Mercury (Hg) contamination is an issue of concern in the Amazon region due to potential health effects associated with Hg exposure in artisanal gold mining areas. The study presents a human health risk assessment associated with Hg vapor inhalation and MeHg-contaminated fish ingestion, as well as Hg determination in urine, blood, and hair, of human populations (about 325 miners and 321 non-miners) from two gold mining areas in the Brazilian Amazon (São Chico and Creporizinho, Pará State). In São Chico and Creporizinho, 73 fish specimens of 13 freshwater species, and 161 specimens of 11 species, were collected for total Hg determination, respectively. The hazard quotient (HQ) is a risk indicator which defines the ratio of the exposure level and the toxicological reference dose and was applied to determine the threat of MeHg exposure. The mean Hg concentrations in fish from São Chico and Creporizinho were 0.83 ± 0.43 and 0.36 ± 0.33 μg/g, respectively. More than 60 and 22 % of fish collected in São Chico and Creporizinho, respectively, were above the Hg limit (0.5 μg/g) recommended by WHO for human consumption. For all sampling sites, HQ resulted from 1.5 to 28.5, except for the reference area. In Creporizinho, the values of HQ are close to 2 for most sites, whereas in São Chico, there is a hot spot of MeHg contamination in fish (A2—São Chico Reservoir) with the highest risk level (HQ = 28) associated with its human consumption. Mean Hg concentrations in urine, blood, and hair samples indicated that the miners group (in São Chico: urine = 17.37 μg/L; blood = 27.74 μg/L; hair = 4.50 μg/g and in Creporizinho: urine = 13.75 μg/L; blood = 25.23 μg/L; hair: 4.58 μg/g) was more exposed to mercury compared to non-miners (in São Chico: urine = 5.73 μg/L; blood = 16.50 μg/L; hair = 3.16 μg/g and in Creporizinho: urine = 3.91 μg/L; blood = 21.04 μg/L, hair = 1.88 μg/g). These high Hg levels (found not only in miners but also in non-miners who live near the mining areas) are likely to be related to a potential hazard due to exposure to both Hg vapor by inhalation and to MeHg-contaminated fish ingestion.

Extensive use of recalcitrant azo dyes in textile and paper industries poses a direct threat to the environment due to the carcinogenicity of their degradation products. The aim of this study was to investigate the efficiency of Curvularia clavata NZ2 in decolorization of azo dyes. The ability of the fungus to decolorize azo dyes can be evaluated as an important outcome as existing effluent treatment is unable to remove the dyes effectively. C. clavata has the ability to decolorize Reactive Black 5 (RB5), Acid Orange 7 (AO7), and Congo Red azo dyes, utilizing these as sole sources of carbon and nitrogen. Ultraviolet–visible (UV–vis) spectroscopy and Fourier infrared spectroscopy (FTIR) analysis of the extracted RB5’s metabolites along with desorption tests confirmed that the decolorization process occurred due to degradation and not merely by adsorption. Enzyme activities of extracellular enzymes such as carboxymethylcellulase (CMCase), xylanase, laccase, and manganese peroxidase (MnP) were also detected during the decolorization process. Toxicity expressed as inhibition of germination was reduced significantly in fungal-treated azo dye solution when compared with the control. The cultivation of C. clavata under sequential batch system also recorded a decolorization efficiency of above 90 %. The crude enzyme secreted by C. clavata also showed excellent ability to decolorize RB5 solutions with concentrations of 100 ppm (88–92 %) and 1000 ppm (70–77 %) without redox mediator. This proved that extracellular enzymes produced by C. clavata played a major role in decolorization of RB5.

Nafion 117 membrane (N117), an important polymer electrolyte membrane (PEM), has been widely applied in numerous chemical technologies. Its increasing production and utilization will inevitably lead to the problem of waste disposal, with incineration as an important method. However, toxicity data of its combustion products on aquatic organisms have been seldom reported. The present study was therefore conducted to investigate the antioxidant response and Na⁺, K⁺-ATPase activity in liver of Carassius auratus exposed to different combustion products of N117 for 5, 15, and 30 days. The concentrations of fluorine ion (F⁻) in the aquaria among the exposure durations were analyzed using the ion chromatography system. The results showed that these treatments have the capability to induce oxidative stress and suppress Na⁺, K⁺-ATPase activity, as indicated by some significant alterations on these measured toxicity end-points in fish liver. According to the integrated biomarker response (IBR) index, the toxicity intensity of these experimental treatments was tentatively ranked. Taken together, these observations provided some preliminary data on the potential toxicity of the combustion products of N117 on aquatic organisms and could fill the information gaps in the toxicity database of the current-use PEM.

