Evaluation of a second derivative UV/visible spectroscopy technique for nitrate and total nitrogen analysis of wastewater samples

A method for nitrate analysis based on second derivative UV/Visible spectroscopy was developed by Simal et al. (1985: Simal J., Lage M. A., and Iglesias I. (1985) Second derivative ultraviolet spectroscopy and sulfamic acid method for determination of nitrates in water. J. Assoc. Analyt. Chem. 68, 962-964) and Suzuki and Kuroda (1987: Suzuki, N. and Kuroda R. (1987) Direct simultaneous determination of nitrate and nitrite by ultraviolet second-derivative spectrophotometry. Analyst 112, 1077-1079), and later modified for the analysis of total nitrogen in aqueous samples of varying nitrate:organic nitrogen ratios (Crumpton et al., 1992: Crumption W. G., Isenhart T. M. and Mitchell P. D. (1992) Nitrate and organic N analyses with second-derivative spectroscopy. Limnol. Oceanogr. 37, 907-913). The procedure uses the second derivative of the absorption spectrum for nitrate (NO3-), which has a peak at approximately 224 nm that is proportional to the NO3- concentration. Samples for total N analysis are first oxidized to NO3- by persulfate digestion. The objectives of this study were to: (1) test the accuracy and precision of the second derivative method through the use of NIST-traceable wastewater check samples; (2) determine whether the second derivative method for nitrate analysis can be used for wastewater samples and whether the method compares favorably with other currently used nitrate analysis methods; and (3) use the method to analyze wastewater samples containing a range of nitrate and total nitrogen concentrations. Our results indicated that the method needed to be modified to include a longer digestion time (60 min) and dilution of samples prior to digestion (if needed). With the modified method, nitrogen recoveries were not significantly different (P > or = 0.05) from samples with known N concentrations. In addition, nitrate concentrations in constructed wetland and wastewater samples analyzed by both second derivative spectroscopy and ion chromatography were not significantly different. Total nitrogen concentrations in wastewater samples also compared favorably to the same samples analyzed by Kjeldahl digestion. The method is faster, simpler, requires smaller sample volumes, and generates less waste than many EPA-approved methods of N analysis, and may offer a suitable alternative to current methods for analysis of nitrate and total N in wastewater samples.     

Platinum, palladium and rhodium content in road dust, tunnel dust and common grass in Białystok area (Poland): a pilot study

The potential of near infrared spectroscopy (NIRS) for determining the total arsenic (As) content in the prostrate amaranth (Amaranthus blitoides S. Watson) was assessed. Seventy-four samples belonging to this species, were harvested at different maturity stages along the polluted area, and then were scanned by NIRS. Their As reference values were obtained by atomic absorption spectrometry and they were regressed against different spectral transformations using modified partial least square (MPLS) regression. First derivative transformation equation of the raw optical data, previously standardized by standard normal variate (SNV) and De-trending (DT) transformations, resulted in a coefficient of determination (r(2)) in the external validation of 0.63, indicative of equations that can be used for a correct separation of the samples into low, medium and high groups. The standard deviation to standard error of prediction ratio (RPD) and range to standard error of prediction ratio (RER) for the first derivative equation were similar to those obtained for other trace metal calibrations reported in NIRS reflectance. Major cell components such as chlorophyll, lipids, starch and proteins were used by MPLS for modeling the equations. The use of NIRS for the determination of the As content in A. blitoides plants offers an important saving of time and cost of analysis.     

微波消解原子荧光光谱法测定活性污泥中的砷

利用高压密闭微波消解技术消解城市污水处理厂污泥样品,并采用氢化物发生/原子荧光光谱法测定污泥中的砷,设定了最佳的样品处理与仪器测定条件。在0.00～200μg/L之间,标准曲线的线性相关系数达0.999 0以上,以称样0.200 0 g计,检出限为0.005 mg/kg。通过测定国家标准物质和加标回收试验,进行了方法验证,其精密度和准确度均能满足污泥环境样品的测试要求。在试验条件下,测定样品中砷的加标回收率为96%～102%,测定结果的RSD<2%。     

Detection of pollutants in water by raman spectroscopy

The possibility of monitoring pollutants in water by means of Raman spectroscopy is discussed with special reference to the CH-stretching vibration bands of possible impurities. From theoretical considerations the limits of detection were found to be in the range of 1 → 10 ppm. The perturbations due to fluorescence and turbidity in samples were investigated and methods for reducing their effects are discussed.     

