Ascorbic acid treatment to reduce residual halogen-based oxidants prior to the determination of halogenated disinfection byproducts in potable water

Treatment of potable water samples with ascorbic acid has been investigated as a means for reducing residual halogen-based oxidants (disinfectants), i.e. HOCl, Cl2, Br2 and BrCl, prior to determination of EPA Method 551.1A and 551.1B analytes. These disinfection byproducts include certain haloalkanes, haloalkenes, haloethanenitriles, haloaldehydes, haloketones and trichloronitromethane. When used as a dehalogenating agent immediately before analysis, only one analyte, 2,2,2-trichloroethanediol (chloral hydrate), is significantly decomposed. Ascorbic acid is superior to thiosulfate and sulfite as it does not destroy trichloroethanenitrile (trichloroacetonitrile), trichloronitromethane (chloropicrin) or dibromoethanenitrile (dibromoacetonitrile). Unlike ammonia or amines, it is not nucleophilic and cannot form hemiaminals (carbinolamines) with carboxaldehydes and ketones. Ascorbic acid treatment can rapidly consume (reduce) large amounts of active (oxidizing) halogen compounds, producing only inorganic halides and dehydroascorbic acid and not additional halogenated organic molecules.     

Influence of reagent purity on the ion chromatographic determination of bromate in water using 3,3'-dimethoxybenzidine as a prochromophore for photometric detection

Variable availability of the purified dihydrochloride salt of 3,3'-dimethoxybenzidine (DMB; ortho-dianisidine) led us to investigate the effects of reagent purity on the analytical results obtained when this reagent is used in the photometric determination of the disinfection byproduct bromate. After analyte ions are separated by ion chromatography, a solution of DMB (post-column reagent) is added to the eluate and the DMB is oxidized, thereby producing a chromophore detected by its absorbance. Although some commercial products of undefined grade performed well, others did not. Variability was also observed between lots of purified material. Sensitivity at low concentrations (< 5 micrograms L-1 BrO3-) varied by a factor of up to 10. In some cases, the lower limit of detection for photometric detection was greater than that obtained using conductivity detection, as high as 5-7 micrograms L-1 BrO3-. An impurity or several impurities are suspected to be responsible for deviations from linearity at low analyte concentrations. This investigation underscores the need for ensuring reagent purity in environmental analyses. Ideally, chemical manufacturers will meet the needs of analytical chemists who test potable water and begin producing a high grade material in sufficient quantities to meet monitoring requirements. The establishment of third-party standards for a spectrophotometric grade of DMB.2HCl would be helpful in ensuring that a variety of manufacturers could supply products of uniformly high quality that would be suitable for the measurement of bromate in public drinking water supplies.     

水中二氧化氯,氯,亚氯酸根和氯酸根区分测定法

为了保护人类健康制定卫生规范,同时为ＣｌＯ２的研究和应用提供基础手段,必须要建立一种能准确区分测定水中ＣｌＯ２,Ｃｌ２,ＣｌＯ＾－１２,ＣｌＯ＾－３浓度的方法。回顾了现有水中ＣｌＯ２,Ｃｌ２,ＣｌＯ＾－２和ＣｌＯ＾－３的区分测定方法,评述了各种测定方法的优缺点和适用性,指出了目前在区分测定这恨氧化物的方法中存在的问题,提出了解决问题的途径。     

