Mixture Of HNO3 Research Articles

Fabrication of Buried Microchannels with Almost Circular Cross-Section Using HNA Wet Etching

In this paper, a novel fabrication process for the realization of large, suspended microfluidic channels is presented. The method is based on Buried Channel Technology and uses a mixture of HF, HNO3, and water etchant, which has high selectivity between the silicon substrate and the silicon-rich silicon nitride mask material. Metal electrodes for actuation and read-out are integrated into the fabrication process. The microfluidic channels are released from the silicon substrate to allow the vibrational movement needed for the application. The resulting microfluidic channels have a near-circular cross-section, with a diameter up to 300 μm and a channel wall thickness of 1.5 μm. The structure of a micro-Coriolis mass-flow and density sensor is fabricated with this process as an example of a possible application.

Preparation of nano SnO2-Sb2O3 composite electrode by cathodic deposition for the elimination of phenol by Sonoelectrochemical oxidation

Abstract The preparation of composite metal oxide to attain high efficiency in removing phenol from wastewater has a great concern. In the present study, the focus would be on adopting antimony-tin oxide coating onto graphite substrates instead of titanium; besides the effect of SbCl3 concentration on the SnO2-Sb2O3 composite would be examined. The performance of this composite electrode as the working electrode in the removal of phenol by sonoelectrochemical oxidation will be studied. The antimony-tin dioxide composite electrode was prepared by cathodic deposition with SnCl2 . 2H2O solution in a mixture of HNO3 and NaNO3, with different concentrations of SbCl3. The SnO2-Sb2O3 deposit layer’s structure and morphology were examined and the 4 g/l SbCl3 gave the more crystallized with nanoscale electrodeposition. The highest removal of phenol was 100% at a temperature of 30 oC, with a current density (CD) of 25 mA/cm2.

Structural Analysis and Electrical Property of Acid‐Treated MWCNT

ABSTRACTThe electrical properties of acid‐treated CNT were investigated in terms of functional group and microstructure. A mixture of HNO3 and H2SO4 was used to acid treatment of CNT, and acid‐treated CNTs were synthesized by the mixture for 0 to 5 h. In crystal structure analysis, as acid treatment time was increased, the intensity of graphite diffraction peak was decreased and shifted to lower angle. It indicates a decrease in the crystallinity of CNT surface and lattice contraction by loss of carbon atoms. The distribution of oxygen on CNT surface was observed by TEM analysis confirming that functional groups and structural defects were formed. ID/IG ratio and average distance between defects (LD) were calculated using Raman spectroscopy to analyze the structural characteristics of CNT, and the greatest decrease was identified from p‐CNT to 2h‐CNT, resulting in the formation of functional groups and the changes in structural defects on CNT surface by acid treatment in the initial stage. Bonding state on CNT surface was analyzed through XPS analysis, and functional groups such as CO and COH were confirmed in acid‐treated CNT. Sheet resistance was measured to analyze the electrical properties of CNT, and 3h‐CNT showed the lowest sheet resistance at 25.28 Ω.

Separation trace amounts of copper ion by solid-phase extraction with carbon-based sorbent prior to flame atomic absorption spectrometry

ABSTRACT In this research, a carbon adsorbent modified with curcumin ligand was utilised in the solid-phase extraction procedure. This method was coupled with flame atomic absorption spectrometry to pre-concentrate and separate trace amounts of copper ions in aqueous solutions. Different experimental parameters, including pH, eluent type and concentration, adsorbent dose, extraction time and sample volume, were studied and optimised. The obtained optimum conditions for the proposed method were: pH of solution, 4.8; extraction time, 9 min; adsorbent dose, 0.01 g; type and concentration of eluent, 1:1 mixture of HCl and HNO3 0.5 mol L−1. Under optimal conditions, the pre-concentration factor of 400.0 and linear range values of the method were 0.031–1.875 µg/L and 12.5–750 µg/L for copper ions in the initial and final solutions, respectively. The relative standard deviation (RSD) for seven replicate detections of 0.05 µg L−1 of copper ion in initial solution was calculated as 2.2%. Furthermore, the detection limit of 0.008 µg L−1 was determined for the suggested method. In order to investigate the selectivity of modified carbon adsorbent, the influence of some interfering ions on the extraction and recovery of Cu (II) was studied. Finally, the present method was employed for the determination of copper ions in real water samples and standard alloys.

