The present and future air contamination by mercury is and will continue to be a serious risk for human health. This publication presents a review of the literature dealing with the issues related to air contamination by mercury and its transformations as well as its natural and anthropogenic emissions. The assessment of mercury emissions into the air poses serious methodological problems. It is particularly difficult to distinguish between natural and anthropogenic emissions and re-emissions from lands and oceans, including past emissions. At present, the largest emission sources include fuel combustion, mainly that of coal, and “artisanal and small-scale gold mining” (ASGM). The distinctly highest emissions can be found in South and South-East Asia, accounting for 45% of the global emissions. The emissions of natural origin and re-emissions are estimated at 45–66% of the global emissions, with the largest part of emissions originating in the oceans. Forecasts on the future emission levels are not unambiguous; however, most forecasts do not provide for reductions in emissions. Ninety-five percent of mercury occurring in the air is Hg⁰—GEM, and its residence time in the air is estimated at 6 to 18 months. The residence times of its Hgᴵᴵ—GOM and that in Hgₚ—TPM are estimated at hours and days. The highest mercury concentrations in the air can be found in the areas of mercury mines and those of ASGM. Since 1980 when it reached its maximum, the global background mercury concentration in the air has remained at a relatively constant level.

Among the measures used to manage mosquito populations and prevent human diseases, the application of pesticides is the global strategy mostly employed. To investigate the lethal and sublethal effects of insecticides used to control mosquitoes on amphibians (Rhinella arenarum, Rhinella fernandezae, and Physalaemus albonotatus), tadpoles were exposed to commercial formulations of temephos (Abate®), Bacillus thuringiensis var. israelensis (Introban®), and permethrin (Depe®). Their acute toxicity in terms of median lethal concentration (LC₅₀) and no- (NOEC) and lowest-observed-effect concentrations (LOEC) was evaluated. To assess the sublethal effects on behavioral endpoints, tadpoles were exposed to the NOEC-24-h value of each insecticide. After that, tadpoles were recorded and video-streaming data were processed by Smart® software. Based on LC₅₀, permethrin was the most toxic insecticide, followed by temephos and B. thuringiensis var. israelensis. Also, intraspecific and interspecific susceptibilities of tadpoles to insecticides were observed. Regarding behavior, the exposure of R. arenarum to the three insecticides had a significant effect on all behavioral endpoints. Two of the three swimming parameters evaluated for R. fernandezae were affected by permethrin, and in the end, only one behavioral pattern was altered in P. albonotatus after exposure to temephos. These results showed that tadpoles’ species were affected differently depending on the chemical properties of the pesticide and on a dose-response effect of the insecticides. Overall, our study suggests that further research is needed to quantify the potential damage of pyrethroid insecticides used for mosquito control on non-target aquatic organisms, mainly due to etho-toxic effects.

The present study was carried out in order to investigate the removal of soluble Mn²⁺ from an aqueous solution using Bacillus cereus. A manganese aqueous solution at 50 mg L⁻¹ was treated, and the product was less than 1 mg L⁻¹ of residual concentration, which complied with environmental regulations. Before the optimization, B. cereus was able to remove Mn²⁺ ions from an aqueous solution; however, the residual content was around 2.5 mg L⁻¹. Screening experiments aiming at defining the effects of the growth medium composition indicated that both casamino acid-peptone and yeast extract contributed to manganese removal. These experiments also showed the interaction between these two components of the culture media, nevertheless the use of glucose did not prove significant. Considering these observations, the Doehlert design was used to generate a response surface. The model was significant with the p value lower than 0.05 and the lack-of-fit not significant (p > 0.05). The optimized composition of the growth medium was defined as 0.5 g L⁻¹ of casamino acid-peptone and 0.25 g L⁻¹ of yeast extract, whereas glucose could be removed from the original growth medium. When the optimized condition of the growth medium was used, the time required for manganese removal was reduced from 21 to 8 days. After optimization, B. cereus was capable of producing high manganese removal, reducing the residual concentration to levels below 1.0 mg L⁻¹.

