Optimal conditions of Al and Fe extraction from laterite soil using D-optimal design

This paper reports pioneering work in identifying an alternative coagulation agent of wastewater treatment, given the availability of commonly used agents are of a higher cost relative to more natural sources, such as soil. The alternative proposed is laterite soil from northern Malaysia because it contains high amounts of Al and Fe, which are well-known coagulants. The soil was grinded and sieved to obtain uniform particle sizes of <250???m. Al and Fe were extracted from the soil. Extraction agents: (1) HCl, (2) NaOH, and (3) HCl?+?NaCl were chosen. It was found that the most effective agent to extract Fe was 5?N HCl while to extract Al was HCl?+?NaCl, 2 and 4?N, respectively. D-optimal design observed that extraction time t, temperature T, and ratio of amount of laterite soil to amount of extractants r, showed a significant effect on Al extraction. In contrast, the combination of factors t and r exhibited insignificant effect on Fe extraction while other factors were significant. The optimum conditions for extraction of both Al and Fe were 90?°C, 40?min, for r?=?1:15, which gave [Fe]?=?1,870?mg/l and [Al]?=?0.17?mg/l and 90?°C, 90?min, for r?=?1:10, which gave [Fe]?=?2,900?mg/l and [Al]?=?0.130?mg/l. Since concentration of Fe extracted from laterite soil was high, it was concluded that laterite soil can be considered as an alternative and novel source of coagulant applicable in a wastewater treatment coagulation process.     

Influence of pedestrian age and gender on spatial and temporal distribution of pedestrian crashes

Objectives: Every year, about 1.24 million people are killed in traffic crashes worldwide and more than 22% of these deaths are pedestrians. Therefore, pedestrian safety has become a significant traffic safety issue worldwide. In order to develop effective and targeted safety programs, the location- and time-specific influences on vehicle–pedestrian crashes must be assessed. The main purpose of this research is to explore the influence of pedestrian age and gender on the temporal and spatial distribution of vehicle–pedestrian crashes to identify the hotspots and hot times.

Methods: Data for all vehicle–pedestrian crashes on public roadways in the Melbourne metropolitan area from 2004 to 2013 are used in this research. Spatial autocorrelation is applied in examining the vehicle–pedestrian crashes in geographic information systems (GIS) to identify any dependency between time and location of these crashes. Spider plots and kernel density estimation (KDE) are then used to determine the temporal and spatial patterns of vehicle–pedestrian crashes for different age groups and genders.

Results: Temporal analysis shows that pedestrian age has a significant influence on the temporal distribution of vehicle–pedestrian crashes. Furthermore, men and women have different crash patterns. In addition, results of the spatial analysis shows that areas with high risk of vehicle–pedestrian crashes can vary during different times of the day for different age groups and genders. For example, for those between ages 18 and 65, most vehicle–pedestrian crashes occur in the central business district (CBD) during the day, but between 7:00 p.m. and 6:00 a.m., crashes among this age group occur mostly around hotels, clubs, and bars.

Conclusions: This research reveals that temporal and spatial distributions of vehicle–pedestrian crashes vary for different pedestrian age groups and genders. Therefore, specific safety measures should be in place during high crash times at different locations for different age groups and genders to increase the effectiveness of the countermeasures in preventing and reducing vehicle–pedestrian crashes.     

Quantification of Hg excretion and distribution in biological samples of mercury-dental-amalgam users and its correlation with biological variables

This is the first study conducted to quantify the excretion and distribution of mercury (Hg) with time (days) in the biological samples collected from Hg dental amalgam users (MDA). The individuals, with Hg-based dental filling were selected, and their biological samples (red blood cells (RBCs), plasma, urine, hair, and nails) were collected on first, third, and 12th day of fillings. The concentrations of Hg observed in the biological samples of MDA were also correlated with the biological variables such as age, weight, restoration, fish consumption, number, and surface area of fillings. The concentrations of Hg in the biological samples of MDA were found 6–8 times higher than the non-amalgam users (control). The concentrations of Hg in the RBCs (4.39 μg/L), plasma (3.02 μg/L), and urine (22.5 μg/L) on first day of filling were found comparatively higher than the concentrations observed on third day (2.15, 1.46, and 12.3 μg/L for RBCs, plasma, urine, respectively) and 12th day (3.05, 2.5, 9.12 μg/L for RBCs, plasma, urine, respectively), while Hg concentrations were found lower in the hair and nails on third day of fillings (1.53 μg/g for hair and 2.35 μg/g for nails) as compared to the 12th day (2.95 μg/g for hair and 3.5 μg/g for nails). The correlations were found significant (p ˂ 0.05) between Hg concentrations in the biological samples of MDA and biological variables (the number of restoration, fish consumption, number, and surface area of fillings), while no significant (p ˃ 0.05) correlations were observed for Hg concentrations in the biological samples with age and weight of MDA. These observations unveil the fact that the use of Hg-based dental filling is the undesirable exposure to Hg which should be replaced by composite (a safer filling material).

