Trends of natural organic matter concentrations in river waters of Latvia

This study revealed significant (P?相似文献   

Total organic carbon analyzers as tools for measuring carbonaceous matter in natural waters

For some utilities, new US drinking water regulations may require the removal of disinfection byproduct (DBP) precursor material as a means of minimizing DBP formation. The Environmental Protection Agency's Stage 1 DBP Rule relies on total organic carbon (TOC) concentrations as a measure of the effectiveness of treatment techniques for removing organic material that could act as DBP precursors. Accordingly, precise and accurate methods are needed for the determination of TOC and dissolved organic carbon (DOC) concentrations in raw and finished potable water supplies. This review describes the current analytical technologies and summarizes the key factors affecting measurement quality. It provides a look into the fundamental principles and workings of TOC analyzers. Current peroxydisulfuric acid wet ashing methods and combustion methods are discussed. Issues affecting quality control, such as non-zero blanks and preservation, are covered. Some of the difficulties in analyzing water for TOC and DOC that were identified up to 20 years ago still remain problematic today. Limitations in technology, reagent purity, operator skill and knowledge of natural organic matter (NOM) can preclude the level of precision and accuracy desirable for compliance monitoring.     

The development of a chemical 'fingerprint' to characterise dissolved organic matter in natural waters

A suite of twelve assays has been used to 'fingerprint' dissolved organic matter (DOM). The assays were applied directly to filtered natural water samples. Temperature, pH and conductivity accounted for the environmental conditions on-site. Bulk carbon characteristics were assayed by measuring UV absorbance at 200 and 240 nm, colour in grade Hazen, DOC (dissolved organic carbon), fluorescence (excitation 370 nm, emission 450 nm) and the complexation of phenol itself. Measuring hydroxybenzenes ('monophenolics'), polyhydroxybenzenes ('polyphenolics') and total phenolics with the Gibbs, Prussian Blue and Folin-Ciocalteau assays, respectively, determined the phenolics pool. The methodology was tested on six freshwater sites in North Wales chosen to provide differences in vegetation, land-use and water chemistry and sampled once during each season. A novel approach for the presentation of the data has been developed that combines all range normalised assay results for each site and each season within one polar plot, hence the term 'fingerprint'. The data was also analysed using principal component factor analysis. Assays characterised as determining the chemical properties of DOM contributed to Factor 1 and explained 59% of the variation in the data. Assays apparently determined by the water matrix, contributed to Factor 2 and explained 20% of the variation within the data. The factor scores obtained for each site showed more variation for assays relating to the chemical properties of DOM than to the surrounding water matrix. The methodology was found to detect chemical changes within DOM for each site throughout the year and different responses for different sites.     

饮用水消毒副产物--卤乙酸的检测

卤乙酸是饮用水氯化消毒中一类主要的消毒副产物,由于存在的广泛性和潜在的健康危害,许多国家和卫生组织相继将其列为饮用水常规监测项目,而我国至今还没有相关规定;为了更好地控制饮用水中卤乙酸的形成,世界各国科研人员先后研究和开发出了性能逐趋完善的多种分析检测方法;本文在国内外文献调研的基础上,对卤乙酸的各种分析检测方法进行了简要的介绍,并指明了今后的发展方向.     

Thresholds in eutrophication of natural waters

The population density of bacterioplankton and the concentration of dissolved organic carbon combined is a useful indicator to monitor subtle variations in the amount of eutrophication. Both parameters can be measured precisely and readily by widely accepted routine techniques that require little skill. Thresholds of eutrophication can be established to maintain the Health of Natural Waters using this indicator.     

Chromium redox speciation in natural waters

Dissolved hexavalent chromium concentrations were determined in river, estuarine and coastal waters of the Humber catchment in north-east England. Samples were collected, filtered, extracted on site and after storage for up to eight days. Hexavalent chromium concentrations did not change by more than 0.05 microg l(-1) (not significant, p = 0.05) over this period. Total chromium concentrations in the catchment were less than 1.0 microg l(-1). This is low in relation to the proposed Environmental Quality Standard. Hexavalent chromium accounted for between 27% and 100% of the total dissolved concentration, with an average of approximately 50%. The proportion of Cr(III) and Cr(VI) in the rivers and estuary were of the same range as previously measured in 1993. The addition of Cr(III) and Cr(VI) to fresh and saline water samples illustrates the complexity of the factors controlling chromium speciation in natural waters. The presence of oxidisable organic matter and the stabilising role of complexing organic ligands are proposed as the main controlling influences of redox speciation in filtered samples.     

