Biochemical responses in tree foliage exposed to coal-fired power plant emission in seasonally dry tropical environment

A biomonitoring study was conducted to investigate the responses of plants exposed to power plant emission in a dry tropical environment. For this purpose, five sampling sites were selected in the prevailing wind direction (NE) at different distance to thermal power plant (TPP) within 8.0 km range and a reference site was selected in eastern direction at a distance of 22.0 km. The two most common tree species, Ficus benghalensis L. (Evergreen tree) and Dalbergia sisso Roxb. (deciduous tree) were selected as test plants. Ambient sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)), suspended particulate matter (SPM), respirable suspended particulate matter (RSPM), dust-fall rate (DFR) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b and carotenoids), ascorbic acid, sugar and sulphate-sulphur (SO4(2-)-S) contents were measured. Ambient SO(2), NO(2), SPM, RSPM and DFR showed significant spatial and temporal variation at different sites. Considerable reduction in pigment (chlorophyll a, chlorophyll b and carotenoids) and sugar contents were observed at sites receiving higher pollution load. Ascorbic acid exhibited significant positive correlation with pollution load. Accumulation of SO4(2-)-S in leaf tissue showed significant positive correlation with ambient SO(2) concentration at all the sites. At the same time, SO4(2-)-S showed significant negative correlation with pigment and sugar content. D. sisso Roxb. tree was found to be more sensitive as compared to F. benghalensis L. tree.     

基于ＧＩＳ的乌鲁木齐市ＮＯ２ 时空分布特征

以乌鲁木齐市2008-2012年7个空气自动监测点位小时浓度数据为基础数据,利用ArcGIS 技术,分析了其NO2年变化、月变化、日变化、空间分布等污染特征。结果表明,NO2年均值为0．065～0．068 mg/m3,基本保持稳定;NO2呈明显的季节变化,冬季污染较重,春节、秋季次之,夏季空气质量相对较好;NO2呈现“单峰型”的日变化特征,夜间NO2明显高于白天;不同季节 NO2的空间分布特征不同,与交通、供暖、人口密度、地理位置密切相关;NO2分布与风速相关关系明显,而与气温、湿度的关系为非线性。     

Modelling mixing height from routinely measured surface and upper air meteorological data

A one‐dimensional model is developed for the estimation of hourly mixing height values from routinely measured upper air and surface meteorological data. A diagnostic technique is used in the model to calculate the convective and mechanically induced mixing height values under different atmospheric, and day and night‐time conditions. In the scheme, for the day‐time hours, the mixing height is determined as the larger of the convective and mechanically induced mixing height values. For the night‐time hours, only the mechanically induced mixing height values are considered. Three‐hourly mixing height values are modelled using once‐a‐day upper air temperature profile data (from radio‐sonde) and three‐hourly surface meteorological data. The spatial and temporal variation of mixing height are modelled in the Brisbane airshed and their relationship with the atmospheric stability, solar radiation and transport wind speed is developed.     

Evaluation of the best compromise between the urban air quality monitoring resolution by diffusive sampling and resource requirements

The need to collect data representative of overall urban pollution is all-important in order to monitor the population exposure. High spatial resolution monitoring using diffusive samplers allows studying of the urban pollutant distribution, thus enabling deeper investigation of their generation and diffusion mechanisms. Nevertheless, such a monitoring campaign has a certain cost. In this study we point out how to find the best compromise between the number of necessary measurements and the affordable costs for monitoring campaigns. We also describe an innovative method for the proper design of a fixed urban monitoring network by means of preliminary high spatial resolution campaigns using diffusive samplers. Four European capital cities (Dublin, Madrid, Paris and Rome) were monitored six times, each time for seven days. Benzene, toluene, ethylbenzene, xylenes (BTEX) and NO(2) concentrations were measured at 146 sites in Dublin, 293 in Madrid, 339 in Paris and 290 in Rome. Multiscale grids have been drawn which ranged in mesh size from 500 m to 2 km. The statistical processing of data produced a twofold result: the creation of isoconcentration maps with geostatistical procedures, and an algorithm aimed at locating the minimum number of sampling sites where the fixed monitoring stations should be placed. Average urban levels estimated on the basis of these selected sites differ by less than 8% from those calculated on the whole populations of the sampled points. The aim of this work is to investigate how far the resolution of a monitoring campaign of urban pollution by diffusive sampling can be reduced, thus making the monitoring less expensive in terms of human and financial resources, while preserving the same quality of the results that could be achieved with a higher resolution. We found that there is no significant loss of information when the resolution of the monitoring grid for BTEX is lowered to a mesh size of 1.85 km, that is a sampling site each 3.4 km(2), and that the minimum number of sampling sites to be used is N = 0.29 A, where A is the urban surface to be monitored (in km(2)). As the spatial distribution of NO(2) is less sensitive to the distance from the emission source than that of BTEX, this relationship could be retained as a valid lower limit for the mesh grid size also for NO(2) monitoring.     