This study analysed the effectiveness of innovative (basalt meal, brown algae extract) and conventional (barley straw) substances which hypothetically alleviate the inhibiting effect of Cd²⁺ on biochemical properties of soil, with particular regard to the activity of arylsulfatase. An analysis of their potential was carried out based on the activity of arylsulfatase and the number of Pseudomonas sp. determined on the 25th and 50th days of the study. Cd²⁺ was applied in the following doses: 0, 4, 40, 80, 120, 160, 200 mg Cd²⁺ kg⁻¹ of DM soil, in the form of CdCl₂·2.5H₂O. A complex formulation of the issue was obtained from the presentation of biochemical properties using the RS (resistance of soil) index. Cadmium caused permanent adverse effects in the soil environment, inhibiting the activity of arylsulfatase and the yield of spring barley. The consequences of stress connected with increasing Cd²⁺ pollution were intensified by an elongation of the accumulation time of the tested metal in the soil. Chances for regeneration of the soil may be sought, most of all, with the application of straw and, to a lesser degree, with basalt meal. Brown algae did not meet the expectations for its potential. An increase in the studied parameters also resulted from sowing the soil with spring barley.

Agricultural intensification has led to the use of high inputs of chemical fertilizers into rice-cultivated lands, and nitrogen and heavy metals in runoff loss from land were a major environmental problem. It is important to mitigate nitrogen and heavy metal pollution for the water body. The nitrogen and heavy metal transformation in the rice field surface water was studied by applied combined organic and inorganic nitrogen fertilizer plus the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in the sandy loam paddy soil and blue clayey paddy soil. The results showed that, the application of DMPP in the rice field in organic and inorganic fertilizer combined application models decreased the heavy metal average concentration of total Cu, Zn, and Cd by 22.1 to 30.2, 33.1 to 36.9, and 10.9 to 17.5% in surface water, respectively. Furthermore, in the sandy loam paddy soil and blue clayey paddy soil, the nitrate, nitrite, and total inorganic nitrogen concentrations decreased by 44.4 and 59.6, 90.3 and 88.6, and 14.2 and 25.4% in the rice field surface water with the DMPP addition, in the organic and inorganic fertilizer combined application models in the rice field, respectively. DMPP could be used as an effective nitrification inhibitor to decline the potential nitrogen and heavy metals runoff loss in the combined application models of organic and inorganic fertilizers in some rice fields, minimizing the nitrogen and heavy metal transformation risk from agricultural fields to the water body and being beneficial for protecting the ecological environment.

The polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) are persistent environmental pollutants. Recently, there have been an increasing demand to assess different biomarkers as early alarming indicators of environmental pollution. This study is the first to investigate the effects of PCDD/Fs on acetylcholinesterase (AChE) activity and histopathology of the body wall (epidermis, circular, and longitudinal muscles) of earthworm Eisenia andrei (Oligochaeta, Lumbricidae) using acute filter paper toxicity test. It is also exploring the selected biomarkers as a potential tool for evaluating soil quality. Earthworms were exposed to 0, 0.5, 1.0, and 1.5 ng/cm² PCDD/Fs. The treated worms expressed progressive abnormal morphological signs with incrementing doses of dioxins, such as coiling, curling, and body swelling. At the highest dose, some worms demonstrated skin discoloration, loss of body segmentation, and body part detachment. The AChE activity was significantly decreased (p < 0.001) in all treated animals compared to control. The mixture induced circular muscle hyperplasia at 0.5 ng/cm². However, the mixture at 1.5 ng/cm² caused epidermal atrophy with cell pyknosis and necrosis in all layers of the body wall. Image analysis revealed significant reduction in the thickness of the epidermis (p < 0.001) at all doses with relative to control. Herein, we report that 48 h of acute exposure of E. andrei to dioxins/furans induced morphological changes, reduced the activity of AChE, and induced histopathological alterations. The outcomes can be utilized as endpoints that could be added to earthworm’s standardized short tests for ecotoxicity studies.