Perchlorate retention and mobility in soils

Adsorption and release of perchlorate in a variety of soils, minerals, and other media were studied when the solid media were exposed to low and high aqueous solutions of perchlorate salts. Low level ClO4- exposure was investigated by subjecting triplicate 5.0 g portions of a solid medium (38 different soils, minerals, or dusts) to 25 mL of an aqueous ammonium perchlorate (NH4ClO4) solution containing 670 ng mL(-1) (6.8 microM) perchlorate. This corresponds to a perchlorate-to-soil ratio of 3.4 microg g(-1) (34 nmol g(-1)). At this level of exposure, more than 90% of the perchlorate was recovered in the aqueous phase, as determined by ion chromatography. In some cases, more than 99% of the perchlorate remained in the aqueous phase. In some cases, the apparent loss of aqueous perchlorate was not clearly distinguishable from the variation due to experimental error. The forced perchlorate anion exchange capacities (PAECs) were studied by soaking triplicate 5.0 g portions of the solid media in 250 mL of 0.20 M sodium perchlorate (NaClO4) followed by repeated deionized water rinses (overnight soaks with mixing) until perchlorate concentrations fell below 20 ng mL(-1) in the rinse solutions. The dried residua were leached with 15.0 mL of 0.10 M sodium hydroxide. The leachates were analyzed by ion chromatography and the perchlorate concentrations thus found were subsequently used to calculate the PAECs. The measurable PAECs of the insoluble and settleable residua ranged from 4 to 150 nmol g(-1) (micromol kg(-1)), with most in the 20-50 nmol g(-1) range. In some soils or minerals, no sorption was detectable. The mineral bentonite was problematic, however. Overall, the findings support the widely accepted idea that perchlorate does not appreciably sorb to soils and that its mobility and fate are largely influenced by hydrologic and biologic factors. They also generally support the idea that intrasoil perchlorate content is depositional rather than sorptive. On the other hand, sorption (anion replacement) of perchlorate appears to occur in some soils. Therefore, the measurement of perchlorate in soils requires accounting for ion exchange phenomena; leaching with water alone may give inaccurate results. If perchlorate anion exchange is confirmed to be negligible, then leaching procedures may be simplified accordingly.     

Bromate analysis in groundwater and wastewater samples

Bromate (BrO(3)(-)) is a disinfection by-product formed during ozonation of potable water supplies containing bromide (Br(-)). Bromate has been classed by the World Health Organisation as a 'possible human carcinogen', leading to implementation of 10-25 microg L(-1)(as BrO(3)(-)) drinking water limits in legislative areas including the United States and European Union. Techniques have been developed for bromate analysis at and below regulatory limits, with Ion Chromatography (IC) coupled with conductivity detection (IC-CD), post-column reaction and ultra-violet (UV) detection (IC-PCR), or inductively coupled plasma-mass spectrometry detection (IC-ICPMS) in widespread use. The recent discovery of bromate groundwater contamination in a UK aquifer has led to a requirement for analysis of bromate in a groundwater matrix, for environmental monitoring and development of remediation strategies. The possibility of bromate-contaminated water discharge into sewage treatment processes, whether accidental or as a pump-and-treat strategy, also required bromate analysis of wastewater sources. This paper summarises techniques currently available for trace bromate analysis in potable water systems and details studies to identify a methodology for routine analysis of groundwater and wastewater samples. Strategies compared were high performance liquid chromatography (HPLC) with direct UV or PCR/UV detection, IC-CD, IC-PCR, and a simple spectrophotometric technique. IC-CD was the most cost-effective solution for simultaneous analysis of bromate and bromide within groundwater samples, having a 5 microg L(-1) detection limit of both anions with limited interference from closely-eluting species. Wastewater samples were successfully analysed for bromate only using HPLC with PCR/UV detection, with detection limits below 20 microg L(-1)(as BrO(3)(-)) and low interference. HPLC with direct UV detection was unsuitable for bromate analysis within the concentration range 50-5000 microg L(-1) which was required for this project, but column choice was shown to be a major factor in determining limits of detection. Spectrophotometry could not reproducibly determine bromate concentration, although the technique showed promise as a quick field method for high-level groundwater bromate analysis.     

Spectrophotometeric determination of trace amounts of Al3+ ion in water samples after cloud point extraction using quinizarin as a complexing agent

In this study, cloud point extraction was used for the preconcentration of Al³⁺ ion after the complex formation with 1,4-dihydroxy-9,10-anthraquinone (Quinizarin [QUIN]), and subsequent analysis by spectrophotometeric method, using Triton X-114 as surfactant. The optimal extraction and reaction conditions were studied (i.e., pH?=?5.5, 0.1 mM QUIN, Triton X-114?=?0.1 % (w/v)), and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and enrichment factors) were obtained. Linearity was obeyed in the range of 3.33–166.67 ng ml^?1 of Al³⁺ ion. The detection limit of the method was 2.09 ng ml^?1 for Al³⁺ ion. The interference effect of some anions and cations was also tested. The method was applied to determine Al³⁺ ion in water samples.     

