Tap Water Samples Research Articles

Boron, nitrogen, and sulfur co‐doped carbon dots as a fluorescence probe for label‐free analysis of Hg2+

AbstractHg2+ is one of the most toxic heavy metals, posing a serious threat to the human body and the environmental ecosystem. In order to detect Hg2+ rapidly, accurately, and sensitively, a kind of boron, nitrogen, and sulfur co‐doped carbon dots (B,N,S‐CDs) were synthesized by a simple, economical, and direct hydrothermal method. The average size of the prepared B,N,S‐CDs is 2.7 ± 0.7 nm, and the high photoluminescence quantum yield is 67.6%. Furthermore, due to the efficient quenching effect of Hg2+, such B,N,S‐CDs are considered to serve as an efficient fluorescence sensing platform for label‐free and sensitive detection of Hg2+ with a detection limit of 72 nM. The selectivity experiments reveal that the B,N,S‐CDs are selective and specific for Hg2+ even in the presence of other interfering substances. Most importantly, the Hg2+ sensing platform based on B,N,S‐CDs can be successfully applied to the determination of Hg2+ in tap water and real lake water samples. This stable and inexpensive carbon material exhibits excellent sensitivity and selectivity, potentially suitable for Hg2+ monitoring in environmental applications.

Dye-sensitized lanthanide-doped upconversion nanoprobe for enhanced sensitive detection of Fe3+ in human serum and tap water

Iron ion (Fe3+) detection is crucial for human health since it plays a crucial role in many physiological activities. In this work, a novel Schiff-base functionalized cyanine derivative (CyPy) was synthesized, which was successfully assembled on the surface of upconversion nanoparticles (UCNPs) through an amphiphilic polymer encapsulation method. In the as-designed nanoprobe, CyPy, a recognizer of Fe3+, is served as energy donor and β-NaYF4:Yb,Er upconversion nanoparticles are adopted as energy acceptor. As a result, a 93-fold enhancement of upconversion luminescence is achieved. The efficient energy transfer from CyPy to β-NaYF4:Yb,Er endows the nanoprobe a high sensitivity for Fe3+ in water with a low detection limit of 0.21 μM. Moreover, the nanoprobe has been successfully applied for Fe3+ determination in human serum and tap water samples with recovery ranges of 95 %-105 % and 97 %-106 %, respectively. Moreover, their relative standard deviations are all below 3.72 %. This work provides a sensitive and efficient methodology for Fe3+ detection in clinical and environmental testing.

Sensitive and rapid determination of tetracycline antibiotic by carrot juice-derived carbon dots as a fluorescent probe.

The antibiotic tetracycline can be efficiently used as medicine for the deterrence of bacterial infections in humans, animals, and plants. However, the unprecedented use of tetracycline is of great concern owing to its low biodegradability, extensive usage, and adverse impacts on the environment and water quality. In this study, a sensitive spectrofluorometric method was proposed for the direct determination of tetracycline, based on biocompatible fluorescent carbon dots (CDs). The synthesis of CDs was performed by adopting a green hydrothermal procedure from carrot juice without requiring surface passivation or outflowing any environmentally hazardous waste. X-ray diffraction analysis and transmission electron microscopy revealed amorphous spherical-shaped CDs that exhibited blue emission under blue illumination. The fabricated fluorescent probe directly detected tetracycline in the concentration range of 4.00 ×10-6 to 1.55 ×10-5mol L-1 with an LOD of 1.33 ×10-6mol L-1. The performance of the probe was assessed in a tap water sample, with recovery values between 80.70 and 103.60%. The method's greenness was evaluated using the Analytical Green metric approach (AGREE) and confirmed to be within the green range. The developed method is facile, rapid, cost-effective, and offers a wide linear range and satisfactory selectivity, making it potentially suitable for determining tetracycline in water applications.

