Volatile Emissions of Ammonium Nitrate under Flowing Conditions

Abstract

1IntroductionThe physical properties of low-volatility military explosives, e.g.,T NT and RDX, have been well characterized,g uiding trace explosives detection efforts worldwide. Due to their simple accessibility and formidable potency,t he explosives comprising improvisede xplosive devices (IEDs) have garnered significant attention in recent years. While the physical properties for some of these explosives, including TATP, are generally well understood, others, such as ammonium nitrate (AN), are not as well characterized.Extensived ata regardingA Na erosols formed in the atmosphere exists as scientists have studied the presence of ammonia and nitric acid in the atmosphere, stemming from multiple anthropogenic sources [1].A tmosphericd ata collected in variousr egions of California [2-5] as well as Japan [6] show thata mmonium nitratea erosol concentrations are in the low to mid mgm À3 range and vary considerably within geographical regions.E ven in regions where relatively low levels are found, it is reasonable to expect, at am inimum, low parts per billion by volume (ppbv) of ammonia and nitric acid as background contamination [4]. Clearly,d etecting an AN-based IED will always be frustrated by the presence of ammonium nitrate aerosols in equilibrium with ammonia and nitric acid vapors.F urthermore, when attempting to generate aq uantitative level of AN vapor in the laboratory,avery careful characterization of the backgroundl evels of ammonia and nitric acid is necessary.

ANFO vapour detection with conducting polymer percolation network sensors and GC/MS

“…However, it slowly degrades into NH 3 and HNO 3 , resulting in vapour pressures similar to those of TNT. 2 Therefore it is likely that when detecting the crushed fertiliser sample, the sensor is in fact responding to the emitted NH 3 . Using a calibration curve based on the sensor response to known NH 3 concentrations it is possible to estimate the concentration of the NH 3 measured when detecting the fertiliser sample (Fig.…”

“…The most commonly used types of IEDs are based on easily accessible materials, such as ammonium nitrate/fuel oil (ANFO) mixtures and perchlorates. 1 Vapour sensing of ammonium nitrate/fuel oil (ANFO) is especially challenging because the fertilisers commonly used as the ammonium nitrate (AN) component are not volatile, although their decomposition products are, 2,3 whereas fuel oils such as diesel are omnipresent and can cause a high false positive rate.…”

Passive delivery of mixed explosives vapor from separated components

“…A Ammonium nitrate breaks down into ammonia and nitric acid under ambient conditions. The nitric acid is readily taken up by any water that has absorbed to the bulk AN due to ambient humidity, leaving ammonia as the main headspace component of AN [20]. Passive ammonia samplers (Ogawa Co.; Pompano Beach, FL) were utilized to collect this ammonia vapor from the headspace of the explosive mixtures, as well as AN alone.…”

Detection of antipersonnel landmines containing ANFO-based explosive: A review

“…For the purposes of ANFO detection means that these vapors can be used as target analytes. The majority of detection methodologies for APLs have been focused on the detection of ammonia [10] because a higher concentration of ammonia is expected near ANFObased explosive devices [9]. This due to the vapor pressure for ammonia and nitric acid, 8.6 x 10 5 and 3.3 x 10 3 Pa, respectively.…”