Application of magnetoelastic sensors for quantifying sediment deposition rates and sizes

This paper describes the application of magnetoelastic sensors for quantifying the size and deposition rate of sediment samples in costal areas, lakes, and rivers. The magnetoelastic sensor, which is made of inexpensive amorphous ferromagnetic alloy, measures parameters of interest by tracking the changes in its resonant frequency and/or amplitude. Since an increase in mass loading on the sensor surface changes its resonant frequency and amplitude, the deposition rate of sediment particles can be determined in real time by tracking these two quantities. Based on a theoretical model, the size distribution of the sediment particles was also estimated from the deposition rate.     

Detection of petroleum hydrocarbons at low ppb levels using quartz resonator sensors and instrumentation of a smart environmental monitoring system

Petroleum hydrocarbon vapors at low ppb levels can be detected using a thickness shear mode resonator (TSMR) coated with a chemical-sensing overlayer, prepared by radiofrequency sputtering of porous sintered-polyethylene (PS-PE). The sensing capabilities of PS-PE sensors were profoundly affected by the sputtering methods; they were enhanced by the photo-excitation effect, and were reduced by carbonization and water treatment. The photo-assisted PS-PE sensor was extremely sensitive and could detect linear hydrocarbon (> C12) vapors below the ppb level. The time constant of the sorption curve, however, was large, indicating a slow sensing speed. Toward creating instrumentation for a smart environmental monitoring system, the TSMR sensors were arrayed on a circuit board equipped with a serial interface and signal processing chips of the oscillation drive and frequency counter. Co-sorption with water vapor at a relative humidity of about 10% has almost no effect on the sensing ability of PS-PE sensors for 1,2,4-trimethylbenzene. Conversely, it enhances the sensitivity of the TSMR sensor coated with a D-phenylalanine film. Upward shifts in the baseline are evident with elapsed time. However, a rigorous ten-cycle iteration test for 100 ppm toluene vapor demonstrated good reproducibility of the sensor's signals.     

Evaluation of a fast wastewater odour characterisation procedure using a chemical sensor array

Sewage treatment works are one of the major sources that cause atmospheric odour pollution. The increase in the number of complaints about odour nuisance is due to the increase in environmental concerns. Unfortunately, the legislation on odour nuisance from sewage treatment works is very limited. In order to determine suitable thresholds on which to base legal standards, reliable and efficient odour measurement methods need to be defined. A chemical sensor array was developed for the purpose of measuring wastewater odour. This paper describes the development of the chemical sensor system which is specifically tuned to odours of wastewater origin and which can give an electronic measure of the wastewater odours. Odour emissions from a wastewater treatment facility were detected by using a quartz crystal microbalance (QCM) sensor array. The array consists of nine sensor elements, which were coated with different materials. In this paper, the usage of these novel instruments in the water industry was shown.     

Metal diffusion properties of a Nafion-coated porous membrane in an aquatic passive sampler system

A cellulose acetate membrane, positioned in a passive sampler system, was coated with the perfluorinated polymer Nafion. Aqueous metal transport through the membrane and the Nafion film was investigated. The Nafion-coated membrane prevents the transport of metals bound to natural organic material to the receiving phase in the passive sampler, while copper associated with small synthetic ligands pass through the Nafion film. Increasing thickness of the Nafion film decreases the metal uptake rate to the receiving phase in the passive sampler and increases the response time. A decreased response time for the passive sampler would provide a better estimation of rapid changes in concentration, particularly for dynamic aquatic systems such as urban runoff. Limited biofouling protection with the Nafion coating was demonstrated by growth inhibition of natural periphyton communities on glass surfaces.     

1994—2010年东亚地区CO2浓度变化特征及成因分析

在东亚地区选取5个大气本底观测站1994年以来观测的 CO2监测资料,分析了各站大气 CO2的时空变化特征,以及 CO2主要人为源的变化及其影响。结果表明,5个本底站大气 CO2年均值均呈明显升高趋势,2010年较1994年增长幅度为8．4％～9．0％;在北半球国家,CO2月均值有明显的季节变化,高值多出现在冬春等寒冷季节,低值多出现在夏季。减少化石燃料消耗量、增加森林覆盖率及农业覆盖率将对大气中 CO2有削减作用。     

Personal ammonia sensor for industrial environments

The realisation of an opto-chemical ammonia sensor suitable for personal monitoring tasks is described, comprising a cyanine dye immobilised in a microporous glass thin film. The fabrication of sensor platforms incorporating embossed grating couplers provides a compact optical design with effective waveguiding characteristics, resulting in reversible ammonia sensitivity in the 5-100 ppm range in under 2 min. Cross-sensitivity of sensor response with water and other potential interferents is considered.     

