Study on the potential risks under a hazardous gas leakage accident: effects of source characteristics and ambient wind velocities

In this study, a full-scale storage tank was established to investigate the potential risks of leakage accident. We have developed a series of leak scenarios that close to real accidents and have divided the ambient areas according to relevant regulations. Considering the variety and complexity of real-life accident scenarios, the presented work revealed the combined effect of source release intensity and ambient wind speed on dispersion features by classifying leakage scenarios into active or passive release. The environmental hazards in each area is evaluated under various leak scenarios. The results show that when the approaching wind speed is low, the leakage on the windward side is the most dangerous release pattern. With the increase of the wind speed, the case with jet angle perpendicular to the incoming wind produces the largest cloud volume. Top release is the least dangerous way among the studied leak scenarios. However, the results illustrate that under some release angles, the cloud volume near the tank is not sensitive to wind speed. In leak accidents, quantitatively analysis reveals that the commonly used dimensionless concentrations ([Formula: see text]) cannot be used as a suitable parameter to discuss the concentration field except under top/leeward passive release conditions. This study will be beneficial to on-site rescue and decision-making when leakage accidents occur and provide reasonable suggestions for subsequent research on the environmental impact of container leakage and the diffusion of pollutants.

Measurements, emission characteristics, and control methods of fire effluents generated from tunnel asphalt pavement during fire: a review

Tunnels are widely used in high-grade roads, particularly in mountainous areas; however, tunnel fires often result in severe economic losses and casualties. The fire effluents produced from asphalt pavement have attracted significant research attention. The main objective of this study is to assimilate information on various aspects of bituminous mixture emissions during fires. In this study, the fume emissions of bitumen and bituminous mixtures during combustion are comprehensively reviewed and summarized. First, the test methods for fire effluents produced by bitumen and bituminous mixtures after combustion are summarized. Second, the factors influencing the fume concentration and composition are determined. In addition, different methods to reduce the emission of fire effluents are compared, particularly for the suppression of toxic gas emissions. Then, reasonable suggestions are proposed to reduce the damage caused by hazardous gases to humans and the environment. This review is beneficial for comprehensively understanding the fume emission behaviour and future research on the smoke suppression of highway tunnel asphalt pavements during fires.

Photoexcitation effect on the adsorption of hazardous gases on silica surface

There is very little scientific understanding of photoexcitation effect on the adsorption properties of adsorbent. The adsorption of four hazardous gases (SARIN (propan-2-ylmethylphospho-nofluoridate), methyl dichlorophosphate (MDCP), trimethyl phosphate (TMP) and hydrogen sulfide (H₂S)) on silica surface is taken as target sample in this work. The adsorption energy order (MDCP<SARIN<TMP) in the ground state is consistent with the strength order of intermolecular hydrogen bond (inter-HB) between hydroxyl group of silica surface and hazardous gas, and the desorption order of the three gases in previous reports. However, with the adsorption energy increase of MDCP and the decrease of SARIN and TMP, this order changes remarkably to SARIN<TMP<MDCP after photoexcitation to excited state by absorbing shortwave ultraviolet irradiation. This change is opposite to the inter-HB weakening of MDCP in the first excited (S₁) state and the strengthening of TMP and SARIN in the second excited (S₂) state. This opposite change is caused by formation of intermolecular charge transfer state of MDCP and local excitation of SARIN and TMP. The H₂S is dissociated after photoexcitation to the S₁ state. This work presents photoexcitation as a new standard for the design and detection of adsorption properties of adsorbent for its striking effect on adsorption behaviors.