Chromium fractionation and speciation in natural waters

It is common for leather industries to dump chromium-contaminated effluent into rivers and other bodies of water. Thus, it is crucial to know the impacts caused by this practice to the environment. A study on chromium partitioning and speciation, with determination at trace levels, was carried out in a potentially contaminated creek. Chromium fractionation and speciation was performed using a flow-injection preconcentration system and detection by flame atomic absorption spectrometry. High levels of this element were found in the particulate material (449-9320 mg kg(-1)), which indicates its compatibility with this fraction. The concentration of Cr(iii) in the water samples collected ranged from 5.2-105.2 μg L(-1). Cr(vi) was always below of the DL (0.3 μg L(-1)). Chromium accumulation observed in the sediment (873-1691 mg kg(-1)) may confirm contamination due to the long term release of contaminated effluents in the creek.     

Chemical speciation in natural and brine sea waters

A combined approach consisting of monitoring and thermodynamic modeling was used in order to calculate the concentration of trace element species in water samples of a broad salinity range and to explain their chemical behaviour. The study was performed on water samples (fresh, marine, hyper-saline) taken from the area of Burgas Bay, Bulgaria. The ion association model based on Debye-Hückel theory using the sst2008.dat database and the ion interaction model based on Pitzer theory using a new pit2010.dat database were compared and combined for the purposes of this study. The new pit2010.dat database combines the sst2008.dat database and the pitzer.dat database of the PHREEQCI computer program as well as the thermodynamic data for the elements Fe, Mn, Cu, Zn, Cd and Pb and their Pitzer ion interaction parameters. The results showed that: (1) the predominant species in fresh waters were free ions of Mn(2+) (73.6%), Zn(2+) (58.0%) and Cd(2+) ions (78.3%) as well as carbonate species CuCO?? (81.8%), PbCO?? (77.2%) and hydroxy species Fe(OH) ??(55.2%) and Fe(OH)+?(35.6%); (2) an increase in chloride species MeCl2(n)-(n)(n = 1-4, Me = Mn, Zn, Cu, Pb and Cd) and of the hydroxy species Fe(OH)?? for Fe was calculated for sea and hyper-saline water.     

水体中酚类化合物分光光度分析方法的研究

对国内外水体中酚类化合物现有的分光光度分析方法进行了文献综述 ,内容包括可见光分光光度法、紫外光分光光度法、荧光分光光度法和流动注射分光光度法。在总结归纳的基础上 ,提出了水体中酚类化合物分光光度分析方法的发展方向。     

Monitoring dissolved organic carbon in surface and drinking waters

The presence of natural organic matter (NOM) strongly impacts drinking water treatment, water quality, and water behavior during distribution. Dissolved organic carbon (DOC) concentrations were determined daily over a 22 month period in river water before and after conventional drinking water treatment using an on-line total organic carbon (TOC) analyzer. Quantitative and qualitative variations in organic matter were related to precipitation and runoff, seasons and operating conditions. Following a rainfall event, DOC levels could increase by 3.5 fold over baseflow concentrations, while color, UV absorbance values and turbidity increased by a factor of 8, 12 and 300, respectively. Treated water DOC levels were closely related to the source water quality, with an average organic matter removal of 42% after treatment.     

Interlaboratory comparability of copper complexation capacity determination in natural waters

The results of a test of interlaboratory comparability for the determination of copper complexation capacity and copper-ligand complex formation constant are presented. Eight water samples comprising, six natural waters, a synthetic ligand solution and a blank solution were analysed by seven laboratories using their own methods of complexation titration. Given the wide variation that might have been possible, relatively good comparability was demonstrated amongst the variety of methods for determining copper complexation capacity. The complexation capacity data largely satisfied the predefined criterion of agreement to within 50%. This provides support for the use of metal speciation criteria in the regulation of copper in the environment. Data for the determination of complex formation constants were of poorer comparability, ranging between 10(7) and 10(12) for the same water.     

