State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
Environ Sci Technol. 2024 Sep 17;58(37):16517-16524. doi: 10.1021/acs.est.4c06860. Epub 2024 Sep 4.
Aerosol acidity (or pH) is one central parameter in determining the health, climate, and ecological effects of aerosols. While it is traditionally assumed that the long-term aerosol pH levels are determined by the relative abundances of atmospheric alkaline to acidic substances (referred to as hereinafter), we observed contrasting pH─ trends at different sites globally, i.e., rising alkali-to-acid ratios in the atmosphere may unexpectedly lead to increased aerosol acidity. Here, we examined this apparently counterintuitive phenomenon using the multiphase buffer theory. We show that the aerosol water content (AWC) set a pH "baseline" as the peak buffer pH, while the and particle-phase chemical compositions determine the deviation of pH from this baseline within the buffer ranges. Therefore, contrasting long-term pH trends may emerge when increases while the AWC or nitrate fraction decreases, or vice versa. Our results provided a theoretical framework for a quantitative understanding of the response of aerosol pH to variations in SO, NO versus NH, and dust emissions, offering broad applications in studies on aerosol pH and the associated environmental and health effects.
气溶胶酸度（或 pH 值）是决定气溶胶对健康、气候和生态影响的一个核心参数。虽然传统上认为气溶胶的长期 pH 值水平是由大气中碱性物质与酸性物质的相对丰度决定的（以下简称），但我们在全球不同地点观察到了相反的 pH 值趋势，即在大气中碱性物质与酸性物质的比例增加可能会导致气溶胶酸度增加。在这里，我们使用多相缓冲理论研究了这一明显违背直觉的现象。我们表明，气溶胶含水量（AWC）设定了一个 pH“基线”，即峰值缓冲 pH 值，而和颗粒相化学成分决定了 pH 值在缓冲范围内偏离基线的程度。因此，当 AWC 或硝酸盐分数减少，而增加，或者相反的情况下，可能会出现长期 pH 值趋势的对比。我们的研究结果为定量理解气溶胶 pH 值对 SO、NO 与 NH、和尘埃排放变化的响应提供了一个理论框架，在气溶胶 pH 值及其相关环境和健康影响的研究中具有广泛的应用。
