Water Analysis: Emerging Contaminants and Current Issues

Database and review of disinfection by-products since 1974: Constituent elements, molecular weights, and structures

Since trihalomethanes were discovered in 1974, disinfection by-products (DBPs) in drinking water have attracted extensive attention. In 2011, more than 600 known DBPs were compiled; however, newly reported DBPs have not been integrated. The rapid development of mass spectrometry has led to a significant increase in the number of DBPs, therefore, there is a need to develop a database of all DBPs and their properties. Herein, a database including 6310 DBPs (651 confirmed, 1478 identified and 4142 proposed) reported between 1974 and 2022 was constructed and made available for public use at https://dbps.com.cn/main. This database can be a tool in screening new DBPs, comprehensively reviewing, and developing predictive models. In this paper, to demonstrate the functions of the database and provide useful information for this area, the origin of the collected DBPs was presented, and some basic information, including elemental composition, molecular weight, functional groups, and carbon frameworks, were comparatively analyzed. The results showed that the proportion of DBPs verified by standard compounds and frequently detected in real water is less than 7.0%, and most of DBPs remained to be identified. Approximately 88% of DBPs contain halogens, and brominated -DBPs occupied a similar ratio to chlorinated -DBPs in real water. Acids were the main functional groups of DBPs, aliphatic and aromatic compounds are the two major carbon frameworks, and the molecular weights of most DBPs ranged from 200 to 400 Da. In addition, 4142 proposed DBPs as obtained using high-resolution mass spectrometry, were characterized based on the modified van Krevelen diagram and adjusted indexes with halogens. Most of the proposed DBPs featured lignin and tannin structures, and phenolic/highly unsaturated DBPs account for the majority.

Effects of the endocrine disruptor 4-nonylphenol on the demography of rotifers Plationus patulus and Brachionus havanaensis: a multigenerational study

The emerging contaminant 4-nonylphenol is an active ingredient in many surfactants. Though 4-nonylphenol has been reported in Mexican waterbodies, no stringent law is available to establish its permissible limits. Most ecotoxicological assays using zooplankton species are based on previously unexposed populations, and multigenerational experiments are rare. Plationus patulus and Brachionus havanaensis are widely distributed species in Mexico and have been used in ecotoxicological assessments. In this work, the median lethal concentration of 4-nonylphenol (LC₅₀, 24 h) for both rotifer species was derived. Based on our acute toxicity data (24 h LC₅₀ of 4-nonylphenol for P. patulus and B. havanaensis were 500 and 250 µg L^-1, respectively), three sublethal concentrations (µg L^-1) (7.81, 15.82 and 31.25 for B. havanaensis and 15.62, 31.25 and 62.5 for P. patulus) were used in the life table demography tests for two successive generations (F0 and F1) of either rotifer species. Regardless of the concentrations used, 4-nonylphenol had an adverse effect on both rotifer species over two successive generations. P. patulus was more sensitive than B. havanaensis in chronic toxicity tests. F1 generation of both rotifer species was far more adversely affected than the F0 in all toxicant treatments.

Method Development for Assessing Carbamazepine, Caffeine, and Atrazine in Water Sources from the Brazilian Federal District Using UPLC-QTOF/MS

About 3.0 million people living under a typical tropical savannah climate in the Brazilian Federal District (FD) have faced an unprecedented water crisis. Considering the need for indirect reuse of wastewater for public supply, this work aimed to investigate FD water sources regarding the presence and risks of three contaminants of emerging concern: caffeine, carbamazepine, and atrazine. Samples from two current water sources (Descoberto and Santa-Maria Lakes) and two future water sources of the FD (Paranoá and Corumbá Lakes) were analyzed by solid-phase extraction followed by liquid chromatography coupled to hybrid quadrupole-time-of-flight mass spectrometry (UPLC-QTOF/MS). Method precision and accuracy were satisfactory and limits of quantification ranged from 0.37 to 0.54 ng/L. Higher concentrations were observed for caffeine in the future water sources (39 to 180 ng/L) followed by carbamazepine (5.4 to 25 ng/L) and atrazine (3.9 to 15 ng/L). The less-impacted water sources, in current use in the FD, present caffeine concentrations ranging from 4.8 to 32 ng/L and atrazine levels varying between 2.4 and 5.5 ng/L. Carbamazepine was not detected in these reservoirs. Environmental risk assessment indicates a possible risk for carbamazepine and atrazine, evidencing the need for further studies. No human health risk was depicted within the results.

Highly efficient inactivation of bacteria found in drinking water using chitosan-bentonite composites: Modelling and breakthrough curve analysis

Disinfection of bacterially-contaminated drinking water requires a robust and effective technique and can be achieved by using an appropriate disinfectant material. The advanced use of nanomaterials is observed as an alternative and effective way for the disinfection process and water treatment as a whole. Hence, the inactivation of Escherichia coli (E. coli) using chitosan-Bentonite (Cts-Bent) composites was studied in a fixed bed column. Cts-Bent composites were synthesized using in situ cross-linking method using Bent-supported silver and zinc oxide nanoparticles. These composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The effect of the composite bed mass, initial concentration of bacteria, and flow rate on the bacterial inactivation was investigated. The characterization results revealed that the composites were successfully prepared and confirmed the presence of both silver and zinc oxide nanoparticles in the chitosan matrix. The growth curves of E. coli were expressed as breakthrough curves, based on the logistic, Gompertz, and Boltzmann models. The breakthrough time and processed volume of treated water at breakthrough were used as performance indicators, which revealed that the composites performed best at low bacterial concentration and flow rate and with substantial bed mass. The chitosan composites were found to be highly effective, which was demonstrated when no bacteria were observed in the effluent sample within the first 27 h of analysing river water. All the models were suitable for adequately describing and reproducing the experimental data with a sigmoidal pattern. Therefore, the prepared composite is showing potential to work as a disinfectant and provide an alternative solution for water disinfection; hence this study should propel further research of the same or similar materials.

