Water Concentration Research Articles

Cross-media transfer of polycyclic aromatic hydrocarbons in the Naples metropolitan area, southern Italy

At present, an in-depth knowledge of polycyclic aromatic hydrocarbons (PAHs) in the multimedia system of the urban environment remains limited. Taking the Naples metropolitan area (NMA) for instance, we simulated the cross-media transfer of PAHs using a multimedia urban model, involving air, water, soil, sediment, vegetation, and impervious film. The results indicated that the predicted PAH values in 2015 match well with their corresponding in-situ monitoring data. The PAH emission inventory and the simulated mass in various media all showed a downward trend from 2015 to 2020 due to national energy conservation policies and Corona Virus Disease 2019. The simulated mass of PAHs in the soil and sediment phases was 896.8 and 232.7 kg in 2020, respectively, contributing together to 96.7% of PAHs in the NMA. And they were identified as the greatest sinks for PAHs, and exhibited the longest retention duration, with values of PAH persistence reaching approximately 548.8 – 2,0642.3 hours. The results of transfer fluxes indicated that local emissions and atmospheric advection were the primary routes affecting the distribution of PAHs. The sensitivity analysis indicated that atmospheric advection rate was the most critical parameter for air, soil, vegetation, and film, whereas water concentration and sediment degradation rate were vital for water and sediment, respectively. This study offered valuable insights into how human activity contributes to the status and fate of PAHs in the urban environment.

Brillouin spectroscopy of medically relevant samples of bovine jugular vein and pericardium

There is the rapid growth in application of Brillouin scattering spectroscopy to biomedical objects in order to characterize their mechanoelastic properties in this way. However, the possibilities and limitations of the method when applied to tissues have not yet been clarified. Here, applicability of Brillouin spectroscopy for testing the elastic response of medically relevant tissues of bovine jugular vein and pericardium was considered. Parameters of the Brillouin peak were studied for samples untreated, diepoxide-fixed, and preserved after treatment in alcohol solutions. It was found that diepoxide cross-linking resulted to a slight tendency to increase the Brillouin position for hydrated tissues. The variations in the position and width of the Brillouin peaks, associated with local fluctuations in water concentration, were reduced after diepoxide treatment in the case of the pericardium, but not in the case of the vein wall. To obtain more information about the elastic response of the protein scaffold without the participation of water, dried samples were also studied. Brillouin spectra of the dried pericardium and vein wall revealed a significant increase in the Brillouin peak position (elastic modulus) after conservation in alcohol. In the case of the vein wall, this effect was found for both collagen and elastin-related peaks, which were identified in the Brillouin spectrum. This result corresponds to a denser packing of fibrous proteins after preservation in alcohol solutions. The ability of Brillouin spectroscopy to independently characterize the effect of treatment on the instantaneous elastic modulus of various tissue components is also attractive for its application in the development of new materials for bioimplants. A comparison of the Brillouin longitudinal and Young’s elastic moduli determined for the hydrated samples of the vein and pericardium showed that there is no clear correspondence between these material parameters. The usefulness of using both experimental methods to obtain new information about the elastic response of the material is discussed.

