Influence of exogenous urea on photosynthetic pigments, 14CO2 uptake, and urease activity in Elodea densa—environmental implications

This paper analyzes the effect of exogenous urea in increased concentration gradient (0, 100, 500 and 1,000 mg L^?1) on photosynthetic pigments (measured spectrophotometrically), uptake of ¹⁴CO₂ (using radioisotope), and urease activity (by measuring ammonia with Nessler’s reagent) in leaves of Elodea densa Planch. We have observed that low concentration of urea (100 mg L^?1) stimulates the accumulation of photosynthetic pigments and intensifies photosynthesis in E. densa, whereas high concentration (1,000 mg L^?1) suppresses these processes. Urease activity increased by approximately 2.7 and 8 fold when exogenous urea concentrations were 100 and 500 mg L^?1, respectively. However, exogenous urea in high concentration (1,000 mg L^?1) decreased urease activity by 1.5 fold compared to the control. The necessity of mitigating urea and other nitrogen-containing compounds (NH₃ from urea) in water bodies has been discussed with emphasis on the potential for phytoremediation of urea using common water weed viz. E. densa.     

Effect of exogenous abscisic acid on the level of antioxidants in Atractylodes macrocephala Koidz under lead stress

This study hypothesized that the positive or negative effects of exogenous abscisic acid (ABA) on oxidative stress caused by lead were dose dependent. The effects of different levels of ABA (2.5, 5, and 10 mg L^?1) on lead toxicity in the leaves of Atractylodes macrocephala were studied by investigating plant growth, soluble sugars, proteins, lipid peroxidation, and antioxidative enzymes. Excess Pb inhibited root dry weight, root length, and the number of lateral roots, but increased shoot growth. In addition, lead stress significantly decreased the levels of chlorophyll pigments, protein, and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD). Different levels of ABA significantly increased SOD, CAT, POD, and APX activities, but decreased the level of hydrogen peroxide and malondialdehyde in nonstressed plants. Exogenous application of 2.5 mg L^?1 ABA detoxified the stress-generated damages caused by Pb and also enhanced plant growth, soluble sugars, proteins, and all four antioxidant enzyme activities but reduced Pb uptake of lead-stressed plant compared to lead treatment alone. However, the toxic effects of Pb were further increased by the applications of 5 and 10 mg L^?1 ABA. The levels of antioxidants caused by a low concentration of exogenous ABA might be responsible for minimizing the Pb-induced toxicity in A. macrocephala.     

Evaluation of Acinetobacter sp. B9 for Cr (VI) resistance and detoxification with potential application in bioremediation of heavy-metals-rich industrial wastewater

Present work demonstrates Cr (VI) detoxification and resistance mechanism of a newly isolated strain (B9) of Acinetobacter sp. Bioremediation potential of the strain B9 is shown by simultaneous removal of major heavy metals including chromium from heavy-metals-rich metal finishing industrial wastewater. Strain B9 tolerate up to 350 mg L^?1 of Cr (VI) and also shows level of tolerance to Ni (II), Zn (II), Pb (II), and Cd (II). The strain was capable of reducing 67 % of initial 7.0 mg L^?1 of Cr (VI) within 24 h of incubation, while in presence of Cu ions 100 % removal of initial 7.0 and 10 mg L^?1 of Cr (VI) was observed with in 24 h. pH in the range of 6.0–8.0 and inoculum size of 2 % (v/v) were determined to be optimum for dichromate reduction. Fourier transform infrared spectroscopy and transmission electron microscopy studies suggested absorption or intracellular accumulation and that might be one of the major mechanisms behind the chromium resistance by strain B9. Scanning electron microscopy showed morphological changes in the strain due to chromium stress. Relevance of the strain for treatment of heavy-metals-rich industrial wastewater resulted in 93.7, 55.4, and 68.94 % removal of initial 30 mg L^?1 Cr (VI), 246 mg L^?1 total Cr, and 51 mg L^?1 Ni, respectively, after 144 h of treatment in a batch mode.     

