Po Concentration Research Articles

Mineral profile of some selected citrus fruits collected from different localities of District Sargodha

The present study was conducted to determine the mineral profile of some selected Citrus fruits collected from different localities of district Sargodha i.e. Silanwali, Sargodha, Bhalwal. Plants include Citrus reticulata early mandarin (feutrell’s early), Citrus paradisi (Grapefruit), Citrus reticulata mandarin (Kinnow), Citrus jambhiri (Khatti) and Citrus sinensis (Musambi). Results of the mineral analysis showed that the maximum concentration of Fe (6.52±0.12 mg/100g), Mn (0.98±0.08 mg/100g), Cr (0.46±0.03 mg/100g) and Zn (1.88±0.10 mg/100g) were analyzed in Citrus sinensis collected from Sargodha and Bhalwal respectively while the highest concentration of PO4 (8.10±0.09 mg/100g), Cu (33.59±0.05 mg/100g) and Ca (50.71±0.07 mg/100g) were noted in Citrus jambhiri and Citrus reticulata early mandarin collected from Bhalwal and Silanwali respectively. A highly significant variation in the mineral profile of all selected plants were observed which may be attributed to different environmental factors i.e. soil composition, water, temperature or may be linked to spatial variations. Keywords: Citrus fruits; District Sargodha; Mineral profile; Pakistan http://dx.doi.org/10.19045/bspab.2020.90265

A 2000-year record of phosphorus forms and accumulation in peatland of the Greater Khingan Mountains in Northeast China: Paleoenvironmental implications

To investigate the connection of phosphorus (P) forms with peatland succession and history of fire in Tuqiang peatland, a 57 cm peat core was sampled with high-resolution (1-cm intervals) in the north of the Great Khingan mountain (Northeast China). AMS 14C dating techniques combined with sequential chemical extraction was used to determine and calculate the accumulation rates of phosphorus fractions. Phosphorus forms were mainly composed with NaOH-Po, hot concentrated HCl–P (conc. HCl–P) and residual-P. Active phosphorus pools were enriched in the top 8–10 cm of the peat surface. The concentrations of organic phosphorus forms and residual-P were generally high during 1200 to 500 cal yr BP, and the accumulation rate of that gradually decreased since 1600 cal yr BP. Both of concentration and accumulation of organic phosphorus decreased after 600 cal yr BP. The accumulation rate of organic phosphorus forms significantly corresponded with peat development frequency, pollen records and other paleo evidence. The concentration and accumulation of organic phosphorus, especially NaOH-Po, was positively connected with concentration of pollen and Cyperaceae, and decreased when relative abundance of moss or shrubs occurred. Fire changed the vegetation community, decreased the concentration and accumulation of Po, and reduced inactive Po/Pi at the same time. Fire events could also leave geochemical evidence on peat. It is necessary to consider the both changes of inactive Po/Pi and organic phosphorus accumulation rate when reflected the fire history by phosphorus in core.

Recovery phosphate and ammonium from aqueous solution by the process of electrochemically decomposing dolomite

The cost-effective recovery of phosphate is of great significance to the mitigation of phosphorus resource depletion crisis. The electrochemical-decomposition of dolomite was developed to recover phosphate and ammonium from aqueous solution. The dolomite ore is mainly composed of CaMg(CO3)2 (53.73%), CaCO3 (28.93%) and SiO2 (16.59%). The continuous release of Mg2+ and Ca2+ were achieved by electrochemically decomposing dolomite ore, accompanied by the generation of base solution (9.0–10.5). The main factors affecting the recovery performance of phosphate (PO4–P) and ammonium (NH4–N) are current, initial concentration of PO4–P and NH4–N, initial pH of feed solution and feed rate. For a 30-d operation, the recovery rate of PO4–P was maintained at 90–97% and that of NH4–N at 50–60% under optimized operating conditions. The recovered product had low water solubility but high citric-acid-soluble, and was proposed as a slow-release fertilizer for crops. The proposed process as a simple, effective and green route may serve as a new strategy for recovering PO4–P and NH4–N from wastewaters.

