Ashraf Z. Al-Hamdan

Sequestration of heavy metals in soils from two polluted industrial sites: implications for remediation

This study was conducted to determine the distribution of heavy metals in two different contaminated field soils, and to assess its influence on remedial performance. The two field soils were obtained from two different polluted industrial sites in the Metropolitan Chicago area and were characterized for physical and chemical properties. The soils were referred to as silty sand and silty clay, based on their particle-size distribution. A five-step sequential liquid–solid extraction procedure was used to speciate the heavy metals into: (1) easily exchangeable; (2) carbonate bound; (3) Fe/Mn oxide bound; (4) organic bound; and (5) residual fractions. These results showed that all the metals except mercury were predominantly distributed as the Fe/Mn-bound form in silty sand. In contrast, they were distributed as the residual form in silty clay. Results indicated that the metals in both soils were in the forms that are not easily amenable to soil washing using water. Therefore, batch extraction tests with varying concentrations of ethylenediaminetetraacetic acid (EDTA) (0.05, 0.1 and 0.2 M) and acetic acid (0.5, 0.1 and 2 M) were conducted to identify an optimum soil-washing-based remediation system for both silty sand and silty clay. Ethylenediaminetetraacetic acid was found to be effective for the remediation of silty sand, while acetic acid was found to be suitable for the removal of metals that existed in residual form in silty clay. Based on these results, total removal efficiency was found to follow the order: sand + EDTA > clay + acetic acid > sand + acetic acid > clay + EDTA. This study showed that the speciation and remediation of heavy metals in soils depend on the sitespecific soil composition, and this should be carefully considered in the selection of an efficient remedial method.

Enhanced Soil Flushing for Simultaneous Removal of PAHs and Heavy Metals from Industrial Contaminated Soil

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are environmental concerns and must be removed to acceptable levels. This paper evaluates different flushing agents to enhance the remediation of soil contaminated with PAHs and heavy metals at a former manufactured gas plant site. Four flushing column tests at a constant hydraulic gradient of 1.2 were conducted using four different flushing agents, which included deionized water, chelant (0.2 M EDTA), surfactant (5% Igepal CA-720), and cyclodextrin (10% hydroxypropyl-β-cyclodextrin or HPCD). Additional column tests using Igepal and HPCD at a lower hydraulic gradient of 0.2 were con- ducted to investigate the effects of rate-limited desorption or solubilization of PAHs. The results showed that the EDTA produced the maxi- mum metal removal from the soil compared with deionized water, Igepal, and HPCD under different hydraulic gradient conditions. The 0.2 M EDTA flushing solution removed approximately 25-75% of the toxic heavy metals found in the soil. None of the PAHs were removed from the soil when deionized water and EDTA were the flushing solutions. The PAHs removal efficiencies in the Igepal and HPCD systems decreased as the hydraulic gradient decreased. However, the surfactant-enhanced systems were more efficient in removing PAHs from the soil than the HPCD systems under high- and low-hydraulic gradients. The results also demonstrated that the removal of PAHs in surfactant-enhanced systems depended upon the micelles formation, whereas in the HPCD-enhanced systems, it depended upon the ster- ioselective diffusion of the PAHs to the nonpolar cavity of the HPCD. Overall, this study showed that the contaminant removal in soil flushing systems depends on the flushing solution affinity and selectivity toward the target contaminant and the existing hydraulic gradient condition. DOI: 10.1061/(ASCE)HZ.1944-8376.0000076.

Particle morphology and mineral structure of heavy metal-contaminated kaolin soil before and after electrokinetic remediation.