     

The cut-off point for tympanic temperature as a heat strain index for evaluation of outdoor workers: a field study

Objectives. The aims of this study were (a) to assess the agreement coefficient between tympanic temperatures and the most popular and valid heat stress index, wet bulb globe temperature (WBGT), in outdoor environments; (b) to determine a cut-off point for tympanic temperature as a heat strain index for evaluation of outdoor workers. Methods. 1452 measurements of WBGT index and tympanic temperature were recorded for outdoor workers from nine different climatic regions. Consistency of the WBGT and tympanic temperature were tested. The cut-off point for tympanic temperature in outdoor environments regarding WBGT evaluation was suggested based on obtained sensitivity and specificity from a receiver operating characteristic curve. Results. The results showed that there were numerous situations in which WBGT exceeded the reference value, whilst the measured values of tympanic temperature rarely reached a permissible value for core temperature (38?°C). Therefore, appropriate consistency of results between the heat stress and strain indices was not achieved. Conclusion. The criterion of tympanic temperature equaling 37?°C was suggested as a cut-off point for tympanic temperature as a heat strain index for outdoor environment evaluation.     

高DOM渗滤液厌氧-好氧-混凝处理工艺

采用厌氧-好氧-混凝工艺,对垃圾焚烧厂高DOM渗滤液进行处理,当进水ρ(COD_Cr)平均值为10 800 mg/L时,出水ρ(COD_Cr)平均值可达208 mg/L;同时,着重针对各工艺单元出水DOM不同分子质量分布区间的ρ(COD_Cr)以及DOM组成成分的变化进行了研究.结果表明:该处理工艺对DOM分子质量＜50 ku的有机物去除率均可达到94.7%以上,而对分子质量＜2 ku的有机物的去除率可达99.0%;对渗滤液DOM组成成分〔腐殖酸(HA)、富里酸(FA)和亲水性有机质(HyI)〕的去除率均达到90.0%以上,表明该组合工艺用于处理垃圾焚烧厂渗滤液是可行的.      

Survey and determination of Anzali wetland trophic state through geographic information systems (GIS)

The trophic state of the Anzali wetland was determined by nutrient analysis, indicating an alarming hypertrophic state. The Anzali wetland is environmentally and economically one of the most important ecosystems that is located in north-west Iran. This wetland was registered as a Ramsar site in September 1975, but due to many problems, particularly eutrophication created by excessive amounts of nutrients, it was registered in the Montreux record. This study was conducted for a year on 21 stations in three zones including receiving rivers, surface water and exiting rivers. Geographic information systems were used to better understand the prevailing situation. Analysis was conducted according to international standards and classification of OECD for freshwaters. The indicators used were levels of total nitrogen (TN) and total phosphorous (TP), and the trophic state index (TSI). Data showed an increase of excess nutrients from domestic and agricultural sources, leading to human, cultural eutrophication processes rather than natural eutrophication.     

Release of beryllium from mineral ores in artificial lung and skin surface fluids

Exposure to some manufactured beryllium compounds via skin contact or inhalation can cause sensitization. A portion of sensitized persons who inhale beryllium may develop chronic beryllium disease (CBD). Little is understood about exposures to naturally occurring beryllium minerals. The purpose of this study was to assess the bioaccessibility of beryllium from bertrandite ore. Dissolution of bertrandite from two mine pits (Monitor and Blue Chalk) was evaluated for both the dermal and inhalation exposure pathways by determining bioaccessibility in artificial sweat (pH 5.3 and pH 6.5), airway lining fluid (SUF, pH 7.3), and alveolar macrophage phagolysosomal fluid (PSF, pH 4.5). Significantly more beryllium was released from Monitor pit ore than Blue Chalk pit ore in artificial sweat buffered to pH 5.3 (0.88 ± 0.01% vs. 0.36 ± 0.00%) and pH 6.5 (0.09 ± 0.00% vs. 0.03 ± 0.01%). Rates of beryllium released from the ores in artificial sweat were faster than previously measured for manufactured forms of beryllium (e.g., beryllium oxide), known to induce sensitization in mice. In SUF, levels of beryllium were below the analytical limit of detection. In PSF, beryllium dissolution was biphasic (initial rapid diffusion followed by latter slower surface reactions). During the latter phase, dissolution half-times were 1,400 to 2,000 days, and rate constants were ~7 × 10⁻¹⁰ g/(cm²·day), indicating that bertrandite is persistent in the lung. These data indicate that it is prudent to control skin and inhalation exposures to bertrandite dusts.     

