Potential deterioration of ozone pollution in coastal areas caused by marine-emitted halogens: A case study in the Guangdong-Hong Kong-Macao Greater Bay Area.

Ozone (O3) is one of the most important air pollutants worldwide in terms of its great damage to human health and agriculture. Previous studies show that marine-emitted halogens significantly influence O3 concentrations, mainly through the consumption of O3 by bromine and iodine atoms. In this study, we investigate the temporal variation at finer time scales (daily and hourly) than previous studies (annual or monthly) to better characterize the influence of marine-emitted halogens on coastal O3. In contrast to previous studies that mainly reported a decrease in O3, our results show significant temporal variations in halogen-induced O3 changes. More specifically, the halogen-induced decrease in coastal O3 in southern China is concentrated on clean days, while an unexpected increase in some regions of up to >10 ppbv could occur on polluted days. On polluted days, the activation of particulate chloride (Cl-) in sea salt aerosol (SSA) is effective due to the high level of dinitrogen pentoxide (N2O5) that is formed from the reactions of O3 and nitrogen dioxide (NO2). In addition, the wind fields are unfavorable for the transport of marine air masses with large O3 depletion inland. These two factors together result in the increase in hourly and MDA8 O3 on polluted days in some regions in the GBA. The locations of O3 increases are controlled by the distribution of nitryl chloride (ClNO2) at sunrise, which is influenced by O3 and NO2 during the previous night. As a result, the increase in O3 is a continuation of the O3 pollution from the previous day, and the whole area is under potential threat of this worsening pollution.

Molecular characteristics, sources and influencing factors of isoprene and monoterpenes secondary organic aerosol tracers in the marine atmosphere over the Arctic Ocean.

Biogenic secondary organic aerosols (BSOA) are important components of the remote marine atmosphere. However, the response of BSOA changes to sea ice reduction over the Arctic Ocean remains unclear. Here we investigated isoprene and monoterpenes secondary organic aerosol (SOAI and SOAM) tracers in three years of summer aerosol samples collected from the Arctic Ocean atmosphere. The results indicated that methyltetrols were the most abundant SOAI tracers, while the main oxidation products of monoterpenes varied over the years owing to different aerosol aging. The results of the principal component analysis (PCA)-generalized additive model (GAM) combined with correlation analysis suggested that SOAI tracers were mainly generated by the oxidation of isoprene from marine emissions, while SOAM tracers were probably more influenced by terrestrial transport. Estimation of secondary organic carbon (SOC) indicated that monoterpenes oxidation contributed more than isoprene and that sea ice changes had a relatively small effect on biogenic SOC concentration levels. Our study quantified the contribution of influencing factors to the atmospheric concentration of BSOA tracers in the Arctic Ocean, and showed that there were differences in the sources of precursors for different BSOA. Hence, our findings have contributed to a better understanding of the characteristics, sources and formation of SOA in the atmosphere of the Arctic Ocean.

The impact of the aerosol reduction on the worsening ozone pollution over the Beijing-Tianjin-Hebei region via influencing photolysis rates.

Due to the implementation of the toughest-ever emission control actions across China from 2013 to present, the aerosols are decreasing annually but ozone is simultaneously increasing, especially over the Beijing-Tianjin-Hebei (BTH) region, where ozone pollution can even spread into winter. Quantifying each impact of aerosols on ozone in all seasons is urgent for the worsening ozone pollution in the improved aerosol air quality. In this study, we focused on the impact of aerosols on ozone via influencing photolysis rates. The air pollutants were simulated over the Central East China (CEC) in 2018 by using the Weather Research and Forecasting with Chemistry (WRF-Chem) model. By implementing emissions with base years of 2014 and 2018, we quantified the increase in ozone (ΔOzone_photolysis) caused by the decreasing aerosol concentrations (ΔPM2.5) by influencing photolysis rates over the BTH region in all seasons. Furthermore, combined with the ozone observations, the contribution of ΔOzone_photolysis to the total changes in ozone (ΔOzone_total) in all seasons was quantitatively discussed. Our results showed that ΔPM2.5 showed obvious seasonal variations, which PM2.5 decreased more significantly in winter and autumn than in spring and summer, although significant reductions in anthropogenic emissions were observed in all seasons. Consistent seasonal variations were also observed in ΔOzone_photolysis, and the mean increases reached 5.5 µg m-3, 2.6 µg m-3, 1.2 µg m-3, and 1.4 µg m-3 in winter, autumn, spring, spring, and summer, respectively. Compared with ΔOzone_total, ΔOzone_photolysis accounted for 36.3%, 17.2%, 3.5% and 10.6% of ΔOzone_total in winter, autumn, spring, and summer, respectively, suggesting that ΔOzone_photolysis was not the primary contributor to the current changes in ozone over the BTH region. However, the 36.3% contribution to ΔOzone_total in winter suggested that ΔOzone_photolysis is still an important contributor and should not be ignored when discussing the formation of high ozone episodes occurring in winter.