Toxicological perturbations of zinc oxide nanoparticles in the Coelatura aegyptiaca mussel

More research is needed to understand the interactions of nanoparticles (NPs) with aquatic organisms and their mechanism of toxic action. Zinc oxide nanoparticles (ZnONPs) are the most used engineered metal oxide NPs in consumer products. The present study was designed to evaluate the cytotoxicity, genotoxicity and digestive gland (DG) as well as gill histopathology of the freshwater molluscan bivalve Coelatura aegyptiaca following exposure to ZnONPs (2, 10 and 50 mg/L) for 6 consecutive days. Exposure to ZnONPs (10 and 50 mg/L) induced a significant increase in malondialdehyde, superoxide dismutase and nitric oxide with a concomitant decrease in reduced glutathione, glutathione-S-transferase and catalase levels in the haemolymph, DG and gills of the treated mussels. Following exposure to ZnONPs (50 mg/L), the DG exhibited gradual changes in glandular activity showing hypertrophy and hyperplasia in the glandular cells and irregularity of lamellae and swelling of filaments in the gills. The present investigation revealed that oxidative stress induction, genotoxicity in the haemocytes and histological alterations in the DG and gills of C. aegyptiaca could be the main mechanisms involved in ZnONPs toxicity in aquatic organisms. Thereby, it is suggested that ZnONPs should be applied with more precautions in relevant industries, and occupational health surveillance should be necessarily considered.

A new approach for trace analysis of guanidine compounds in surface water with resorcinarene-based ion chromatography columns

Trace levels of pharmaceuticals have been detected in surface water and may pose a health risk to humans and other organisms. New chromatographic materials will help identify and quantify these contaminants. We introduce a new ion chromatographic (IC) material designed to separate cationic pharmaceuticals and report its ability to separate a group of guanidine compounds. Guanidine moieties are strongly basic and protonated under acid conditions, and therefore can potentially be separated on the newly designed stationary phase and detected by ion exchange chromatography. The new column packing material is based on glutamic acids bonded to resorcinarene moieties that in turn are bound to divinylbenzene macroporous resin. Detection limits in the range of 5-30 μg L(-1) were achieved using integrated pulsed amperometric detection (IPAD) for guanidine (G), methylguanidine (MG), 1,1-dimethylbiguanide (DMG), agmatine (AGM), guanidinobenzoic acid (GBA) and cimetidine (CIM). Suppressed conductivity (CD) and UV-vis detection resulted in limits of detection similar to IPAD, in the range of 2-66 μg L(-1), but were not able to detect all of the analytes. Three water sources, river, lake, and marsh, were analyzed and despite matrix effects, sensitivity for guanidine compounds was in the 100 μg L(-1) range and apparent recoveries were 80-96%. The peak area precision was 0.01-2.89% for IPAD, CD and UV-vis detection.

Impact of treated wastewater reuse and floods on water quality and fish health within a water reservoir in an arid climate

Treated wastewater (TWW) reuse for agricultural irrigation is a well-established approach to coping with water shortages in semi-arid and arid environments. Recently, additional uses of TWW have emerged, including streamflow augmentation and aquatic ecosystem restoration. The purpose of the current study was to evaluate the water quality and fish health, in an artificial reservoir located in an arid climate (the Yeruham Reservoir, Israel), which regularly receives TWW and sporadic winter floods. The temporal distribution of water levels, nutrients and organic micropollutants (OMPs) were measured during the years 2013-2014. OMPs were also measured in sediment and fish tissues. Finally, the status of fish health was evaluated by histopathology. Water levels and quality were mainly influenced by seasonal processes such as floods and evaporation, and not by the discharge of TWW. Out of 16 tested OMPs, estrone, carbamazepine, diclofenac and bezafibrate were found in the reservoir water, but mostly at concentrations below the predicted no-effect concentration (PNEC) for fish. Concentrations of PCBs and dioxins in fish muscle and liver were much lower than the EU maximal permitted concentrations, and similar to concentrations that were found in food fish in Israel and Europe. In the histopathological analysis, there were no evident tissue abnormalities, and low to moderate infection levels of fish parasites were recorded. The results from the Yeruham Reservoir demonstrated a unique model for the mixture effect between TWW reuse and natural floods to support a unique stable and thriving ecosystem in a water reservoir located in an arid region. This type of reservoir can be widely used for recreation, education, and the social and economic development of a rural environment, such as has occurred in the Yeruham region.

Arsenic contamination, consequences and remediation techniques: a review

The exposure to low or high concentrations of arsenic (As), either due to the direct consumption of As contaminated drinking water, or indirectly through daily intake of As contaminated food may be fatal to the human health. Arsenic contamination in drinking water threatens more than 150 millions peoples all over the world. Around 110 millions of those peoples live in 10 countries in South and South-East Asia: Bangladesh, Cambodia, China, India, Laos, Myanmar, Nepal, Pakistan, Taiwan and Vietnam. Therefore, treatment of As contaminated water and soil could be the only effective option to minimize the health hazard. Therefore, keeping in view the above facts, an attempt has been made in this paper to review As contamination, its effect on human health and various conventional and advance technologies which are being used for the removal of As from soil and water.

