Aeolian dust from hot spots in eastern China and Mongolia can be carried downwind to provinces in China, neighboring countries, the Pacific islands, and cities far beyond the source region. Although dust sources of huge extent have been identified in several countries, few effective countermeasures are available to combat dust emissions in arid regions. We analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) images (1 km spatial resolution) that captured dust emission and dispersion during 2000–2013 to determine dust sources in eastern China and Mongolia. MODIS level 1B data and the brightness temperature difference (BTD) algorithm provided efficient discrimination of dust in this study. The derived dust information, in conjunction with the MODIS land cover product (1 km spatial resolution) and high-resolution Landsat data (30 m spatial resolution; Landsat 8, Operational Land Imager sensor) were used to identify the locations and specific sources of dust. Dust emissions appear to be sporadic in time and space, controlled by both environmental factors and human activity, although past studies have indicated that many dust emissions are from consistently active hot spots. Analysis of MODIS data indicated that three subregions of the eastern China and Mongolia source region are the dominant sources of dust: Horqin Sandy Land, Otintag Sandy Land, and the southeastern Mongolian Gobi; each of these subregions contains dust emission hot spots. We identified the locations of consistent hot spots and verified that some individual dust emissions originated from those hot spots. Our data also indicated that hot spots in southeastern Mongolia have migrated northward since 2006. Our study showed that hot spots such as dry lakes, river beds, mines, and croplands contribute to dust emissions in the eastern China and Mongolia source region. Dust hot spots coincide with regions of expanding industry in Otintag Sandy Land and in some areas of the Mongolian Gobi and with agricultural areas in Horqin Sandy Land and in some parts of the Mongolian Gobi. In Horqin and Otintag sandy lands, dust sources are associated with ephemeral water bodies. Water conservation can be an important countermeasure for initial dust emissions in the Horqin Sandy Land. In the Otintag Sandy Land, attention should be paid to human activities, for example, minimizing the effects of mining disturbances, improving dust suppression in industrial areas, and controlling water use by industry. In Mongolia, protective farming techniques and water conservation in dust emitting basins, and dust suppression and water resource protection in mining zones, must be considered to combat dust emission. MODIS level 1B data can be used to locate dust hot spots and to identify future sources of dust entrainment. Dust hot spots identified from MODIS level 1B data provide small-scale information about dust emission that can be used to locate pollution hot spots, increase understanding of the global dust cycle, and improve dust modeling.

Carbamazepine (CBZ) is a representative of a group of compounds found in our rivers that have been classified as upcoming contaminants. Its pharmacological activity to treat mood and neurological disorders is based on its effects on ion channels, but effects on aquatic organisms have not yet been thoroughly investigated.In our initial analysis, we compared CBZ effects on two microalgae species differing in CBZ sensitivity: Parachlorella kessleri and Neochloris pseudoalveolaris. While we observed a stimulation in the growth rate in cultures of P. kessleri in the presence of 10 μg L⁻¹ CBZ, no effect on growth rates of N. pseudoalveolaris cultures could be documented at this concentration. Any higher tested CBZ concentration led to growth inhibition.To gain insight into these effects, biochemical and physiological parameters of these two microalgae species were measured in the presence of CBZ in a concentration-dependent manner.As the severe inhibition of growth rate correlated with a significant inhibition of most tested parameters in cultures of N. pseudoalveolaris, the primary reason for the adverse effect of CBZ on cultures of this microalgae species could not be identified. In cultures of N. pseudoalveolaris, experimental data indicate that inhibition of growth rate occurs when the microalgae are no longer able to compensate for adverse CBZ-induced ROS effects.Analysis of the CBZ response of cultures of P. kessleri showed a reduction of growth stimulatory effect if the CBZ concentration exceeds a threshold value. In general, cultures of P. kessleri show a great potential to withstand CBZ as an environmental pollutant.