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation

The objective of this work was to evaluate the efficiency of a solar TiO₂-assisted photocatalytic process on amoxicillin (AMX) degradation, an antibiotic widely used in human and veterinary medicine. Firstly, solar photolysis of AMX was compared with solar photocatalysis in a compound parabolic collectors pilot scale photoreactor to assess the amount of accumulated UV energy in the system (Q _UV) necessary to remove 20 mg L^?1 AMX from aqueous solution and mineralize the intermediary by-products. Another experiment was also carried out to accurately follow the antibacterial activity against Escherichia coli DSM 1103 and Staphylococcus aureus DSM 1104 and mineralization of AMX by tracing the contents of dissolved organic carbon (DOC), low molecular weight carboxylate anions, and inorganic anions. Finally, the influence of individual inorganic ions on AMX photocatalytic degradation efficiency and the involvement of some reactive oxygen species were also assessed. Photolysis was shown to be completely ineffective, while only 3.1 kJ_UV?L^?1 was sufficient to fully degrade 20 mg L^?1 AMX and remove 61 % of initial DOC content in the presence of the photocatalyst and sunlight. In the experiment with an initial AMX concentration of 40 mg L^?1, antibacterial activity of the solution was considerably reduced after elimination of AMX to levels below the respective detection limit. After 11.7 kJ_UV?L^?1, DOC decreased by 71 %; 30 % of the AMX nitrogen was converted into ammonium and all sulfur compounds were converted into sulfate. A large percentage of the remaining DOC was in the form of low molecular weight carboxylic acids. Presence of phosphate ions promoted the removal of AMX from solution, while no sizeable effects on the kinetics were found for other inorganic ions. Although the AMX degradation was mainly attributed to hydroxyl radicals, singlet oxygen also plays an important role in AMX self-photosensitization under UV/visible solar light.     

Utilization of water chestnut for reclamation of water environment and control of cyanobacterial blooms

Overgrowth of water chestnut (Trapa spp.) is a regional problem throughout Asia and North America because of waterway blockage and water fouling upon decomposition. In the present study, we investigated the potential of water chestnut to control cyanobacterial blooms, via a high content of phenolic compounds. In addition, we assessed the impact of biomass harvesting and crude extract application on nutrient balance. We showed that the floating parts of water chestnut contained high concentrations of total phenolics (89.2 mg g^?1 dry weight) and exhibited strong antioxidant activity (1.31 mmol g^?1 dry weight). Methanol-extracted phenolics inhibited growth of Microcystis aeruginosa; the half maximal effective concentration (EC₅₀) of the extracted phenolics was 5.8 mg L^?1, which was obtained from only 103 mg L^?1 of dry biomass (the floating and submerged parts). However, the crude extracts also added important quantities of nitrogen, phosphorus, and potassium (1.49, 1.05, and 16.3 mg g^?1, respectively; extracted dry biomass weight basis); therefore, in practice, nutrient removal before and/or after the extraction is essential. On the other hand, biomass harvesting enables recovery of nitrogen, phosphorus, and potassium from the water environment (23.1, 2.9, and 18.7 mg g^?1, respectively; dry biomass weight basis). Our findings indicate that water chestnut contains high concentrations of phenolics and exhibits strong antioxidant activity. Utilization of these resources, including nutrients, will contribute to reclamation of the water environment, and also to disposal of wet biomass.     

Copper bioaccumulation,photosystem II functioning,and oxidative stress in the seagrass <Emphasis Type="Italic">Cymodocea nodosa</Emphasis> exposed to copper oxide nanoparticles