WITHDRAWN: Formation of TCNM from polyDADMAC during UV irradiation combined with chlorination treatment

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The fate and importance of organics in drinking water treatment: a review

In the pioneer days, the main driving forces for research of organics in drinking water treatment (DWT) were human health risks and optimisation of technology. The focus was on natural organic matter (NOM) structure, disinfection by-products (DBPs) formation, NOM removal by means of coagulation, adsorption, and oxidation, and development of the most efficient water treatment trains. Surprisingly, after decades of research, rapid development of analytical techniques and progress in risk assessment, the same driving forces are still in the limelight - although the topics have changed slightly. The attention switched from trihalomethanes to a new generation of DBPs. The definition of hydrophilic/hydrophobic NOM depends on the technique used for characterisation. It has become evident that numerous organic compounds can threaten water supply sources. Some of them had been ignored or overlooked in the past, but have recently been detected by advanced analytical tools even in drinking water. Prioritisation becomes priority per se. As far as processes are concerned, mainstream research has been following three lines: fouling mechanisms, application of hybrid processes and interactions between synthetic organic chemicals, other water constituents and materials used in DWT. Significant development has been made in membrane technology. This paper presents a broad overview of the recent organics research. Although the state-of-the-art technologies seem to have an answer to each and every question raised, it is still necessary to deal with specific problems on a case-by-case basis mainly due to the unique nature of NOM and different xenobiotics that may appear in various types of waters. In the end, human health risk, which derives from the presence/absence of organics, is only the tip of the iceberg - underneath lies a whole new universe - the socio-economic aspect of water treatment and quality that deserves much more attention.

Emerging contaminants of public health significance as water quality indicator compounds in the urban water cycle

The contamination of the urban water cycle (UWC) with a wide array of emerging organic compounds (EOCs) increases with urbanization and population density. To produce drinking water from the UWC requires close examination of their sources, occurrence, pathways, and health effects and the efficacy of wastewater treatment and natural attenuation processes that may occur in surface water bodies and groundwater. This paper researches in details the structure of the UWC and investigates the routes by which the water cycle is increasingly contaminated with compounds generated from various anthropogenic activities. Along with a thorough survey of chemicals representing compound classes such as hormones, antibiotics, surfactants, endocrine disruptors, human and veterinary pharmaceuticals, X-ray contrast media, pesticides and metabolites, disinfection-by-products, algal toxins and taste-and-odor compounds, this paper provides a comprehensive and holistic review of the occurrence, fate, transport and potential health impact of the emerging organic contaminants of the UWC. This study also illustrates the widespread distribution of the emerging organic contaminants in the different aortas of the ecosystem and focuses on future research needs.

Ecotoxicological effect of sublethal exposure to zinc oxide nanoparticles on freshwater snail Biomphalaria alexandrina

Freshwater snails are used as sensitive biomarkers of aquatic ecosystem pollution. The potential impacts of zinc oxide nanoparticles (ZnONPs) on aquatic ecosystems have attracted special attention due to their unique properties. The present investigation was designed to evaluate the possible mechanisms of ecotoxicological effects of ZnONPs on freshwater snail Biomphalaria alexandrina. ZnONPs showed molluscicidal activity against B. alexandrina snails, and the LC50 was 145 μg/ml. Two tested concentrations of ZnONPs were selected: The first concentration was equivalent to LC10 (7 μg/ml), and the second was equivalent to LC25 (35 μg/ml). Exposure to ZnONPs (7 and 35 μg/ml) for three consecutive weeks significantly induced malondialdehyde and nitric oxide with concomitant decreases in glutathione and glutathione-S-transferase levels in hemolymph and soft tissues of treated snails. Moreover, ZnONPs elicited a significant decrease in total protein and albumin contents coinciding with enhancement of total lipids and cholesterol levels as well as activities of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in hemolymph and soft tissues of treated snails. This study highlights the potential ecological implications of ZnONP release in aquatic environments and may serve to encourage regulatory agencies in Egypt to more carefully monitor and regulate the industrial use and disposal of ZnONPs.

Solid phase microextraction (SPME) combined with TGA as a technique for guest analysis in crystal engineering

Guest identification using SPME – a technique for analysis of TGA off-gas that eliminates the need for direct TGA-GC/MS coupling.

Photodegradation of Trace Trichloronitromethane in Water under UV Irradiation

This study’s objective was to study the photodegradation of TCNM (trichloronitromethane) in water under UV light. The effects of light intensity, nitrate ions, chloride ions, humic acid, and pH on the photochemical degradation of TCNM were investigated under the irradiation of low pressure mercury lamp (λ= 254 nm, 12 W). The photodegradation rate of TCNM was found to increase with increasing the concentration of nitrate ions, chloride ions, humic acid, pH, and light intensity. The photodegradation of TCNM was examined at pH 6.0 with initial concentrations (C0) of TCNM at 10.0–200.0 µg/L. The overall rate of degradation of TCNM was modeled using a pseudofirst-order rate law. Finally, the proposed mechanism involved in the photodegradation of TCNM was also discussed by analysis. Results of this study can contribute to the development of new source control strategies for minimization of TCNM risk at drinking water and wastewater utilities.

