Changing Nature of Organic Carbon over the United States
Changing Nature of Organic Carbon over the United States
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DOI：
10.1021/acs.est.0c02225
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发表时间：
2020-09-01
影响因子：
11.4
通讯作者：
Porter, William C.
中科院分区：
文献类型：
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作者：
Christiansen, Amy E.;Carlton, Annmarie G.;Porter, William C.
在毗邻的美国(CONUS)，总有机碳(TOC)的质量浓度正在下降。我们调查了有机碳(OC)热组分[OC1(在140摄氏度下挥发)、OC2(280摄氏度)、OC3(480摄氏度)、OC4(580摄氏度)]和热解碳(PC)的十年趋势，这些数据在2005年至2015年期间在美国全国23个地区的机构间保护视觉环境监测(EMPAND)网络的121个地点报告。PC和OC2驱动的减少降低了TOC(TOC=OC1+OC2+OC3+OC4+PC)质量浓度。从2005年到2015年，OC2下降了40%，PC下降了34%。最大的绝对质量下降发生在美国东部，归一化为当地浓度的相对变化在整个CONUS范围内更加一致。有机碳使用区域和季节特定的有机质量(OM)：OC比率转换为有机质量(OM)。使用GEOS-Chem的模拟再现了OM的趋势，并表明整个CONUS的减少是由于气溶胶液态水(ALW)化学作用。个别模式物种，特别是来自异戊二烯氧化产物的气溶胶，在低海拔地区形成，与OM2显著相关(p<；0.05)，即使在干旱地区。这些发现有助于文献表明，针对SO2和NOx排放的空气质量规则可以通过ALW化学方法减少有机颗粒物质量，并且这些好处超出了美国东部。
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 degrees C), OC2 (280 degrees C), OC3 (480 degrees C), OC4 (580 degrees 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 NOx emissions induce the cobenefit of reducing organic particle mass through ALW chemistry, and these benefits extend beyond the eastern United States.