School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an 710021, China.
Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi'an 710054, China; Xi'an Center of Geological Survey, China Geological Survey, Xi'an 710054, China.
Environ Int. 2020 Mar;136:105515. doi: 10.1016/j.envint.2020.105515. Epub 2020 Jan 30.
Reactive oxygen species (ROS) are a class of substances that are of general concern in terms of human health and are used to represent the oxidation potential (OP) of the atmosphere. In this study, the ROS levels in 116 daily fine particulate matter (PM) samples taken over Xi'an in 2017 were measured with the dithiothreitol (DTT) method. The sources of DTTv (volume-based DTT consumption) in PM as well as their contributions were identified by both positive matrix factorization (PMF) and multiple linear regression (MLR) based on the measured chemical species in particulate matter (PM). The results showed that the yearly average DTTv over Xi'an was 0.53 nmol/min/m (0.19-1.10 nmol/min/m). The highest DTTv level occurred in winter, followed by spring, summer and autumn. DTTv was the most strongly correlated with the water-soluble organic carbon (WSOC; r = 0.85), but the effects of WSOC on DTTv were very limited. SO, NO, CO, elemental carbon (EC) and K (r > 0.64) had moderate correlations with DTTv and were moderately related to environmentally persistent free radicals (EPFRs) (r = 0.56). The linear mixed-effects model showed that pollutants originating from incomplete combustion had greater effects on DTTv than those from complete combustion. Source apportionment results from PMF showed that motor vehicle emissions (27.4%), secondary sulfates (21.6%) and coal combustion sources (18.8%) were more important contributors to the DTTv in PM than dust sources (8.4%), metal processing (4.9%), industrial emissions (11.3%) and secondary nitrates (7.5%). The PMF results for the DTTv were consistent with the MLR results, which verified that both PMF and MLR are feasible methods for source apportionment of PM as well as specific species such as ROS and EPFRs. Backward trajectory clusters showed that the dominant cluster groups were local and regional transport, while the OP of the PM over Xi'an was affected more by long-range transport than by local transport. As stated above, the improvement of atmospheric oxidation potential require not only regional efforts but also large-scale joint cooperation. Furthermore, this study on the OP of PM as well as the specific source information provides important guidance for health effect research.
活性氧（ROS）是一类普遍与人类健康相关的物质，常用于表示大气氧化潜能（OP）。本研究采用二硫苏糖醇（DTT）法测定了 2017 年西安采集的 116 个细颗粒物（PM）日样本中的 ROS 水平。基于颗粒物中测定的化学物质，采用正定矩阵因子分解（PMF）和多元线性回归（MLR）两种方法对 DTTv（基于体积的 DTT 消耗）的 PM 来源及其贡献进行了识别。结果表明，西安年平均 DTTv 为 0.53 nmol/min/m（0.19-1.10 nmol/min/m）。DTTv 水平冬季最高，其次是春季、夏季和秋季。DTTv 与水溶性有机碳（WSOC；r = 0.85）的相关性最强，但 WSOC 对 DTTv 的影响非常有限。SO、NO、CO、元素碳（EC）和 K（r＞0.64）与 DTTv 中度相关，与环境持久性自由基（EPFRs；r = 0.56）中度相关。线性混合效应模型表明，不完全燃烧源产生的污染物对 DTTv 的影响大于完全燃烧源。PMF 的源分配结果表明，机动车排放（27.4%）、二次硫酸盐（21.6%）和煤燃烧源（18.8%）对 PM 中 DTTv 的贡献大于扬尘源（8.4%）、金属加工（4.9%）、工业排放（11.3%）和二次硝酸盐（7.5%）。DTTv 的 PMF 结果与 MLR 结果一致，验证了 PMF 和 MLR 都是 PM 及其特定物种（如 ROS 和 EPFRs）源分配的可行方法。后向轨迹聚类表明，主导聚类组是本地和区域传输，而西安 PM 的 OP 受长距离传输的影响大于本地传输。综上所述，提高大气氧化潜能不仅需要区域努力，还需要大规模的联合合作。此外，本研究对 PM 的 OP 以及具体的源信息提供了对健康效应研究的重要指导。