Recent advances in drinking water disinfection: successes and challenges

Drinking water is the most important single source of human exposure to gastroenteric diseases, mainly as a result of the ingestion of microbial contaminated water. Waterborne microbial agents that pose a health risk to humans include enteropathogenic bacteria, viruses, and protozoa. Therefore, properly assessing whether these hazardous agents enter drinking water supplies, and if they do, whether they are disinfected adequately, are undoubtedly aspects critical to protecting public health. As new pathogens emerge, monitoring for relevant indicator microorganisms (e.g., process microbial indicators, fecal indicators, and index and model organisms) is crucial to ensuring drinking water safety. Another crucially important step to maintaining public health is implementing Water Safety Plans (WSPs), as is recommended by the current WHO Guidelines for Drinking Water Quality. Good WSPs include creating health-based targets that aim to reduce microbial risks and adverse health effects to which a population is exposed through drinking water. The use of disinfectants to inactivate microbial pathogens in drinking water has played a central role in reducing the incidence of waterborne diseases and is considered to be among the most successful interventions for preserving and promoting public health. Chlorine-based disinfectants are the most commonly used disinfectants and are cheap and easy to use. Free chlorine is an effective disinfectant for bacteria and viruses; however, it is not always effective against C. parvum and G. lamblia. Another limitation of using chlorination is that it produces disinfection by-products (DBPs), which pose potential health risks of their own. Currently, most drinking water regulations aggressively address DBP problems in public water distribution systems. The DBPs of most concern include the trihalomethanes (THMs), the haloacetic acids (HAAs), bromate, and chlorite. However, in the latest edition of the WHO Guidelines for Drinking Water Quality, it is recommended that water disinfection should never be compromised by attempting to control DBPs. The reason for this is that the risks of human illness and death from pathogens in drinking water are much greater than the risks from exposure to disinfectants and disinfection by-products. Nevertheless, if DBP levels exceed regulatory limits, strategies should focus on eliminating organic impurities that foster their formation, without compromising disinfection. As alternatives to chlorine, disinfectants such as chloramines, ozone, chlorine dioxide, and UV disinfection are gaining popularity. Chlorine and each of these disinfectants have individual advantage and disadvantage in terms of cost, efficacy-stability, ease of application, and nature of disinfectant by-products (DBPs). Based on efficiency, ozone is the most efficient disinfectant for inactivating bacteria, viruses, and protozoa. In contrast, chloramines are the least efficient and are not recommended for use as primary disinfectants. Chloramines are favored for secondary water disinfection, because they react more slowly than chlorine and are more persistent in distribution systems. In addition, chloramines produce lower DBP levels than does chlorine, although microbial activity in the distribution system may produce nitrate from monochloramine, when it is used as a residual disinfectant, Achieving the required levels of water quality, particularly microbial inactivation levels, while minimizing DBP formation requires the application of proper risk and disinfection management protocols. In addition, the failure of conventional treatment processes to eliminate critical waterborne pathogens in drinking water demand that improved and/or new disinfection technologies be developed. Recent research has disclosed that nanotechnology may offer solutions in this area, through the use of nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, and nanoparticle-enhanced filtration.

Prioritizing research for trace pollutants and emerging contaminants in the freshwater environment

Organic chemicals have been detected at trace concentrations in the freshwater environment for decades. Though the term trace pollutant indicates low concentrations normally in the nanogram or microgram per liter range, many of these pollutants can exceed an acceptable daily intake (ADI) for humans. Trace pollutants referred to as emerging contaminants (ECs) have recently been detected in the freshwater environment and may have adverse human health effects. Analytical techniques continue to improve; therefore, the number and frequency of detections of ECs are increasing. It is difficult for regulators to restrict use of pollutants that are a human health hazard; scientists to improve treatment techniques for higher priority pollutants; and the public to modify consumption patterns due to the vast number of ECs and the breadth of literature on the occurrence, use, and toxicity. Hence, this paper examines literature containing occurrence and toxicity data for three broad classes of trace pollutants and ECs (industrials, pesticides, and pharmaceuticals and personal care products (PPCPs)), and assesses the relevance of 71 individual compounds. The evaluation indicates that widely used industrials (BPF) and PPCPs (AHTN, HHCB, ibuprofen, and estriol) occur frequently in samples from the freshwater environment but toxicity data were not available; thus, it is important to establish their ADI. Other widely used industrials (BDE-47, BDE-99) and pesticides (benomyl, carbendazim, aldrin, endrin, ethion, malathion, biphenthrin, and cypermethrin) have established ADI values but occurrence in the freshwater environment was not well documented. The highest priority pollutants for regulation and treatment should include industrials (PFOA, PFOS and DEHP), pesticides (diazinon, methoxychlor, and dieldrin), and PPCPs (EE2, carbamazepine, βE2, DEET, triclosan, acetaminophen, and E1) because they occur frequently in the freshwater environment and pose a human health hazard at environmental concentrations.

Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective

Although N-nitrosodimethylamine (NDMA) has been the most prevalent N-nitrosamine detected in disinfected waters, it remains unclear whether NDMA is indeed the most significant N-nitrosamine or just one representative of a larger pool of N-nitrosamines. A widely used assay applied to quantify nitrite, S-nitrosothiols, and N-nitrosamines in biological samples involves their reduction to nitric oxide by acidic tri-iodide, followed by chemiluminescent detection of the evolved nitric oxide in the gas phase. We here describe an adaptation of this method for analyzing total N-nitrosamine (TONO) concentrations in disinfected pools. Optimal sensitivity for N-nitrosamines was obtained using a reduction solution containing 13.5 mL glacial acetic acid and 1 mL of an aqueous 540 g/L iodide and 114 g/L iodine solution held at 80 degrees C. The method detection limit for N-nitrosamines was 110 nM using 100 microL sample injections and NDMA as a standard. N-nitrosamines featuring a range of polarities were converted to nitric oxide with 75-103% efficiency compared to NDMA. Evaluation of potential interfering species indicated that only nitrite and S-nitrosothiols were a concern, but both interferences were effectively eliminated using group-specific sample pretreatments previously employed for biological samples. To evaluate the low TONO concentrations anticipated for pools, 1 L samples were extracted by continuous liquid-liquid extraction with ethyl acetate for 24 h, and concentrated to 1 mL. N-nitrosamine recovery during extraction ranged from 37-75%, and there was a potential for artifactual nitrosation of amines during solvent reflux in the presence of significant nitrite concentrations, but not at the low nitrite concentrations prevalent in most pools. Using the 1000-fold concentration factor and 56% average extraction efficiency, the method detection limit would be 62 pM (5 ng/L as NDMA). The TONO assay was applied to six pools and their common tap water source in conjunction with analysis for specific nitrosamines. Even accounting for the range of N-nitrosamine extraction recoveries, NDMA accounted for an average of only 13% (range 3-46%) of the total nitrosamine pool.

N-nitrosodimethylamine (NDMA) removal by reverse osmosis and UV treatment and analysis via LC-MS/MS

N-nitrosodimethylamine (NDMA) is a probable human carcinogen found in ng/l concentrations in chlorinated and chloraminated water. A method was developed for the determination of ng/l levels of NDMA using liquid chromatography-tandem mass spectrometry (LC-MS/MS) preceded by sample concentration via solid-phase extraction with activated charcoal. Recoveries were greater than 90% and allowed a method reporting limit as low as 2ng/l. Using this method, the removal of NDMA was determined for the Interim Water Purification Facility (IWPF), an advanced wastewater treatment facility operated by the Orange County Water District (OCWD) in Southern California. The facility treats effluent from an activated sludge treatment plant with microfiltration (MF), reverse osmosis (RO), and an ultraviolet-hydrogen peroxide advanced oxidation process (UV-AOP). Six nitrosamines were surveyed: NDMA, N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPip), and N-nitrosopyrrolidine (NPyr). Only NDMA was detected and at all treatment steps in the IWPF, with influent concentrations ranging from 20 to 59 ng/l. Removals for RO and UV ranged from 24% to 56% and 43% to 66%, respectively. Overall, 69+/-7% of the original NDMA concentration was removed from the product water across the advanced treatment process and, in combination with blending, the final concentration did not exceed the California drinking water notification level of 10 ng/l. NDMA removal data are consistent with findings reviewed for other advanced treatment facilities and laboratory studies.

Monensin is not toxic to aquatic macrophytes at environmentally relevant concentrations

Monensin, a common livestock feed additive, has been detected in surface waters around areas of intensive agriculture. The effect of this ionophore antibiotic on floating (Lemna gibba) and submersed (Myriophyllum spicatum, Elodea canadensis, Egeria densa) freshwater macrophytes was investigated under seminatural field conditions using 12,000 l of outdoor microcosms. Exposure concentrations of 0, 12, 25, 50, and 100 mug/l (n = 3) were evaluated over a 35-day period. Submersed plants were grown individually in 115-ml plastic "cone-tainers" and assessed for various growth and pigment end points. E. canadensis and M. spicatum also were grown in assemblages to represent model populations and two-species communities. Few statistically significant differences from control organisms were observed for any of the monitored end points. Overall, monensin is deemed unlikely to cause toxicity in freshwater macrophytes at current environmental concentrations. However, the ability to characterize toxicity in macrophytes is based partially on the relative growth rates (RGRs) of the plants. The greater the RGR, the more sensitive the assay may be to contaminants. The RGRs of E. canadensis and M. spicatum grown in model populations and communities were found to be significantly higher than the RGRs of plants grown individually. This implies that the "cone-tainer" method, although simple and easy to perform, may underestimate toxicity in simulated field studies.

Investigation of retention behaviour of non-steroidal anti-inflammatory drugs in high-performance liquid chromatography by using quantitative structure–retention relationships

In this paper, a quantitative structure-retention relationship (QSRR) method is employed to model the retention behaviour in reversed-phase high-performance liquid chromatography of arylpropionic acid derivatives, largely used non-steroidal anti-inflammatory drugs (NSAIDs). Computed molecular descriptors and the organic modifier content in the mobile phase are associated into a comprehensive model to describe the effect of both solute structure and eluent composition on the isocratic retention of these drugs in water-acetonitrile mobile phases. Multilinear regression (MLR) combined with genetic algorithm (GA) variable selection is used to extract from a large set of computed 3D descriptors an optimal subset. Based on GA-MLR analysis, a five-dimensional QSRR model is identified. All the four selected molecular descriptors belong to the category of GEometry, Topology, and Atom-Weights AssemblY (GETAWAY) descriptors. The related multilinear model exhibits a quite good fitting and predictive performance. This model is further improved using an artificial neural network (ANN) learned by error back-propagation. Finally, the ANN-based model displays a remarkably better performance as compared with the MLR counterpart and, based on external validation, is able to predict with good accuracy the behaviour of unknown arylpropionic NSAIDs in the range of mobile phase composition of analytical interest (between 35 and 75% acetonitrile (v/v)).

