Dramatic increase in reactive volatile organic compound (VOC) emissions from ships at berth after implementing the fuel switch policy in the Pearl River Delta Emission Control Area

Abstract

Abstract. Limiting fuel sulfur content (FSC) is a widely adopted approach for reducing ship emissions of sulfur dioxide (SO2) and particulate matter (PM), particularly in emission control areas (ECAs), but its impact on the emissions of volatile organic compounds (VOCs) is still not well understood. In this study, emissions from ships at berth in Guangzhou, southern China, were characterized before and after the implementation of the fuel switch policy (IFSP) with an FSC limit of 0.5 % in the Pearl River Delta ECA (ECA-PRD). After IFSP, the emission factors (EFs) of SO2 and PM2.5 for the coastal vessels decreased by 78 % and 56 % on average, respectively; however, the EFs of the VOCs were 1807±1746 mg kg−1, approximately 15 times that of 118±56.1 mg kg−1 before IFSP. This dramatic increase in the emissions of the VOCs might have been largely due to the replacement of high-sulfur residual fuel oil with low-sulfur diesel or heavy oils, which are typically richer in short-chain hydrocarbons. Moreover, reactive alkenes surpassed alkanes to become the dominant group among the VOCs, and low-carbon-number VOCs, such as ethylene, propene and isobutane, became the dominant species after IFSP. As a result of the largely elevated EFs of the reactive alkenes and aromatics after IFSP, the emitted VOCs per kilogram of fuel burned had nearly 29 times greater ozone formation potential (OFP) and approximately 2 times greater secondary organic aerosol formation potential (SOAFP) than those before IFSP. Unlike the coastal vessels, the river vessels in the region used diesel fuels consistently and were not affected by the fuel switch policy, but the EFs of their VOCs were 90 % greater than those of the coastal vessels after IFSP, with approximately 120 % greater fuel-based OFP and 70 %–140 % greater SOAFP. The results from this study suggest that while the fuel switch policy could effectively reduce SO2 and PM emissions, and thus help control PM2.5 pollution, it will also lead to greater emissions of reactive VOCs, which may threaten ozone pollution control in harbor cities. This change for coastal or ocean-going vessels, in addition to the large amounts of reactive VOCs from the river vessels, raises regulatory concerns for ship emissions of reactive VOCs.

Effects of marine fuel sulfur restrictions on particle number concentrations and size distributions in ship plumes in the Baltic Sea

“…PNC pl values attained in this work are similar to the concentrations of plumes observed in similar studies: median PNC values of 700 and 1470 cm −3 were measured during winter and summertime in southern Sweden, respectively (Ausmeel et al, 2019). A noticeably higher PNC concentration (2100 cm −3 ) of ship plumes was measured with airborne measurements right over the shipping lane in the southern Baltic Sea by Zanatta et al (2020) during the 0.10 m/m% FSC restriction. Concentrations observed by Zanatta et al (2020) were likely higher due to the fresher plumes (plume age ∼ 200-800 s).…”

“…This variation in the GMD from a minimum of 36, 39, and 31 nm to a maximum of 58, 55, and 51 nm for the FSC restrictions of 1.50 m/m%, 1.00 m/m%, and 0.10 m/m%, respectively, implies that particles either grow significantly or small particles evaporate when they are transported in the atmosphere. Zanatta et al (2020) found a similar behavior: increasing particle size as the age of the plumes increased. The atmospheric processing of plume particles is discussed more in Sect.…”

“…A noticeably higher PNC concentration (2100 cm −3 ) of ship plumes was measured with airborne measurements right over the shipping lane in the southern Baltic Sea by Zanatta et al (2020) during the 0.10 m/m% FSC restriction. Concentrations observed by Zanatta et al (2020) were likely higher due to the fresher plumes (plume age ∼ 200-800 s). Moreover, the small sample size (only nine continuous periods of single or multiple exhaust plumes, each lasting a couple of minutes at maximum) might cause statistical uncertainty in the results.…”

“…The reduction in PM 2.5 emissions from shipping has been estimated to reduce the negative health effects (Barregard et al, 2019;Chen et al, 2019;Partanen et al, 2013;Sofiev et al, 2018). In multiple studies, shipping has also been reported to be a significant contributor to atmospheric particle number concentrations (PNCs) both in the sea and in coastal areas, especially in the ultrafine size range (Ausmeel et al, 2019;Gobbi et al, 2020;Karl et al, 2020;Kivekäs et al, 2014;Kukkonen et al, 2016;Zanatta et al, 2020). The atmospheric PNC has been considered to S. D. Seppälä et al: Effects of marine fuel sulfur restrictions cause significant negative health effects, such as airway inflammation, impaired lung function, and cardiovascular mortality (Hennig et al, 2018;Strak et al, 2012).…”

“…Sulfate and OM concentrations have both been reported to be dependent on FSC (Lack et al, 2009). Furthermore, the emission factors (EFs) of SO 2 and organic carbon (OC) have been observed to decrease when fuels with lower FSC are used (Wu et al, 2020). In the study of Celik et al (2020), OM was twice as large for fuels with an FSC of 2.5 m/m% (mass per mass percentage) compared with an FSC of 0.5 m/m%.…”