Macro algae based adsorption for treatment of cotton processing wastewater

In the recent advances in treatment of different industrial wastewater, an attempt is made to treat the wastewater produced in demand of dyes and is used to make bandages and surgical cotton using freshwater macro algae. In the treatment method adopted here is focused on reducing the organic and inorganic pollutants present in the wastewater in the form of COD, BOD, Nitrate, Ammonia, Phosphate and Sulphate. Cotton processing wastewater contains high level of tCOD and sCOD in the order of 15000. Initially, Fresh water Green Macro algae is grown in freshwater Bolds Basal Medium (BBM). Tests were conducted with different dilution of Medium, Wastewater and Macro algae. The concentration of COD, NO3, NH4, PO4, and SO4in the real wastewater found to be 4800mg/l, 60.236mg/l, 4.110mg/l, 19.132mg/l, and 2.239mg/l respectively. Finally, after 10 days of continuous treatment of cotton wastewater using macro algae was found to be 1600mg/l, 7.30mg/l, 1.970mg/l, 4.800mg/l, and 1.009mg/l respectively. COD concentration of 1600 mg/l was still not a safe value to be finalized for a safe disposal, it has been observed that due to the high toxicity of the wastewater, macro algae are unable to treat the wastewater further. Solids like Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Fixed Solids (FS) and Total solids (TS) are also noted and studied during the treatment.

A new strategy for determination of trace PO43− using CNDAu as resonance Rayleigh scattering and fluorescence dual-mode probe

The hydrophilic carbon nitride dots (CNDs) and gold-carbon nitride dots (CNDAu) were prepared by microwave digestion instrument with citric acid, thiourea and chloroauric acid as precursors. The morphology and properties of the nanomaterial were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), resonance Rayleigh scattering (RRS), fluorescence (FL), Fourier transform infrared spectrometer (FTIR) and particle size analysis. The acidified ammonium molybdate and CNDs are combined to form complex by intermolecular forces, the system's fluorescence and RRS signals are decreased. After adding PO43−, the ammonium molybdate and PO43− form stable phosphomolybdate heteropoly acid (PMo) with hydrophobic properties, the PMo particles are separated from CNDs, and the released CNDs lead to the increase of FL signal. At the same time, PMo particles are simultaneously aggregate forming large particles, which are manifested by an increase in the RRS signal. We can establish a sensitive, rapid, selective method for the determination of trace PO43− by combining RRS and FL signals. Within a certain range, the signals of the two methods show a linear relationship with the concentration of PO43−. The linear range of dual-mode determination method is 1.4–21 nmol/L PO43−, with a detection limit of 0.60 nmol/L.

Study on the mechanism of the influence of flood storage at the end of the Three Gorges Reservoir on the phosphorus forms in the sediments of the tributary reservoir bay

This paper studies the influence of the impounding process during flood recession in the TGR on the distribution and rerelease of sediment phosphorus forms in the Xiangxi Bay in 2016. Influenced by the main stream of the Three Gorges Reservoir (TGR) flowing backward during impoundment, the water environmental conditions, sediment grain size and sediment-forming environment of the tributary bays change correspondingly. In this study, it is found that the water temperature (WT), turbidity and oxidation–reduction potential (ORP) of the overlying water in the Xiangxi Bay decrease, while the pH increases after impoundment in the TGR. The backward flow of the main stream containing a large amount of sediments increases the sediment content of the tributary bay, and the difference in sediment particle size between the main stream and tributaries narrows after resedimentation. The phosphorus adsorbed on the sediments increases the total phosphorus (TP) in the sediments of the Xiangxi River to 1.3 times its value before water impoundment. NaOH-P and HCl-P in the Xiangxi River sediments account for 42% and 38% of the TP, respectively, and the contents of the various phosphorus forms are ranked in the following order: NaOH-P > HCl-P > organic phosphorus (OP). After impoundment, HCl-P accounts for 67% of the TP, and the relative contents of the phosphorus forms are ranked as: HCl-P > OP > NaOH-P. Orthophosphate (PO43−-P) in the Xiangxi sediments before and after impoundment acts as a source, and the PO43−-P diffusion flux increases from approximately − 0.0029 to 0.0059 mg (m2 d)−1 before impoundment to 0.0067–0.1071 mg (m2 d)−1 after impoundment, which is mainly due to the increased difference in concentration of PO43−-P [ρ(PO43−-P)] between the sediment interstitial water and overlying water after impoundment. After nutrient recharge of the main stream of the Yangtze River, ρ(PO43−-P) of the overlying water is 3.7 times its value before impoundment, and after the release of NaOH-P in the sediments, ρ(PO43−-P) of the interstitial water is 8.3 times its value before water impoundment. Hence, the risk of nutrient release from the sediments in the Xiangxi Bay increases.

