Some aspects of air pollution in Buenos Aires city

This paper presents three aspects of air pollution in the city of Buenos Aires (Argentina). First, we describe the main features of air pollution climatology in the city: the characteristics of wind flow, atmospheric stability and mixing heights. Then, we present the results of the application of DAUMOD and ISCST3 atmospheric dispersion models to calculate spatial and temporal distributions of carbon monoxide and nitrogen oxides background concentrations. Finally, we present the main features of carbon monoxide concentrations observed in a narrow street canyon located downtown.     

Continuous measurement of gaseous pollutants in Buenos Aires city

Data on CO, NO, NO₂ and O₃ concentrations measured in Buenos Aires city using a continuous monitoring station are reported. This is the first systematic study of this kind carried out in the city, which is, together with its surroundings, the third more populated in Latin America. Measurements were performed during 12 months in one of the principal avenues near downtown. Results indicate that vehicular traffic is the principal source of CO and NO_x. The concentration of O₃ is generally quite low and results from the mixing of clean air masses with exhaust gases containing high amounts of NO. The monthly averages of CO and NO decrease from Winter to Summer in correlation with the increase of the mean wind speed and average temperature. These results are compared with previous measurements on the spatial distribution of NO₂ in the whole city using passive diffusion tubes and with the concentration of CO, which is being continuously registered since several years in the downtown area. Measurements performed at a green, windy, low traffic area beneath the La Plata river are also shown.     

Daytime ventilation conditions in Buenos Aires city, Argentina

From routinely available observational data, the daytime ventilation conditions in Buenos Aires city have been studied. The climatological behaviour was analysed. The study included the effects of local conditions, such as the coastal location, the urban features and the influence of air humidity on the characteristic parameters of the dispersive capability of the atmosphere. The frequencies of occurrence of daytime ventilation factors and related stability conditions were obtained. There is a relatively high probability for reduced daytime ventilation in winter. The most frequent daytime stability conditions in all ventilation factor ranges and seasons are the near-neutral and the slightly unstable atmospheric conditions. The frequencies of occurrence of reduced ventilation conditions are higher if humidity is not included, except during winter, when differences are nearly absent. Humidity inclusion produces an increase of the mean ventilation factors, especially in the warm season. Statistical tests have been applied to analyse the departures for significance. In some situations, the influence of humidity is large enough to obtain a statistically significant response     

A case study of biomass burning and its smoke dispersion to Buenos Aires City, Argentina

In February and March 2000, several uncontrolled forest and grassland fires occurred in the municipalities of Campana and Zarate (100 km north of Buenos Aires, Argentina). The biomass burning emitted a large amount of smoke particulates, which caused dense fog and visibility impairment in the nearby area. From 18 to 19 March, the smoke was transported towards the Buenos Aires Metropolitan Area (BAMA), resulting in a prolonged reduction of visibility. This feature was supported by a build-up of the Aerosol Optical Thickness (AOT) and deposited particulate matter mass observed in BAMA. This paper examines the prevailing meteorological situation that produced the smoke transport towards BAMA. An anticyclone, displaced easterly over the interest area by a frontal low-pressure system, produced low-level ventilation conditions that favoured the transport and the smoke persistence in BAMA. The transport of particles and the behaviour of their normalised concentrations were simulated adequately by a regional dispersion model.     

Concentrations and elemental composition of particulate matter in the Buenos Aires underground system

