Trends in air quality and population exposure in Santiago, Chile, 1989–2001

This study focused on establishing trends in the period 1988–2001 in PM_2.5, PM₁₀ and ozone concentrations in Santiago, Chile, and linking those to population exposure. There is strong seasonality in the concentration levels, driven by prevailing meteorological conditions, with the concentration of particulates peaking at the beginning of winter, whereas the ozone concentration is highest during the summer. The levels of PM_2.5 and PM₁₀ have substantially decreased since the late 1980s and so has the population exposure. Nevertheless, the majority of the population is still exposed to annual average levels that are above standard values. The situation with ozone exposure is different; no substantial decrease can be observed in the data. If anything, certain parts of Santiago, notably the south-east, have shown increased levels of ozone. Overall population exposure indicates that the average person was more at risk of ozone in the year 2000 than they were in 1993.     

Influence of meteorological factors on air pollution concentration for a coastal region in India

A long-term study of measurement of concentration of NO_x, SO₂ and TSP pollutants have been done in a port and harbour region in India. Monthly measurements of gaseous and particulate pollutants were made at six monitoring stations from January 1997 to December 2000. Meteorological data was also simultaneously collected. In this study, the relationship between monitored ambient air quality data and meteorological factors, such as wind speed, temperature, is statistically analysed, using the SPSS package. The monthly mean concentrations of NO_x, SO₂ and TSP were in the range of 19.5–59.0 μg/m3, 8.6–51.3 μg/m3 and 88.2–199.3 μg/m3, respectively. The results show that TSP is strongly correlated with NO_x and SO₂ with a correlation coefficient of 0.83 and 0.82, respectively. The correlation coefficients for TSP, NO_x, and SO₂ with wind are –0.78, –0.78, and –0.88, respectively.     

A statistical model for predicting carbon monoxide levels

This paper presents a statistical model that is able to predict carbon monoxide (CO) concentrations as a function of meteorological conditions and various air quality parameters. The experimental work was conducted in an urban atmosphere, where the emissions from cars are prevalent. A mobile air pollution monitoring laboratory was used to collect data, which were divided into two groups: a development group and a testing group. Only the development dataset was used for developing the model. The model was determined by using a stepwise multiple regression modelling procedure. Thirteen independent variables were selected as inputs: non-methane hydrocarbon (NMHC), methane (CH₄), suspended dust, carbon dioxide (CO₂), nitrogen oxide (NO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), wind speed, wind direction, temperature, relative humidity and solar energy. It was found that NO has the most effect on the predicted CO concentration. The contribution of NO to the CO concentration variations was 91.3%. Adding in the terms for NO₂), NMHC and CH₄ improved the model by only a further 2.3%. The derived model was shown to be statistically significant, and model predictions and experimental observations were shown to be consistent.     

Air pollution at the Bily Kriz mountains in the Czech Republic

An evaluation of air pollution at the Bily Kriz mountains in the Czech Republic is given. Annual daily concentrations of sulphur dioxide (SO₂), nitrogen oxides (NO_x), particulate matter of size 10 mm (PM₁₀) and ozone (O₃) measured in the years 1994–2000 are presented. Air pollution at Bily Kriz is assessed with the reference to the European Union Directives and the standards adopted by the Czech Republic. In general, the concentrations of air pollutants were lower in 1996 for ozone and decreased for SO₂, NO_x and PM₁₀ from 1994. The daily values of SO₂ and PM₁₀ exceeded the European Union limits in approximately 0.0% and 5.5% of cases, respectively. The values of ozone exceeded the limits for the considered period.     

Measurement of atmospheric particles and anionic species across central Taiwan

The ambient air concentrations and fluxes of various anionic species were sampled by MOUDI, TSP and dry deposition plates at a traffic sampling site in Taichung, central Taiwan. In the sampling period, from September to December 2000, the ambient air particle concentrations (PM₁, PM_2.5, PM₁₀ and TSP) were lower in the September than in the other three months (October to December). The reason is that the northwest wind brought more particles (diameter less than 10 μm) and the higher wind speed caused higher dry deposition fluxes and TSP concentrations in the last three months. The anion species percentages of TSP were 0.24%, 13.7%, 0.52%, 12.0%, 18.9'% and 54.6% for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively. The results revealed that SO₄^2-, NO₃^-, Cl^- and NO₂^- were the dominant species at the traffic sampling site. The ion-size distributions of Cl^-, NO₂^- and NO₃^- were unimodal, the main peak being between 3.2 and 5.6 μm. In contrast, the size distribution of SO₄^2- was bimodal, with the main peaks in the particle size ranges 0.32.0.56 μm and 3.2.5.6 μm. The ambient average particle dry deposition flux was 6.28 μg/m2/s, and the dry deposition fluxes were 0.01, 94.6, 0.05, 34.7, 72.2 and 376.4 ng/m2/s for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively. The dry deposition velocities were 3.10, 0.03, 3.67, 0.05, 1.54, 2.03 and 3.67 cm/s for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively.     

