PurpleAir PM2.5 from the 2022-23 Florida agricultural-fire season

Smoke from agricultural fires is a potentially important source of fine
particulate matter (PM2.5) in the US. Sugarcane is burned in Florida to
facilitate the harvesting process, with the majority of these fires
occurring in the Everglades Agricultural Area (EAA), where there is only
one regulatory air quality monitor. During the 2022–2023 sugarcane burning
season (October–May), we used public low-cost PurpleAir sensors,
regulatory monitors, and 29 PurpleAir sensors deployed for this study to
quantify PM2.5 from agricultural fires. We found satellite imagery is of
limited use for detecting smoke from agricultural fires in Florida due to
the cloud cover, overnight smoke, and the fires being small and
short-lived. For these reasons, surface measurements are critical for
capturing increases in PM2.5 from smoke, and we used multiple
smoke-identification criteria. During the study period, median 24-hour
PM2.5 concentrations increased by 2.3–6.9 µg m-3 on smoke-impacted days
compared to unimpacted days, with smoke observed on 4–28% of the campaign
days (ranges from the different smoke-identification criteria). Further,
short-term PM2.5 increases were observed over 40 µg m-3 during smoke
events. We contrast the region near the EAA with large populations of
low-income and minoritized groups to the more affluent coastal region. The
inland region experienced more smoke-impacted monitor days than the
Florida east coast region, and there was a higher study-average smoke
PM2.5 concentration in the inland area. These findings highlight the need
to increase air quality monitoring near the EAA.

农业野火产生的烟气是美国细颗粒物（PM2.5）的一类潜在重要来源。佛罗里达州会通过焚烧甘蔗以便利收割作业，此类野火大多发生在大沼泽地农业区（Everglades Agricultural Area, EAA），该区域仅设有一台法定空气质量监测站。在2022-2023年度甘蔗焚烧季（10月至次年5月）期间，本研究借助公共低成本紫感（PurpleAir）传感器、法定空气质量监测站，以及本研究部署的29台紫感传感器，对农业野火产生的PM2.5进行量化分析。研究发现，受云量覆盖、夜间烟气残留以及野火规模小、持续时间短等因素影响，卫星遥感影像在佛罗里达州农业野火烟气检测方面实用性有限。基于上述原因，地面监测对于捕捉烟气导致的PM2.5浓度升高至关重要，因此本研究采用了多套烟气识别标准。在研究周期内，相较于无烟气影响的天数，受烟气影响的日期中24小时PM2.5浓度中位数升高2.3~6.9 µg·m⁻³；根据不同烟气识别标准，研究活动期内4%~28%的天数被观测到存在烟气。此外，在野火烟气事件期间，观测到PM2.5浓度短时升高幅度超过40 µg·m⁻³。本研究将大沼泽地农业区周边聚居大量低收入与少数族裔群体的区域，与更为富裕的沿海区域进行了对比，结果显示内陆区域受烟气影响的监测天数多于佛罗里达州东海岸区域，且内陆地区的研究平均烟气PM2.5浓度更高。上述研究结果凸显了在大沼泽地农业区周边增设空气质量监测站点的必要性。