Effects of natural and anthropogenic emissions on the composition and toxicity of aerosols in the marine atmosphere.

The impacts of natural dimethyl sulfide (DMS) and ship emissions on marine environments and particulate matter (PM) over the western and southern sea areas around South Korea were studied based on field campaigns from August-September 2017 and May-June 2018 using the Community Multi-scale Air Quality v5.3.2 modeling system. DMS oxidation enhanced the concentrations of both sulfur dioxide (SO2) and sulfate (SO42-) in PM2.5 by 6.2-6.4% and 2.9-3.6%, respectively, in the marine atmosphere during the study period, whereas it slightly decreased nitrate (NO3-) concentrations (by -1.3%), compared to the simulation without DMS oxidation chemistry. Furthermore, ship emissions increased the concentrations of SO42-, NO3-, and NH4+ by 4.5%, 23%, and 7.3%, respectively. Methane sulfonic acid concentration was 0.17 µg m-3, suggesting the importance of the addition channel in the DMS oxidation pathway. The model simulation indicated that ship emissions in the target area contributed dominantly to non-sea-salt SO42-, and the marine DMS emission source was non-negligible. The geographical distribution of PM toxicity (aerosol oxidative potential) was assessed in the marine atmosphere during the study period.

Enhanced Methane Emissions during Amazonian Drought by Biomass Burning.

The Amazon is a significant source of atmospheric methane, but little is known about the source response to increasing drought severity and frequency. We investigated satellite observations of atmospheric column-averaged methane for the 2010 drought and subsequent 2011 wet year in the Amazon using an atmospheric inversion scheme. Our analysis indicates an increase in atmospheric methane over the southern Amazon region during the drought, representing an increase in annual emissions relative to the wet year. We attribute the increase to emissions from biomass burning driven by intense drought, combined with carbon monoxide showing seasonal variations corresponding to methane variations. We show that there is probably a strong correspondence between drought and methane emissions in the Amazon.