Transformation and migration of phosphorus in excess sludge reduction pretreatment by alkaline ferrate oxidation combined with anaerobic digestion

Recently, more and more attention has been paid to the strong oxidation ability of newly prepared potassium ferrate (NAPF) in sludge reduction process, but less attention has been paid to the change of phosphorus in this process. The feasibility of phosphorus migration and transformation during excess sludge reduction pretreatment using NAPF pre-oxidation combined with anaerobic digestion was investigated. After 70 mg/g suspended solids NAPF pretreatment and 16 days anaerobic digestion, the solid-phase volatile suspended solids decreased by 44.2%, and much organic matter had been released into the liquid-phase and then degraded during digestion by indigenous microorganisms. As the sludge pre-oxidation process was performed, solid-phase organic phosphorus and chemically combined phosphorus also released into the liquid-phase as PO43−, peaking at 100 mg/L. During anaerobic digestion, the Fe3+ in the liquid-phase was gradually reduced to Fe2+, and then formed Fe2+-PO43− compound crystals and re-migrated to the solid-phase. The concentration of PO43− decreased to 17.08±1.1 mg/L in the liquid-phase after anaerobic digestion. Finally, the phosphorus in the Fe2+-PO43− compound accounts for 80% of the total phosphorus in the solid-phase. A large number of vivianite crystals in sludge were observed. Therefore, this technology not only effectively reduces sludge, but also increases the proportion of PO43− in the sludge in the form of Vivianite.

Selective colorimetric nano-sensing solution for the determination of phosphate ion in drinking water samples

ABSTRACT A new sensing solution for the colorimetric determination of PO4 3− in drinking water samples was developed. The sensing solution composed of silver nanorods in the absence of PO4 3− ions. Mixing the sensing solution and high concentration of PO4 3− the growth and formation of silver nanorods are suppressed, and the colour of the solution was changed from wine colour to yellow. The wavelength shift of the sensing solution in the presence and absence of PO4 3− was monitored for PO4 3− quantification. Colorimetric determination of PO4 3− revealed the limit of detection (LOD) of 0.076 μM and 0.12 μM in the absence and presence of all interferences, respectively.

Irrigation water quality assessment of Betagi Upazila under Barguna district in Bangladesh

Irrigation water quality is important for the successful crop production. The present study aimed to assess the quality of both ground and surface water for use of irrigation purposes at Betagi Upazila under Barguna district in Bangladesh. Forty two water samples were collected from different locations and their important chemical properties including pH, EC, the concentration of PO43-, SO42-, K+, and Na+ were analyzed. Results revealed that the pH of the ground and surface water were ranged from 7.23 to 8. 49 and 6.98 to 7.96, respectively. Electrical conductivity (EC) of the water samples were 590 to 1950 µ Scm-1 and 110 to 380 µ Scm-1 respectively. The PO43- concentration in groundwater was 0.10 to 0.74 mgL-1 and surface water was 0.05 to 0.20 mgL-1. The SO42- concentration of groundwater ranged from 1.29 to 3.10 mgL-1 and surfacewater was 2.11 to 7.28 mgL-1. The K+ ion concentration was 4.55 to 11.38 mgL-1 in groundwater and 6.12 to 22.44 mgL-1 in surface water. The PO43- and SO42- concentration in most of the ground and surface water samples within the “safe” limit for irrigation, whereas the pH, EC, and K+ concentration in both ground and surface water were not in the safe limit. Besides this, Na+ concentration was higher in groundwater than surface water. Based on chemical properties, surface water is more suitable as irrigation water compared to groundwater in the study area.

