Measurements of size-fractionated concentration and bulk dry deposition of atmospheric particulate bound mercury

• Published in: Atmospheric environment (1994) 2012-12, Vol.61, p.371-377
• Main Authors: Fang, G.C., Zhang, L., Huang, C.S.
• Format: Article
• Language: English
• Subjects: Applied sciences; atmospheric chemistry; Atmospheric mercury; Atmospheric pollution; Central Taiwan; Deposition velocity; Dry deposition; emissions; Exact sciences and technology; Fine/coarse fraction; mercury; Particle size distribution; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Surrogate surface measurements; traffic; wetlands
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2012.07.052

Daily samples of size-fractionated (18, 10, 2.5 and 1.0 μm) particulate-bound mercury Hg(p) were collected using Micro-Orifice Uniform Deposition Impactors (MOUDI), on randomly selected days each month between November 2010 and July 2011, at a traffic site (Hungkuang), a wetland site (Gaomei), and an industrial site (Quanxing) in central Taiwan. Bulk dry deposition was also collected simultaneously using a surrogate surface. The nine-month average (±standard deviation) Hg(p) concentrations were 0.57 (±0.90), 0.17 (±0.27), and 0.94 (±0.92) ng m−3 at Hungkuang, Gaomei, and Quanxing, respectively. Concentrations in November and December were much higher than in the other months due to a combination of high local emissions and meteorological conditions. PM1.0 contributed more than 50% to the bulk concentration at the traffic and the industrial sites, but only contributed 25% at the wetland site. PM1.0–2.5 contributed 25%–50%, depending on location, to the bulk mass. Coarse fraction (PM2.5–18) contributed 7% at Hungkuang, 25% at Gaomei, and 19% at Quanxing. Samples with very high bulk concentrations had large fine fractions. Annual dry deposition estimated from the surrogate surface measurements was in the range of 30–85 μg m−2 yr−1 at the three sites. Coarse particulate Hg(p) were estimated to contribute 50–85% of the total Hg(p) dry deposition. Daily dry deposition velocities (Vd) ranged from 0.01 to 7.7 cm s−1. The annual Vd generated from the total measured fluxes was 0.34, 0.60 and 0.29 cm s−1 at Hungkuang, Gaomei, and Quanxing, respectively. These values can be reasonably reproduced using a size-resolved model and measured size fractions. ► Highest concentrations for ambient particulate mercury (Hg(p)) were observed in early winter. ► PM1.0 and PM1.0–2.5 dominated the bulk Hg(p) concentration. ► Coarse Hg(p) contributed 7–25% of the bulk Hg(p) concentration. ► Coarse Hg(p) contributed 50–85% of the total Hg(p) dry deposition. ► Dry deposition velocity of Hg(p) was mostly in the range of 0.1–0.8 cm s−1.