Formation and modeling of disinfection by-products in drinking water of six cities in China

Water quality parameters including TOC, UV(254), pH, chlorine dosage, bromide concentration and disinfection by-products were measured in water samples from 41 water treatment plants of six selected cities in China. Chloroform, bromodichloromethane, dibromochloromethane, dichloroacetic acid and trichloroacetic acid were the major disinfection by-products in the drinking water of China. Bromoform and dibromoacetic acid were also detected in many water samples. Higher concentrations of trihalomethanes and haloacetic acids were measured in summer compared to winter. The geographical variations in DBPs showed that TTHM levels were higher in Zhengzhou and Tianjin than other selected cities. And the HAA5 levels were highest in Changsha and Tianjin. The modeling procedure that predicts disinfection by-products formation was studied and developed using artificial neural networks. The performance of the artificial neural networks model was excellent (r > 0.84).     

A method for characterising natural and waste waters using plant seeds

Studies were conducted to describe a method for the characterisation of natural and waste waters using plant seed germination as a technique for toxicity testing. Maize seeds were found to be more sensitive to differences in water quality than cowpea seeds and also showed more consistency in results. Trials conducted using natural waters and effluents from gold mining and textile manufacturing operations are also reported.     

Monitoring of eutrophication by microbial uptake kinetics of dissolved organic matter in waters

The monitoring of eutrophication can be performed by measuring the turnover times of amino acids in watermasses using the Wright-Hobbie uptake kinetics approach.The substrate specificity of amino acids varies greater with turnover times than with sampling location in watermasses with a certain water type. Thus a specific substrate among the essential amino acids should be selected to use for measuring the turnover time, in order to monitor precisely the state of trophic excitation within the steady-state oscillation in a certain aquatic system. On the other hand, either singular or plural substrates among the essential amino acids can be used for measuring the turnover time for the identification of a watermass, relevant to eutrophication.     

Copper fractionation with dissolved organic matter in natural waters and wastewater--a mixed micelle mediated methodology (cloud point extraction) employing flame atomic absorption spectrometry

A cloud point extraction-preconcentration methodology for the speciation analysis of free and organically complexed metal species in natural waters is presented. The method is based on the neutralization of the electrostatic charge of the humate-metal complexes with a positively charged surfactant in a high ionic strength solution environment. The resulting complexes are conveniently solubilized in the micelles of a non-ionic surfactant medium and are thus separated from the bulk aqueous phase. Free metal species are also determined by complexation with a conventional chelating agent under mild conditions. The overall procedure is easy, rapid and allows for a high sample throughput in terms of massive analysis of many samples in the same time period. The method offers substantially low detection limits of 8.5 and 0.9 micrograms l-1 for bound and labile species respectively, with a calibration curve rectilinear in the wide range 40-150 micrograms l-1 for the humate associated and 4-40 micrograms l-1 for the free metal species. The method is free from interferences yielding recoveries in the range 97-102% for various samples of different matrixes.     

流动注射--氢化物发生原子吸收法测定天然水中的丁基锡化合物

建立用流动注射--氢化物发生原子吸收法同时测定天然水中一丁基锡、二丁基锡、三丁基锡和四丁基锡化合物的方法.首先用NaBH4还原丁基锡化合物后冷凝富集、加热,氢化物根据沸点的不同依次解吸从而得到分离,由原子吸收法测定.本方法可测每升几十纳克(以锡计)的各种丁基锡化合物.     

Dissolved organic iodine in marine waters: role in the estuarine geochemistry of iodine

Non-volatile dissolved organic iodine (DOI) can be a major, or even the dominant, species of dissolved I in coastal, inshore and estuarine waters. It can be converted to IO3- in the presence of an oxidizing agent and to I- by reacting it with a reducing agent. Depending on the exact experimental conditions, the yields of these reactions may not be quantitative. In previous analytical schemes for the determination of IO3-, I- and DOI in marine waters, if oxidation or reduction steps are involved and the concentrations of one or more species are estimated by difference, the presence of DOI can lead to an overestimation of the concentrations of the inorganic species determined by difference and an underestimation of the concentration of DOI. In two cruises covering the James River to the southern Chesapeake Bay and from the southern Chesapeake Bay to the Atlantic, above a salinity (S) of 2, the contribution of DOI to total I increased with decreasing salinity and reached a maximum of 80%. DOI, I- and IO3- were successively the dominant form of dissolved I at 0.1 < S < 15 in the James River estuary, 15 < S < 30 in the Southern Chesapeake Bay and S > 30 in the Atlantic Ocean at the Bay mouth, respectively. Total I behaved conservatively (i.e., no evidence of consumption or production) during estuarine mixing during both cruises. In the southern Chesapeake Bay, total inorganic I was also approximately conservative. The primary process affecting the speciation of dissolved I was the conversion of IO3- to I-. In the James River estuary, there were indications of the conversion of both IO3- and I- to DOI. The concentrations of total I, IO3-, I- and DOI in James River water were 0.121, undetectable, 0.068 and 0.053 microM, respectively. These concentrations of total I and I- are significantly higher while that of IO3- is noticeably lower than those used presently for estimating global riverine input of these I species to the oceans. The riverine flux of DOI to the oceans is presently unknown.     