The presence of multicomponent nonaqueous phase liquid (NAPL) source zones in the subsurface can significantly complicate remediation efforts, transport predictions, and the development of accurate risk assessments. A series of flow-cell experiments was conducted to investigate the effectiveness of two different enhanced-solubilization agents for the removal of a multicomponent dense nonaqueous phase liquid (DNAPL) source zone from homogeneous porous media. The source zone consisted of an equal 1:1:1 mole mixture of cis-1,2-dichloroethene (DCE), trichloroethene (TCE), and tetrachloroethene (PCE) with NAPL saturation (Sn) targeted between 8 and 14 %. Solutions (5 wt%) of hydroxypropyl-β-cyclodextrin (HPCD) and sodium dodecyl sulfate (SDS) were flushed through the flow-cell system until nearly complete contaminant removal was achieved. Analysis of elution curves indicate that SDS was approximately 10 times more efficient at removing all three components from the system compared to HPCD. Although enhancement factor magnitudes vary for each specific contaminant component and enhanced-solubilization agent, the lowest-solubility contaminant component (i.e., PCE) consistently experienced the greatest relative solubility enhancement during flushing. SDS was generally superior when evaluated on a recovery basis; however, HPCD outperformed SDS for all contaminant components when compared based on moles-contaminant to moles-reagent removal efficiency analysis. Contaminant mass flux reduction analysis showed that enhanced-solubilization flushing (HPCD and SDS) resulted in general inefficient contaminant removal behavior. Raoult’s Law could be used to successfully predict aqueous contaminant concentrations from the multicomponent DNAPL source zone, indicating that dissolution processes were relatively ideal during both HPCD and SDS enhanced-solubilization flushing. These findings suggest that multicomponent NAPL source dissolution and removal depend upon the flushing agent itself and of the solubility and properties of the individual components of the NAPL mixture. The selection of a particular enhanced-flushing agent should be evaluated carefully prior to remediation as the dissolution, removal, and mass flux behavior of each component can vary significantly.

A wide variety of application of nanoparticles (NPs) in recent years has raised their possible entrance into the environment so that can affect living components of ecosystems. There is no comparative study on the long-term effects of a wide range of concentrations of NPs, related bulk particles (BPs), and corresponding metal ions on different traits of the plants. The present study has investigated comparative effects of zinc oxide (ZnO) NPs, ZnO BPs, and zinc ions (Zn²⁺) on rapeseed (Brassica napus L.) after long-term exposure to a wide range of concentrations. The inhibitory effects of treatments on the growth of B. napus were in the order Zn²⁺ >> ZnO BPs > ZnO NPs. Results showed the significant changes in the antioxidant enzyme activities, total chlorophyll, soluble proteins, proline, and soluble sugars of the leaves in response to the treatments. However, total phenolic compounds were not affected significantly by any treatment. Overall, in the present study, the toxicity of ZnO NPs on B. napus was lower than those of Zn²⁺ or ZnO BPs. Results indicate that adverse effects of ZnO NPs or BPs on B. napus may be due in part to the toxic effects of Zn²⁺ ions dissolution, probably induced by root exudates, or due o the physical interaction of ZnO particles with roots and induction of structural and functional disorders.

Some microorganisms can produce biotensoactive when in contact with hydrocarbons, which favours micelle formation, allowing microbial cells to metabolise them effectively. In this study, we evaluated the capacity of nitrogen-fixing (NFB) and hydrocarbonoclastic bacterial strains to generate biotensoactive. The sampling site was in a flood plain of the Chico Zapote River, on the low basin of the Tonalá River in Tabasco, Mexico. Rhizospheres and soil contaminated by oil were collected, and the concentration of oil and botanic samples were determined for their taxonomic classification. The collected rhizosphere oil was seeded into Congo red cultures to obtain Azospirillum (NFB) bacteria. The NFB strain was placed in liquid mineral medium with oil as the only carbon source to identify the hydrocarbonoclastic strains. Biochemical and physiological evaluations determined that the species were Azospirillum brasilense and Azospirillum lipoferum. The strains were placed into Kim medium for generating a biosurfactant. The biosurfactant produced by A. brasilense showed an emulsion stability of 229 min, yield of 0.1375 g L⁻¹, emulsion capacity of 80 % and superficial tension of 38 mN m⁻¹, and while the biotensoactive produced by A. lipoferum had an emulsion stability of 260 min, yield of 0.22 g L⁻¹, emulsion capacity of 90 % and superficial tension of 35.5 mN m⁻¹.

Suspended sediments can decrease the apparent bio-concentration factor of organic pollutants through adsorption. However, whether this process also weakens the toxicity of organic pollutants to non-target aquatic organisms is not clear. Therefore, natural sediments were chosen as suspended sediment examples in this research applying atrazine as the target pollutant and Brachydanio rerio (more recently, Danio rerio (Zebrafish)) as the target organism to conduct acute toxicity experiments. The concentration of atrazine in aqueous solution was measured as a time series. Results show that without suspended sediments, the 96-h LC₅₀of atrazine to Brachydanio rerio is 29.06 mg/l at 95 % confidence interval (24.41 to 40.70 mg/l). For suspended sediments of 7500 and 15,000 mg/l, the LC₅₀(i.e., concentration resulting in 50 % mortality) equates to 30.74 and 39.51 mg/l, respectively, and the corresponding confidence intervals are between 27.17 and 40.91 mg/l and between 30.43 and 126.93 mg/l in that order. Probit analysis, which is a type of regression used to analyze binomial response variables, was applied using the Statistical Package for the Social Sciences. For the series of no suspended solids (SS), 7500 and 15,000 mg/l SS, the so-called no-observed-effective concentrations were 3, 9, and 15 mg/l, correspondingly. The uptake quantity and uptake rate of atrazine by B. rerio according to atrazine concentrations in the aqueous solution were computed. The research indicates that suspended sediments can decrease the absorbed rate of atrazine by B. rerio. Thus, suspended sediments weaken the acute toxicity of atrazine to B. rerio.

