Spillover effects of trade and foreign direct investment on economic growth: an implication for sustainable development

Environment, Development and Sustainability - This paper explores the advantages of international trade and foreign direct investment (FDI), which can be the main factors of transferring technology...     

Exposure to methyl methacrylate and its subjective symptoms among dental technicians, Tehran, Iran.

Exposure to methyl methacrylate (MMA), total dust and health symptoms were investigated in 20 dental laboratories located in Tehran, Iran. Time-weighted average (TWA) of MMA and peak concentrations were determined, using XAD-2 tubes followed by GC-FID analysis. Total dusts were evaluated gravimetrically. Health symptoms were asked using a questionnaire. TWA for technicians with direct and indirect exposure to MMA were 327.28 +/- 79.42 and 282.9 +/- 41.84 mg/m3, respectively. Peak concentration of MMA for those technicians were 337.0 +/- 36.81 and 328.88 +/- 45.40 mg/m3, respectively. There were no significant differences between TWA of MMA and peak concentration in different weekly workdays; however, within-day variations were observed (P < .05). TWA of MMA and peak concentration correlation with the laboratory volume were 0.61-0.65. Dust exposure of technicians was 2.35 +/- 2.70 mg/m3. Cough and skin dryness were the common health symptoms. Smoking and asbestos exposure history were factors influencing cough prevalence (p < .05). It is concluded that the current Short-Term Exposure Limit (STEL) is not low enough to protect technicians against the adverse effects caused by MMA.     

Toward a robust analytical method for separating trace levels of nano-materials in natural waters: cloud point extraction of nano-copper(II) oxide

Cloud point extraction (CPE) factors, namely Triton X-114 (TX-114) concentration, pH, ionic strength, incubation time, and temperature, were optimized for the separation of nano-sized copper(II) oxide (nCuO) in aqueous matrices. The kinetics of phase transfer was studied using UV–visible spectroscopy. From the highest separation rate, the most favorable conditions were observed with 0.2 %?w/v of TX-114, pH?=?9.0, ionic strength of 10 mM NaCl, and incubation at 40 °C for 60 min, yielding an extraction efficiency of 89.2?±?3.9 % and a preconcentration factor of 86. The aggregate size distribution confirmed the formation of very large nCuO–micelle assemblies (11.9 μm) under these conditions. The surface charge of nCuO was also diminished effectively. An extraction efficiency of 91 % was achieved with a mixture of TX-100 and TX-114 containing 30 wt.% of TX-100. Natural organic and particulate matters, represented by humic acid (30 mg/L) and micron-sized silica particles (50 mg/L), respectively, did not significantly reduce the CPE efficiency (<10 %). The recovery of copper(II) ions (20 mg/L) in the presence of humic acid was low (3–10 %). The spiked natural water samples were analyzed either directly or after CPE by inductively coupled plasma mass spectrometry following acid digestion/microwave irradiation. The results indicated the influence of matrix effects and their reduction by CPE. A delay between spiking nCuO and CPE may also influence the recovery of nCuO due to aggregation and dissolution. A detection limit of 0.04 μg Cu/L was achieved for nCuO.     

Influence of preparation method on structural,optical, magnetic,and adsorption properties of nano-NiFe2O4

Nickel ferrite (NiFe₂O₄) nanoparticles are prepared through different routes (microwave, co-precipitation, and pyrolysis) and tested for water purification applications through adsorption removal of an acid red dye B as a model organic pollutant. The characterizations of the prepared samples were done using XRD, FT-IR, SEM, TEM, BET, UV-Vis absorbance, Raman spectrum, and vibrating sample magnetometer (VSM). All samples showed an inverse spinel crystal structure. The obtained results pointed out to the effect of the synthetic route on the morphology, particle size, optical, and magnetic properties of the prepared ferrites. Magnetic measurements showed super-paramagnetic behavior for all samples. The magnetic saturation (M_s) of the sample prepared by pyrolysis, was found to possess the highest saturation value, 34.8 emu/g. Adsorption experiments were performed under the change in several parameters, such as pH, adsorbent dosage, and initial dye concentration. A dye removal percentage of 99% was reached under the optimum state. The isothermal adsorption of the acid red dye was investigated using several models, in which the experimental data could be best described by the Freundlich model. Several kinetic and equilibrium models were inspected by linear regression analysis and showed best fitting for the adsorption data through pseudo-second-order model. The calculated thermodynamic parameters indicated that the adsorption of acid red dye onto all the ferrite samples is a spontaneous and endothermic physical adsorption process.

