Predicting impacts of oil spills on the environment requires a better understanding of the effects on aquatic organisms, both for single hydrocarbons and for their interactions. In this study, the individual and combined effects of the petroleum hydrocarbons phenanthrene and dibenzothiophene (DBT) were assessed on the reproductive behavior of the freshwater amphipod Hyalella azteca. Following a 24-h exposure to single polycyclic aromatic hydrocarbons (PAHs), or an equimolar mixture of phenanthrene–dibenzothiophene (Phen–DBT), mate-guarding behavior was assessed. This consisted of an assessment of the incidence of mate guarding right at the end of the exposure period and quantification of the “time taken to initiate mate guarding” (TIMG) and “proportion of time spent mate guarding” (PTMG) during a subsequent 10-min observation period in clean water. Both Phen and DBT reduced the incidence of mate guarding at the end of the exposure. TIMG and PTMG during the observation period were not affected by the PAHs other than indirectly by their effect on mate guarding status at the end of the exposure. The interaction between Phen and DBT varied among the mate guarding measures. For mate guarding status at the end of the exposure period and for TIMG, the interaction did not deviate statistically from an additive effect. For PTMG, the overall interaction was a synergistic one. This study’s findings point out that assessments of hydrocarbon toxicity need to take into account that subtle reproductive behaviors (that may be important for population persistence) may be negatively affected. The results also show that the general assumption of additive effects among PAHs may be an oversimplification.

Heavy metal contamination causes significant environmental problems around the world and poses a threat to human health. Poplar hybrids present features for potential uses in phytoremediation systems in areas with heavy metal contamination. The purpose of this study was to assess the copper (Cu) accumulation level in five poplar inter-species hybrids [(Populus trichocarpa × Populus deltoides) × P. deltoides; P. deltoides × Populus nigra; P. trichocarpa × Populus maximowiczii; P. trichocarpa × P. nigra; and (P. trichocarpa × P. deltoides) × (P. trichocarpa × P. deltoides)] grown in a hydroponic system. The treatments entailed the application of low and high doses of Cu of 8.0 and 16.0 μM, respectively. Cu accumulation was observed in roots, stems, and leaves, which was determined using flame atomic absorption spectroscopy, prior acid digestion of each sample. The methodology was validated according to certified reference material (Cypress BIMEP 432). Significant differences in Cu accumulation were found among genotypes for both roots and leaves, but not for stems. In roots, the genotype P. deltoides × P. nigra had a Cu accumulation level of 169.8% higher than the average accumulation found in the other genotypes. The (P. trichocarpa × P. deltoides) × P. deltoides hybrid showed the least Cu accumulation in leaves. The results of this study can potentially be used for proper crossovers and hybrids selection within the genus Populus for phytoremediation of Cu contaminated land.

A novel quaternary nanocomposites consisting of Ag/AgCl decorated TiO₂ introduced on graphene oxide (GO) sheets with high loading of GO (50 wt.%) were prepared for photocatalytic application. The composite powders were synthesized by a facile sol–gel method utilizing polyvinylpyrrolidone (PVP) as a reducing agent to obtain Ag particles and a modified Hummers’ method to acquire GO sheets. The influence of reducing agent concentration and type of TiO₂ was investigated. The adsorption properties of the GO/TiO₂/Ag/AgCl nanocomposites were examined, and photocatalytic activity was investigated under UV light applying methylene blue (MB) as a model pollutant. The composites displayed great adsorption capability up to 112.6 mgg⁻¹ due to GO. It is shown that the GO/TiO₂/Ag/AgCl samples prepared by Degussa P25 TiO₂ and with a reduced amount of PVP have the best photocatalytic activity, reaching up to 55% decolorization of methylene blue under UV light. The photocatalytic activity is enhanced by approximately 80% with the addition of GO to the quaternary GO/TiO₂/Ag/AgCl composites.