A rapid and accurate method for the determination of plutonium in food using magnetic sector ICP-MS with an ultra-sonic nebuliser and ion chromatography

In the event of a nuclear incident it is essential that analytical information on the distribution and level of contamination is available. An ICP-MS method is described which can provide data on plutonium contamination in food within 3 h of sample receipt without compromising detection limits or accuracy relative to traditional counting methods. The method can also provide simultaneous determinations of americium and neptunium. Samples were prepared by HNO3 closed-vessel microwave digestion, evaporated to dryness and diluted into a mobile phase comprising 1.5 M HNO3 and 0.1 mM 2,6-pyridinedicarboxylic acid. A commercially available polystyrene-divinylbenzene ion chromatography column provides on-line separation of 239Pu and 238U reducing the impact of the 238U1H interference. Oxidation of the sample using H2O2 ensures all Pu is in the Pu(+4) state. The oxidation also displaces Np away from the solvent front by changing the oxidation state from Np(+3) to Np(+4) and produces the insoluble Am(+4) ion. Simultaneous Pu, Am and Np analyses therefore require omission of the oxidation stage and some loss of Pu data quality. Analyses were performed using a magnetic sector ICP-MS (Finnigan MAT Element). The sample is introduced to the plasma via an ultrasonic nebuliser-desolvation unit (Cetac USN 6000AT+). This combination achieves an instrumental sensitivity of 238U > 2 x 10(7) cps/ppb and removes hydrogen from the sample gas, which also inhibits the formation of 238U1H. The net effect of the improved sample introduction conditions is to achieve detection levels for Pu of 0.020 pg g(-1) (4.6 x 10(-2) Bq kg(-1)) which is significantly below 1/10th of the most stringent EU (European Union) legislation, currently 0.436 pg g(-1) (1 Bq kg(-1)) set for baby food. The new method was evaluated with a range of biological samples ranging from cabbage to milk and meat. Recovery of Pu agrees with published values (100% +/- 20%).     

The effect of light and iron(II)/iron(III) on the distribution of Tl(I)/Tl(III) in fresh water systems

The distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties was studied by quantifying the oxidation states after separation with ion chromatography and on-line detection with ICP-MS. Ultraviolet irradiation of aqueous solutions containing 1 microg l(-1) Tl(III) and in equilibrium with the atmosphere increases the reduction rate. In systems with photoreduction of Fe(III)(aq) a quantitative oxidation of Tl(I)(aq) was observed, notably at low pH. The process is reversible, as indicated by formation of Tl(I) when the irradiated systems were kept in the dark. In systems with colloidal silica-stabilised ferrihydrite, UV irradiation also leads to oxidation of Tl(I)(aq), but not quantitatively. It is suggested that adsorption of thallium to the ferrihydrite determines the rate of oxidation. Detectable, but not quantitative, oxidation of Tl(I)(aq) took place when natural water samples with 1 microg l(-1) Tl(I)(aq) were exposed to either sunlight or UV-light. For these samples, the reduction was not quantitative when they were kept in the dark for 24 h. The results suggest that the light dependent iron cycle in fresh water systems strongly influences the redox state of thallium.     

质谱及其联用技术在水中消毒副产物识别和分析中的应用

水中消毒副产物(DBPs)是在水消毒过程中消毒剂与水中溶解性有机物以及无机离子发生反应而产生,其对水环境生态安全和人体健康有不利影响。简述了DBPs的生成、种类、毒性和分析方法等,重点综述了气相色谱-质谱联用(GC-MS)、液相色谱-质谱联用(LC-MS)、离子色谱-质谱联用(IC-MS)以及超高分辨率质谱(UPMS)等质谱(MS)及其联用技术在水中DBPs识别和分析中的应用,分析了不同MS技术的特点和应用实例,提出了MS技术在DBPs研究领域的发展方向与挑战。     

北京市大气颗粒物的浓度水平和离子物种的化学形态

用离子色谱法测定了 1 998年 1 1月至 1 999年 2月期间的 2 4个总悬浮颗粒物 (TSP)样品中 NH+ 4、NO- 3、SO2 - 4和Na+ 质量浓度。研究结果表明 ,北京市冬季大气颗粒物中离子物种的化学形态可以分为三种情况 :污染严重时 ,离子物种以 H2 SO4 、NH4 HSO4 、Na NO3为主要存在形态 ,气溶胶酸性强 ;污染轻时 ,离子物种以 (NH4 ) 2 SO4 、Na NO3为主要存在形态 ,气溶胶呈弱酸性 ;中等污染时 ,离子物种以 (NH4 ) 2 SO4 、NH4 HSO4 、Na NO3几种化学形态存在 ,气溶胶呈中等酸性     