A Novel Electrochemical Sensing Based on Cerium Oxide/Nitrogen-Doped Reduced Graphene Oxide for Sensitive Detection of Acetaminophen

Acetaminophen (ACP), a common analgesic and antipyretic medication, can harm the liver when overdosed and its metabolites can contaminate the environment, so it is necessary to monitor the concentration precisely and reliably. In this work, we successfully synthesized cerium oxide/nitrogen-doped reduced graphene oxide (CeO2/N-rGO) composite nanomaterials using a one-step hydrothermal method. Using composite nanomaterials, we created an electrochemical sensing detection platform for ACP detection. The synthesized materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The constructed electrochemical sensor exhibits good ACP detection ability under the synergistic effect of CeO2 and N-rGO. Under optimal experimental conditions, the sensor displayed a linear range for the detection of ACP of 1 ∼ 200 μM and the lowest detection limit of 0.79 μM, exhibiting outstanding selectivity, stability, and repeatability. Furthermore, the sensor was effectively applied to detect ACP in tap water samples, which offers a wide range of possible applications in actual sample testing.

Per- and polyfluoroalkyl substances (PFAS) in paired tap water and house dust from United States homes

Most people in the United States have been exposed to per- and polyfluoroalkyl substances (PFAS) which have been linked to a wide array of adverse health conditions in adults and children. The consumption of contaminated drinking water is an important human exposure pathway to PFAS. Residential sources also contribute to PFAS exposure through dermal contact and ingestion of house dust, which acts as an aggregate of chemicals from sources like furnishing materials and consumer products. The U.S. Department of Housing and Urban Development (HUD) conducted the first nationwide survey of residential hazards called the American Healthy Homes Survey (AHHS) in 2005, followed by a second survey (AHHS II) in 2017. The U.S. Environmental Protection Agency (EPA) collaborated with HUD on both efforts and subsequently analyzed PFAS in household tap water and house dust collected from the same homes during the AHHS II study. This study leverages these paired samples to investigate potentially important exposure sources and pathways in the residential environment. Here we report results for paired household tap water and house dust samples from 241 homes for 13 and 16 PFAS chemicals, respectively. All 13 targeted chemicals were detected in the household tap water samples with detections ranging from 100 % for PFBS to 1 % for PFNS, and all 16 targeted chemicals were detected in the house dust samples with detections ranging from 97 % for PFOA to 9 % for PFNS. Four chemicals (PFOA, PFOS, PFHxS, and PFHpA) were measured above the limit of detection in at least 50 % of the samples in both media. All households had at least one of the targeted PFAS detected in both their tap water and house dust. Results provided evidence that geographical factors, such as proximity to ambient contamination sources, were main drivers of PFAS contamination in tap water, while PFAS contamination in house dust was driven mainly by within-home sources. Exposure estimates calculated from the measured PFAS concentrations highlight the importance of addressing potential sources of exposure to PFAS within homes in addition to ambient sources affecting communities’ drinking water, particularly to reduce children’s exposure to these chemicals.

In-syringe homogeneous liquid–liquid microextraction as an economical, convenient, and one-step analytical method for the extraction and preconcentration of five plasticizers and one antioxidant from different city tap water samples

In this study, an analytical method called in-syringe homogeneous liquid–liquid microextraction was developed and applied for the extraction and preconcentration of plasticizers including di ethyl phthalate, di isobutyl phthalate, di-n-butyl phthalate, di(2-ethylhexyl) adipate, and di(2-ethylhexyl) phthalate and one antioxidant, (butylated hydroxytoluene). Only a few microliters of dibutyl amine was used as the extraction solvent. This switchable solvent became miscible in the solution of interest by adding acetic acid at µL-level to extract the analytes. Also, the addition of sodium carbonate (in mg-level) into the solution led to the release of carbon dioxide, which facilitated the extraction of plasticizers into the extractant. Also, sodium carbonate caused to the regeneration of the extractant in the upper narrow bore of the syringe. The enriched analytes were determined by a gas chromatographic equipped with a flame ionization detector. Under the optimum conditions, extraction recoveries and enrichment factors were obtained in the ranges of 39–78 % and 196–394, respectively. Also, the limits of detection and quantification were in the ranges of 1.76–12.51 µg/L and 5.80–41.28 µg/L, respectively, and the r2 values were equal to or better than 0.991. Development of the method as a one-step analysis processed which was electrically independent in extraction and preconcentration stage (no centrifugation or vortexing) and inexpensive. The use of only µL-level of organic solvent, convenient operation, and short extraction time are the other highlights of the method. This method was successfully applied to the extraction, preconcentration, and determination of several plasticizers in eight different city water samples.

