Measuring reactive nitrogen emissions from point sources using visible spectroscopy from aircraft

Accurate measurements of nitrogen dioxide (NO2), a key trace gas in the formation and destruction of tropospheric ozone, are important in studies of urban pollution. Nitrogen dioxide column abundances were measured during the Texas Air Quality Study 2000 using visible absorption spectroscopy from an aircraft. The method allows for quantification of the integrated total number of nitrogen dioxide molecules in the polluted atmosphere and is hence a useful tool for measuring plumes of this key trace gas. Further, we show how such remote-sensing observations can be used to obtain information on the fluxes of nitrogen dioxide into the atmosphere with unique flexibility in terms of aircraft altitude, and the height and extent of mixing of the boundary layer. Observations of nitrogen dioxide plumes downwind of power plants were used to estimate the flux of nitrogen oxide emitted from several power plants in the Houston and Dallas metropolitan areas and in North Carolina. Measurements taken over the city of Houston were also employed to infer the total flux from the city as a whole.     

Airborne observations of vegetation and implications for biogenic emission characterization

Measuring hydrocarbons from aircraft represents one way to infer biogenic emissions at the surface. The focus of this paper is to show that complementary remote sensing information can be provided by optical measurements of a vegetation index, which is readily measured with high temporal coverage using reflectance data. We examine the similarities between the vegetation index and in situ measurements of the chemicals isoprene, methacrolein, and alpha-pinene to estimate whether the temporal behavior of the in situ measurements of these chemicals could be better understood by the addition of the vegetation index. Data were compared for flights conducted around Houston in August and September 2000. The three independent sets of chemical measurements examined correspond reasonably well with the vegetation index curves for the majority of flight days. While low values of the vegetation index always correspond to low values of the in situ chemical measurements, high values of the index correspond to both high and low values of the chemical measurements. In this sense it represents an upper limit when compared with in situ data (assuming the calibration constant is adequately chosen). This result suggests that while the vegetation index cannot represent a purely predictive quantity for the in situ measurements, it represents a complementary measurement that can be useful in understanding comparisons of various in situ observations, particularly when these observations occur with relatively low temporal frequency. In situ isoprene measurements and the vegetation index were also compared to an isoprene emission inventory to provide additional insight on broad issues relating to the use of vegetation indices in emission database development.     

The toxicity of several oil-spill removers to some species of fish and shellfish

Increasing quantities of crude oil and oil products are now being transported by sea, and this has resulted in a greater risk of oil pollution of coastal waters and has increased the dangers to marine life and amenities. With this increase in oil pollution have come various methods of treatment, among the more successful of which have been the so-called oil-spill removers or detergents. The toxicity of 12 of these materials, more accurately known as solvent emulsifiers, was examined, using 4 marine species of shellfish. Using 2 of these test species the toxicities of 3 solvent emulsifiers were examined in more detail, particular attention being paid to the time of exposure at different concentrations required to cause death. The effect of crude oil mixed with these 3 materials was also examined. Details are also given of some preliminary experiments with solvent emulsifiers on larvae of the shore crab (Carcinus maenas) and the brown shrimp (Crangon crangon).