Μg Dm Research Articles

Quantitative, Qualitative and Thermal Aspects of Rainwater Retention on Wetland Roofs

Wetland roofs (WRs) are a multi-functional green infrastructure measure to mitigate the negative effects of climate change. The present work advances knowledge in the field of WRs by analyzing the performance of rainwater management, focused on water sufficiency, water quality and cooling potential. Automatic monitoring, covering weather conditions, temperature and the conductivity of WR water, and the amount of outflow into retention tanks, was supported with automated sampling of water for laboratory analysis of BOD5, phosphate phosphorus, suspended solids, electrical conductivity (EC), redox potential (Eh), color and pH. From April to September 2022, a precipitation deficit of 395.45 mm and a negative climatic water balance of 267.91 mm were observed. It was necessary to fill up the system several times in order to maintain water at the assumed level. In most cases, the values of EC observed during the monitoring period were higher than those reported for rainwater. Continuous monitoring of EC in the wetland was a useful tool for the observation of operating activities in the system; however, it was not sufficient for system control. BOD5 values did not exceed 6 mg dm−3 and were lower than reported for urban rainwater retention reservoirs. Suspended solids values did not exceed 27 mg dm−3. Color varied between 0 and 101 PtCo, with the highest values noted in July and the beginning of August. The pH value ranged between 7.28 and 8.24. The Eh varied between 155 and 306 mV, with lower values associated with the filling up of the wetland. Peak values of PO4-P were observed between the end of July and the beginning of September 2022, with a maximum concentration of 232 µg dm−3 utilized by the wetland within one month. Monitoring of the water and air temperature showed a thermal buffering effect of the wetland. The results of the research, conducted during the growing season, allow for better management of rainwater on the roof. However, there is a need to expand the scope of the analyzed water quality parameters. Although there are several limitations to the analysis, the present study partially fills the existing knowledge gap and may generate further interest in this topic among researchers and decision-makers.

Phenotypic Diversity in Leaf Cuticular Waxes in Brassica carinata Accessions.

Brassica carinata has received considerable attention as a renewable biofuel crop for semi-arid zones due to its high oil content and polyunsaturated fatty acids contents. It is important to develop new drought-resistant cultivars of B. carinata production to expand its areas into more arid regions. The accumulation of leaf cuticular wax on plant surfaces is one mechanism that reduces non-stomatal water loss, thus increasing drought resistance in plants. To explore phenotypic variations in cuticular wax in B. carinata, leaf waxes were extracted and quantified from a diversity panel consisting of 315 accessions. The results indicate that the accessions have a wide range of total leaf wax content (289-1356 µg dm-2), wax classes, and their components. The C29 and C31 homologues of alkanes, C29 ketone homologue, C29 secondary alcohol, and C30 aldehyde were the most abundant leaf waxes extracted from B. carinata accessions. The high heritability values of these waxes point to the positive selection for high wax content during early generations of future B. carinata breeding programs. Positive correlation coefficients, combined with the effects of these waxes on leaf wax content accumulation, suggest that modifying specific wax content could increase the total wax content and enhance cuticle composition. The identified leaf wax content and compositions in B. carinata will lead to the future discovery of wax biosynthetic pathways, the dissection of its genetic regulatory networks, the identification of candidate genes controlling production of these waxes, and thus, develop and release new B. carinata drought-tolerant cultivars.

Selenium biofortification via soil and its effect on plant metabolism and mineral content of sorghum plants

Sorghum has excellent potential to be used in the supplementation of selenium (Se) to humans and animals when compared with other grain crops due to its protein content, rusticity, and great tolerance to various stressing conditions. Few studies have been dedicated to explore Se biofortification strategies in sorghum plants, especially in tropical agroecosystems. In this context, the objective of this work was to evaluate the efficiency of different Se doses (0, 60, 240, and 480 µg dm−3) and Se sources (SeA - potassium hydroxy-selenide, SeB - methyl hydroxy-selenide, SeC - hydroxy-selenide, and SeD - sodium selenate) in Se biofortification of Sorghum bicolor L., as well as in its antioxidant system, and the contents of carbohydrates and mineral in response to soil Se application. The increase in Se content in the grains and the shoots were closely related to the increments in applied Se doses. The greater absorption efficiency by the roots and % Se recovery occurred with the application of SeD. Selenium application influenced both the antioxidant system and carbohydrates in a positive way. In summary, considering the parameters evaluated, the Se sources SeB (methyl hydroxy-selenide) and SeC (hydroxy-selenide) at a dose of 240 µg dm−3 of Se and SeD (sodium selenate) at a dose of 60 µg dm−3 of Se are considered promising for the biofortification of sorghum.