Sugarcane bagasse soot is an agro-industrial residue rich in carbon that can be transformed into value-added materials, such as activated carbons. Therefore, this work aimed at producing activated carbon from sugarcane bagasse soot, using CO₂ at 800, 850, and 900 °C, and investigating its efficiency to adsorb methylene blue as model contaminant. The results showed that the surface area and pore volume increased in the obtained carbons, with high specific areas (up to 829 m²/g), and the isotherms of the N₂ adsorption describe mesoporous materials. The morphology of the prepared activated carbons showed that sugarcane bagasse soot and the activated carbons kept the fibrous structure of sugarcane bagasse, but after activation, they have cavities that resemble a honeycomb. Adsorption studies with methylene blue dye showed that the activation process resulted in adsorption capacities up to 11 times higher than sugarcane bagasse soot, which is comparable with commercial activated carbon. Dye adsorption kinetics could be described by a pseudo-second-order dependency in the studied materials, and the adsorption isotherms were better fitted by the Langmuir model. It is emphasized that cost-effective materials that are similar to commercial activated carbon were obtained.

Balancing the nitrogen derived from sewage effluent and fertilizers is essential for efficiently utilizing the nitrogen and minimizing the environmental degradations when applying sewage effluent. Pot experiments of maize (Zea mays L.) under drip irrigation were performed using ¹⁵N labeled urea to quantify the nitrogen balances of sewage effluent and fertilizers. Field experiments were conducted to confirm the findings of pot experiments. Four nitrogen rates ranging from 0 to 2.64 g/pot (0–210 kg/ha equivalently) for pot experiments and from 0 to 180 kg/ha for field experiments were established applying either secondary sewage effluent (SW) or groundwater (GW). Both pot and field experiments revealed that SW irrigation boosted nitrogen uptake and yield of maize compared to GW irrigation. However, the sewage-derived effects decreased with increasing nitrogen rates. SW irrigation could facilitate the uptake of ¹⁵N labeled urea relative to GW irrigation. Nonetheless, the nitrogen containing in effluent possibly had lower uptake effectiveness than the fertilizer urea for maize, suggesting greater potential for nitrogen losses resulting from effluent nitrogen compared to urea nitrogen. The percentage utilization of effluent nitrogen declined from 43 to 34% in 2014 and 48 to 32% in 2015 as nitrogen rates increased from 0 to 2.64 g/pot. Besides, the percentages utilization of total nitrogen (including effluent and fertilizers) under SW irrigation increased from 43 to 55% in 2014 and from 48 to 55% in 2015 when the rates increased from 0 to 1.76 g/pot, and subsequently decreased to 48% in 2014 and 44% in 2015 at the rate of 2.64 g/pot. This result was strengthened by the pattern of nitrogen recovery efficiency observed in the field experiments. Overall results of pot and field experiments recommended an optimal rate of 120 kg/ha for maize under drip irrigation applying SW to maximize nitrogen use efficiency and achieve an acceptably high yield.

Batch adsorption studies for cadmium (Cd), copper (Cu) and chromium (Cr) onto an agricultural soil impacted by mining activities were conducted in single- and multi-component systems. The effect of initial concentration, pH and competing ions (Fe³⁺, Ca²⁺, Co²⁺, Mg²⁺, K⁺, Ni²⁺ and Zn²⁺) on adsorption was studied. The soil exhibited high adsorption capacities for the elements at all initial concentrations with the adsorption process better described by the Freundlich isotherm. Adsorption was found to proceed via an ion exchange mechanism. The pseudo second-order kinetic model described the adsorption of the elements (R ² > 0.999), indicating a chemisorption process. The adsorption of Cd increased with pH in both systems while that for Cu decreased. The adsorption of Cr decreased with pH in the single-component system, but increased in the multi-component system. The adsorption of Cd was affected more by competing ions while Cu and Cr were not significantly affected (p > 0.05). Elemental speciation under varying conditions was studied using the PHREEQC geochemical modelling code. The observed high capacity of the soil for the elements pointed to the soil’s potential as a repository, a feature that would change depending on the speciation of the elements and soil conditions.

Melamine, which has three free amino groups and three aromatic nitrogen atoms in its molecule, can be potentially used as an adsorbent for metal ions. Factors associated with adsorption efficiency of vanadium by melamine were systematically investigated, including initial pH value of solution, temperature, contact time, and dosage of melamine. The optimal operation conditions for adsorption performance of vanadium with melamine were obtained. The adsorption efficiency was over 99.97% at the initial pH value of 1.18, molar ratio of n (melamine)/n (vanadium) = 1.0 for 60 min. The kinetic data for the adsorption followed well the pseudo second-order kinetic model.

