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Despite decades of progress in reducing nitrogen oxide (NO_x) emissions, ammonium nitrate (AN) remains the primary inorganic component of particulate matter (PM) in Los Angeles (LA). Using aerosol mass spectrometry over multiple years in LA illustrates the controlling dynamics of AN and their evolution over the past decades. These data suggest that much of the nitric acid (HNO₃) production required to produce AN in LA occurs during the nighttime via heterogeneous hydrolysis of N₂O₅. Further, we show that US Environmental Protection Agency–codified techniques for measuring total PM_2.5fail to quantify the AN component, while low-cost optical sensors demonstrate good agreement. While previous studies suggest that declining NO_xhas reduced AN, we show that HNO₃formation is still substantial and leads to the formation of many tens of micrograms per cubic meter of AN aerosol. Continued focus on reductions in NO_xwill help meet the PM_2.5standards in the LA basin and many other regions. 

In this work, we compare the air quality benefits of a variety of future policy scenarios geared towards controlling EGU (electricity generating units) emissions between the present-day conditions and 2050. While these policies are motivated by reducing CO2 emissions, they also yield significant co-benefits for criteria pollutants, such as ozone and PM2.5. An integrated set of clean energy policies were examined to assess the time-varying costs and benefits of a range of decarbonization strategies, including business as usual and the Affordable Clean Energy plan, with a primary focus on others that look to achieve very low, if not zero, CO2 emissions from the EGU sector by 2050. Benefits assessed include mitigation of greenhouse gas emissions as well as air quality co-benefits. In this introductory work, we describe the potential air quality changes from various clean air policies, to set the stage for upcoming work looking at health and monetized benefits. Emission changes for key pollutants are forecast using the Integrated Planning Model (IPM), which are then transformed into emission inputs for the Community Multiscale Air Quality Model (CMAQ). For all primary scenarios considered that achieve large greenhouse gas decreases, significant reductions in ozone and PM are realized, mainly in the eastern US, and all policies produce air quality benefits. 

Abstract Implementing Paris Climate Accord is inhibited by the high energy consumption of the state-of-the-art CO₂capture technologies due to the notoriously slow kinetics in CO₂desorption step of CO₂capture. To address the challenge, here we report that nanostructured TiO(OH)₂as a catalyst is capable of drastically increasing the rates of CO₂desorption from spent monoethanolamine (MEA) by over 4500%. This discovery makes CO₂capture successful at much lower temperatures, which not only dramatically reduces energy consumption but also amine losses and prevents emission of carcinogenic amine-decomposition byproducts. The catalytic effect of TiO(OH)₂is observed with Raman characterization. The stabilities of the catalyst and MEA are confirmed with 50 cyclic CO₂sorption and sorption. A possible mechanism is proposed for the TiO(OH)₂-catalyzed CO₂capture. TiO(OH)₂could be a key to the future success of Paris Climat e Accord.