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Abstract
We present a novel source attribution approach that incorporates satellite data into GEOS-Chem adjoint simulations to characterize the species-specific, regional, and sectoral contributions of daily emissions for 3 air pollutants: fine particulate matter (PM2.5), ozone (O3), and nitrogen dioxide (NO2). This approach is implemented for Washington, DC, first for 2011, to identify urban pollution sources, and again for 2016, to examine the pollution response to changes in anthropogenic emissions. In 2011, anthropogenic emissions contributed an estimated 263 (uncertainty: 130–444) PM2.5- and O3-attributable premature deaths and 1,120 (391–1795) NO2 attributable new pediatric asthma cases in DC. PM2.5 exposure was responsible for 90% of these premature deaths. On-road vehicle emissions contributed 51% of NO2-attributable new asthma cases and 23% of pollution-attributable premature deaths, making it the largest contributing individual sector to DC’s air pollution–related health burden. Regional emissions, originating from Maryland, Virginia, and Pennsylvania, were the most responsible for pollution-related health impacts in DC, contributing 57% of premature deaths impacts and 89% of asthma cases. Emissions from distant states contributed 34% more to PM2.5 exposure in the wintertime than in the summertime, occurring in parallel with strong wintertime westerlies and a reduced photochemical sink. Emission reductions between 2011 and 2016 resulted in health benefits of 76 (28–149) fewer pollution-attributable premature deaths and 227 (2–617) fewer NO2-attributable pediatric asthma cases. The largest sectors contributing to decreases in pollution-related premature deaths were energy generation units (26%) and on-road vehicles (20%). Decreases in NO2-attributable pediatric asthma cases were mostly due to emission reductions from on-road vehicles (63%). Emission reductions from energy generation units were found to impact PM2.5 more than O3, while on-road vehicle emission reductions impacted O3 proportionally more than PM2.5. This novel method is capable of capturing the sources of urban pollution at fine spatial and temporal scales and is applicable to many urban environments, globally.
Highlights
Marine microorganisms are integral to major biogeochemical cycles, fluxes, and other processes occurring in marine systems (Glockner et al, 2012)
The results from this study provide novel insight into the microbially mediated fates of DMSP under heightened pCO2 derived from 35S-DMSP radio-isotopic uptake assays
A natural plankton community sourced from the surface waters of the SLE during summer 2013 was exposed to three initial pCO2 targets, corresponding to single (775 matm), double (1,850 matm), and triple pCO2 (2,700 matm)
Summary
Marine microorganisms are integral to major biogeochemical cycles, fluxes, and other processes occurring in marine systems (Glockner et al, 2012). Beyond the several DMSP-dependent DMS-releasing (Dddþ) enzymes that have been isolated in populations of heterotrophic bacteria, one family of DMSP-lyase, dubbed Alma, has been identified in eukaryotes, such as Emiliania huxleyi and species of Symbiodinium, displaying the potential for direct production of DMS by phytoplankton (Todd et al, 2007; Alcolombri et al, 2015; Johnston et al, 2016). To this day, the relative importance of autotrophic and heterotrophic processes in supplying stocks of DMS in seawater remains unclear, with provisional estimates fluctuating extensively (Lizotte et al, 2012). As a result of the intrinsic coupling between microorganisms and the cycling of marine methylated compounds, ongoing and future disturbances in oceanic ecosystems related to anthropogenic forcing that may affect marine microbes may impact the dynamics of the climate-relevant compound DMS
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