Quantification for photochemical loss of volatile organic compounds upon ozone formation chemistry at an industrial city (Zibo) in North China Plain.

Volatile organic compounds (VOCs) are consumed by photochemical reactions during transport, leading to inaccuracies in estimating the local ozone (O3) formation mechanism and its subsequent strategy for O3 attainment. To comprehensively quantify the deviations in O3 formation mechanism by consumed VOCs (C-VOCs), a 5-month field campaign was conducted in a typical industrial city in Northern China over incorporating a 0-D box model (implemented with MCMv3.3.1). The averaged C-VOCs concentration was 6.8 ppbv during entire period, and Alkenes accounted for 62% dominantly. Without considering C-VOCs, the relative incremental reactivity (RIR) of anthropogenic VOCs (AVOC, overestimated by 68%-75%) and NOx (underestimated by 137%-527%) demonstrated deviations at multiple scenarios, and the RIR deviations for precursors in High-O3-periods (HOP) were lower than Low-O3-periods (LOP). The RIR deviations from individual species involved C-VOCs calculation did not impact the identification for the high-ranking-RIR AVOC species but non-negligible. Monthly comparisons showed that higher C-VOCs concentrations would lead to higher RIR deviations. The daily maximum of net Ox production rate (P(Ox)) and the regional transport Ox (Trans(Ox)) without C-VOCs were underestimated by 56%-194% and 81%-243%, respectively. After considering C-VOCs, the contribution of HO2+NO for Ox gross production (G(Ox)) decreased by 7% (LOP) and 7% (HOP), but OH + NO2 for Ox destruction (D(Ox)) decreased by 16% (LOP) and 23% (HOP), and alkenes + O3 increased for D(Ox) by 12% (LOP) and 22% (HOP). This implies that VOCs-NOx-O3 sensitivity was deviated between with/without C-VOCs, and severe O3 pollution rendered deviations in O3 formation, especially via NOx-driving chemistry. Based on RIR(NOx)/RIR(AVOC) with/without C-VOCs, the sensitivity regime shifted from VOCs-limited (-0.93) to transition (1.38) at LOP, and from VOCs-limited (0.19) to NOx-limited (3.79) at HOP. Our results reflected that the NOx limitation degree was underestimated without constraint C-VOCs, especially HOP, and provided implication to more precise O3 pollution control strategies.

[Photochemical Mechanism and Control Strategy Optimization for Summertime Ozone Pollution in Yining City].

To explore the formation mechanism of the ozone （O3） and emission reduction strategy in a northwestern city， an extensive field campaign was conducted in summertime in 2021 in Yining City， in which the 0-D box model incorporating the latest explicit chemical mechanism （MCMv3.3.1） was applied for the first time to quantify the O3-NOx-VOCs sensitivity and formulate a precise O3 control strategy in this city. The results showed that： ① the three indicators ï¼»i.e.， O3 formation potential （OFP）， ·OH reaction rate （k·OH）， and relative incremental reactivity （RIR）］ jointly indicated that alkenes， oxygenated volatile organic compounds （OVOCs）， and aromatics were the highest contributors among anthropogenic volatile organic compounds （AVOC） to O3 formation， and the contribution of biogenic volatile organic compounds （BVOC） also could not be ignored. Additionally， the results based on RIR calculation implied that that the acetaldehyde， ethylene， and propylene were the most sensitive individual VOCs species in Yining City. ② The in-situ photochemical O3 variations were primarily influenced by the local photochemical production and export process horizontally to downwind areas or vertically to the upper layer， and the reaction pathways of HO2·+ NO and ·OH + NO2 contributed the most to the gross Ox photochemical production （60%） and photochemical destruction production （53%）， respectively. Hence， the reduction in local emissions for O3 precursors was more essential to alleviate O3 pollution in this city. ③ The outcome based on RIR（NOx） / RIR（AVOC） and EKMA jointly suggested that the photochemical regime in this city can be considered a transitional regime that was also nearly a VOCs-limited regime. Detailed mechanism modeling based on multiple scenarios further suggested that the NOx and VOCs synergic emission reduction strategies was helpful to alleviate O3 pollution. These results are useful to provide policy-related guidance for other cities facing similar O3 pollution in northwest China.

Potential source and health risks of black carbon based on MERRA-2 reanalysis data in a typical industrial city of North China Plain.

Black carbon (BC) significantly affects climate, environmental quality, and human health. This study utilised Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), which can compensate for the shortcomings of ground BC monitoring in spatial-temporal distribution to study the pollution characteristics of BC and potential pollution sources in a typical industrial city (Xinxiang) with serious air pollution in northern China. The results showed that average daily ground observation and MERRA-2 concentration of BC of 7.33 µg m-3 and 9.52 µg m-3. The mean BC concentration derived from MERRA-2 reanalysis data was higher than ground measurement due to resolution limitations and pollution from the northern regions. The reliability of the MERRA-2 data was confirmed through correlation analysis. Consideration of the spatial distribution of BC from MERRA-2 and incorporating the potential source contribution function (PSCF), concentration-weighted trajectory (CWT), and emission inventory, other possible source areas and primary sources of BC in Xinxiang were investigated. The results indicated that implementing transportation and residential emission control measures in Henan Province and its surrounding provinces, such as Hebei Province, will effectively decrease the BC level in Xinxiang City. A passively smoked cigarettes model was used to evaluate the risk of BC exposure. The percentage of lung function decrement (PLFD) was the highest in school-age children, while the impact on lung cancer (LC) health risk was comparatively lower. Notably, the BC health risk in Xinxiang was lower than in most cities across Asia.