Using HFMEA to Reduce the Number of Colonies in the Water of Hemodialysis Room

<p>運用HFMEA手法降低血液透析室水處理之菌落數<br />國內血液透析中心發生多起透析用水處理不當導致的醫療疏失，讓醫病關係產生緊張及不信任感。本單位2018年04月至09月因透析液送檢不合格率為0.2%，故成立專案小組藉由醫療失效模式效應分析，檢視透析用水處理流程。發現問題有：漂白水濃度不足、漂白水靜置時間不足、透析機無自動開機沖洗、班間沖洗時間不足、透析機消毒時未吸取消毒液、透析機移動重新接水路未執行沖洗、透析用水採檢技術流程知識不足等問題，其改善措施為：修訂水處理系統消毒規範、修訂透析機消毒規範、修訂透析用水採檢流程。對策實施後，不合格率由0.2％降至為0％，高為險因子由10項降低為0項。藉此次專案讓人員瞭解HFMEA是著重於系統分析，可預防錯誤發生進而提升醫療安全。</p> <p> </p><p>Many cases of medical negligence caused by improper treatment of dialysis water occurred in domestic hemodialysis centers, which caused tension and mistrust between doctors and patients. From April to September 2018, the unqualified rate of dialysate was 0.2% in our hemodialysis room. Therefore, a task force team was set up to examine the dialysis water treatment process through the analysis of medical failure mode effects. We found problems that include: insufficient concentration of bleach water, insufficient standing time of bleach water, no automatic start-up flushing of the dialysis machine, insufficient flushing time between shifts, no antiseptic solution was absorbed during the disinfection of the dialysis machine, flushing was not performed when the dialysis machine was moved and reconnected to the water circuit and insufficient knowledge of the technical process of sampling of dialysis water. The measures of improvement are revising the disinfection specification of water treatment system, revising the disinfection specification of dialysis machine, and revising the sampling process of dialysis water. After the implementation of the countermeasures, the unqualified rate was reduced from 0.2% to 0%, and the high risk factors were reduced from 10 to 0. Through this project, personnel can understand that HFMEA focuses on system analysis, which can prevent errors and improve medical safety.</p> <p> </p>

Concomitant determination of pesticides in soil and drainage water over a potato cropping season reveal dissipations largely in accordance with respective models

Pesticides are widely used in agriculture where they do not only reach their targets but also distribute to other environmental compartments and negatively affect non-target organisms. To prospectively assess their environmental risk, several tools and models using pesticide persistence (DT50) and leaching potential (groundwater ubiquity score (GUS), EXPOSIT) have been developed. Here, we simultaneously quantified 18 pesticides in soil and drainage water during a conventionally grown potato culture at field scale with high temporal resolution and compared our findings with predictions of the above models. Overall dissipations of all freshly applied compounds in soil were in line with published DT50 field values and their occurrences in drainage water were generally consistent with GUS and EXPOSIT models, respectively. In contrast, soil concentrations of the legacy pesticide atrazine and one of its transformation products (atrazine-2-hydroxy) were constant during the entire sampling campaign. Moreover, during peak discharge atrazine concentrations in drainage water were diluted whereas those of freshly applied pesticides were maximal. This difference demonstrates that the applied risk assessment tools were capable of predicting environmental concentrations and dissipation of pesticides at the short and medium time scale of a few half-lives after application, but fell short of capturing long-term trace residues.

Oil shale enrichment mechanisms in the Lower Cretaceous Jiufotang Formation from the Ludong sag, Songliao Basin, Northeast China

In order to investigate the oil shale enrichment mechanisms and the relationship among gravity flows, volcanism, and oil shale deposition, detailed petrological, sedimentological, and organic geochemical research have been carried out on the Lower Cretaceous Jiufotang Formation in the Ludong sag, Songliao Basin, Northeast China. Seven facies were recognized and were grouped into three facies associations, namely hyperpycnites and intrabasinal turbidites, delta, and lacustrine facies associations. During the deposition of the lower Jiufotang Formation, hyperpycnites were developed during catastrophic flooding events that caused an abrupt increase in the discharge of water and sediment into the deep lacustrine environments, and a delta persisted during normal river discharge intervals and prograded into lacustrine environments. During the deposition of the upper Jiufotang Formation, deep lacustrine facies further expanded, and the extent of hyperpycnites decreased. Four types of oil shales were recognized in the Ludong sag of which those in the lower and upper Jiufotang Formation were defined as medium- to good-quality and good- to best-quality source rocks, respectively, exerting an overall thermal maturity of early oil generation. The lacustrine redox conditions show oxic to dysoic conditions in the lower Jiufotang Formation, and anoxic to dysoic conditions in the upper Jiufotang Formation. Oil shales were poorly-developed in the lower Jiufotang Formation and were well-developed in the upper Jiufotang Formation. During the active rift stage of the lower Jiufotang Formation, frequent occurrences of gravity flows and water-carried re-sedimentation of tuffaceous materials were unfavorable for oil shale accumulation. During the waning rift phases of the upper Jiufotang Formation, minor wind-transport of volcanic ash input into the deep lacustrine environments fertilized the lake water and supported algae blooms, leading to reduced oxygen concentrations in the bottom lacustrine waters along with high bioproductivity that were favorable for organic matter preservation and oil shale formation.

