新疆大气氮沉降监测研究进展浅析

通过对新疆12个监测点氮沉降研究结果发现,无机活性氮浓度(p NH 4+、p NO 3-、NH 3、NO 2)在不同生态系统存在较大的时空差异,氮沉降通量变化随人为干扰程度呈递增趋势。总结了当前新疆大气氮沉降监测研究进展,包括主要监测方法、不同生态系统大气氮素干沉降的时空差异性分析、大气氮素干湿沉降通量估算。对大气氮素干湿沉降通量的整体估算、不同生态系统的监测常态化等还存在不足,未来评估氮沉降的综合气候效应、定量临界负荷以及生态系统对氮沉降通量急剧增加的响应是今后研究的重点方向。     

火焰原子吸收光谱法测定大气飘尘中的痕量Pb Cu Mn Fe Ca Mg

大气飘尘中往往含有多种金属元素,对人体有严重的生理影响,所以,大气飘尘中金属元素的分析已受到卫生防疫和环境监测部门的日益重视.对大气飘尘中金属元素的分析,早期一般采用化学法,目前更多的是应用仪器分析方法.如中子活化、原子吸收光谱和发射光谱等方法.原子吸收光谱法由于其灵敏度较高、干扰较少、设备价格相对低廉,是测定大气飘尘中金属元素可选择的方法.尽管大气飘尘中有些金属元素含量甚微,用火焰原子吸收法测定,其灵敏度难以达到要求,但我们采取了采样时间长、过滤大气体积量多的简单方法,解决了灵敏度的问题.     

灰霾期间武汉城市区域大气污染物的理化特征

利用湖北省大气复合污染自动监测站2013年的全年监测数据,分析了灰霾期间武汉城市区域大气污染物的理化特征。霾日主要出现在春季、秋季和冬季。霾日与非霾日大气污染物质量浓度和气象参数的对比分析结果显示:高湿度、静风是武汉城市区域霾日的重要气象特征;PM1、PM_(2.5)、PM_(10)、NO_2、CO、NH3的质量浓度,SOR、NOR值以及PM_(2.5)中的二次无机离子(SO2-4、NO-3、NH+4)和部分元素(Pb、Se、Cd、Zn、K)的质量浓度均在霾日明显高于非霾日,而霾日SO2质量浓度仅在冬季略高于非霾日。选取2013年1月的连续灰霾日进行相关性分析,结果表明:污染组分主要来自当地排放(包括直接排放和二次形成),并受当地气象条件影响。此次灰霾过程中PM_(2.5)中的硫酸盐和硝酸盐主要来自气相反应,气态NO_2主要生成了气态HNO_3,而不是HNO_2。     

广州市灰霾期PM10的化学组成对能见度的影响

采集广州市大气可吸入颗粒物(PM10)样品,并分别对冬、夏两季灰霾和非灰霾期PM10中有机碳(OC)、元素碳(EC)和水溶性离子进行分析。广州市灰霾期大气PM10中的主要化学成分按质量浓度大小排序为OC>NO3->SO24->NH4+>EC(非灰霾期则依次为OC>SO24->EC>NH4+>NO3-),其质量浓度分别为非灰霾期的4.7、12.5、3.7、3.2和2.3倍。相关性分析表明,灰霾期总碳[TC(OC+EC)]及NO3-的质量浓度对大气能见度的降低起主要作用,而非灰霾期则主要是TC和SO24-。     

