The purpose of this research was to evaluate the biodegradation extent of petroleum hydrocarbons by Phormidium ambiguum strain TISTR 8296 in the presence of inorganic nutrients and heavy metals as co-contaminants. In this context, waste motor oil served as a source of petroleum hydrocarbons. Strain TISTR 8296 grew actively with waste motor oil at 0.5–2.0% (v/v) concentrations and also exhibited good biodegradation potential at this concentration range. Meanwhile, its growth and biodegradation capacity fell down with increasing oil concentration to 3.0 and 4.0%. Strain TISTR 8296 adapted quickly to pH changes, showing good growth ability and biodegradation capability at a pH range of 4.0–9.0 with an acidic pH of 4.0 and 5.0 appearing to decelerate its biodegradation efficiency. The addition of PO₄ ³⁻ and NO₃ ⁻ exerted a strong stimulatory effect on growth and biodegradation efficiency, while a slight promoting effect was observed for NO₂ ⁻. By contrast, amendment of NH₄ ⁺ as well as heavy metals caused a substantial inhibitory effect on growth and biodegradation efficiency with NH₄ ⁺ and Mn(II) appearing to show a weak suppressing effect. GC-MS analyses indicated that strain TISTR 8296 could transform and degrade both aliphatic and aromatic compounds.

The mechanisms involved in immobilization of soil Cu and the role of extracellular polymeric substances (EPS) in Cu(II) adsorption by Bacillus subtilis DBM were investigated in this study. Adsorption and desorption experiments with intact DBM cells revealed that complexation with surface functional groups and intracellular accumulation were involved in the immobilization of soil Cu. The removal of EPS using cation exchange resin resulted in a 26.6% decrease in the Cu(II) adsorption capacity relative to untreated cells. Compared to intact cells, EPS-free cells showed a 9.9% decrease in the proportion of complexed Cu(II), while the intracellular fraction increased by 8.0%. Surface complexation modeling indicated that the total concentration of complexation sites on the intact DBM cell surface was 1.11 mmol/g dry biomass, which was decreased by 17% to 0.92 mmol/g after EPS removal. Infrared analysis revealed that the pKa values of the carboxyl and phosphate groups in the DBM cell wall differed from those in the EPS. Carboxyl, carbonyl, hydroxyl, amino, and phosphate groups were involved in binding Cu(II) by both intact and EPS-free cells, and Cu(II) was more likely to combine with organic rather than inorganic phosphates. The presence of the EPS increased the binding potential of surface functional groups and may help to prevent heavy metals from entering the cells.

The efficiency of the following systems: photolysis (UV-C only), photocatalysis with titanium-dioxide (UV-C/TiO₂), photocatalysis with granular-activated carbon (UV-C/GAC), and by adsorption on GAC, was assessed under different initial contaminant concentrations, i.e., 0.1–100 mg L⁻¹. The experiments were conducted in a batch photocatalytic reactor (1.9 L and 32 W UV power). It was found that UV-C/TiO₂ and UV-C/GAC systems showed fairly equal removal efficiencies under lower MNZ concentrations (0.1–5 mg L⁻¹) compared to higher concentrations at similar catalyst loading of 2.5 g L⁻¹. A decline in removal rate (based on first-order reaction) was observed with respect to increase in initial MNZ concentration in all systems. MNZ removal by adsorption on GAC was much lesser compared to UV-C only, UV-C/TiO₂, and UV-C/GAC systems. The adsorption data well correlated with the Freundlich model indicated that the adsorption was on the heterogeneous surface of the catalyst. The effectiveness of the systems were evaluated by calculating electrical energy consumed per order (E EO). The lowest E EO value was found to be for UV-C/TiO₂ (0.03 kWh m⁻³ order⁻¹) for the degradation of 0.1 mg L⁻¹ of MNZ compared to UV-C/GAC (0.06 kWh m⁻³ order⁻¹), UV-C only (0.15 kWh m⁻³ order⁻¹), and adsorption (0.44 kWh m⁻³ order⁻¹). The total organic carbon and nitrogen ion analyses have confirmed the mineralization of MNZ via aliphatic carboxylic acid compounds in the photocatalytic system. Overall, the photocatalytic system seems to be an energy-efficient treatment option for the removal of MNZ and similar other micropollutants.