Sampling errors in the study of acid gases and anion species in atmospheric aerosols

Atmospheric acid aerosols were sampled by two annular denuder systems (ADS) and a micro-orifice uniform deposit impactor (MOUDI) at a traffic site in central Taiwan. Theoretical analysis showed that the relative artifact for HNO₃ gas sampling was about 0.53 when the initial HNO₃ concentration was under 0.2 µg/m³ and should be considered carefully. The concentrations of gaseous acid at the traffic sampling site were higher than those in the other study. The size distributions of acid aerosols were unimodal for Cl^-, NO₂^-, and NO₃^-, and bimodal for SO₄^2-. The dominant acid ions in particles less than 18 µm were SO₄^2-, NO₃^-, NO₂^- and Cl^-.     

Annual simulation of secondary pollution over northern Italy

A secondary pollution modelling system for simulating airborne dispersion and chemical reactions is applied over a regional scale domain located in the North-West of Italy, where urban and industrial areas are present. It was found an overestimation of NO₂ in the urban areas, probably due to an underestimation of the vertical diffusivity; the analysis of O_X confirms that the discrepancies in O₃ and NO₂ are mainly due to local scale effects; the model shows a general underestimation of the observed PM10 concentrations due to the uncertainties in the emission inventories, spatial resolution, and the adopted aerosol modelling approach.     

Treatment of reactive dyes and textile finishing wastewater using Fenton's oxidation for reuse

Fenton's oxidation (FO) was used to decolourise and degrade some reactive dyes (Remazol Black 5, Remazol Red, Remazol Blue, Remazol Yellow) and raw textile finishing industry effluents (S1, S2, S3) containing mainly reactive dyes. The operational conditions for pH varied between 2.5 and 4.0 while temperature ranged from 30°C to 50°C. The concentrations of FeSO₄ and H₂O₂ varied to a wide range (200–600 mg/l of FeSO₄, 300–1000 mg/l of H₂O₂) depending on the type of the dyes and their mixture and textile additives used in the process. FO is highly effective for colour removal (>99%) for reactive dyes and (87–94%) for textile finishing wastewater. It can be applied as a pretreatment and the remaining total dissolved solids (TDS) can be removed by an additional advanced process, e.g. membrane process.     

Monitoring of phytoplankton biomass and nutrients in a polluted stream

The spatial and temporal variations in the concentrations of nutrients (NH₄⁺, NO₂⁻, PO₄³⁻, SiO₄⁻) and chlorophyll a were monitored simultaneously in a slow-flowing watercourse (Saricay Stream, Turkey), which runs in a rural–urban gradient. Chlorophyll a concentrations ranged between 0.044 μg l^-1 and 206.15 μg l^-1 and, in general, the higher concentrations of chlorophyll a and ammonium were measured downstream of the raw sewage outfalls. Nitrate was by far the most abundant form of inorganic nitrogen, and its concentration ranged between 411.71 μM and 87.25 μM. Silicates and phosphates were always potentially limiting to biomass relative to nitrogen. Agricultural run-off and point discharges from urban sources greatly affected the chemical composition of the water in the Saricay Stream and drove the system towards eutrophication.     

Short-term prediction of means of artificial neural urban NO2 pollution by networks

A neural network model for the short-term prediction of concentrations of urban pollutants was developed and applied to the Turin (Northern Italy) air quality network. In particular, the study was focused on NO₂ concentrations measured at five stations; t + 3 and t + 24 hour NO₂ concentration forecasting based on hourly meteorological and concentration data gave good agreement with observed concentrations. This is particularly true for the mean concentration values and concentration distribution. The time of occurrence of peak values was correctly forecast but the amounts were generally underestimated. To reduce this underestimation, an empirical step function was applied in the t + 24 case. This allowed an accurate estimate to be obtained of the few cases in which 50% of the air quality monitoring stations exceeded the attention level (200 μg m^-3) during the following day for at least one hour.     

