This study investigated the soil pollution level and evaluated the phytoremediation potential of 25 native plant species on a former gold mine-tailing site in Ghana. Plant shoots and associated soil samples were collected from a tailing deposition site and analyzed for total element concentration of As, Hg, Pb, and Cu. Soil metal(loid) content, bioaccumulation factor (BAFₛₕₒₒₜₛ), and hyperaccumulator thresholds were also determined to assess the current soil pollution level and phytoextraction potential. The concentration of As and Hg in the soil was above international risk thresholds, while that of Pb and Cu were below those thresholds. None of the investigated plant species reached absolute hyperaccumulator standard concentrations. Bioavailability of sampled metal(loid)s in the soil was generally low due to high pH, organic matter, and clay content. However, for Cu, relatively high bioaccumulation values (BAFₛₕₒₒₜₛ > 1) were found for 12 plant species, indicating the potential for selective heavy-metal extraction via phytoremediation by those plants. The high levels of As at the study site constitute an environmental and health risk but there is the potential for phytoextraction of Cu (e.g., Aspilia africana) and reclamation by afforestation using Leucaena leucocephala and Senna siamea.

Despite the controversy, the ecological risk of microplastics research has increased sharply from only one in 1966 to 495 in 2018, according to Web of Science with microplastics as keyword. To date, an upward trend of global microplastics mass emission was confirmed by many environmental scientists. The ocean is the ultimate destination of land-based microplastics sources; therefore, most of efforts were concentrated on microplastics in aquatic environment. In this brief article, the global release of microplastics and flux into the ocean in the recent decade were estimated roughly. The plastics fragmentation in the marine environment only accounted for 22% of total microplastics release (assuming defined emission rate per capita and fragmentation rate of plastics). Future research is needed for microplastics generation and retention in the terrestrial system, especially indoor environments. The accumulated microplastics over the environmental self-purification capacity certainly increases stress for the marine, freshwater and terrestrial ecosystem.

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.

Biological reduction is an effective method for removal of perchlorate (ClO₄⁻), where perchlorate is transformed into chloride by perchlorate-reducing bacteria (PRB). An external electron donor is required for autotrophic and heterotrophic reduction of perchlorate. Therefore, plenty of suitable electron donors including organic (e.g., acetate, ethanol, carbohydrate, glycerol, methane) and inorganic (e.g., hydrogen, zero-valent iron, element sulfur, anthrahydroquinone) as well as the cathode have been used in biological reduction of perchlorate. This paper reviews the application of various electron donors in biological perchlorate reduction and their influences on treatment efficiency of perchlorate and biological activity of PRB. We discussed the criteria for selection of appropriate electron donor to provide a flexible strategy of electron donor choice for the bioremediation of perchlorate-contaminated water.

Diflubenzuron (DFB) is a larvicide widely used to control Aedes aegypti populations as an alternative to organophosphates (OPs), with a specific mechanism of action for insects by inhibiting their chitin synthesis. However, DFB is used extensively in urban and rural environments, having the aquatic environment as the major receptor. Thus, the present study aimed to investigate the toxicity of DFB-based formulation and compare it with the toxicity of the OP temephos (TMP)-based formulation, a larvicide still used to control A. aegypti, on freshwater fishes Oreochromis niloticus and Hyphessobrycon eques. Organisms were submitted to acute (48 h) and prolonged (7 days) exposures, in the presence and absence of organic sediment, seeking interactions between chemical and sediment. Histopathological analyses were performed on O. niloticus gills and liver. According to 48-h median lethal concentration (LC₅₀), DFB- and TMP-based formulations were classified as harmful and toxic to fish, respectively, following the Globally Harmonized System of Classification (GHS). After prolonged exposure to sublethal concentrations, DFB-based formulation decreased H. eques body weight at concentrations 272-fold lower than its LC₅₀. Ultrastructural responses of O. niloticus indicated edemas and aneurisms on gills, and hepatocyte hypertrophy and vascular congestion of the liver. TMP-based formulation also induced pyknotic nuclei, which may lead to irreversible necrosis. The addition of organic sediment did not alter the larvicide toxicity, suggesting that larvicides remained available to the organisms. Altogether, these results suggest that as an insect-specific pesticide, DFB still induces mortality and tissue damage in fishes; thus, both larvicides pose risks to fishes.