Photosynthetic activity, oxidative stress, and Cu bioaccumulation in the seagrass Cymodocea nodosa were assessed 4, 12, 24, 48, and 72 h after exposure to two copper oxide nanoparticle (CuO NP) concentrations (5 and 10 mg L^?1). CuO NPs were characterized by scanning electron microscopy (SEM) and dynamic light scattering measurements (DLS). Chlorophyll fluorescence analysis was applied to detect photosystem II (PSII) functionality, while the Cu accumulation kinetics into the leaf blades was fitted to the Michaelis-Menten equation. The uptake kinetics was rapid during the first 4 h of exposure and reached an equilibrium state after 10 h exposure to 10 mg L^?1 and after 27 h to 5 mg L^?1 CuO NPs. As a result, 4-h treatment with 5 mg L^?1 CuO NPs, decreased the quantum yield of PS II photochemistry (Φ _PSΙΙ ) with a parallel increase in the regulated non-photochemical energy loss in PSII (Φ _NPQ ). However, the photoprotective dissipation of excess absorbed light energy as heat, through the process of non-photochemical quenching (NPQ), did not maintain the same fraction of open reaction centers (q _p ) as in control plants. This reduced number of open reaction centers resulted in a significant increase of H₂O₂ production in the leaf veins serving possibly as an antioxidant defense signal. Twenty-four-hour treatment had no significant effect on Φ _PSΙΙ and q _p compared to controls. However, 24 h exposure to 5 mg L^?1 CuO NPs increased the quantum yield of non-regulated energy loss in PSII (Φ _NO ), and thus the formation of singlet oxygen (¹O₂) via the triplet state of chlorophyll, possible because the uptake kinetics had not yet reached the equilibrium state as did 10 mg L^?1. Longer-duration treatment (48 and 72 h) had less effect on the allocation of absorbed light energy at PSII and the fraction of open reaction centers, compared to 4-h treatment, suggesting the function of a stress defense mechanism. The response of C. nodosa leaves to CuO NPs fits the “Threshold for Tolerance Model” with a threshold time (more than 4 h) required for induction of a stress defense mechanism, through H₂O₂ production.     

Solar CPC pilot plant photocatalytic degradation of bisphenol A in waters and wastewaters using suspended and supported-TiO2. Influence of photogenerated species

Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO₂) was performed under different conditions. Suspensions of the TiO₂ were used to compare the degradation efficiency of BPA (20 mg L^?1) in batch and compound parabolic collector (CPC) reactors. A TiO₂ catalyst supported on glass spheres was prepared (sol–gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L^?1). The influence of OH·, O₂ ^·?, and h ⁺ on the BPA degradation were evaluated. The radicals OH· and O₂ ^·? were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO₂ to degrade BPA in batch or CPC reactors was 0.1 g L^?1. According to biological tests, the BPA LC₅₀ in 24 h for E. andrei was of 1.7?×?10^?2 mg cm^?2. The photocatalytic degradation of BPA mediated by TiO₂ supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment.     

Kinetics of imidazolium-based ionic liquids degradation in aqueous solution by Fenton oxidation

In the last few years, several works dealing with Fenton oxidation of ionic liquids (ILs) have proved the capability of this technology for their degradation, achieving complete ILs removal and non-toxic effluents. Nevertheless, very little is known about the kinetics of this process, crucial for its potential application. In this work, the effect of several operating conditions, including reaction temperature (50–90 °C), catalyst load (10–50 mg L^?1 Fe³⁺), initial IL concentration (100–2000 mg L^?1), and hydrogen peroxide dose (10–200% of the stoichiometric amount for the complete IL mineralization) on 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) oxidation has been investigated. Under the optimum operating conditions (T = 90 °C; [Fe³⁺]₀ = 50 mg L^?1; [H₂O₂]₀ = 100% of the stoichiometric amount), the complete removal of [C₄mim]Cl (1000 mg L^?1) was achieved at 1.5-min reaction time. From the experimental results, a potential kinetic model capable to describe the removal of imidazolium-based ILs by Fenton oxidation has been developed. By fitting the proposed model to the experimental data, the orders of the reaction with respect to IL initial concentration, Fe³⁺ amount and H₂O₂ dose were found to be close to 1, with an apparent activation energy of 43.3 kJ mol^?1. The model resulted in a reasonable fit within the wide range of operating conditions tested in this work.     