曙红荧光猝灭法测定水中ClO2

在pH值为5.0的HAc-NaAc缓冲溶液中,曙红在540 nm处产生一个荧光峰,并能被ClO2氧化导致其荧光发生猝灭.通过试验确定了ClO2使曙红褪色的最佳条件,ClO2在0.042 mg/L～0.916 mg/L范围内与曙红荧光猝灭强度呈线性关系,据此建立了水中ClO2的荧光分析方法,方法检出限为0.01 mg/L.     

Fractionation of sedimentary arsenic from Port Kembla Harbour, NSW, Australia

The binding of arsenic in sediments of the heavily industrialised Port Kembla Harbour, NSW, Australia, has been investigated. Both dredge and core samples have been used to develop a sieving/sequential extraction (SE) procedure. Dredge samples included oxic surficial and deeper anoxic sediment. The main core sample analysed was 18 cm deep, sliced at 2 cm intervals. Sediment was sieved to three size ranges (<63 microm, 63-250 microm, >250 microm) and each of these was then subjected to a four step SE, sequentially solubilizing arsenic as ion exchangeable, 1 M HCl soluble, NH(2)OH.HCl soluble, and strong oxidising acid soluble. Concentrations of 50-500 mg As kg(-1) were found, elevated well above local background values. The core sample showed elevated concentrations of arsenic within the top 6-8 cm (300-500 mg As kg(-1)), relative to the deeper sediment (100-200 mg As kg(-1)). Substantial portions of the total arsenic present in the 0-8 cm sediments of core and dredge samples, were found to be soluble in 1 M pH 5 phosphate buffer or 1 M HCl. Arsenic in the lower 8-18 cm of the core displayed different solubility, the fourth stage SE strong acid digestion being required to solubilize >90% of the deep sediment arsenic. It appears that diagenesis had resulted in remobilisation of weakly bound arsenic with subsequent diffusion and deposition in surficial layers. Strong acid soluble arsenic present in deeper sediments has two possible origins: sedimented as strongly bound remaining untouched by diagenetic events, or subjected to diagenetic reactions such as pyritization, which lead to more stable crystalline forms of minerals.     

The role of humic non-exchangeable binding in the promotion of metal ion transport in groundwaters in the environment

Metal ions form strong complexes with humic substances. When the metal ion is first complexed by humic material, it is bound in an 'exchangeable' mode. The metal ion in this fraction is strongly bound, however, if the metal-humic complex encounters a stronger binding site on a surface, then the metal ion may dissociate from the humic substance and be immobilised. However, over time, exchangeably-bound metal may transfer to a 'non-exchangeable' mode. Transfer into this mode and dissociation from it are slow, regardless of the strength of the competing sink, and so immobilisation may be hindered. A series of coupled chemical transport calculations has been performed to investigate the likely effects of non-exchangeable binding upon the transport of metal ions in the environment. The calculations show that metal in the non-exchangeable mode will have a significantly higher mobility than that in the exchangeable mode. The critical factor is the ratio of the non-exchangeable first-order dissociation rate constant and the residence time in the groundwater column, metal ion mobility increasing with decreasing rate constant. A second series of calculations has investigated the effect of the sorption to surfaces of humic/metal complexes on the transport of the non-exchangeably bound metal. It was found that such sorption may reduce mobility, depending upon the humic fraction to which the metal ion is bound. For the more weakly sorbing humic fractions, under ambient conditions (humic concentration etc.) the non-exchangeable fraction may still transport significantly. However, for the more strongly sorbed fractions, the non-exchangeable fraction has little effect upon mobility. In addition to direct retardation, sorption also increases the residence time of the non-exchangeable fraction, giving more time for dissociation and immobilisation. The non-exchangeable dissociation reaction, and the sorption reaction have been classified in terms of two Damkohler numbers, which can be used to determine the importance of chemical kinetics during transport calculations. These numbers have been used to develop a set of rules that determine when full chemical kinetic calculations are required for a reliable prediction, and when equilibrium may be assumed, or when the reactions are sufficiently slow that they may be ignored completely.     