睢宁地区大气PM_(2.5)及气态污染物季节性变化特征

根据2014年全年实时在线观测数据,分析了徐州睢宁地区大气细颗粒物(PM_(2.5))和气态污染物(包括SO_2、CO、NO_x、O_3)质量浓度的季节性变化特征。结合后向轨迹模型,分析不同气团对该地区大气污染浓度的影响。PM_(2.5)与O_3值在夏季最低,呈显著相关,表明夏季PM_(2.5)主要受控于本地大气光化学活性。在冬季,除O_3外,PM_(2.5)、SO_2、CO、NO_x值最高,且大气颗粒物主要以细粒子为主。O_3在春季最高,并与远程传输的气团且经过我国东部污染源密集地区相对应。高浓度的PM_(2.5)主要与冬季缓慢移动的气团相对应,这可能将PM_(2.5)及其气态前体物传输至该地区进而加重大气污染程度。     

Molecular-level methods for monitoring soil organic matter responses to global climate change

Soil organic matter (SOM) is one of the most complex natural mixtures on earth. It plays a critical role in many ecosystem functions and is directly responsible for sustaining life on our planet. However, due to its chemical heterogeneity, SOM composition at molecular-level is still not completely clear. Consequently, the response of SOM to global climate change is difficult to predict. Here we highlight applications of two complementary molecular-level methods (biomarkers and nuclear magnetic resonance (NMR)) for ascertaining SOM responses to various environmental changes. Biomarker methods that measure highly specific molecules determine the source and decomposition stage of SOM components. However, biomarkers only make up a small fraction of SOM components because much of SOM is non-extractable. By comparison, (13)C solid-state NMR allows measurement of SOM in its entirety with little or no pretreatment but suffers from poor resolution (due to overlapping of SOM components) and insensitivity, and thus subtle changes in SOM composition may not always be detected. Alternatively, (1)H solution-state NMR methods offer an added benefit of improved resolution and sensitivity but can only analyze SOM components that are fully soluble (humic type molecules) in an NMR compatible solvent. We discuss how these complementary methods have been employed to monitor SOM responses to: soil warming in a temperate forest, elevated atmospheric CO(2) and nitrogen fertilization in a temperate forest, and permafrost thawing in the Canadian High Arctic. These molecular-level methods allow some novel and important observations of soil dynamics and ecosystem function in a changing climate.     

工业温室气体CO2排放监测技术前期研究

介绍了国内外二氧化碳（ CO2）气体检测方法,选取红外传感器、非分散红外和气相色谱3种方法监测工业燃煤废气中的CO2。试验结果表明,3种方法的精密度和准确度均满足要求;单一燃煤废气中CO2的体积分数范围为6．70％～15．10％,同一排气筒中CO2体积分数5 min的波动范围为0～22．4％;同一排气筒（单一燃煤废气）中CO2和O2的体积分数有一定的关联性,二者之和基本稳定在19％～21％范围;非分散红外法和气相色谱法测定同一样品的相对偏差为0．9％～3．4％;红外传感器适用于有组织排放的现场监测,另2种方法适用于无组织废气和环境空气监测。     

北京市大气气态汞变化特征

采用Tekran 2537X大气汞分析仪在线测量北京市城区大气中气态元素汞(GEM,简称大气汞) 浓度,研究大气汞浓度随不同气象条件的变化特征。通过分析2016年10月—2017年9月大气汞监测数据发现,该监测点全年大气汞浓度为0.48～16.25 ng/m³,均值为(3.41±1.79)ng/m³。春季、夏季、秋季和冬季大气汞浓度均值依次为2.93 、2.95、4.27、3.37 ng/m³,其中,秋季大气汞浓度明显高于其他季节 。秋季大气汞浓度显著偏高可能由不利的大气扩散条件导致。大气汞夜间浓度显著高于白天浓度。同时,将大气汞与SO₂、CO及PM_2.5进行相关性分析,发现大气汞浓度变化趋势与SO₂、CO和PM_2.5呈显著正相关。结合风向和风速进行污染来源分析,得到该点位大气汞在西南和东北方向上受人为排放源影响较大。污染源类型分析表明,冬季大气汞与CO同源性强,主要来自本地供暖用煤。     

Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid

A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 microL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a light emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is approximately 2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min-1. The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.     

