Concentration Levels In Water Research Articles

Statistical Analysis and Health Risk Assessment: Vegetables Irrigated with Wastewater in Kirri Shamozai, Pakistan.

One of the primary environmental routes through which humans are exposed to metals and may be exposed to health risks is the food chain's contamination with heavy metals. The study observed the risks posed by contaminants in vegetables produced in soil that received wastewater irrigation, as well as their origins and the human health impacts. Eight harmful metals (Cu, Fe, Zn, Mn, Pb, Cd, Ni, and Cr) were tested for concentration levels in water, soil, and vegetable samples using analytical techniques and an atomic absorption spectrophotometer. The present study investigated the potential health implications associated with the consumption of vegetables irrigated using wastewater containing heavy metals. The results indicated a notable accumulation of heavy metals in plant and soil samples obtained from Kirri Shamozai, Pakistan. In comparison to vegetables cultivated in soil irrigated with fresh water, the concentration levels of heavy metals in vegetables grown on soil irrigated with untreated wastewater were considerably higher at (P ≤ 0.001) and above the World Health Organization (WHO) recommended limits. The results showed that heavy metals had significantly accumulated in the soil and had permeated into the crops. Heavy metal concentrations in vegetables cultivated on land irrigated with wastewater were more significant than those grown on land irrigated with freshwater. They exceeded US EPA and World Health Organization (WHO) limits. PCA results for Pb, Cu, and Cr are the main issues impacting water quality and health hazards. The PCA results show that the soil has an extensive loading of heavy metals Cd, Ni, and Mn.

Pesticide Residues and Berry Microbiome after Ozonated Water Washing in Table Grape Storage.

Nowadays, different systems for reducing pesticides in table grapes are being tested at different production stages either in the field or in postharvest. The present study tested ozonated water treatments at the beginning of the cold storage of the Princess® seedless table grape variety to reduce the residue contents of some pesticides and to evaluate their effect on gray mold and the berry microbiome. An ozone generator capable of producing an ozone concentration ranging from 18 to 65 Nm3 was utilized for obtaining three ozone concentration levels in water: 3, 5 and 10 mg/L. Ozonated water was placed in a 70 L plastic box where 500 g grape samples closed in perforated plastic clamshell containers were immersed utilizing two washing times (5 and 10 min). Overall, six ozonated water treatments were tested. After the ozonated water treatments, all samples were stored for 30 days at 2 °C and 95% relative humidity to simulate commercial practices. The pesticide residue contents were determined before the ozonated water treatments (T0) and 30 days after the cold storage (T1). The treatments with ozonated water washing reduced the pesticide residues up to 100%, while the SO2 control treatment reduced the pesticide residues ranging from 20.7 to 60.7%. Using 3 mg/L ozonated water to wash grapes for 5 min represented the optimal degradation conditions for all of the analyzed pesticides, except for fludioxonil, which degraded better with a washing time of 10 min. The ozone treatments did not significantly reduce the gray mold and the fungal and bacterial microbiome, while a relevant reduction was observed in the yeast population.

Urinary outputs of nickel in association with their concentration levels in water, soil, and selected foods among farmers in the industrial estate of district swabi

Diet is the main route of exposure to trace metals, so the assessment risk of these elements to human via dietary intake is important. The non-carcinogenic health risk of Nickel (Ni) to the farmers via dietary intake in the Gadoon Amazai Industrial Estate (GAIE) Swabi of Kyber Pakhtunkwa was assessed. A cross sectional study was carried out in the GAIE to estimate the concentration of Nickel in all types of vegetables, grains, drinking water, irrigation water, soil and in urine of the farmers. A total of 22 farmers, living within the 2km distance in all four directions were selected and enrolled in the study after signing consent form. Atomic absorption spectrophotometer was used for the Ni analysis in the collected samples of water (both drinking and irrigation water), soil, foods and in urine of farmers. Results shows that the mean age of the farmers using tube well water and wastewater for irrigation purposes was 43.5±21.01 and 44.75±16.44 years, height was 167.6±3.7 and 165.75±6.02 cm, weight was 61±12.52 and 64.75±9.63 kg and BMI was 21.65±3.73 and 23.7±4.4 respectively. The concentration of the Ni in the wastewater irrigated field was significantly higher than the tube well irrigated field. The mean concentration of Ni in the soil irrigated with wastewater was 123.50±54.74 mg/kg respectively and in the tube-well irrigated field was 54.25±10.14 mg/kg. The Ni concentration in the wastewater irrigated garlic, fodder grass, potato, wheat and maize were 9.15±0.50 mg/kg, 8.82±1.30mg/kg, 7.70±1.04mg/kg and 7.56±1.24mg/kg respectively compared to tube-well irrigated land i.e., 0.97±0.25 mg/kg, 0.64±0.42 mg/kg, 1.08±0.35 mg/kg, 1.05±0.013 mg/kg and 1.02±0.39 mg/kg. A positive correlation was observed between the water, soil, and all crops grown in the GAIE . The bio-accumulation factor was higher for Ni in both the site. The Hazzard Quotient (HQ) for Ni exceeded the 1 for crops irrigated with industrial wastewater compared with tube-well irrigated crops and thus pose adverse health affect to farmers health. This study concluded that a strong association was evident between the Ni concentration in crops and cereals and waste-water irrigation.

