In the proposed model, the estrogen activity values and thyroid hormone activity values of PAEs molecules were normalized using the TOPSIS method by eliminating the dimension coefficients, and the comprehensive activity values of estrogen and thyroid hormone were obtained by analyzing the activity of each hormone and assigning the corresponding weight. The five pharmacophore models of hormone combined activity were constructed using the comprehensive activity values. Hypol 1 was the optimal pharmacophore model, showing good predictive power and significance. Then, the DBP, DNOP, and DMP molecules in environmental priority control pollutants were selected as the target molecules to perform common substitution reactions of hydrogen bond donor. Eleven PAEs derivative molecules with significantly reduced combined activity and single activity were screened. In analysis of the differences before and after modification of the docking parameters and amino acid residues before and after modification of PAEs and their derivatives, the reduced closeness between ligand and receptor leads to the decrease of thyroid hormones and estrogen activities. Moreover, the establishment of the models, not only shows that the PAEs hormone activity has certain linear relationships with the physical parameters of molecules but also shows that thyroid hormone activity and estrogen activity of PAEs is consistent with the hormone combined activity. The results confirmed the feasibility of the modified PAEs modification scheme with reduced combined activities of hormones, providing an important theoretical method for the construction of the pharmacophore model of combined activities of hormones and the study of PAEs derivative molecules.

Cross-linking of polymer hydrogels can be achieved by exposing the polymer to gamma radiation that induces production of polymer chain radicals resulting in cross-linking of chains. The present study was focused on fabrication of hydrogel by gamma irradiation for immobilization of bacterial cells. Hydrogels were prepared using 30 and 40% acrylamide at gamma irradiation dose of 5 kGy. Five bacterial strains BR-6, BR-14, BR-18, BR-21, and BR-26 screened for resistance to strontium were immobilized in hydrogels and evaluated for the bioremoval of strontium. Strontium content for different strains was 4.21–4.68 μg/ml after 3 days in the presence of free cells grown in 5 μg/ml strontium, while for immobilized cells, the strontium content was 3.35–3.81 μg/ml (30% acrylamide gel) and 3.46–3.99 μg/ml (40% acrylamide gel). After 10 days of incubation, the strontium content was reduced to 0.94–1.26 μg/ml (30% acrylamide gel) and 0.82–1.07 μg/ml (40% acrylamide gel), and for free cells, strontium content was 1.34–1.41 μg/ml. 72–75% bioremoval of strontium by free cells of different strains BR-6, BR-14, BR-18, BR-21, and BR-26 was observed after 10 days of incubation. 77–83% reduction in strontium content was observed in the presence of cells immobilized in 30% acrylamide, whereas higher reduction of 80–85% was observed for cells immobilized in 40% acrylamide after 10 days. At higher concentration of 10-μg/ml strontium, 62 to 71% reduction was observed with immobilized bacterial cells. Obtained results indicated that immobilized bacterial cells in hydrogels prepared by gamma irradiation were found to have significantly higher efficiency as compared to free cells for bioremoval of strontium ions.

This study aimed to develop Ca-alginate immobilized Providencia vermicola as a reusable biosorbent to recover palladium ions from acidic solutions. To examine the adsorption characteristics and availability of Ca-alginate immobilized P. vermicola for Pd(II) recovery, several experiments such as SEM-EDX, FT-IR, isotherm, kinetics, fixed-bed columns, desorption, and reusability were conducted. The results of SEM-EDX and FT-IR analyses demonstrated that amino and carboxyl groups were the main contributors in the Pd(II) biosorption process and that hydroxyl and phosphate groups were also critical for Pd(II) adsorption. The adsorption isotherms could be well described by the Langmuir model, and the maximum adsorption capacity was 197.23 mg g⁻¹. Kinetic experiments suggested that the biosorbent reached adsorption equilibrium within 60 min. After adsorption, the Pd(II) bound to the Ca-alginate immobilized P. vermicola was easily desorbed with 0.1 M HCl. A regeneration test of this Ca-alginate immobilized P. vermicola biosorbent revealed that it could be used for at least five cycles with high adsorption capacity. These results indicated that Ca-alginate immobilized P. vermicola has the extraordinary potential to adsorb metal ions from industrial wastewater.

