School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195, United States.
Sci Total Environ. 2022 Apr 20;818:151699. doi: 10.1016/j.scitotenv.2021.151699. Epub 2021 Nov 16.
In the Western U.S., the prescribed burning of woody biomass in forests, mainly harvest slash, is the prevailing practice for in-woods fuel reduction and wildfire mitigation. Though these prescribed burns play an essential role in mitigating the wildfire risks, the resultant emission is a major air pollutants source that adversely affects air quality, negatively impacting human health. With an increased need for fire hazard reduction thinning, coupled with shrinking regional demand for lower quality biomass (pulpwood, hog-fuel, etc.), the volumes of unused biomass left on the forest floor as 'waste' will continue to grow. Reducing prescribed burns by utilizing this 'waste' biomass for alternate bio-based solutions (like bio-energy or bio-char) will enhance the economic feasibility of much-needed thinning operations and reduce uncontrolled emissions and related environmental and local health impacts. In this study, we simulate the increase in air pollutants due to additional prescribed fires in the Southwestern part of Washington State. Using the 'BlueSky smoke modeling system,' the study estimated the emissions associated with burning additional 726,000 dry t of residual biomass, which corresponds to a 30% increment from 2011. The burn was simulated over 29 days of the fall quarter and subsequently incorporated into the AIRPACT pollution transportation modeling system using the 2011 air quality and meteorological data as the baseline. The results showed that the ambient PM concentrations, due to the simulated pile burns, exceeded EPA's air quality standards on multiple days and in various locations across the Western part of the state, with two days reaching "very unhealthy" levels and one day reaching "hazardous" levels. By layering the census data on top of the pollution concentration data, the model estimated that, over the 29-day burn period, approximately 440,000 additional human days would be affected by higher than the EPA air-quality standards for ambient PM levels.
在美国西部，在森林中进行木质生物质的有计划燃烧，主要是采伐剩余物，是减少林内燃料和缓解野火的主要做法。尽管这些有计划的燃烧在减轻野火风险方面发挥了重要作用，但由此产生的排放是主要的空气污染物来源，会对空气质量产生不利影响，对人类健康造成负面影响。随着减少火灾危险疏伐的需求增加，加上区域对低质量生物质（纸浆材、粗原木等）的需求减少，留在林地上的未使用生物质作为“废物”的数量将继续增加。通过利用这种“废物”生物质替代生物基解决方案（如生物能源或生物炭）来减少有计划的燃烧，将提高急需疏伐作业的经济可行性，并减少无控制的排放和相关的环境及地方健康影响。在这项研究中，我们模拟了华盛顿州西南部因额外的有计划燃烧而增加的空气污染物。使用“BlueSky 烟雾建模系统”，研究估计了与燃烧额外的 72.6 万干吨剩余生物质相关的排放，这相当于 2011 年的 30%增幅。燃烧模拟在秋季的 29 天内进行，随后将其纳入 AIRPACT 污染传输建模系统，使用 2011 年的空气质量和气象数据作为基准。结果表明，由于模拟的堆烧，环境 PM 浓度在多个地点和多个日期超过了 EPA 的空气质量标准，在该州西部的多个地点和多个日期，有两天达到了“非常不健康”的水平，一天达到了“危险”的水平。通过将人口普查数据叠加在污染浓度数据之上，该模型估计，在 29 天的燃烧期间，大约有 44 万人的额外天数将受到高于 EPA 空气质量标准的环境 PM 水平的影响。
