Evaluation of preconcentration methods in the analysis of synthetic musks in whole‐water samples

According to the European Water Framework Directive, environmental assessment of organic compounds should be made in whole‐water samples, but due to their hydrophobicity and strong attraction to organic content these compounds can be found bound to suspended particle matter or in the dissolved fraction. In this work, the extraction of musk compounds was studied in whole‐water samples exhibiting different amounts of dissolved organic carbon and suspended particulate matter using polyethersulfone preconcentration technique. Matrix effects in estuarine and wastewater (both influent and effluent) were evaluated for filtered and unfiltered samples. For unfiltered samples, estuarine water exhibited matrix effects <20%, while for effluent it was up to 48% and for influent ranged from 85 to 99%. To compensate matrix effects and determine total concentrations in unfiltered samples, different quantification approaches were tested: the use of deuterated analogues and standard additions. Standard additions provided the best results for unfiltered samples. Finally, filtered and unfiltered samples were analyzed using both polyethersulfone preconcentration and membrane‐assisted solvent extraction and results showed a good agreement between the two methods. In both cases unfiltered samples provided concentrations 1.5–2.6 times higher than filtered samples.     

Spatial and temporal variations of the inherent and apparent optical properties in a shallow coastal lake

Apparent and inherent optical properties in the coastal lagoon of Fogliano were measured in three seasonal surveys in 2002. Irradiance data from in situ measurements of ultraviolet and visible wavebands permitted to estimate the related attenuation coefficients. Laboratory extinction measurements on filtered (0.22 microm) and unfiltered water samples were also performed. The integrated approach between in situ and laboratory measurements allowed the determination of the role of the suspended and dissolved matter in the attenuation and extinction of ultraviolet and visible radiation within the water column. As noted, the impact of the suspended and dissolved matter on the lake optical quality was influenced by wind resuspension of particulate matter: the relative role of dissolved matter in the absorption of UV and visible radiation was prevailing at low wind velocity conditions (less than 2.2 m s(-1)), while at high wind velocities (3.9 m s(-1)), particulate matter resuspension strongly influenced the attenuation and the extinction measurements. The extinction in the analyzed wavelengths of filtered and unfiltered water samples and the in situ irradiance measurements allowed us to define new optical parameters and important correlations with limnological and classical optical measurements. By sampling at high spatial resolution (18 stations in 4 km2), it was possible to evidence a spatial gradient of the optical and limnological properties, these distributions showed a consistent pattern in all three surveys, and were important for the characterization of the chromophoric dissolved organic matter that was estimated with the spectral slope of the extinction curve spectra. A relatively higher spectral slope was found in the southern basin with respect to the northern, where the maximum values of the attenuation coefficients and limnological parameters were found. These results suggest different sources of dissolved organic matter and/or a different level of photobleaching.     

Modelling spatial and temporal variations in the water quality of an artificial water reservoir in the semiarid midwest of Argentina

Temporal and spatial patterns of water quality of an important artificial water reservoir located in the semiarid Midwest of Argentina were investigated using chemometric techniques. Surface water samples were collected at 38 points of the water reservoir during eleven sampling campaigns between October 1998 and June 2000, covering the warm wet season and the cold dry season, and analyzed for dissolved oxygen (DO), conductivity, pH, ammonium, nitrate, nitrite, total dissolved solids (TDS), alkalinity, hardness, bicarbonate, chloride, sulfate, calcium, magnesium, fluoride, sodium, potassium, iron, aluminum, silica, phosphate, sulfide, arsenic, chromium, lead, cadmium, chemical oxygen demand (COD), biochemical oxygen demand (BOD), viable aerobic bacteria (VAB) and total coliform bacteria (TC). Concentrations of lead, ammonium, nitrite and coliforms were higher than the maximum allowable limits for drinking water in a large proportion of the water samples. To obtain a general representation of the spatial and temporal trends of the water quality parameters at the reservoir, the three-dimensional dataset (sampling sites×parameters×sampling campaigns) has been analyzed by matrix augmentation principal component analysis (MA-PCA) and N-way principal component analysis (N-PCA) using Tucker3 and PARAFAC (Parallel Factor Analysis) models. MA-PCA produced a component accounting for the general behavior of parameters associated with organic pollution. The Tucker3 models were not appropriate for modelling the water quality dataset. The two-factor PARAFAC model provided the best picture to understand the spatial and temporal variation of the water quality parameters of the reservoir. The first PARAFAC factor contains useful information regarding the relation of organic pollution with seasonality, whereas the second factor also encloses information concerning lead pollution. The most polluted areas in the reservoir and the polluting sources were identified by plotting PARAFAC loadings as a function of the UTM (Universal Transverse Mercator) coordinates.     