The present study investigated the optimization of arsenic adsorption onto natural clinoptilolite (NC-Na). Response surface methodology in combination with Box–Behnken design was used to optimize the parameters of the adsorption process. Solution pH, temperature, and initial arsenic concentration were chosen as the main process variables, and the amount of arsenic adsorbed was selected as the investigated response. The analysis of variance results of the response surface model for arsenate (As(V)) adsorption on NC-Na showed that the effects and the interactions of pH and temperature were highly significant according to the p values (p < 0.05). The optimum conditions were found to be the solution pH of 5.0, temperature of 45 °C, and initial concentration of 7.8 mg L⁻¹. The response surfaces derived from the models revealed that solution pH and temperature showed the greatest effect on the As(V) adsorption capacity of natural clinoptilolite.

The process of phosphorus (P) transformation in particulate matter during sediment resuspension and sedimentation was studied. The P-binding forms in resuspended particles (RP) and settled particles (SP) were analyzed by sequential fractionation (modified Psenner method) and an extended extraction with ammonium oxalate. Water quality data and P fractions were used to estimate P release and uptake by the resuspended and settling sediment particles. Results of 8-h resuspension experiments showed increases of dissolved oxygen, pH, total phosphorus, and particulate phosphorus in overlying water, but no change in soluble reactive phosphorus (SRP). P fractions extracted with common sequential fractionation showed that the increase of total P in RP was mainly due to increases of redox-sensitive bound P BD (BD-SRP) and P bound to Al and Fe oxides (NaOH-SRP) (36–52 % and 30–36 % of total increased P, respectively). Comparisons between two sequential fractionations indicated that inorganic P extracted with ammonium oxalate consisted of P bound to amorphous Fe/Al oxy-hydroxides and partially of carbonate-bound P (HCl-SRP) and that increased P in RP was mainly caused by increases in P bound to amorphous oxides. It is concluded that the formation of amorphous oxides and subsequent adsorption of P lead to the increase of P in RP. However, P adsorbed by amorphous oxy-hydroxides in RP is unstable and may be released under sedimentation conditions. Meanwhile, increases in HCl-SRP, refractory P, and crystalline Fe-P were found in SP compared with RP. NaOH-SRP in SP increased gradually under sedimentation conditions. It is suggested that, during sedimentation, mobile P can be transformed to non-mobile P forms that provide long-term P retention. The findings contribute to the understanding of P cycling in particulate matter during sediment resuspension and sedimentation.

The present study is aimed to explore the relationship between coal consumption, industrial production, and CO₂emissions in China and India for the period of 1971–2011. The structural break unit root test and cointegrating approach have been applied. The direction of causal relationship between the variables is investigated by applying the VECM Granger causality test. Our results validate the presence of cointegration among the series in both countries. Our results also validate the existence of inverted U-shaped curve between industrial production and CO₂emissions for India, but for China, it is a U-shaped relationship. Coal consumption adds in CO₂emissions. The causality analysis reveals that industrial production and coal consumption Granger cause CO₂emissions in India. In the case of China, the feedback effect exists between coal consumption and CO₂emissions. Due to the importance of coal in China and India, any reduction in coal consumption will negatively affect their industrial value added as well as economic growth.

The Patagonian coast is characterized by the existence of pristine ecosystems which may be particularly sensitive to oil contamination. In this study, a simulated oil spill at acute and chronic input levels was carried out to assess the effects of contamination on the macrobenthic community structure and the bioturbation activity of sediments sampled in Caleta Valdés creek. Superficial sediments were either noncontaminated or contaminated by Escalante crude oil and incubated in the laboratory for 30 days. Oil contamination induced adverse effects on macrobenthic community at both concentrations with, for the highest concentration, a marked decrease of approximately 40 and 55 % of density and specific richness, respectively. Besides the disappearance of sensitive species, some other species like Oligochaeta sp. 1, Paranebalia sp., and Ostracoda sp. 2 species have a higher resistance to oil contamination. Sediment reworking activity was also affected by oil addition. At the highest level of contamination, nearly no activity was observed due to the high mortality of macroorganisms. The results strongly suggest that an oil spill in this protected marine area with no previous history of contamination would have a deep impact on the non-adapted macrobenthic community.

To offer scientific data support for remediation of Cd-contaminated paddy soils under reasonable water condition, pot experiment was conducted to study the effects of moisture management and amendments on Cd immobilization in a paddy soil. Application of biochar combined with organic fertilizer reduced the exchangeable Cd by 20.4, 15.7, and 13.0 % and brown rice Cd by 43.8, 35.5, and 42.1 % under continuous flooding, conventional irrigation, and wetting irrigation, respectively, compared to the controls. Under no amendments, the content of Fe(II) in root coating in the continuous flooding treatment was 2.3 and 3.6 times of that in the conventional and wetting irrigation treatments, but Cd in root coating in the continuous flooding treatment was only 82.6 and 73.8 % of that in the conventional and wetting irrigation treatments. Applying amendments increased the Fe(II) in root coating by 27.3, 59.1, and 65.0 % but reduced the Cd in root coating by 33.6, 26.5, and 25.1 % under continuous flooding, conventional irrigation, and wetting irrigation, respectively. The lower bioavailability of Cd in paddy soil and the competition for adsorption sites in root coating of rice plant between Cd²⁺and Fe²⁺reduced from bivalent ions jointly caused the lower brown rice Cd in amended soils.