Total suspended particulate (TSP) samples have been collected at six stations in the C and B lines of the Buenos Aires underground system and, almost simultaneously, at six ground level sites outside and nearby the corresponding underground stations, in the Oct 2005/Oct 2006 period. All these samples were analyzed for mass and elemental Fe, Cu, and Zn concentrations by using the Particle Induced X-ray Emission (PIXE) technique. Mostly, TSP concentrations were found to be between 152 μg m⁻³ (25% percentile) and 270 μg m⁻³ (75% percentile) in the platform of the stations, while those in outside ambient air oscillated from 55 μg m⁻³ (25% percentile) to 137 μg m⁻³ (75% percentile). Moreover, experimental results indicate that TSP levels are comparable to those measured for other underground systems worldwide. Statistical results demonstrate that subway TSP levels are about 3 times larger on average than those for urban ambient air. The TSP levels inside stations and outdoors are poorly correlated, indicating that TSP levels in the metro system are mainly influenced by internal sources.Regarding metal concentrations, the most enriched element in TSP samples was Fe, the levels of which ranged from 36 (25% percentile) to 86 μg m⁻³ (75% percentile) in Line C stations, while in Line B ones they varied between 8 μg m⁻³ (25% percentile) and 46 μg m⁻³ (75% percentile). As a comparison, Fe concentrations in ambient air oscillated between 0.7 μg m⁻³ (25% percentile) and 1.2 μg m⁻³ (75% percentile). Other enriched elements include Cu and Zn. With regard to their sources, Fe and Cu have been related to processes taking place inside the subway system, while Zn has been associated with outdoor vehicular traffic. Additionally, concerns about possible health implications based on comparisons to various indoor air quality limits and available toxicological information are discussed.     

Analysis of NO,NO2, O3 and NOx concentrations measured at a green area of Buenos Aires City during wintertime

We analyse the air quality data measured at a green area of Buenos Aires City (Argentina) during 38 days in winter. We study the relationships between ambient concentrations of nitric oxide (NO), nitrogen dioxide (NO₂), ozone (O₃) and nitrogen oxides (NO_x=NO+NO₂). The variation of the level of oxidant (OX=O₃+NO₂) with the NO_x is obtained. It can be seen that the level of OX at a given location is made up of two contributions: one independent and another dependent on the NO_x concentration. The first one can be considered as a regional contribution, equivalent to the background O₃ concentration and the second one as a local contribution that depends on the level of primary pollution. Local oxidant sources may include direct NO₂ emissions, the reaction of NO with O₂ at high-NO_x levels, and the emission of species that promote the conversion of NO to NO₂. The final category of emissions may include the nitrous acid (HONO) that is emitted directly in vehicle exhaust. Finally, we present a diurnal variation of the local as well as regional contributions and the dependence of the last one on wind direction.     

Prediction of sulfur dioxide concentrations at a site near downtown Santiago,Chile

We have analyzed the possibility to predict hourly averages of sulfur dioxide concentrations in the atmosphere at a site not far from the downtown area in the city of Santiago, Chile. We have compared the forecasts produced assuming persistence, linear regressions and feed forward neural networks. The effect of meteorological conditions is included by using forecasted values of temperature, relative humidity and wind speed at the time of the intended prediction as inputs to the different models. The best predictions for hourly averages are obtained with a three-layer neural network that has hourly averages of sulfur dioxide concentrations every 6 h on the previous day plus the actual values of the meteorological variables as input. Training the network with 1995 data, error in 8 h in advance prediction for 1996 data is of the order of 30%.     

Ecotoxicological studies of environmental samples from Buenos Aires area using a standardized amphibian embryo toxicity test (AMPHITOX).

The toxicity of 34 environmental samples from potentially polluted and reference stations were evaluated by means of the AMPHITOX test from acute to chronic exposure according to the toxicity found in each sample. The samples were obtained from surface and ground water, leaches, industrial effluents and soils. The data, expressed in acute, short-term chronic and chronic Toxicity Units (TUa, TUstc and TUc) resulted in a maximal value of 1000 TUc, found in a leach, while the lower toxicity value was 1.4 TUa corresponding to two surface water samples. In five samples (four providing from reference places) no toxicity was detected. The results point out the possibility of evaluating the toxicity of a wide diversity of samples by means of AMPHITOX as a customized toxicity test. The fact that almost all samples with suspected toxicity in rivers and streams from the Metropolitan area of Buenos Aires city resulted toxic, indicates the need of enhanced stewardship of chemical substances for environmental and human health protection purposes.     

Aquatic macrophytes potential for the simultaneous removal of heavy metals (Buenos Aires, Argentina)

Heavy metal removal from water has been approached by using different technologies. Phytotechnologies, with an increasing development during the last two decades, involve using plants for metal removal. Three autochthonous floating macrophytes, common in pampean shallow lakes (Argentina), Pista stratiotes, Spirodela intermedia and Lemna minor were used in laboratory experiences for the simultaneously removal of several heavy metals (Fe, Cu, Zn, Mn, Cr and Pb) resulting from anthropogenic activity, in order to simulate a naturally polluted environment. The experiences were performed for different concentrations of metals along 15 days. High metal removal percentages were obtained for the 3 species and metals. L. minor did not survive the conditions of the experiment. High correlation between the final water and the macrophytes metal concentration was obtained, deviations were due to PbCrO(4) precipitation. The rate of metal uptake was dependent on the metal concentration for the 3 species studied.     