Physical-chemical characterization of uranium containing sediments

The presented paper is intended to study the chemical behaviour of combined geogenicanthropogenic uranium content in specific stream sediments. The sampling points have been chosen with respect to the natural conditions in the locality of groundwater outflow from a former uranium mine adit in Považský Inovec mountain range, near Kálnica village. Besides the total uranium determination and physical-chemical characterization of the relevant water- and sediment samples we carried out modified Tessier type sequential fractionation extractions of natural- and artificially contaminated sediment samples after time dependent agitation in air and in the atmosphere of argon. The obtained results have been compared with those fulfilled with montmorillonite K-10. The total uranium concentrations of the relevant groundwater samples as well as of stream sediments have been determined by ICP-MS using HP 4500. The determinations of uranium in extracts have been accomplished according STN757614, utilizing arsenazo III as a selective complex forming reagent for spectrophotometric determination of uranyl-ions at 650 nm. The total uranium concentration of the groundwater outflow and in the sediment taken in its immediate vicinity has been 31.75±0.35 μg dm-3 and 38.0±2.7 μg g-1 respectively. Unlike montmorillonit K-10, in which the carbonate-bound fraction of uranium after 1 week aeration and agitation in argon atmosphere represents 22.8% and 18.6% respectively, uranium in investigated sediments has been present predominantly in carbonate-bound fraction-reaching under similar conditions 38.6% and 26.6%, respectively.

Optimization of Nd(III) removal from water by Ulva sp. and Gracilaria sp. through Response Surface Methodology

This study focused on the impact of 3 key variables (macroalgae mass, water salinity, and Nd(III) initial concentration) on the performance of two living macroalgae (Ulva sp. and Gracilaria sp.) in the removal and bioaccumulation of Nd(III), finding the optimal operating conditions through the Response Surface Methodology (RSM). Experiments were carried out in batch conditions stablished using a Box-Behnken design of 3 factors-3 levels (macroalgae mass of 0.5, 3.0 and 5.5 g dm-3; water salinity of 10, 20 and 30; and Nd(III) initial concentration of 10, 255 and 500 µg dm-3). The linear, quadratic and combined effects of the variables were described by RSM through a second order polynomial function. Optimized conditions were calculated by nonlinear regression using the Nelder-Mead simplex algorithm. Results evidenced the great capacity of both species to remove Nd(III), with removals around 80 % for the conditions: initial concentration of Nd(III) of 255 µg dm-3, water salinity 10, and macroalgae mass of 5.5 g dm-3. 3-D Response Surfaces showed that after 72 h of experiment, the most impactful variable on the removal process was the macroalgae mass. Regarding bioaccumulation, for the conditions studied, the higher the Nd(III) initial concentration the greater was its accumulation. The RSM tool made it possible to obtain the optimal conditions for both species, for contact times of 72 and 120 h. The proposed methodology can be applied in the recovery of Nd (which is a critical element) from contaminated waters, with the aim of its reintroduction in industrial production processes (recycling).

Bioaccumulation processes for mercury removal from saline waters by green, brown and red living marine macroalgae.

Mercury is a very toxic metal that persists and accumulates in the living organisms present in the aquatic systems and its elimination is an urgent need. Two green (Ulva intestinalis and Ulva lactuca), brown (Fucus spiralis and Fucus vesiculosus), and red (Gracilaria sp. and Osmundea pinnatifida) marine macroalgae were tested for mercury removal from saline waters. The ability of each species was evaluated to the initial mercury concentrations of 50, 200, and 500 μg dm-3 along 72 h. In general, all species exhibited good performances, removing 80.9-99.9% from solutions with 50 μg dm-3, 79.3-98.6% from solutions with 200 μg dm-3, and 69.8-97.7% from solutions containing 500 μg dm-3 of mercury. Among the macroalgae, Ulva intestinalis showed the highest affinity to mercury and it presented an uptake ability up to 1888 μg g-1 of Hg(II) and bioconcentration factors up to 3823, which proved its promising potential on Hg removal.