Smart App Assisted Colorimetric Determination of Iron: A Case Study in UDUPI Taluk

Abstract: Water is an important source for several uses. Water from surface and groundwater is used extensively to get the various industrial and domestic demands. Increased industrialization and urbanization discharges wastewater in the environment without treatment. By the infiltration and runoff, The water reaches subsurface and water above the ground and pollutes fresh water. Groundwater treatment is costlier and requires proper assessment. The area selected for study is Udupi taluk, Karnataka state. The study says that in Udupi region the soil is sensitive and here the soil is lateritic, there is a chance that the soil induces iron content in water which may increases concentration of iron in water. According to BIS 10500:2012 the limit of iron concentration in water is 0.3mg/lt. If iron content in water exceeds from 0.3mg/lt, it causes various health effects and waterborne diseases

Comparison of chemical contaminant measurements using CLAM, POCIS, and silicone band samplers in estuarine mesocosms.

Discrete water samples represent a snapshot of conditions at a particular moment in time and may not represent a true chemical exposure caused by changes in chemical input, tide, flow, and precipitation. Sampling technologies have been engineered to better estimate time-weighted concentrations. In this study, we consider the utility of three integrative sampling platforms: polar organic chemical integrative sampler (POCIS), silicone bands (SBs), and continuous, low-level aquatic monitoring (CLAM). This experiment used simulated southeastern salt marsh mesocosm systems to evaluate the response of passive (POCIS, SBs) and active sampling (CLAM) devices along with discrete sampling methodologies. Three systems were assigned to each passive sampler technology. Initially, all tanks were dosed at nominal (low) bifenthrin, pyrene, and triclosan concentrations of 0.02, 2.2, and 100 µg/L, respectively. After 28 days, the same treatment systems were dosed a second time (high) with bifenthrin, pyrene, and triclosan at 0.08, 8.8, and 200 µg/L, respectively. For passive samplers, estimated water concentrations were calculated using published or laboratory-derived sampling rate constants. Chemical residues measured from SBs resulted in high/low ratios of approximately 2x, approximately 3x, and 1x for bifenthrin, pyrene, and triclosan. A similar pattern was calculated using data from POCIS samples (~4x, ~3x, ~1x). Results from this study will help users of CLAM, POCIS, and SB data to better evaluate water concentrations from sampling events that are integrated across time. Integr Environ Assess Manag 2024;00:1-12. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Water modulates the chemiexcitation efficiency of the peroxyoxalate reaction: Enhancement at low and decrease at higher concentrations

Chemiluminescence transformations are widely utilized in analytical and bioanalytical applications. Specifically, the peroxyoxalate system can be employed for sensitive quantification of a wide variety of analytes. Under anhydrous conditions, the peroxyoxalate reaction shows extremely high emission quantum yields, comparable to highly efficient bioluminescence systems. However, in aqueous media, important for bioanalytical applications, the emission efficiency suffers a significant decrease of several orders of magnitudes, although the reason for this loss in efficiency is unknown up to now.In the present work, we show the results of a detailed photophysical study on the effect of water on the chemiexcitation efficiency of the peroxyoxalate reaction using bis(2,4-dinitrophenyl) oxalate as reagent and imidazole as base catalyst in the presence of different chemiluminescence activators. It is shown that in 1,2-dimethoxyethane/water mixtures (DME:H2O), singlet quantum yields increase with increasing the water concentrations up to 0.7 mol/L, followed by a steady decrease at higher water concentrations. The decrease in quantum yields is not predominantly due to concurrent ester hydrolysis, as quantum yields could be corrected for this side reaction. This indicates that the quantum yield decrease is due to the diminished chemiexcitation efficiency in the presence of water. Using different activators, it is shown that chemiexcitation occurs via electron transfer and electron back-transfer steps between a high-energy intermediate and the activator. Additionally, its efficiency is governed by the energetics of the electron back-transfer step, in agreement with the Chemically Initiated Electron Exchange Luminescence (CIEEL) mechanism, also in partially aqueous environment. Lower excitation efficiency in aqueous media may be due to formation of solvent-separated radical ion pairs, inhibiting chemiexcitation.