This study aimed to investigate the potency of soil reflectance spectroscopy in the visible and near infrared (Vis-NIR) spectral regions in estimating soil heavy metal pollution in the western coastal front of Thessaloniki (N. Greece) and how the protocol used for chemical analyses can affect the models’ performance. For this purpose, 49 topsoil samples were collected and the concentrations of Cd, Cr, Cu, and Pb were determined by two different analytical methods, i.e., ISO 11466 based on the technique of atomic absorbance spectrometry (AAS) and ISO 14869-1 using the technique of inductively coupled plasma-atomic emission spectrometry (ICP-AES). The spectral signatures were applied for modeling the metal concentrations by using the partial least squares regression (PLSR) method. To eliminate the “noise” of data and enhance the models’ accuracy, four spectral pre-treatment methods were used. The overall results showed that there is heavy metal pollution in the soils of specific areas in the studied region and that the use of different chemical analytical methods can affect the performance of examined prediction models. Better prediction models were created for the cases of Pb, Cu, and Cr concentrations, which were estimated by the application of ISO 14869-1, while for the case of Cd better prediction models were obtained, by the application of ISO 11466. These results may indicate that soil reflectance spectroscopy can measure the total heavy metal content in soil samples.

The aim of this study was to evaluate the genotoxic and mutagenic potential of contaminated soil diluted in acidic solutions and not acidic, in the offspring of rats exposed during pregnancy and neonatal periods. To this end, a comet assay and micronucleus test were performed. Soil samples were solubilized in the following three solvents: distilled water (control group), acid solvent at pH 5.2, and acid solvent at pH 3.6. Soil and solvent were mixed in a rate of 1:2 in g/mL, and hydrofluoric acid was used in the acid solvents. In the comet assay, the tail length, percentage of DNA within the tail and tail moment was analyzed in the whole blood of the pups that were studied. The number of micronuclei found in the bone marrow cells was counted in the micronucleus test. In all parameters evaluated in the comet assay, the group exposed to the lowest pH value when associated with contaminated soil (p < 0.05) had the most damage. However, the micronucleus test showed differences between all exposed groups and the control group (p < 0.05). These results reaffirm the health risks related to the exposure to soil contaminants.

A comprehensive ecotoxicity assessment of three different nanosized TiO₂ (with 16, 36 and 89 nm particle diameter) and one microscale TiO₂ suspension (with 3264 nm particle diameter) was carried out with a special emphasis on the relation between product characteristics and toxic effect. The applied test battery included the combination of modified standardized tests (Aliivibrio fischeri bioluminescence inhibition test, Lemna minor growth inhibition test), and nonstandardized bioassays with unconventional physiological endpoints (Tetrahymena pyriformis phagocytic activity, the Daphnia magna heartbeat rate). Based on the lowest significant effect values, the tested aquatic organisms were the most sensitive to the microscale TiO₂ suspension (with 3264 nm particle size). Although the three nanoscale TiO₂ particles were aggregated in the A. fischeri and the L. minor growth media, significant inhibition rates were experienced at 0.1 and at 1 μg L─¹ concentration of nTiO₂ suspensions with 16 and 36 nm primary particle size, respectively. Larger aggregates may have also high impact on biological organisms. In case of the D. magna heartbeat rate test rapid agglomeration was avoided, but lower responses were found compared to other investigated systems. The short term T. pyriformis phagocytic activity test demonstrated outstanding sensitivity; three TiO₂ suspensions were significantly toxic even at 0.1 μg L─¹. The consequences of our study clearly indicated that nanoscale TiO₂ may have an impact on the aquatic ecosystem which is strongly influenced by aggregation. The effect of exposure duration and concentration as contributing factors in nano-titanium dioxide mediated toxicity was also demonstrated.

The pollution of the air and the monitoring of indoor air quality are receiving increasing attention worldwide, and many methodologies are now available to identify sources of pollution. However, there has been less work concerning the development of techniques to mitigate the effects of indoor air pollution. The aim of this study was to modify cotton fabrics with silver nanoparticles in order to use them in air conditioner filters. To achieve this goal, common fabrics purchased from commercial sources were evaluated in terms of their filtration properties (permeability, pressure drop, and collection efficiency) and were subsequently modified by impregnation with nanoparticles. This modification was achieved by immersion of the filters in nanoparticle suspensions. After drying the filter, collection of particulate matter was made in a toilet. The results showed that the filters impregnated with silver nanoparticles were able to significantly reduce the activity of microorganisms present in the airborne particulate matter, resulting in growth inhibition to the microorganisms which were retained (76.70%) and passed through (96.34%) the cotton filters.