氨基磺酸系高性能减水剂的研制开发

本文主要讨论了氨基磺酸系高性能减水剂的合成过程及后期混凝土试验情况。通过对反应温度、反应时间、溶液浓度和酸碱度、投料顺序及速度、第四单体的选择等反应条件的控制,合成具有最佳分子结构的最终产物,并通过红外光谱图和核磁共振谱图对合成主产物的分子结构进行了验证。同时,大量的混凝土试验说明氨基磺酸高性能减水剂具有优良的保坍性能。     

碱集料反应的介电谱特性

对碱集料反应的介电谱特性进行的讨论结果表明，如果有碱集料反应，其Cole-Cole图中存在1条起自原点的垂直线，且集料的碱活性越强，该垂直线越长，矿物掺合料可抑制碱集料反应。     

干湿循环条件下钢筋锈蚀的临界氯离子浓度

采用电化学交流阻抗谱研究了干湿循环条件下混凝土中钢筋锈蚀的临界氯离子浓度,深入探讨了混凝土中钢筋锈蚀临界点的判断方法,分析了干湿循环时间比对临界氯离子浓度的影响.结果表明:借助电化学交流阻抗谱法能较为准确地判断钢筋锈蚀临界点;临界氯离子浓度随干湿循环时间比的增加基本呈增大趋势;临界氯离子浓度与干燥结束时混凝土的饱和度之间存在线性关系,且随着干燥结束时混凝土饱和度的增大而降低.     

Characterization of organic membrane foulants in a submerged membrane bioreactor with pre-ozonation using three-dimensional excitation-emission matrix fluorescence spectroscopy

This study focuses on organic membrane foulants in a submerged membrane bioreactor (MBR) process with pre-ozonation compared to an individual MBR using three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy. While the influent was continuously ozonated at a normal dosage, preferable organic matter removal was achieved in subsequent MBR, and trans-membrane pressure increased at a much lower rate than that of the individual MBR. EEM fluorescence spectroscopy was employed to characterize the dissolved organic matter (DOM) samples, extracellular polymeric substance (EPS) samples and membrane foulants. Four main peaks could be identified from the EEM fluorescence spectra of the DOM samples in both MBRs. Two peaks were associated with the protein-like fluorophores, and the other ones were related to the humic-like fluorophores. The results indicated that pre-ozonation decreased fluorescence intensities of all peaks in the EEM spectra of influent DOM especially for protein-like substances and caused red shifts of all fluorescence peaks to different extents. The peak intensities of the protein-like substances represented by Peak T₁ and T₂ in EPS spectra were obviously decreased as a result of pre-ozonation. Both external and internal fouling could be effectively mitigated by the pre-ozonation. The most primary component of external foulants was humic acid-like substance (Peak C) in the MBR with pre-ozonation and protein-like substance (Peak T₁) in the individual MBR, respectively. The content decrease of protein-like substances and structural change of humic-like substances were observed in external foulants from EEM fluorescence spectra due to pre-ozonation. However, it could be seen that ozonation resulted in significant reduction of intensities but little location shift of all peaks in EEM fluorescence spectra of internal foulants.     

