Influence of Sea-Land Breezes on the Tempospatial Distribution of Atmospheric Aerosols over Coastal Region

摘要

The influence of sea-land breezes (SLBs) on the spatial distribution and temporal variation of particulate matter (PM) in the atmosphere was investigated over coastal Taiwan. PM was simultaneously sampled at inland and offshore locations during three intensive sampling periods. The intensive PM sampling protocol was continuously conducted over a 48-hr period. During this time, PM_(2.5) and PM_(2.5-10) (PM with aerodynamic diameters ≤2.5μm and between 2.5 and 10μm, respectively) were simultaneously measured with dichotomous samplers at four sites (two inland and two offshore sites) and PM_(10) (PM with aerodynamic diameters ≤10 μm ) was measured with (3-ray monitors at these same 4 sites and at 10 sites of the Taiwan Air Quality Monitoring Network. PM sampling on a mobile air quality monitoring boat was further conducted along the coastline to collect offshore PM using a β-ray monitor and a dichotomous sampler. Data obtained from the inland sites (n = 12) and offshore sites (n = 2) were applied to plot the PM_(10) concentration contour using Surfer software. This study also used a three-dimensional meteorological model (Pennsylvania State University/National Center for Atmospheric Research Meteorological Model 5) and the Comprehensive Air Quality Model with Extensions to simulate surface wind fields and spatial distribution of PM_(10) over the coastal region during the intensive sampling periods. Spatial distribution of PM_(10) concentration was further used in investigating the influence of SLBs on the transport of PM_(10) over the coastal region. Field measurement and model simulation results showed that PM_(10) was transported back and forth across the coastline. In particular, a high PM_(10) concentration was observed at the inland sites during the day because of sea breezes, whereas a high PM_(10) concentration was detected offshore at night because of land breezes. This study revealed that the accumulation of PM in the near-ocean region because of SLBs influenced the tempospatial distribution of PM_(10) over the coastal region.