Constructed wetlands (CWs) have been applied to remediate heavy metal pollution effectively in practice. However, the heavy metal release from CWs has not been paid enough attention. In this study, a 5-month experiment was carried out with three parallel lab-scale vertical flow constructed wetlands (VFCWs) with zeolites as fillers. The artificial rainwater was pumped into VFCWs to study the release characteristic and mechanisms of heavy metals (Cu, Zn, Cr, and Pb). The results showed that significant amounts of Zn and Cu were released from the VFCWs at the end of the experiment while Pb and Cr rarely escaped. The upper layer (0–30 cm) of the VFCWs was the most effective area for heavy metal removal due to the presence of sediments, but it was also the most active area for heavy metal release. To explain this result, the sediments were analyzed before and after being leached by the tap water. The results indicated that Zn and Cu existed mainly in the exchangeable state, and they had strong leachability and bioavailability, causing its releases. Also, competitive adsorption of different metals meant that the metal ions with strong adsorption to zeolite caused the metal ions with weak adsorption to be desorbed from zeolites, and thus, a large amount of Zn escaped from VFCWs. The escape of heavy metals from CWs illustrated that it should be paid more attention in the management.

The main aims of the present research were (1) investigation of the temporal trends of atmospheric benzene concentrations in Tehran city during the period 2010 to 2013 and (2) assessment of carcinogenic and non-carcinogenic health risks of inhalation exposure to benzene. For the first objective, the data of ambient air benzene concentrations were derived from 15 air quality monitoring stations (AQMSs) in Tehran during the years 2010 to 2013 and they were temporally investigated after data cleaning and missing data imputation. The excess lifetime cancer risk (ELCR) and hazard quotient (HQ) were estimated to reveal the carcinogenic and non-carcinogenic health effects of exposure to ambient benzene. Our findings indicated that over 2010–2013, annual mean concentrations of benzene were in the range of 1.84 to 2.57 μg m⁻³, and the highest annual mean concentration was observed in 2011 with a mean of 2.57 μg m⁻³. The four-year average concentration of benzene during the period from 2010 to 2013 was 2.14 μg m⁻³. Furthermore, the HQ for inhalation exposure to ambient benzene was lower than the acceptable risk level (HQ < 1) over the study time period which indicated that the non-carcinogenic effects are very unlikely to happen. In addition, health risk assessment for ELCR showed that the potential cancer risk for inhalation exposure to benzene was 1.67 × 10⁻⁵ over the study period, which is significantly higher than the limits recommended by the U.S. EPA (1 × 10⁻⁶). Our study clearly proves that the ambient benzene concentration in Tehran has substantially higher carcinogenic effects on the population. Appropriate sustainable control measures should be taken to reduce air benzene concentration and protect public health.

This study aims to analyze the impact of financial development, foreign direct investment, economic growth, electricity consumption, and trade openness on environmental quality for a panel of 59 Belt and Road Initiative (BRI) countries, over the period of 1980–2016. The presence of the environmental Kuznets curve (EKC) hypothesis is investigated. The cross-sectional augmented Dickey-Fuller (CADF) and cross-sectional Im, Pesaran, and Shin panel unit root test; the Westerlund cointegration test, the dynamic seemingly unrelated regression (DSUR) approach; and the Dumitrescu and Hurlin (Econ Model 29:1450–1460, 2012) panel causality approach are employed. It is found that the analyzed variables are stationary at first differences and are cointegrated. It is also found that an increase in financial development, foreign direct investment, and trade openness enhance environmental quality, while the increase in economic growth and electricity consumption degrade environmental quality. The presence of the EKC hypothesis for the selected panel countries is validated. Furthermore, the Dumitrescu-Hurlin (DH) panel causality test result confirmed the presence of bidirectional causality among economic growth, foreign direct investment, financial development, electricity consumption, and trade openness with environmental quality.