The present study aims to assess the impact of a gold mine located in the southeastern part of Burkina Faso on local soil quality. This information is needed in order to determine any health hazards and potential remediation strategies as the mining site is expected to be turned over to the local community after the closure of the mine. For the purpose, total minor and trace elements analysis as well as a sequential extraction were performed and results were interpreted using different methodologies: enrichment factor (EF), geoaccumulation index (Igeo) computed using two separate background samples, and comparison to selected national standard. The soil analysis revealed a moderate to significant soil EF and Igeo with hotspots located closer to the ore processing plant and on the east side of the site, with a maximum arsenic concentration of 286.55 ± 12.50 mg/kg. Sequential extraction revealed, however, that less than 2% of the arsenic is found in the exchangeable part. Cobalt and zinc are more distributed in the different fractions than arsenic. Geogenic and anthropogenic contributions were revealed by the study. Graphical Abstract .

The calix[4]resorcinarene macrocycles are excellent oligomers for the design of amphiphilic derivatives; they can form self-assemblies and stable sensing networks. Owing to their favorable properties, they are the focus of many exploitations and studies ranging from biological controls to heavy metal ion sensing. In this perspective, two calix[4]resorcinarene derivatives, namely: C-dec-9-en-1-ylcalix[4]resorcinarene (ionophore I) and C-undecylcalix[4]resorcinarene (ionophore II) were used to form stable ultra-thin Langmuir monolayer films at the air/water interface; their interactions with different harmful metal cations (Cd²⁺, Pb²⁺, Hg²⁺, and Cu²⁺) were studied and highlighted via the pressure-area (Π-A) isotherms. The obtained results in the current investigation showed a dependence of both macrocycle interactions on the metal cation concentration in the subphase, confirming their complexation. In addition, the ionophore (I) exhibited high selectivity towards Pb²⁺ and Cu²⁺ cations, whereas the ionophore (II) showed tendency to bind with Cu²⁺ cations over others, approving the potential applicability of these macrocycles as ion selective chemical sensors.

The study on radon emanation and exhalation in soil is more and more important for environmental protection, and many influencing factors on radon emanation coefficient and exhalation in soil have been well documented. In order to evaluate the radon change and key influencing factors, this paper made an overall summary based on these studies. The main results show that the change laws of emanation coefficient with elevated temperature of radon can be divided into three types and they relate to the moisture state and content of soil. The normalized radon exhalation has a negative linear correlation with temperature, and the maximum emanation coefficient has a positive linear correlation with heating rate and specific surface. The pores with different size have different effects on the emanation coefficient of radon in the soil, e.g., the micro-pores increase emanation coefficient, and the mezzo-pores decrease emanation coefficient. Taken together, our results offered guiding significance for the evaluation of radon in soil and in air when soil state changes. Lastly, the existing problems and research directions were also given.

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.

Soybean peroxidase (SBP) has been employed for the treatment of aqueous solutions containing pentachlorophenol (PCP) in the presence of hydrogen peroxide at pH range 5–7. Reaction carried out with 1 mg/L of PCP, 4 mg/L of H₂O₂, and 1.3 × 10⁻⁹ M of SBP showed a fast initial elimination of PCP (ca. 30% in 20 min), but the reaction does not go beyond the removal of 50% of the initial concentration of PCP. Modification in SBP and PCP amounts did not change the reaction profile and higher amounts of H₂O₂ were detrimental for the reaction. Addition of Fe(II) to the system resulted in an acceleration of the process to reach nearly complete PCP removal at pH 5 or 6; this is more probably due to a synergetic effect of the enzymatic process and Fenton reaction. However, experiments developed in tap water resulted in a lower PCP elimination, but this inconvenience can be partly overcome by leaving the tap water overnight in an open vessel before reaction.