Because of their adverse effects, such as their toxicity and carcinogenicity, volatile organic compounds (VOCs) are the most important and common pollutants produced by urbanization and industrial processes that contaminate air and water streams. VOCs, commonly originating from many industrial syntheses, and their derivatives, especially halogen, produce an unpleasant odor in the air when present in excess. All the issues related to VOCs make them a severe threat to whole ecosystems and environments as well as humans. Globally growing environmental awareness and knowledge have resulted in strict regulations to control VOC emissions into the air. It is necessary for each component of emitted VOCs to be controlled or removed from the air. NaZSM-5 and HZSM-5, having high ratios of SiO₂/Al₂O₃ (50), which are necessary for good adsorbents of organics, were prepared. Characterization of the prepared materials was done by XRD, SEM, FTIR, N₂ adsorption, NH₃-TPD, ²⁷Al-NMR, and TGA analysis. The adsorptive removal of VOCs from the air by Na-ZSM-5 and H-ZSM-5 was explored. These adsorption materials were tested with respect to the adsorption capacity, renewability, and selectivity for benzene, toluene, ethylbenzene, and xylene. The effects of the contact time, adsorbent dose, and initial concentration of pollutant on the adsorption process were also studied. Finally, the adsorption data were applied to Langmuir, Freundlich, and Temkin isotherms and two different kinetic models.

The aim of this study was to investigate the presence of heavy metals/metalloids (Pb, Cd, Hg, Cu, Fe, Zn, As) in the muscle tissue of fish from the Danube River (two locations: Zemun and Grocka). For the purpose of heavy metal determination in fish muscle, 120 samples of six different fish species, Prussian carp, barbel, bream, carp, pike perch, and catfish were collected. For determining heavy metals, we used microwave oven digestion and atomic absorption spectrometer methods. The highest average content of Pb (0.084 ± 0.004 mg kg⁻¹), Cd (0.082 ± 0.003 mg kg⁻¹), Hg (0.466 ± 0.006 mg kg⁻¹), and As (0.333 ± 0.007 mg kg⁻¹) was found in the muscle of carp (an omnivorous fish) from Grocka, while the highest average level of Fe (13.60 ± 0.03 mg kg⁻¹) was deposited in bream (also omnivorous) from Zemun. Also, the average Cu level (1.62 ± 0.13 mg kg⁻¹) was the highest in catfish muscle (a carnivorous fish) from Grocka, while the highest Zn content (11.16 ± 0.17 mg kg⁻¹) was determined in muscle of Prussian carp (an omnivorous fish) from Zemun. The highest content of heavy metals (Cu, Fe, and Zn, respectively) in muscle of the six different types of fish from both locations was symmetrically arranged by species (catfish, barbel, and Prussian carp, respectively). Concentrations of Pb, Hg, and As in the Danube River fish muscle were under the maximum residual levels prescribed by the European Union (EU) and the maximum allowed concentrations (MAC) for Serbia. On the other hand, in all fish muscle from both locations (Zemun and Grocka), higher concentrations of Cd than prescribed (MAC) were found, with the exception of bream and pike perch.

The reaeration coefficient (K ₐ) is an essential parameter to predict the dissolved-oxygen concentration in different aquatic ecosystems. The techniques applied to K ₐ estimates require considerable efforts, since measuring this coefficient is a laborious and expensive task. Thus, the use of predictive equations wherein K ₐ is found through hydraulic flow parameters is common. However, the available prediction equations lead to estimates often different from each other. A new predictive equation is addressed in the present study. The insertion of a dimensionless number resulting from the relation between the RMS (Root Mean Square) of the free-surface vertical velocity and the surface flow velocity is the great innovation of the study. The reaeration experiments and the surface vertical velocity mapping were performed in a circular hydraulic channel. The flow velocity varied from 0.25 to 0.64 m s⁻¹, and depth varied from 0.09 to 0.15 m. The new equation led to more accurate results than the equations based on traditional hydraulic parameters such as the Reynolds and Froude numbers, mainly when it comes to K ₐ values higher than 40 day⁻¹. The sensitivity analysis has shown that the new dimensionless number is the most sensitive parameter of the herein proposed predictive equation and that the influence from the Reynolds and Froude numbers on K ₐ weakens as turbulence gets more intense.