Survival rate and changes in foraging performances of solitary bees exposed to a novel insecticide

Solitary bees are among the most important pollinators worldwide however population declines especially in croplands has been noticed. The novel pesticide sulfoxaflor is a competitive modulator of nicotinic acetylcholine receptors (nAChR) in insects. While there is evidence of a negative impact of neonicotinoids on bees of several social organization levels, our overall knowledge on the impact of sulfoxaflor on bees is poor. Here we present for the first time a study showing effects of field realistic doses of sulfoxaflor on solitary bees. Bees submitted to long term exposure of field realistic doses of sulfoxaflor (5 µg dm-3, 10 µg dm-3, 50 µg dm-3) and control were observed regarding their survival rate. Moreover, we recorded metrics related to flower visitation and flight performance. We discover that the highest field realistic dose is lethal to Osmia bicornis along five days of exposure. The effect of sulfoxaflor reduces the outcome of foraging, important features for fruit and seed production of cross-pollinated plant species. Bees exposed to pesticide visited flowers mostly walking rather than flying. Flight performance was also impaired by the pesticide.

Heavy Metals in Fresh Waters of Kazakhstan and Methodological Approaches to Developing a Regional Water Quality Classification

The study aimed to define the classes in the Heavy Metals Section of the Regional Environmental Ranking System based on long-term data (1997-2017). When distinguishing water quality classes, the following factors were taken into account: background content of heavy metals, content of heavy metals in water bodies exposed to different levels and character of anthropogenic pollution, and response of biological communities to toxic pollution of their natural habitats. According to the proposed classification, the non-contaminated water of Сlass 1 contains the following: Cd<0.2, Cu<2.5, Zn<4, Pb<3, Cr<0.5, and Ni<0.5 μg dm-3. Class 2 water is characterized by Cd<0.5, Cu<6, Zn<6, Pb<7, Cr<1, and Ni<2 μg dm-3 content. Moderately polluted water of Class 3 contains Cd<3, Cu<10, Cr<10, Ni<10, Zn<20, and Pb<20 μg dm-3. Concentrations of all heavy metals increase proportionally and exceed 30-100 μg dm-3 in the most polluted water of Class 6. The proposed methodological approach assesses not only the local content of heavy metals in water bodies of Kazakhstan but also the degree of toxic pollution of their vast catchment basins. The proposed methods are applicable to other arid regions with similar physical and climatic conditions.

The toxicity of BDE-47 to the photosystem of Lemna minor fronds

To elucidate the toxicity of 2,2ʹ,4,4ʹ-tetrabromodiphenyl ether (BDE-47) on photosynthetic primary processes, in vivo and in vitro treatments of BDE-47 were performed. The 20-d treatment in vivo (5 - 20 μg dm-3) suppressed the reproduction of duckweed (Lemna minor) and led to decline in chlorophyll (Chl) content of fronds. The most obvious features of BDE-47-treated fronds included a Chl a fluorescence rise at the J phase and a depression at the G phase, whereas significant fluorescence rises at the L, K, and J phases were found on the ΔVt curve of thylakoid membranes treated with 10 - 15 mg dm-3 BDE-47 for 4 h (in vitro). In both in vivo and in vitro experiments, the BDE-47 treatments significantly reduced the density of the active reaction centers (RC/CSo), affected the efficiency and speed of photosynthetic electron transfer [the maximum quantum yield of photosystem (PS) II photochemistry - Fv/Fm, quantum yield for electron transport (at t = 0) - φEo, electron transport flux per excited cross section - ETo/CSo, and net rate of reaction centers closure at 300 and 100 μs - dV/dto and dVG/dto, respectively], and increased energy dissipation [quantum yield for energy dissipation (at t = 0) - φDo, dissipated energy flux per reaction center - DIo/RC, and issipated energy flux per excited cross section - DIo/CSo]. The BDE-47 at 5 - 15 mg dm-3 had no impact on the minimum (initial) fluorescence (Fo) and total electron carriers per reaction center (Sm) of the thylakoid membranes, but PS II units were less tightly grouped (a positive L-band). On the contrary, there was no positive L-band on the difference between relative fluorescence intensities of the normalized induction curves from 50 μs to 300 μs (WK) of each BDE-47 treatment and control (ΔWK), and Fo and Sm increased after the treatment with BDE-47. The above results indicate that BDE-47 not only affected the permeability of thylakoid membranes, but also relaxed the structure of PS II, thereby affecting the function of PS II. In addition, BDE-47 could induce secondary damage to the PSs in duckweed fronds.