Evaluation of growth and biochemical indicators of Salvinia natans exposed to zinc oxide nanoparticles and zinc accumulation in plants

The adverse effects of zinc oxide nanoparticles (ZnO NPs) with an average diameter of 25 nm on the aquatic plant Salvinia natans (L.) All. were determined. Growth, superoxide dismutase (SOD) activity, catalase (CAT) activity, peroxidase activity, and chlorophyll content of the plants were measured after 7 days of exposure to different concentrations of ZnO NPs (1 to 50 mg L^?1). The particle distribution in the culture medium (without plants) during the first 24 h was determined using a Nanotrac 250 particle analyzer. We also investigated the zinc accumulation in leaves and roots of the plant after 7 days of exposure. Exposure to 50 mg L^?1 ZnO NPs significantly increased SOD and CAT activities (P?<?0.05) and significantly depressed photosynthetic pigments (P?<?0.05). However, plant growth was not significantly affected (P?>?0.05). NPs completely precipitated at the bottom of the container at 8 h except for the portions of dissolution and aggregation on the roots. ZnO NPs at a concentration of 50 mg L^?1 can adversely affect S. natans, and their stress is affected by their aggregation and dissolution.     

Phosphorus removal in a sulfur–limestone autotrophic denitrification (SLAD) biofilter

The sulfur–limestone autotrophic denitrification (SLAD) biofilter was able to remove phosphorous from wastewater during autotrophic denitrification. Parameters influencing autotrophic denitrification in the SLAD biofilter, such as hydraulic retention time (HRT), influent nitrate (NO₃ ^?), and influent PO₄ ^3? concentrations, had significant effects on P removal. P removal was well correlated with total oxidized nitrogen (TON) removed in the SLAD biofilter; the more TON removed, the more efficient P removal was achieved. When treating the synthetic wastewater containing NO₃ ^?-N of 30 mg L^?1 and PO₄ ^3?-P of 15 mg L^?1, the SLAD biofilter removed phosphorus of 45 % when the HRT was 6 h, in addition with TN removal of nearly 100 %. The optimal phosphorus removal in the SLAD biofilter was around 60 %. For the synthetic wastewater containing a PO₄ ^3?-P concentration of 15 mg L^?1, the main mechanism of phosphorus removal was the formation of calcium phosphate precipitates.     

Toxicity of atrazine and its bioaccumulation and biodegradation in a green microalga,Chlamydomonas mexicana

This study evaluated the toxicity of herbicide atrazine, along with its bioaccumulation and biodegradation in the green microalga Chlamydomonas mexicana. At low concentration (10 μg L^?1), atrazine had no profound effect on the microalga, while higher concentrations (25, 50, and 100 μg L^?1) imposed toxicity, leading to inhibition of cell growth and chlorophyll a accumulation by 22 %, 33 %, and 36 %, and 13 %, 24 %, and 27 %, respectively. Atrazine 96-h EC50 for C. mexicana was estimated to be 33 μg L^?1. Microalga showed a capability to accumulate atrazine in the cell and to biodegrade the cell-accumulated atrazine resulting in 14–36 % atrazine degradation at 10–100 μg L^?1. Increasing atrazine concentration decreased the total fatty acids (from 102 to 75 mg g^?1) and increased the unsaturated fatty acid content in the microalga. Carbohydrate content increased gradually with the increase in atrazine concentration up to 15 %. This study shows that C. mexicana has the capability to degrade atrazine and can be employed for the remediation of atrazine-contaminated streams.     

Impact of treated urban wastewater for reuse in agriculture on crop response and soil ecotoxicity

The scarcity of freshwater resources is a serious problem in arid regions, such as Tunisia, and marginal quality water is gradually being used in agriculture. This study aims to study the impact of treated urban wastewater for reuse in agriculture on the health of soil and food crops. The key findings are that the effluents of Sfax wastewater treatment plant (WWTP) did not meet the relevant guidelines, therefore emitting a range of organic (e.g., up to 90 mg L^?1 COD and 30 mg L^?1 BOD₅) and inorganic pollutants (e.g., up to 0.5 mg L^?1 Cu and 0.1 mg L^?1 Cd) in the receiving aquatic environments. Greenhouse experiments examining the effects of wastewater reuse on food plants such as tomato, lettuce, and radish showed that the treated effluent adversely affected plant growth, photosynthesis, and antioxidant enzyme contents. However, the pollution burden and biological effects on plants were substantially reduced by using a 50 % dilution of treated sewage effluent, suggesting the potential of reusing treated effluent in agriculture so long as appropriate monitoring and control is in place.     