Predicting removal kinetics of biochemical oxygen demand (BOD) and nutrients in a pilot scale fed-batch algal wastewater treatment system

Our previous reports have presented single-step treatment of primary-settled urban wastewater by a mixotrophic alga, Galdieria sulphuraria. Here, we present an approach to predict the operational cycle time, t*, required to meet the discharge standards for ammoniacal-nitrogen (NH3-N), phosphate (PO4) and biochemical oxygen demand (BOD) in fed-batch mode, under varying influent concentrations. First order removal rates of NH3-N, PO4 and BOD, determined using data from 10 fed-batch cycles in a pilot scale system (700 L), were used to predict their temporal fate and t* in 30 other cycles. Predicted concentrations of NH3-N, PO4, and BOD and t* over a wide range of influent concentrations agreed well with the measured ones, with root mean square errors, respectively, of 2.06 mg/L, 0.23 mg/L, 2.88 mg/L and 0.30 days. The coefficient of determination between the measured and the predicted values were as follows: for NH3-N: r2 = 0.82, n = 90; for PO4: r2 = 0.87, n = 90; for BOD: r2 = 0.70, n = 30; and for t*: r2 = 0.61, n = 30. The validity of the model in predicting temporal concentration profiles of NH3-N, PO4 and BOD reflected by Janus quotient (respectively of 0.85, 0.87 and 0.61) is comparable to or better than those reported in the literature. Sensitivity analysis procedures identified the influent concentration of PO4 as the most sensitive parameter in predicting t*.

Effects of Exogenous Inputs on Phosphorus Recovery and Transport in Newborn Surface Layers from Sediment Dredging

The effect of external pollution inputs on phosphorus recovery, transport, and transformation in newborn surface layers from sediment dredging remains unclear. Clarifying this issue is important for the control and management of external pollution loads at the watershed scale, particularly after the implementation of sediment dredging activities. In this study, sediments in Meiliang Bay of Lake Taihu were investigated. In-situ dredging simulation was used to study the transport and transformation of phosphorus at the sediment-water interface, before and after dredging, with either external or non-external particulate matter inputs, and to explore the effect of dredging on phosphorus release as part of internal loading. The results showed that limiting the inputs of external particulate matter and dredging had positive impacts on the control of TP and TN in the sediments. Dredging significantly reduced the content of potentially mobile phosphorus (Mobile-P) in surface sediments. Iron-bound phosphorus (Fe-P) was the first main component of the reduced Mobile-P and Organic phosphorus (Org-P) was the second. The content of Loose-bound phosphorus (Lb-P) was less than 1‰ of the total phosphorus. After 210 days of the experiment, the concentration of PO43--P in the pore water of the dredged treatment was lower than that of the undredged treatment, and this difference was more pronounced without external particulate matter input. Furthermore, the concentration of PO43--P in the pore water of the dredged treatment (without external particulate matter input) was maintained at a low level, while this first increased and then subsequently decreased for the other treatments. The concentrations of PO43--P in pore water were positively correlated with Fe-P in the corresponding sediment layers. Source-sink transition took place between winter and spring, leading to the switch in sediment functioning as a sink to a source. The results indicated that dredging could reduce the release rate of internal phosphorus from sediments. Furthermore, limiting the input of external particulate matter plays an important role in facilitating the control of internal phosphorus loading by dredging.