二氧化硫光谱检测技术

介绍了二氧化硫的性质,综述了紫外荧光分析检测技术、长程吸收光谱检测技术、激光红外吸收检测技术和遥感傅里叶变换红外光谱检测技术的原理及在二氧化硫检测中的应用。     

东南沿海典型岛屿大气降水化学特征及来源分析

于2020年6月—2021年5月,应用相关分析、富集因子(EF)以及正定矩阵因子分解模型(PMF)和气团来源分析对东南沿海岛屿平潭大气降水化学特征及来源进行了综合评价与分析。结果表明,平潭大气降水pH值为3.96~7.49,平均值为4.78;电导率(EC)为4.9~342.0μs/cm,平均值为24.4μs/cm,高于我国降水背景点值;大气降水中各离子组分当量浓度排序为:Cl->Na+>SO_(4)^(2)>NO-3>Ca 2+>NH+4>Mg 2+>K+>F->NO-2,Cl-和Na+是降水中占比最大的阴、阳离子,其当量浓度占总离子当量浓度的51.4%;NO-3对平潭大气降水酸化的贡献较高(55.9%),且有77%的大气降水酸度被碱性物质中和,其中铵根离子(NH+4)和钙离子(Ca 2+)有着较强的中和能力。富集因子分析结果表明,除海洋源外,地壳源和人为源也是平潭大气降水离子的主要来源;PMF模型结果显示,海洋源、人为源、地壳源和燃烧源分别贡献了平潭大气降水离子的61.1%,23.8%,10.0%和5.1%;气团来源分析结果表明,区域传输对平潭大气降水离子分布及空气质量影响显著,京津冀和长三角地区排放的人为污染物可以经海上传输通道由北至南影响我国下风向地区,给沿海地区大气细颗粒物(PM_(2.5))与臭氧(O_(3))协同控制带来挑战。     

光电技术在大气氮氧化物检测中的应用

介绍了大气中氮氧化物的组成，综述了激光诱导荧光法、光纤传感法、激光雷达探测法和化学发光法测定大气中氮氧化物的原理和特点，指出光电技术已在大气氮氧化物检测中得到了广泛的应用，并具有良好的发展前景。     

燃煤工业城市大气细颗粒物中水溶性无机离子的季节变化特征及来源解析——以邯郸市为例

为探究典型燃煤工业城市邯郸市的大气细颗粒物(PM2.5)污染水平及水溶性无机离子特征,于2016年1—12月采集了当地大气PM2.5样品,然后利用离子色谱法测得水溶性无机离子的组分,分析了不同季节水溶性无机离子随PM2.5的浓度变化特征。通过对PM2.5中的阴离子、阳离子进行分析发现,SO4^2-、NO3^-和NH4^+在春夏秋冬四季均为PM2.5中的主要离子成分,SO4^2-、NO3^-和NH4^+的浓度之和在春夏秋冬四季占各季节总的水溶性无机离子浓度的百分比分别为84.6%、77.4%、89.9%、62.5%。其中,在春季和冬季含量最高的3种离子分别是NO3^-、SO4^2-和NH4^+,夏季含量最高的3种离子分别是SO4^2-、NH4^+和NO3^-,而秋季含量最高的3种离子分别是NH4^+、SO4^2-和NO3^-。相关性分析发现,2016年春季、夏季和秋季PM2.5为酸性,冬季为碱性。SO4^2-、NO3^-、NH4^+浓度分析表明,冬季PM2.5中的一次建筑扬尘排放较多。通过主成分分析法得出,PM2.5中水溶性无机离子主要来源于二次转化和生物质燃烧。     

石墨炉原子吸收法在环境样品测定中的应用

评述了石墨炉原子吸收光谱法在环境样品测定中的应用 ,内容包括装置与技术、水与废水、土壤与底质 ,以及大气与废气     

PUF大气被动采样技术对POPs的采样计算

随着《斯德哥尔摩公约》的实施,大气中持久性有机污染物(POPs)的大气被动采样(PAS)观测技术得到了快速发展,相比于传统大气主动采样技术,PAS技术具有明显的优势。以应用最为广泛的聚氨酯软性泡沫材料大气被动采样(PUF-PAS)为例,重点阐述和讨论了3种通过大气被动采样技术来计算污染物在空气中的浓度的方法,并对其采样原理和发展趋势进行了简要介绍。     