This study assessed the level of potentially toxic trace metals (PTMs), seasonal variations, and their possible sources from the surface water and lake-bed sediment of Panchpokhari lake series, an alpine and glacial lake at 4160 m a.s.l. in Central Nepal. The lake series have five lakes, with Lake-1 larger than others. So, Lake-1 was investigated thoroughly during pre-monsoon and post-monsoon seasons. Sediment core was collected from the deepest basin of the Lake-1 during pre-monsoon. Most of the PTM concentrations were higher in the pre-monsoon season; however, Sc, Cr, Cu, Zn, As, and Ag were higher in the post-monsoon. This is an indication that the lake has been impacted either by natural or long-range transported atmospheric pollutants. Ti, Sb, and Ag had extremely high enrichment factor (EF) in waters, whereas Cd, Zn, and As had high EF in sediments indicating that these metals originated from anthropogenic sources. Furthermore, PTM concentrations in the sediment were in the increasing order of Hg < Cd < Ag < Mo < Sb < Sn < As < U < Sc < Co < Cs < Cu < Pb < Ni < Cr < V < Zn < Rb < Mn < Ti < Fe and showed that the upper layer (top 10 cm) of lake sediment has been receiving a higher load of PTMs in the recent period. he observed EF values also suggested that major sources of PTMs in the sediment were from crustal origin except for a few metals (Ti, V, Sb, and Ag) which were enriched anthropogenically due to long-range transport of atmospheric pollutants, deposited at the higher elevations. Nevertheless, the level of pollution in sediments was low as indicated both by EF and geo-accumulation index.

Adsorption of hexavalent chromium (Cr(VI)) using pomelo peel activated biochar (PPAB) as a adsorbent was investigated. The characterization of the adsorbent was studied by Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and zeta potentials analysis. The results showed that the PPAB had a high microporous structure and the existence of organic compounds such as hemicellulose, cellulose, and lignin. Various parameters including initial Cr(VI) concentration, pH, and adsorbent dosage were studied. The results indicated that the adsorption process was pH dependent and maximum adsorption capacity of Cr(VI) was 57.637 mg/g at pH 2.0 and 35 °C with PPAB dosage of 0.05 g. The adsorption kinetics fitted well to the pseudo-second-order model and the correlation coefficients were greater than 0.999. The adsorption isotherm data could be better described with the Langmuir model, suggesting the homogeneous and monolayer adsorption. Moreover, the scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and Fourier transform infrared spectrum (FTIR) results showed that the surface of PPAB had plenty of developed pores after activation and the modification process was deemed to proceed between the O–H groups from pomelo peel and H₃PO₄ molecules. The main adsorption mechanism was attributed electrostatic interaction and ion exchange between the surface of PPAB and Cr(VI).

The objective of this research was to evaluate the biodegradation of chloroform by using biotrickling filter (BTF) and determining the dominant bacteria responsible for the degradation. The research was conducted in three phases under anaerobic condition, namely, in the presence of co-metabolite (phase I), in the presence of co-metabolite and surfactant (phase II), and in the presence of surfactant but no co-metabolite (phase III). The results showed that the presence of ethanol as a co-metabolite provided 49% removal efficiency. The equivalent elimination capacity (EC) was 0.13 g/(m³ h). The addition of Tomadol 25-7 as a surfactant in the nutrient solution increased the removal efficiency of chloroform to 64% with corresponding EC of 0.17 g/(m³ h). This research also investigated the overall microbial ecology of the BTF utilizing culture-independent gene sequencing alignment of the 16S rRNA allowing identification of isolated species. Taxonomical composition revealed the abundance of betaproteobacteria and deltaproteobacteria with species level of 97%. Azospira oryzae (formally dechlorosoma suillum), Azospira restrica, and Geobacter spp. together with other similar groups were the most valuable bacteria for the degradation of chloroform.