Evaluation of Heavy Metals in Roadside Soil of Tumfure Main Market, Gombe State

Heavy metal pollution has been a problem of concern in soil ecology in recent decades. This study evaluated the physico-chemical characteristics and heavy metal contents in roadside soil samples of Tumfure main market, Gombe, Nigeria. The soil samples were collected from six different sampling points with a control sample each by handpicking, this was followed by oven-drying, ground to fine grain, and then sieved using a 2 mm mesh sieve. The pH, electrical conductivity and bulk density were carried out on the soil samples, sieve and sedimentation method were used to determine the soil texture. The soil samples were weighed and digested using mixture of HCl and HNO3. The contents (mg/kg) of four metals (cadmium, copper, lead and zinc) were estimated using Atomic Absorption Spectrophotometer (AAS). Among the metals analyzed, the contents of Cd, Cu and Pb were not detected while the content of Zn (23.454 - 36.026) was found to be within the desirable permissible limits by the World Health Organization (WHO) and European Regulatory Standards (EURS) whose prevalence is to be considered non-toxic in unpolluted soils.

Recovery of Rare Earth Elements from Coal Fly and Bottom Ashes by Ultrasonic Roasting Followed by Microwave Leaching

Considering the rising demand for rare earth elements (REEs), researchers are looking for new sources for their extraction, thereby fostering economic and environmentally justified processing solutions. Among potential industrial sources, coal fly ash emerges as one of the most promising. The recovery of REEs from coal fly and bottom ashes derived from different thermal power plants was the main focus of this study. A dual-step methodology was conducted on ash samples, which involved an ultrasonic roasting process to disintegrate the silica matrix, followed by a microwave-assisted acid leaching step to extract REEs. The roasting procedure was studied using the Plackett–Burman design, and the Box–Behnken design was subsequently implemented to optimize the leaching procedure. The optimized ultrasonic roasting procedure was set up at 95 °C for 10 min with an ash-to-roasting agent (3M NaOH) ratio of 0.5:1 (m/V). For acid leaching, the optimal conditions were obtained at 174 °C for 30 min with an HCl ÷ HNO3 mixture (1:1 V/V). The standard reference material (NIST 1633c) was used in the conclusive experiments to estimate the average recovery (80%) of REEs. The green aspects of this methodology were evaluated using several metrics (atom economy, E-factor, and energy consumption). The proposed process outperforms high-temperature roasting procedures in terms of greenness; however, the REE recovery rate is lower.

ZAWARTOŚĆ SELENU W GONADACH SAMCÓW I SAMIC DZIKA EUROAZJATYCKIEGO (SUS SCROFA) Z WOJEWÓDZTWA MAZOWIECKIEGO

Selenium is counted among the trace elements necessary to maintain metabolic processes occurring in the animal body, including reproductive processes. The aim of the study was to assess selenium content in testes and ovaries of wild boars (Sus scrofa) in an attempt to establish a range of reference values for individuals of this species. Selenium concentrations in tissues tested were determined using spectrofluorometric method after wet mineralization in HNO3 and HClO4 mixture. Based on the results, it was found that male wild boars accumulated significantly higher concentrations of Se than females. The average content of this element in the testes of wild boars was 0.32 mg · kg−1 while in the ovaries it was at the level of 0.14 mg · kg−1 wet weight. In addition, the gonads of males were characterized by a higher variability of the analyzed parameter in relation to samples obtained from female wild boars. The coefficient of variation in their case was almost 40.9, while the value of the coefficient of variation for selenium content in the parenchymal layer of the ovaries was 24.9. On the basis of statistical analysis, highly significant differences were found at p ≤ 0.01 according to the sex of the individuals studied. Despite the fact that samples were taken from individuals living in areas with selenium deficiencies due to the biogeochemical background, it should be considered that the supply of Se is optimal, which is evident in the population growth dynamics of individuals of this species in the study area.