Study of the influence of the region, the depth and the drying process on the chemical composition of Gelidium corneum from Moroccan coast

The Gelidium corneum is an algae exploited industrially for its richness in agar. In addition, it is known for its anti-inflammatory, antioxidant and anti-microbial activities. In this study, we established a general overview of the macronutrient composition of G. corneum and compared this composition according to harvest site, harvest depth and drying process. Proteins, lipids and carbohydrates of samples are measured by different methods. The analysis of results show that the protein concentrations of the El Jadida and Mohammadia samples are significantly higher than Casablanca samples (0.026 ± 0.0007 μg/μg DM, 0.024 ± 0.001 μg/μg DM, 0.006 ± 0.0007 μg/μg DM, p < 0.05 respectively). However, Casablanca samples are significantly richer in total carbohydrates (0.023 ± 0.002 μg/μg DM, p < 0.05) and less rich in reducing carbohydrates (0.0001 ± 0.00001 μg /μg DM, p < 0.05) compared to other samples. The lipid concentrations of the samples from all harvest sites do not show any significant difference. According to depth, total protein and sugar concentrations were significantly higher in the coast versus depth samples (0.035 ± 0.004 μg/μg DM vs 0.025 ± 0.0007 μg/μg DM, 0.035 ± 0.006 μg/μg DM vs 0.012 ± 0.005 μg/μg DM, p < 0.05 respectively). For the drying process, protein, total sugars and lipid concentrations were significantly higher in open air samples compared to oven samples (0.025 ± 0.0007 μg/μg DM vs 0.013 ± 0.0003 μg/μg DM, 0.012 ± 0.002 μg/μg DM vs 0.006 ± 0.002 μg/μg DM, 6% vs 3%, p < 0.05 respectively). Our results demonstrate that the chemical composition of G. corneum varies according to the harvest region. In addition, samples harvested on the coast and dried in the open air are the most rich in macronutrients.

Distribution and superposed health risk assessment of fluorine co-effect in phosphorous chemical industrial and agricultural sources

The industrial and agricultural activities based on phosphorous can increase the F content in the surrounding area, causing a widespread adverse effect on the organisms. However, the current information on the superposed health risk posed by the multi-exposure to the F contamination in an area jointly affected by agricultural and industrial activities (DA) is limited. Herein, the F distribution in multi-environmental media and the exposure risk to humans by ingestion, inhalation, and dermal contact pathways are studied in an DA. The content of soil water-soluble fluorine (WF) was higher in the DA than in the area individually affected by agricultural activities (SA). This indicated a superposed contribution of the industrial and agricultural activities to increase the F toxicity in the soil. The correlation of the soil pH and the organic matter content with the soil WF concentration in DA suggested an inter-relationship between the soil physicochemical properties and the toxicity of F in the soil by industrial and agricultural activities. Irrigation water was not a major anthropogenic source of the cropland soil F. The large variation in F concentration in the crops (101.8–195.6%) might have originated from the discrepancies in the soil F content and air F concentration. The air F pollution (0.6–1.6 μg dm−2 d−1) in the area particularly influenced by intensive industrial activities should be important. The exposure of residents to F was mainly from the ingestion of F-enriched crops. The higher exposure of adults to F than that of children could be attributed to more industrial and agricultural outdoor activities, larger exposure area of the skin, and more daily ingestion of F-enriched food by adults. Overall, present insights into the distribution of and the multi-exposure to F may be beneficial for decreasing the adverse F effects on the residents in DAs worldwide.

Determination of monoamine neurotransmitters and metabolites by high-performance liquid chromatography based on Ag(III) complex chemiluminescence detection

A novel, simple and efficient chemiluminescence system has been developed for the determination of monoamine neurotransmitters and metabolites. By using the Ag (III)-luminol chemiluminescence system as a detector, a high performance liquid chromatography chemiluminescence method (HPLC-CL) was established and used to detect seven monoamine neurotransmitters. Under the optimized conditions, the detection limits (3S/N) of epinephrine (E), levodopa (l-DOPA), dopamine (DA), serotonin (5-HT), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxypentylacetic acid (5-HIAA) were 20.0 μg dm−3,15.0 μg dm−3, 15.0 μg dm−3, 8.0 μg dm−3, 2.0 μg dm−3, 2.0 μg dm−3 and 3.0 μg dm−3, respectively. Moreover, they were well within the linear range of 50–1000 μg dm−3, 50–1000 μg dm−3, 50–1000 μg dm−3, 25–1000 μg dm−3, 5–25 μg dm−3, 5–25 μg dm−3 and 10–30 μg dm−3, respectively. The average recovery varied between 84.82% and 110.4%. The method has the attributes of simplicity, high sensitivity, and high efficiency. The sensitization and inhibition mechanisms for luminol-[Ag(HIO6)2]5–- analytes CL system were proposed by CL spectra and free-radical capture experiment.

