Atmospheric Environment. Part B. Urban Atmosphere最新文献

Over the past 20 years, the U.S. Congress has passed four acts relating to clean air. The 1970 act set out a comprehensive plan for federal-state partnership to require all areas in the country to meet National Ambient Air Quality Standards. In 1977, the act was amended and expanded, both to address many of the problems encountered in the 1970 act and to reorient the law to limit significantly emissions of any sort, even if there were no currently identified health-related reasons. In 1986, the Emergency Planning and Community Right-to-know Act was passed, as an amendment to a solid waste law, in response to the desire to prevent chemical release tragedies. After 10 years of effort, Congress finally passed the 1990 Clean Air Act amendments which require a number of new programs aimed at curbing urban ozone, rural acid rain, stratospheric ozone, toxic air pollutant emissions and vehicle emissions, and establishing a new, uniform national permit system.

This paper discusses some of the consequences of the various acts and suggests ways that others might learn from our 20 years of experience. Certain programs have worked quite well, while some alternatives could have improved other programs.

In Japanese urban areas, NO_x air pollution has recently become more and more serious, and a rise in atmospheric temperature has been observed. This correlation was surveyed in 187 locations, where NO₂ concentration monitoring and atmospheric temperature measurement were conducted simultaneously and separately during the same period from 1982 to 1988. The following results were obtained. First, the percentage of areas where NO₂ concentration increased was 72%. Second, the percentage of areas where the correlation coefficient between the annual mean NO₂ concentration and the elapsed years was larger than 0.20, and at the same time the correlaltion coefficient between the annual mean NO₂ concentration and the annual mean atmospheric temperature was larger than 0.20, was 23%. About three-quarters of these areas were in the Tokyo and Osaka megalopolis. Third, in these areas, the relation between the mean NO₂ concentration and the regression coefficient of the change in atmospheric temperature relative to the change of annual mean NO₂ concentration was suspected to be distributed steeply with a reflected point in NO₂ concentration.

A time-dependent finite difference model in three levels combined with a puff model to account for subgrid effects close to single sources was used to calculate hour-to-hour concentration distributions. Measurements from several selected stations were used to account from time variation in background concentrations. For each hour, weight was given to observed values in areas that were not influenced by local sources.

Results of concentration calculations based on hourly data on emission and dispersion are validated by measured time series of SO₂ and NO_x at five stations. A combination of hourly nephelometer readings and 12-h measurements of small particles at three stations are compared with calculated values.

Hourly observed and calculated values from two periods (3 January–15 March 1988 and 18 April–24 June 1988) were used for the evaluation of the model for calculating hourly pollution concentrations in each square kilometre. The results showed that prediction of short-term average concentrations (e.g. hourly data) are usually poorly correlated with observations at the same time and location. Slight displacement errors may cause point-to-point correlation to be poor as a result of errors in input data.

The pattern of NO_x concentration variation with time was reproduced well at all stations. A subgrid model taking into account the influence of nearby roads would probably improved the model for NO_x at some stations. For SO₂ and small particles, industrial sources have the dominant influence and the correspondence between observed and calculated values were improved by taking into account spatial uncertainty and an hourly variation in background concentrations.

Particulate measurements made in Katowice, Poland, in 1989 (prior to political changes in Eastern Europe and the resulting decrease in industrial production) indicate total suspended particulate levels that are 3–10 times higher than in other European cities. The concentrations of cadmium, nickel and manganese were also significantly higher than in other places in Europe. However, lead concentrations were comparable to European cities with high automobile traffice. The modes and concentration levels of the Katowice aerosol were highly direction dependent, which indicates that most of the sampled particles were locally or regionally emitted into the atmosphere.

The CRSTER and MPTER computer codes are two of many air quality dispersion models recommended for use in a regulatory context by the U.S. Environmental Protection Agency. CRSTER and MPTER are generally applicable to tall stack sources, such as coal-fired electrical utility power plants located in flat or gently rolling terrain. This paper briefly reviews the developmental history, formulation, operation and application of the CRSTER and MPTER models. Also reviewed are performance evaluation studies which have included these two models. The paper concludes with a brief discussion of future directions for regulatory modeling of tall stack sources.

A statistical time series analysis was applied to study the interdependence between the primary and secondary pollutants in the Taipei area. Estimations using the vector autoregression model (VAR) indicate that 2 and 4 h time lags are sufficient to represent the observed values at two stations studied. The impulse response functions and variance decompositions of NO, NO₂ and O₃ were derived using the vector moving average representations to examine the significance of one species on others. Influences of photochemistry and transport processes on these air pollutants at different locations were evaluated from the results. This technique may provide a simple tool for preliminary assessment of pollution problems.

Artificially enriched isotopes of neodymium (Nd) were released from a 100 MW(e) coal-fired power plant at rates ranging from 40 to 61 mg h⁻¹ in an experiment designed to test a new intentional particulate tracer technique. During each release, ambient samples of airborne particles with diameters < 2.5 μm were collected for 6 h at 13 locations along a 72° arc 20 km from the plant on 47-mm diameter Teflon filters operated at nominal flow rates of 130 l min⁻¹. Samples collected when estimates of the meteorological dispersion parameter, X/Q, ranged from 0.3 × 10⁻¹⁰ to 350 × 10⁻¹⁰ s m⁻³, were analysed for total Nd mass and excess ¹⁴⁸Nd, the tracer isotope, by thermal-ionization mass spectrometry. Measured concentrations were in good agreement with predictions of ambient tracer concentrations made with a Gaussian plume model in which lateral and vertical plume dispersion parameters were derived from the standard deviation of the horizontal wind direction. The observed tracer concentrations correspond to signal-to-noise ratios (S:N) of 150–450. The concentration of ¹⁴⁸Nd measured in particles <0.65 μm in diameter corresponds to an S:N in excess of 4500.