     

Biodegradation of low-density polyethylene (LDPE) by isolated fungi in solid waste medium

In this study, biodegradation of low-density polyethylene (LDPE) by isolated landfill-source fungi was evaluated in a controlled solid waste medium. The fungi, including Aspergillus fumigatus, Aspergillus terreus and Fusarium solani, were isolated from samples taken from an aerobic aged municipal landfill in Tehran. These fungi could degrade LDPE via the formation of a biofilm in a submerged medium. In the sterilized solid waste medium, LPDE films were buried for 100 days in a 1-L flask containing 400 g sterile solid waste raw materials at 28 °C. Each fungus was added to a separate flask. The moisture content and pH of the media were maintained at the optimal levels for each fungus. Photo-oxidation (25 days under UV-irradiation) was used as a pretreatment of the LDPE samples. The progress of the process was monitored by measurement of total organic carbon (TOC), pH, temperature and moisture. The results obtained from monitoring the process using isolated fungi under sterile conditions indicate that these fungi are able to grow in solid waste medium. The results of FT-IR and SEM analyses show that A. terreus and A. fumigatus, despite the availability of other organic carbon of materials, could utilize LDPE as carbon source. While there has been much research in the field of LDPE biodegradation under solid conditions, this is the first report of degradation of LDPE by A. fumigatus.     

Investigation of PM2.5 and carbon dioxide levels in urban homes

PM_2.5 (particulate matter with an aerodynamic diameter <2.5 μm) samples were collected in the indoor environments of 15 urban homes and their adjacent outdoor environments in Alexandria, Egypt, during the spring time. Indoor and outdoor carbon dioxide (CO₂) levels were also measured concurrently. The results showed that indoor and outdoor PM_2.5 concentrations in the 15 sites, with daily averages of 45.5 ± 11.1 and 47.3 ± 12.9 µg/m³, respectively, were significantly higher than the ambient 24-hr PM_2.5 standard of 35 µg/m³ recommended by the U.S. Environmental Protection Agency (EPA). The indoor PM_2.5 and CO₂ levels were correlated with the corresponding outdoor levels, demonstrating that outdoor convection and infiltration could lead to direct transportation indoors. Ventilation rates were also measured in the selected residences and ranged from 1.6 to 4.5 hr^?1 with median value of 3.3 hr^?1. The indoor/outdoor (I/O) ratios of the monitored homes varied from 0.73 to 1.65 with average value of 0.99 ± 0.26 for PM_2.5, whereas those for CO₂ ranged from 1.13 to 1.66 with average value of 1.41 ± 0.15. Indoor sources and personal activities, including smoking and cooking, were found to significantly influence indoor levels.

Implications: Few studies on indoor air quality were carried out in Egypt, and the scarce data resulted from such studies do not allow accurate assessment of the current situation to take necessary preventive actions. The current research investigates indoor levels of PM_2.5 and CO₂ in a number of homes located in the city of Alexandria as well as the potential contribution from both indoor and outdoor sources. The study draws attention of policymakers to the importance of the establishment of national indoor air quality standards to protect human health and control air pollution in different indoor environments.     

Hair as a marker for pesticides exposure

Rats were orally treated with mixtures of chlorinated pesticides. Hair was collected and analyzed for pesticide residues over a period of up to four weeks. Quantitative and qualitative analysis of the recovered pesticides in hair were determined using gas chromatography with electron capture detector. Results suggest that hair can be used as a biomarker for the monitoring of organochlorinated pesticide residues at low parts per billion levels. Chlorinated pesticides were also detected in human hair of environmentally exposed and occupationally exposed individuals, which indicates that hair can be used for monitoring pesticides exposure.