Bridge-based sensing of NO x and SO 2 emissions from ocean-going ships Daniel A. Burgard * , Carmen R.M. Bria 1 Department of Chemistry, University of Puget Sound, Tacoma, WA 98416, USA highlights graphical abstract  Measured NO x and SO 2 emissions from in-use ocean-going ships.  First emission measurements from individually identified in-use cruise ships.  Demonstration of a remote sensor that can estimate sulfur content in fuels from ships. article info Article history: Received 14 January 2016 Received in revised form 7 April 2016 Accepted 11 April 2016 Available online 12 April 2016 Keywords: Remote sensing Ship emissions NO x Sulfur dioxide Spectroscopy Cruise ships abstract As emissions from nonroad mobile sources face increased regulatory scrutiny, a surprisingly few number of real-world, in-use measurements exist for these sources. This paper reports the first use of an open- path Remote Sensing Device (RSD) to measure emissions from ocean-going ships, including cruise ships. This noninvasive technique measured NO x and SO 2 emission factors from 16 individually identified ocean-going ships as they passed under the Lions Gate Bridge in Vancouver, B.C. and their exhaust plumes passed through the sensing beam of the RSD on a bridge directly above. Ship NO x emissions generally agreed with previous studies showing no emissions trends across vessel type. Ship SO 2 emissions were reasonable based on expected Environmental Control Area fuel sulfur requirements and corresponded to 0.4e2.4% sulfur in the fuels. This method's specificity of individual vessel SO 2 mea- surements suggests that this technique could be used as a tool to detect high sulfur fuel use in vessels. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. Background In the 10 year period between 1996 and 2006, on-road gasoline vehicles went from being the largest single mobile source of oxides of nitrogen (NO x ) emissions to being nearly halved and roughly equal to the sum of the nonroad diesel sources (Dallmann and Harley, 2010). On-road mobile sources have been strictly regu- lated, requiring advanced emissions control technologies and leading to significantly reduced emissions (Bishop and Stedman, 2008). Nonroad diesel sources such as construction equipment, locomotives, and marine vessels, attracted little regulatory atten- tion during that same period. On-road emissions are also well characterized leading to a better understanding of their * Corresponding author. E-mail address: dburgard@pugetsound.edu (D.A. Burgard). 1 Present address: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO, USA. Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv http://dx.doi.org/10.1016/j.atmosenv.2016.04.014 1352-2310/© 2016 Elsevier Ltd. All rights reserved. Atmospheric Environment 136 (2016) 54e60