Assessment of Indoor and Water Radon Concentrations in Esenyurt and Beylikdüzü Districts of Istanbul, Marmara Region, Turkey

The radon activity concentration measurements for indoor and tap water were studied in Esenyurt and Beylikdüzü districts of Istanbul Province, Turkey. The mean radon concentration value received from thirty-six passive radon detectors was obtained as 63.56 Bq/m3. The mean annual effective dose for indoor radon measurements is 1.60 mSv/y in this measurement period. The radon activity results of calculated tap water samples were under 0.8 Bq/L. The annual effective doses resulting from ingestion and inhalation were calculated to evaluate the health risk across various age groups. All radon measurement results, and the associated calculated data for ingestion and inhalation remained below the threshold values established by international organizations

Carbon quantum dots with ultra-high quantum yield for versatile turn-on sensor of gluten and cyanide Ions

In this work, we reported the synthesis of carbon quantum dots (CQDs) with high fluorescent quantum yield (90.7 %). These nanoparticles were applied in a turn-off/turn-on sensor able to detect cyanide ions. In this sensing strategy, Fe3+ ions were added to the aqueous suspension of CQDs to quench the fluorescence of the system, which was recovered from the presence of cyanide ions. Furthermore, a sensor array was developed using the LDA chemometric tool, to classify different species present in cookie formulations, including gluten. The turn-off/turn-on sensor proved to be sensitive and effective for detecting cyanide ions, with a detection limit of 3.77 ppm. This high sensibility and selectivity allowed quantifying the analyte in a real sample of tap water.

Photocurrent polarity switching photoelectrochemical aptasensor for oxytetracycline based on BiOBr/Ag2S/PDA//CuO: CuO-induced II-type to dual Z-scheme system

BackgroundAs a broad-spectrum tetracycline antibiotic, Oxytetracycline (OTC) was widely used in a variety of applications. But, the overuse of OTC had led to the detection of it in food, water and soil, which could present significance risk to human health and cause damage to ecosystem. It was of great significance to develop sensitive detection methods for OTC.Herein, an environmentally friendly photoelectrochemical (PEC) aptasensor was constructed for the sensitive detection of OTC based on CuO-induced BiOBr/Ag2S/PDA (Polydopamine) photocurrent polarity reversal. ResultsBiOBr/Ag2S/PDA composites modified electrode not only produced stable initial anodic photocurrent but also provided attachment sites for the aptamer S1 of OTC by the strong adhesion of PDA. On the other hand, CuO loaded OTC aptamer S2 (Cu–S2) was got through Cu–S bonds. After the target OTC was identified on the electrode surface, CuO was introduced to the surface of ITO/BiOBr/Ag2S/PDA through the specific binding of OTC to S2. This identification process formed dual Z-type heterojunctions and resulted in a remarkable reversal of photocurrent polarity from anodic to cathodic. Under optimization conditions, the PEC aptasensor showed a wide linear range (50 fM ∼ 100 nM), low detection limit (1.9 fM), excellent selectivity, stability and reproducibility for the detection of OTC. Moreover, it was successfully used for the analysis of OTC in real samples of tap water, milk and honey, and had the potential for practical application. SignificanceThis work developed an environmentally friendly photocurrent-polarity-switching PEC aptasensor with excellent selectivity, reproducibility, stability, low LOD and wide linear range for OTC detection. This sensitive system, which was including BiOBr, Ag2S, PDA and CuO were low toxicity, not only reduced the risk of traditional toxic semiconductors to operators and the environment, but can also be used for the detection of real samples, broadening the wider range of applications for BiOBr, Ag2S, PDA and CuO.