The relationship between typhoons' peripheral circulation and ground-level ozone concentrations in central Taiwan

Surface data of meteorological parameters (wind speed, wind direction, and mixing height) and air pollutant concentrations (O₃, NO, and NO₂) were collected for a 92-day period associated with typhoon formation in 2005. The influence of typhoons on O₃ concentration were defined by azimuth and distance from Taiwan, and Types A, B, and C correspond to typhoons less than 1,500 km from Taiwan and located between azimuths 45° and 135°, 135° and 225°, and 225° and 45°, respectively. Type D corresponds to typhoons more than 1,500 km from Taiwan. Titration reactions were conducted at three temporal phases: 2000–0700, 0800–1100, and 1200–1400 LST (Local Standard Time). The air pollution model (TAPM) was used to simulate wind fields and trajectories of air masses. It was determined that typhoon position affected O₃ concentration, temporal and spatial patterns of O₃ titration and vertical meteorological characteristics, which were not all at the statistically significant level.     

Factors controlling the accumulation of metals within fluvial systems

The magnitude and distribution of European Community (EC) regulated List I and List II metals and metalloids have been investigated in two lowland river systems in East Anglia, U.K. A combination of sediment and water quality data identified municipal sewage treatment work discharges as the main metal input sources to the river systems and identified two main areas of metal contamination: the Pix Brook, downstream of Letchworth STW on the River Ivel, and a 14 km enrichment zone adjacent to Whitlingham STW on the River Yare. The basement geology, flow dynamics, distance from point sources and sediment type were identified as important controls upon the magnitude and spatial distribution of metal contaminants.     

Mathematical models for accurate prediction of atmospheric visibility with particular reference to the seasonal and environmental patterns in Hong Kong

Atmospheric visibility impairment has gained increasing concern as it is associated with the existence of a number of aerosols as well as common air pollutants and produces unfavorable conditions for observation, dispersion, and transportation. This study analyzed the atmospheric visibility data measured in urban and suburban Hong Kong (two selected stations) with respect to time-matched mass concentrations of common air pollutants including nitrogen dioxide (NO(2)), nitrogen monoxide (NO), respirable suspended particulates (PM(10)), sulfur dioxide (SO(2)), carbon monoxide (CO), and meteorological parameters including air temperature, relative humidity, and wind speed. No significant difference in atmospheric visibility was reported between the two measurement locations (p > or = 0.6, t test); and good atmospheric visibility was observed more frequently in summer and autumn than in winter and spring (p < 0.01, t test). It was also found that atmospheric visibility increased with temperature but decreased with the concentrations of SO(2), CO, PM(10), NO, and NO(2). The results showed that atmospheric visibility was season dependent and would have significant correlations with temperature, the mass concentrations of PM(10) and NO(2), and the air pollution index API (correlation coefficients mid R: R mid R: > or = 0.7, p < or = 0.0001, t test). Mathematical expressions catering to the seasonal variations of atmospheric visibility were thus proposed. By comparison, the proposed visibility prediction models were more accurate than some existing regional models. In addition to improving visibility prediction accuracy, this study would be useful for understanding the context of low atmospheric visibility, exploring possible remedial measures, and evaluating the impact of air pollution and atmospheric visibility impairment in this region.     

Spatio-temporal variation in physicochemical properties of coastal waters off Kalpakkam, southeast coast of India, during summer, pre-monsoon and post-monsoon period