Proximate analysis, levels of trace heavy metals and associated human health risk assessments of Ethiopian white sugars

In this study, white sugar samples collected from five Ethiopian sugar manufacturing plants were analyzed for their proximate composition, and trace heavy metals level (Fe, Co, Ni, Mn, Zn, Cr, Cd, and Pb). Human health risk assessments associated with heavy metals exposure from white sugar ingestion were also assessed. Proximate analysis was conducted according to AOAC methods. For heavy metals determination, the sugar samples were digested using a mixture of HNO3, HClO4 and H2O2 (4:3:1) at 250 °C for 3 h prior to FAAS analysis. The measured mean values (%) of proximate parameters including moisture, ash, fiber, protein, fat and carbohydrate were found in the range of 0.07–0.61, 2.56–4.33, 0.06–0.24, 0.78–1.49, 1.16–1.89 and 92.13–95.03, respectively. The average concentration of heavy metals found in the sugar samples were ranged as 1.366–12.502, 0.107–0.268, 0.099–0.842, 0.458–1.000, 10.140–25.480, 0.053–0.322, 0.427–0.827 and 0.074–0.528 in mg/kg for Fe, Mn, Ni, Co, Zn, Cr, Cd and Pb, respectively. All the studied metals are below FAO/WHO permissible limit except Cd and Pb in Kessem, Fincha'a and Metahara samples. The target hazard quotient (THQ) and hazard index (HI) values are <1, indicating no non-carcinogenic risks of the heavy metals to an adult population via consumption of white sugar. However, the single element incremental lifetime cancer risk (ILCR) occurrence is probable from Ni for samples obtained from Kessem sugar factory (ILCR>1.0 × 10−4). The cumulative ILCR of heavy metals (Ni, Cr, Cd and Pb) resulting from consumption of white sugar by an adult person reveal a potential adverse cancer risk (ILCR>1.0 × 10−4) for all the studied samples except for sugar samples obtained from Wonji sugar factory. Therefore, continuous monitoring of these toxic metals should be made mainly by sugar industries and responsible government regulatory bodies to avert heavy metal toxicity associated with white sugar consumption in Ethiopia.

Efficient Removal of Hazardous P-Nitroaniline from Wastewater by Using Surface-Activated and Modified Multiwalled Carbon Nanotubes with Mesostructure.

P-nitroaniline (PNA) is an aniline compound with high toxicity and can cause serious harm to aquatic animals and plants. Multiwalled carbon nanotubes (MWCNTs) are a multifunctional carbon-based material that can be applied in energy storage and biochemistry applications and semiconductors as well as for various environmental purposes. In the present study, MWCNTs (CO2-MWCNTs and KOH-MWCNTs) were obtained through CO2 and KOH activation. ACID-MWCNTs were obtained through surface treatment with an H2SO4-HNO3 mixture. Herein, we report, for the first time, the various MWCNTs that were employed as nanoadsorbents to remove PNA from aqueous solution. The MWCNTs had nanowire-like features and different tube lengths. The nanotubular structures were not destroyed after being activated. The KOH-MWCNTs, CO2-MWCNTs, and ACID-MWCNTs had surface areas of 487, 484, and 80 m2/g, respectively, and pore volumes of 1.432, 1.321, and 0.871 cm3/g, respectively. The activated MWCNTs contained C-O functional groups, which facilitate PNA adsorption. To determine the maximum adsorption capacity of the MWCNTs, the influences of several adsorption factors-contact time, solution pH, stirring speed, and amount of adsorbent-on PNA adsorption were investigated. The KOH-MWCNTs had the highest adsorption capacity, followed by the CO2-MWCNTs, pristine MWCNTs, and ACID-MWCNTs. The KOH-MWCNTs exhibited rapid PNA adsorption (>85% within the first 5 min) and high adsorption capacity (171.3 mg/g). Adsorption isotherms and kinetics models were employed to investigate the adsorption mechanism. The results of reutilization experiments revealed that the MWCNTs retained high adsorption capacity after five cycles. The surface-activated and modified MWCNTs synthesized in this study can effectively remove hazardous pollutants from wastewater and may have additional uses.