Phytoremediation for co-contaminated soils of chromium and benzo[a]pyrene using Zea mays L.

A greenhouse experiment was carried out to investigate the single effect of benzo[a]pyrene (B[a]P) or chromium (Cr) and the joint effect of Cr–B[a]P on the growth of Zea mays, its uptake and accumulation of Cr, and the dissipation of B[a]P over 60 days. Results showed that single or joint contamination of Cr and B[a]P did not affect the plant growth relative to control treatments. However, the occurrence of B[a]P had an enhancing effect on the accumulation and translocation of Cr. The accumulation of Cr in shoot of plant significantly increased by?≥?79 % in 50 mg kg^?1 Cr–B[a]P (1, 5, and 10 mg kg^?1) treatments and by?≥?86 % in 100 mg kg^?1 Cr–B[a]P (1, 5, and 10 mg kg^?1) treatments relative to control treatments. The presence of plants did not enhance the dissipation of B[a]P in lower (1and 5 mg kg^?1) B[a]P contaminated soils; however, over 60 days of planting Z. mays seemed to enhance the dissipation of B[a]P by over 60 % in 10 mg kg^?1 single contaminated soil and by 28 to 41 % in 10 mg kg^?1B[a]P co-contaminated soil. This suggests that Z. mays might be a useful plant for the remediation of Cr–B[a]P co-contaminated soil.     

Principal component analysis to assess the efficiency and mechanism for enhanced coagulation of natural algae-laden water using a novel dual coagulant system

A novel dual coagulant system of polyaluminum chloride sulfate (PACS) and polydiallyldimethylammonium chloride (PDADMAC) was used to treat natural algae-laden water from Meiliang Gulf, Lake Taihu. PACS (Al_n(OH)_mCl_3n-m-2k(SO₄)_k) has a mass ratio of 10 %, a SO₄ ^2?/Al₃ ⁺ mole ratio of 0.0664, and an OH/Al mole ratio of 2. The PDADMAC ([C₈H₁₆NCl]_m) has a MW which ranges from 5?×?10⁵ to 20?×?10⁵ Da. The variations of contaminants in water samples during treatments were estimated in the form of principal component analysis (PCA) factor scores and conventional variables (turbidity, DOC, etc.). Parallel factor analysis determined four chromophoric dissolved organic matters (CDOM) components, and PCA identified four integrated principle factors. PCA factor 1 had significant correlations with chlorophyll-a (r?=?0.718), protein-like CDOM C1 (0.689), and C2 (0.756). Factor 2 correlated with UV₂₅₄ (0.672), humic-like CDOM component C3 (0.716), and C4 (0.758). Factors 3 and 4 had correlations with NH₃-N (0.748) and T-P (0.769), respectively. The variations of PCA factors scores revealed that PACS contributed less aluminum dissolution than PAC to obtain equivalent removal efficiency of contaminants. This might be due to the high cationic charge and pre-hydrolyzation of PACS. Compared with PACS coagulation (20 mg L^?1), the removal of PCA factors 1, 2, and 4 increased 45, 33, and 12 %, respectively, in combined PACS–PDADMAC treatment (0.8 mg L^?1?+?20 mg L^?1). Since PAC contained more Al (0.053 g/1 g) than PACS (0.028 g/1 g), the results indicated that PACS contributed less Al dissolution into the water to obtain equivalent removal efficiency.     

