• 期刊
• OpenAccess

Quantifying Emissions of PM_(10) Generated by the Implosion of Concrete Grain Silos

This study quantified the effect of imploding old concrete grain silos in Aqaba, Jordan, on the eastern side of the Gulf of Aqaba, an arid region, on air quality by measuring the PM_(10) concentrations before and after the implosion at four monitoring locations. The implosion of the silos forms part of a comprehensive plan to relocate and upgrade the Port of Aqaba, which is situated on the coast of the Red Sea, with the goal of freeing space for development and improving the infrastructure in the heart of the city. The demolition, which occurred at 11:00 a.m. (local time) on 13 January 2019, generated a massive cloud of dust that was transported to nearby areas. To characterize these emissions, descriptive statistics, graphical methods, inverse distance weighting interpolation, decision trees constructed with recursive partitioning, the Gaussian dispersion model, the modified box model, and regression analysis were applied. The PM10 concentrations were in compliance with the Jordanian 24-h standard of 120 μg m^(-3) prior to the implosion but substantially increased (although still varied by distance from the demolition site) at all four stations afterward, with the maximum values (259-587 μg m^(-3)) exceeding the pre-implosion ones by as much as 26 times. However, these high concentrations were short-lived, and the majority of the stations returned to background levels within 30-33 hours. According to our calculations on the implosion, the PM_(10) emission rate was 17 ± 2 mg m^(-2) s^(-1), which is equivalent to 215 ± 22 kg silo^(-1), and the air mixing height was 613 ± 72 m, or approximately eight times the height of the silos.

• 期刊
• OpenAccess

Formation and Evolution Mechanisms of Severe Haze Pollution in the Sichuan Basin, Southwest China

Severe haze episodes are important environmental issues, and the rapid formation and evolution mechanisms of such episodes over complex terrain remain poorly understood. The Sichuan Basin (SCB) periodically experienced heavy haze pollution during the winter of 2016, with the maximum regional average PM_(2.5) concentration reaching almost 120 μg m^(-3). In this study, we characterize a severe haze episode in the SCB from 20 to 30 January 2017 using comprehensive measurements and model analyses. The evolution of this severe episode shows clear stages, with gradual PM_(2.5) increases under stagnant weather conditions in Stage I (aerosol accumulation stage) and with explosive PM_(2.5) increases mainly associated with cross-border transport from the southern SCB in Stage III (rapid formation stage). The process analysis results indicated that primary emissions and aerosol processes were the major sources of PM_(2.5) in these urban regions, whereas vertical transport and dry deposition generally acted as sinks of PM_(2.5). In the presence of southwesterly synoptic winds, the aerosols emitted from the southern SCB were transported to Chengdu and the surrounding areas through horizontal transport and accounted for 66% of the PM_(2.5) concentration in Chengdu during Stage III. Our results reveal the detailed formation mechanism of a severe haze episode in the SCB under the effects of regional transport and synoptic forcing patterns to improve the understanding of haze formation in areas with complex terrain.

• 期刊
• OpenAccess

Inhibition Behavior of PCDD/Fs Congeners by Addition of N-containing Compound in the Iron Ore Sintering

PCDD/Fs are typical toxic persistent aromatic compounds that greatly reduce air quality and harm human health. In this study, urea's suppressive effect on PCDD/Fs and their congener emissions was investigated via sintering pot tests, and the inhibition mechanisms were studied. The results showed that the I-TEQ values for the total PCDD/Fs decreased from 0.50 to 0.20, 0.12 and 0.20 ng I-TEQ Nm^(-3) after adding solid 0.02, 0.035 and 0.05 wt.% urea particles, respectively, to the iron ore sintering mixture, but these values increased for the low-chlorinated TeCDFs (from 0.003 to 0.009, 0.006 and 0.006 ng I-TEQ Nm^(-3)) and TeCDDs (from 0.014 to 0.020, 0.018 and 0.020 ng I-TEQ Nm^(-3)). Moreover, the average I-TEQ values for the chlorine substituents in the PCDFs and PCDDs decreased, indicating that urea inhibited chlorination or enhanced dechlorination. The potential mechanisms by which urea suppresses the total PCDD/Fs and hydrodechlorinates the high-chlorinated PCDD/Fs are discussed.