Validation of microwave acid digestion, diffusive gradients in thin-film preconcentration and inductively coupled plasma optical emission spectrometry methodology for the determination of REEs in natural zeolites.

The determination of rare earth element (REE) content in different natural minerals is of high interest due to their extensive use in modern and sustainable technologies. The REEs occurring in natural zeolites are specific to each deposit. This study presents the validation and evaluation of the measurement uncertainty for the determination of REEs (Ce, Dy, Er, Eu, Gd, La, Lu, Nd, Pr, Sm, Y, and Yb) in natural zeolites using microwave-assisted acid digestion and inductively coupled plasma optical emission spectrometry (ICP-OES) after diffusive gradients in thin-film preconcentration. A mixture of HNO3 : HCl : HF of 3 : 9 : 2 (v/v/v) and microwave digestion provided suitable recoveries for the analysis of two certified reference materials, CRM BCS-CRM 375/1 and CRM OREAS 460. Good linearity over the calibration range of 0-2 μg mL-1, with correlation coefficients of 0.9995-1.0000, was obtained for each REE by ICP-OES. The limits of quantification (LOQS), calculated considering the instrumental LOQs and the sample preparation by microwave digestion, were in the range of 0.20-0.60 mg kg-1. A supplementary step of preconcentration/matrix separation based on the passive sampling by diffusive gradients in thin-films (DGT) technique improved the LOQs by about 20 times after three days of passive accumulation, allowing the measurement of the concentrations of all studied REEs in natural zeolite samples. The proposed methodology is a suitable approach for the measurement of REEs at low concentrations in natural zeolite samples by ICP-OES, and it can be extended to other geological samples. The measurement uncertainty was calculated based on the validation data. The proposed method provides reliable results for the measurement of REEs in natural zeolites and was used to measure the specific concentrations of REEs in natural zeolite samples from three Romanian quarries. The REE concentration can be used as a fingerprint for each deposit.

A resins-neutralization coupled route for the treatment of stainless-steel pickling effluent: A research study

One of the major environmental problems caused by stainless-steel industries is the liquid effluents generated during the production processes. It contains a high concentration of metal ions such as Fe (III), Cr (III), Cr (VI), and Ni (II) in HF and HNO3 mixture, oil, and rinse wastewater. The used pickling waste stream has a pH of 0.5 and Total Dissolved Salts (TDS) of 520g/L with a density of 1.20g/CC. The present work focused on recycling pickling effluent by combining filtration, resins, and neutralization to remove metal ions efficiently and F- greater than 99.5%. To remove TDS, laboratory experiments were performed using micro and ultra-filters with a membrane area 0.2m2. Cr (VI) was removed using TulsionFSMP 6301 resin and desorption using NaNO3 and subsequent conversion into Na2Cr2O7 as a by-product. For neutralization, Ca(OH)2 and NaOH were used to precipitate metal ions, and the resulting filtrate was polished using ZrOCl2 to remove F- to 0.12 mg/L effectively. The nitrate was recovered as NaNO3. Adsorption isotherm and kinetic studies were utilized for Cr (VI) from experimental data, and a process flow diagram was developed, which can eventually be tested on a larger scale.

