Aldhaif Abdulmonam M, Lopez David H, Dadashazar Hossein, Sorooshian Armin
Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.
Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
Atmos Environ (1994). 2020 Jun 15;231. doi: 10.1016/j.atmosenv.2020.117456. Epub 2020 Apr 5.
This study examines 14 years (2004-2017) of surface aerosol composition data from the EPA IMPROVE network with a focus on the monthly profile, sources, and chemical nature of extreme dust events (>92nd percentile of fine soil concentration each month) impacting ten sites along the United States East Coast ranging in latitude from Florida to Maine. Based on trajectory, remote sensing, and reanalysis data, dust events were categorized into four source categories: African, Asian, Mix (African + Asian), and Other (anything other than African and Asian). The results reveal that extreme dust events account for between 3.3% and 4.6% of total available days depending on the site. March-April-May (MAM) had the most (174) dust events, followed by June-July-August (JJA) with 172, and then by September-October-November (SON) with 160 and December-January-February (DFJ) with 150. There is a variability in the predominant dust sources based on latitude, with African and Other sources more influential from North Carolina to the south, while Asian and Other were most important from New Jersey to the north. The Mix category is consistently the least frequent dust category at all sites. The African dust category was linked to the highest fine soil levels across the entire East Coast relative to other sources regardless of location. JJA is mostly impacted by African dust for sites ranging from Florida to New Jersey, while MAM is dominated by Asian dust for all sites. Mix events occurred mostly between April and October and Other events were most common outside of MAM and JJA seasons. Seven out of ten sites had Other as the most dominant source. Aerosol constituents organic carbon (OC) and elemental carbon (EC) had higher average concentrations in Other events (2.39 ± 0.78 μg m and 0.79 ± 0.81 μg m, respectively) as compared to the other three source categories, suggestive of regional anthropogenic emissions. Moreover, the ratios of elements (Si:Al, K:Fe, Fe:Ca, Al:Ca) contributing to fine soil and PM:PM exhibited distinct values depending on the dust source category and the site. This study builds on the growing evidence of the importance of long-range transport of dust in impacting distant regions and how a variety of sources can impact the U.S. East Coast at all times of the year.
本研究考察了美国环境保护局（EPA）改进网络14年（2004 - 2017年）的地表气溶胶成分数据，重点关注影响美国东海岸从佛罗里达州到缅因州纬度范围内10个站点的极端沙尘事件（每月细土浓度超过第92百分位数）的月度分布、来源和化学性质。基于轨迹、遥感和再分析数据，沙尘事件被分为四类来源：非洲源、亚洲源、混合源（非洲源 + 亚洲源）和其他源（非洲源和亚洲源以外的任何来源）。结果表明，根据站点不同，极端沙尘事件占总有效天数的3.3%至4.6%。3月至4月至5月（MAM）沙尘事件最多（174次），其次是6月至7月至8月（JJA），有172次，然后是9月至10月至11月（SON），有160次，12月至1月至2月（DFJ）有150次。根据纬度不同，主要沙尘来源存在差异，从北卡罗来纳州到南部，非洲源和其他源的影响更大，而从新泽西州到北部，亚洲源和其他源最为重要。混合源类别在所有站点始终是出现频率最低的沙尘类别。在整个东海岸，无论位置如何，相对于其他来源，非洲沙尘类别与最高的细土水平相关。对于从佛罗里达州到新泽西州的站点，JJA主要受非洲沙尘影响，而对于所有站点，MAM主要受亚洲沙尘主导。混合事件大多发生在4月至10月之间，其他事件在MAM和JJA季节之外最为常见。10个站点中有7个站点以其他源为最主要来源。与其他三类来源相比，气溶胶成分有机碳（OC）和元素碳（EC）在其他事件中的平均浓度更高（分别为2.39±0.78μg/m和0.79±0.81μg/m），这表明存在区域人为排放。此外，构成细土和PM:PM的元素（Si:Al、K:Fe、Fe:Ca、Al:Ca）的比值根据沙尘来源类别和站点呈现出不同的值。本研究基于越来越多的证据，证明沙尘远距离传输对遥远地区的影响以及各种来源如何在一年中的任何时候影响美国东海岸。
