Mahdi Badami Mohammad, Tohidi Ramin, Jalali Farahani Vahid, Sioutas Constantinos
University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA.
Atmos Environ (1994). 2023 Oct 1;310. doi: 10.1016/j.atmosenv.2023.119984. Epub 2023 Jul 25.
In this study, the water-solubility and sources of metals and trace elements in both fine and coarse particulate matter (PM) were investigated in Central Los Angeles. Sampling was performed in the winter, spring, and summer of 2022 at the Particle Instrumentation Unit (PIU) of the University of Southern California located in the proximity of I-110 freeway. Both fine and coarse PM samples were collected using Personal Cascade Impactors (PCIS) and chemically analyzed to determine their water-soluble and water-insoluble metal content. Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) were used to determine the sources of soluble and insoluble metals and obtain their contributions to total metal concentration. Our results indicate that the water-solubility of most of the metals is higher in the fine size fraction compared to the coarse fraction. Seasonal variations in the water solubility of selected metals for both coarse and fine fractions were observed, with higher water-soluble metal concentrations in summer for several species (e.g., , S, Pb, Cu, La, Ni, and ), possibly due to higher photochemical processing, while in winter, almost all species exhibited higher insoluble fraction concentrations. The PCA and MLR analyses results showed that tire and brake wear was the most significant contributor to the total metals for both fine soluble and insoluble portions, accounting for 35% and 75% of the total metals, respectively. Combustion sources also contributed substantially to water-soluble metals for fine and coarse size ranges, representing 40% and 32% of the total metal mass, respectively. In addition, mineral dust and soil and re-suspended dust were identified as the highest contributors to coarse metals. The MLR analysis also revealed that secondary aerosols contributed 11% to the fine water-soluble metals. Our results suggest that non-tailpipe emissions significantly contribute to both coarse and fine PM metals in the Central Los Angeles region.
在本研究中，对洛杉矶市中心细颗粒物和粗颗粒物（PM）中金属及微量元素的水溶性和来源进行了调查。2022年冬、春、夏三季，在南加州大学位于110号高速公路附近的粒子检测单元（PIU）进行了采样。使用个人级联撞击器（PCIS）收集了细颗粒物和粗颗粒物样本，并进行化学分析以确定其水溶性和水不溶性金属含量。采用主成分分析（PCA）和多元线性回归（MLR）来确定可溶性和不溶性金属的来源，并获得它们对总金属浓度的贡献。我们的结果表明，与粗颗粒相比，大多数金属在细颗粒中的水溶性更高。观察到粗颗粒和细颗粒中选定金属的水溶性存在季节性变化，夏季几种金属（如 、S、Pb、Cu、La、Ni和 ）的水溶性金属浓度较高，这可能是由于光化学过程较强，而在冬季，几乎所有金属的不溶性部分浓度较高。PCA和MLR分析结果表明，轮胎和刹车磨损是细颗粒可溶性和不溶性部分总金属的最重要贡献源，分别占总金属的35%和75%。燃烧源对细颗粒和粗颗粒大小范围内的水溶性金属也有很大贡献，分别占总金属质量的40%和32%。此外，矿物粉尘、土壤和再悬浮粉尘被确定为粗颗粒金属的最大贡献源。MLR分析还表明，二次气溶胶对细颗粒水溶性金属的贡献为11%。我们的结果表明，非尾气排放对洛杉矶市中心地区的粗颗粒和细颗粒PM金属都有显著贡献。