Valuation of banana peels as an effective biosorbent for mercury removal under low environmental concentrations

The use of banana peels as biosorbent for mercury sorption from different aqueous solutions was investigated in this work. The impact of the operating conditions, such as biosorbent dosage, contact time and ionic strength was evaluated for realistic initial Hg(II) concentrations of 50 μg dm−3. Biosorbent dosage and contact time showed more influence on Hg(II) removal than ionic strength, and their increase led to improve Hg(II) uptake achieving final concentrations with drinking water quality. The kinetic behaviour of the sorption process was assessed through the reaction-based models of pseudo-first order, pseudo-second order and Elovich, being the last two more appropriated to describe the process. The equilibrium study showed that Freundlich isotherm provided the best fit to the experimental results (R2 = 0.991), which may suggest a multilayer mechanism at biosorbent surface, and the sorption capacity of banana peels obtained from Langmuir isotherm was 0.75 mg g−1. The ability of banana peels to sorb Hg(II) was also examined under real waters, like seawater and a wastewater, which confirmed the feasibility of the biosorbent. Additionally, a counter-current two-stages unit has been proposed for the application of banana peels as biosorbent in water treatments for mercury removal.

Experimental Measurement and Modeling of Hg(II) Removal from Aqueous Solutions Using Eucalyptus globulus Bark: Effect of pH, Salinity and Biosorbent Dosage.

Different experimental conditions were tested in order to optimize the Hg(II) removal by Eucalyptus globulus bark. Response surface methodology was applied to extract information about the significance of the factors and to obtain a model describing the sorption. The results were generated through the design of experiments by applying the methodology of a three-factor and three-level Box–Behnken design. The factors tested were pH (4.0, 6.5, and 9.0), salinity (0, 15, and 30), and biosorbent dosage (0.2, 0.5, and 0.8 g dm−3) to evaluate the Hg(II) removal using realistic conditions, such as contaminated natural waters with an initial Hg(II) concentration of 50 µg dm−3. The optimum response provided by the model was 81% of the metal removal under the optimal operating conditions: a pH value of 6.0, no salinity, and a biosorbent dosage of 0.55 g dm−3. Concerning the kinetic, the pseudo-second-order equation fitted better to the experimental results with between 0.973 and 0.996. This work highlights the promising valorization of this biomass, which is an industrial byproduct and makes available information about the influence of the variables for Hg(II) removal in water treatment processes.

Importance of Interfacial Activation and Proton Transfers during Redox Processes of Highly Inert Systems: Electrocatalytic Detection of As(III) and As(V) in Acid Medium