Atmospheric deposition of nitrogen emitted in the Metropolitan Area of Buenos Aires to coastal waters of de la Plata River

The Metropolitan Area of Buenos Aires (MABA) is the third mega-city in Latin America. Atmospheric N emitted in the area deposits to coastal waters of de la Plata River. This study describes the parameterizations included in DAUMOD-RD (v.3) model to evaluate concentrations of nitrogen compounds (nitrogen dioxide, gaseous nitric acid and nitrate aerosol) and their total (dry and wet) deposition to a water surface. This model is applied to area sources and CALPUFF model to point sources of NO_x in the MABA. The models are run for 3 years of hourly meteorological data, with a spatial resolution of 1 km². Mean annual deposition is 69, 728 kg-N year^?1 over 2 339 km² of river. Dry deposition contributions of N-NO₂, N-HNO₃ and N-NO₃^? to this value are 44%, 22% and 20%, respectively. Wet deposition of N-HNO₃ and N-NO₃^? represents 3% and 11% of total annual value, respectively. This very low contribution results from the rare occurrence of rainy hours with wind blowing from the city to the river. Monthly dry deposition flux estimated for coastal waters of MABA varies between 7 and 13 kg-N km^?2 month^?1. These results are comparable to values reported for other coastal zones in the world.     

湖州市中心城区饮用水源地粪大肠菌群污染特征及源解析研究

根据湖州市中心城区2家市级饮用水源地2005-2009年粪大肠菌群指标监测数据,分析湖州市中心城区饮用水源地粪大肠菌群污染特征,对饮用水源地周边污染源进行排查.结果表明,2家市级饮用水源地粪大肠菌群污染严重,城市污水处理厂出水、市政管网排水系统的雨污合流排放是粪大肠菌群的主要来源.     

Estimation of dry deposition of atmospheric nitrogen to coastal waters of de la Plata River in front of Buenos Aires city

The deposition of atmospheric nitrogen (N) to surface waters of de la Plata River downwind of Buenos Aires city has been estimated using atmospheric dispersion-deposition models. The CALPUFF model has been applied to point source emissions and the DAUMOD-RD model has been developed to evaluate the area source emission contributions. Annual N dry deposition is 31,763 kg-N yr⁻¹ (≈ 18 kg-N km⁻² yr⁻¹). Nitrogen dioxide contribution to this value is 54% and nitric acid contribution is 46%. The maximum monthly N dry deposition fluxes vary between 7 kg-N km⁻² month⁻¹ (in February) and 13 kg-N km⁻² month⁻¹ (in December).     

Analysis of the air pollution climate at a central urban background site

Measurements of air pollutants from a background site in central London are analysed. These comprise hourly data for CO, NO, NO₂, O₃, SO₂ and PM₁₀ from 1996 to 2008 and particle number count from 2001 to 2008. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and autocorrelation and cross-correlation functions. CO, NO and NO₂ show a typical traffic-associated pattern with two daily peaks and lesser concentrations at the weekend. Particle number count and PM₁₀ show a similar cycle, but with smaller amplitude. Ozone has an annual cycle with a maximum in May, influenced by the spring maximum in background ozone, but the diurnal and weekly cycles are dominated by losses through reaction with nitric oxide. Particle number count shows a minimum corresponding with maximum air temperatures in August, whereas the CO, NO NO₂ and SO₂ show a minimum in June/July. There is a lower particle count to NO_x ratio at the background site compared to a central London kerbside site (Marylebone Road) and a seasonal pattern in particle count to NO_x and PM₁₀ ratios consistent with loss of nanoparticles by evaporation during atmospheric transport. Sulphur dioxide peaks in the morning in summer, but at midday in winter consistent with emissions from elevated sources mixing down from aloft as the diurnal mixed layer deepens. Implications for epidemiological studies of air quality and health are discussed. Sulphur dioxide, carbon monoxide, nitric oxide and nitrogen dioxide show clear downward trends over the measurement period, PM₁₀ declines initially before levels stabilised, and ozone concentrations increased.     