A Research Report Comprising on Behaviour of Sea Sand and Normal Sand

Abstract: Consumption of concrete has grown rapidly over a year, and it is also becoming one of the basic constructionmaterials. Since, it is a composite mixture of the constituents containing cement, fine aggregate, coarse aggregate and water. For manufacturing the concrete the fine aggregate are required more quantity. In general, river sand and RIVDER SAND is used as fine aggregate in construction industry. Due to this increase in use of river sand and RIVDER SAND the requirement has been increasing massively day by day in building sector. The government also have given some limitation on mining of river sand from the river beds. The treatment needed to remove the salt content in sea sand and sea water is difficult on time oftreatment and cost. So, the untreated sea sand is used in this test. The work on this study evaluates the different comparisons of mechanical properties of complete RIVDER SAND , complete sea sand (SS) and50% of RIVDER SAND with 50% of sea sand (MSSS). Main intention to consider the sea sand based concrete is to preserve the environmental resource in economical and sustainable development in construction and concrete sector. The experimental test results of sea sand based concrete shows adverse increase in strength compared to RIVDER SAND based concrete specimens

Experimental investigation on the effect of nano-enhanced phase change materials on the thermal performance of single slope solar still

Solar desalination is employed to create drinkable water from salt water. Using solar energy saves money and supplies clean, renewable fresh water. Nano-enhanced Phase change materials (NEPCM) and nano-enhanced absorption were utilized in this analysis to increase the capacity of solar desalination. Increased solar energy absorption makes anthracite content in saline water. CuO and AlN nanoparticles at 0.2 wt% and 0.4 wt% were combined in paraffin wax and injected into 12 copper pipes on the anthracite to boost the thermal characteristics of PCM. Copper pipes coated with dark paint containing scattered CuO nanoparticles to improve thermal conductivity. According to the findings, solar still production amplifies by 55.8 % and 49.5 %, respectively. Copper Oxide and Aluminium Nitride nanoparticles, each containing 0.2 wt%, lowered the melting temperature to 2.2ºCand 1.9ºC, respectively. It found that the CPL values of the Single slope solar still were 0.2₹/L and 8.26₹/L with the nano-enhanced PCM at 0.4 wt% CuO and AlN. The nano-coating also achieved a 5.7 % rise in the water production rate of the solar still.

Towards natural care products: Structural and deposition studies of bio-based polymer and surfactant mixtures

Oppositely charged polymer-surfactant systems are expected to interact with formation of coacervate complexes near composition of charge-neutrality. Such behaviour is widely used in formulated products (e.g. household and personal care), where the co-deposition of coacervates and active ingredients on various surfaces is triggered by dilution. A transition towards the use of more sustainable ingredients is currently ongoing as a response to the need of more environmentally conscious choices in production, albeit slowed down by the often more complex and not fully understood bulk and interfacial behaviour of new ingredients. In this work, mixtures of a medium-chain fatty acid (sodium decanoate) and two grades of bio-based cationic modified inulin were studied. The phase behaviour was determined in a wide composition matrix. The formation of coacervate complexes was observed for the mixture with the higher charge density polymer at a surfactant concentration of 1–3 wt%, close to the surfactant critical micellar concentration in pure water. Such behaviour was confirmed by DLS and SAXS data, suggesting surfactant-polymer complexation in a concentrated phase of packed micelles with a micelle-to-micelle distance of ∼4.5 nm. In situ ellipsometry and neutron reflectometry experiments were conducted to study the effect on surface deposition when diluting. The ellipsometry showed an adsorbed mass of ∼1.3–1.9 mg/m2, consistent with the deposition of a coacervate layer, and considerably higher than the neat, adsorbed polymer layer of ∼0.3 mg/m2. In the case of the neutron reflectometry experiments, dilution was performed before contact with the surface (pre-mixing), and no adsorption of coacervates was observed, but rather the adsorption of a polymer layer (0.49–0.85 mg/m2). The different results obtained with the different techniques highlight the kinetic nature of bulk coacervate formation and deposition, and the competition between these two phenomena. Maximal deposition can be achieved if one can control this time window either by tuning the composition of the system or the experimental set-up, to mimic the conditions of a specific application.