Synthesis of non-modified near-infrared carbon dots for hypochlorite detection and cell membrane imaging

Devising carbon dots with long wavelength emission (red light or near infrared), high selectivity and good bio-compatibility is critical in fluorescence detection and imaging, but achieving this goal remains a great challenge. Herein, near-infrared emissive carbon dots (NIR-CDs) with obvious emission characteristic of 653 nm were synthesized through hydrothermally treatment of toluidine bule and gallic acid. Noticeably, the NIR-CDs exhibited excellent selectivity and sensitivity to hypochlorite (ClO−), and the limit of detection is as low as 42.7 nM. The selective recognition reaction between ClO− and the surface functional groups of NIR-CDs inhibits the fluorescence from NIR-CDs. The quenching mechanism was confirmed by fluorescence lifetime decays, FT-IR spectroscopy and UV–vis absorption spectra. More remarkably, the NIR-CDs have rich hydrophilic groups showed lower cytotoxicity, excellent bio-compatibility and specific cell membrane localization ability. The established spectrofluorometric method based on NIR-CDs has been used to determination of ClO− level in tap water sample, the recoveries were 97.7 %–103.3 %. In addition, the NIR-CDs also has been successfully applied for the imaging of cell membrane. The study provides a novel idea for developing NIR ClO− probe as well as cell membrane localization probe based on CDs, which present bright prospects in real water samples monitoring and cell membrane imaging.

A fluorescent sensor array based on a single cucurbit[5]uril-truxene probe for simultaneous identification of five heavy metal ions.

There is a need to develop simple and effective strategies for the rapid detection of heavy metal ions (HMIs) in order to protect the environment and human health. A simple fluorescent sensor array based on a single cucurbit[5]uril-truxene probe was proposed to simultaneously identify five HMIs (Pb2+, Cu2+, Ag+, Fe2+ and Fe3+). This probe was synthesized using monohydroxyl cucurbit[5]uril and monobromohexyl truxene by a substitution reaction between them. It could be observed that the fluorescence response of this synthesized probe to HMIs was closely related to the pH of the aqueous solution, exhibiting different fluorescence intensities at pH 3.0, 7.0, and 9.0. Based on this phenomenon, a fluorescent sensor array based on a single cucurbit[5]uril-truxene probe was then constructed by simply altering the pH in the sensor element. These unique fluorescence responses were analyzed using linear discriminant analysis (LDA) to identify metal ions. A concentration limit classification of 0.1 μM was applied to the above five HMIs. Moreover, the quantification of metal ions was implemented even at low concentrations of 48-121 nM. This array showed good results in the recognition of metal ions in real water samples (lake water and tap water samples), which shows its broad application prospects in many fields, including monitoring of the environmental water quality and so on.

A novel Z-scheme covalent triazine framework/silver phosphate (CTF/Ag3PO4) heterojunction photocatalyst: Improved adsorption, photocatalytic degradation and degradation mechanism of rifampicin

In order to achieve a suitable covalent triazine framework (CTF) photocatalyst, it is imperative to further improve synthesis conditions of ionothermal trimerization technique. Therefore, in this study, CTF was prepared using a binary ZnCl2-NaCl molten salt mixture at 250 °C for 20 h. Furthermore, a Z-scheme CTF/silver phosphate (CTF/Ag3PO4) was prepared by facile in-situ precipitation technique for the adsorption and photocatalytic degradation of rifampicin (RIF) under visible light. The synthesized CTF, Ag3PO4, and CTF/Ag3PO4 composites were extensively characterized using various spectroscopic tools. The composites displayed improved visible light absorption, low resistance to charge transfer, and enhanced heteroatom effect (HAE) compared to pristine CTF and Ag3PO4. The CTF/Ag3PO4 composite showed improved rifampicin removal from solution. Consequently, the 0.75 % CTF/Ag3PO4 composite attained an adsorption capacity of 41.72 mg/g and 100 % degradation of RIF, which corresponded to a 3.5-fold improvement compared to pristine CTF. Its efficiency was attributed to its narrow band gap of 2.20 eV, improved surface area, and low resistance to charge transfer. Degradation product analysis revealed that rifampicin with m/z of 823 was successfully degraded to m/z of 189 within 360 min. The successful removal of RIF from influent wastewater (65.5 %) and tap water (75.5 %) samples indicates the practical application of 0.75 % CTF/Ag3PO4. The stability measurement suggests a stable 0.75 % CTF/Ag3PO4 material compared to Ag3PO4.