Due to the serious pollution and great harm of steel pickling waste liquor, the treatment of the waste liquor with high concentration of iron ion has been a problem in a lot of countries around the world. A simple electrochemical method is proposed for recovering iron from steel pickling waste liquor with graphite plates as electrodes. This study investigated the effects of reaction parameters on the concentration of residual total iron (TFe) in steel pickling waste liquor, including initial pH, reaction temperature, electrode distance, current density, and electrolytic time. Under the optimal reaction condition, the removal efficiency of TFe was 99.98%. The obtained precipitates were measured by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It was found that the precipitates were high purity of Fe₃O₄ with small amount of γ-Fe₂O₃. This method will provide an effective and potential solution for resource recycling of steel pickling waste liquor.

The study aimed to evaluate the techniques of main principal components analysis (PCA) and hierarchical cluster analysis (HCA) as a criterion to monitor the removal of nitrogen forms and phosphorus in sequential upflow anaerobic sludge blanket (UASB), submerged aerated biological filters (SABF), and horizontal subsurface flow constructed wetland (HSSF-CW) treating different organic loads of swine wastewater. System was conducted in four organic loads of swine effluent. The UASB reactor did not provide satisfactory removal of nitrogen and phosphorus. In SABF, dissolved oxygen increased by more than 50 mg L⁻¹ in nitric forms between phases I and IV. The HSSF-CW removed 87.5 and 63.1% and 70 and 42 kg ha⁻¹d⁻¹ of nitrogen and phosphorus, respectively. The PCA showed the effect of salinity and nitrogen/organic load measured and nitrogen and phosphorus removal with high positive correlation (r > 0.80). Two components extracted from the 7 variables were responsible for 81.8, 66.7, and 61.6% of the original influent and effluent data from the UASB, SABF, and HSSF-CW reactors, associated by nutrient removals. There was a reduction in HCA similarity with application of the sequential biological treatment, with the formation of four clusters and the central highlight of the nitrite and nitrate in the SABF reactor. The multivariate techniques presented in this document reduce the number of analyses, maintaining the representativeness of the monitoring data for wastewater treatment. Graphical abstract

To determine the role of organic matter in the attenuation of acid rock drainage (ARD), microcosm-based experiments were performed using ARD stimulated with plants and manures. Initial mineralogical, organic geochemical and microbial analyses indicated a predominance of goethite, a substantial amount of organic carbon originating from local sources, and a bacterial community comparable with those detected in a range of ARD sites worldwide. After 100 days of incubation, changes in the mineralogical, organic and microbiological composition of the ARD demonstrated that the plant additions stimulate microbes with the potential to degrade this organic matter but do not necessarily cause substantial Fe(III) reduction. Conversely, the greatest observed stimulation of Fe(III) reduction, associated with an increase in pH to near-neutral values, was observed using manure additions. These results demonstrate that the use of the optimal natural carbon source is important and can promote the metabolism of microorganisms potentially fuelling a range of geomicrobial processes, including iron and sulfate reduction.

The paper describes optimization of mathematical models for determining the main characteristics of the source of environmental pollution. A modification of the classical Newton’s method for finding a numerical solution of the constructed mathematical models for identifying the parameters of an environmental pollutant has been developed. A modification of the classical Newton’s method is obtained, which makes it possible to reduce the total number of calculations in the process of determining the main characteristics of the pollution source. A number of software-implemented computational experiments have been carried out for the model for determining the height of the pipe of the pollution source and the concentration of emissions on it, the model for determining the full location of the pipe of the pollution source and the concentration of emissions from the source. The possibility of complete localization of the pollution source in less than 40 measurement iterations using 1 post of the air pollution monitoring system has been established. The proposed method makes it possible to reduce by 3 times the number of simulation iterations for detecting a source of pollution in comparison with classical methods for solving inverse problems during monitoring of air pollution.