ESI-MS analyses of lake dissolved organic matter in light of supramolecular assembly

A high-performance size-exclusion chromatography (SEC) system was coupled on-line to an electrospray ionization (ESI) interface to detect gas-phase ions by an API 365 LC/MS/MS triple quadrupole analyzer. The SEC fractions of a strongly coloured freshwater solution containing dissolved organic matter-humic substances (DOM-HS) were screened both by UV(254) and by ESI mass spectrometry (ESI-MS) in the full-scan mode within the m/z range of 100-2,900 amu in negative and positive polarities. The ESI-MS spectra were also collected by direct infusion of the DOM-HS solution in both polarities. ESI-MS spectra did not primarily favour low mass compounds, and negative and positive total ion chromatograms were parallel to the SEC elution profile obtained by UV(254) detection from DOM-HS solution. The UV(254) detection overestimated the SEC portion of higher size/mass solutes and underestimated that of solutes of smaller sizes/masses as compared with the total ion chromatogram intensities in negative or positive polarities. The change of mass-weighted and number-weighted average sizes/masses (M(w) and M(n)) of different SEC fractions was fairly small, in contrast to UV(254) detection, with increasing elution volume. A reasonable explanation for the great differences between M(w) and M(n) values, obtained by UV(254) and ESI-MS detections for eight different SEC fractions, seems to be a supramolecular-type association of relatively small components through weak dispersive forces. M(n) values obtained by vapour-pressure osmometry for different SEC fractions were to some extent analogous with those of negative and positive ESI-MS. The shapes obtained by either negative or positive polarities and calculated M(w) and M(n) values indicated a close structural similarity between each SEC fraction. Positive ion and negative ion spectra of different humic fractions represented quite similar components, and there was no evidence for noteworthy occurrence of multiply charged ions being able to lower mass distributions of negative ion spectra. The effect of nitrogen on the mass spectra seemed to be unimportant, and the weak ions observed at even m/z values correspond most likely to the (13)C counterparts of the more abundant (12)C odd ions. No uncontrolled ESI fragmentation was observable and humic solutes seemed to be quite heat-resistant. Direct infusion of the untreated DOM-HS solution and statistical calculation verified that the SEC-separated different fractions really represent distinct entities of the original DOM-HS mixture. ESI-MS results support the opinion that the structural composition of humic solutes in their original combined mixture resembles supramolecular-type associations of smaller molecular size entities possessing similar structural functionalities.

Review of kinetics of chemical and photocatalytical oxidation of Arsenic(III) as influenced by pH

The kinetics and stoichiometry of As(III) oxidation by chemical oxidants is presented. The reactions are first-order with respect to each reactant. The second-order rate constants vary with pH and have a range in magnitude of 10(4)-10(7) M-1 s-1 for free available chlorine (FAC), O3, and FeO4(2-) in a pH range of 6.0-9.0. In this pH range, the reactions of As(III) with chloroamine (NH2Cl) and H2O2 are quite slow with rate constants of 2.9-4.3x10(-1) M-1 s-1 and 2.6x10(-2)-4.5x10(1) M-1 s-1 for chloroamine and H2O2, respectively. The pH dependence of the oxidation reactions can be described using acid-base equilibria of both As(III) species and the oxidant. FAC, O3, and FeO(4)2- oxidize As(III) instantaneously at pH 7.0 with half-lives of milliseconds if 2 mg/L excess dose of oxidant is applied. One major advantage of FeO4(2-) ions over the other oxidants is its ability to remove arsenic in water by two mechanisms; it oxidizes As(III) and also subsequently coagulates As(V) through Fe(III) hydroxide produced from Fe(VI) reduction. Photocatalytic oxidation of As(III) to As(V) follows zero-order kinetics and the oxidation is completed in minutes with no significant pH dependence. The removal of dissolved arsenic to values below the World Health Organization drinking water limit of 10 microg/L can be achieved through photocatalytic oxidation of As(III) to As(V) in acidic solution followed by adsorption of As(V) onto TiO2 surfaces.

Potential sources of background contaminants in solid phase extraction and microextraction

A study to identify the sources of background contamination from SPE, using a C-18 sorbent, and solid-phase microextraction (SPME), using a 70 microm carbowax/divinylbenzene (CW/DVB) fiber, was carried out. To determine the source of contamination, each material used in the procedure was isolated and examined for their contribution. The solid-phase column components examined were: sorbent material and frits, column housings and each solvent used to elute analytes off the column. The components examined in the SPME procedure were: SPME fiber, SPME vials, water (HPLC grade), and salt (sodium chloride) used to increase the ionic strength. The majority of the background contaminants from SPE were found to be from the SPE sorbent material and frits. The class of contaminants extracted during a blank extraction were phthalates and other plasticizers used during the manufacturing process. All had blank levels corresponding to measured concentrations below 2 ng/ mL, except for undecane, which had a concentration of 5.4 ng/mL. The most prevalent contaminants in the SPME blank procedure are 1,9-nonanediol, a mixture of phthalates and highly bis-substituted phenols. All the concentrations were below 2 ng/mL, with the exception of bis (2-ethylhexyl) phthalate, which had concentrations ranging from 5 to 20 ng/mL.