Application of cryofocusing hydride generation and atomic fluorescence detection for dissolved mercury species determination in natural water samples

The concentration levels of mercury (Hg) species in natural water samples are usually low. Consequently, accurate analysis with low detection limits is still a major problem. In this work, a method was applied for the simultaneous direct determination of dissolved mercury species in water samples by on-line hydride generation (HG), cryogenic trapping (CT), gas chromatography (GC) and detection by atomic fluorescence spectrometry (AFS). The suitability of the method for real samples with different organic matter and chloride contents was evaluated by recovery experiments in synthetic and natural spiked water samples. The HG method was compared with other current available methods for mercury analysis with respect to the different fraction of mercury analysed, i.e. 'reactive', 'reducible' or total. HG derivatization and SnCl2 reduction (with and without previous oxidation with BrCl) were applied to synthetic and natural (spiked and non-spiked) water samples. The influence of chloride and dissolved organic matter concentrations was studied. The results suggest that the HG procedure is suitable for the simultaneous determination of Hg2+ and MeHg+ in surface water samples. Inorganic mercury analysed by HG (i.e. reducible) is close to the total inorganic mercury.     

Spectrophotometric determination of anionic surfactants: optimization by response surface methodology and application to Algiers bay wastewater

A simple analytical method for quantitative determination of an anionic surfactant in aqueous solutions without liquid-liquid extraction is described. The method is based on the formation of a green-colored ion associate between sodium dodecylbenzenesulfonate (SDBS) and cationic dye, Brilliant Green (BG) in acidic medium. Spectral changes of the dye by addition of SDBS are studied by visible spectrophotometry at maximum wave length of 627 nm. The interactions and micellar properties of SDBS and cationic dye are also investigated using surface tension method. The pH, the molar ratio ([BG]/[SDBS]), and the shaking time of the solutions are considered as the main parameters which affect the formation of the ion pair. Determination of AS in distilled water gives a significant detection limit up to 3?×?10^?6?M. The response surface methodology (RSM) is applied to study the absorbance. A Box-Behnken is a model designed to the establishment of responses given by parameters with great probability. This model is set up by using the three main parameters at three levels. Analysis of variance shows that only two parameters affect the absorbance of the ion pair. The statistical results obtained are interesting and give us real possibility to reach optimum conditions for the formation of the ion pair. As the proposed method is free from interferences from major constituents of water, it has been successfully applied to the determination of anionic surfactant contents in wastewaters samples collected from Algiers bay.     

Determination of CH4, CO2 and N2O in air samples and soil atmosphere by gas chromatography mass spectrometry, GC-MS

A method for determination of the climate gases CH4, CO2 and N2O in air samples and soil atmosphere was developed using GC-MS. The method uses straightforward gas chromatography (separation of the gases) with a mass spectrometric detector in single ion mode (specific determination). The gases were determined with high sensitivity and high sample throughput (18 samples h(-1)). The LOD (3sigma) for the gases were 0.10 micro L L(-1) for CH4, 20 microL L(-1) for CO2 and 0.02 microL L(-1) for N2O. The linear range (R2 = 0.999) was up to 500 microL L(-1) for CH4, 4000 microL L(-1) for CO2 and 80 microL L(-1) for N2O. The samples were collected in 10 mL vials and a 5 microL aliquot was injected on column. The method was tested against certified gas references, the analytical data gave an accuracy within +/-5% and a precision of +/-3%. The presence of < or = 10% by volume of C2H2 (often used experimentally to prevent N2 formation from N2O) did not interfere with detection for the targeted trace gases.     