Temporal and Vertical Relations between Various Environmental Factors in the Largest Lake of Łęczna-Włodawa Lake District (Eastern Poland)

Due to global warming and increasing water eutrophication, understanding in-lake relationships is paramount to prevent excessive pollution and further negative changes in lakes. The physico-chemical and biological parameters, as well as nutrient variabilities, both temporal and vertical (in the water column), were studied in the largest Łęczna-Włodawa lake. The study was conducted during two consecutive water years, from November 2015 to September 2017. The non-parametric Kruskal–Wallis ANOVA, test H was used to detect variability between years, and among seasons and lake depths in water temperature, electrical conductivity, pH, ORP, concentration of dissolved oxygen as well as concentration of NO3−, PO43−, TP and chlorophyll a. One-way analysis of variance (ANOVA) was used to detect any differences in Secchi depth (SD) and concentration of NH4+, NO2−, and TN. Ordination techniques: Detrended correspondence analysis (DCA), and Principal Components Analysis (PCA) were used to describe the relationships among 13 environmental variables and distribution of samples. Results showed significant differences (P < 0.05) between two years of the study for most variables except of water temperature, visibility, concentration of PO43−, TN and TP, which corresponded with highly different weather conditions in both years. All of the tested variables, except for nutrients, differed significantly among seasons. Most parameters showed fluctuation in depth, especially in summer and in winter, despite the fact that no hypolimnion or long-lasting thermocline was observed in the study period. However, variability of Chl-a was statistically significant only. The results emphasized complex and multi-directional relations between tested variables, dependent on both external (catchment) and internal (in-lake) processes.

Effect of Pickling and Activation Treatments on the Performance of Electroless Plating of Ni-B Coating on AZ31 Mg Alloy

Pickling is particularly critical before Ni-B electroless plating to create a uniform and catalytically active surface. In the present work, pickling treatment of AZ31 Mg alloy was performed in phosphoric acid followed by immersion in 40% HF. The effect of concentration of both H 3 PO 4 and HF as well as the effect of time were investigated. The pickled samples were then electroless plated with a Ni-B composite. The performance of the Ni-B composite coating was investigated under the SEM.Results show that the highest quality coating was obtained upon pickling AZ31 Mg alloy samples in 50% phosphoric acid for 1 min, followed by activation in 40% HF for 15 min. Higher concentration of H 3 PO 4 results in a higher concentration of PO 3 − 4 , leading to a higher tendency to produce insoluble films (mainly Mg 3 (PO 4 ) 2 and AlPO 4 ) on the substrate surface slowing down the rate of Mg alloy oxidization and dissolution. Activation of pickled AZ31 Mg samples in HF results in the formation of corrosion resistant dense layer of magnesium fluoride. SEM investigation predicted the electroless deposition of an adherent compact layer of Ni–B composite coating on the H 3 PO 4 /HF pickled AZ31 samples. Key Words: AZ31 Mg alloy, pickling, activation, HF, electroless plating DOI : 10.7176/CMR/11-5-04 Publication date :May 31 st 2019

210Po in Pacific Salmon from the West Coast of Canada and its Contribution to Dose by Ingestion.

In response to public concern in Canada regarding health impacts attributable to the Fukushima Daiichi nuclear accident, oceanic seawater samples from the north Pacific and Arctic oceans, coastal seawater samples from 16 locations along the British Columbia coastline, and seafood samples (salmon, steelhead trout, and shellfish) from British Columbia coastal waters were collected and analyzed. This paper reports radiological analysis results of Pacific salmon samples (Oncorhynchus species) obtained from summer 2013 to fall 2016. While radioactive cesium from the Fukushima disaster was not detectable in most salmon samples, naturally occurring Po was measured in almost all individual samples in varying activity concentrations, from below the detection limit of 0.2 Bq kg fresh weight up to 4.7 Bq kg fresh weight. The average Po concentration among 297 salmon samples was 0.73 Bq kg fresh weight. The average ingested radiation dose per kilogram of salmon from Po is estimated to be 0.88 μSv, and the average dose from Cs is estimated to be 0.0026 μSv. The annual dose from ingested salmon would be only a fraction of the worldwide average annual effective dose from exposure to natural background radiation (2,400 μSv y) (). The measurement results showed clearly that radiation doses to people consuming fish (such as salmon) from the Canadian west coast pose no health concern.

