Chemical Characteristics of Marine Fine Aerosols over Sea and at Offshore Islands during Three Cruise Sampling Campaigns in the Taiwan Strait– Sea Salts and Anthropogenic Particles

Abstract

Marine fine aerosols were simultaneously collected over sea and at offshore islands during three cruise sampling campaigns to investigate the spatial distribution of atmospheric fine particles (PM<sub>2.5</sub>) and the influences of sea salts and anthropogenic particles on the chemical characteristics of PM<sub>2.5</sub> in the Taiwan Strait. Field sampling results indicated that PM<sub>2.5</sub> concentrations over sea were generally higher than those at the offshore islands, while the PM<sub>2.5</sub> concentrations in the daytime were commonly higher than those at nighttime. Moreover, the concentrations of PM<sub>2.5</sub> were generally higher than those of coarse particles (PM<sub>2.5–10</sub>) with an exception of the winter cruise in 2014. Moreover, sea salts accounted for 6.5–11.1 % and 11.0–13.5 % of PM<sub>2.5</sub> at the offshore islands and over sea, respectively. The contributions of non-sea salt-water soluble ions (nss-WSI) to PM<sub>2.5</sub> at the offshore islands were obviously higher than those over sea, while the contributions of ss-WSI for PM<sub>2.5</sub> at the offshore islands were much lower than those over sea during the cruise sampling campaigns. Anthropogenic metallic elements including Zn, Mn, Pb, Cr, and Ni had higher concentrations over sea than those at the offshore islands, suggesting that PM<sub>2.5</sub> was not only influenced by marine aerosols but also by anthropogenic particles originated from human activities such as industrial processing, fuel burning, and vehicular and shipping exhausts. Higher mass ratios of Ni/Al and Ni/Fe over sea than those at the offshore islands suggested that shipping emissions had higher influences on marine fine particles than crustal dusts in open sea while compared to those at the offshore islands. The carbonaceous contents of PM<sub>2.5</sub> indicated that the concentrations of organic carbons (OC) were generally higher than those of elemental carbons (EC). The higher mass ratios of organic and elemental carbons (OC/EC) were observed at the central and north Taiwan Strait, and follow by the offshore islands and the south Taiwan Strait. Overall, sea salts and anthropogenic particles had significant influences on the chemical composition of PM<sub>2.5</sub> over sea and at the offshore islands.

Air quality in the middle and lower reaches of the Yangtze River channel: a cruise campaign

“…Figure S9 presents the variation in levoglucosan / OC ratio along the Yangtze River. The ratio of levoglucosan / OC during this cruise ranged from 0.03 % to 0.91 % with an average of 0.35±0.24 %, which was comparable to that of Lin'an in the YRD region (Liang et al, 2017). However, the ratio of levoglucosan / OC during the YRC was near an order of magnitude lower than its value in New Delhi (3.1 ± 0.8 %) and Lumbini (3.34±2.53 %) on the northern edge of the Indo-Gangetic Plain (Wan et al, 2017), where BB plays an important role in air quality.…”

“…Numerous studies have also confirmed that levoglucosan mostly originates from BB (Liang et al, 2017;Wan et al, 2017;Wang et al, 2014). The distribution of levoglucosan is irregularly parabolic from inland to coastal areas in Fig.…”

“…4) was much higher than 1.17 (ratio of seawater), suggesting that anthropogenic sources, including BB and coal combustion, contributed to the excessive Cl − in China cities (C. Zhang et al, 2013). The concentration of levoglucosan, a BB tracer, ranged from 0.015 to 0.18 µg m −3 with a mean value of 0.075 ± 0.047 µg m −3 , much higher than the average concentration of 0.0394 µg m −3 in Lin'an (30.3 • N, 119.73 • E) (a rural site in the YRD region) (Liang et al, 2017), indicating that BB was also a major contributor to PM 2.5 during the YRC.…”

Reply to Reviewers

“…Figure S9 presents the variation in levoglucosan / OC ratio along the Yangtze River. The ratio of levoglucosan / OC during this cruise ranged from 0.03 % to 0.91 % with an average of 0.35±0.24 %, which was comparable to that of Lin'an in the YRD region (Liang et al, 2017). However, the ratio of levoglucosan / OC during the YRC was near an order of magnitude lower than its value in New Delhi (3.1 ± 0.8 %) (Li et al, 2014) and Lumbini (3.34±2.53 %) on the northern edge of the Indo-Gangetic Plain (Wan et al, 2017), where BB plays an important role in air quality.…”

Physico-chemical characterization of urban aerosols from specific combustion sources in West Africaat Abidjan in Côte d’Ivoire and Cotonou in Benin in the frame of DACCIWA program

“…The concentrations of magnesium (Mg 2+ ) are low, ranging from 0.5 to 1.1 μg.m -3 (3.6-3.8%), and are as high as the sum of the remaining species (oxalic, formic and acetic), constituting 2.1-7.2% of the total ion mass at the ADF site. Chloride is most likely associated with sea salt origin (55% of total composition of the sea water) or secondary aerosol production (Li et al, 2016). Its highest concentration at the ADF site remains lower than the typical concentration in sea water, suggesting a secondary production source.…”