Sedimentology models from activity concentration measurements: application to the “Bay of Cadiz” Natural Park (SW Spain)

A previous study on seabed sediments of the Bay of Cadiz (SW of Spain) enabled us to identify several relations between sedimentological variables and activity concentrations of environmental radionuclides such as ¹³⁷Cs, ²²⁶Ra, ²³²Th and ⁴⁰K. In this paper the study has been extended to a large neighbouring inter-tidal area in order to establish if the above mentioned models can be generalized. As a result we have determined that the measured activity concentrations are closely to the values predicted by the theoretical models (correlation coefficient range = 0.85–0.93).     

Sorption mechanisms of cephapirin, a veterinary antibiotic, onto quartz and feldspar minerals as detected by Raman spectroscopy

Raman spectroscopy was used to investigate sorption mechanisms of cephapirin (CHP), a veterinary antibiotic, onto quartz (SiO₂) and feldspar (KAlSi₃O₈) at different pH. Sorption occurs by electrostatic attraction, monodentate and bidentate complexation. The zwitterion (CHP^o) adsorbs to a quartz⁽⁺⁾ surface by electrostatic attraction of the carboxylate anion group (-COO⁻) at low pH, but adsorbs to a quartz⁽⁻⁾ surface through electrostatic attraction of the pyridinium cation, and possibly COO⁻ bridge complexes, at higher pH. CHP⁻ bonds to quartz⁽⁻⁾ surfaces by bidentate complexation between one oxygen of -COO⁻ and oxygen from carbonyl of an acetoxymethyl group. On a feldspar^(+/−) surface, CHP^o forms monodentate complexes between CO, and possible -COO⁻ bridges and/or electrostatic attachments to localized edge (hydr)oxy-Al surfaces. CHP⁻ adsorbs to feldspar⁽⁻⁾ through monodentate CO complexation. Similar mechanisms may operate for other cephalosporins. Results demonstrate, for the first time, that Raman techniques can be effective for evaluating sorption mechanisms of antibiotics.     

Multi-group approximation, scattering and calibration coefficients, uncertainty estimates and detection limits of a NaI(Tl)-based gamma spectrometry set-up for low-level activity analysis

This paper describes a quantitative radioactivity analysis method especially suitable for environmental samples with low-level activity. The method, consisting of a multi-group approximation based on total absorption and Compton spectra of gamma rays, is coherently formalized and a computer algorithm thereof designed to analyze low-level activity NaI(Tl) gamma ray spectra of environmental samples. Milk powder from 1988 was used as the example case. Included is a special analysis on the uncertainty estimation. Gamma sensitiveness is defined and numerically evaluated. The results reproduced the calibration data well, attesting to the reliability of the method. The special analysis shows that the uncertainty of the assessed activity is tied to that of the calibration activity data. More than 77% of measured 1461-keV photons of ⁴⁰K were counted in the range of clearly lower energies. Pile-up of single line photons (¹³⁷Cs) looks negligible compared to that of a two-line cascade (¹³⁴Cs). The detection limit varies with radionuclide and spectrum region and is related to the gamma sensitiveness of the detection system. The best detection limit always lies in a spectrum region holding a line of the radionuclide and the highest sensitiveness. The most radioactive milk powder sample showed a activity concentration of 21 ± 1 Bq g⁻¹for ¹³⁷Cs, 323 ± 13 Bq g⁻¹ for ⁴⁰K and no ¹³⁴Cs.     

Rapid estimation of compost enzymatic activity by spectral analysis method combined with machine learning

The aim of this study was to investigate the feasibility of using visible near-infrared (VisNIR) diffuse reflectance spectroscopy (DRS) as an easy, inexpensive, and rapid method to predict compost enzymatic activity, which traditionally measured by fluorescein diacetate hydrolysis (FDA-HR) assay. Compost samples representative of five different compost facilities were scanned by DRS, and the raw reflectance spectra were preprocessed using seven spectral transformations for predicting compost FDA-HR with six multivariate algorithms. Although principal component analysis for all spectral pretreatments satisfactorily identified the clusters by compost types, it could not separate different FDA contents. Furthermore, the artificial neural network multilayer perceptron (residual prediction deviation = 3.2, validation r² = 0.91 and RMSE = 13.38 μg g^?1 h^?1) outperformed other multivariate models to capture the highly non-linear relationships between compost enzymatic activity and VisNIR reflectance spectra after Savitzky–Golay first derivative pretreatment. This work demonstrates the efficiency of VisNIR DRS for predicting compost enzymatic as well as microbial activity.     

