A series of mesoscale burns were conducted in 1998 to assess fire-resistant booms, twelve of these were used to study emissions from diesel oil burns. Extensive sampling and monitoring were conducted to determine the emissions at nine downwind ground stations, one upwind ground station, and at six side stations. Particulates were measured using high-volume samplers and real-time particulate analyzers. Particulate samples in air were taken and analyzed for polycyclic aromatic hydrocarbons (PAHs). Water under the burns was analyzed; small amounts of PAHs were found. The burn residue was analyzed for PAHs as well. PAHs were at about the same concentration in the residue than in the starting oil, however, there is a slight differential concentration increase in some higher molecular weight species in the residue. Combustion gases including carbon dioxide, sulphuric acid aerosols, and sulphur dioxide were very low and in some cases undetectable. Volatile organic compound (VOC) emissions were measured in Summa canisters. Over 100 compounds were identified and quantified; most concentrations were too low to be considered a health risk. It was concluded that small burns of this size (burn area about 25 m2) are too small to pose a health hazard.
Over 45 mesoscale burns were conducted to study various aspects of diesel and crude oil burning in situ,. Extensive sampling and monitoring of these burns were conducted at downwind stations, upwind stations, and in the smoke plume. Particulate samples were taken in air and analyzed for polycyclic aromatic hydrocarbons (PAHs). PAHs were found to be lower in the soot than in the starting oil, although higher concentrations of the larger molecular PAHs were found in the soot and residue, especially for diesel burns. Overall, the amount of PAHs in the soot and residue were about 2 to 8% of that in the starting oil. This implies a destruction of PAHS by 92 to 98%. Particulates in the air were measured by several means and were found to be greater than recommended exposure levels up to 500 meters downwind at ground level, depending on the size and type of fire. Diesel fires emit much more particulate matter and have longer exposure zones. Combustion gases including carbon dioxide and carbon monoxide are below exposure level maximums. Volatile organic compound (VOC) emissions are extensive from fires, but the levels were less than from an evaporating crude oil spill. Over 140 compounds were identified and quantified. Carbonyls, including aldehydes and ketones, were found to below human health concern levels.
Emission data from over 45 experimental burns have been used to develop prediction equations for over 150 specific compounds or emission categories. These are used to calculate safe distances and levels of concern for a standard burn size of 500 square meters, an amount that would typically be contained in a boom. The safe distance for a crude oil burn of this size is about 500 m and for a diesel burn, much further.
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