Analysis and interpretation of the monitoring data for C2–C11 hydrocarbons in the atmosphere of a rural Portuguese site

This paper focuses the application of a measurement technique for determining atmospheric C₂–C₆ hydrocarbons after canister sampling and analysis by gas chromatography/flame ionisation detection (GC/FID), as well of an adsorption-sampling technique for C₆–C₁₁ compounds and GC/FID analysis after thermal desorption and cryogenic concentration. Tens of samples collected at Giesta, a rural area located 20 km to the SE of the coastal Portuguese city of Aveiro, were analysed. The characterisation of C₂ C₁₁ hydrocarbons is presented, considering seasonal variations, diurnal cycles, the influence of air masses and different photochemical conditions. Ratios between hydrocarbons and principal components analysis were applied to differentiate between biogenic and anthropogenic sources.     

Spatial and diurnal variations in concentration of atmospheric NOx along urban-rural roadways in Nanjing, Southeastern China

Atmospheric NO_x concentrations (including NO₂ and NO) on the roadside environments of urban trunk, belt highway and suburban road as well as a reference in a forest area were measured. NO_x concentrations on roadside environments tended to be higher than that on the reference. With the exception of suburban road, NO_x concentrations over both of the urban trunk and belt highway exceeded the limited value of National Air Environmental Quality Standards. Gradient measurement of NO_x on the downwind side of the belt highway shows that it declined to background level over 100 m from the road edge.     

Separate determination of PM10 emission factors of road traffic for tailpipe emissions and emissions from abrasion and resuspension processes

Little is known about the relevance of mechanically produced particles of road traffic from abrasion and resuspension processes in relation to the exhaust pipe particles. In this paper, emission factors of PM₁₀ and PM₁ for light and heavy-duty vehicles were derived for different representative traffic regimes from concentration differences of particles and nitrogen oxides (NO_x) in ambient air upwind and downwind of busy roads, or alternatively of kerbsides and nearby background sites. Hereby, PM₁ was interpreted as direct exhaust emissions and PM₁₀-PM₁ as mechanically produced emissions from abrasion and resuspension processes. The results show that abrasion and resuspension processes represent a significant part of the total primary PM₁₀ emissions of road traffic. At sites with relatively undisturbed traffic flow they are in the same range as the exhaust pipe emissions. At sites with disturbed traffic flow due to traffic lights, emissions from abrasion/resuspension are even higher than those from the exhaust pipes.     

Modelling changes of aerosol compositions over Belgium and Europe

Seasonal changes in aerosol compositions over Belgium and Europe are simulated with an extended version of the EUROS model. EUROS is capable of modelling mass and chemical composition of aerosols in two size fractions (PM_2.5 and PM_10-2.5). The chemical composition is expressed in terms of seven components: ammonium, nitrate, sulphate, primary inorganic compounds, elementary carbon, primary organic compounds and Secondary Organic Compounds (SOA). A comparison of modelled and measured aerosol concentrations showed that modelled concentrations are generally consistent with observed concentrations. The chemical composition of the aerosol showed a strong dependence on the season. High aerosol concentrations during the summer were mainly due to high concentrations of the secondary components nitrate, ammonium, sulphate and SOA in the size fraction PM_2.5. In contrast, during autumn and winter, increased PM-concentrations were mainly due to higher concentrations of primary components, especially in the size fraction PM_10-2.5.     

Roadside particulate levels at 30 locations in the Kathmandu Valley, Nepal

Roadside particulate levels (PM₁₀) at 30 locations throughout the Kathmandu Valley, Nepal are reported. There were seven sampling cycles from January to December 1999. PM₁₀ levels ranged between 1000 and 6000 μ/m3 for 1-h sampling. There was no consistent trend in PM10 levels with respect to monitoring cycle, average precipitation or wind speed. There is no WHO guideline for PM₁₀ (no safe exposure threshold), but the EPA 24-h standard is 150 μ/m3. The major sources of roadside PM₁₀ include dust re-suspension from vehicular movement and human activity, and particulate emissions from old vehicles. Other sources of PM₁₀ in the valley include cement and brick factories. Studies are currently being conducted to determine the lead content of PM₁₀ from roadside samples. Additional studies are warranted to assess the potential adverse human health effects of acute or chronic exposure to high particulate levels reported in this study.     