Flow Injection Analysis Using Potassium Permanganate: An Approach for Measuring Chemical Oxygen Demand in Organic Wastes and Waters

Abstract

A rapid and continuous analytical method based on flow injection analysis was developed for the determination of chemical oxygen demand due to organic substances in water pollution. Potassium permanganate and sulfuric acid solutions were individually pumped up as an oxidizing agent and glucose was used as a standard substance. The results for filtered organic waste and water samples were as reasonable as compared to those measured by the manual acidic permanganate method.     

Heavy metal levels and physico--chemical quality of potable water supply in Warri, Nigeria

The interaction between man's activities and the environment is gaining world wide attention. Warri an oil producing community in Delta State of Nigeria is faced with environmental oil pollution. Since open and underground water bodies are regarded as final recipients of most environmental pollutants, this study sought to provide data on the levels of the physico-chemical parameters and contaminants in Warri metropolitan water supply. This study investigated the cadmium, lead and chromium using Atomic Absorption Spectrophotometer, physico-chemical properties such as pH, temperature, total suspended solid TSS, total dissolved solid TDS, electrical conductivity EC, biological oxygen demand BOD, dissolved oxygen DO, chemical oxygen demand COD, and total coliform count of potable water sources in Warri. Ekpan River was found to have 1.2 mg/L of cadmium, 1.0 mg/L of chromium, 1.20 mg/L of lead and 2.0 mg/L of manganese. The heavy metals levels and the pollution parameters were lowest in the borehole water samples, except pH which is more acidic in borehole water samples and conductivity which is more in well water samples in all the sampling stations. Some of the parameters were above WHO standards.     

Structural effects on biodegradation of aliphatic polyesters

Various types of aliphatic polyesters were prepared by both biosynthetic and chemosynthetic methods, and their biodegradation tests were carried out under aerobic conditions in the river water. Biodegradabilities of polyester films were evaluated by monitoring the time-dependent changes in the biochemical oxygen demand (BOD), weight loss (erosion) of polyester film, and dissolved organic carbon concentration (DOC) of test solution. The microbial copolyesters were degraded in the river water at a rapid rate, and the weight-loss- and BOD-biodegradabilities of the majority of biosynthetic polyesters were 100 % and 80±5 % for 28 days, respectively. In contrast, the biodegradabilities of chemosynthetic polyesters were strongly dependent of the chemical structure of monomeric units.     

A solid composite electrode for the determination of the electrochemical oxygen demand of aqueous samples

A composite electrode containing graphite, paraffin, AgO and CuO is described for the determination of the electrochemical oxygen demand (EOD) of waste waters. The oxidation of dissolved organic compounds at the electrode is based on a heterogeneous chemical reaction of AgO/CuO with the organic constituents of the waste water. This chemical reaction can be followed by a solid state electrochemical oxidation of the formed Ag₂O/Cu₂O. The method has been tested with various organic compounds and applied to real samples of sewage water. The EOD values correlate well to BOD and COD values.     