Observational study of ozone pollution at a rural site in the Yangtze Delta of China

Ozone and related trace gases (CO, NO_x, and SO₂) were measured from June 1999 to July 2000 at a rural site in the Yangtze Delta of China, a region of intensive anthropogenic activity. Elevated ozone levels were frequently observed during the study period, with the highest frequency in late spring and early summer. Over a 1 yr period, 21 d were found to have ozone concentrations exceeding the new US 8-h 80 ppb health standard. Calculation of the “SUM06” exposure index also shows relatively high (>15 ppm h) values for each season except winter. At these levels ozone may have adverse effects on human health as well as agricultural crops. Analysis of meteorological data shows that the high ozone days were associated with large-scale stagnation, intense solar radiation, and minimum rainfall. Large-scale back trajectories indicate a slow-moving/re-circulating airmass during the episodic days. Examination of chemical data shows that the observed daytime high ozone concentrations were due to downward mixing of ozone-rich air, in situ photochemical formation, and in some cases, advection to the site of aged plumes. The very high CO levels (and high CO to NO_x ratios) were found to coincide with many of the ozone episodes, suggesting a contribution from sources of emission involving incomplete combustion. It is suggested that the burning of biomass (e.g., biofeuls and crop residues) may be an important source for the observed high CO and O₃ values.     

The influence of a time shift on the pollution maxima over an urban site

Several European countries have chosen to go on “summer time” from April to October, corresponding to a shift of 2-h from universal time (UT + 2), instead of 1-h for winter time (UT + 1). Because of this shift, pollutant emissions are released into the atmosphere under different conditions of stability, especially in the morning and evening.Using a box model applied to the experimental results obtained in an urban center, the effect of the time shift on the Aitken nuclei concentration in the air is calculated. The use of UT + 2 can give rise to an increase of about 30 % in the morning, and a decrease of nearly 50 % in the evening.     

A mathematical modeling of sulphur dioxide pollution in Erzurum City

A non-linear simple air-quality model was developed by applying the continuity equation for the air control volume over Erzurum city center and tested using daily average values of SO2 and meteorological data obtained during the winter seasons in Erzurum, Turkey from 1994 to 1998. Model parameters are estimated by non-linear regression analysis. Agreement between model predictions and measured data was found very satisfactory with standard deviations less than 20 microg/m3.     

福州市城市化进程与大气污染关系研究

以福州市为研究区域,选取福州市1996—2012年的时间序列数据,将大气污染物浓度作为被解释变量,城市化水平作为解释变量,分别设定二次曲线模型和三次曲线模型,通过比较PM10、SO2、NO2浓度与城市化水平的二次曲线和三次曲线模型的回归拟合效果,得出福州市大气污染与城市化水平之间的演化规律。结果表明,1996—2012年,福州市城市化水平平稳上升,城市的大气污染程度与城市化水平之间的关系并不完全符合"倒U型"的环境库兹涅茨曲线,不同的污染物类型具有不同的演化规律。PM10、SO2与城市化水平呈"倒N型"的曲线关系;NO2与城市化水平之间呈现"倒U型"曲线关系。由于研究的时间序列较短,因而研究结果可能只是真实曲线的一部分,福州市的大气污染与城市化水平之间的关系还有待进一步研究。     

突发性场地污染应急控制技术研究进展

随着中国社会经济水平的加速发展,近年来各类突发性场地污染事故频发,如何有效地在第一时间对污染物进行应急控制及场地修复显得尤为重要.以突发性场地污染为研究对象,探讨了土壤及地下水中污染物的应急控制及场地修复技术的研究状况,给出了各项应急控制技术在突发性场地污染事故中适用的目标污染物及土壤类型,以便在实际运用中根据场地的污染类型和土壤性质快速做出响应.最后还指出,应急控制技术作为一种暂时性处理手段,可在场地污染事故发生后对污染物扩散进行快速控制,但不可作为一种长期处置措施.