Retrieval And Monitoring of Atmospheric Trace Gas Concentrations in Nadir and Limb Geometry Using the Space-Borne Sciamachy Instrument

The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) onboard the European Envisat spacecraft performs continuous spectral observations of reflected, scattered and transmitted sunlight in various observation geometries. A unique feature of SCIAMACHY is the capability of probing the atmosphere in three different observation geometries:The nadir, limb, and occultation measurement modes. In nadir mode, column densities of trace gases are retrieved with a spatial resolution of typically 30× 60 km using the Differential Optical Absorption Spectroscopy (DOAS) technique (Platt and Perner, 1983). Alternating with the nadir measurement, vertical profiles of absorber concentration in the stratosphere are derived in limb and occultation. In this paper we present an overview over some applications of SCIAMACHY data in space-based monitoring of atmospheric pollution. The DOAS algorithms for the retrieval of total column amounts from nadir spectra are briefly described and case studies of pollution events are presented. We also illustrate the technique used to derive stratospheric concentration profiles from limb observations and show comparisons with other remote sensing systems. Special emphasis will be given to techniques, which take advantage of SCIAMACHY's different viewing geometries. In particular, we will discuss the potential and limits of strategies to infer tropospheric abundances of O₃and NO₂.     

Support Vector Machine Modeling Using Particle Swarm Optimization Approach for the Retrieval of Atmospheric Ammonia Concentrations

This study was performed in order to improve the estimation accuracy of atmospheric ammonia (NH₃) concentration levels in the Greater Houston area during extended sampling periods. The approach is based on selecting the appropriate penalty coefficient C and kernel parameter σ ². These parameters directly influence the regression accuracy of the support vector machine (SVM) model. In this paper, two artificial intelligence techniques, particle swarm optimization (PSO) and a genetic algorithm (GA), were used to optimize the SVM model parameters. Data regarding meteorological variables (e.g., ambient temperature and wind direction) and the NH₃ concentration levels were employed to develop our two models. The simulation results indicate that both PSO-SVM and GA-SVM methods are effective tools to model the NH₃ concentration levels and can yield good prediction performance based on statistical evaluation criteria. PSO-SVM provides higher retrieval accuracy and faster running speed than GA-SVM. In addition, we used the PSO-SVM technique to estimate 17 drop-off NH₃ concentration values. We obtained forecasting results with good fitting characteristics to a measured curve. This proved that PSO-SVM is an effective method for estimating unavailable NH₃ concentration data at 3, 4, 5, and 6 parts per billion (ppb), respectively. A 4-ppb NH₃ concentration had the optimum prediction performance of the simulation results. These results showed that the selection of the set-point values is a significant factor in compensating for the atmospheric NH₃ dropout data with the PSO-SVM method. This modeling approach will be useful in the continuous assessment of NH₃ sensor discrete data sources.     

Reduction of SO2 emissions by ammonia gas during unstaged combustion

The reduction of SO₂ by the addition of ammonia gas has been studied in a 2 m high fluidized bed combustor having a 30 cm static bed height and a freeboard height of 170 cm. Ammonia gas was injected at 52 cm above the distributor where the temperature is ca. 700° C by an uncooled stainless steel tube injector. Experiments were carried out to investigate the effects of amminia gas injection on sulphur dioxide emissions at unstaged conditions of: (i) excess air level, (ii) NH₃:SO₂ molar ratio, (iii) fluidizing velocity and (iv) bed height.A maximum reduction of 75% in SO₂ emissions was found at 40% excess air, at an NH₃:SO₂ molar ratio of 5.4. The onset of SO₂ reduction occurred at an NH₃:SO₂ ratio of 1.5 However, the most effective ratio was found to be between 3 and 5. Fluidizing velocity and bed height were also found to have significant influence on SO₂ reduction.It is difficult to determine how the SO₂ reduction varied with operating conditions. When ammonia is added in the main combustor zone, the temperature is much higher than that required for the occurrence of sulphur dioxide-ammonia and sulphur trioxide-ammonia reactions. However, this paper points out the significance of ammonia addition in the reduction of sulphur dioxide.     