This study aims to characterize the physical distribution of heavy metals in kaolin soil and the chemical and structural changes in kaolinite minerals that result from electrokinetic remediation. Three bench-scale electrokinetic experiments were conducted on kaolin that was spiked with Cr(VI) alone, Ni (II) alone, and a combination of Cr(VI), Ni(II) and Cd(II) under a constant electric potential of 1VDC/cm for a total duration of 4 days. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses were performed on the soil samples before and after electrokinetic remediation. Results showed that the heavy metal contaminant distribution in the soil samples was not observable using TEM and EDX. EDX detected nickel and chromium on some kaolinite particles and titanium-rich, high-contrast particles, but no separate phases containing the metal contaminants were detected. Small amounts of heavy metal contaminants that were detected by EDX in the absence of a visible phase suggest that ions are adsorbed to kaolinite particle surfaces as a thin coating. There was also no clear correlation between semiquantitative analysis of EDX spectra and measured total metal concentrations, which may be attributed to low heavy metal concentrations and small size of samples used. X-ray diffraction analyses were aimed to detect any structural changes in kaolinite minerals resulting from EK. The diffraction patterns showed a decrease in peak height with decreasing soil pH value, which indicates possible dissolution of kaolinite minerals during electrokinetic remediation. Overall this study showed that the changes in particle morphology were found to be insignificant, but a relationship was found between the crystallinity of kaolin and the pH changes induced by the applied electric potential.

Experimental Study on Chromium Containment by Admixed Soil Liner

This is a copy of an article published in the Journal of Environmental Engineering

Performance reconnaissance of stormwater proprietary best management practices

This paper presents a study to investigate the relative pollutant removal effectiveness of three proprietary end-of-pipe Best Management Practices (BMPs), namely, Baysaver, CDS, and Stormceptor. In this study, controlled conditions were used in order to provide documentation for the performance of the BMPs. For that purpose, a prototype facility was constructed at the University of Central Florida. For each BMP, five tests were conducted with five different flow rates: 1.6, 1.28, 0.96, 0.64, and 0.32 cfs. The monitored pollutants were sediments, nutrients, metals, and litters such as organic leaves, soda cans, plastic bottles, and cigarette butts and boxes. The results showed that some of the pollutants decreased in concentration while others increased between the influent and the effluent of the units. TSS load reductions for Baysaver, CDS and Stormceptor were 62.2%, 71.2%, and 83%, respectively. The performances of the studied BMPs for the pollutants were different. All the studied BMPs had good performance in removing the large sediment particles and litter. However, CDS had lower average inflow velocities in all tests than Baysaver and Stormceptor, causing sediment accumulation in the CDS inlet pipe. This study also showed that there was an increase in the total nitrogen concentration in Stormceptor while the nitrate/nitrite concentration increased in Baysaver and CDS. Other factors that should be considered in BMP evaluation are also presented in this paper.

Geochemical Reconnaissance of Heavy Metals in Kaolin after Electrokinetic Remediation

The development or implementation of electrokinetic soil remediation technique requires a good knowledge of how the contaminants are retained within the soil-water system. This paper investigates the speciation and extent of migration of the heavy metals, Cr(VI), Cr(III), Ni(II), and Cd(II), during electrokinetic soil remediation. A geochemical assessment of how the contaminants are held within the kaolin soil under induced electric potential is made by using the equilibrium model MINEQL+. The study is performed for three different contaminant cases: the Cr(VI) existing alone in the soil, the Cr(VI) combined with Ni(II) and Cd(II) in the soil, and the Cr(VI) combined with Ni(II) and Cd(II) in the soil in the presence of a reducing agent (sulfide). The adsorption of the studied metals by kaolin was implemented as an electrostatic behavior. FITEQL 4.0 model was used to determine the equilibrium constants of the electrostatic adsorption model of kaolin for the studied metals by optimizing the experimental titration and adsorption data of kaolin. This study showed that the initial speciation of the contaminants in the soil prior to the electrokinetic treatment depends on the type and amounts of contaminants present as well as on the presence of the co-contaminants or any reducing agent. Moreover, the extent of migration of the contaminants is strongly dependent on their initial speciation prior electrokinetic treatment. This study also showed that adsorption and precipitation are the significant hindering mechanisms for the removal of heavy metals from kaolin soil during electrokinetic treatment. The adsorption and precipitation forms of Cr(III), Ni(II), and Cd(II) increased near the cathode and decreased near the anode, whereas the adsorption form of Cr(VI) increased near the anode as well as in the middle region. However, the precipitation form of Cr(III), Ni(II), and Cd(II) as Cr2O3 or Cr(OH)3, Ni(OH)2, and Cd(OH)2, respectively, dominates over their adsorption form as they get closer to the cathode. Overall this study demonstrates that the electrolysis reactions control contaminant speciation and distribution in the soil during electrokinetic remediation because of the generated variations in pH and redox potential in the soil as a result of these reactions.