Residual pesticides reduction on table grapes in post-harvest using ozonated water washing

Nowadays, different systems for reducing pesticides in table grapes are being tested at different production stages either in the field or in post-harvest. The present study tested ozonated water treatments at the beginning of the cold storage on Melissa seedless table grape variety to reduce residue contents of some pesticides. An ozone generator capable of producing ozone concentrations ranging from 18 to 65 Nm3 was utilized for obtaining three ozone concentration levels in water: 3, 5 and 10 mg/L. Ozonated water was placed into a 70 L plastic box where 500 g grape samples closed in perforated plastic clamshell containers were immersed utilizing two washing times (5 and 10 min). Overall, six ozonated water treatments were tested. After ozonated water treatments, all samples were stored for 30 days at 2 °C and 95% relative humidity to simulate commercial practice. Pesticide residue contents were determined before ozonated water treatments (T0) and 30 days after the cold storage (T1). The comparison highlighted the different degradation rates as regards Fludioxonil and Fluxapyroxad. The best results were reached among the non-systemic pesticide such as Fludioxonil. Using 3 mg/L ozonated water to wash grapes for 10 min represented the optimal degradation conditions for the analyzed pesticides.

Preliminary studies on microbial management efficiency of ozonated water on Italian ready-to-eat table grape variety

Ozonated water is an alternative means of post-harvest fruit and vegetable management that keeps gaining interest for its applications. The aim of this study was to evaluate the effects of ozonated water at different concentrations (12 mg L-1 and 8 mg L-1) on ready-to-eat Italian ‘Regal seedless’ grapes, to assess the ozone effect on grey mould and berry microbiome (non-Saccharomyces yeasts, total bacteria, and total fungi). An ozone generator capable of producing ozone concentration ranging from 18 to 65 Nm3 was used to obtain the different ozone concentration levels in water where berries were immersed. After 26 days of cold storage, grey mould incidence was assessed as percentage ratio between the number of affected berries and the total number of berries. Berries dipped into ozonated water at the higher ozone concentration of 12 mg L-1 showed a 61% average reduction of the overall disease incidence compared to the control. Moreover, the microbiome of berries treated with 12 mg L-1 ozone concentration showed significant reduction of fungal and yeast populations, while not showing any significant difference for the bacterial population, compared to the control.

Monte Carlo model for evaluation of concentration of gold nanoparticle clusters as predictor of effective dose in proton therapy of microscopic tumors

Radio-sensitization with gold nanoparticles (GNPs) is a relatively recent advancement of radiotherapy that is determined to increase radiation in the target tumor region. Monte Carlo (MC) simulation is a well-known method that has gained popularity by assisting in determining the effective dose in various tumors. Assessing the concentration of particles during proton therapy can provide the key to evaluating the efficiency of the performed treatment. Therefore, this study aimed to investigate the interconnection between the concentration of gold nanoparticle clusters and the dose enhancement in microscopic tumors by using the MC Model. A single cell tumor model with a size of 5 μm that was exposed to 100 MeV protons in a region resembling the human brain was investigated by using an MC simulation employing the Geant4 toolkit. With each nanoparticle having a diameter of 15 nm, a three-dimensional model of the random distribution of gold nanoparticle clusters was developed. Then, the dose enhancement for various concentrations of the GNPs accumulated around the tumor was estimated according to the dose enhancement factor (DEF), while the dose was concentrated on the surface of each GNP in the clusters. The results showed that the dose enhancement located at the Bragg-peak in the tumor region depended on the different concentrations of the GNPs. DEF values were found to be 1.016, 1.022, 1.026, 1.035, 1.013, 1.000, and 0.984 for the 1, 2, 3, 5, 10, 30, and 50 mg/ml concentration levels in water, respectively. The findings also revealed that large GNP clusters with high concentration levels yield larger DEFs than clusters with lower concentration levels, which may have an impact on radiation therapy. Specifically, at a concentration higher than 10 mg/ml, the estimated dose was significantly lower than those for a concentration of 5 mg/ml by about ∼100 mGy. As the benefit of the increased total dose must be balanced against the effect of the accumulation of nanoparticles, the current study detected dose reduction in regions that accumulate GNPs at high concentrations. As a result, the potential efficiency of the radiotherapeutic treatment can be reduced.