Noble metal nanoparticles (Pt, Rh, Ir Pd), when deposited on an inert electrode substrates, exhibit electrocatalytic properties during both oxidation of As(III) and reduction of As(V) in acid medium (e.g. 0.5 mol dm-3 H2SO4). For example, upon application of the appropriate potential, both As(III) and As(V) are preconcentrated on surfaces of Pt nanoparticles. Consequently, their presence can monitored under voltammetric conditions. Population of protons does affect the systems’ electrochemical characteristics. The nature of arsenic voltammetric peaks is strongly dependent on the preconcentration potential. While the reduction and deposition of As(III) is induced by adsorbed hydrogen on Pt formed at potentials lower than 0.25 V (vs. RHE), the adsorption and preconcentration of As(V) can be readily achieved at Pt oxides generated at Pt nanoparticles at potentials higher than 0.85 V (vs. RHE). From mechanistic point of view, voltammetric oxidation of bulk As(III) is catalyzed by Pt oxo species but electrocatalytic reduction of As(V) requires its prior adsorption. Electroreduction of the resulting As(V) adsorbates is catalyzed by both metallic platinum and by platinum on which hydrogen atoms are adsorbed; the resulting voltammetric peak current densities are dependent on concentration of As(V) in solution. A unique feature of the adsorbed As(III) and As(V) oxo species is the ability to agglomerate and form stable polynuclear electroactive films on Pt nanoparticles. Their performance resembles behavior of redox conducting polymers, and their redox transitions are fast and reversible. Electrochemical experiments are supported by the data from scanning and transmission electron microscopies and Raman spectroscopy. In conclusion, the present observations demonstrate the utility of Pt nanoparticles as the catalytic system for inducing of (otherwise highly inert) electrode processes of As(III) and As(V) in acid medium. While the electrocatalytic activity of platinum (particularly PtO) toward electrooxidation of As(III) was previously postulated, we clearly show here that arsenates(V) can be adsorbed, preconcentrated, and electrocatalytically reduced (without prior chemical treatment) and, thus, detected on surfaces of Pt nanostructures. On mechanistic grounds, As(V) must be first adsorbed on bare (metallic) Pt surface before the actual electron transfer can take place. In addition to the structural importance, involvement of protons is crucial to effective electrocatalysis. It is also noteworthy that the current signals can be correlated to concentration of As(V) in bulk solution. The present study also provides evidence of obtaining a stable redox-polymer-like As(III,V) oxo film capable of fast charge propagation (electron-self exchange rate on the level 8*106 dm3 mol-1 s-1) within the adsorbed layer existing on surfaces of platinum nanoparticles. The latter observation is of both fundamental and analytical significance. Although the experimental approaches are not optimized here, the detection of As(V) and As(III) down 5*10-6 and 2*10-6 mol dm-3, respectively, is feasible. The main drawback is that the baseline uncertainty limits its routine use in static solutions to concentrations above 2-5*10-6 mol dm-3. This level is not sufficient for practical purposes. For example, the US Environmental Protection Agency (EPA) defines the permissible level of arsenic in drinking water in the United States as 10 μg dm-3 (ca. 1.3*10-7 mol dm-3). Further research is being continued along this line.

Toxicity of atrazine and the products of its homogeneous photocatalytic degradation on the aquatic organisms Lemna minor and Daphnia magna.

Usage of atrazine, a widely used herbicide, is now banned in many countries. Although forbidden to use, significant concentration of this herbicide is still present in the environment. The study focused not only on the toxicity of atrazine itself but also on products of homogeneous photocatalytic degradation. Such degradation was very fast in given conditions (sufficient amount of Fe(III) in the reaction system)-more than 95% of the initial amount of atrazine was eliminated after 30 min of irradiation. The toxicity of atrazine and its photodegradation products were examined on the aquatic plant Lemna minor and microcrustacean Daphnia magna in both acute and chronic tests. While the growth inhibition assay of atrazine for Lemna minor revealed EC50 value of 128.4 μg dm-3, the herbicide did not affect Daphnia in the acute toxicity assay. A degradation product, desethyl-atrazine, has been demonstrated to have a pronounced negative effect on the plant growth. Both atrazine and desethyl-atrazine affect negatively the number of juveniles and number of clutches of Daphnia magna in the chronic toxicity assay. Photocatalytic degradation lowers the negative effect of atrazine in Daphnia magna while photodegradation products still negatively affect Lemna growth.

Ozone microbubble-aided intensification of degradation of naproxen in a plant prototype

Naproxen (NPX), one of the best-selling nonsteroidal anti-inflammatory drugs, is found in surface and drinking water at concentrations up to 1 μg dm−3. It has been emerging as a water contaminant during the last two decades. Conventional removal techniques, i.e. sewage treatment, membrane separation, filtration, and adsorption have been found to be inefficient for complete removal of NPX. Intensification of the wastewater treatment processes is important in order to achieve higher degradation efficiencies. Advanced oxidation processes (i.e. ozonation, photolysis, and photo-Fenton) have the greater capability of NPX removal. In the present study, a combination of ozonated microbubbles and H2O2 was used for effective removal of NPX. The use of microbubbles increased the mass transfer into the aqueous phase. Use of H2O2 with ozone increased the degradation process significantly, which confirms the − the hydroxyl radicals generated in situ under the alkaline conditions. The ozone supply rates were 0.39, 0.41, 0.44, and 0.48 mg s−1 and the corresponding reaction times were 10000, 2400, 840, and 240 s, respectively for 98−99% conversion for pH 9. The pseudo first-order reaction constants or O3 alone and H2O2 + O3 were in the range of 2.89 × 10−3 − 6.44 × 10−3 and 3.39 × 10−3 − 13.6 × 10−3 min−1, respectively. The effects of ozone supply rate and pH of the reaction system were also studied. The by-products were identified and a mechanism of ozonation of NPX was proposed. The main intermediates were 2-methoxy-6-ethyl naphthalene, (2-methoxy-6-methyl naphthalene, and 1-(6-methoxynaphtalen-2-yl) ethyl-hydroperoxide.

