ABSTRACT
International shipping's particulate matter primary emissions have a share in global anthropogenic emissions of between 3% and 4%. Ship emissions of volatile organic compounds (VOCs) can play an important role in the formation of fine particulate matter. Using an aerosol box model for the near-plume scale, this study investigated how the changing VOC emission factor (EF) for ship engines impacts the formation of secondary PM2.5 in ship exhaust plumes that were detected during a measurement campaign. The agreement between measured and modeled particle number size distribution was improved by adjusting VOC emissions, in particular of intermediate-, low-, and extremely low-volatility compounds. The scaling of the VOC emission factor showed that the initial emission factor, based on literature data, had to be multiplied by 3.6 for all VOCs. Information obtained from the box model was integrated into a regional-scale chemistry transport model (CTM) to study the influence of changed VOC ship emissions over the Mediterranean Sea. The regional-scale CTM run with adjusted ship emissions indicated a change in PM2.5 of up to 5% at the main shipping routes and harbor cities in summer. Nevertheless, overall changes due to a change in the VOC EF were rather small, indicating that the size of grid cells in CTMs leads to a fast dilution.
ABSTRACT
Long-term monitoring of data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (http://www.gmos.eu) and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere as well as in the lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010-2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.
ABSTRACT
PURPOSE: To assess the efficacy and safety of portal vein (PV) embolization versus hepatic artery embolization (HAE) for induction of hepatic hypertrophy before extended right hemihepatectomy in patients with hilar cholangiocarcinoma. MATERIALS AND METHODS: Fifty patients (female, n = 15; male, n = 35; age range, 37-80 y) with hilar cholangiocarcinomas who were planned to undergo extended right hemihepatectomy were prospectively included in 2003-2006. In addition to biliary decompression of the left liver, patients were randomized to undergo embolization of the right hepatic artery (with transfemoral access and polyvinyl alcohol [PVA] particles plus coils) or right PV branches (with computed tomography [CT]-guided transhepatic access and PVA particles). CT was performed before and approximately 3 weeks after embolization for volumetric assessment of the liver. RESULTS: In the HAE group, median growth of the left lateral segments was 40 mL (P < .01), with a median reduction of the whole liver of 10 mL (P = .41); adverse events were observed in two of 25 patients (8%), who each developed an abscess in the right liver lobe. In the PV embolization group, median growth of the left lateral segments was 110 mL (P < .01), with a median growth of the whole liver of 10 mL (P = .92); a subcapsular seroma occurred in one of 25 patients (4%). The median growth of the left lateral segments after PV embolization was significantly greater than after HAE (P = .004). CONCLUSIONS: Compared with HAE, PV embolization was significantly superior regarding induction of hepatic hypertrophy of the left lateral segments.