Seasonal observations on water-quality parameters and chlorophyll-a in the coastal waters off Kalpakkam, southeast coast of India, was carried out covering an area of about 30 km(2) to find out the variations in physicochemical properties during a monsoonal cycle of the year. Most of the parameters exhibited a significant spatial and seasonal variation. It revealed that the coastal water was significantly influenced by freshwater input from the nearby backwaters during North-east monsoon and post-monsoon periods. A marginal increase in pH from coast towards offshore was noticed during the observation. Relatively low salinity values were observed during pre and post monsoon when compared to summer. Bottom water was found to be highly turbid during summer and pre-monsoon conditions when compared to surface. This could be attributed to the strong northerly wind and northward current prior to the onset of southwest monsoon. N, P and Si based nutrients are relatively high in their concentration in the bottom water. Nitrate was significantly high during post-monsoon and contributed greatly towards total nitrogen as evident from the statistical correlation. Ammonia concentration was relatively high in the bottom samples during all the seasons except on a few occasions during post-monsoon. In general, phosphate and total phosphorous values remained low and particularly so in the surface water. Higher silicate concentration was observed in the bottom water, and there was a reducing trend towards offshore. High chlorophyll-a values were observed during summer and surface water was found to have higher pigment concentrations as compared to the bottom. Results show that phosphate acts as the limiting factor for phytoplankton production particularly during post-monsoon period whereas; none of the nutrients were found to be limiting the phytoplankton growth during other seasons.     

Filtering effect of wind flow turbulence on atmospheric pollutant dispersion

This paper presents a model for coupling the statistics of wind velocity distribution and atmospheric pollutant dispersion. The effect of wind velocity distribution is modeled as a three-dimensional finite-impulse response (3D-FIR) filter. A phase space representation of the 3D-FIR filter window is discussed. The resulting pollutant dispersion is the multiplication in the phase space of the 3-D Fourier transform of the pollutant concentration and the volume described by the filter window coefficients. The shape of the filter window in the phase space enables representing such effects as vortex shedding thermal currents, etc. The impact of spatial distribution of the sensors on the resulting pollutant spatial distribution and the 3-D FIR filter model employed also discuss. The case of a neutrally buoyant plume emitted from an elevated point source in a turbulent boundary layer considers. The results show that wind turbulence is an important factor in the pollutant dispersion and introduces expected random fluctuations in pollutant distribution and leads to spreading the distribution due to wind mixing.     

An observational case study of ozone and precursors inflow to South East England during an anticyclone

Summertime photochemical air pollution episodes within the United Kingdom have been proposed via modelling studies to be strongly influenced by regional scale inflow of air from the continental European boundary layer. We present a vertically resolved case study using measurements made from the NERC/Met Office BAe 146 research aircraft on 18th August 2005 over the South East of England and the North Sea during a weak anticyclone centred over Northern Europe. The vertical distribution of ozone, CO, NO(x), peroxyacetyl nitrate (PAN) and a wide range of both nonmethane hydrocarbons (NMHC) and oxygenated volatile organic compounds (OVOCs) were determined between 500 ft (approximately 152 m) and 7000 ft (approximately 2134 m) over the East Anglia coastline and 50 km inland. In excess of 80 ppbV ozone was observed within inflowing boundary layer air over the North Sea coast in a broad N-S sloping feature around 60 km wide. The inflowing feature of European origin was also observed further inland within the boundary layer albeit with lower, more variable, ozone mixing ratios. The increased variability in ozone over land was a product of titration by fresh surface emissions of NO via rapid upward transport in thermals, a hypothesis supported by the observed vertical wind speed component. Fast boundary layer mixing over land was further illustrated by a uniform distribution in reactive alkenes. A comparison between aircraft and surface O(3) UK AUN (Automatic Urban Network) measurements showed good agreement with the inland site, Sibton, but marked differences with the coastal monitoring site at Weybourne, potentially due to gradients established by ocean deposition in stably stratified marine air.     

Sixteen-year air quality data analysis of a high environmental risk area in Southern Italy

The Brindisi area is characterized by the presence of industries with high environmental impact, located along its eastern border. Epidemiological studies have revealed several critical situations: two short-term (2003-2005) epidemiological studies have shown that PM(10) and NO(2) are adversely associated with daily hospital admissions: one of the two pointed to the associations with wind blowing from the southern, eastern and western sectors. This study aims to expand the time span of available air quality data in order to provide a more complete and extensive epidemiological study. Multi-year series (from 1992 to 2007) of SO(2), NO(2), and TSP concentration data are presented and analyzed. Data show a significant downward trend of SO(2) from 1992 to 2007, while for the TSP series, the downward trend is limited to the period 1992-1994. Marked seasonal trends are evident for all three pollutants, especially for NO(2) and TSP. The NO(2) series shows higher levels in winter. Inversely, the TSP series shows its maximum values during the summer months, associated with a moderate correlation with temperature and a poor correlation with other pollutants. Analysis of the series for wind sectors revealed the influence of the industrial site and of the harbor. The concentration series exhibit high concentration values and stronger correlations between them and with meteorology for wind blowing from the eastern sectors. Overall analysis supports the hypothesis of a different origin for TSP during the year and for different wind regimes and therefore possible size and chemical differences in TSP, which should be further investigated due to their health implications.     