Needs for reliable analytical methods for monitoring chemical pollutants in surface water under the European Water Framework Directive

The state of the art in monitoring chemical pollutants to assess water quality status according to Water Framework Directive (WFD) and the challenges associated with it have been reviewed. The article includes information on environmental quality standards (EQSs) proposed to protect the aquatic environment and humans against hazardous substances and the resulting monitoring requirements. Furthermore, minimum performance criteria for analytical methods and quality assurance issues have been discussed. The result of a survey of existing standard methods with a focus on European (EN) and international standards (ISO) for the analysis of chemical pollutants in water is reported and the applicability of those methods for the purpose of compliance checking with EQSs is examined. Approximately 75% of the 41 hazardous substances for which Europe-wide EQSs have been proposed can be reliably monitored in water with acceptable uncertainty when applying existing standardised methods. Monitoring in water encounters difficulties for some substances, e.g., short-chain chlorinated paraffins (SCCPs), polybrominated diphenyl ethers (PBDEs), tributyltin compounds, certain organochlorine pesticides and six-ring PAHs, mainly due to a lack of validated, sufficiently sensitive methods that are applicable in routine laboratory conditions. As WFD requires monitoring of unfiltered samples for organic contaminants more attention needs to be paid to the distribution of chemical pollutants between suspended particulate matter and the liquid phase. Methods allowing complete extraction of organic contaminants from whole water samples are required. From a quality assurance point of view, there is a need to organise interlaboratory comparisons specifically designed to the requirements of WFD (concentrations around EQSs, representative water samples) as well as field trials to compare sampling methodologies. Additional analytical challenges may arise when Member States have identified their river basin specific pollutants and after revision of the list of priority substances.     

北海半岛水体混合过程的稀土元素分布特征

选择北海半岛南流江河口、半岛近岸海域及涠洲岛附近海域为对象,研究河海水混合过程中稀土元素的某些地球化学特征。结果表明,水体中稀土元素主要以悬浮颗粒态存在,溶解态稀土含量及轻、重稀土含量之比从河流到海洋逐渐降低。溶解态稀土含量在南流江河口低盐度区因胶体絮凝而下降,在中高盐度区,颗粒物解吸或部分溶解引起含量上升;pH值对其亦有影响。溶解态稀土分布模式以重稀土相对富集为特征,在此基础上存在中稀土富集,是源区铁锰氧化物和水体中有机胶体共同作用的结果,Ce正异常与水体中有机物有关,Eu负异常是对源区岩石分布模式特征的继承。而原水中稀土含量变化相对复杂,与水动力状况有关,分布模式较为一致,表明河流颗粒物存在均一化趋势。     

Studies on the sea surface microlayer. II. The layer of sudden change of physical and chemical properties

Seawater samples of the sea surface microlayer were obtained from the ocean, coastal waters, and laboratory imitation experiments adopting glass plate, rotating drum, screen, and funnel samplers. The result was that surface microlayer samples of thickness 50 microm could be taken, not by the popular screen and funnel techniques, but by glass plate or rotating drum techniques. The layer of sudden change of physical and chemical properties in the surface microlayer was found at 50 microm below the sea-air interface. These physical and chemical properties included tens of physical and chemical parameters, such as concentrations of organic matter, nutrients, and dissolved trace metals, biochemical oxygen demand, chemical oxygen demand chlorophyll-a, surface tensions, and pH. Therefore, it was suggested that the layer of sudden change of physical and chemical properties in surface seawater should serve as a basis for defining the sea surface microlayer should, and be regarded as the practical operational thickness of the sea surface microlayer. The apparent sampling thickness of the sea surface microlayer from surface seawater should be 50+/-10 microm.     

The presence of trace phosphine in Lake Taihu water

Phosphine (PH₃) is a natural constituent in phosphorus (P) chemical cycles. The discovery of phosphine will shed new light on the mechanisms of P supplement and biogeochemical cycles. Since phosphine is converted to phosphate after complex oxidation via hypophosphite and phosphite, if it were present in the water column, understanding its production and emission could enhance our understanding of P speciation.

Assuming that phosphine in the gas phase is an ideal gas and at equilibrium between water and gas interface, phosphine in water solution can be quantified from the equilibrated concentration in gas phase using the Henry's Law. Application of this approach to Lake Taihu, China, phosphine in unfiltered and filtered water samples (0.45 μm) was analysed. Results showed that phosphine was universally present in Lake Taihu water. Phosphine concentration in unfiltered water ranged from 0.16 to 1.11 pg L^?1, and was much less (0.01 to 0.04 pg L^?1) in filtered samples. Over 90% of phosphine was adsorbed onto or incorporated into suspended materials with <10% dissolved in the water. Higher phosphine concentrations could be observed in warm seasons. Positive relationships were found between PH₃ and TP (average R ² = 0.59 ± 0.22) and TSP (average R ² = 0.37 ± 0.13).     