Characteristic study of particulates and metallic elements at an urban sampling site in Taichung, central Taiwan

Atmospheric total suspended particulate concentrations and metallic element concentrations were measured at three locations, characteristic of urban, suburban and rural sites. The sampling period was from July 2000 to August 2000. The results indicated that the urban sampling site had the highest total suspended particulate concentrations (average 108.61μ1m3), followed by the suburban site (average 60.11μ1m3) and the rural site (average 53.31μ1m3). The average PM_2.5 concentrations (24.11μ1m3) were higher than the PM_2.5-10 concentrations (12.81μ1m3) at the urban site. The average distributed ratios for PM_2.5/PM_2.5-10 were about 1.29, 1.53, 0.12, 1.12 and 2.31 for Pb, Zn, Fe, Ni and Cr, respectively. The average total suspended particulate mass ratios for daytime and nighttime were about 1.72. As for the elements Cu, Pb, Zn, Fe, Ni and Cr, these ratios were about 0.63, 0.97, 0.54, 1.66, 0.53 and 1.12, respectively. The total suspended particulate daytime concentrations of Pb and Zn were positively correlated (R = 0.925) at the urban sampling site. The elements Ni and Cr were positively correlated both during the daytime (R = 0.648) and the nighttime (R = 0.511), revealing that they came from the same emission source during daytime and nighttime, at the urban sampling site.     

Air pollution and the influence of sources on Paulinia (Brazil) and surroundings

The air quality in the industrial area and surroundings of the city of Paulinia (state of Sao Paulo, Brazil) has been investigated by analysing the concentration of air pollutants (SO₂, PM₁₀, NO, NO₂, CO and ozone) and identifying the main sources of air pollution. A mobile pollutant monitoring unit was used to collect the data at five different sites from November 2000 to July 2002. Critical pollutants were determined based on air quality standards, and sources were identified by principal component analysis. Photochemical reactions play an important role in Paulinia's air pollution: three out of five monitored sites showed levels exceeding the standard air quality of ozone. SO₂ and PM₁₀ appeared as pollutants deserving special attention. All the monitored sites showed vehicles and industrial plants (which release SO₂) to be significant sources of pollution. Depending on the location, ozone was related mainly with vehicular or industrial sources.     

Effect of leachate recirculation on refuse decomposition rates at landfill site: a case study

In this study, a comparison of methane (CH₄) generation rates for two test cells, one operated with (enhanced) and another without leachate recirculation at Odayeri Sanitary Landfill were compared using their bio-chemical methane potentials (BMP). Initial methane potential is approximately 34.5 m3 CH₄/wet ton of solid waste. The remaining methane potential for the control (C1) and the enhanced (C2) cells are 32.6 m3 CH₄/wet ton and 31.1 m3 CH₄/wet ton of refuse after eight months of operation, respectively. The produced CH₄ quantities for C1 and C2 after eight months of operation are 1.9 m3 CH₄/wet ton and 3.4 m3 CH₄/wet ton, respectively. On the other hand, 5.5% and 9.9% of the total potential are generated in eight months. However, the CH₄ generation rates for the first year are determined as 2.85 and 5.10 m3/ton/year for C1 and C2 test cells, respectively. Due to the appropriate conditions such as moisture content, solid waste decomposition rate is enhanced at a rate of 79% at C2 test cell relative to C1 test cell. Hence, C2 test cell shows more decomposition relative to the C1 test cell.     

Nitrification of centrate from dewatering of anaerobically digested sludge

Nitrification of anaerobically digested sludge centrate was studied in bench-scale suspended growth and fixed film enhanced suspended growth systems at temperatures of 10.5-28.5°C and pH values of 6.0-9.1. Nitrification followed zero-order kinetics in both systems, and ammonia removals in excess of 99% were observed. The temperature dependency of the suspended growth nitrification rate observed under not fully acclimated biomass conditions at pH between 6.8 and 8.5, was expressed as k_T = k₂₀θ^T-20where k₂₀ and θ were found to be 0.34 mg NH₃-N/MLVSS-d and 1.033, respectively. The nitrification rate in the fixed film enhanced suspended growth system involving styrofoam pads ranged from 0.11 to 0.13 mg NH₃-N/mg MLVSS-d at temperatures of 21.5-25°C and pH values of 7.8-8.6. The process contained suspended solids in the range of 10-20 mg/l.     

Interaction between air pollution and meteorological parameters in Erzurum, Turkey

In recent years, the rapid increase in population density has caused increases in the consumption of fuel, and the outdoor air quality has deteriorated in the crowded urban areas of Turkey. Erzurum, a city in the eastern part of Turkey, is influenced by air pollutants such as SO₂ and suspended particles. It is known that, in general, the air pollution concentrations have a close relationship with meteorological factors. In this study, the relationship between outdoor air quality data and meteorological factors, such as wind speed, rainfall, temperature, sunshine hours and relative humidity, is statistically analysed, using the code SPSS. According to the results obtained through multiple linear regression analysis, there are moderate levels of correlation between SO₂ and particle concentrations and meteorological factors in Erzurum.