长江入海口北岸单站降水组分10年变化状况探讨

分析2001—2010年南通市区城中子站降水监测点位数据,得出降水中起致酸作用的阴离子硫酸根、硝酸根、氟离子和氯离子中除硝酸根呈现显著性上升趋势,其余上升趋势不明显;氯离子、钠离子与降水量存在高度线性负相关,硫酸根、硝酸根与降水量分别为低度非线性负相关和正相关,其他项目与降水量为显著性非线性负相关;将pH分5级,pH<4.7为重酸雨频率,pH4.7～5.0为较重酸雨频率,pH5.0～5.3为中度酸雨频率,pH5.3～5.6为轻度酸雨频率,pH≥0.56为非酸雨频率,其结果表明:南通市区2009、2010年酸雨频率降低,分别为44.1%和38.2%,主要是重酸雨频率减少,非酸雨频率增加;2003、2007年酸雨频率升高,分别为67.4%和69.8%,主要是重酸雨频率增加,非酸雨频率减小;降水量大小与电导率浓度高低没有对应性;阴阳离子浓度总量逐年、逐月同步变化;阴离子中硫酸根、硝酸根浓度逐年、逐月变化量与幅度较大;阳离子中钙离子、铵离子浓度逐年、逐月变化量与幅度较大;阴阳离子浓度逐年、逐月占比呈准对称形。     

冷原子吸收法测汞用干燥剂

试验了几种常用的干燥剂在冷原子吸收法测定水中汞时,对汞蒸气的干燥性能及对测定灵敏度的影响。结果表明,以无水氯化钙和无水高氯酸镁效果最好     

Use of ethylene diurea (EDU) in assessing the impact of ozone on growth and productivity of five cultivars of Indian wheat (Triticum aestivum L.)

Increase in concentrations of tropospheric ozone (O(3)) is one of the main factors affecting world agriculture production. Tropical countries including India are at greater risk due to their meteorological conditions (high solar radiation and temperature) being conducive to the formation of O(3). The most effective anti-ozonant chemical is N-[2-(2-oxo-1-imidazolidinyl) ethyl]-N-phenylurea or ethylene diurea (EDU). Due to its specific characteristics, EDU has been used in the field as a phytomonitoring agent to assess crop losses due to O(3). Field experiments were conducted on five local cultivars of wheat (Triticum aestivum L. cv HUW234, HUW468, HUW510, PBW343, and Sonalika) grown under natural field conditions in a suburban area of Varanasi, Uttar Pradesh, India during December 2006 to March 2007 to determine the impact of O(3) on their growth and yield characteristics. Mean monthly O(3) concentrations varied between 35.3 ppb and 54.2 ppb at the experimental site. EDU treatment positively affected various growth and yield parameters with difference between cultivars. EDU-treated plants showed increase in shoot and root length, leaf area, absolute growth rate, relative growth rate, and net primary productivity, indicating O(3) induced suppression in growth. EDU treatment was highly significant in different cultivars for total biomass and test weight but not for harvest index. Yield per plant was higher by 25.6%, 24%, 20.4%, 8.6%, and 1.9% in EDU-treated cultivars HUW468, Sonalika, HUW510, HUW234, and PBW343, respectively, than non-EDU-treated ones. These results clearly indicate the sensitivity of all the wheat cultivars to ambient levels of O(3) with cv HUW468 appearing to be most sensitive. The present study also supports the view that EDU has great potential in alleviating the unfavorable effects of O(3) and can be effectively used as a monitoring tool to assess growth and yield losses in areas experiencing elevated concentrations of O(3).     

Monochloramine loss in the presence of humic acid

Free chlorine has been used extensively as a primary and secondary disinfectant for potable water. Where it is difficult to maintain a free chlorine residual or when disinfection by-products (DBPs) are of concern, monochloramine has been used to provide a stable disinfectant residual in distributions systems. Reactions of disinfectants, free chlorine or monochloramine, with natural organic matter (NOM) consequently result in the formation of DBPs such as trihalomethanes and haloacetic acids. However, few studies have focused on the fate and kinetics of monochloramine loss in the presence of reactive constituents such as NOM. Monochloramine is inherently unstable and decays even without reactive constituents present via a mechanism known as autodecomposition. Therefore, to predict monochloramine concentrations in the presence of NOM is clearly associated with the ability to adequately model autodecomposition. This study presents the results of a semi-mechanisiic model capable of predicting the loss of monochloramine in the presence of humic material in the pH range of 6.55-8.33. The model accounts for both fast and a slow monochloramine demand to explain the loss of monochloramine over the pH range of this study. The formation of dichloroacetic acid was also predicted due to the ability of the model to differentiate monochloramine reaction pathways in the presence NOM. The results shown here demonstrate the ability of a semi-mechanistic model to predict monochloramine residuals and DBP formation in the presence of humic material.