The potential application of commercial coffee as a source of electron donors for detoxifying hexavalent chromium [Cr(VI)]-contaminated water was investigated. Various amounts of coffee were reacted with 50 mg/L of artificially prepared Cr(VI)-contaminated water, and the Cr(VI) concentration was monitored as a function of the reaction time using the diphenylcarbazide colorimetric method with an Aquamate 8000 UV-Vis spectrophotometer at a 540-nm wavelength. When the ratio of the coffee mass applied to the volume of Cr(VI) solution was 75 g/L, more than 80% of the initial Cr(VI) disappeared within 5 min of reaction time, and the Cr(VI) concentration became lower than the detection limit of 1 mg/L within 20 min. More Cr(VI) disappeared as more coffee was introduced. In general, smaller particles of coffee were more effective at Cr(VI) reduction, but the advantage that particle size conferred disappeared once the coffee particle size was smaller than 125 μm. As a result, the reduction of the Cr(VI) in the solution was not considered to result from the surface catalytic reduction but by the electron transfer from the electron donors released from the applied coffee.

The study investigated wastewater treatment in an aerobic reactor with activated sludge exposed to static magnetic field (SMF) with mean induction of 8.1 mT. The efficiency of chemical oxygen demand removal was about 90% in a control reactor and an SMF-exposed reactor. Although the nitrification efficiency was higher than 95% in both reactors, the activity of ammonia-oxidizing bacteria was higher in the SMF-exposed reactor. This resulted in shortening of nitrification time to 4 h compared to 8 h in the control reactor. Higher number of ammonia-oxidizing bacteria in the SMF-exposed reactor might result from increased oxygen penetration into the liquid exposed to SMF, which favored growth of these bacteria. The results indicate that SMF enhanced nitrification, the most sensitive process from the biological nitrogen transformations. SMF influenced the overall biomass content that was 14% higher in the SMF-exposed reactor than in the control reactor.

The gas absorption/chemical reaction (GACR) method developed in chemical engineering to measure gas–fluid interface in reactor systems is adapted for natural porous geologic media. Several series of column experiments were conducted using model glass beads and a natural sand to determine optimal operational conditions for measuring air–water interfacial area with the adapted method. The impacts of operational variables were investigated, including liquid and gas volumetric flow rates, solution concentration, and temperature. The results show that the magnitude of the measured air–water interfacial area is dependent upon all of these variables to greater or lesser degrees. Larger fluid flow rates promote distribution and mixing of the fluids, enhancing absorption and reaction. Increasing the concentration of NaOH in solution reduced the relative utilization of NaOH, promoting pseudo-first-order reaction conditions. The results elucidate the optimal operational conditions for application of the method to geomedia systems.

The cadmium (Cd) contamination in the aquatic environment has attracted more and more attention due to its toxicity characteristics, e.g., accumulation in the environment, non-degradability, and the potential threat to the ecosystem. In this research, in order to illustrate the potential threat of heavy metal Cd to aquatic organisms, the online swimming behavior and the continuous acetylcholinesterase (AChE) activity in the gill of Zebrafish (Danio rerio) in 48 h exposure of cadmium chloride (CdCl₂) (4.26 mg/L (0.1 TU, toxic unit), 42.6 mg/L (1.0 TU), and 85.2 mg/L (2.0 TU)) are investigated. The behavior responses of D. rerio based on behavior strength (BS) have obvious dose-effect relationship, and lower BS values could be observed in the dark period at 13–21 h and 37–45 h in all treatments. The circadian rhythm could be observed even in all treatments (0.1, 1.0, and 2.0 TU), and the rhythm was disrupted with 1.0 TU at the end of the experiment whereas the lower (0.1 TU) and higher (2.0 TU) levels showed clear rhythms. These results suggested that the online BS values could illustrate the toxicity of CdCl₂ directly. The AChE activity in the gill is strongly inhibited by CdCl₂ based on the continuous sample results during 48 h exposure. The cross-correlation results using DCCA show a high correlation (r > 0.5) with extreme significance (p < 0.01), which suggest that the exposure in CdCl₂ can affect the AChE activity of D. rerio, and then damage the transduction signal due to neurotoxicity, which may induce decrease of swimming behavior, loss of coordination, and other kinds of behavior changes.