Simultaneous Measurements of Atmospheric Pollutants and Visibility with a Long-Path DOAS System in Urban Areas

In this paper, the applicability of a Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) system was checked for the feasibility of the simultaneous measurement of trace gases (such as O₃, NO₂, SO₂, and HCHO) and atmospheric visibility (light extinction by aerosols) in Asian urban areas. Field studies show that an LP-DOAS system can simultaneously measure the key pollutants (such as O₃, NO₂, SO₂, and HCHO) at detection limits in the ppb/sub-ppb range as well as the Mie extinction coefficient with an uncertainty of 0.1 km^–1 at time resolution of a few minutes. It is thus concluded that the use of LP-DOAS system is feasible for simultaneous measurement of gaseous pollutants as well as an atmospheric extinction coefficient which is tightly bound to fine particulate concentration.     

Study on concentration of ambient NH 3 and interactions with some other ambient trace gases

We present diurnal variation of ambient ammonia (NH₃) in relation with other trace gases (O₃, CO, NO, NO₂, and SO₂) and meteorological parameters at an urban site of Delhi during winter period. For the first time, ambient ammonia (NH₃) was monitored very precisely and continuously using ammonia analyzer, which operates on chemiluminescence method. NH₃ estimation efficiency of the chemiluminescence method (>90%) is much higher than the conventional chemical trapping method (reproducibility 4.5%). Ambient NH₃ concentration reaches its maxima (46.17 ppb) at night and minimum during midday. Result reveals that the ambient ammonia (NH₃) concentration is positively correlated with ambient NO (r ²?=?0.79) and NO₂ (r ²?=?0.91) mixing ratio and negatively correlated with ambient temperature (r ²?=???0.32). Wind direction and wind speed indicates that the nearby (~500 m NW) agricultural fields may be major source of ambient NH₃ at the observational site.     

The Effects of Ammonia on SO2 Emissions in a Fluidized Bed Combustor Under Pseudo-Staged Combustion

The reduction of SO₂ by ammonia gas additionduring staged combustion of bituminous coal has beenstudied in a 2 m high fluidized bed combustor of 30 cmstatic bed height and a freeboard height of 100 cm.The coal was introduced to the combustor at 42 cmabove the distributor and the ammonia gas was injectedat 52 cm above the distributor by an uncooledstainless steel injector. Experiments were carriedout to investigate effects of ammonia gas injection onSO₂ emissions of (i) air staged levels, (ii) excess air levels, (iii) primary air factor, PAF(ratio of primary to stoichiometric air), (iv) NH₃:SO₂ molar ratio, and (v) fluidizingvelocity. Experiments were carried out under a newtechnique of air staging called Pseudo-stagedCombustion, maintaining the excess air level andfluidizing velocity between 17 and 70% and between0.7 and 2.0 m sec^-1, respectively. A maximum reduction of92% was obtained at 37% excess air, at NH₃:SO₂ molar ratio of 5.5. The effective NH₃:SO₂ molar ratio was found to be between 3.0 and5.5, which is true for all staging and excess air levels.A greater removal of SO₂ with NH₃ injectionduring staged combustion is probably due to this newstaging technique. The Pseudo-staging reducestemperature through the freeboard and flue for theoccurance of as NH₃ + SO₂ reactions. Thesereactions are reported to be low temperaturereactions. The NH₃ carry over was less than 83 ppm for all operating conditions. The present studydemonstrates that staged combustion coupled withammonia injection can reduce SO₂ emissions.     