Side-by-Side Evaluation of Stormwater Proprietary BMPs

This paper presents a side-by-side study to determine the relative pollutant removal effectiveness of three proprietary end-of-pipe BMPs, namely, Baysaver, CDS, and Stormceptor. In this study, a controlled laboratory conditions were used in order to provide documentation of the performance of the BMPs. For that purpose, a lab facility was constructed at the University of Central Florida (UCF). The setup of the facility has the ability to pump flows required to replicate runoff events. Using this type of setup enables the relatively rapid testing of BMPs to evaluate their performance, under repeatable and consistent conditions for multiple flow rates, different constituents, particle sizes, and sediment concentrations. In this study, five tests were conducted with five different flow rates: 1.6, 1.28, 0.96, 0.64, and 0.32 cfs. The studied pollutants were sediments (TSS, TDS, and Bed load), nutrients (nitrogen and phosphorous), Metals (Fe, Cu, Zn, Cr, Ni, Cd), and litters such as organic leaves, soda cans, plastic bottles, and cigarette butts and boxes. The results showed that some of the pollutants decreased in concentration while others increased between the influent and the effluent of the units. The results also showed that the performances of the studied BMPs for the pollutants varied. Baysaver had the lowest TSS removal efficiency. Even though TSS removal efficiencies of CDS and Stomceptor were higher than Baysaver, they were still relatively low. All the units had good performance in removing the large sediment particles and litter. The results also suggested that nitrogen was produced in the Stormceptor unit during the testing program. Other than removal efficiencies, the paper also presents some factors that should be considered in BMP evaluation. The review engineer will need to decide which factors to include in an evaluation and their respective importance to the user.

The association of remotely sensed outdoor fine particulate matter with cancer incidence of respiratory system in the USA

ABSTRACT This study aimed to assess the association between exposure to fine particulate matter (PM2.5) and respiratory system cancer incidence in the US population (n = 295,404,580) using a satellite-derived estimate of PM2.5 concentrations. Linear and logistic regression analyses were performed to determine whether PM2.5 was related to the odds of respiratory system cancer (RSC) incidence based on gender and race. Positive linear regressions were found between PM2.5 concentrations and the age-adjusted RSC incidence rates for all groups (Males, Females, Whites, and Blacks) except for Asians and American Indians. The linear relationships between PM2.5 and RSC incidence rate per 1 μg/m3 PM2.5 increase for Males, Females, Whites, Blacks, and all categories combined had slopes of, respectively, 7.02 (R2 = 0.36), 2.14 (R2 = 0.14), 3.92 (R2 = 0.23), 5.02 (R2 = 0.21), and 4.15 (R2 = 0.28). Similarly, the logistic regression odds ratios per 10 μg/m3 increase of PM2.5 were greater than one for all categories except for Asians and American Indians, indicating that PM2.5 is related to the odds of RSC incidence. The age-adjusted odds ratio for males (OR = 2.16, 95% CI = 1.56–3.01) was higher than that for females (OR = 1.50, 95% CI = 1.09–2.06), and it was higher for Blacks (OR = 2.12, 95% CI = 1.43–3.14) than for Whites (OR = 1.72, 95% CI = 1.23–2.42). The odds ratios for all categories were attenuated with the inclusion of the smoking covariate, reflecting the effect of smoking on RSC incidence besides PM2.5.

