Introduction: This study aimed to calculate and evaluate air quality index (AQI) in Tehran according to the EPA’s instruction, and evaluate the obtained values. Materials and methods: The study period included three years of 2013, 2015, and 2017 within the six-year period of 2013-2017. The concentrations of six studied pollutants were acquired from Department of Environment (DE) and Air Quality Control Company of Tehran (AQCC). EPA’s method was applied to calculate AQI values during the study period, selecting the highest AQI value among all of the pollutants and monitors. Results: The three-year average of AQI was about 147. During all the three years, the air quality had never been in a “good” condition (AQI<50). About 92%, 91%, 87% of AQIs indicated the conditions unhealthy for sensitive groups (100<AQI<150) or unhealthy for all groups (150<AQI<200). PM2.5 accounted for most of the AQI values in Tehran, followed by NO2 and O3. Evaluating the histogram of AQI values indicated a strange form of distribution, showing a decline in the 100-150 range and a sudden increase just after AQIs higher than 150. Conclusion: This study indicated that governmental organizations should follow EPA’s instruction for AQI calculations to avoid underestimation of air pollution, and broadcast accurate and reliable AQIs to public. To determine the reason for the abnormal distribution of AQI, further studies with longer study periods are required.

Introduction: Exposure to benzene has been associated with a range of acute and long-term adverse health effects. We aimed to estimate national and provincial level of benzene emissions from 1990 to 2013 in Iran. Materials and methods: Benzene emission was estimated through two main sources: unburned benzene content of fuel and evaporated benzene. Unburned benzene content of fuel estimated by gasoline consumption rate, kilometers traveled by non-diesel-based cars, and benzene emission factor. Evaporated benzene estimated by evaporated gasoline and volumetric percentile of benzene. Results: The estimated provincial annual mean benzene estimation range was between 5.9  (ton) and 1590 (ton) from 1990 to 2013. Our results showed that maximum benzene emission over the past 24 years occurred in Tehran, Mean (SD) ((1147.23(308.57) (ton)), Isfahan ((423.45(132) (ton)), Khorasan Razavi) (410.48(122.23) (ton)) provinces, respectively. There was an upward trend in the benzene emission into atmosphere at national and subnational level from 1990 to 2007. Also a significant decrease trend is observed from 2008 to 2013. Conclusion: The findings of this study will provide an insight into the extent of emitted benzene in the atmosphere at different regions of Iran for policy makers and scientists and may be a groundwork for field studies on benzene concentration estimation.

Developing fetus is connected to the mother by placenta to receive oxygen and nutrients. Maternal exposure to ambient air pollution not only affects maternal health but also provides a pathway for many toxic pollutants to cross the placental barrier and interrupt biochemical milieu. There are numerous scientific studies available describing possible negative health impact of air pollutants on reproductive health, pregnancy outcomes and fetal development yet no toxic effect is available recently. Studying the pollutants exposure effect on fetal development is crucial for the underlying mechanism between prenatal exposure and pregnancy outcomes. Present review meticulously provides the compiled data of 40 most recent studies with possible action mechanism of air pollutants on pregnancy outcomes and fetal development to find a better solution to exterminate or reduce the problem.

Introduction: The wide range of studies on air pollution requires accurate and reliable datasets. However, due to many reasons, the measured concentrations may be incomplete or biased. The development of an easy-to-use and reproducible exposure assessment method is required for researchers. Therefore, in this article, we describe and present a series of codes written in R Programming Language for data handling, validating and averaging of PM10, PM2.5, and O3 datasets. Findings: These codes can be used in any types of air pollution studies that seek for PM and ozone concentrations that are indicator of real concentrations. We used and combined criteria from several guidelines proposed by US EPA and APHEKOM project to obtain an acceptable methodology. Separate .csv files for PM10, PM2.5 and O3 should be prepared as input file. After the file was imported to the R Programming software, first, negative and zero values of concentrations within all the dataset will be removed. Then, only monitors will be selected that have at least 75% of hourly concentrations. Then, 24-h averages and daily maximum of 8-h moving averages will be calculated for PM and ozone, respectively. For output, the codes create two different sets of data. One contains the hourly concentrations of the interest pollutant (PM10, PM2.5, or O3) in valid stations and their average at city level. Another is the final 24-h averages of city for PM10 and PM2.5 or the final daily maximum 8-h averages of city for O3. Conclusion: These validated codes use a reliable and valid methodology, and eliminate the possibility of wrong or mistaken data handling and averaging. The use of these codes are free and without any limitation, only after the citation to this article.

Bioelectrochemical systems (BESs) have great potential for treating wastewater containing polycyclic aromatic hydrocarbons (PAHs); however, detailed data on cell physiological activities in PAH biodegradation pathways stimulated by BESs are still lacking. In this paper, a novel BES device was assembled to promote the growth of Pseudomonas sp. DGYH-12 in phenanthrene (PHE) degradation. The results showed that in the micro-electric field (0.2 V), cell growth rate and PHE degradation efficiency were 22% and 27.2% higher than biological control without electric stimulation (BC), respectively. The extracellular polymeric substance (EPS) concentration in BES (39.38 mg L⁻¹) was higher than control (33.36 mg L⁻¹); moreover, the membrane permeability and ATPase activities were also enhanced and there existing phthalic acid and salicylic acid metabolic pathways in the strain. The degradation genes nahAc, pcaH, and xylE expression levels were upregulated by micro-electric stimulation. This is the first study to analyze the physiological and metabolic effect of micro-electric stimulation on a PHE-degrading strain in detail and systematically.