紫外光谱水质分析仪中的支持向量机方法

紫外光谱水质分析仪的一个关键技术是如何建立紫外光谱数据与有机污染物浓度之间的数学模型,以及提高模型的外推能力。本研究基于统计学习理论的支持向量机方法,提出了有机污染物浓度与紫外光谱数据的建模方法。该方法具有较强的推广能力和全局最优的特点,得到的数学模型的预测能力明显改善,从而提高了紫外光谱水质分析仪的测量精度。实验表明：该方法优越于目前在紫外光谱水质分析仪中常规采用的偏最小二乘算法。     

Strategies for monitoring the emerging polar organic contaminants in water with emphasis on integrative passive sampling

Although polar organic contaminants (POCs) such as pharmaceuticals are considered as some of today's most emerging contaminants few of them are regulated or included in on-going monitoring programs. However, the growing concern among the public and researchers together with the new legislature within the European Union, the registration, evaluation and authorisation of chemicals (REACH) system will increase the future need of simple, low cost strategies for monitoring and risk assessment of POCs in aquatic environments. In this article, we overview the advantages and shortcomings of traditional and novel sampling techniques available for monitoring the emerging POCs in water. The benefits and drawbacks of using active and biological sampling were discussed and the principles of organic passive samplers (PS) presented. A detailed overview of type of polar organic PS available, and their classes of target compounds and field of applications were given, and the considerations involved in using them such as environmental effects and quality control were discussed. The usefulness of biological sampling of POCs in water was found to be limited. Polar organic PS was considered to be the only available, but nevertheless, an efficient alternative to active water sampling due to its simplicity, low cost, no need of power supply or maintenance, and the ability of collecting time-integrative samples with one sample collection. However, the polar organic PS need to be further developed before they can be used as standard in water quality monitoring programs.     

Chemiluminescence method with potassium permanganate for the determination of organic pollutants in seawater.

A chemiluminescence method with potassium permanganate was developed for use as an indicator of organic pollutants in fresh water. This method could be applied to the determination of organic pollutants in seawater as well. However, the flow chemiluminescence method suffered from the interference of chloride ions at the same concentration of seawater because of the production of manganese dioxide in the oxidation of chloride ions with permanganate. The conditions (concentrations of potassium permanganate and sulfuric acid and sample volume, i.e. flow injection method) were chosen to minimize the interference of chloride ions. The chemiluminescence method shows a good correlation with the chemical oxygen demand method on fresh water added artificial sea salt and seawater samples. Natural seawater was analyzed by the chemiluminescence method. The results obtained were compared with those obtained by chemical oxygen demand under the alkaline condition and total organic carbon methods. The chemiluminescence method has higher sensitivity and reproducibility than the conventional chemical oxygen demand and total organic carbon methods.     

Environmetric modeling and interpretation of river water monitoring data

This environmetric study deals with modeling and interpretation of river water monitoring data from the basin of the Saale river and its tributaries the Ilm and the Unstrut. For a period of one year of observation between September 1993 and August 1994 a data set from twelve campaigns at twenty-nine sampling sites from the Saale river and six campaigns from the river Ilm at seven sampling sites and from river Unstrut at ten sampling sites was collected. Twenty-seven chemical and physicochemical properties were measured to estimate the water quality. The application of cluster analysis, principal components analysis, and apportioning modeling on absolute principal components scores revealed important information about the ecological status of the region of interest:identification of two separate patterns of pollution (upper and lower stream of the rivers);identification of six latent factors responsible for the data structure with different content for the two identified pollution patterns; anddetermination of the contribution of each latent factor (source of emission) to the formation of the total concentration of the chemical burden of the river water.As a result more objective ecological policy and decision making is possible.     