Analysis of Pesticides Using a Polyppyrole Modified Electrode

Electrochemical methods can provide fast, sensitive and sometimes real time detection of pesticides. In the course of this work, a dispersed mercury electrode has been used to detect pesticides electrochemically. The electrode was prepared by depositing a thin mercury film on a glassy carbon disc and then coating a layer of polypyrrole on the disc. The effect of coating thickness on detection sensitivity was studied. A thin mercury film of 0.34 µm dispersed by one cycle polymerization of pyrrole was preferred. The influence of electrolyte, pH and organic solvent content on pesticide response was also investigated. The polypyrrole dispersed mercury electrode (Hg-PPy/GC) was not suitable for a pH above 6 but it can tolerate acetonitrile up to 10% at which concentration the mercury film coated glassy carbon electrode (Hg/GC) failed to response. Methyl parathion, methyl azinphos, parathion and fenitrothion were detected. The sensitivity of the dispersed mercury electrode was similar to a normal thin mercury film electrode in this case. A good response can be obtained for 1 ppm pesticides using fast linear sweeping voltammetry.     

Field intercomparison of diffusive samplers for measuring ammonia

Agricultural production systems are recognised as a major source of atmospheric ammonia. Deposition of ammonia and ammonium may contribute to undesired changes in oligotrophic ecosystems. The continuous measurement of atmospheric ammonia requires expensive and sophisticated techniques and is performed only in a very restrict number of ambient air stations in Europe. Therefore, the application of passive samplers, which have the advantage of being easy to handle and cost-efficient, is useful. In the past the comparability of different passive samplers must be considered as rather scarce. In a joint European project under the leadership of the GSF-Forschungszentrum für Umwelt und Gesundheit, Neuherberg, in 1997 a comparison of different passive ammonia monitoring methods was carried out in a prealpine rural site near Garmisch-Partenkirchen. It was considered valuable to include not only well established systems but also methods still being developed. For the comparative test ten working groups with different methods took part. A wet annular denuder system, which has been developed by the Netherlands Energy Research Foundation for on-line measurement of atmospheric ammonia, served as reference of passive methods. The experiment, which started in June and finished in December, showed that most of the passive samplers fulfil the requirements and can be recommended for further measurements. Additional measurements of meteorological parameters were performed to check the influences of different weather conditions on passive sampling.     

A generalized analytical solution for turbulent dispersion with inhomogeneous wind and diffusion coefficient

A technique is presented to solve analytically the turbulent diffusion equation for the concentration of a passive contaminant emitted from an elevated continuous source into the atmosphere. A generalized method of solution using Sturm–Liouville and WKB theories is developed to overcome difficulties due to the height‐dependent wind velocity and diffusion coefficient appearing in the diffusion equation. The method presented in this paper is able to derive an asymptotic expression for the concentration obtained from the solution of the atmospheric diffusion equation which involves explicitly inhomogeneous wind velocity and diffusion coefficient. The diffusion equation model derived from this method can be applied in a practical prediction of contaminant concentration in a turbulent atmosphere. This revised version was published online in August 2006 with corrections to the Cover Date.     

南京市臭氧、VOCs和PANs污染特征及变化趋势

对2013—2016年基于国家环境空气质量监测站以及省建大气多参数站所获取的南京市O_3、NO_2、CO、VOCs、PANs观测结果进行综合评价,结果表明:2016年南京市O_3第90百分位日最大8 h平均质量浓度比2013年上升33.3%,超标天数中O_3引起的超标占比增至32.0%。南京市区大气中非甲烷总烃冬季浓度高于夏季,含氧挥发性有机物则与之相反;在5—9月,含氧挥发性有机物组分在日变化过程中出现峰值的时间先后顺序依次为醚、醛、酮类,且O_3和过氧乙酰硝酸酯(PANs)生成存在有一定的线性关系。VOCs/NOx比值表明南京市处于VOCs控制区,因此对NO_2浓度下降不敏感,植物源挥发性有机物连续3年上升,夏季大气光化学反应活性未显著下降,这些现象是城市O_3浓度维持在较高水平的重要因素。     

Development of low-cost ammonia gas sensors and data analysis algorithms to implement a monitoring grid of urban environmental pollutants

The present study is focused on the implementation of a novel, low cost, urban grid of nanostructured chemresistor gas sensors for ammonia concentration ([NH(3)]) monitoring, with NH(3) being one of the main precursors of secondary fine particulate. Low-cost chemresistor gas sensors based on carbon nanotubes have been developed, their response to [NH(3)] in the 0.17-5.0 ppm range has been tested, and the devices have been properly calibrated under different relative humidity conditions in the 33-63% range. In order to improve the chemresistor selectivity towards [NH(3)], an Expert System, based on fuzzy logic and genetic algorithms, has been developed to extract the atmospheric [NH(3)] (with a sensitivity of a few ppb) from the output signal of a model chemresistor gas sensor exposed to an NO(2), NO(X) and O(3) gas mixture. The concentration of these pollutants that are known to be the most significant interfering compounds during ammonia detection with carbon nanotube gas sensors has been tracked by the ARPA monitoring network in the city of Milan and the historical dataset collected over one year has been used to train the Expert System.     