Synthesis of sandwich structure forward osmosis membrane with calcium-carboxyl modified polyamide and tannic acid-Fe3+ interlayer and its application in coconut water concentration

In this study, a sandwich structure thin-film composite forward osmosis (TFC-FO) membrane based on calcium-carboxyl interfacial polymerization was synthesized using tannic acid-Fe (TA-Fe) as the interlayer. Additionally, the concentration effect of Ca2+ surface modification, TA-Fe intermediate layers, and their combination on coconut water concentration, membrane efficiency, anti-fouling ability, and quality of the concentrate was investigated. Compared to the TFC-Ca or TFC-TA-Fe membrane, the TFC-TA-Fe-Ca membrane significantly enhanced the concentration effect and reverse salt flux (p < 0.05) and exerted the lowest attenuation of permeability. Furthermore, the total soluble solids content increased from 5.13 °Brix to 13.17 °Brix after 8 h. The TFC-TA-Fe-Ca membrane showed a 61.20 % increase in its efficiency compared to the TFC membrane. The total reducing sugar, acids, and polyphenol contents increased by 1.72, 1.34, and 1.22 times, respectively. Overall, the sandwich structure FO membrane exhibited significant feasibility and potential for industrial application in fruit juice concentrate production.

Study on Sensing Urine Concentrations in Water Using a Microwave Sensor Based on Hilbert Structure.

In this study, a two-port network-based microwave sensor for liquid characterization is presented. The suggested sensor is built as a miniature microwave resonator using the third iteration of Hilbert's fractal architecture. The suggested structure is used with the T-resonator to raise the sensor quality factor. The suggested sensor is printed on a FR4 substrate and has a footprint of 40×60×1.6mm3. Analytically, a theoretical investigation is made to clarify how the suggested sensor might function. The suggested sensor is created and put to the test in an experiment. Later, two pans to contain the urine Sample Under Test (SUT) are printed on the sensor. Before loading the SUT, it is discovered that the suggested structure's frequency resonance is 0.46 GHz. An 18 MHz frequency shift is added to the initial resonance after the pans are printed. They monitor the S-parameters in terms of S12 regarding the change in water content in the urine samples, allowing for the sensing component to be completed. As a result, 10 different samples with varying urine percentages are added to the suggested sensor to evaluate its ability to detect the presence of urine. Finally, it is discovered that the suggested process' measurements and corresponding simulated outcomes agreed quite well.

Microplastic Content in Fish and Sea Water at Air Tawar Coast, Padang City, Indonesia

Every year, millions of tons of plastic contaminate marine ecosystems, disrupting the natural balance and endangering marine life. Marine debris, especially plastic, is exposed to sunlight and repeated physical activities in the ocean, eventually breaking down into microscopic particles known as microplastics. This research aims to identify the presence of microplastics in fish and seawater at Air Tawar Coast, Padang City, Indonesia, based on their shapes, colors, and sizes. Seawater samples were collected at 3 stations using purposive random sampling along the direction of net trawling. Water samples were collected using a plankton net and filtered horizontally at the sea surface. Fish samples were obtained from the catches of fishermen, using trawl net (maelo pukek). The fish sampled were Selar and Kembung fish. Microplastics found in seawater and fish exhibited various shapes, including fibers, films, fragments, and pellets, with pellets and granules being the most dominant shapes. The colors of microplastics found in this study were black, brown, red, orange, blue, yellow, green, and purple, with dark colors (black and brown) being the most dominant. The abundance of microplastics at station 1 was 140.12 particles/m3, at station 2 was 151.27 particles/m3, and at station 3 was 129.61 particles/m3. The number of microplastic particles found in Kembung was higher than in Selar. On average, Selar fish contained 228 particles/individual, while Kembung fish contained an average of 267.5 particles/individual. The smallest particle size was found in pellet form, with a size of 8.12 µm, while the largest particle size was found in film form, measuring 174.56 µm.

