美国有机碳性质的变化。,Environmental Science & Technology

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美国有机碳性质的变化。
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-05-28 , DOI: 10.1021/acs.est.0c02225
Amy E Christiansen ₁ , Annmarie G Carlton ₁ , William C Porter ₂

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整个美国（CONUS）的总有机碳（TOC）质量浓度正在下降。我们调查了有机碳（OC）热组分[OC1（在140°C时挥发），OC2（280°C），OC3（480°C），OC4（580°C）]和热解碳（PC）的年代际变化趋势，报道在121个位置我nteragency中号的onitoring临tected V isual Ë2005年至2015年的环境（IMPROVE）网络遍布CONUS的23个地区。PC和OC2驱动力的降低会降低TOC（TOC = OC1 + OC2 + OC3 + OC4 + PC）的质量浓度。从2005年到2015年，OC2减少了40％，PC减少了34％。最大的绝对质量下降发生在美国东部，并且在整个CONUS中，以当地浓度归一化的相对变化更加一致。使用特定于区域和季节的OM：OC比率，可将OC转换为有机物质（OM）。用GEOS-Chem进行的模拟重现了OM趋势，并表明整个CONUS的下降是由于气溶胶液态水（ALW）的化学作用。各个模型物种，特别是衍生自异戊二烯氧化产物并形成ALW的气溶胶，显着相关（p<0.05），即使在干旱地区也使用OM2。这些发现有助于文献表明，针对SO ₂和NO _x排放的空气质量规则通过ALW化学诱导减少有机颗粒质量的协同效益，并且这些益处超出了美国东部。

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Changing Nature of Organic Carbon over the United States.

Total organic carbon (TOC) mass concentrations are decreasing across the contiguous United States (CONUS). We investigate decadal trends in organic carbon (OC) thermal fractions [OC1 (volatilizes at 140 °C), OC2 (280 °C), OC3 (480 °C), OC4 (580 °C)] and pyrolyzed carbon (PC), reported at 121 locations in the Interagency Monitoring of Protected Visual Environments (IMPROVE) network from 2005 to 2015 for 23 regions across the CONUS. Reductions in PC and OC2 drive decreases in TOC (TOC = OC1 + OC2 + OC3 + OC4 + PC) mass concentrations. OC2 decreases by 40% from 2005 to 2015, and PC decreases by 34%. The largest absolute mass decreases occur in the eastern United States, and relative changes normalized to local concentrations are more uniform across the CONUS. OC is converted to organic mass (OM) using region- and season-specific OM:OC ratios. Simulations with GEOS-Chem reproduce OM trends and suggest that decreases across the CONUS are due to aerosol liquid water (ALW) chemistry. Individual model species, notably aerosol derived from isoprene oxidation products and formed in ALW, correlate significantly (p < 0.05) with OM2, even in arid regions. These findings contribute to literature that suggests air quality rules aimed at SO₂ and NO_x emissions induce the cobenefit of reducing organic particle mass through ALW chemistry, and these benefits extend beyond the eastern United States.

更新日期：2020-05-28

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