Hydrology-linked spatial distribution of pesticides in a fjord system in Greenland

A pilot study is presented evaluating selected chlorinated pesticides as chemical tracers for water masses in a sub-Arctic fjord system (Godth?bsfjord, western Greenland). Polyoxymethylene (POM) based passive water samplers were deployed during summer-autumn 2010. The levels of the analysed chlorinated pesticides in the fjord surface waters were found to be low compared to earlier studies. α-Hexachlorocyclohexane (α-HCH) and hexachlorobenzene (HCB) were the predominant contaminants. However, these two compounds have higher levels in oceanic water compared to freshwater influenced fjord waters. These chemicals can thus be considered as indicators for direct atmospheric long-range transport, while the organochlorine pesticides like trans-, cis-chlordane, trans-nonachlor and oxychlordane that are detected in the inner parts of the fjord are indicators for potential freshwater sources such as rivers and glacial meltwater runoff (secondary sources). The average values were 50 pg L(-1) for HCB and 11 pg L(-1) for α-HCH. These concentrations are comparable to levels in fjords in Svalbard (Norwegian Arctic), but lower than in open and/or ice covered oceans in the Canadian Arctic. Two air samplers were deployed for the identification of direct atmospheric contributions. Local contamination sources do not contribute significantly. The study demonstrated the value of passive water sampling devices for comprehensive hydrological characterization of Arctic coastal waters.     

大气环境高灵敏光谱探测技术

大气环境高灵敏光谱探测技术是以光与环境相互作用为基础发展起来的学科交叉方向,使用光学的方法和手段来探知研究环境问题。大气环境高灵敏光谱探测技术能够实现从现场瞬态灵敏探测到污染时空分布等不同尺度的遥测,从而获得大气污染"点-线-面"的时空变化规律,由于光谱探测技术具有多组分、非接触、无采样、高灵敏度、大范围快速以及遥测等特点,已经成为国际上大气环境监测技术的主要方向之一。大气环境高灵敏光谱技术在污染源、工业园区、空气质量以及区域污染等监测方面都有很广泛的应用。针对化工园区复杂的环境污染问题,光谱探测技术可以高灵敏、非接触地获取多种污染物浓度特征,掌握化工园区污染时空分布状况,为化工园区的大气污染治理提供有效支撑;针对京津冀、长三角等地区大气重污染过程的核心问题,大气环境高灵敏光谱探测技术通过地基组网观测,车载/机载平台移动观测等三维立体监测手段获取重点区域污染物的生成、转化过程以及重污染过程的形成机制,为区域大气污染成因追溯、污染控制措施评估提供科学的数据和技术支撑。高灵敏光谱探测技术在大气环境领域的成功应用,为污染源、化工园区和重点区域的环境综合诊断和治理奠定了技术基础。     

Carbon Monoxide Concentration in a Street Canyon of Buenos Aires City (Argentina)

The analysis of three years of 8-h CO concentration values registered in a deep street canyon downtown shows high frequency of values that exceed WHO health protection guidelines. An inverse relationship between opposing percentiles of the distributions of CO concentrations and mean wind speed could be found. Data also showed a variation of mean CO values with prevailing wind direction. The averaged concentration value obtained when the sampler probe is on the leeward side is lower than the obtained when it is on the windward wall. A preliminary explanation of this feature may be related to the advection of polluted air from a high traffic density area nearby.     

基于厚膜传感器的空气质量监测仪性能及应用研究

介绍了一种基于厚膜传感器技术,可同时测量NO2、O3、CO三个因子的空气质量监测仪器。深入研究了仪器的检测原理,并对仪器的质量保证及数据存储传输进行了详细介绍。最后对仪器的检测性能进行了对比分析,通过和常规点式仪器的对比表明,该仪器NO2、O3、CO三因子的检测性能能够满足实际监测要求。另外,该仪器还具有集成性好、安装调试方便等特点,因此,在道路交通监测等领域中有广泛的应用前景。