The uncontrolled discharge of organic and inorganic substances causes overenrichment of water bodies by nutrients resulting in eutrophication which disturbs the flora and fauna balance of the lake ecosystem affecting its water quality. Therefore, it is necessary to remove excess nutrients from contaminated lake water. The present investigation was attempted to reduce high organic content and excess nutrients from the sewage-contaminated lake water using microalgae and bacteria in the form of activated sludge. Comparative analyses in three different setups state that maximum efficient removal of nutrients and organic matter (chemical oxygen demand [COD]) was achieved by the symbiotic co-culture than stand-alone cultures of microalgae and activated sludge. The highest removal of nitrates (NO₃⁻) and phosphates (PO₄⁻) was 93% and 99% with maximum removal of COD by 73% in the case of co-culture. The maximum biomass obtained was 7.8 g/L in the co-culture system. Fourier transform infrared spectroscopy confirms the presence of fatty acids and lipids in the microalgae biomass. The effect of cultivation time and pH was studied in optimization for simultaneous biomass production, organic matter reduction and for removal of nutrients using central composite design (CCD) under response surface methodology (RSM). The optimized results were in good agreement with the experimental results. Graphical Abstract

The black-odor phenomenon in polluted urban rivers is a serious environmental problem that has received increasing attention in the recent years. The low redox potential (less than − 100 mV) in the sediment is considered to be the key factor causing the occurrence of black-odor phenomenon. Here, we studied the structure and function of the microbial community during the remediation of urban rivers. Results showed a clear improvement in water quality after undergoing river remediation processes. The on-site treatments showed a succession in the microbial composition and their predicted functions. The primary iron- and sulfur-reducing bacteria (Thiobacillus, Sulfuricurvum, and Sulfursoma) and the related reactions rapidly decreased after the dredging treatment but reappeared after a year. The structure and abundance of nitrogen and methane participants were also affected by river remediation process. These results indicated that although the water quality temporarily improved shortly after a dredging process, a recurrence of the black-odor phenomenon may occur as a result of the rebound in the microbial communities.

Although much previous research effort has examined the impacts of metal contamination on macrobenthic assemblages in subtidal sediments, little attention has been directed at macroinvertebrate responses in intertidal mangrove habitats. Thus, in order to assess the unique responses of mangrove macroinvertebrate assemblages to sediment metal(loid) contamination, total, normalised and bioavailable metal(loid)s (Mn, Pb, Cr, Cd, As, Se, Co, Ni, Zn and Cu) were assessed within and between four mangrove locations in Lake Macquarie, NSW, Australia, and compared to resident macroinvertebrate assemblages over two sampling occasions. Mangrove biomass and physicochemical properties of sediment are known to influence macroinvertebrate assemblages, and as such, were also assessed to account for any potential confounding effect on macroinvertebrate assemblage composition. Significant differences in total and bioavailable metal(loid) contamination were found between and within locations and were consistent over time. Sediments at contaminated locations presented a high risk to biota with bioavailable concentrations of Pb, Cd, Zn found to exceed sediment quality guidelines and concentrations of Se capable of adverse impacts to biota. Macroinvertebrate assemblage composition varied with metal(loid) contamination loads present at study locations. Metal(loid) contamination was significantly correlated with macroinvertebrate assemblages over two sampling periods. Further analysis revealed that 71% of macroinvertebrate assemblage composition could best be explained by a combination of five variables namely, bioavailable Mn, Zn, and Se, number of mangrove seedlings and mean mangrove biomass. Rather than tolerant polychaetes dominating metal(loid)-contaminated sediments (as is found generally in subtidal sediments), polychaetes in intertidal mangroves appeared to be relatively sensitive to metal(loid) stress. Further, decapod crustaceans in the family, Varunidae, and gastropod molluscs, in the family, Amphibolidae, were found to be metal-sensitive taxa and may be employed in future studies as indicator taxa of sediment metal(loid)-related impacts in south-eastern Australian mangrove forests.