Dispersal of functional microorganisms is a rate-limiting process during in situ bioremediation of contaminated soil and groundwater. In this work, series of column experiments were conducted to investigate the retention and transport behaviors of Herbaspirillum chlorophenolicum FA1, a promising bacterial agent for bioremediation, in saturated porous media under conditions of different combinations of grain size, solution pH, solution ionic strength (IS), and humic acid (HA) concentration. Experimental data showed that the mobility of FA1 in saturated porous media was strongly dependent on the physicochemical conditions. The breakthrough curves (BTCs) indicated that the amounts of FA1 in the effluent increased with increasing in sand size, solution pH, and HA concentration, but decreased with increase of solution IS. The shape of retention profiles (RPs) was hyper-exponential. The amounts of retained bacteria in the media also varied with the experimental conditions with opposite trends to that of effluent. Both experimental BTCs and RPs were simulated by a mathematical model that accounted for deposition kinetics to better interpret the effects of physicochemical conditions on FA1 deposition dynamics. Findings from this study showed that fate and transport of the functional bacterium FA1 in porous media strongly relied on the environmental conditions. Both experimental and modeling results can provide guidelines for field application of functional bacteria for soil and groundwater remediation.

The effect of solids retention time (SRT) on volatile fatty acids (VFAs) accumulation and microbial community evolutions in enzymolysis-pretreated waste activated sludge (WAS) fermentation process was investigated. SRT played important roles on VFA accumulation efficiency and composition with a best performance of over 2200 mg COD/L at an SRT of 8 days. Volatile suspended solids (VSS)/total suspended solids (TSS) of fermentative sludge decreased obviously during the fermentation tests at various SRTs. Distribution spread index (DSI) of fermentative WAS augmented from 1.175 to 1.218 in accordance with SRT rising from 6 to 11 days. SRT changes led to microbial community (bacterial and archaeal) shifts clearly as well as the community diversity in the fermentation system. Bacterial community evenness tended to be more uneven at an SRT of 8 days compared to SRTs of 6 and 11 days, which indicated that high dominance of bacterial community could be formed at 8 days SRT with more VFA accumulation in WAS fermentation system. RDA inferred that microbial consortia could be driven by the preponderant individual VFA accumulation (acetate, propionate, and N-butyrate) with getting to a relative balance level by SRT optimization in the system.

Genetically modified agricultural products have been introduced to increase food supply by enhancing their resistance to pests and diseases, along with easily adapting to environmental conditions. Due to the modification of DNA, public objections are prevalent, including concerns on the impact on the ecosystem. In this research, adsorption and transport of Cry1Ab, a toxin exuded by the transgenic Bt maize in alumino-silica clays, were evaluated in laboratory columns under steady-state flow conditions. Since Cry1Ab fate and transport were very responsive to animal waste field applications, during which humic acids were released, Cry1Ab adsorption and transport in humic acid-coated alumino-silica clays were also investigated. Cry1Ab breakthrough curves were simulated using the convection-dispersion transport models. It was discovered that the humic acid coating increased Cry1Ab deposition during the transport. Based on analysis of the breakthrough curves, adsorption isotherms of Cry1Ab in alumino-silica clays were obtained and compared with those of batch experiments. The humic acid coating changed the bonding energy between Cry1Ab and the adsorption receptor sites on alumino-silica clay surfaces, thereby changing Cry1Ab partition between the aqueous phase and the solid phase.

The use of low-polarity organic solvents is widespread in cleanup/extraction processes in order to carry compounds of interest, remove interferences and separate phases, among other uses. A large number of studies have used delipidation to remove excess of lipids to analyse carbon stable isotopes in biological tissues for trophic and behavioural ecology investigations. In this context, the primary aim of this study is to assess the influence of one delipidation process on the results of total mercury (Hg) analyses and the possible use of delipidated samples from previous analyses, such as for stable isotopes, in Hg level determination. Samples of vegetation (angiosperm, lichens and mosses), invertebrates (krill and limpets), fish (marbled and black rockcod), bird liver and eggs (Antarctic, Gentoo and Adélie penguins, kelp gull, Antarctic tern, cape petrel and giant southern petrel) and pinniped tissues (Weddell seal, crabeater seal, southern elephant seal and Antarctic fur seal) were analysed for Hg before and after delipidation by cyclohexane. The difference between the two measurements ranged individually from −63 to 136% (in the moss Sanionia uncinata) and the averages ranged from −60 to 66% (in pinniped tissues). The proportion of organic Hg, which presents considerable lipophilicity, but also high affinity for sulfhydryl groups in proteins, might be responsible for such variability. Given the limitations of our study, we think it is safe to say that delipidated samples could not be used to infer total Hg values in non-delipidated ones.