Flow Field and Pollution Dispersion in a Central London Street

Urban pollution due to roadways is perceived as a major obstacle to implementing low-energy ventilation design strategies in urban non-domestic buildings. As part of a project to evaluate the use of a computational fluid flow model as an environmental design tool for urban buildings, this paper seeks to address the impact of pollution from roadways on buildings in areas of restricted topography and assess dominant influencing factors and other requirements for testing the flow model predictions. Vertical profiles of carbon monoxide (CO) and temperature at the facade of a building in a Central London street, in addition to above-roof wind speed and direction, were measured over a period of three months. The street has a height-to-width (h/W) ratio of 0.6 and is of asymmetric horizontal alignment. The air flows in the area surrounding the building were modelled using a computational fluid flow model for two orthogonal wind directions. CO concentrations were calculated from the steady-state flow field in order to place point measurements in the context of the flow field, identify persistent features in the measured data attributable to the flow structure and, by comparison with measurements, identify further testing requirements.Some qualitative and quantitative agreement between measured and modelled data was obtained. Measured CO levels at the building facade and vertical variations of CO were small, as predicted by the model. A wake-interference type flow was predicted by the model for wind speeds >2ms-1 with formation of a vortex cell occurring for roof-level wind speeds >5ms-1 for the cross-wind direction, which was reflected in the measured CO levels and facade gradients. A direction-dependent inverse relationship was noted, both in the model and measurements, between above-roof wind speed and facade CO levels although statistical correlations in the time series were poor. CO concentrations at the facade were found to increase with height frequently, as well as decrease, especially for parallel winds. It is expected that mechanical turbulence due to vehicles was largely responsible. In comparison, thermal stratification appeared to play only a minor role in controlling vertical mixing in the street, under low wind speed conditions.     

Measurement of the proximity effect for indoor air pollutant sources in two homes

Personal exposure to air pollutants can be substantially higher in close proximity to an active source due to non-instantaneous mixing of emissions. The research presented in this paper quantifies this proximity effect for a non-buoyant source in 2 naturally ventilated homes in Northern California (CA), assessing its spatial and temporal variation and the influence of factors such as ventilation rate on its magnitude. To quantify how proximity to residential sources of indoor air pollutants affects human exposure, we performed 16 separate monitoring experiments in the living rooms of two detached single-family homes. CO (as a tracer gas) was released from a point source in the center of the room at a controlled emission rate for 5-12 h per experiment, while an array of 30-37 real-time monitors simultaneously measured CO concentrations with 15 s time resolution at radial distances ranging from 0.25-5 m under a range of ventilation conditions. Concentrations measured in close proximity (within 1 m) to the source were highly variable, with 5 min averages that typically varied by >100-fold. This variability was due to short-duration (<1 min) pollutant concentration peaks ("microplumes") that were frequently recorded in close proximity to the source. We decomposed the random microplume component from the total concentrations by subtracting predicted concentrations that assumed uniform, instantaneous mixing within the room and found that these microplumes can be modeled using a 3-parameter lognormal distribution. Average concentrations measured within 0.25 m of the source were 6-20 times as high as the predicted well-mixed concentrations.     

基于激光雷达分析2020年冬季镇江地区一次大气污染过程

利用气溶胶激光雷达观测结果,结合环境监测站污染物浓度数据、气象观测资料及HYSPLIT后向轨迹模式结果,综合分析2020年1月17—22日镇江市一次大气污染过程。结果显示,此次污染过程前期天气形势稳定,不利于污染物的清除及扩散,后期受偏北风影响,北方污染物向镇江输送,使得本地污染物持续累积,污染不断加重。特征雷达图分析表明此次污染为以PM2.5为主的二次污染。激光雷达显示污染日消光系数为0.0⁰.9 km-1,消光系数垂直廓线日变化特征明显,气溶胶粒子主要堆积在0.6 km高度以下,并且很好地揭示了污染气团从高空逐渐下沉最终与本地污染叠加的过程,与HYSPLIT模式解析的污染气团来源结果基本一致。     