Fertilization and straw return have been widely adopted to maintain soil fertility and increase crop yields, but their long-term impacts on the accumulation and availability of cadmium (Cd) in paddy soils are still unconfirmed. Therefore, this study was undertaken in central China to investigate the accumulation, availability, and subsequent uptake of Cd by rice (Oryza sativa L.) in two adjacent field trials (P1 and P2, lasting for 10 and 12 years, respectively) under long-term straw return or in combination with chemical fertilizers. Obvious Cd accumulation, probably due to the notable Cd input from irrigation and traffic exhaust in the bulk soil (0–20 cm) of P1, was observed. The bulk soil of P2 received homogeneous straw return and chemical fertilizers, as did that of P1; however, the P2 soil almost showed Cd balance. Long-term straw return increased the portion of soil DTPA-extractable Cd to the total pool for both sites, but only P1 showed significant differences when compared to the controls. However, the highest Cd concentrations and the maximum bioconcentration factors in rice straw and grain were obtained using solo application of chemical fertilizers at both sites. Continuous additional applications of crop straw, in contrast, resulted in slightly decreased Cd uptake in rice straw, but not in grain. These findings demonstrate that neither long-term straw return nor fertilization leads directly to notable Cd accumulation, but that the promotion effects of long-term chemical fertilizer applications on Cd uptake in rice need more attention.

Anaerobic digestion (AD) is one of the best technologies for producing methane from biomass wastes with limited environmental impacts. Most AD plants need a continuous and stable supply of feedstock for their sustained operation for which lignocellulosic biomass can be effectively utilized. Switchgrass (SG), also known as Panicum virgatum, is a tall-growing grass which exists throughout the year in areas with warm climate and has the potential to produce biomethane. The present work investigated anaerobic digestion performance of SG while focusing on enhancing the methane yield by employing central composite design of response surface methodology (RSM). The aim of this research was to find out the best level of factors including feed-to-inoculum (F/I) ratio, organic loading (OL), and pH for optimizing the desired output of biomethane production from 3% KOH–pretreated SG. Results revealed that the highest value of experimental methane yield was 288.4 mL/gVS at the optimal F/I ratio, pH, and OL of 1, 6.96, and 24 gVS/L, respectively. Moreover, 3% KOH pretreatment improved the biodegradability of SG significantly from 14.23 to 85.53%. This study forms the basis for future application of SG for enhanced methane production.

Fenton’s reaction-based chemical oxidation is in principle a method that can be utilized for all organic fuel residues thus making it a potential all-purpose, multi-contaminant, in situ application for cases in which storage and distribution of different types of fuels have resulted in contamination of soil or groundwater. Since peroxide breakdown reactions are also expected to lead to a physical transport of the target compound, this secondary physical removal, or rebound concentrations related to it, is prone to be affected by the chemical properties of the target compound. Also, since soil conditions are seldom optimal for Fenton’s reaction, the balance between chemical oxidation and transport may vary. In this study, it was found that, with a high enough hydrogen peroxide concentration (5 M), methyl tert-butyl ether–spiked groundwater could be treated even under suboptimal conditions for chemical mineralization. In these cases, volatilization was not only contributing to the total removal but also leading to rebound effects similar to those associated with air sparging techniques. Likewise for diesel, temporal transport from soil to the aqueous phase was found to lead to false positives that outweighed the actual remediation effect through chemical mineralization.

Sediments are known to be the ultimate sink for most pollutants in the aquatic environment. In this study, the concentrations of both legacy polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs) were measured in sediments samples from the Vaal River catchment. The concentrations of Σ₇BDE-congeners ranged from 20 to 78 ng g⁻¹ dry weight (dw) with BDE-209, -99, and -153 as the dominant congeners. The concentrations observed ranged from 9.4–56, 4–32, and 1–10.6 ng g⁻¹ for BDE-209, -99, and -153, respectively. The concentrations of AHFRs, mainly contributed by decabromodiphenyl ethane (DBDPE) at approximately 95% of total AHFRs, ranged from 64 to 359 ng g⁻¹ dw while the concentration of polybrominated biphenyls (PBBs), mainly PBB-209, ranged from 3.3–7.1 ng g⁻¹ dw. The ratios of AHFRs to PBDEs observed in this study were 0.76, 1.17, and 7.3 for 2-ethyl-1-hexyl-2,3,4,5-tetrabromobenzoate and bis-(2-ethylhexyl)-tetrabromophthalate (EH-TBB & BEH-TEBP)/penta-BDE; 1,2-bis-(2,4,6-tribromophenoxy) ethane (BTBPE)/octa-BDE; and DBDPE/BDE209, respectively. These results indicate dominance of some AHFRs compared to PBDEs. Our results indicates that BDE-99 poses high risk (RQ > 1) while BDE-209 posed medium risk (0.1 < RQ < 1). Though the concentration of DBDPE was several orders of magnitude higher than BDE209, its ecological risk was found to be negligible (RQ < 0.01). Thus, more attention is required to regulate the input (especially the e-waste recycling sites) of brominated flame retardants into the environment.