Use of three-dimensional excitation and emission matrix fluorescence spectroscopy for predicting the disinfection by-product formation potential of reclaimed water

This study was undertaken to demonstrate the feasibility of using three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy for the determination of chlorination disinfection by-product (DBP) precursors and the disinfection by-product formation potential (DBPFP) of reclaimed water samples. Two major DBP precursors were examined in this study, including humic acid (HA) and fulvic acid (FA). The 3DEEM fluorescence results obtained from various reclaimed water samples indicated that the reclaimed water samples were rich in fulvic acid-like substances that were associated with two main peaks (Ex/Em = 235-245/420-440 nm, and Ex/Em = 330-340/410-430 nm) in the fluorescence spectrum. The results also illustrated that the wavelength location of peak fluorescence intensity of a reclaimed water sample was independent of the influent water quality and the wastewater treatment process used in the reclamation plant. As a result, the peak fluorescence intensity and the wavelength location of the peak were used to identify the species of DBP precursors and their concentrations in the reclaimed water sample. Four regression models were then developed to relate the peak fluorescence intensity of the water sample to its DBPFP, including the formation potential of trihalomethane (THMFP) and the formation potential of haloacetic acid (HAAFP). The regression models were verified using the measured DBPFP results of a series of reclaimed water samples. It was found that the regression modeling results matched the measured DBPFP values well, with prediction errors below 10%. Therefore, the use of 3DEEM fluorescence spectroscopy together with the developed regression models in this study can provide a reliable and rapid tool for monitoring the quality of reclaimed water. Using this method, water quality could be monitored online, without utilizing the lengthy conventional DBPFP measurement.     

Functional group characterization of indoor, outdoor, and personal PM: results from RIOPA

Fourier transform infrared (FTIR) spectra of outdoor, indoor, and personal fine particulate matter (PM(2.5)) samples were collected during the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study. FTIR spectroscopy provides functional group information about the entire PM(2.5) sample without any chemical preparation. It is particularly important to characterizing the poorly understood organic fraction of PM(2.5). To our knowledge this is the first time that FTIR spectroscopy has been applied to a PM(2.5) exposure study. The results were used to chemically characterize indoor air and personal exposure. Sulfate was strongest in outdoor samples, which is consistent with the generally accepted understanding that sulfate is of outdoor origin. Absorbances attributed to soil dust were also seen in many outdoor and some indoor and personal samples. Inorganic nitrate absorbances were a common feature of many California and some New Jersey samples. Carbonyl absorbances showed substantial variation in strength, number of peaks, and wave number shift between samples, indicating variability in composition and sources. Absorbances attributed to aliphatic hydrocarbon and amide functional groups were enhanced in many personal and indoor samples, which suggested the influence of indoor sources in these homes. We speculate that meat cooking is one possible source of particulate amides. PRACTICAL IMPLICATIONS: To our knowledge this is the first time that FTIR spectroscopy has been used to characterize the composition of indoor and personal PM(2.5). The presence of sulfate, nitrate, ammonium, soil dust and a number of organic functional groups are all detected in one analysis on filter samples without extraction or other sample preparation. Differences between indoor and outdoor spectra are used to identify spectral features due to indoor-generated PM(2.5). Particularly interesting are the much larger aliphatic absorbances, shifts in carbonyl absorbances, and occasional small amide absorbances found in indoor and personal spectra but rarely in outdoor spectra. These observations are important because organics make up a large portion of PM(2.5) mass and their composition and properties are poorly characterized. The properties and behavior of organic compounds in airborne particles are often predicted based on their functional group composition. This analysis begins the development of a better understanding of the functional group composition of indoor and personal PM(2.5) and how it differs from that of outdoor PM(2.5). Eventually this will lead to an improved understanding of the properties, behavior and effects of PM(2.5) of indoor and outdoor origin.     