This study aimed to evaluate the removal of polychlorinated biphenyls, with a vermicomposting system, using the following as components: the earthworm Eisenia fetida, peat moss and rabbit excrement and a compound called decachlorobiphenyl, for a period of 91 days under non-sterile conditions. The results obtained were a removal of decachlorobiphenyl 79.6 % with an initial concentration of 100 mg L⁻¹, 89.7 % with 150 mg L⁻¹and 95.38 % with 200 mg L⁻¹; the earthworms bioaccumulated less than 5 mg L⁻¹in all concentrations of decachlorobiphenyl analysed without apparent toxic effect. Weight gain was observed in earthworms that assimilated contaminant during vermicomposting, as the number of cocoons produced in contrast to the control in which both the weight and the number of cocoons were lower. To our knowledge, this is the first study which suggests that vermicomposting may be a suitable mechanism for removal of decachlorobiphenyl with high recalcitrance from contaminated sediment or soils.

Cr interactions with TiO₂were systematically studied using batch and spectroscopic investigations. Sorption of chromium on TiO₂at pH 4.5 increases with increasing Cr concentration. The sorption of Cr(III) is in good agreement with Langmuir isotherm model, whereas that of Cr(VI) is better accounted for by the Freundlich model. At pH 7.0, however, the uptake of Cr(III) by TiO₂is over 95 %, while the extent of Cr(VI) sorption on TiO₂is much less than that of pH 4.5. These results are consistent with SEM observations showing that precipitates of Cr(III) are dominant under neutral pH. The sorption of Cr(VI) on TiO₂decreases with increasing pH. However, Cr(VI) sorption decreases with increasing ionic strength below pH 4.5 whereas the sorption increases with ionic strength above pH 4.5. These observations suggest that Cr(VI) sorption is sensitive to ionic strength, and Cr(VI) could form weakly bound adsorption complexes at the TiO₂–water interface. Phosphate competes with Cr(VI) for TiO₂surface sites during sorption processes, and Cr(VI) desorption accelerates and increases in the presence of phosphate. It is noted that the reduction of Cr(VI) is induced by sunlight on the TiO₂surface, but not detected in acidic solution throughout batch experiments at pH ≥ 4.5 for 24 h.

A novel alginate–montmorillonite biopolymer-clay composite bead formulation for water defluoridation was developed in this study. Montmorillonite was dispersed alginate solution, and the mixture was cross-linked in an aqueous solution of aluminum(III). The resulting cross-linked beads were characterized using FTIR, SEM, and mechanical measurements. In order to reveal the defluoridation capacity of the beads, batch adsorption experiments were carried out. Optimum conditions and effect of competing ions were investigated. Experimental data were modeled using several isothermal, kinetic, and thermodynamic models. Maximum Langmuir adsorption capacity was reached as 31.0 mg g⁻¹at 25 °C. It is also found that the adsorption is physical in nature and follows the Elovich kinetic model, and the fluoride removal efficiency is not affected by the presence of most competing anions. The results show that aluminum alginate–montmorillonite composite beads can be used as effective and natural sorbents for fluoride removal from water.

Many studies have been conducted regarding the degradation of PAHs. One of the technologies that has been widely used is bioremediation due to its relatively low cost and greater efficiency for those compounds with structural complexity. Biotechnology has been used in several countries for many years and consists in the use of microorganisms (bacteria and fungi) to transform contaminants into inert substances, which is a result of the microbial activity from biochemical processes. This study aimed to develop a bioremediation methodology for the pollutant benzo[a]pyrene (B[a]P), which belongs to the group of PAHs. The potential use of a microbial consortium with Pseudomonas aeruginosa, Candida albicans, Aspergillus flavus, and Fusarium sp. for bioremediation was assessed. To confirm the pollutant reduction, quantifications of the samples were performed via gas chromatography–mass spectrometry (GC-MS). The contamination was prepared with a soil previously contaminated with B[a]P at the concentration of 3.74 mg kg⁻¹. The microbial consortium was added (16 μL g⁻¹), and samples were incubated for 42 days in an oven at 35 °C. The microbial growth curves showed representative differences between the samples in the presence and absence of the pollutant, demonstrating the possibility of bioremediation process. The final quantification of soil showed a mean concentration of 1.29 mg kg⁻¹, showed that 65.51 ± 0.95 % of the pollutant was degraded, which is an important and representative performance.