基于MODIS数据产品的桂林市气溶胶时空分布及变化特征分析

利用MODIS 3 km AOD原始数据,借助ENVI、Arc GIS等软件对桂林市AOD进行提取和插值,模拟该市AOD的空间分布特征,综合分析区域地形、NDVI与AOD分布的相关关系。结果表明:桂林市AOD空间分布受到地形的影响,AOD高值区出现在近乎封闭的桂林中部盆地和其他区域的谷地,地势高的区域AOD值较低;利用NCEP分析资料的风场数据,对比春节期间桂林市的AOD相对高值中心的变化,得出气溶胶的迁移和扩散方向与风向一致,静风时AOD相对高值中心更容易集中在中部盆地的城区。     

川南6市空气中SO2和NO2空间分布特征

利用简单、方便、不用电源的被动采样技术分别对川南地区6市区域范围内空气中SO2和NO2在雨季和旱季的空间分布特征进行研究。按16 km×16 km的均匀网格布设点位162个,并在雨季于6市各选1个空气自动站布设城区点位采集空气中SO2和NO2。获得的样品经0.3%的双氧水浸提后采用离子色谱法进行分析,经换算后获得空气中SO2和NO2的浓度,了解了其含量水平,绘制了SO2和NO2的空间分布图,掌握了其空间分布特征,并对可能的来源进行了浅析。将被动采样监测结果与自动站监测结果进行相关分析,两者高度线性相关,NO2和SO2线性相关系数分别为0.901 3和0.874 5,均大于r0.05(4)=0.811 4。     

长株潭区域一次重度污染过程气象成因

利用PM_2.5质量浓度、地面气象要素、NCEP、ERSST＿V3、GBL等资料,研究了2021年12月7—11日长株潭地区一次重度空气污染过程的特征及成因。结果表明,高空平直环流、无明显槽脊影响,地面弱冷空气活跃是本次重度空气污染过程的主要环流形势特征;地面均压场、小风和升温增湿是此次重度空气污染过程的主要气象要素特征。污染物浓度变化与主导风向和污染通道密切相关,本地风速对混合层的高度、污染物水平扩散影响较大,600～700 hPa逆温层有利于污染物在主导风作用下近距离传输及在低层交换积累。我国中东部污染物积聚是长株潭区域重要的污染来源,长株潭地区存在区域性同步污染现象。低层流入长株潭区域气流轨迹差异及地理条件是长株潭污染物空间分布差异的重要因素。     

连云港市大气降尘时空分布特征

采用2018年1月—2020年2月连云港市17个监测点位降尘数据,分析连云港市大气降尘变化规律和时空分布特征.结果表明,2018年连云港市平均降尘量为11.6 t/(km2·30 d),超过江苏省考核标准[6 t/(km2·30 d)],超标倍数为0.93,其呈现出先增大再降低再增大的规律,春季、秋季降尘量最大,与大风...     

Ground level volume mixing ratio of methane in a tropical coastal city

Urban regions are hotspots of greenhouse gas emissions which include CO₂, CH₄, N₂O, etc. Methane is a strong greenhouse gas which is produced from a number of sources including fossil fuel combustion, municipal waste, and sewage processing, etc. Ground level mixing ratio of methane in the tropical coastal city of Thiruvananthapuram in South India, during calm early morning period was measured. Measurements were done during both winter and summer seasons. Concentrations were significantly higher than global average value. Intra-city variation in ground level mixing ratio was also significant. Ground level methane concentration at Thiruvananthapuram urban area showed maximum value of 3.16 ppmV. Under stable atmospheric conditions in early morning, ground level mixing ratio of methane was 2.79 ppmV in winter and 2.54 ppmV during summer. The spatial distribution of methane concentration shows correlation with urban heat island.     

基于EOF/SVD的2018年湖北省臭氧特征及其高值与气象要素关系研究

基于湖北省2018年4-10月臭氧、温度和相对湿度逐小时监测数据以及50 m风场逐小时再分析数据,采用经验正交函数(EOF)和奇异值分解(SVD)方法,分析了2018年湖北省臭氧特征及其高值与气象要素关系。结果表明:湖北省臭氧日最大8 h浓度距平呈现以武汉为正值中心、自鄂东向鄂西递减的主要空间分布型;15:00臭氧与温度呈现较好的正相关关系,以随州、襄阳及其周边最为明显;与14:00相对湿度呈现很好的负相关关系,以孝感、随州、荆门及其周边最为明显;襄阳西部和十堰北部地区15:00 50 m风场的纬向分量对本地臭氧高值有一定影响,武汉北部、黄冈北部以及孝感东部等地15:00 50 m风场的经向分量对本地臭氧高值影响较大。