Effects of bisphenol A on ammonium assimilation in soybean roots

Bisphenol A (BPA), which is ubiquitous in the environment, is an example of an endocrine-disrupting compound (EDC). Ammonium assimilation has an important function in plant growth and development. However, insufficient information on the potential effect of BPA on ammonium assimilation in plants is available. In this study, the effects of BPA on ammonium assimilation in roots of soybean seedlings were investigated. During the stress period, 1.5 mg L^?1 of BPA improved glutamine synthetase (GS)/glutamate synthase (GOGAT) cycle and glutamate dehydrogenase (GDH) pathway in ammonium assimilation. The amino acid and the soluble protein contents increased in the soybeans. At 17.2 and 50.0 mg L^?1 of BPA, the GS/GOGAT cycle was inhibited and the GDH pathway was promoted. The amino acid content increased and the soluble protein content decreased. During the recovery period, the GS/GOGAT cycle and the GDH pathway recovered at 1.5 and 17.2 mg L^?1 of BPA but not at 50.0 mg L^?1 of BPA. The amino acid content continuously increased and the soluble protein content decreased compared with those in the control treatment. In summary, BPA treatment could affect the contents of soluble protein and amino acid in the soybean roots by regulating ammonium assimilation.     

Investigation of chloramine-T impact on crayfish Astacus leptodactylus (Esch., 1823) cardiac activity

The crayfish play an essential role in the biomonitoring and may reflect ambient water quality through the biochemical, behavioural and physiological reactions. To assess whether narrow-clawed crayfish Astacus leptodactylus can respond by heart rate changes to presence in water of such biocide as chloramine-T, adult males were exposed to its low (2 and 5 mg L^?1), moderate (10 mg L^?1, commonly used in industry and aquaculture) and exceeded (20 and 50 mg L^?1) concentrations. In addition, a physical stress test evaluated energy expenditure following the chemical trials. Three key reactions (cardiac initial, first-hour and daily prolonged exposure) were discussed with particular focus on crayfish initial reaction as the most meaningful in on-line water quality biomonitoring. After short-term exposure to both chloramine-T concentrations, crayfish were found to respond rapidly, within 2–5 min. According to heart rate changes, the 1-h exposure did not adversely affect crayfish at either concentration, as well as during daily exposure to 10 mg L^?1. As assessed by the heart rate, the 24-h exposure to 50 mg L^?1 of chloramine-T was toxic for crayfish and led to substantial loss of energy that became apparent during subsequently conducted physical stress. The results supported a hypothesis that crayfish vital functions are connected with environment they inhabit closely enough to serve as biological monitors. Crayfish were tolerant to short-term chloramine-T exposure, while rapid crayfish reaction to an increased chemical level indicated their high sensitivity, an essential attribute of real-time environmental assessment.     

Phytoaccumulation potentials of two biotechnologically propagated ecotypes of Arundo donax in copper-contaminated synthetic wastewater

An in vitro experiment was carried out to evaluate the phytoremediation potentials of two somatic embryo-derived ecotypes of Arundo donax—BL (American ecotype) and 20SZ (Hungarian ecotype)—of copper from synthetic wastewater. The two ecotypes were grown under sterile conditions in tubes containing a nutrient solution supplied with increasing doses of Cu (0, 1, 2, 3, 5, 10, and 26.8 mg L^?1) for 6 weeks. The translocation and bioaccumulation factors and removal rate were estimated. In general, increasing Cu concentration in nutrient solution slightly decreased root, stem and leaf biomass without toxicity symptoms up to 26.8 mg L^?1. Moreover, both ecotypes showed high Cu removal efficiency from aqueous solution. However, Cu removal rate ranged between 96.6 to 98.8 % for BL ecotype and 97 to 100 % for 20SZ ecotype. Data illustrated that both BL and 20SZ ecotypes may be employed to treat Cu-contaminated water bodies up to 26.8 mg L^?1.     

Effect of deposit age on adsorption and desorption behaviors of ammonia nitrogen on municipal solid waste