Molecular analyses of bacterioplankton communities with highly abundant Vibrio clades: a case study in Bohai Sea coastal waters

We investigated the bacterioplankton abundance, community composition and the associated Vibrio clades of natural seawater in Bohai Sea coastal waters. Seawater samples (10 L in triplicate) were collected at 0.5, 3, and 5 m depths near the coastal aquaculture zone of the Bohai Sea on May 12, 2016. Real-time PCR and 16S rRNA gene amplicon high-throughput sequencing methods were employed by which 485 operational taxonomic units (OTUs) at a 97% sequence similarity level were generated. Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes were the most abundant groups, accounting for 49.5%, 23.5%, and 18.9% of the total assemblage, respectively. Obvious variations in Pseudoalteromonas, Vibrio, and Octadecabacter, which were the most abundant genera, could be observed among different samples. Notably, the results of Vibrio-specific real-time PCR indicated that Vibrio had extremely high 16S rRNA gene copy numbers. The 16S rRNA gene sequencing results across all the samples also indicated that they occupied a large proportion of the total assemblage. Both the alpha diversity and major bacterioplankton group Pseudoalteromonas had significant correlations with the concentration of PO 4 3− . Overall, studies on bacterioplankton communities with highly abundant Vibrio clades can provide interesting insight into the microbial function and health assessment of the Bohai Sea coastal ecosystem.

Phosphorus speciation and dynamics in river sediments, floodplain soils and leaf litter from the Lower Murray River region

Phosphorus (P) availability, which depends on both P concentration and speciation, often controls primary productivity and algal-bloom formation in river systems. The river P pool is also connected to P pools of adjacent sediments, soils and vegetation. Thus, informed management of P in floodplain–river systems requires detailed understanding of P concentration and speciation in all of these interconnected components. We studied P speciation in river sediments and water, floodplain soils and river red gum (Eucalyptus camaldulensis) leaf litter from the Lower Murray region using conventional spectroscopic measurements, solution 31P nuclear magnetic resonance (31P NMR) spectroscopy, and leaching experiments to simulate floodplain re-wetting of leaf litter. Almost all (>85%) of the P in river sediments was in the orthophosphate form, whereas floodplain soils had higher proportions of organic P (PO) species. Both fresh and senescent river red gum leaf litter also had a much higher concentration of PO, primarily in the form of phytate. On submersion, there was a rapid (0–96h) loss of dissolved P from senescent leaves; release of dissolved organic carbon showed similar kinetics. Loss of P from the leaves included both organic and inorganic forms. The results have important implications for aquatic primary productivity and environmental management strategies.

Preparation, characterization, release and antioxidant activity of curcumin-loaded amorphous calcium phosphate nanoparticles

In the study, amorphous calcium phosphate (ACP) nanoparticles were prepared by the coprecipitation method to optimize release profile of curcumin (Cur) and avoid burst releases, which were used to overcome the weakness of Cur, such as poor chemical stability and bioavailability. To find the best preparation condition, the influence of reaction concentration, temperature, time and pH on crystal phase of the samples was investigated by XRD and FTIR. The results showed that amorphous calcium phosphate (ACP) was obtained, when pH value and the concentration of PO43− were 8 and 0.024 mM, prepared at 30 °C for 10 min. In vitro drug release assay, ACP nanoparticles showed high loading capacity of Cur and favorable pH-responsive drug release properties. Furthermore, the Cur-load ACP nanoparticles showed an excellent ability to scavenge free radical and damage A549 cells, resulting in a high antioxidant properties and low cell viability. Therefore, the as-prepared nanoparticles have promising applications in the food and biomedical fields.