表面增强拉曼光谱技术检测高氯酸根离子

高氯酸根离子是水质污染物中常见的污染源之一.通过化学还原法制备稳定、分散性好的纳米银溶胶颗粒(粒径为30～40 nm),并以此为基底,探究了利用表面增强拉曼光谱技术迅速准确地检测质量浓度为10-6～10-1 g/L的高氯酸根离子溶液的表面增强拉曼光谱.结果表明,当高氯酸根离子质量浓度为10-5～10-1 g/L时,随着高氯酸根离子浓度的降低,表面增强拉曼光谱强度逐渐减弱.     

内源呼吸过程溶解性代谢产物的光谱特性分析

微生物内源呼吸期对污水处理过程具有重要意义.为了更清晰地了解微生物内源呼吸过程,采用三维荧光光谱、紫外光谱结合呼吸图谱对微生物内源呼吸过程进行解析.结果表明,三维荧光光谱和紫外光谱在内源呼吸各个阶段有明显的不同:1内源呼吸快速下降期(第1 d):腐殖酸峰的激发波长(Ex)和发射波长(Em)分别出现5 nm、6 nm的蓝移,荧光指数f450/500和HIX(humification index)分别减小了9.3%、0.2%,UV253/203和UV254分别增加了37.5%、200%,预示着混合液中可生物降解有机物的存在;2内源呼吸慢速下降期(第2 d):f450/500增加了0.5%,HIX减小0.2%,UV253/203减小了20%,UV254增加了16.7%,预示着细胞可能出现了水解或自溶;3内源呼吸稳定期(第3~5 d):腐殖酸峰基本保持不变预示了微生物适应了饥饿环境.本研究从代谢产物的角度解析了内源呼吸过程,为污水处理过程控制提供了新的思路.     

Evaluation of Bacillus sp. MZS10 for decolorizing Azure B dye and its decolorization mechanism

To evaluate decolorization and detoxification of Azure B dye by a newly isolated Bacillus sp. MZS10 strain, the cultivation medium and decolorization mechanism of the isolate were investigated. The decolorization was discovered to be dependent on cell density of the isolate and reached 93.55%(0.04 g/L) after 14 hr of cultivation in a 5 L stirred-tank fermenter at 2.0 g/L yeast extract and 6.0 g/L soluble starch and a small amount of mineral salts. The decolorization metabolites were identified with ultra performance liquid chromatography-tandem mass spectroscopy(UPLC-MS). A mechanism for decolorization of Azure B was proposed as follows: the C=N in Azure B was initially reduced to –NH by nicotinamide adenine dinucleotide phosphate(NADPH)-dependent quinone dehydrogenase, and then the –NH further combined with –OH derived from glucose to form a stable and colorless compound through a dehydration reaction. The phytotoxicity was evaluated for both Azure B and its related derivatives produced by Bacillus sp. MZS10 decolorization, indicating that the decolorization metabolites were less toxic than original dye. The decolorization efficiency and mechanism shown by Bacillus sp. MZS10 provided insight on its potential application for the bioremediation of the dye Azure B.     

多元回归-紫外分光光度法同时测定硝基苯类化合物

对多元线性回归、多元逐步回归和岭回归三种方法应用于硝基苯类五元体系进行定量分析的结果进行了比较研究,结果表明,对于所涉及的组分光谱重叠严重的病态的混合体系,多元逐步回归和岭回归间接校正都是合适的算法,总平均相对误差分别为3.84%和3.00%.     

一种火场多参量在线监测系统的设计与实现

火场氧浓度降低、大量烟气遮挡视线和吸入毒性气体是造成火灾中人员无法逃生而窒息死亡的三大主要因素.基于波长调制光谱和谐波探测技术,利用光源调制实现了气体浓度的谐波检测;采用激光烟浓度检测方法,测得减光系数,以表征烟雾浓度.通过合理高效的系统光路和硬件设计,采用分时复用方法,大大缩短了检测周期,每2.5秒便可完成一次对火场多参量的检测,实现了同时对火场中多参量(包括火灾产物中O2、CO、CO2、HCN的浓度和烟雾浓度)的在线实时监测.