Occurrence of halonitromethanes (HNMs) in drinking water has been a concern recently due to the potentially high human health risks of HNMs. Mechanisms of formation of HNMs during disinfection has remained controversial. The objective of this study was to investigate the effects of nitrite on the formation of trichloronitromethane (TCNM), a dominant HNM species occurring in chlorinated water. Polyhydroxy-phenols (hydroquinone, catechol, resorcinol, and phloroglucinol) and sugars (glucose, maltose, and lactose) were compared as surrogates/model compounds of common organic precursors of humic and non-humic substances in natural organic matter, respectively. The results showed that TCNM was not detectable after chlorinated sugars with the addition of nitrite. Upon chlorinating the polyhydroxy-phenols, TCNM formation varied greatly among different compounds, i.e., resorcinol > phloroglucinol > catechol >> hydroquinone. The results demonstrated that TCNM formation in the presence of nitrite was a function of aromaticity as well as the position and number of hydroxyl groups on the benzene rings of a compound, and the TCNM formation potential of humic substances was greater than that of non-humic substances. For catechol, resorcinol, and phloroglucinol, TCNM formation varied greatly with pH but generally remained stable with the increase of reaction time and temperature.

Biochars are adsorptive solids potentially of benefit to soil microbes by providing improved nutrient retention, a carbon substrate and contaminant adsorption. A 28-day incubation experiment gauged the interactive effects of biochar application and contaminants on the microbial biomass and respiration of a sandy loam soil. Soil was amended with 250 mg/kg phenol or p-nitrophenol (two toxic but nevertheless biodegradable organic contaminants) or 50 mg/kg cadmium or copper. Biochar application generally caused increased microbial respiration and biomass relative to non-amended controls. Of the heavy metal-amended soils, Cu effected significant reductions in microbial biomass carbon and basal respiration, which were improved with concurrent biochar amendment. The biochar’s functional groups are likely to have mitigated the metals’ negative effects via complexation and sorption, while the soil’s proportion of negative pH-dependent sites was increased by the pH rise induced by biochar application, allowing more cationic retention. Organic contaminant-spiked soils had higher microbial biomass-specific respiration without biochar amendment, indicating that surviving microbes utilised the compounds and necromass as substrates. Paranitrophenol proved to be particularly toxic without biochar application, causing marked reductions in the microbial quotient and biomass carbon. Remarkably, concurrent biochar and pNP application led to hugely increased microbial biomass carbon and nitrogen, significantly higher than those in contaminant-free replicates. It is likely this arose from biochar sorbing the contaminant and allowing its microbial utilisation as a carbon and nitrogen source, stimulating growth. Biochar application is a highly promising strategy for reducing the soil microbial toxicity of heavy metals and aromatic organic contaminants, particularly p-nitrophenol.

An effective reagent for mercury desorption from contaminated soil is a key condition for mercury remediation. Effects of time, pH, temperature on mercury desorption using sodium sulfite were studied with a series of batch experiments. Results showed that desorption rate of mercury increased rapidly in the stage of 0 to 1 h, after that, a much slower stage appeared. Desorption rate reached 92.05% with 0.7 mol/L sodium sulfite at 25°C in 24 h. Moreover, potential value increased rapidly from −162 to –31 mV in desorption of 1 h. It indicates that desorption process was a process of Hg(II) turning into Hg(I). A higher pH (10.5) or temperature (35°C) was helpful to increase mercury desorption rate. Furthermore, small fold and curves appeared in the surface of soil particles presented by scanning electron microscopy (SEM) show that soil particles may be destroyed in desorption process using sodium sulfite. The desorption of Hg from contaminated soil was accomplished within a reductive solution provided by sodium sulfite.