Reconnoitering the linkage between cardiovascular disease mortality and long-term exposures to outdoor environmental factors in the USA using remotely-sensed data

ABSTRACT This ecological study aimed to assess the association between long-term exposures to outdoor environmental factors and mortality rate from cardiovascular disease (CVD) in a diverse and spatially distributed population from 3,094 counties within the U.S. (n > 3,780,000 CVD deaths) using satellite-derived data of PM2.5 concentrations, sunlight, and maximum heat index. Multivariable logistic regression analyses were conducted to determine whether PM2.5, sunlight and maximum heat index were related to the odds of the total CVD death rate based on gender, race, and age taking into consideration the confounding risk factors of diabetes, obesity, leisure- time physical inactivity, smoking and socioeconomic status. The study has shown that elevated levels of PM2.5, sunlight and heat long-term exposures are significantly associated with an increase in the odds ratio of the total CVD mortality. The results suggest a 9.8% (95% CI = 6.3% – 13.4%), 0.9% (95% CI = 0.5% – 1.2%), and 0.7% (95% CI = 0.5% – 11.2%) increase in total CVD mortality associated with 10 μg/m3 increase in PM2.5 concentrations, 1,000 kJ/m2 increases in sunlight, and 1 oF increase in heat index, respectively. The odds ratios for the CVD death rate due to long-term exposures of PM2.5, sunlight, and heat index were significantly greater than 1.0 for all categories except for Asians, Hispanics, and American Indians, indicating that the effect of long-term exposures to particulate matter, sunlight radiation, and maximum heat on CVD mortality is trivial for Asians, Hispanics, and American Indians. Among the categories of age, the group of 65 years and older had the highest odds ratios, suggesting that the age group of 65 years and older are the most vulnerable group to the environmental exposures of PM2.5 (OR = 1.179, 95% CI = 1.124 – 1.237), sunlight (OR = 1.047, 95% CI = 1.041 – 1.053), and maximum heat (OR = 1.014, 95% CI = 1.011 – 1.016). The odds ratios of CVD mortality due to the environmental exposures were higher for Blacks than those for Whites. The odds ratios for all categories were attenuated with the inclusion of diabetes, obesity, leisure-time physical inactivity, smoking, and income covariates, reflecting the effect of other medical conditions, lifestyle, behavioral and socioeconomic factors on the CVD death rate besides the environmental factors.

Transport and Speciation of Heavy Metals in Soils during Electrokinetic Remediation: Influence of Soil Type and Electric Potential

This paper presents transport and speciation of heavy metals in soils during electrokinetic remediation. A series of laboratory electrokinetic experiments was conducted using two different clayey soils, kaolin and glacial till, to investigate the migration and removal of heavy metals Cr(VI), Ni(II), and Cd(II). In kaolin, the acid front advances towards the cathode faster than the base front towards the anode, leading to a development of an acidic condition in most of the soil. In glacial till, however, because of its high buffering capacity, the development of the acid front is hindered, which results in alkaline conditions throughout the soil during electrokinetic remediation. In both kaolin and glacial till, Cr(VI) migration towards the anode increases as the applied voltage gradient increases. However, Cr(VI) migration was higher in glacial till as compared to kaolin because of the high pH conditions that exist in glacial till. As the voltage gradient increases, greater migration of Cr(VI) was observed in glacial till as compared in kaolin. Some Cr(VI) was reduced to Cr(III) in both soils. The Cr(VI) reduction rate to Cr(III) as well as the Cr(III) migration are significantly affected by the applied voltage gradient, leading to different chromium distributions throughout the soil. In kaolin, the applied voltage gradient has a pronounced effect on the migration of nickel and cadmium. The Ni(II) and Cd(II) migration towards the cathode increases in kaolin as the applied voltage gradient increases. Unlike kaolin, in glacial till the applied voltage gradient has no effect on nickel and cadmium migration because of its high acid buffering capacity.