Ammonia nitrogen pollution control is an urgent issue of landfill. This research aims to select an optimal refuse for ammonia nitrogen removal in landfill from the point of view of adsorption and desorption behavior. MSW (municipal solid waste) samples which deposit ages were in the range of 5 to 15 years (named as R₁₅, R₁₁, R₇, and R₅) were collected from real landfill site. The ammonia nitrogen adsorption behaviors of MSW including equilibrium time, adsorption isotherms, and desorption behaviors including equilibrium time were determined. Furthermore, the effects of pH, OM, Cu(II), Zn(II), and Pb(II) on adsorption and desorption behavior of ammonia nitrogen were conducted by orthogonal experiment. The equilibrium time of ammonia nitrogen adsorption by each tested MSW was very short, i.e., 20 min, whereas desorption process needed 24 h and the ammonia nitrogen released from refuses was much lesser than that adsorbed, i.e., accounted for 3.20 % (R₁₅), 14.32 % (R₁₁), 20.59 % (R₇), and 20.50 % (R₅) of each adsorption quantity, respectively. The maximum adsorption capacity estimated from Langmuir isotherm appeared in R₁₅-KCl, i.e., 25,000 mg kg^?1. The best condition for ammonia nitrogen removal from leachate was pH >7.5, OM 23.58 %, Cu(II) <5 mg L^?1, Zn(II) <10 mg L^?1, and Pb(II) <1 mg L^?1. Ammonia nitrogen in landfill leachate could be quickly and largely absorbed by MSW but slowly and infrequently released. The refuse deposited for 15 years could be a suitable material for ammonia nitrogen removal.     

Australian native plant species Carpobrotus rossii (Haw.) Schwantes shows the potential of cadmium phytoremediation

Many polluted sites are typically characterized by contamination with multiple heavy metals, drought, salinity, and nutrient deficiencies. Here, an Australian native succulent halophytic plant species, Carpobrotus rossii (Haw.) Schwantes (Aizoaceae) was investigated to assess its tolerance and phytoextraction potential of Cd, Zn, and the combination of Cd and Zn, when plants were grown in soils spiked with various concentrations of Cd (20–320 mg kg^?1 Cd), Zn (150–2,400 mg kg^?1 Zn) or Cd + Zn (20?+?150, 40?+?300, 80?+?600 mg kg^?1). The concentration of Cd in plant parts followed the order of roots > stems > leaves, resulting in Cd translocation factor (TF, concentration ratio of shoots to roots) less than one. In contrast, the concentration of Zn was in order of leaves > stems > roots, with a Zn TF greater than one. However, the amount of Cd and Zn were distributed more in leaves than in stems or roots, which was attributed to higher biomass of leaves than stems or roots. The critical value that causes 10 % shoot biomass reduction was 115 μg g^?1 for Cd and 1,300 μg g^?1 for Zn. The shoot Cd uptake per plant increased with increasing Cd addition while shoot Zn uptake peaked at 600 mg kg^?1 Zn addition. The combined addition of Cd and Zn reduced biomass production more than Cd or Zn alone and significantly increased Cd concentration, but did not affect Zn concentration in plant parts. The results suggest that C. rossii is able to hyperaccumulate Cd and can be a promising candidate for phytoextraction of Cd from polluted soils.     

Differences between 4-fluoroaniline degradation and autoinducer release by Acinetobacter sp. TW: implications for operating conditions in bacterial bioaugmentation

To develop a bacterial bioaugmentation system for fluorine-containing industrial wastewater treatment, optimal conditions for 4-fluoroaniline (4-FA) degradation and autoinducer release in Acinetobacter sp. TW were determined. Quorum sensing in biofilms of strain TW was also investigated. Different optimal conditions exist for 4-FA degradation and autoinducer release, particularly with regard to pH. Quorum sensing modulates extracellular polymeric substance (EPS) secretion and biofilm formation in the strain but plays no role in 4-FA degradation. Under optimal conditions for 4-FA degradation, the release of N-3-oxo-hexanoyl-homoserine lactone (3-oxo-C₆-HSL) and N-hexanoyl-homoserine lactone (C₆-HSL) in strain TW was significantly lower than required for quorum sensing. Under optimal conditions for autoinducer release, on the other hand, 3-oxo-C₆-HSL and C₆-HSL levels exceeded the quorum sensing thresholds, thereby inducing EPS secretion and biofilm formation. We conclude that the optimal conditions for autoinducer release (25 °C, pH 5, 800 mg L^?1 4-FA, and 0 % NaCl) are suitable for bacterial colonization in bioaugmentation, while those for 4-FA degradation (25–30 °C, pH 8 and 800 mg L^?1 4-FA) maximize the system performance after colonization.