Assessment of Natural Radioactivity and Associated Radiological Indicators in Water and Surface Soils Around Beta Glass Plc and Its Environs, Ughelli, Delta State, Nigeria

A radiometric assessment was conducted around Beta Glass plc using sodium iodide detector (3×3-inch NaI (TI)). The study collected 14 soil and 13 water samples from June to July 2022, analyzing radioactivity concentrations of 40K, 238U, and 232Th. The mean specific activity concentrations of 40K, 238U, and 232Th were 184.00±29.73 Bqkg-1, 14.55±2.50 Bqkg-1, and 8.60±1.04 Bqkg-1, respectively, in soil samples, but these elements' concentrations in water were 27.429±5.633 BqL-1, 6.661±1.421 BqL-1, and 2.518±0.361 BqL-1, respectively. The average activity concentrations of 40K, 238U, and 232Th were lower than the safe limit, and the corresponding radiation hazard indices for soil samples were all below the UNSCEAR-recommended acceptable limits. The mean activity concentrations of radionuclides in water samples were higher than the UNSCEAR's recommended international limits for 40K, 238U, and 232Th. Nonetheless, elevated radiological health hazards imply that cumulative dosages may cause cancer, even though these values might not pose an immediate health concern to the local community's people or the workforce.

The synthesis and application of L-cysteine graphene quantum dots for quantitative analysis of nitrite content in water

The limit standard of nitrite content in drinking water is an internationally recognized safety indicator. Some fluorescence analysis methods used for quantitative analysis of nitrite suffered from low anti-interference performance and inadequate specificity. In this article, L-cysteine graphene quantum dots have been synthesized and used to built a sensor system of ratiometric fluorescence with CdTe quantum dots. The L-cysteine graphene quantum dots were characterized by TEM and XPS. Results shown that the size of product is about 2 nm with homogeneous dispersion and a interplanar distance 0.235 nm, and there were hydroxyl, carboxyl, amino and sulfhydryl groups on its surface. Also, according to the linear association between nitrite concentrations and the ratio of fluorescence intensities at 421 and 570 nm (F421 nm/F570 nm), the quantitative analysis of nitrite in water has been realized, of which the linear range was 7.25–72.5 nmol/l, and the lowest detection limit was 3.012 nmol/l. This method with high sensitivity, selectivity, and anti-interference ability might be applied to analyze of nitrite in water quantitatively.

Pockmarks and associated fresh submarine groundwater discharge in the seafloor of Puck Bay, southern Baltic Sea

This is the first well-documented report on the occurrence of pockmarks in Puck Bay. Pockmarks in the seafloor of Puck Bay were discovered during a hydroacoustic survey carried out in 2020. They are located at a depth of 25–27 m in the southwestern part of the bay. Significant depletion of chloride (Cl−) concentrations in sediment pore water was found within the depressions. Most likely, the formation of pockmarks was due to groundwater flow through the Miocene–Pleistocene system of aquifers, which extends from land to the bay area. One-dimensional modeling of vertical Cl− concentration profiles in pore water revealed the upward flow of freshened groundwater within the pockmarks. The magnitude of submarine groundwater discharge (SGD) was estimated to vary from 1.53·10−2 to 18·10−2 L·m−2·h−1. The effect of groundwater seepage was also observed at 3 cm above the seafloor within the pockmarks, which was identified as a decrease in salinity of approximately 0.12 PSU compared to reference sites.Furthermore, due to the effect of water advection, SGD can be detected even several meters above the seafloor as a decrease in salinity values within the thermocline layer.