Transformation of the pernicious and toxic weed parthenium into an organic fertilizer by vermicomposting

In what is believed to be the first study of its kind, the compositions of the toxic and allelopathic weed parthenium, and its vermicompost, have been investigated using UV–visible and Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, gas chromatography–mass spectroscopy, and scanning electron microscopy. The studies reveal that the weed is transformed into a totally benign organic fertilizer during the course of its vermicomposting. This is indicated by substantial improvements in the humification index, mineralization of organic matter, and degradation of complex aromatics such as lignin and polyphenols into simpler carbohydrates and lipids when parthenium is turned into its vermicompost. There are also significant fragmentation, bio-oxidation and molecular rearrangements of chemical compounds in parthenium vermicompost compared to the parent substrate. In particular, parthenin, which is principally responsible for the toxicity and allelopathy of parthenium, is completely degraded by the vermicomposting of parthenium. The study opens the way to profitable use of the millions of tonnes of parthenium that are generated annually, the continued proliferation of which causes great loss of biodiversity.     

The use of surfactant-based separation techniques for monitoring of orthophosphate in natural waters and wastewater

In an effort to monitor orthophosphate in natural waters and wastewater in the Ipirous region (Greece), an analytical methodology was established owing to the need for interference-free determination at the low mg/l levels. The method applied for the determination of orthophosphate is based on its reaction with molybdate towards a yellow heteropoly acid complex, which is electrically balanced with a cationic surfactant (cetylatrimethylammonium bromide) towards a complex non-polar derivative. This derivative is conveniently solubilized in the micelles of a non-ionic surfactant under mild conditions and measured spectrophotometrically at 370 nm after its uptake with a sulfuric acid-methanol solution. By simply preconcentrating 10 ml of sample volume a detection limit of 2.6 microM was obtained. Due to the required dilution step and signal enhancement caused by the presence of surfactant, interference from the presence of anionic species (mostly silicate and arsenate) was minor and could be conveniently alleviated by the use of tartaric acid and Na(2)SO(3), respectively. The method was successfully applied to real samples obtained for the natural sites subject to the monitoring survey ranging in their matrix complexity from clean river water to wastewater.     

Continuous fluorescence excitation-emission matrix monitoring of river organic matter

Real-time fluorescence monitoring has been mostly performed in marine systems, with little progress being made in the application of fluorescence excitation-emission matrix (EEM) spectroscopy, especially for freshwater monitoring. This paper presents a two weeks experiment where real-time fluorescence EEM data have been obtained for Bourn Brook, Birmingham, UK, using an in-situ fibre-optic probe. Fluorescence EEMs were measured every 3 min for two weeks, with control ‘grab’ samples every hour analyzed for fluorescence EEMs as well as pH, conductivity and dissolved organic carbon. Comparison of real-time and control samples showed an excellent agreement, with no evidence of fibre-optic probe fouling. EEMs of different character were identified using self-organizing maps, which demonstrated seven clusters of fluorescence EEMs which related to the intensity of fluorescence and relative intensities of peak T₁ and T₂ vs. peak C and peak A fluorescence. Fluorescence intensity of peaks A and C were observed to increase with rainfall, and a diesel pollution event was detected through an increase in T₂ fluorescence.     

Characterization of extracellular polymeric substances of aerobic and anaerobic sludge using three-dimensional excitation and emission matrix fluorescence spectroscopy

In this study three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was applied to characterize the extracellular polymeric substances (EPS) extracted from aerobic and anaerobic sludge in wastewater treatment. Three fluorescence peaks were identified in EEM fluorescence spectra of the EPS samples. Two peaks were attributed to the protein-like fluorophores, and the third to the humic-like fluorophores. The effects of both pH and EPS concentration were significant on EEM fluorescence spectra of EPS, but the ionic strength had no substantial effect on EEM spectra of the EPS. The differences in the EPS fluorescence parameters, e.g., peak locations, intensities and ratios of various peak intensities, indicate the difference in the chemical structures of the EPS from various origins. EEM spectroscopy was proven to be an appropriate and effective method to characterize the EPS from various origins in wastewater treatment systems.     

交流阻抗谱在混凝土保护涂层研究中的应用

通过论述交流阻抗谱方法(A.C.Impedance Spectrum,缩写为ACIS)在混凝土保护涂层系统中应用的可行性的基础上,提出了混凝土保护涂层系统ACIS行为的"串砖块"等效电路模型,并进一步试验验证了模型的正确性.为交流阻抗谱方法研究混凝土保护涂层的性质提供了有益的参考.     