Determination of technology-critical elements in seafood reference materials by inductively coupled plasma-tandem mass spectrometry

The certified reference materials (CRMs) BCR-668 (mussel tissue), NCS ZC73034 (prawn), NIST SRM 1566a (oyster tissue) and NIST SRM 2976 (mussel tissue) were analyzed for their mass fractions of 23 elements using inductively coupled plasma tandem-mass spectrometry (ICP-MS/MS). This study focused on the quantification of selected technology-critical elements (TCEs), specifically rare earth elements (REE) and the less studied TCEs Ga, Ge, Nb, In and Ta. Microwave assisted closed vessel digestion using an acid mixture of HNO3, HCl and H2O2 was applied to varying sample masses and two different microwave systems. Recoveries of 76% (Gd, NCS ZC73034) to 129% (Lu, BCR-668) were obtained for the REE and 83% (Ge, NCS ZC73034) to 127% (Nb, NCS ZC73034) for the less studied TCEs across all analyzed CRMs (compared to certified values) using the best-performing parameters. Mass fractions for all analyzed, non-certified elements are suggested and given with a combined uncertainty U (k = 2), including mass fractions for Ga (11 µg kg-1 ± 9 µg kg-1 to 67 µg kg-1 ± 8 µg kg-1) and In (0.4 µg kg-1 ± 0.3 µg kg-1 to 0.8 µg kg-1 ± 0.7 µg kg-1). This study provides mass fractions of possible new emerging contaminants and addresses the relevant challenges in quantification of less studied TCEs, thus allowing the application of existing CRMs for method validation in studies dealing with the determination of TCEs in seafood or other biota.Graphical abstract

Synthesis of a Molybdenum-Containing Mo2C/C Composite Material with Functionalized Carbon Nanotubes

The Mo2C/C composite material was synthesized by the sol-gel method using molybdenum blue dispersions. Carbon nanotubes treated with HCl (acid treatment) and a mixture of H2SO4 and HNO3 (liquid-phase oxidation) were used as the carbon support. Samples of finished supports and composites were characterized by X-ray phase analysis, transmission electron microscopy, infrared spectroscopy, and low temperature nitrogen adsorption to determine phase composition, surface morphology, and porous parameters. It was established that the content of molybdenum carbide in a composite material is affected by the electrical surface properties of carbon nanotubes and molybdenum blue nanoparticles.

ZAWARTOŚĆ SELENU W JAJNIKACH WOLNO ŻYJĄCYCH CERVIDAE Z TERENU PÓŁNOCNO-WSCHODNIEJ POLSKI

Selenium is counted among the trace elements necessary for the maintenance of metabolic processes occurring in the animal body, including the proper functioning of the reproductive system. The aim of the study conducted was to analyze the selenium content in the ovaries of red deer (Cervus elaphus) and European roe deer (Capreolus capreolus) in an attempt to establish a range of reference values for individuals of these species. Selenium concentrations in tissues tested were determined using spectrofluorometric method after wet mineralization in HNO3 and HClO4 mixture. Ovaries Se concentrations ranged from 0.034–0.338 mg⋅kg−1 wet weight and 0.015–0.285 mg⋅kg−1 wet weight in roe deer and red deer respectively. Based on the results, it was found that the average selenium content was higher in the ovaries of red deer and was 0.11 while in roe deer it was 0.09 mg⋅kg−1 wet weight. The gonads of European roe deer were characterized by higher variability of the analyzed pa- rameter in relation to samples obtained from female red deer. The coefficient of variation in their case was almost 90.1, while the value of the coefficient of variation for selenium content in the parenchymal layer of ovaries in red deer was almost 67.6.

Titanium Dioxide/Graphene Oxide Composite Coatings for 316 Stainless Steel Dental Implants.