In this work, the novel direct synthesis method of dimethylacetamide-based graphene oxide (GO) was performed through electrochemical exfoliation assisted by commercially available single-tail sodium dodecyl sulphate (SDS) surfactant. Then, the synthesised GO (SDS–GO) was incorporated into polyvinylidene fluoride (PVDF) solution to produce a nanofiltration (NF) membrane through the phase immersion method. The addition of GO into the preparation of membrane solution alters the membrane morphology and improves the hydrophilicity. TiO₂ was also used as an additive for the NF membrane fabrication to further increase the membrane hydrophilicity. The fabricated PVDF/SDS–GO/TiO₂ and PVDF/SDS–GO NF membranes were compared with pure PVDF membrane. Then, the fabricated NF membranes were tested for methylene blue (MB) rejection with 10 ppm MB concentration. On the basis of the dead-end cell measurement operated at the pressure of 2 bar, the PVDF/SDS–GO/TiO₂ presents high MB rejection (92.76%) and the highest dye flux (7.770 L/m² h). This dye flux value was sevenfold higher than that of pure PVDF membrane (1.146 L/m² h) which was due to the utilisation of both GO and TiO₂ that improved the membrane hydrophilicity as indicated by the lowest contact angle (64.0 ± 0.11°). High porosity (57.46%) also resulted in the highest water permeability (4.187 L/m² h bar) of the PVDF/SDS–GO/TiO₂ NF membrane.

Sponge gourd (Luffa aegyptiaca) was grown in pots with and without inoculation with two arbuscular mycorrhizal (AM) fungi, viz., Glomus macrocarpum and Glomus monosporum singly and in combination. Seven-day-old plants were treated with 18.9 μg Cd g⁻¹ soil and 155.4 μg Ni g⁻¹ soil alone and in combination. At 90 days old stage, dry weight of root, shoot, and fruit; uptake of heavy metals in root, stem, leaves, and fruits; percent mycorrhizal root colonization; and spore number in the root zone were determined. When applied singly, the uptake of Cd and Ni in host plants was enhanced more effectively by G. monosporum than G. macrocarpum. The larger proportion of Cd uptake in uninoculated host was retained in the roots but in inoculated plants (with both Glomus sp.), major amounts of the Cd were translocated to the above ground parts including fruits. The leaves were the main sinks of Ni in inoculated plants. The overall tissue burden of both heavy metals in the host was enhanced relatively more effectively on association with G. monosporum as compared with G. macrocarpum. The uptake of Cd was relatively higher in plants treated with both the metals and both the AM fungi. Despite the relatively higher uptake of both the heavy metals in inoculated plants, the host dry weight was significantly higher compared with uninoculated plants. The percent mycorrhizal root colonization of the host by both AM fungi was higher in plants grown without either of the heavy metals. The combined application of both the heavy metals reduced the spore density in the root zone soil of host. The results show that the AM fungi enhanced the uptake of Cd and Ni by the host but alleviated the toxicity by promoting plant growth.

In light of growing concern and insufficient knowledge on the negative impact of aircraft emissions on environmental health, this study strives to investigate the air burden of major and trace elements caused by general aviation, piston-engine, and turboprop aircraft, within the vicinity of Eskisehir Hasan Polatkan Airport (Eskisehir, Turkey). The levels of 57 elements were investigated, based on moss bag biomonitoring using Sphagnum sp., along with chemical analyses of lubrication oil and aviation gasoline fuel used in the aircraft’s operations. Five sampling sites were selected within the vicinity of the airport area to capture spatial changes in the concentration of airborne elements. The study demonstrates that moss bag biomonitoring is a useful tool in the identification of differences in the air burden by major and trace elements that have concentrated downwind of the aircraft emission sources. Moreover, pollutant enrichment in the Sphagnum moss bags and elemental characterization of oil/fuel are in agreement suggesting that Pb, followed by Cd, Cu, Mo, Cr, Ni, Fe, Si, Zn, Na, P, Ca, Mg, and Al are dominant elements that shaped the general aviation aircraft emissions.