The ethanol extract of honeysuckle stem modulates the innate immunity of Chinese mitten crab Eriocheir sinensis against Aeromonas hydrophila

Honeysuckle stem had been used as feed additives to modulate immunity in breeding industry, which was limited in the aquaculture field. In this study, the immunomodulation of honeysuckle stem ethanol extract (designed as HSE) on Chinese mitten crab Eriocheir sinensis was detected. The crabs fed with HSE diets for 30 days had higher level of the total haemocyte count (HTC), lysozyme activity and PO activity (P < 0.05), and had no obvious affect on the phagocytic activity, NO and TNF-α level. When challenged with Aeromonas hydrophila (1.0 × 107 colony-forming units), HSE exhibited weak antibacterial activity against A. hydrophila and increased survival rate of crabs. The decreasing of THC and the increasing of TNF-α concentration, EsCaspase and EsLITAF mRNA expression level were all inhibited significantly by HSE treatment (P < 0.05), when the crabs were challenged by A. hydrophila. Moreover, the following immune parameters of crabs were enhanced by HSE treatment after A. hydrophila infection, including the rising of phagocytosis index and phagocytic rate of haemocyte, the rising of lysozyme, PO, NOS activities and nitric oxide concentration (P < 0.05). Therefore, it was concluded that HSE had great potential to develop into feed additive of crabs, which could enhance the innate immunity of Chinese mitten crabs E. sinensis effectively after A. hydrophila infection.

Hydrophobic and hierarchical modification of TS-1 and application for propylene epoxidation

Hierarchical and hydrophobic TS-1 was obtained by the desilication and silanization of TS-1. The modified TS-1 was characterized by adsorption–desorption isotherms analysis, transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and contact angle measurement. It demonstrates that modified TS-1 has hierarchical channel structures consisting of micropores and mesopores. The average pore diameters of the micropores and mesopores are 0.55 and 5–10 nm, respectively. The contact angle measurements indicate that modified TS-1 is hydrophobic. The effects of the desilication and silanization of TS-1 on the catalyst structure and catalytic properties of propylene epoxidation were investigated. Modified TS-1 showed better catalytic activity and catalytic life than the TS-1 without modification. The H2O2 conversion, PO selectivity and PO concentration reached 99.72%, 91.33% and 0.85 mol L−1, respectively.

Time dependent electrical resistivity tomography and seasonal variation assessment of groundwater around the Olushosun dumpsite Lagos, South-west, Nigeria

Time-lapse electrical resistivity tomography (ERT) and seasonal variation studies of the physicochemical properties of groundwater were carried out on the Olushosun dumpsite in Lagos South-western Nigeria, to monitor, track the depth of leachate contamination, and to investigate the impact of seasonal variation on groundwater quality around the dumpsite. Six 2-D resistivity imaging lines were investigated. The independent inversion of the dipole–dipole and pole-dipole resistivity data indicated that contaminated zones are characterised by resistivity values ranging from 0.63 to 12.5 Ωm, and a maximum depth of 141 m was investigated. The pole-dipole models show clear evidence of vertical migration of contaminant with time, as depth of contamination increased from 106 m in May 2014 to about 120 m in December 2015 around the investigated portion of the dumpsite. Analysis of the seasonal variation of the examined physicochemical properties of the water samples taken from wells and boreholes within and around the site showed that there is increase in concentration of TDS and EC in the dry season study and a corresponding increase in the mean concentration of pH, Ca, Mg, hardness, Cu, Cr, NO3, SO4 and Na from the dry season results. Also, there is reduction in the mean concentration of Fe, Zn, Mn, PO4, Cl, and Ni in the dry season when compared with the wet season analysis. Generally, there is a strong correlation between the ERT results and the physicochemical parameters of ground water quality viz-a-viz the contamination status of the Olushosun dumpsite. This increased trend in the dry season period could be attributed to the increase in concentration of the dissolved metals due to evaporation, and on the other hand, dilution effect of the rainfall during the wet season. South East direction of contaminant flow was established from the water table contour lines produced for the area. The research has clearly shown that the groundwater within the study area has been impacted by the leachate from the decomposed refuse at the dumpsite and may constitute danger to the life of residents living around the dumpsite.