混凝土阻抗谱的拓扑结构

将常见的各种混凝土试样的交流阻抗响应曲线按拓扑学进行了分类；对常见的双过程曲线的等效电路和时间常数进行了详细讨论。     

Infrared spectroscopy tracing of sediment sources in a small rural watershed (French Alps)

The present article describes a first attempt to use infrared spectroscopy to trace the origin of suspended river sediments. Fifty samples of the main potential sediment sources within a small catchment area (990 ha) in the French Alps were collected and compared with samples of suspended sediment from the river, collected on various dates during 2006 and 2007 using sediment traps. Two major categories of sediment source were identified: topsoils and river channel sediments. For the qualitative part of the study, each of these two main categories was divided into two sub-categories, that is to say, cultivated and pastureland topsoils, and riverbed and riverbank sediments. Discriminant analysis on the source samples showed that Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy can be used to differentiate between the four potential source materials. To determine whether or not immersion in the river altered the infrared spectra of these source materials, we measured the infrared spectra of samples that had been immersed in the river, in litter bags, for periods of up to 24 days. Immersion did not cause any major changes in the infrared spectra. The contribution of each type of source material to the suspended sediment in the river was quantified using partial least squares (PLS) analyses of DRIFT spectra to compare actual river sediment samples with an experimental model. This model was produced from the DRIFT spectra of a range of calibration samples produced by mixing source material samples in different ratios. The predictions of the model were valid and fell within the confidence interval calculated for the calibration set. Comparisons between suspended sediment samples and the model indicate that the predominant source of the sediment is riverbank erosion, which, in this case, is probably due to trampling by cattle.     

Rapid and direct determination of tryptophan in water using synchronous fluorescence spectroscopy

Water samples from lakes situated in and around the area of Tsukuba Science City, Ibaraki Prefecture, Japan, were analysed using synchronous fluorescence spectroscopy and HPLC. The spectra revealed a major emission peak (lambda emm) at 340 nm corresponding to an excitation wavelength (lambda exc) position of 280 nm and a Stoke's shift, delta lambda = 60 nm. The fluorescence intensities at these wavelengths were normalised with respect to the water Raman peak, where the lambda exc was 397 nm and the lambda emm was 453 nm, and corrections were introduced to take into account absorption/re-absorption effects of the fluorescing signals caused by the sample matrix. Normalised fluorescence values correlate well with levels of tryptophan present in the samples determined by HPLC analysis (R2 = 0.99). The relationship of the observed tryptophan-like fluorescence in the water samples to the presence of free tryptophan is discussed.     

Evaluation on the toxicity of nanoAg to bovine serum albumin

Measuring protein damage by nanomaterials may give insight into the mechanisms of toxicity of nanomaterials. The toxic effects of nanoAg on bovine serum albumin (BSA) were thoroughly studied using fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, resonance light scattering spectroscopy (RLS), circular dichroism spectroscopy (CD) and transmission electron microscopy (TEM). NanoAg had obvious toxic effects on BSA: nanoAg could increase the amount of helix and decrease the beta sheet structure, leading to a loosening of the protein skeleton. In the loose structure, internal hydrophobic amino acids are exposed and the characteristic fluorescence of BSA is obviously quenched. When the ratio of nanoAg and BSA increased to 1: 96 (wt/wt), the impact of nanoAg on the spectral properties leveled off. The RLS spectrum, TEM, CD spectra and electrophoresis results showed that BSA had destroyed the double-layer structure of nanoAg and covered its surface, generating a BSA-nanoAg complex held together by van der Waals and electrostatic forces. This paper provides a new perspective and method for determining the toxic effects of nanoAg on biological macromolecules.     

水泥浆体／碎石界面性能的交流阻抗研究

提出了用交流阻抗谱方法来研究水泥浆体／碎石界面的性能。通过比较交流阻抗谱的三个参数来确定水混浆体／碎石界面效应的大小。