDFs.

Soil temperature is a major factor controlling many physical, chemical, and biological processes ... more Soil temperature is a major factor controlling many physical, chemical, and biological processes in the soil. Therefore, soil temperature greatly influence plant growth and nutrient uptake. Meteorological data mostly focus on the effect of climatic change on the above ground air temperature, which cannot adequately describe actual changes occurring in soil temperature in the vadose zone. In this study, we measured the changes in soil temperature in 10 locations in southern Tohama region, and used the HYDRUS model to simulate the changes in average soil temperature and temporal variations under variable boundary conditions. Soil temperature was continuously monitored at 4 depths of 25, 50, 75, and 100 cm using the 5TE Decagon sensor that was connected to an EM50G micrologger. Soil hydraulic and thermal parameters were obtained by laboratory experiments and inverse modeling against collected data. Meteorological data were used as input data for the boundary conditions. The model was c...

Arabian Journal of Geosciences, 2014

In the absence of permanent rivers, groundwater is one of the major water resources in Southern T... more In the absence of permanent rivers, groundwater is one of the major water resources in Southern Tihama plain, in the Southwestern Saudi Arabia. Hydrogeological investigation, as well as hydrogeochemical analyses, of 272 groundwater samples was performed to evaluate groundwater resources of shallow alluvial aquifer and their quality for different purposes in the Southern Tihama plain. Hydrogeological investigation revealed that groundwater occurs mainly in alluvium deposits under free water table conditions that range between 9 and 33 m. The calculated hydraulic gradient is inclined towards the west and southwest direction, ranging from 0.001 to 0.005, and soil infiltration rate of coastal plain soils is higher than other soil types. Hydrochemical analysis results indicate that groundwater type is mainly sodium chloride reflecting high amount of minerals. Groundwater in Tihama plain is not suitable for direct drinking and domestic purposes; therefore, it needs a proper treatment to remove high salinity and chloride concentrations. Result also shows that most of the groundwater has high salinity and low sodium hazard, suggesting little danger of exchangeable sodium. Other quality indices such as salinity, chloride, sulfate, and alkalinity range from suitable to high restricting water suitability for some industrial purposes without special treatment or mixing with low saline water.

Environmental Science and Pollution Research, 2015

Polycyclic aromatic hydrocarbons (PAHs) are potent environmental pollutants, and some of them hav... more Polycyclic aromatic hydrocarbons (PAHs) are potent environmental pollutants, and some of them have been identified as carcinogenic and mutagenic. To advance the knowledge of the environmental fate of PAHs, we systematically investigated the influence of different UV wavelengths irradiation on photolysis of PAHs on sandy soil under tow wavelengths (254 and 306 nm) UV irradiation for six PAHs. In addition, kinetic model and influence of several parameters on PAHs photolysis have been studied. The results obtained indicated that UV radiation with a wavelength of 306 nm was more efficient in the photolysis of the polycyclic aromatic hydrocarbons. Our results showed that fluoranthene (Flt) was the fastest in decomposition, has the greatest value for the coefficient of photolysis (7.4×10 −3 h −1), and has less half-life, reaching 94 h when using a wavelength of 254 nm. The results indicated that the pyrene (Pyr) was more resistant to photolysis in comparison with indeno(1,2,3-cd) pyrene (IP) and fluoranthene (Flt). The results indicate that photolysis is a successful way to remediate the six studied PAHs compounds.

Journal of Applied Sciences, 2010