Multivariate Stochastic Models of Sulphur Dioxide Pollution in an Urban Area

Three multivariate stochastic mathematical models of daily SO₂ pollution in an urban area (Milan, Italy) during the heating season (mid-October/end of March) are illustrated in the paper. Each model is characterized by a different number of external inputs. Precisely, the first model has no inputs (it is simply an autoregressive relationship), the second one has a temperature input (roughly accounting for emission), the third one has two inputs (temperature and wind speed). From each model a real-time predictor is derived, namely a recursive relationship which, at the end of each day, allows future pollution levels to be forecast on the basis of current concentration and meteorological measurements. The quality of the forecast is rather satisfactory, even in episode situations. The improvements in forecast performance when turning from a predictor with less external inputs to a predictor with more external inputs (i.e., when exploiting more information about meteorology) are also pointed out in the paper.     

Characterization of Several Integrative Sampling Methods for Nitric Acid,Sulphur Dioxide and Atmospheric Particles

Laboratory and field experiments were performed to evaluate integrative measurement methods for atmospheric nitrates, sulphate and sulphur dioxide. Denuder tubes and several filter media were tested under laboratory and field conditions. Effects of sampling variables such as temperature and relative humidity, flow rates, concentration, loading capacity and artifacts due to NO, NO₂ and SO₂ were also evaluated. The integrative filter sampling method and the ion chromatographic analytical procedure gave a measurement precision (relative standard deviation) of ±11.5 percent for particulate NO₃ ^? on Teflon and ±15.6 percent for gaseous HNO₃ on nylon; for both these constituents, the detection limit was about 0.1 μ m^?3.     

海门市城区二氧化氮污染物浓度呈上升趋势的调查与分析

通过调查海门市城区所有NOX和NO2排放源,从排放情况和NO2月浓度变化情况分析,得出了海门市城区NO2污染物浓度呈上升趋势的结果。     

关于SO2排污权交易试点工作的思考

论述了实施排污权交易的背景、目标和意义,阐述了实施排污权交易的指导思想及基本做法,分析了排污权交易实施过程中的薄弱环节和存在的主要问题,在此基础上,提出进一步完善排污权交易工作的几点措施.     

Application of the Active Soda Process for Removing Sulphur Dioxide from Flue Gases

The active soda process1 was applied for desulfurlzatlon of flue gases emitted by a plant burning heavy fuel oil In a rotary drum drier for stone aggregate. The flue gas capacity of the plant was about 6,7 m³/s at normal conditions. The SO₂ concentration varied between 400– 500 ppm. The solid, dry and fine-grained NaHCO₃ of good quality was fed directly into the hot gas stream at the outlet of the rotary drier In two variants—with and without grinding. The mean particle size was 0.180 m^-3 or 0.070 m^-3, respectively. The achieved desulfurizatlon degree was shown to be directly dependent on the flue gas temperature and on the grinding effect, as well as on the normalized stoichiometric ratio. The highest achieved desulfurization degree amounted up to 74 percent. During the design of the desulfurization process no pilot plant installations and tests were necessary, and for the final process no special chemical reactor was used.     

Development of Models for Predicting the Distribution of Indoor Nitrogen Dioxide Concentrations

Extensive data on residential indoor and outdoor NO₂ levels have been collected in a limited number of U.S. locations. To date, researchers have analyzed these data sets individually, but have not analyzed them in the aggregate. Results have not, therefore, been suitable for application in a nationwide exposure assessment. This paper presents an analysis of indoor and outdoor NO₂ field measurements from five U.S. metropolitan areas for homes with gas-fueled ranges and discusses potential applications of the results. Using linear regression analysis, the relationship between indoor NO₂ and various predictor variables was explored. Results indicated that ambient NO2 levels alone explain an estimated 37 percent of the variability in indoor NO₂ levels, that the relationship between indoor and outdoor NO₂ concentrations differs significantly from summer to winter months, and that homes with range pilot lights have indoor levels approximately 7 ppb greater than homes without pilot lights. A logistic regression model which predicts the distribution of indoor NO₂ levels based on ambient NO₂ concentrations was developed. Estimation and testing of the logistic model indicated good model performance. The model is particularly useful for addressing policy-oriented questions that involve the concept of "acceptable" threshold levels for human exposure to NO₂.     

API 100E型SO2监测仪的维护要点

主要阐述了API 100E型SO2监测仪的维护要点。     

Atmospheric fall-out of metals around the Murano glass-making district (Venice,Italy)

Background, aim and scope  

Murano’s glass-makers have held a monopoly on quality glass-making for centuries known all over the world. Artistic glass manufacture entails exposure to complex mixtures of pollutants, including metals. A few studies have reported high levels of trace elements in marine waters, sediments and mussels around Murano and shown that emissions from Murano glass-making workshops significantly influence air quality in the Venice area. Nevertheless, to date, there is very little information on atmospheric concentrations and virtually none on atmospheric deposition fluxes of trace elements around the island. This study presents data on the distribution of trace elements in the air and atmospheric depositions around Murano, based on a 2-year sampling period.     