A shallow lake in an agricultural landscape – water quality, nutrient loads, future management

Abstract Qualitative analyses of nitrogen and phosphorus loads reaching the lake ecosystem provide a basis for pollution control, which is of paramount importance in shallow lakes due to the rapid turn-over of matter and energy. The studies of both external and internal loading were conducted in Lake Łeknenskie, a very shallow, through-flow lake situated in Western Poland. Strong eutrophication is manifested in rich rush vegetation and a lack of submerged macrophytes as well as nitrogen and phosphorus concentrations (max 13.04 mg N dm−3 and 0.32 mg P dm−3, respectively). Constant domination of cyanobacteria in the phytoplankton community was noted in almost all seasons with a 98% share in summer, resulting in 20 cm water transparency and 223 μg dm−3 of chlorophyll-a. The zooplankton community was dominated by rotifers. The main source of nutrients was the River Nielba. Spatial external nutrient loading was 1.93 g P m−2 yr−1 and 77.55 g N m−2 yr−1. An even higher load of phosphorus was released from the bottom sediments, 2.18 g P m−2 yr−1. A comprehensive action plan is required, aiming at the reduction of both external and internal nutrient loading. A series of solutions regarding local environmental conditions should be applied in the lake catchment, including biogeochemical barriers, denitrification walls, artificial retention basins or wetlands, but most of all – improvement in the functioning of the wastewater treatment plant. Restoration is possible, however, protection measures reducing external loading should be undertaken prior to phosphorus inactivation in the water column and in the bottom sediments, supported by biological methods e.g. biomanipulation.

Long-Term Stability of n-Alkane-in-Water Pickering Nanoemulsions: Effect of Aqueous Solubility of Droplet Phase on Ostwald Ripening.

High-pressure microfluidization is used to prepare a series of oil-in-water Pickering nanoemulsions using sterically-stabilized diblock copolymer nanoparticles as the Pickering emulsifier. The droplet phase comprised either n-octane, n-decane, n-dodecane, or n-tetradecane. This series of oils enabled the effect of aqueous solubility on Ostwald ripening to be studied, which is the primary instability mechanism for such nanoemulsions. Analytical centrifugation (LUMiSizer instrument) was used to evaluate the long-term stability of these Pickering nanoemulsions over time scales of weeks/months. This technique enables convenient quantification of the fraction of growing oil droplets and confirmed that using n-octane (aqueous solubility = 0.66 mg dm–3 at 20 °C) leads to instability even over relatively short time periods. However, using n-tetradecane (aqueous solubility = 0.386 μg dm–3 at 20 °C) leads to significantly improved long-term stability with respect to Ostwald ripening, with all droplets remaining below 1 μm diameter after 6 weeks storage at 20 °C. In the case of n-dodecane, the long-term stability of these new copolymer-stabilized Pickering nanoemulsions is significantly better than the silica-stabilized Pickering nanoemulsions reported in the literature by Persson et al. (Colloids Surf., A,2014,459, 48–57). This is attributed to a much greater interfacial yield stress for the former system, as recently described in the literature (see P. J. Betramo et al. Proc. Natl. Acad. Sci. U.S.A.,2017,114, 10373–10378).

Composite anion-exchangers modified with nanoparticles of hydrated oxides of multivalent metals

Organic–inorganic composite ion-exchangers based on anion exchange resins have been obtained. Particles of one-component and two-component modifier were embedded using the approach, which allows us to realize purposeful control of a size of the embedded particles. The approach is based on Ostwald–Freundlich equation, which was adapted to deposition in ion exchange matrix. The equation was obtained experimentally. Hydrated oxides of zirconium and iron were applied to modification, concentration of the reagents were varied. The embedded particles accelerate sorption, the rate of which is fitted by the model equation of chemical reactions of pseudo-second order. When sorption of arsenate ions from very diluted solution (50 µg dm−3) occurs, the composites show higher distribution coefficients comparing with the pristine resin.