A chelator, potassium dipropyl dithiophosphate, and humic acid were combined and used as a stabilizing agent to study the stabilization effect of the mixture on heavy metals in a contaminated sediment. The results indicated that the stabilization efficiencies for Cu, Zn, Pb, and Cd in the sediment were up to 99.98, 90.66, 99.38, and 92.83%, respectively, and the unstable Cu, Zn, Pb, and Cd fractions fell by 57.11, 54.74, 56.41, and 89.14%, respectively, when 5% potassium dipropyl dithiophosphate and 7% humic acid were added. This significantly reduced the bioavailability of the heavy metals. Under leaching caused by simulated acid rain (pH 3 and pH 5), the heavy metals mainly migrated from the solid phase to the liquid phase during the initial leaching period, and the Pb, Cu, Zn, and Cd leaching rates in the sediment after stabilization fell by 55–99%. Cu showed the greatest reduction. When the results for the sediment after stabilization were compared with the sediment before stabilization, the wheat stem height had increased by 53.62%, the dry weights of the leaves and roots increased by 86.25 and 34.85%, respectively, and Cu, Zn, Pb, and Cd enrichment in the wheat roots and leaves fell by 40–88 and 73–95%, respectively.

Pig slurry contains sufficient amount of nitrogen, phosphorus, and potassium for plant growth. If appropriately administered, this could substitute significant amounts of fertilizer. However, excessive fertilization with slurry causes environmental problems. To reduce environmental issues, solid-liquid separation or anaerobic digestion is needed to obtain a better distribution of nutrients. Solid-liquid separation produces a solid fraction rich in phosphorus and a liquid fraction containing ammonia, potassium, and high water content. Therefore, further concentration of ammonia is desired for any practical use. In this study, ammonia membrane stripping was carried out using polypropylene membranes and the impact of temperature, flow velocities, and liquid fraction pretreatment on the membrane contactor performance was tested. Sieved liquid effluents from a decanter centrifuge, a screw press, an AL-2 system (flocculation and filtration), and an anaerobic digester were tested. Since the properties of these liquid effluents vary, they might affect ammonia recovery. Thus, it is essential to investigate which effluent is most suitable as a feed for a membrane contactor and what is the cost of preprocessing. The mean ammonia mass transfer coefficient at 30 °C was found to be equal to 17 ± 2 × 10⁻³ m h⁻¹. At 50 °C, it was found to be equal to 29 ± 2 × 10⁻³ m h⁻¹ for all the tested effluents. This means that sieving after slurry separation or anaerobic digestion alleviates the influence the solid-liquid separation has on ammonia membrane stripping. However, the cost evaluation showed that solid-liquid separation using a decanter centrifuge followed by sieve draining is the cheapest of the methods investigated.

Agricultural practices and industrial growth have contaminated the environment with heavy metals and many other harmful compounds. Arsenic (As) has been highlighted as a major heavy metal affecting growth and development of plants as well as causing severe human health hazards through food chain contamination. Most studies of heavy metal impacts address only one of these aspects, overlooking the effect of pollution on the plant as a whole. In this work, our objective was to determine the effect of arsenic stress on physiological, biochemical, and morphological characteristics in seedlings of two cultivars of maize with different arsenic tolerance. This study investigated the effects of varying levels of arsenic (As) stress on growth, enzymatic characteristics, and cell ultrastructure in seedlings of As-sensitive and As-tolerant maize cultivars (Shiyu No. 9 and Dongdan90, respectively) grown in hydroponic culture. Compared to Shiyu No. 9 at the same As concentration, Dongdan90 maintained higher values of biomass, shoot length, root length, and activity of superoxide dismutase, peroxidases, and catalase, but had lower malondialdehyde content, As accumulation, and non-protein thiol. High As concentrations inhibited the growth of both cultivars, while lower concentrations stimulated it. The As-tolerant cultivar also maintained the structural integrity of cells and tissues more efficiently under As stress. These findings demonstrate a link between the physiological and physical impacts of heavy metals on crop plants that paves the way for improved interventions to deal with heavy metal pollution.