Rapid on-plate and one-pot derivatization of carbonyl compounds for enhanced detection by reactive matrix LDI-TOF MS using the tailor-made reactive matrix, 4-dimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-hydrazine (DMNTH)

In this study, a very sensitive and economical high-throughput methodology has been developed for the analysis of small carbonyl compounds using rapid derivatization with 4-dimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-hydrazine (DMNTH), a derivatizing agent developed by the Karst group at the University of Münster. DMNTH is highly ionizable by the UV laser and reacts selectively and rapidly with carbonyl moieties. The resulting hydrazone is easily detectable by laser desorption ionization time of flight mass spectrometry (LDI-TOF MS), eliminating the need for the matrix assisted variant (MALDI) and the associated issue of matrix optimization, which greatly simplifies the analysis. It has been demonstrated that a range of carbonyl compounds can be conveniently analyzed by this reactive matrix LDI-TOF MS (RM-LDI-TOF MS) procedure and that furfural DMNThydrazone (prior labeled and labeled in situ) can be used as an internal standard for semiquantitative analysis. Amounts as low as 0.5 ng ml(-1) of 4-methoxybenzaldehyde have been detected using a one-pot derivatization methodology. Rapid on-plate derivatization was also found to be a simple approach for fast and reliable screening of various analytes, although with slightly higher detection limits. To test its applicability in complex matrices, analysis of furfural spiked in beer has been demonstrated. This RM-LDI-TOF MS method shows considerable promise for the analysis of carbonyl compounds in water, particularly for disinfection by-products that result from reaction of natural organic matter with oxidative disinfectants.

A preliminary study on the occurrence and behavior of sulfonamides, ofloxacin and chloramphenicol antimicrobials in wastewaters of two sewage treatment plants in Guangzhou, China

Wastewater samples collected from two sewage treatment plants (STPs) in Guangzhou, China were acidified, solid-phase extracted (SPE) with Oasis HLB cartridges, followed by instrumental measurement by high performance liquid chromatography (HPLC) coupled with a diode array UV detector (DAD) and a fluorescence detector (FLD) for the occurrence and fate of antimicrobial compounds sulfadiazine (SDZ), sulfamethoxazole (SMX), ofloxacin (OFX) and chloramphenicol (CAP). Antimicrobials have been detected at 5.10-5.15, 5.45-7.91, 3.52-5.56 and 1.73-2.43 microg L(-1) for SDZ, SMX, OFX and CAP in the raw sewages of the two STPs, respectively. The concentrations of antimicrobials do not show substantial changes after preliminary mechanical sedimentation. No quantifiable sulfonamides and chloramphenicol have been identified, and >85% of ofloxacin has been removed in the effluents after activated sludge treatment in the two STPs, indicating that activated sludge treatment is effective and necessary to remove antimicrobial substances in municipal sewage.

On-line immunoaffinity column-liquid chromatography–tandem mass spectrometry method for trace analysis of diuron in wastewater treatment plant effluent sample

An on-line immunoaffinity column with liquid chromatography/tandem mass spectrometry (IAC-LC-MS/MS) method for the determination of diuron in water matrices was described. This method used a sol-gel immunoaffinity column (20 mm x 4 mm I.D.) for on-line sample cleanup and enrichment, a monolithic analytical column (100 mm x 4.6 mm I.D.) for separation, and a triple quadrupole mass spectrometer for quantitation. The major challenges for the on-line set-up were discussed. The optimized on-line protocol was emphasized by the fact that low limit of quantitation (LOQ) of 1.0 ng/L was achieved with only 2.5-mL sample. In addition, a satisfactory accuracy ( approximately 90% of recovery) and precision (<6% of relative standard deviation) at 50 ng/L concentration were also obtained. Due to the ability of the sol-gel immunoaffinity column to eliminate matrix effect, the on-line IAC-LC-MS/MS analysis method can reliably determine diuron in wastewater treatment plant effluent sample.

Ozonation of seawater from different locations: formation and decay of total residual oxidant--implications for ballast water treatment

Ballast water is a likely cause for worldwide transfer of non-indigenous aquatic species because of the large volumes and frequency of possible inoculations. Ozone is one treatment option being considered for eliminating non-indigenous species in ballast water. When ozone is applied to seawater, secondary disinfectants are formed, commonly measured and expressed as total residual oxidant (TRO). The goal of this study was to determine those variables most likely to affect the rate of TRO increase during ozonation and the subsequent TRO decline that occurs over time. These parameters strongly influence the efficacy of ozone treatments aimed to eliminate organisms present in ballast water. Seawater was obtained from Puget Sound, Washington; Cape Fear, North Carolina; and San Francisco Bay. Results indicated that seawater characteristics, including the organic content and ammonia, affect the amount of ozone required to achieve a desired TRO level and rate of TRO decay, and therefore need to be considered in determining ozone requirements for ballast water treatment.

