Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China.
Joint Laboratory for Electron Microscopy Analysis of Atmospheric Particles, Beijing 100012, China; Beijing Met High-Tech Co., Ltd, Beijing 102299, China.
Sci Total Environ. 2022 Sep 15;839:156342. doi: 10.1016/j.scitotenv.2022.156342. Epub 2022 May 29.
Aerosol liquid water content (ALWC) has important influences on atmospheric radiation and aerosol chemical processes. In this work, the changes in ALWC of PM were investigated over four seasons based on hourly monitoring of inorganic water-soluble ions and their gaseous precursors using the thermodynamic model ISORROPIA II. The results showed that the ALWC concentrations exhibited pronounced seasonal (autumn > summer > spring > winter) and diurnal variation characteristics. The sensitivity tests indicated that ALWC depended strongly on TSO (total sulfate (gas and aerosols) expressed as equivalent HSO), followed by TNO (total nitrate (gas and aerosols) expressed as equivalent HNO). The relatively low concentration of TCl (total chloride (gas and aerosols) expressed as equivalent HCl) limit its importance in the atmosphere. ALWC showed exponential growth features as a function RH in all four seasons. RH became the most influential factor on the variation of ALWC when RH exceeded 80% in all seasons. The seasonal average data showed that the ALWC increased from 2.92 μg·m to 75.83 μg·m when ambient RH increased from 30% to 90%, the associated sulfate, nitrate, and ammonium (abbreviated as SNA) mass fraction in PM rose from 0.39 to 0.58 in the atmosphere. The ALWC facilitated the formation of SNA through gas-particle conversion and partitioning. The self-amplifying processes between ALWC and SNA enhanced aerosol formation. By modeling ALWC under different seasonal atmospheric scenarios, it was found that reductions in chemical species could reduce ALWC concentrations in different degrees. Based on the current emission conditions, controlling excess NH emission could effectively reduce ALWC to a maximum of 45.71% in summer, indicating that NH control was crucial for reducing ALWC and PM concentrations under high levels of SO and NO.
气溶胶液态水含量（ALWC）对大气辐射和气溶胶化学过程有重要影响。本研究基于热力学模型 ISORROPIA II，利用小时监测无机水溶性离子及其气态前体，研究了 PM 中 ALWC 的四季变化。结果表明，ALWC 浓度具有明显的季节性（秋季>夏季>春季>冬季）和日变化特征。敏感性测试表明，ALWC 强烈依赖于 TSO（总硫酸盐（气体和气溶胶）表示为等效 HSO），其次是 TNO（总硝酸盐（气体和气溶胶）表示为等效 HNO）。相对较低浓度的 TCl（总氯（气体和气溶胶）表示为等效 HCl）限制了其在大气中的重要性。在所有四个季节中，ALWC 都表现出与 RH 呈指数增长的特征。在所有季节中，当 RH 超过 80%时，RH 成为影响 ALWC 变化的最主要因素。季节平均数据表明，当环境 RH 从 30%增加到 90%时，ALWC 从 2.92μg·m 增加到 75.83μg·m，相应的硫酸盐、硝酸盐和铵（简称 SNA）在 PM 中的质量分数从大气中的 0.39 增加到 0.58。ALWC 通过气粒转化和分配促进了 SNA 的形成。ALWC 和 SNA 之间的自我放大过程增强了气溶胶的形成。通过模拟不同季节大气情景下的 ALWC，发现减少化学物质可以不同程度地降低 ALWC 浓度。根据当前的排放情况，控制过量 NH 排放可以有效地将 ALWC 降低 45.71%，最大程度地降低夏季的 ALWC，这表明在 SO 和 NO 水平较高的情况下，控制 NH 对于降低 ALWC 和 PM 浓度至关重要。