Impact of Cyanotoxin Ingestion on Liver Cancer Development Using an At-Risk Two-Staged Model of Mouse Hepatocarcinogenesis.

Exposure to cyanobacterial hepatotoxins has been linked to the promotion and increased incidence of liver cancer in pre-clinical and epidemiologic studies. The family of hepatotoxins, microcystins (MCs), are produced by over 40 cyanobacterial species found in harmful algal blooms (HABs) worldwide, with MC-LR being the most common and potent MC congener. In the current study, we hypothesized that the low-dose chronic ingestion of Microcystis cyanotoxins via drinking water would promote liver carcinogenesis in pre-initiated mice. Four groups of C3H/HeJ mice received one intraperitoneal (i.p.) injection of diethylnitrosamine (DEN) at 4 weeks of age. Three weeks later, the mice were administered ad libitum drinking water containing one of the following: (1) reverse osmosis, deionized water; (2) water containing 500 mg/L phenobarbital (PB500); (3) water with purified MC-LR (10 µg/L) added; or (4) water containing lysed Microcystis aeruginosa (lysate; 10 µg/L total MCs). The exposure concentrations were based on environmentally relevant concentrations and previously established Ohio EPA recreational water MC guidelines. Throughout the 30-week exposure, mouse weights, food consumption, and water consumption were not significantly impacted by toxin ingestion. We found no significant differences in the number of gross and histopathologic liver lesion counts across the treatment groups, but we did note that the PB500 group developed lesion densities too numerous to count. Additionally, the proportion of lesions classified as hepatocellular carcinomas in the MC-LR group (44.5%; p < 0.05) and lysate group (55%; p < 0.01) was significantly higher compared to the control group (14.9%). Over the course of the study, the mice ingesting the lysate also had a significantly lower survival probability (64.4%; p < 0.001) compared to water (96.8%), PB500 (95.0%), and MC-LR (95.7%) exposures. Using cyanotoxin levels at common recreational water concentration levels, we demonstrate the cancer-promoting effects of a single cyanotoxin MC congener (MC-LR). Furthermore, we show enhanced hepatocarcinogenesis and significant mortality associated with combinatorial exposure to the multiple MCs and bioactive compounds present in lysed cyanobacterial cells—a scenario representative of the ingestion exposure route, such as HAB-contaminated water and food.

Comprehensive assessment of heavy metals contamination in soil and water in peri-urban areas of National Capital Territory, Delhi

Contamination of soil and irrigation water by heavy metals (HMs) is a genuine concern due to the possible effect on human well-being via food chain. Thus, an assessment was carried out to find HMs concentration level in water and soil samples of peri-urban areas of National Capital Territory (NCT) Delhi. Analytical results revealed that significant amount of HMs concentration were found in irrigation water, out of which concentrations of Cu (2590 ?g/L), Fe (5549 ?g/L), Cr (1910 ?g/L), Mn (2570 ?g/L), Zn (2155 ?g/L) and Cd (405 ?g/L) in drain water were exceeded the permissible limit of FAO. Cu (108.94 ?g/g) and Pb (163 ?g/g) concentration in surface soils of majority of sites were recorded beyond the permissible limit of FAO. The overall mean HMs concentration in soil found in the sequence Zn&gt;Cu&gt;Fe&gt;Mn&gt;Cr&gt;Ni&gt;Pb&gt;Cd. It reveals that increasing trend of HMs concentration in water used for irrigation results in metal accumulation in soil, and their consequent accrual in the crops lead to adverse impact on human well-being.

