On Aerosol Liquid Water and Sulfate Associations: The Potential for Fine Particulate Matter Biases
On Aerosol Liquid Water and Sulfate Associations: The Potential for Fine Particulate Matter Biases
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DOI：
10.3390/atmos11020194
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发表时间：
2020-02-01
期刊：
影响因子：
2.9
通讯作者：
Ghate, Virendra P.
中科院分区：
文献类型：
--
作者：
Babila, Jonathon E.;Carlton, Annmarie G.;Ghate, Virendra P.
在美国东部潮湿的地区，硫酸盐是气溶胶液态水（ALW）的替代品，这是一种测量不良的颗粒成分。alw -硫酸盐关系的区域和季节变化为调和关于颗粒硫和健康终点的流行病学和毒理学研究提供了潜在的解释。ALW促进极性物质从气相转移到颗粒相，影响颗粒pH值和金属氧化态。尽管ALW含量丰富，是不良健康终点的潜在指标，但在大多数颗粒物测量技术中，包括在使用联邦参考方法（FRM）监测仪的常规颗粒物（PM2.5）网络中，ALW在很大程度上被去除，这些监测仪用于流行病学研究。我们发现，在可获得记录的典型年份2004年，在大多数（94%）站点的采样和过滤平衡过程中，环境ALW质量被去除，达到环境水质量的85%。ALW的去除可以诱导PM2.5中存在的其他半挥发性化合物的蒸发，如硝酸铵和许多有机物。这在PM质量测量中产生了一个工件，重要的是，它在空间或时间上不均匀。这表明排除ALW的PM2.5流行病学研究是有偏见的。这项工作为解决一些流行病学和毒理学研究中关于环境硫酸盐和健康影响的几十年差异提供了一个合理的解释。
In humid locations of the Eastern U.S., sulfate is a surrogate for aerosol liquid water (ALW), a poorly measured particle constituent. Regional and seasonal variation in ALW-sulfate relationships offers a potential explanation to reconcile epidemiology and toxicology studies regarding particulate sulfur and health endpoints. ALW facilitates transfer of polar species from the gas phase to the particle phase and affects particle pH and metal oxidation state. Though abundant and a potential indicator of adverse health endpoints, ALW is largely removed in most particulate matter measurement techniques, including in routine particulate matter (PM2.5) networks that use federal reference method (FRM) monitors, which are used in epidemiology studies. We find that in 2004, a typical year in the available record, ambient ALW mass is removed during sampling and filter equilibration to standard laboratory conditions at most (94%) sites, up to 85% of the ambient water mass. The removal of ALW can induce the evaporation of other semi-volatile compounds present in PM2.5, such as ammonium nitrate and numerous organics. This produces an artifact in the PM mass measurements that is, importantly, not uniform in space or time. This suggests that PM2.5 epidemiology studies that exclude ALW are biased. This work provides a plausible explanation to resolve multi-decade discrepancies regarding ambient sulfate and health impacts in some epidemiological and toxicological studies.