To address and remediate severe particulate matter (PM) pollution in the North China Plain (NCP), many studies have traced pollution sources by using fixed air quality monitoring stations. However, these fixed monitors have high maintenance costs that make it economically infeasible to construct spatially dense networks for air quality measurement. Alternatively, using satellite monitoring systems and a low-cost air quality sensor network can greatly increase the spatiotemporal resolution of the ground-level PM concentration data for a given region. This study comprehensively examines the performance of China's EPA monitoring stations (CN-EPA), low-cost PM sensor networks and satellite aerosol optical depth (AOD) measurements. The goal is to improve the spatiotemporal resolution of ground-level PM concentration data for Xinxiang, a typical industrial city in the NCP. The inferred results show that low-cost PM sensors demonstrate high linearity with CN-EPA data sets for PM 2.5 concentrations with an R 2 value of 0.82. The PM 2.5 concentration inferred from the AOD retrievals demonstrates a moderate correlation with fixed monitoring stations with an R 2 value of 0.53. To evaluate the impact of human activities on air pollution, four traditional Chinese festivals, Chinese New Year, Tomb Sweeping Day, Ghost Festival, and Moon Festival, are chosen to observe the PM distribution in Xinxiang. Heat-maps of the ground-level PM 2.5 concentration reveal pollution hotspots in areas of high population density. Cross-validation is employed to evaluate the accuracy of the created pollution maps. The results demonstrate that pollution maps that were interpolated from data measured by CN-EPA data sets have the smallest root mean squared error (RMSE). Finally, our results show that low-cost PM sensor data can be integrated with traditional fixed air quality measurements to provide more detailed information about emission sources on pollution maps in urban and rural areas.

We measured submicron aerosols (PM1) at a beachfront site in Texas in Spring 2021 to characterize the “background” aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine “background” aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM1 mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf “background” aerosols were much more polluted; the average non-refractory (NR-) PM1 mass concentration was 3–70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured “background” sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Abstract. As criteria pollutants from anthropogenic emissions have declined in the US in the last two decades, biomass burning (BB) emissions are becoming more important for urban air quality. Tracking the transported BB emissions and their impacts is challenging, especially in areas that are also burdened by anthropogenic sources like the Texas Gulf coast. During the Corpus Christi and San Antonio (CCSA) field campaign in Spring 2021, two long-range transport BB events (BB1 and BB2) were identified. The observed patterns of absorption Ångström Exponent (AAE), high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) BB tracer (f60), equivalent black carbon (eBC), acetonitrile and carbon monoxide (CO) during BB1 and BB2 indicated differences in the mixing of transported BB plumes with local anthropogenic sources. The combined information from HYSPLIT backward trajectory (BTs) and satellite observations revealed that BB1 had mixed influence of transported smoke plumes from fires in Central Mexico, the Yucatan peninsula, and the Central US, whereas BB2 was influenced majorly by fires in the Central US. The estimated transport time of smoke from the Mexican fires and the Central US fires to our study site were not too different (48–54 hours and 24–36 hours, respectively) and both events appeared to have undergone similar levels of atmospheric processing, as evident in the elemental ratios of bulk organic aerosol (OA). We observed a progression of f44 vs. f60 as a function of time elapsed during BB2. Positive matrix factorization (PMF) analysis of OA showed that BB1 had a mixture of organics from aged BB emission with an anthropogenic marine signal while the oxidized organic compounds from aged BB emissions dominated the aerosols during BB2. While aerosol measurements exhibited good agreement with respect to the BB designation, the CO and acetonitrile trends revealed more complicated source contributions. Our analysis from mobile and stationary measurements highlights that both CO and acetonitrile are likely impacted by local sources even during the BB events and specifically that acetonitrile cannot be used as a unique BB tracer for dilute BB plumes in an industrially influenced location. Finally, we provide evidence of the potential regional impacts of these transported BB events on urban O3 levels using measurements from the surface air quality monitoring network in Texas.