Distribution,geochemistry, and mineralogy of aerosols in the Angouran Mine area,northwest Iran

The Angouran Mine, located in northwest Iran, is the largest Zn–Pb producer in the Middle East. This study was designed to investigate the distribution, geochemistry, and mineralogy of the aerosols in the mining area and to assess their likely health impacts on the local residents. For this purpose, 36 aerosol samples were collected from 2014 to 2015 at nine sites located in mine district and upwind and downwind directions. The concentration of potentially toxic elements in the aerosols was determined using AAS instrument. Size, morphology, and mineralogy of the particles were studied using SEM and EDX spectra. The results indicate that the amount of total suspended particles in upwind, mine district, and downwind sites is 95.5, 463.4 and 287.5 µg/m³, respectively. The concentrations of PM_2.5 in the three locations are 8.9, 134.7, and 51.8 µg/m³, whereas the PM₁₀ contents are 2.9, 74.4, and 15.5 µg/m³, respectively. These observations point to the impact of mining activities on the concentration of aerosols in the local atmosphere. The values of air quality index also show the probable effects of the mining activities on the health of the local populations, especially for allergic peoples. The average concentration of Zn in the samples collected from the mining district (290 µg/kg) is much higher than its value in the upwind sites (27 µg/kg). The highest concentration of As (70 µg/kg), Cd (10 µg/kg), and Pb (3 µg/kg) is in downwind sites, which shows the negative impact of mining activities on the local air quality. Temporally, the highest concentration of the studied elements is recorded in spring season, especially for PM_2.5 collected in downwind stations. Based on the results of SEM and EDX spectra, three groups of minerals, i.e., carbonates, silicates, and sulfides, are present in the aerosol particles, confirming the local source for the aerosols. SEM analyses showed that the aerosol particles with dissimilar chemical composition have different morphologies such as irregular, rounded, elongated, and angular. On the basis of the results, the mining activities in the Angouran Zn–Pb Mine may have various short- and long-term consequences on the public health, especially due to high amount of the finer particles (PM_2.5) and the higher concentration of the potentially toxic elements in PM_2.5 which can penetrate into the lungs.

     

Polycyclic aromatic hydrocarbon derivatives in airborne particulate matter: sources,analysis and toxicity

Polycyclic aromatic hydrocarbons (PAHs) are worldwide pollutants produced mainly during incomplete combustion and pyrolysis of organic substances. PAH derivatives are components with hydrogen on the aromatic ring substituted by carbonyl-, nitro- and hydroxyl-functional groups (N-PAH, O-PAH or OH-PAH), or a group of heterocyclic PAHs containing one sulfur atom in place of a carbon atom in the aromatic ring. PAHs and their derivatives can be either introduced in the atmosphere directly in this form as primary pollutants, or formed by homogenous and heterogeneous oxidation reactions. During the last decades, interest on studying PAH derivatives has increased because derivatives may be more harmful than parent compounds. PAH derivatives have been detected in the atmospheric particulate matter in numerous cities worldwide. PAH derivatives enter living organisms by inhalation, oral ingestion and dermal contact. In vivo and in vitro experiments together with epidemiological studies have shown the toxic effects of PAH derivatives, notably for compounds present in airborne and diesel exhaust particles. Here we review the sources, the mechanisms of formation, the physicochemical properties, the analytical methods, and the toxicological effects of PAHs and their derivatives in airborne particulate matter.     

Enhanced catalytic complete oxidation of 1,2-dichloroethane over mesoporous transition metal-doped γ-Al2O3

High-surface-area mesoprous powders of γ-Al₂O₃ doped with Cu²⁺, Cr³⁺, and V³⁺ ions were prepared via a modified sol-gel method and were investigated as catalysts for the oxidation of chlorinated organic compounds. The composites retained high surface areas and pore volumes comparable with those of undoped γ-Al₂O₃ and the presence of the transition metal ions enhanced their surface acidic properties. The catalytic activity of the prepared catalysts in the oxidation of 1,2-dichloroethane (DCE) was studied in the temperature range of 250-400℃. The catalytic activity and product selectivity were strongly dependent on the presence and the type of dopant ion. While Cu²⁺- and Cr³⁺-containing catalysts showed 100% conversion at 300℃ and 350℃, V³⁺-containing catalyst showed considerably lower conversion. Furthermore, while the major products of the reactions over γ-alumina were vinyl chloride (C₂H₃Cl) and hydrogen chloride (HCl) at all temperatures, Cu- and Cr-doped catalysts showed significantly stronger capability for deep oxidation to CO₂.