The process of growth of algae can be described using the images from microscopic analysis. The new approach to assessment of the growth dynamics of algae used the data of granulometric composition of liquid medium and the modified Avrami equation relating to the crystallisation process. This paper presents a comparison of both methods (granulometric and microscopic) for the analysis of the dynamics of changes in the growth of algae in wastewater. The experimental set-up consisted of four glass tanks filled with biologically treated sewage, in which algae grew. The cultivation of algae was carried out for 8 weeks. During this period, the granulometric analysis and microscopic observations of sewage were conducted. The study demonstrated that with increase in the size of flocs in treated sewage, biomass of algae was also increased. Therefore, the results obtained with the method of laser diffraction are in agreement with microscopic observation of flocs. Granulometric analysis could be, next to microscopic analysis, a method for the estimation of the dynamics of changes in the growth of algae in sewage. This knowledge will allow to selection of a suitable method of wastewater treatment and algal separation.

Two smelters in the North of France emitted potentially toxic metals for more than a century and today, the resulting contamination represents a risk to human health and affects also the biodiversity. To limit health risks and to improve the soil quality, a study using calcium phosphates (monocalcium phosphate, dicalcium phosphate and a mixture of both salts) and Lolium perenne L was conducted. Through this preliminary investigation, we will try to shed some light about (i) the effects of a sustainable amount of calcium phosphates on the agronomic, biological (microbial and fungi communities) and physiological parameters (chlorophyll a and b, antocyanins, carotenoids) as well as the phytoavailability of potentially toxic metals and nutrients in time, and (ii) the potential use of contaminated biomass from ryegrass as a source of new valorisation ways instead of using it as contaminated compost by gardeners. Although slight variations in pH and significant increases of assimilable phosphorus after adding calcium phosphates were registered, the physiology of plants and the biological parameters were statistically unchanged. The germination of the ryegrass seeds was favoured with calcium phosphates regardless the contamination level of the studied soils. No clear effects of calcium phosphates on the microbial and fungi communities were detected. In contrast, results indicated relationships between the physicochemical parameters of soils, their contamination level and the composition of fungal communities. Indeed, for one of the soils studied, calcium could limit the transport of nutrients, causing an increase in fungi to promote again the transfer of nutrients. Surprisingly, the phytoavailability of Pb increased in the most contaminated soil after adding dicalcium phosphate and the mixture of phosphates whereas a slight decrease was highlighted for Cd and Mn. Although minor changes in the phytoavailability of potentially toxic metals were obtained using calcium phosphates, the ability of ryegrass to accumulate Zn and Ca (up to 600 and 20,000 mg kg⁻¹, respectively) make possible to qualify this plant as a bio ‘ore’ resource.

This study investigates levels of bacteria through population indicators as well as the levels of antibiotic-resistance bacteria in dairy manure. Although overall bacteria levels may be reduced during manure processing, it is of interest whether changes in management practices could lead to increased levels of antibiotic-resistance bacteria, which are becoming more prevalent in agricultural soils, groundwater, and surface water. Appropriate manure treatments are needed not only to reduce the potential risk of exporting antibiotic-resistant bacteria to an environment, but also reduce antibiotic-resistant bacteria exposure to animals if processed water is recycled. Results from this research revealed manure separation under relatively low speed centrifuge with 100 ppm polyacrylamide (PAM) emulsion addition reduced bacteria indicators population such as total coliforms and Escherichia coli (E. coli) significantly in the liquid stream compared to no PAM added. However, the percentages of antibiotic-resistant isolates in liquid stream after centrifuge with PAM were higher compared to raw manure and no PAM added. Antibiotic resistance (cephalosporin, florfenicol, penicillin, or tetracycline) was observed or 65.38% of bacterial isolates in manure from a large dairy farm in Wisconsin and 39.29% of isolates demonstrated multidrug resistance. The results from this study strongly suggest that appropriate manure treatment is essential in order to help minimize the abundance of antibiotic resistance in our water environment.