Measurement of organic contaminants and biological effects in Scottish waters between 1999 and 2005

Concentrations of organic contaminants were determined in sediment and fish collected annually at six sites around Scotland between 1999 and 2005, as part of the UK National Marine Monitoring Programme. Polycyclic aromatic hydrocarbons (PAHs) and chlorobiphenyls (CBs) were measured in sediment, while CBs and ethoxyresorufin-O-deethylase (EROD) activities were measured in the fish. Highest PAH concentrations in sediment were found at sites where higher coastal influences would be expected (e.g., Clyde and Solway) and four of the six sites gave PAH concentrations above OSPAR background assessment concentrations (BACs). A significant downward trend in the median total PAH concentrations, normalised to total organic carbon (TOC), was found at one of the six sites (Minches). The PAH profiles at all sites were consistent over the 6 year period, indicating that the sites are relatively stable and PAH sources are not changing. There was an indication of a greater petrogenic input on the west coast, with sediment from the Clyde, Solway and Minches having a greater proportion of 2- and 3-ring PAHs and a lower proportion of 5-ring PAHs. CB concentrations at all sites were low compared with UK estuarine sites and similar to sediment from more remote areas: however, BACs were exceeded. No significant trends were detected in either the sediment CB concentrations or patterns at any of the six sites. CB concentrations were significantly higher in fish liver collected from the Clyde. Concentrations at the other five sites were low, with the majority of samples having concentrations for the ICES7 CBs of <500 microg kg(-1) lipid weight. However, individual CB concentrations were still above the BACs. Hepatic EROD activities were measured in male plaice from 2002-2005 and were generally low (<10 pmol min(-1) mg protein(-1)). No temporal trends were detected in either CB concentrations or the EROD activity.     

Determination of metal-humic complexes, free metal ions and total concentrations in natural waters

A comparison of two systems for the quantitation of metal-humic complexes and free metal ions, consisting of the separation by coupled ion exchange columns followed by detection by inductively coupled plasma mass spectrometry or cold vapour atomic fluorescence spectrometry, is presented. The systems evaluated comprised the serially coupled anion and cation exchangers, Sephadex A-25/Chelex 100 and Dowex 1X8/Chelamine Metalfix. Separation and preconcentration of the species studied were accomplished with both systems, elution being carried out using 2 M HNO3. Total concentrations, metal-humic complex fractions and free metal ion fractions of Al, Ba, Cd, Co, Cu, Fe, Hg, Mn, Pb, Sr, U and Zn in nine natural waters were determined. Statistical evaluation of the data from the two cation exchange materials, including results for additional elements, showed better precision (for Al, Ba, Cr, Cu and Mo) and higher recoveries (Al, Ba, Cd, Fe, Sr and Zn) for Chelex 100 than Chelamine Metalfix for free metal ions. On the other hand, Chelamine Metalfix recovered a significantly greater amount of Ni. The amounts of metal-humic complexes were compared with modelled distributions of these species, and one advantage of the preferred Sephadex A-25/Chelex 100 system is that the elements studied are all correctly classified with respect to their binding strengths to humic substances, which is not the case with the Dowex 1X8/Chelamine Metalfix pair. With the preferred system, metal-humic complexes can be reliably determined, as indicated by the results of equilibrium speciation modelling. However, comparison with the total concentrations showed statistically significant, non-quantitative recoveries of Al, Cu, Hg, Mn, U and Zn from some samples. Thus a combination of speciation and total concentration measurements is required to obtain a complete representation of the distribution of trace elements in natural waters.