The effects of natural hydrocarbons must be considered in order to develop a reliable plan for reducing ozone in the urban atmosphere. Trees can emit significant quantities of hydrocarbons to metropolitan areas such as Atlanta, and model calculations indicate that these natural emissions can significantly affect urban ozone levels. By neglecting these compounds, previous investigators may have overestimated the effectiveness of an ozone abatement strategy based on reducing anthropogenic hydrocarbons.
A one‐dimensional, time‐dependent, photochemical model is used in conjunction with data obtained during the dry‐season portion of NASA's Global Tropospheric Experiment and Brazil's Instituto Nacional de Pesquisas Espaciais (INPE) (National Institute for Space Research) Amazon Boundary Layer Experiment (ABLE 2A) to simulate the chemistry of the dry‐season Amazon troposphere. The background atmosphere, unperturbed by the presence of emissions from biomass burning, is simulated with inputs of surface sources and deposition of various species measured during ABLE 2A. The presence of haze layers over a region is simulated by the imposition of profiles of species characteristic of haze within the model for 12 hours. The inclusion of hydrocarbons within the modeled haze is found to approximately double the calculated in situ ozone production rate. The difference between the calculated total column ozone production rates in the haze simulation and the background simulation is the model‐predicted enhancement of the in situ ozone production due to regionally transported haze layers (up to 1000 km transport distance). The predicted enhancement of ozone is between 0.3 and 2.9 × 1011molecules O3 cm−2 s−1, near the range of observed rates of ozone increase over the Amazon Basin during the dry season. This suggests that the regional transport of haze during the southern tropical burning season is an important factor in explaining the increase of ozone observed annually during this period.
Abstract. Aerial emission sampling of four natural gas boiler stack plumes was
conducted using an unmanned aerial system (UAS) equipped with a lightweight
sensor–sampling system (the “Kolibri”) for measurement of nitrogen oxide
(NO), and nitrogen dioxide (NO2), carbon dioxide (CO2), and carbon
monoxide (CO). Flights (n = 22) ranged from 11 to 24 min in duration at
two different sites. The UAS was maneuvered into the plumes with the aid of
real-time CO2 telemetry to the ground operators and, at one location, a
second UAS equipped with an infrared–visible camera. Concentrations were
collected and recorded at 1 Hz. The maximum CO2, CO, NO, and NO2
concentrations in the plume measured were 10 000, 7, 27, and 1.5 ppm, respectively. Comparison of the NOx emissions between the stack
continuous emission monitoring systems and the UAS–Kolibri for three boiler
sets showed an average of 5.6 % and 3.5 % relative difference
for the run-weighted and carbon-weighted average emissions, respectively. To
our knowledge, this is the first evidence of the accuracy performance of
UAS-based emission factors against a source of known strength.
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