Discrimination of bottled mineral water from tap water using a Dip-Type colorimetric paper-based sensor array and chemometrics

Mineral water is a natural water that originated from an underground water table, a well, or a natural spring which is considered microbiologically intact. The revenue from the bottled mineral water industry will be USD 342.40 billion in 2023, and it is expected to grow at a compound annual growth rate (CAGR) of 5.24 %. Consequently, the discrimination of original bottled mineral water from tap water is an important issue that requires designing sensors for simple and portable identification of these two types of water. In this work, we have developed a Dip-Type colorimetric paper-based sensor array with three organic dyes (Bromothymol Blue, Bromophenol Blue, and Methyl Red) followed by chemometrics’ pattern recognition methods (PCA and LDA) for discrimination of original bottled mineral waters from tap waters based on differences in ion variety and ion quantity. Forty brands of mineral water and twenty-six Tap water samples from different regions of Shiraz and other Iranian cities were analyzed by this sensor array. Moreover, these experiments were performed in two consecutive years to check the versatility of the sensor with seasonal changes in waters. This sensor array was able to discriminate these two water types from each other with an accuracy of > 95 % based on the analysis of 85 water samples.

A smartphone-integrated ratiometric fluorescent platform based on europium (III)-functionalized metal-organic frameworks for quantitative and visual detection of tetracycline

Food safety and environmental pollution caused by tetracycline antibiotics (TCs) are of great concern for public health worldwide. To realize on-site, real-time, ultrasensitive visual detection of tetracycline is an urgent need. Herein, a ratiometric fluorescent probe has been constructed by grafting Cit-Eu3+ on the amino-silanes-modified metal–organic framework for the detection of tetracycline. Under exciting at 330 nm,the red emission at 617 nm of Eu3+ was significantly enhanced by the antenna effect upon adding tetracycline, while the intrinsic fluorescence quenching at 425 nm of the probe ascribes to the inner filter effect, resulting in a reversible signal response. Under optimum conditions, the probe exhibits a visualized fluorescence evolution from blue to red with a linear range of 0.1–60 μM, and a limit of detection as low as 24.6 nM. Furthermore, a test strip was further fabricated by dropping NH2-MIL(Al)@SiO2-Cit-Eu3+ on filter paper, which can be used for on-site of tetracycline conveniently by using a smartphone. Moreover, the proposed probe has also been successfully applied for TCs detection in spiked honey and tap water sample with satisfactory recoveries in the range from 91.21–102.97 %, demonstrating the potential real application performance. This the smart sensing platform lays a foundation for the rapid screening of TCs in food and environmental matrices.

One‐pot hydrothermal biochar obtained from malt bagasse waste as an electrode‐modifying material towards the stripping voltammetric sensing of lead