Stainless steel has been used in orthopedics and orthodontic fields. However, it cannot be used for fabrication of dental implants due to its inertness, low biocompatibility and weak resistance to corrosion. A composite coating of titanium oxide /graphene oxide has been prepared for stainless steel to improve its biological properties. Stainless steel discs were polished, cleaned and pre-treated with a mixture of HNO3 and HF acid for 15 min. The composite coating composed of TiO2 produced by sol-gel technique and doped with 0.75 wt% graphene oxide. XRD, SEM-EDX and AFM were employed to characterize the composite coating. The anti-bacterial action of the composite coating was investigated against S. aureus and E. coli. The corrosion resistance of coated and noncoated samples was assessed in SBF using electrochemical technique. Cytotoxicity was assessed using osteoblast-like cells. The wettability was determined by contact angle, and bioactivity assessed by immersion in SBF. The results revealed that the composite coating was dense with few micro-cracks, and was not cytotoxic to osteoblast-like cells. The composite coating reduced bacterial colonies and the corrosion rate of the steel was improved. The wettability of the sample was increased with the composite coating and apatite formation appeared after 21 days.

Sulfur impurity removal in magnesium aluminate spinel by acid treatment

MgAl2O4 is a versatile and stable oxide that is useful in various applications. However, the presence of impurities originating as a part of the powder synthesis process can potentially impair desired properties. In this work, we performed acidic treatments with mixtures of HNO3 and H2SO4 on commercial MgAl2O4 nanopowders. The treated powder structure and morphology was found to be largely retained, while changes in specific surface area, adsorbed CO2, and sulfur content were detected. Two sulfur species populations were identified (i.e., S2+ and S6+) and their concentration throughout the surface and bulk of the particles was analyzed. Notably, S2+ was beforehand unknown as a contaminant in MgAl2O4. The S2+ concentration could be diminished below detection limit of XPS by increasing the percentage of H2SO4. The insights gained on sulfur impurities present in commercial nanopowders and their removal possibilities or limitations can help utilize such oxides in applications sensitive to chemical purity.

Development and evaluation of thiosalicylic-modified/ion-imprinted chitosan for selective removal of cerium (III) ion

Chitosan was used in this study as the bio-based product for the development of microparticles for the specifically targeted removal of cerium ions (Ce3+) by ion-imprinting technology. A thiosalicylic hydrazide-modified chitosan (TSCS) is produced via cyanoacetylation of chitosan, followed by hydrazidine derivatization to finally introduce the thiosalicylate chelating units. Ion-imprinted Ce-TSCS sorbent microparticles were prepared by combining the synthesized TSCS with Ce3+, crosslinking the polymeric Ce3+/TSCS complex with glutaraldehyde, and releasing the chelated Ce3+ using an eluent solution containing a mixture of EDTA and HNO3. Ce-TSCS had a capacity of 164 ± 1 mg/g and better removal selectivity for Ce3+ because it was smart enough to figure out which target ions would fit into the holes made by Ce3+ during the imprinting process. The kinetic data were well suited to a pseudo-second-order model, and the isotherms were well described by the Langmuir model, both of which pointed to chemisorption and adsorption through Ce3+ chelation. XPS and FTIR analyses demonstrate that the predominant adsorption mechanism is the coordination of Ce3+ with the -NH-, -NH2, and -SH chelating units of the thiosalicylic hydrazidine. These findings provide fresh direction for the development of sorbent materials that can effectively and selectively remove Ce3+ from aqueous effluents.

Fabrication and Evaluation of Carrageenan Based Bioplastic with Graphite and Ag-Nanoparticles Addition as Flexible Electrode for EMG Signal Measurement

Electromyography (EMG) is a method for measuring muscle biopotential signals for monitoring muscle activity. Electrodes are placed on the skin to capture EMG signals from muscles underneath. The most common electrodes used in clinical EMG measurement are Ag/AgCl electrodes in the form of metal plates coated with electrode gel. Electrode gel enhances the contact between the electrode’s metal plate and the skin since it is essential for a good measurement signal quality. Meanwhile, flexible electrodes are made from flexible conductive materials that can be adjusted to the contour of the skin surface; therefore, they can improve the measured biopotential signal quality. This study developed a carrageenan-based bioplastic with the addition of graphite and silver nanoparticles (AgNP) hybrid as a flexible electrode for EMG signal measurement. Fabrication of graphite and AgNP hybrid starts with the functionalization of the graphite powder in a mixture of HNO3 and H2SO4. Next, AgNPs were added using the electrochemical method by utilizing SnCl2 and functionalized graphite powder to form an Ag-Sn/Graphite (Graphite-AgNPs) hybrid conductive material. In order to incorporate conductive materials into bioplastic, the Graphite-AgNPs hybrid conductive material is then mixed into the carrageenan-based bioplastic mixture. It is found that 25% w/w addition of these conductive materials already gives good electrical conductivity. The best electrical conductivity value was determined by varying several conductive material types and concentrations. Finally, the EMG signal was measured with the bioplastic flexible electrodes, and the performance was compared with the commercial Ag/AgCl electrodes.

