title: Do rainfalls wash out anthropogenic airborne magnetic particulates?
abstract: We separated dust particles from the mesh-filtered sets of rainwaters collected on rainy days with daily precipitations exceeding 10 mm per day. A total of 136 rainwaters (or snow during the winter season) samples collected from February 2009 to February 2013 were analyzed. In particular, 33 out of 136 rainwaters were collected during or just after the Asian dust storm (ADS) events. Values of pH were relatively higher during warmer seasons. During ADS events, precipitations were alkaline, possibly due to abundant supply of alkaline minerals from the deserts source area to the precipitation. Compositional analysis on particulate matter (PM) indicated that Fe (and Al, K, and Mg) enriched the dusts collected during ADS, with respect to events than those without ADS. We found that ADS rainfall events are effective in selectively eliminating dust particles. However, high rainfall does not necessarily indicate more dilution of dusts. On microscopic examination, we observed natural soils, natural dust of pedogenesis or weathering origin, anthropogenic C-Fe-rich particles, and anthropogenic C-rich particles. Because of its small size, the stoichiometry of ADS-related, Fe-rich dust particles was inferred from the magnetic analysis. Presence of Verwey transition near 100-120 K and experimental determination of Curie points near 580 °C indicate that magnetic mineral responsible for the magnetic properties of ADS-related dusts was magnetite.
authors.affiliation: Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon, 34134, South Korea.
authors.forename: Amarjargal
authors.initials: A
authors.lastname: Baatar
authors.affiliation: Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon, 34134, South Korea.
authors.forename: Raegyung
authors.initials: R
authors.lastname: Ha
authors.affiliation: Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon, 34134, South Korea. yongjaeyu@cnu.ac.kr.
authors.forename: Yongjae
authors.identifier: http://orcid.org/0000-0002-2005-2778
authors.initials: Y
authors.lastname: Yu
mesh_terms: D000393:Air Pollutants; D004391:Dust; D004784:Environmental Monitoring; D008903:Minerals; D010316:Particle Size; D052638:Particulate Matter
chemical_list: D000393:Air Pollutants; D004391:Dust; D008903:Minerals; D052638:Particulate Matter
keywords: Anthropogenic pollutions; Asian dust storms; Heavy metals; Magnetic material; Monthly variation; Particle size; Precipitation; Rainfalls