Are Environmentally Friendly Fireworks Really "Green" for Air Quality? A Study from the 2019 National Day Fireworks Display in Shenzhen.

Fireworks are widely used around the world and can cause severe air pollution over a short period of time. Many efforts have been carried out worldwide to reduce the level of firework-generated air pollution, such as limiting the use of fireworks and developing environmentally friendly fireworks. Research has suggested that the use of environmentally friendly charges in fireworks can reduce emissions, although their impact on ambient air quality has not been quantified. Here, we used a chemical transport model to study the benefits of environmentally friendly fireworks in reducing ambient PM2.5 based on a detailed estimation of emissions from fireworks and dense observations available for simulation validation. Our results showed that environmentally friendly fireworks can reduce ambient PM2.5 by ∼50% (in the range of 15-65% with a "central" value of 35% considering uncertainties) compared with traditional fireworks. However, due to a large number of fireworks used, the air quality still significantly deteriorated, and the effect of using twice the amount of environmentally friendly fireworks on air quality would be comparable to the use of traditional fireworks. Our results indicate that environmentally friendly fireworks are not actually "green". To make them green, the total number of fireworks used at one time must be strictly restricted.

A Novel Method with Stacking Learning of Data-Driven Soft Sensors for Mud Concentration in a Cutter Suction Dredger.

The dredger construction environment is harsh, and the mud concentration meter can be damaged from time to time. To ensure that the dredger can continue construction operations when the mud concentration meter is damaged, the development of a dredger with advantages of low price and simple operation that can be used in emergency situations is essential. The characteristic spare mud concentration meter is particularly critical. In this study, a data-driven soft sensor method is proposed that can predict the mud concentration in real time and can mitigate current marine mud concentration meter malfunctions, which affects continuous construction. This sensor can also replace the mud concentration meter when the construction is stable, thereby extending its service life. The method is applied to two actual construction cases, and the results show that the stacking generalization (SG) model has a good prediction effect in the two cases, and its goodness of fit R2 values are as high as 0.9774 and 0.9919, indicating that this method can successfully detect the mud concentration.

Scanning vertical distributions of typical aerosols along the Yangtze River using elastic lidar.

In recent years, China has experienced heavy air pollution, especially haze caused by particulate matter (PM). The compositions, horizontal distributions, transport, and chemical formation mechanisms of PM and its precursors have been widely investigated in China based on near-ground measurements. However, the understanding of the distributions and physical and chemical processes of PM in the vertical direction remains limited. In this study, an elastic lidar was employed to investigate the vertical profiles of aerosols along the Yangtze River during the Yangtze River Campaign of winter 2015. Some typical aerosols were identified and some events were analyzed in three cases. Dust aerosols can be transported from the Gobi Desert to the Yangtze River basin across a long distance at both low and high altitudes in early December. The transport route was perpendicular to the ship track, suggesting that the dust aerosols may have affected a large area. Moreover, during transport, some dust was also affected by the areas below its transport route since some anthropogenic pollutants were mixed with the dust and changed some of its optical properties. Biomass-burning aerosols covering a distant range along the Yangtze River were identified. This result directly shows the impact areas of biomass-burning aerosols in some agricultural fields. Some directly emitted aerosol plumes were observed, and direct effects of such plumes were limited both temporally and spatially. In addition, an aerosol plume with very low linear depolarization ratios, probably formed through secondary processes, was also observed. These results can help us better understand aerosols in large spatial scales in China and can be useful to regional haze studies.

Use of 4,4'-dinitrostilbene-2,2'-disulfonic acid wastewater as a raw material for paramycin production.

This study uses 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS) wastewater to produce paramycin (4-amino-2-hydroxybenzoic acid), an antitubercular agent and important pharmaceutical intermediate. The high concentrations of aromatic sulfonic acids contained in the wastewater, derived from a DNS production facility, have been transformed to paramycin in yields of more than 85%. This waste-disposal strategy, which combines oxidation using NaClO, reduction using iron powder, and subsequent alkaline fusion with NaOH, has been proven to be successful in dealing with ton-scale DNS wastewater. Compared with common treatment methods, which usually involve degrading the compounds, this new method recycles most of the aromatic sulfonic acids in the wastewater to produce paramycin. This effectively solves the associated environment problems associated with DNS wastewater and is also potentially profitable. The present approach could also lead to alternative solutions for dealing with other industrial wastewaters generated from oxidative coupling reactions of nitro-substituted toluenes to the corresponding substituted stilbenes.