Case studies on summertime measurements of O3, NO2, and SO2 with a DOAS system in an urban semi-industrial region in Athens, Greece

The objective of this study is to analyze the concentrations of SO₂, NO₂, and O₃ measured by a Differential Optical Absorption Spectroscopy (DOAS) system that was operating at the campus of Technological Education Institute of Piraeus during 2008 and 2009 warm periods (July to September) in relation to the prevailing meteorological conditions. The DOAS system was operating in a particularly polluted area of the West part of Attica basin on a continuous basis, measuring the concentration levels of the main pollutants (O₃, NO₂, and SO₂) as well as aromatic hydrocarbon substances (benzene, toluene, and xylene). According to the analysis, the SO₂ concentration levels at this measuring site are rather high and this may be attributed to the characteristics of this measuring site. Proximity of roadways and local circulation are just some of the factors that can affect the concentration levels of monitoring of pollutant concentrations such as NO₂ and surface ozone. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect.     

Odour emission characteristics of 22 recreational rivers in Nanjing

The odour emission characteristics of 22 recreational rivers in Nanjing were investigated and analysed. Eight odorous compounds (ammonia (NH₃), hydrogen sulphide (H₂S), sulphur dioxide (SO₂), carbon disulphide (CS₂), nitrobenzene (C₆H₅NO₂), aniline (C₆H₅NH₂), dimethylamine (C₂H₇N), and formaldehyde (HCHO)) were measured in odour emission samples collected using a custom-made emission flux hood chamber. The results showed that all odorants were detected in all monitoring rivers. NH₃ was the main odorant, with emission rates ranging from 4.86 to 15.13 μg/min m². The total odour emission rate of the Nan River, at 1 427.07 OU/s, was the highest of the all investigated rivers. H₂S, NH₃ and nitrobenzene were three key odour emission contributors according to their contributions to the total odour emission. A correlation analysis of the pollutants showed there was a significant positive correlation between the emission rate of NH₃ and the concentration of ammonia nitrogen (NH₄ ⁺-N) and total nitrogen (TN). The H₂S and SO₂ emission rates had a significant positive correlation with sulphides (S^2?) and available sulphur (AS) in the water and sediment. The content of TN, NH₄ ⁺-N, S^2? and AS in the water and sediment affected the concentration of H₂S, SO₂ and NH₃ in the emission gases. NH₄ ⁺-N, S^2? and AS are suggested as the key odour control indexes for reducing odours emitted from these recreational rivers. The study provides useful information for effective pollution control, especially for odour emission control for the recreational rivers of the city. It also provides a demonstrate example to show how to monitor and assess a contaminated river when odour emission and its control need to be focused on.     

Second derivative spectroscopy for the determination of volatilized ammonia from urea-amended soil

A second derivative spectrometer custom fitted with a 1 m stainless steel White cell and maintained at 105°C is used to make real-time measurements of volatilized NH₃ from urea-amended soil. Comparison of the technique to impinger data shows a 5–16% discrepancy between the two techniques; however, other experiments presented suggests that this is not real. Sulfur dioxide and nitrous oxide interferences are discussed, though they were not found to be present in this study. Instrument response time is shown to be fast if 67% of the total response is achieved in less than 5 min. Fast response is achieved for ammonia if wall-adsorption effects are minimal and if ammonia mass flow is maintained at 0.2 μg min^-1.     

北京市某典型污水处理厂氨气排放研究

在污水处理厂的格栅、沉砂池、初沉池、曝气池、二沉池采集气样,同时采集相应点位水样,分析各点位氨气排放特征及其与污水指标间相关性。在格栅间、污泥脱水间收集氨气浓度分析密闭车间氨气排放量,结果表明:水气界面格栅间氨气排放浓度最高,随着处理工艺的进行,氨气排放浓度呈下降趋势;氨气排放浓度与污水中氨氮浓度及总氮浓度有较好的线性关系;沉砂池及初沉池氨气挥发速率远高于曝气池和二沉池;各工艺段氨气排放量差异较大,污水厂污水氨气排放量为922 mg/m~3,初沉池对污水厂氨气贡献率最高,为78.8%。