Abstract
Abstract. Mixing of Asian mineral dust with anthropogenic pollutants allows pollutants (e.g. sulfate and nitrate) to be transported over longer distances (e.g. to the northern Pacific, even to North America) along with dust particles. This mixing therefore affects the atmospheric and oceanic environment at local, regional and even continental scales. In this study, we used a three-dimensional regional chemical transport model (Nested Air Quality Predicting Modeling System, NAQPMS) to examine the degree of mixing between Asian mineral dust and anthropogenic pollutants in a super-duststorm event during 19–22 March 2010. Influences of the mixing processes on regional atmospheric environmental and oceanic biogeochemical cycles were also investigated. A comparison with measurements showed that the model reproduced well the trajectory of long-range dust transport, the vertical dust profile, and the chemical evolution of dust particles. We found that along-path mixing processes during the long-range transport of Asian dust led to increasingly polluted particles. As a result, ~60% of the sulfate and 70–95% of the nitrate in the downwind regions was derived from active mixing processes of minerals with pollutants sourced from the North China Plain and enhanced by transport over South China. This mixing had a significant impact on the regional-scale atmospheric composition and oceanic biogeochemical cycle. Surface HNO3, SO2 and O3 were decreased by up to 90%, 40% and 30%, respectively, due to the heterogeneous reactions on dust particles. Fe solubility rose from ~0.5% in the Gobi region to ~3–5% in the northwestern Pacific, resulting from oxidization of SO2 on dust particles. Total Fe(II) deposition in the ocean region of East Asia reached 327 tons during the 4-day dust event, and created a calculated primary productivity of ~520 mgC m−2 d−1 in the Kuril Islands, which can support almost 100% of the observed mean marine primary productivity in spring in this region (526 mgC m−2 d−1).
Highlights
Over the last few decades, China has experienced urbanization and industrialization processes on an unprecedented scale
The back trajectories are calculated by a Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT v4) model based on WRF output with 80 km resolution
The concentration of SO24− taken up by dust particles significantly increased from 5 μg m−3 to 20 μg m−3 when the air mass reached the North China Plain
Summary
Over the last few decades, China has experienced urbanization and industrialization processes on an unprecedented scale. More than 120 cities have populations of more than one million. This rapid growth in such a short period of time has led to a remarkable increase in material wealth and a higher standard of living, but has caused serious so-called “complicated air pollution”, which means various types of pollution (e.g. acid rain, coal smog, photochemical smog, duststorm and haze) are present together in China (He et al, 2002). The chemical transformation and transport processes in this “complicated air pollution” make emissions controls more difficult. The interaction between gas and aerosols creates major challenges for policy makers. Approaches to reduce “complicated air pollution” and its impact on other regions have already become the research focus for Chinese environmental scientists
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