Design of Bridge Type C-Band Planar RF Sensor for Detection of Solute Concentration Level in Water

In this paper, a planar Micro-strip-based bridge topology CSRR is proposed for the detection of various solute concentrations in water sample. The designed bridge topology CSRR (B-CSRR) sensors resonates at 5.18 GHz with a Q-factor of 170, which exhibits a fractional sensitivity (10.17%). To avoid the contamination of test liquids, use of the thin Teflon layer is incorporated on top of the sensor region. The numerical analysis of the sensors for various scenarios including the sensor loaded with several lossy samples are carried out and accordingly shift in resonant frequency is recorded. The optimized design topology helps to attain better electric field confinement at the resonant frequency, which eventually leads to improved dielectric sensitivity. In the next part, an equivalent circuit of the proposed sensor is developed using the Advanced Design System (ADS) software. Afterwards, the designed sensor is fabricated on 0.8mm thick Taconic TLY-5 substrate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\varepsilon }_{r}$ </tex-math></inline-formula> = 2.2). Finally, the measurement of B-CSRR sensor is carried out for different solute concentration in pure water, which is in present scenario are salt and detergent concentration, respectively. The developed sensor is found to be quite sensitive which produces a substantial change in the measured insertion loss even for small variation in solute concentration. For instance, a typical 2% variation in detergent, and salt concentration leads to nearly 1.5 dB, and 2.0 dB, change in measured S21.

Preliminary results on the uptake and biochemical response to water-exposure of Tamiflu® (oseltamivir phosphate) in two marine bivalves

ABSTRACTTamiflu® (oseltamivir phosphate, OST) is an antiviral drug used for the pandemic treatment of avian influenza but few data are available regarding its toxicity. It should be noted that acute adverse responses are not likely to occur due to low environmental presence of this drug. Nonetheless, water concentration levels of this compound may reach the µg/L range under influenza episodes. Bivalves are reliable sentinels of chemical exposure due to their low metabolism; however, biotransformation of drugs does occur in these aquatic invertebrates. Two species of bivalves, namely mussels Mytilus galloprovincialis and clams Ruditapes philippinarum, were exposed for 48 h to 100 µg/L OST. Hemolymph from control and treated bivalves was withdrawn and the presence of OST and its metabolite oseltamivir carboxylate (OST-C) determined by LC-MS/MS. Gills and digestive gland were excised from control and exposed bivalves and carboxylesterase (CE) activities measured using different substrates. In addition, antioxidant defences and lipid peroxidation levels were determined. Higher metabolism of OST seemed to occur in mussels, since both OST and OST-C were found in hemolymph, whereas in clams only the parent compound was detected. In contrast, biomarker responses were more evident in exposed clams which indicate that this species may be considered as more sensitive to OST exposure. CE-related activities successfully reflected OST exposure, with substrates 1-naphthyl acetate (1NA) and 1-naphthyl butyrate (1NB) displaying the highest sensitivity in the two bivalve species. Data thus indicate the usefulness of CE-related activities as biomarkers for OST exposure in bivalves.

Experimental Investigation on a Diesel Engine Fueled by Diesel-Biodiesel Blends and their Emulsions at Various Engine Operating Conditions

The present work aims to investigate emulsion fuel characteristics with different levels of water concentration and their effects on performance and emissions of a light-duty diesel engine. The engine was operated at three engine speeds of 1000, 2100 and 3000rpm, respectively. At each speed, three loads (20%, 50%, and 80%) were applied. Diesel and biodiesel-diesel blends up to 40 by step of 10 were emulsified with three different levels of water concentration (5%, 10% and 15%). Emulsifiers Sorbitan Monoleate (Span 80) and Polyoxyethylene Sorbitan Monoleate (Tween 80) were used to prepare emulsion fuels. Fuel properties, stability and particle size distribution were measured. Engine performance (brake-specific fuel consumption (BSFC) and brake thermal efficiency (BTE)) and emissions were investigated. An increase in BTE was observed with increased water content in emulsions. A reduction in exhaust gas temperature (EGT) with an increase in water content was achieved. The nitrogen oxides (NOx) and smoke emissions were also significantly reduced with the increase in water content in the emulsion compared to their bases. Emulsion fuel containing a higher water content revealed a considerable increase in carbon monoxide (CO) emissions.

Geochemistry and sources of fluoride and nitrate contamination of groundwater in Lar area, south Iran.