Technical note: Gas-phase nitrate radical generation via irradiation of aerated ceric ammonium nitrate mixtures

Abstract. We present a novel photolytic source of gas-phase NO3 suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize NO2 + O3 reactions and/or thermal dissociation of dinitrogen pentoxide (N2O5). The method generates NO3 via irradiation of aerated aqueous solutions of ceric ammonium nitrate (CAN, (NH4)2Ce(NO3)6) and nitric acid (HNO3) or sodium nitrate (NaNO3). We present experimental and model characterization of the NO3 formation potential of irradiated CAN / HNO3 and CAN / NaNO3 mixtures containing [CAN] = 10−3 to 1.0 M, [HNO3] = 1.0 to 6.0 M, [NaNO3] = 1.0 to 4.8 M, photon fluxes (I) ranging from 6.9 × 1014 to 1.0 × 1016 photons cm−2 s−1, and irradiation wavelengths ranging from 254 to 421 nm. NO3 mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [NO3] was achieved using [HNO3] ≈ 3.0 to 6.0 M and UVA radiation (λmax⁡ = 369 nm) in CAN / HNO3 mixtures or [NaNO3] ≥ 1.0 M and UVC radiation (λmax⁡ = 254 nm) in CAN / NaNO3 mixtures. Other reactive nitrogen (NO2, N2O4, N2O5, N2O6, HNO2, HNO3, HNO4) and reactive oxygen (HO2, H2O2) species obtained from the irradiation of ceric nitrate mixtures were measured using a NOx analyzer and an iodide-adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of NO3-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) from the β-pinene + NO3 reaction using a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to the HR-ToF-CIMS.

Ecological and Human Health Risk Assessment of Heavy Metals in Sediment of Selected Creeks in Rivers State, Nigeria

There has been much concern about the rate at which industrial and household wastes are released into Creeks in Rivers State. The study examined the status of heavy metal pollutants (Cd, Cu, Zn, Cr, Pb, and Ni) in sediment and to determine the extent of damage caused by these human factors using the most recent pollution index and Sediment quality guidelines (SQGs). The research was carried out in four important creeks along the Delta River network in Rivers State, Nigeria (Okrika, Borokiri, Eagle Island, and Kaa). Triplicate sediment samples were collected at a depth of 0-20 cm and extracted with 20cm3 of aqua ragia (a 3:1 mixture of HCl and HNO3) and 10cm3 of 30% H2O2. The metal concentrations were measured using an Atomic Absorption Spectrophotometer (AAS). The concentrations of the heavy metals ranged from 11.147–18.919mg/kg, 11.918–14.379mg/kg, 8.321–11.691 mg/kg, 6.405–11.72mg/kg, and 5.718–12.125mg/kg, and 2.429-7.725mg/kg respectively and followed the sequence Zn &gt; Pb &gt; Cr &gt; Ni &gt;Cu &gt; Cd. Geo-accumulation Index (Igeo) calculated was less than 0 i.e. uncontaminated for all metals except Pb in Borokiri Creek and Cd in all sampled creeks, showing moderate contamination. Eco-toxicological risk assessment (RI) indicated that the creeks were uncontaminated. Despite the low level of contamination, it is recommended that relevant authorities to regulate the indiscriminate dumping of domestic waste and untreated industrial effluents into the river to prevent the deterioration of the creeks