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Cross-boundary transport of air pollution is a difficult issue in pollution control for the North China Plain. In this study, an industrial district (Shahe City) with a large glass manufacturing sector was investigated to clarify the relative contribution of fine particulate matter (PM 2.5 ) to the city's high levels of pollution. The Nest Air Quality Prediction Model System (NAQPMS), paired with Weather Research and Forecasting (WRF), was adopted and applied with a spatial resolution of 5 km. During the study period, the mean mass concentrations of PM 2.5 , SO 2 , and NO 2 were observed to be 132.0, 76.1, and 55.5 μg/m 3 , respectively. The model reproduced the variations in pollutant concentrations in Shahe at an acceptable level. The simulation of online source-tagging revealed that pollutants emitted within a 50-km radius of downtown Shahe contributed 63.4% of the city's total PM 2.5 concentration. This contribution increased to 73.9±21.2% when unfavorable meteorological conditions (high relative humidity, weak wind, and low planetary boundary layer height) were present; such conditions are more frequently associated with severe pollution (PM 2.5 ≥ 250 μg/m 3 ). The contribution from Shahe was 52.3±21.6%. The source apportionment results showed that industry (47%), transportation (10%), power (17%), and residential (26%) sectors were the most important sources of PM 2.5 in Shahe. The glass factories (where chimney stack heights were normally < 70 m) in Shahe contributed 32.1% of the total PM 2.5 concentration in Shahe. With an increase in PM 2.5 concentration, the emissions from glass factories accumulated vertically and narrowed horizontally. At times when pollution levels were severe, the horizontally influenced area mainly covered Shahe. Furthermore, sensitivity tests indicated that reducing emissions by 20%, 40%, and 60% could lead to a decrease in the mass concentration of PM 2.5 of of 12.0%, 23.8%, and 35.5%, respectively., (Copyright © 2021. Published by Elsevier B.V.)

The region along the Taihang Mountains in the North China Plain (NCP) is characterized by serious fine particle pollution. To clarify the formation mechanism and controlling factors, an observational study was conducted to investigate the physical and chemical properties of the fine particulate matter in Jiaozuo city, China. Mass concentrations of the water-soluble ions (WSIs) in PM 2.5 and gaseous pollutant precursors were measured on an hourly basis from December 1, 2017, to February 27, 2018. The positive matrix factorization (PMF) method and the FLEXible PARTicle (FLEXPART) model were employed to identify the sources of PM 2.5 . The results showed that the average mass concentration of PM 2.5 was 111 μg/m 3 during the observation period. Among the major WSIs, sulfate, nitrate, and ammonium (SNA) constituted 62% of the total PM 2.5 mass, and NO 3 - ranked the highest with an average contribution of 24.6%. NH 4 + was abundant in most cases in Jiaozuo. According to chemical balance analysis, SO 4 2- , NO 3 - , and Cl - might be present in the form of (NH 4 ) 2 SO 4 , NH 4 NO 3 , NH 4 Cl, and KCl. The liquid-phase oxidation of SO 2 and NO 2 was severe during the haze period. The relative humidity and pH were the key factors influencing SO 4 2- formation. We found that NO 3 - mainly stemmed from homogeneous gas-phase reactions in the daytime and originated from the hydrolysis of N 2 O 5 in the nighttime, which was inconsistent with previous studies. The PMF model identified five sources of PM 2.5 : secondary origin (37.8%), vehicular emissions (34.7%), biomass burning (11.5%), coal combustion (9.4%), and crustal dust (6.6%)., (Copyright © 2020. Published by Elsevier B.V.)