GIS Atmospheric Chemical Fate Model Simulation of Iron Released from High Intensity Bombing in Northwestern Laos

Abstract

The atmospheric dispersal of iron fragments ejected from detonated ordnance released within the Nam Souy sub-basin during the secret bombing campaign of Laos from 1965 ~ 1973 was simulated through python integration with ArcGIS. The data for the study was obtained from the US National Archives and shows that of a total of 7,667,619 weapons delivered in Laos (4.5 million tons), 19,005 (5,900 tons) were dropped within the study site. The simulation adapted Gaussian isotropic puff modeling for the dust/grain-sized fragments and explosive force radial release modeling for the larger fragments into python script to produce temporal raster output images of the dispersal patterns of the analyte. The use of code language libraries ArcPy, NumPy, and numba and the logic for their application is discussed and reported along with the script developed. The simulation produced 9 m2 resolution raster images displaying iron material loading at ground level. Loading density is reported at a range between 0 ~ 7.5 g/m2 washable iron load, 0 ~ 0.65 kg/m2 of suspended iron load, and 0 ~ 3.5 kg/m2 of bedded load. The results are intended for use in subsequent studies of surface removal over time with a potential application in exposure risk analysis and for the assessment of impact on natural environments.

Keywords: atmospheric material dispersal, chemical fate modeling, environmental risk assessment, Geographical Information Systems, high intensity warfare, iron, ordnance, Python