Groundwater quality in bone-dry and semiarid areas of Iran is decreasing because of contaminants from natural origins and anthropogenic sources. Among many harmful contaminants, nitrate and fluoride ions are more common. This study was carried out with the aim of determining geochemical processes controlling chemistry of groundwater with special reference to nitrate and fluoride enrichment in groundwater in Lar plain aquifer, south of Iran. Groundwater samples were collected from 17 sites and analyzed for main constituents (Na, K, Ca, Mg, Cl, SO42-, HCO3-, F-, and NO3-). Composite diagram, saturation indices calculation, and multivariate analysis techniques including cluster and factor analyses were employed in evaluating groundwater quality. The EC ranges from 8793.87 to 13,345.00μS/cm in wet season and from 9621.59 to 12,640.00μS/cm in dry season. Fluoride amounts range between 0.59 and 3.92mg/L. Nitrate concentrations range between 1.47 and 70.66mg/L. Results indicate that dissolution-precipitation of carbonate and evaporate minerals, evaporation (in terms of agricultural water return), and opposite ion interchange are the main processes that determine groundwater chemistry. It seems that fluoride has a natural origin and the equilibrium reaction between fluorite and calcite is very significant to control fluoride concentration level in water. Vertical variation of nitrate concentration and distribution of agricultural areas have indicated that nitrate originated from nitrogenous inorganic fertilizers used during irrigation periods. The results also indicate that denitrification takes place in the aquifer and that nitrate decline is not only a function of dilution but also a process of denitrification.

Variability in Levels of Heavy Metals in Water and Fish (Chrysichthys nigrodigitatus) tissues from Badagry Creek, Nigeria

The occurrence of metals viz., lead (Pb), zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd) and chromium (Cr) in water and fish ( Chrysichthys nigrodigitatus) samples collected bi-monthly from nine stations (water) and 3 designated landing sites (fish) of Badagry creek were investigated using atomic absorption spectrophotometer (AAS) method. With an exception of cadmium, metals concentration was lower in the water samples and higher in the fish tissues, indicating a bioaccumulation tendency of fish. Concentration levels in water were found in decreasing order of magnitude Cr &gt; Pb &gt; Fe &gt; Zn &gt; Cu &gt; Cd. However, metals investigated except Cu (highest concentration in the liver) had highest concentrations in the fish gills, which could be related to the uptake pathway. The relatively lower wet season Cu, Pb, Cr and Cd in water could be attributed to a dilution effect of rainfall. Although, presently the mean concentrations of all the heavy metals except Pb in this study were moderate and within the Federal Environmental Protection Agency (FEPA) permissible standard limit for aquatic life , the elevation of metal concentrations in this creek is inevitable under the prevailing conditions of increasing urbanization, industrialization and other forms of modernization in Badagry and environs. Nevertheless, it is imperative to ensure regular monitoring of heavy metal loading in this creek and other water bodies with a view to safeguard public health.

Catalytic transfer hydrogenation for stabilization of bio-oil oxygenates: Reduction of p-cresol and furfural over bimetallic Ni–Cu catalysts using isopropanol

γ-Alumina and carbon supported mono and bimetallic Ni and Cu catalysts were synthesized and applied to the reduction of p-cresol and furfural via transfer hydrogenation. The developed reaction system was applied to alkyl phenol rich pyrolysis oils produced from the ARS tail gas reactive pyrolysis (TGRP) of switchgrass and oak wood. The catalysts used were characterized pre- and post-reactions using XRD, TPR, TEM and TGA. When isopropanol was used as the hydrogen donor solvent, yields of >95% of a mixture of products from the reduction of p-cresol were achieved using the Ni–Cu/Al2O3 catalyst. This product mixture includes ring hydrogenation products (4-methylcyclohexanol and 4-methylcyclohexanone) as well as deoxygenated products (methylcyclohexane and toluene), with 4-methylcyclohexanol being the major product. The activity remained high in the presence of water with very high levels of water concentration resulting in a higher selectivity towards the ketone product. The system was also effective for the reduction of furfural to furfuryl alcohol, although lower temperatures were required to prevent polymerization of the furfural. When applied to bio-oil, although increases in H/C and C/O ratios and energy content were realized, effective reduction of the alkyl phenols in the bio-oils was below expectation. Rather, solid formation, a result of the polymerization of bio-oil compounds was also observed. Our effort to extend the successes encountered with the model compounds to improve the application of transfer hydrogenation to real bio-oils is the subject of ongoing research.