Atmospheric Factors Influencing Daily Sulfate Concentrations in Chicago Air

Abstract

Confidence interval construction for central tendency is a problem of practical consequence for those who must analyze air contaminant data. Determination of compliance with relevant ambient air quality criteria and assessment of associated health risks depend upon quantifying the uncertainty of estimated mean pollutant concentrations. The bootstrap is a resampling technique that has been steadily gaining popularity and acceptance during the past several years. A potentially powerful application of the bootstrap is the construction of confidence intervals for any parameter of any underlying distribution. Properties of bootstrap confidence intervals were determined for samples generated from lognormal, gamma, and Weibull distributions. Bootstrap t intervals, while having smaller coverage errors than Student's t or other bootstrap methods, under-cover for small samples from skewed distributions. Therefore, we caution against using the bootstrap to construct confidence intervals for the mean without first considering the effects of sample size and skew. When sample sizes are small, one might consider using the median as an estimate of central tendency. Confidence intervals for the median are easy to construct and do not under-cover. Data collected by the Northeast States for Coordinated Air Use Management (NESCAUM) are used to illustrate application of the methods discussed.     

Estimation of Trends in Atmospheric Concentrations of Sulfate in the Northeastern United States

Abstract

Daily atmospheric concentrations of sulfate collected at six locations in the northeastern United States are regressed against meteorological factors, ozone, seasonal cycles, and time in order to determine if a significant trend in sulfate can be detected. The data used in this analysis were collected during the Sulfate Regional Experiment (SURE, 1977-1978) and the Eulerian Model Evaluation Field Study (EMEFS, 1988-1989). Ozone, specific humidity, and seasonal terms (reflecting the potential of the atmosphere for oxidation of sulfur dioxide) emerged as important explanatory variables. After accounting for the variability explained by environmental factors, the median estimated change in sulfate concentration from the six locations over the 11-year period is -22% (or -28% if ozone is not used as an explanatory variable). Although there are wide variations among locations, these changes are commensurate with an estimated 25% decline in sulfur emissions in the northeastern U.S. during the same period. These analyses provide insight into methods for detecting reductions in sulfate that may be expected to occur as a result of the Clean Air Act Amendments of 1990. Uncertainties in the estimates, with consideration of serial correlation in the data, imply a minimum detectable reduction of 10% using this modeling procedure with similar data availability.     

Impact of Microenvironmental Nitrogen Dioxide Concentrations on Personal Exposures in Australia

ABSTRACT

Indoor and outdoor NO₂ concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO₂ levels and the presence of a gas range in the home were significantly associated with personal exposure. The time-weighted average of personal exposure was estimated using NO₂ measurements in indoor home, indoor workplace, and outdoor home levels. The estimated personal exposures were closely correlated, but they significantly underestimated the measured personal exposures. Multiple regression analysis using other nonmeasured microenvironments indicated the importance of transportation in personal exposure models. The contribution of transportation to the error of prediction of personal exposure was confirmed in the regression analysis using the multinational study database.     

Sources and Concentrations of Indoor Nitrogen Dioxide in Barcelona,Spain

Abstract

Sources and concentrations of indoor nitrogen dioxide (NO₂) were examined in Barcelona, Spain, during 1996– 1999. A total of 340 dwellings of infants participating in a hospital-based cohort study were selected from different areas of the city. Passive filter badges were used for indoor NO₂ measurement over 7–30 days. Dwelling inhabitants completed a questionnaire on housing characteristics and smoking habits. Data on outdoor NO₂ concentrations were available for the entire period of the study in the areas of the city where indoor concentrations were determined. Bivariate analysis was performed to investigate relationships between indoor NO₂ concentrations on one hand and outdoor NO₂ concentrations, housing, and occupant characteristics on the other. Stepwise multiple linear regression was performed with variables that were 1996 and 27.02 ppb in 1999, with the highest yearly value of 27.82 ppb in 1997. In the same time period, mean outdoor NO₂ concentration ranged between 25.26 and 25.78 ppb with a peak of 30.5 ppb in 1998. Multiple regression analysis showed that principal sources of indoor NO₂ concentrations were the use of a gas cooker, the absence of an extractor fan when cooking, and cigarette smoking. The absence of central heating was also associated with higher NO₂ concentrations. Finally, each ppb increase in outdoor NO₂ was associated with a 1% increase in indoor concentrations.     

