School of Civil & Environmental Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.
Environ Sci Technol. 2019 Aug 20;53(16):9646-9655. doi: 10.1021/acs.est.9b02005. Epub 2019 Aug 12.
Aerosol pH can affect gas-particle partitioning of semivolatile species, secondary aerosol formation, aerosol water uptake and growth, acid deposition, and, potentially, aerosol toxicity. Despite its importance, aerosol pH projected in the near future has not been addressed explicitly while investigating the response of aerosol concentrations to emission regulations. In this study, we apply CMAQ to simulate aerosol pH in 2011 and 2050 across the continental U.S. We also assess the influence of two major emission trends, declining SO emissions and rising NH emissions, with a set of sensitivity simulations. Our results show that the aerosols will remain acidic with average pH typically ranging from 0.5 to 3.5 in 2050. Further reducing domestic SO emissions does not significantly decrease aerosol acidity, even if SO emissions were reduced to preindustrial levels because of the nonlinear response of SO concentration to SO emissions, and the semivolatile NH-NH buffering effect. Aerosol pH response to NH emission increase will remain minor. Consequently, future fine particulate matter control efficiency will not be undercut by additional nitrate aerosol formation even if SO emissions from industry and electricity generation are aggressively controlled, although areas will see some substitution leading to nitrate increases if NO emissions are not reduced.
气溶胶 pH 值会影响半挥发性物质的气固分配、二次气溶胶的形成、气溶胶的吸湿性和增长、酸沉降，以及潜在的气溶胶毒性。尽管气溶胶 pH 值非常重要，但在研究气溶胶浓度对排放法规的响应时，尚未明确预测未来的气溶胶 pH 值。在这项研究中，我们应用 CMAQ 模拟了 2011 年和 2050 年美国大陆的气溶胶 pH 值。我们还通过一组敏感性模拟评估了两种主要排放趋势（SO 排放减少和 NH 排放增加）的影响。我们的结果表明，气溶胶仍将保持酸性，平均 pH 值通常在 2050 年介于 0.5 到 3.5 之间。即使 SO 排放因 SO 浓度对 SO 排放的非线性响应和半挥发性 NH-NH 缓冲作用而减少到工业化前的水平，进一步减少国内 SO 排放也不会显著降低气溶胶酸度。NH 排放增加对气溶胶 pH 值的响应仍将较小。因此，即使积极控制工业和发电行业的 SO 排放，未来细颗粒物控制效率也不会因额外硝酸盐气溶胶的形成而受到影响，尽管如果不减少 NO 排放，某些地区的硝酸盐排放将会增加。