AbstractPb2+ ions are highly toxic to living beings because they tend to bioaccumulate in the body. For this reason, the development of simpler, low‐cost, and easy‐to‐operate techniques that can detect and quantify low concentrations of metal ions would help to identify contaminating media and improve public health. This work proposes a Pb2+ voltammetric sensor based on a carbon paste electrode modified with hydrothermal biochar (hydrochar, HC) obtained from malt bagasse waste (HC/CPE). The obtained hydrochar was characterized by zero‐charge point, FT‐IR, XRD and thermogravimetry. The differential pulse adsorptive anodic stripping voltammetry (DPAdASV) technique was used to perform the Pb2+ determination. After optimizing important parameters for detecting Pb2+ ions and the parameters of the voltammetric technique employed, a linear response range of 0.50 to 7.06 μmol L−1 with a limit of detection (LOD) and limit of quantification (LOQ) of 55.0 and 181.5 nmol L−1 were achieved, respectively. The developed voltammetric procedure was applied towards the Pb2+ determination at tap water and river water samples, with excellent recoveries (ranging of 91.19 to 109.22 %), proving that the HC‐based electrode has great potential for detecting Pb2+ ions. Hydrothermal carbonization allowed the biomass to be converted into functionalized hydrochar, eliminating the need for subsequent functionalization/activation steps for use as a Pb2+ adsorbing material on the electrodic surface. The proposed sensor also proved to be easy to assemble and environmentally friendly by using biomass waste as the carbon material. Thus, the proposed sensor adds to the literature the possibility of simple and easy detection of metal ions with a waste reuse bias.

A selective and sensitive mercury sensor for drinking water based on fluorescence quenching of pure rhodamine B

The escalating threat of industrial pollutants, particularly heavy metals, in water sources poses a significant risk to global populations. Among these heavy metals, mercury stands out as a severe contaminant with detrimental health implications. This paper introduces a novel and efficient method for the selective detection of mercury ions in drinking water, employing laser-induced fluorescence with pure rhodamine B as the sensing probe. The method achieves a low detection limit of 7 ppb, closely approaching the World Health Organization’s maximum permissible limit. The simplicity of the procedure, coupled with the use of pure rhodamine B, distinguishes this approach from others relying on complex chemical procedures and derivatives of rhodamine B. The sensing mechanism involves the fluorescence quenching of rhodamine B due to complex formation with tetraiodomercurate. Noteworthy is the method’s selectivity, demonstrated by its resistance to interference from common ions present in water (e.g. Magnesium, calcium, sodium, and potassium), ensuring accurate detection of mercury ions. Extensive testing with tap water samples, considering potential interference, validates the robustness of the sensor, with recovery percentages of 99.25% and 109.2%. In summary, this study contributes a practical solution to the critical challenge of mercury detection in drinking water, addressing issues of sensitivity, selectivity, and on-site applicability. The proposed method holds promise for widespread implementation, enhancing efforts to safeguard public health and ensure the safety of water resources.

Distribution of inorganic compositions of Japanese tap water: a nationwide survey in 2019–2024

A nationwide survey of inorganic components of tap water all over Japan was conducted from 2019 to 2024. In this survey, 1564 tap water samples were collected, and an additional 194 tap water samples were collected from 33 other countries. The water samples were analyzed for 27 dissolved inorganic components, with a primary focus on the distribution of major and trace components, including Ca, Mg, K, Na, Cl−, NO3−, SO42−, total-hardness, Al, Fe, Cu, Mn, and Zn. The Japanese tap water hardness was 50.5 ± 30.2 (± 1σ SD) mg/L, classified as soft water according to the World Health Organization (WHO) classification. The average content of each major component in Japanese tap water tended to be lower than those in other countries. Furthermore, Piper trilinear diagrams were used to categorize Japanese tap water types. The dominating water types were the Ca–HCO3 and mixed types, which had a nationwide distribution. Japanese tap water generally complied with Japanese and WHO drinking water criteria, with only 1% (17/1564 sites) of the samples exceeding water quality standards. Observations of water quality changes for 2 years at three household faucets revealed that fluctuations in major components and trace metals (Al, Fe, Cu, Mn, and Zn) varied in different patterns. This suggests that the behavior of trace metal elements is influenced by local infrastructure, such as supply pipes, distinct from the variability in source water quality.