Evaluation of the Effectiveness of The Lead Peroxide Method for Atmospheric Monitoring of Sulfur Dioxide

This paper presents a simplified analysis to determine the variables that affect the empirical correlation factor used in the lead peroxide method. The rate of sulfation has been determined from two different models. In the first model, the mass transfer rate is calculated from the gas phase resistance alone whereas in the second model, the diffusion resistance in the gel phase is assumed to be the rate limiting step. Although the gas phase and the gel phase resistances may be both important in the actual case, it has been found that the correlation factor based on the first model is adequate to describe general experimental observations. Reasonable agreement has been obtained between the measured and the calculated va|ue of the correlation factor.     

The Absorption of Atmospheric Sulfur Dioxide by Water Solutions

Results of a laboratory study indicate that the rate of solution of atmospheric sulfur dioxide in distilled water, over the range of atmospheric concentrations of 0.81?8.73 mg SO₂/M³, is a function of the concentration of SO2 in the atmosphere, with saturation being reached more rapidly at the higher concentrations. This would indicate that rain water, with constantly renewed surfaces, can be very effective in the removal of atmospheric SO₂. The pH of the exposed water samples reached values of 4.0 or less, comparable to values observed in fog and cloud water near large industrial areas. Overall solubility of sulfur dioxide in distilled water did not follow the law of partial pressure. At the atmospheric concentrations used it was found that over 98.5% of the sulfite in solution was in the form of the bisulfite ion with, the remainder present as unionized sulfurous acid. Computations using the concentration of unionized sulfurous acid in the solution showed that the solubility of this portion of dissolved sulfite did follow the law of partial pressure.     

API MODEL 100A光路系统对二氧化硫测定值的影响

通过比较二氧化硫测定值与紫外灯强度、紫外检测器调节值及光电倍增管高压值的关系，提出二氧化硫测定值与紫外灯强度、光电倍增管高压值成正比，与紫外检测调节值成反比的结论，并对仪器校准提出了有效性建议。     

The Survival of Airborne Serratia marcescens in Urban Concentrations of Sulfur Dioxide

Aerosols of Serratia marcescens ATCC 274 were suspended in a 709L rotating drum at 20 ± 1 °C and high to mid-range relative humidities. At specified times after bacterial aerosolization, sulfur dioxide was added to concentrations of 2.5, or 5 mg/m³. Viable cell decay rate constants, in control aerosols without added sulfur dioxide, increased rapidly from near 100% to 60% RH in the first hour (termed: young aerosol) of suspension, and from a minimum rate constant at 80% in the succeeding four hours (termed: old aerosol).Upon addition of sulfur dioxide to a cloud of S. marcescens, generally, viable cell decay rate constants increased further. One exception was at 80% relative humidity where maximum resistance to SO₂ accelerated death was observed for old aerosols. Cells in young aerosols were particularly sensitive to SO₂ addition at mid-range humidities, while in older aerosols the cells were insensitive to up to 5 mg SO₂/m³ introduced at high RH; but were up to 10 times more sensitive than cells in young aerosols to a given increase (from 2.5 to 5 mg/m³) in SO₂ concentration at mid-range humidities.     

A Rapid Titrimetric Method for Sulfate in Lead Dioxide Exposed to Atmospheric Sulfur Pollution

A titrimetric method is described for the analysis of sulfate in lead dioxide candles which have been exposed to atmospheric sulfur pollution. The time taken to analyse one sample is 3 hr. Sixty milliliters of 8% ammonium carbonate solution is used to convert the lead sulfate present on the candle to ammonium sulfate. The solution is filtered lc remove lead dioxide, and an aliquot of the filtrate is heated to remove ammonium carbonate. The solution of ammonium sulfate remaining is titrated directly for sulfate with 0.02 M barium perchlorate, using Thoron as indicator. The accuracy of the method is ±10 and ±6 % of theoretical, for 10 mg, and 40 mg or greater amounts of sulfate, respectively. For 2 mg of sulfate, results are about 20% high. Good agreement has been obtained between results for duplicate field candles, analyzed by the standard sodium carbonate gravimetric method, and the method presented, over a five-month period.     

A Multivariable Model for Atmospheric Dispersion Predictions

In conjunction with a 15-month air quality survey of Jacksonville, Fia., a mathematical model has been developed to describe the dispersion of atmospheric pollutants. The source inventory used with the model was compiled, in part, from the data obtained from the sampling of all major sources within the area. The major sources were considered separately from the one-mile square area sources which accounted for the remainder of the emissions. Meteorological data was recorded continuously in the city including vertical temperature observations to 750 ft. The model was compiled in FORTRAN and can be used for both gaseous and particulate pollutants, by utilizing proper decay rates. The variant nature of meteorological parameters and emission rates are considered. The ground level concentrations of several pollutants which were determined for 24 hr periods at 11 sites and continuously at two other sites were used to check the model. A limited tracer study was carried out in conjunction with the project.