Effect of mass ratio on rGO/TiO2 composite as catalyst for methylene blue degradation under UV irradiation

Adsorption and photocatalytic are commonly used methods for the removal of dye contained in industrial wastewater. Therefore, this study aimed to combine reduced Graphene Oxide (rGO) with Titanium Oxide (TiO2) through various compositions using the hydrothermal method to obtain a catalyst of rGO/TiO2 nanocomposites for the removal of contaminants from wastewater. The synthesized rGO/TiO2 nanocomposites were mixed with methylene blue (MB) to reduce their content in water under dark conditions and UV light irradiation. The change of the optical properties of MB under both conditions was also examined, where a decrease in absorbance was observed. Under UV light irradiation, the maximum wavelength [Formula: see text] of MB shifted from 664[Formula: see text]nm to 649[Formula: see text]nm but remained constant at 664[Formula: see text]nm in dark conditions. The results of optical characterizations confirmed that the adsorption of MB by rGO/TiO2 nanocomposites under dark conditions did not change the MB structure. However, a significant degradation was observed with photocatalytic process under UV light irradiation. Nanocomposites rGO/TiO2 with rGO 60% and TiO2 40% (GT40) have better performance in reducing MB under UV light irradiation.

Adsorption of Cr(VI) and Cr(III) on layered pipe scales and the effects of disinfectants in drinking water distribution systems

Pipe scales in drinking water distribution systems (DWDS) potentially adsorb chromium (Cr). Meanwhile, the fate of Cr in pipe scales and water could be influenced by the disinfectants used in DWDS since they might influence the valence state of Cr. Therefore, the adsorption of Cr (Cr(VI) and Cr(III)) on pipe scales, the transformation between different valence states, and the effects of disinfectants present in DWDS are important research topics for improving tap water quality but have not yet been sufficiently investigated. This study investigated the properties of layered pipe scales and conducted adsorption kinetic experiments in single and binary Cr(VI) and Cr(III) systems, as well as experiments related to the oxidation and adsorption of Cr(III) under the influence of decaying disinfectants. According to the results, pipe scales exhibited distinct layered structures with varying mechanisms for the adsorption of Cr(VI) and Cr(III). Cr(VI) was adsorbed through surface complexation on the surface and porous core layers, while redox reactions predominantly occurred on the shell-like layer. Furthermore, Cr(III) was adsorbed via surface precipitation on the three-layer pipe scales. Importantly, disinfectants promoted the transformation of Cr(III) to the less readily released Cr(VI) in pipe scales, reducing the Cr exposure risk from the pipe scale phase. Pipe scales also decreased the Cr(VI) concentration in water (almost 0 mg/L), enhancing the safety of DWDS. This study provides theoretical guidance on the safe operation of DWDS.

Microplastic pollution in the Thumbprint emperor (Lethrinus harak) from Tanzanian coastal waters: Occurrence, abundance, characterization, and relevance as a monitoring species

In the present study we collected the Thumbprint emperor (Lethrinus harak) from seven landing sites from the coastal waters around Dar es Salaam and Zanzibar (Tanzania) to (i) quantify and characterize microplastics (MPs) in their digestive tracts and (ii) use previously assessed environmental levels in nearshore surface waters and seabed sediments to determine whether L. harak could be a relevant biomonitor for MP pollution in the region. L. harak (n=387) had an overall frequency of occurrence (FO%) of 48 % and displayed spatial variation between sites with Kunduchi (FO=66.7 %) and Mijimwena (FO=17.1 %) having the highest and lowest FO%, respectively. Fish from Mjimwema had a mean MP content of 0.17 ± 0.38 MPs individual-1 whilst fish from Kizimkazi had the highest MP abundance (1.75 ± 2.33 MPs individual-1). Fibers (overall 64.7 %, range across sites 48–86 %) and fragments (17.9 %, 5–25 %) were the most dominant MP types whilst black (46.9 %, 40–58 %) and blue (22.5%, 7–36 %) MPs were the most common colours. Fish length (ρ= -0.09, p=0.09) or weight (ρ=0.07, p=0.18) did not significantly correlate to MP abundance in fish (Spearman rank correlations). Neither MP occurrence nor abundance was linked to MP concentrations in either surface waters or seabed sediments (Spearman rank correlation), but MPs in the fish better reflected MPs in the sediment compared to surface water (two-way ANOVA on ranked data). Whilst L. harak presents as a promising candidate to monitor MP pollution along the East African coast due to its ecology, overall, it lacks reliability. Nonetheless, the present study fills important knowledge gaps both geographically on the East African Coast and with an underrepresented taxonomic family (Lethrinidae ‘Emporer fishes’).