A sensitive aptasensor mediated by gold nanoparticles/metal organic framework lattice for detection of Pb2+ ion in marine products

Herein, an enzyme-free fluorescent aptasensor was introduced for the ultrasensitive quantification of lead (Pb2+) ion as a hazardous pollutant of the environment and foodstuffs. A nanocomposite of zeolitic imidazolate frameworks-8 and gold nanoparticles (ZIF-8@AuNPs) was utilized as an efficient quencher of the fluorescence intensity of carboxyfluorescein (FAM) signal reporter. The establishment of a hybrid structure between attached aptamer on ZIF-8@AuNPs nanocomposite, and its FAM-tagged complementary (CP) strand decreased the fluorescence response. The preferential binding between the aptamer and Pb2+ released CP strands, which retrieved the fluorescence signal. The aptasensor could assess Pb2+ in the linear concentration range of 1 pM-1 nM with a detection limit (LOD) of 0.24 pM. Besides, it could quantify Pb2+ in various samples, including fish, shrimp, tap water, milk, and serum samples. The developed aptasensor with the superiorities of easiness, cost-effectiveness, easy-to-operate, and rapidness is promising for controlling marine foodstuff safety.

Electrochemical sensor based on Y-shaped DNA by “one-pot” method for mercury detection

A DNA electrochemical sensor based on Y-shaped DNA probes was successfully designed for Hg2+ detection. The sensor was modified with carbon self-doping graphite-like carbon nitride (C-g-C3N4) and electrodeposited gold nanoparticles (EAu) to enhance conductivity and enrich the binding sites for DNA. DNA probe (S1) binded on the modified electrode via –SH, forming a stable Y-shaped DNA double helix structure with probe S2 and probe S3 anchoring on gold nanoparticles (nanoAu) in the presence of Hg2+ solution. The Y-shaped DNA duplex, with its tight and nondeformable rigid structure, created well-defined stereoscopic reaction areas and efficiently captures Hg2+ due to its structural differences, thereby improving the signal response. Moreover, larger amounts of methyleneblue (MB) could be loaded to provide adequate electrochemical response signal. The proposed sensor possessing signal amplification ability displayed a linear relationship between the square wave voltammetry (SWV) peak currents. Under the optimal conditions, Hg2+ could be detected in the range from 5000.0 to 5.0 nM with a detection limit of 8.5 pM. The sensor was also tested with tap water, river and medical wastewater samples. It showed the good recovery and accuracy and represented a promising method for Hg2+ detection.

Radiation protection for Gabes phosphate area residents: Assessing natural radioactivity in soil and potable water samples

Phosphate mining activities are recognized to be one of various industrial processes generating enhanced Naturally Occurring Radioactive Materials (NORM) by introducing natural radionuclides into the surrounding soils and water bodies, posing a risk to human health.This study was carried out to assess the level of natural radionuclides in soils and potable waters collected from the phosphate area of Gabes city, located in southeastern Tunisia, and to evaluate radiation protection measures by estimating radiological health hazard parameters. Gamma spectrometry system employing an HPGe detector was used in this study to assess 40K, 232Th and 226Ra activity concentration in soils. The average values were found to be 163.7, 14.5, and 7.7 Bq kg−1, respectively, which were lower than worldwide average values. The radiological hazard parameters assessed in this study were radium equivalent activity (Ra-eq), external hazard index (Hex), external gamma absorbed rate (GDR), external annual effective dose (Deff) and excess lifetime cancer risk (ELCR). The calculated average values of the above-mentioned parameters were of 41 Bq kg−1, 0.1, 20.2 nGy h−1, 24.8 μSv y−1 and 8.7 × 10−5 all of which were found to be below their permissible standards.For potable water samples, the activity concentrations of radium were analyzed using an HPGe detector and those of uranium were determined by alpha spectrometry. The average activity concentrations of uranium and radium isotopes in underground water samples were found to be higher than those obtained in tap water samples. For both types of water, the average values for all radionuclides were found to be below their respective reference limits.The annual ingestion effective doses were also estimated in this study. The estimated average values for infant and children for underground water samples were higher than the permissible limit of 100 μSv y−1 set by WHO. The 226Ra was the main contributor to the effective doses for different age categories, followed by 228Ra.