Priority and emerging flame retardants in rivers: Occurrence in water and sediment, Daphnia magna toxicity and risk assessment

The occurrence, partitioning and risk of eight polybrominated diphenyl ethers (PBDEs), nine new brominated (NBFRs) and ten organophosphorus flame retardants (OPFRs) were evaluated in three Spanish rivers suffering different anthropogenic pressures (Nalón, Arga and Besòs). OPFRs were ubiquitous contaminants in water (ΣOPFRs ranging from 0.0076 to 7.2μgL−1) and sediments (ΣOPFRs ranging 3.8 to 824μgkg−1). Brominated flame retardants were not detected in waters, whereas ΣPBDEs ranged from 88 to 812μgkg−1 and decabromodiphenyl ethane (DBDPE) reached 435μgkg−1 in sediments from the River Besòs, the most impacted river. The occurrence of flame retardants in river water and sediment was clearly associated with human activities, since the highest levels occurred near urban and industrial zones and after wastewater treatment plants discharge. Daphnia magna toxicity was carried out for OPFRs, the most ubiquitous flame retardants, considering individual compounds and mixtures. Toxicity of nine tested OPFRs differed largely among compounds, with EC50 values ranging over three magnitude orders (0.31–381mgL−1). Results evidenced that these compounds act by non-polar narcosis, since their toxicity was proportional to their lipophilicity (Kow). Furthermore, their joint toxicity was additive, which means that single and joint toxicity can be predicted knowing their concentration levels in water using quantitative structure activity relationships (QSARs) and predictive mixture models. Based on these results, a risk assessment considering joint effect was performed calculating and summing risk quotients (RQs) for the water and sediment samples. No significant risk to D. magna (ΣRQs <1) was observed for any of the monitored rivers.

Effects of Water Contamination of Lubricants on Hydrodynamic Lubrication: Rheological and Thermal Modeling

Even if water has more favorable thermal characteristics than oil, its use in the realm of bearings is still restricted to some rare applications. Moreover, the presence of water in lubricating circuits is seen as not at all desirable. The contamination of oil by water results in dangerous effects on lubrication. In relation to this, the study of thermal enhancement that this contamination can provide is seen to be insignificant. The literature demonstrates the damaging effects of this type of contamination. However, the existing studies are commonly based on an analysis of the results obtained after a bearing failure. The present study evaluates the instantaneous effect of the water-oil mixture on hydrodynamic lubrication for significant levels of water concentration, up to 10% by mass. The aim of the work is to identify the conditions for which the presence of water is detrimental in lubrication. Such conditions could then be avoided and a new generation of lubrication circuits could be designed to be immune against water contamination. Moreover, any positive effects of water contamination on lubrication deserve to be studied, the possibility being that new lubricant concepts might emerge. Thus, the rheological behavior and thermal characteristics of the mixture (density, specific heat, and thermal conductivity) were numerically modeled and simulations of bearings operating with this mixture were performed. The lubrication characteristics were also measured on a tilting pad thrust bearing, similar effects to those obtained numerically being observed. The presence of water has a slight effect on lubrication, which is nevertheless recognized to amount to an improvement in the lubrication characteristics. In fact, it is found that pure oil could be replaced by a water-in-oil emulsion having the same viscosity. In this case, the film thickness and the friction coefficient will be weakly modified, whereas the bearing will run at a lower temperature. From the point of view of safety, this indicates a significant advantage in operating conditions.

The influence of water on butanol isomers pervaporation transport through polyethylene membrane

Pervaporation transport of binary mixtures of four butanol isomers (n-butanol, sec-butanol, iso-butanol and tert-butanol) with water through polyethylene membrane was studied. The pervaporation experiments were performed with butanol–water binary mixtures of wide concentration range and at different temperatures.The effects of temperature, feed composition and molecular shape of the permeating species on pervaporation characteristics were investigated. The obtained results shown that in comparison with pure butanols, the butanol permeation fluxes initially steeply decreases with increase of water concentration in the feed but then at higher water concentration levels. In the case of higher content of water in mixtures (15–95wt.%) they remained practically constant. It was found that the butanol fluxes decrease in the following order: sec-butanol, n-butanol, tert-butanol to iso-butanol.Butanol diffusivities with small increase of water concentration in the feed increase only slightly, for higher water concentration they appear approximately concentration independent. From the comparison of butanol isomers flux and diffusivity it follows that diffusivity decreases as expected with decreasing of “linearity” of butanol molecules in the sequence –n-butanol, sec-butanol, iso-butanol and tert-butanol.The temperature dependencies of butanol isomers sorption in polyethylene membrane were measured and compared. The sorption of isomers corresponds to their vapor pressure – the sorption amount decreases from tert-butanol, sec-butanol, iso-butanol to n-butanol.Calculated butanol fluxes using the first Fick’s law under the assumption constant diffusion coefficient and equilibrium concentration of permeant at the feed side of the membrane are in very good agreement with experimental values.