Formation of halogenated by-products of parabens in chlorinated water

Chemical transformations of four alkyl esters of p-hydroxybenzoic acid, parabens, in chlorinated water samples are investigated. Quantification of the parent species and identification of their reaction by-products were performed using gas chromatography in combination with mass spectrometry. Experiments were accomplished considering free chlorine and paraben concentrations at the mg L(-1) and microg L(-1) level, respectively. Concentration of water samples, using solid-phase extraction, and silylation of the target species were carried out in order to improve the detectability of parent species and their possible transformation products, achieving quantification limits at the low ng L(-1) level. Under employed experimental conditions, the decrease in the concentrations of parabens followed pseudo-first-order kinetics. Half-lives values obtained for model ultrapure water solutions were in good agreement with those observed in tap water samples. For the first type of sample, only two by-products were detected for each paraben. They corresponded to chlorination of the aromatic ring in one or two carbons situated in ortho-positions to the hydroxyl group. Both species were also generated after the addition of parabens to chlorinated tap water. Moreover, three new transformation products were noticed for each parent compound. They were identified as bromo- and bromochloro-parabens, formed due to the existence of traces of bromide in tap water sources. Experiments carried out by mixing paraben-containing personal care products with tap water, containing free chlorine, confirmed the formation of all above described halogenated by-products. In addition, the presence of the di-chlorinated forms of methyl and propyl paraben has been detected for first time in raw sewage water samples.

Kinetic and mechanistic investigations of progesterone reaction with ozone

The removal of progesterone by ozone in aqueous solution was studied in this work. The absolute rate constant was evaluated and first by-products were identified. The reaction was studied in the 2.0-8.0 pH range and was found to be a second-order reaction, first-order relative to each compound concentration. The rate constant, determined by kinetic experiments in presence of an OH radical scavenger (tert-butanol), was independent of pH. The value was evaluated to be equal to 480+/-30 M(-1)s(-1) by two kinetic methods. Mass spectrometry analyses were performed to investigate primary degradation products generated by the reaction of ozone with progesterone. Two by-products were evidenced. According to these results, a degradation pathway of progesterone reacting with ozone was proposed.

Different sample stacking strategies to analyse some nonsteroidal anti-inflammatory drugs by micellar electrokinetic capillary chromatography in mineral waters

Three on-column preconcentration techniques were compared to analyse a group of nonsteroidal anti-inflammatory drugs (NSAIDs) using micellar electrokinetic capillary chromatography (MEKC) under pH-suppressed electroosmotic flow (EOF) in water samples. The analysed drugs were ibuprofen, fenoprofen, naproxen, ketoprofen, and diclofenac sodium. The micellar background electrolyte (BGE) solution was formed by 75 mM sodium dodecyl sulfate (SDS), 40% (v/v) acetonitrile, and 25 mM sodium phosphate at pH 2.5. When this BGE solution was used the applied voltage was reversed, -10 kV, and the drugs were separated within 20 min. The on-column preconcentration modes, characterised all of them for the sample matrix removal out of the capillary by itself under a reverse potential at the same time as the EOF was reduced, were stacking with reverse migrating micelles (SRMM), stacking with reverse migrating micelles-anion selective exhaustive injection (SRMM-ASEI), and field-enhanced sample injection with reverse migrating micelles (FESI-RMM). The sensitivity was improved up to 154-, 263-, and 63-fold, respectively when it was calculated through the peaks height. The optimised methods were validated with spiked mineral water by combining off-line solid-phase extraction (SPE) and the proposed on-line sample stacking strategies. The detection limits (LODs) of NSAIDs in mineral water were at ng/L levels.

Determination of TOCl, TOBr and TOI in drinking water by pyrolysis and off-line ion chromatography

The objective of this research was to determine the optimum total organic halogen (TOX) protocol for use with ion chromatographic (IC) detection to analyze total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI) in drinking water simultaneously. Two commercial analyzers (one using a pure O2 carrier and one using O2/CO2 mixture) and three commercially available activated carbons (two coconut-based and one bituminous coal-based) were examined in this study. Results showed that the pyrolytic analyzer using pure O2 and off-line IC combined with a standard TOX carbon (coconut-based) achieved the most complete recovery of TOCl, TOBr and TOI for both model compounds and real samples. There was no obvious difference between the two analyzers when used in microcoulometric detection mode. The TOX method is moderately sensitive to nitrate rinse volume. The monohaloacetic acids were partly washed out during sample preparation. This problem was solved by a modified nitrate rinsing solution.

Analysis of methylglyoxal in water and biological matrices by capillary zone electrophoresis with diode array detection

We describe a new method for the determination of methylglyoxal in water and biological matrices, using o-phenylenediamine as derivatizing agent and solid-phase extraction followed by capillary zone electrophoresis with diode array detection. 25 mM sodium phosphate running buffers at pH 2.2, 30 kV, and 25 degrees C allowed the best instrumental conditions for the optimum separation of methylglyoxal in a suitable analytical time (< 10 min), using an uncoated fused-silica capillary of 75 microm inner diameter and an effective length of 45.1 cm with an extended light path and the wavelength set to 200 nm. Under optimized instrumental conditions, good reproducibility of the migration time (< 1.1%), precision (< 5%), an excellent linear dynamic range from 0.1 to 3.6 mg/L (r(2) = 0.9997), and low limits of detection (7.2 microg/L) were obtained for methylglyoxal measurements, using the internal standard methodology. Assays on laboratory-spiked tap and ground water samples allowed a remarkable accuracy, presenting yields of 95.0 +/- 4.3 and 94.0 +/- 1.1%, respectively, and good performance to determine methylglyoxal in beer and yeast cells suspensions matrices was also obtained at trace level. The present methodology is a cost-effective alternative for routine quality control analysis, showing to be reliable, sensitive, and with a low sample volume requirement to monitor methylglyoxal in water and biological matrices.