Freshwater quality in urban areas: a case study from Rome, Italy

Water quality in streams running in urban areas can be strongly altered by the impact of human activities. Different kinds of water quality degradation were investigated in the streams running in the ‘Appia Antica’ Regional Park, placed in the southern suburbs of Rome. Water quality was assessed in 21 sampling points located in eight streams by the analysis of chemical [chemical oxygen demand (COD), nitrates, ammonia, total phosphorus], biological (IBE index), microbial (total coliforms, faecal coliforms, Escherichia coli, faecal streptococci, sulphite-reducing clostridia) ecosystemic (IFF index), and hydrological (flow) parameters. On the whole the results indicate an in depth degradation of water quality. However, IBE and IFF showed local condition of water stress that were not individuated by chemical parameters. A multidisciplinary approach is necessary to highlight the different pressures on water quality of urban freshwaters. The presence of buffer zones in urban green areas does not avoid the impact arising from the surrounding urban area.     

A rapid analytical method for predicting the oxygen demand of wastewater

In this study, an investigation was undertaken to determine whether the predictive accuracy of an indirect, multiwavelength spectroscopic technique for rapidly determining oxygen demand (OD) values is affected by the use of unfiltered and turbid samples, as well as by the use of absorbance values measured below 200 nm. The rapid OD technique was developed that uses UV–Vis spectroscopy and artificial neural networks (ANNs) to indirectly determine chemical oxygen demand (COD) levels. It was found that the most accurate results were obtained when a spectral range of 190–350 nm was provided as data input to the ANN, and when using unfiltered samples below a turbidity range of 150 NTU. This is because high correlations of above 0.90 were obtained with the data using the standard COD method. This indicates that samples can be measured directly without the additional need for preprocessing by filtering. Samples with turbidity values higher than 150 NTU were found to produce poor correlations with the standard COD method, which made them unsuitable for accurate, real-time, on-line monitoring of OD levels.     

光化学降解溶解有机物及其对生物过程的影响

溶解有机物对控制海洋和淡水水生系统的化学、生物和物理特性有重要的影响.光化学降解溶解有机物改变了生态体系的溶解有机碳、有机物的分子量及光学特性,并且产生复杂的反应性氧化合物、二氧化碳、一氧化碳、小分子量的有机酸、氨基酸、二硫化碳等,对生物过程有重要的影响.本文简要综述了光化学降解溶解有机物的过程机理及其对生物过程的影响.     

Determination of chemical oxygen demand of nitrogenous organic compounds in wastewater using synergetic photoelectrocatalytic oxidation effect at TiO2 nanostructured electrode

Chemical oxygen demand (COD) is one of the most important parameters in water quality assessment and monitoring. The natural degradation of nitrogenous organic compounds (NOCs) in water requires significant amounts of oxygen. In the determination of standard COD however, NOCs are persistent compounds that cannot be completely oxidized even in the most oxidative chemical environments, i.e. the reaction media that contain high concentrations of dichromate in strong acid at high temperature. Consequently, the measured COD values of wastewater samples containing NOCs are commonly lower than theoretical COD values and do not reflect the actual oxygen demand of the water body. This problem is partially alleviated when the photoelectrochemical method for COD determination (PeCOD) based on nanostructured TiO₂ photoanode is utilized. To completely overcome this problem, a synergetic photoelectrochemical oxidation effect in thin layer cells is used to achieve complete oxidation of NOCs. This is done by the simple addition of a hydroxyl organic compound (i.e. glucose) into the test sample before the PeCOD measurement. Preliminary experimental results demonstrate that the synergetic PeCOD method provides an effective and reliable means to measure COD values of NOC-containing pollutants without the need for toxic or expensive reagents.     

Electrothermal atomic absorption determination of ultratraces of suspended and dissolved species of elements in natural water

Direct and adsorption-atomic absorption procedures are proposed for the determination of suspended and dissolved species of elements in natural water. The procedures involve the fractional vaporization of solid samples (suspensions or adsorbent concentrates) in a graphite crucible atomizer with the simultaneous condensation of filtered and unfiltered element vapors on the surfaces of graphite rods placed above and below the crucible. The obtained microsample condensates were analyzed by independently heating the vaporization and atomization zones and localizing the element vapors in the isothermal analytical zone. The proposed approach makes it possible to use and compare various methods for suppressing matrix interference in a single analysis and to improve the performance characteristics of element determination.