Water Circulation, Sediment Transport, and Pollutant Dynamics in Southern Iberia Waters: A Review on Numerical Modelling Studies

Southern Iberian Peninsula coastal waters have a high ecologic and economic value. The objective of this work has consisted of describing numerical models which simulate the dispersion of particle-reactive tracers in these waters and reproducing measured concentration levels in water and bed sediment samples. Additionally, information on suspended matter concentration distributions and sedimentation rates is obtained. In the Alboran Sea, the model has been applied to simulate the transport of radionuclides introduced from atmospheric fallout. Transport pathways of heavy metals discharged from three rivers draining a large mining area have been obtained for the Gulf of Cadiz. It has been found that these rivers constitute a source of trace elements to the Mediterranean through the Strait of Gibraltar. Some characteristic times have been calculated, as well as fluxes of isotopes through the Strait of Gibraltar, as additional results of environmental interest.

Automated dynamic headspace followed by a comprehensive two-dimensional gas chromatography full scan time-of-flight mass spectrometry method for screening of volatile organic compounds (VOCs) in water

This article describes an effective full scan new analytical approach for target and non-target screening of volatile organic compounds (VOCs) in water based on an automatic dynamic headspace (DHS) sampler followed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOF-MS). The operational parameters of DHS having influence on the extraction efficiency of water samples were optimized. The performance of a developed method by DHS-GCxGC-TOFMS was assessed with special attention to the capability of an enhanced separation and reliable identification at a trace concentration level in water. For this purpose, 31 target compounds including non-halogenated, mono-, di-, tri- and tetra-halogenated VOCs were selected. DHS-GCxGC-TOFMS allowed fast and automated analysis of VOCs at a level of parts per trillion, with no matrix interference in the different types of water analyzed (drinking water-tap, and bottled, river water and sea water) and with a minimum sample preparation. Excellent method detection and quantification limits were achieved, ranging from 0.01 to 10 ng L−1 and from 0.02 to 34 ng L−1, respectively. Good linearity (r2 > 0.99), intra and inter-day repeatability (<30%) were obtained for most of the target analytes denoting the suitability of the method for quantifying VOCs and its potential use in a routine setting. This method was successfully applied to real samples. Full mass range TOFMS acquisition allowed for positive identification of both targets, through mass spectral matching to database standards, and non-targeted compounds (dichloroiodomethane and dichloroacetonitrile). Trihalomethanes, tetrachloroethene, benzene, toluene ethylbenzene and xylenes (BTEXs) were the most frequently detected contaminants in the water samples analyzed. Mean concentrations of VOCs ranged from 65–439 ng L−1 in sea water, 29–1626 ng L−1 in bottled water, 17–16 312 ng L−1 in river water and 51–54 460 ng L−1 in tap water. The feasibility of using effective software data was very useful to rapidly sort information about the presence of VOCs in water and pattern recognition.

Electrochemical Determination of Trihalomethanes in Water by Means of Stripping Analysis

A protocol has been developed and evaluated for the determination of trihalomethanes (THMs) at the submicromolar concentration level in water. This method is based on a three-step stripping analysis that utilizes a single electrochemical cell and that entails (a) direct electrochemical reduction of a trihalomethane at a silver cathode to form halide ions in an aqueous sample containing tetraethylammonium benzoate, (b) capture of the released halide ions as a silver halide film on the surface of a silver gauze anode, and (c) cathodic reduction and quantitation of the silver halide film by means of differential pulse voltammetry. Using this procedure, we have determined THMs individually; bromoform and chloroform have been successfully quantitated in 30 min and with a detection limit of 3.0 μg L(-1) (12 nM) and 6.0 μg L(-1) (50 nM), respectively. In addition, we have employed our methodology to determine the total trihalomethane (TTHM) content in a prepared water sample at a level commensurate with the maximum allowable annual average of 80 μg L(-1) mandated by the United States Environmental Protection Agency. We have compared our TTHM results to those obtained by an independent testing laboratory.