Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia
Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia
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DOI：
10.5194/acp-17-6611-2017
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发表时间：
2017-06-06
影响因子：
6.3
通讯作者：
Martin, Scot T.
中科院分区：
文献类型：
--
作者：
de Sa, Suzane S.;Palm, Brett B.;Martin, Scot T.
异戊二烯的大气化学作用有助于热带森林上空颗粒物（PM）的大量产生。异戊二烯在ho2优势条件下氧化产生的气相异戊二烯环氧二醇（IEPOX）随后被颗粒吸收，从而导致次生有机PM的产生。本研究调查了城市污染对这一途径可能产生的扰动。亚马孙中部测点位于巴西马瑙斯顺风4 ~ 6小时处。作为GoAmazon2014/5实验的一部分，测量于2014年雨季的2月至3月进行。利用Aerodyne气溶胶质谱仪采集的有机PM的质谱进行了正矩阵分解分析。一个已解决的统计因素（“IEPOX- soa因素”）通过IEPOX途径与PM生产相关联。IEPOX-SOA因子负荷与独立测量的iepox衍生PM示踪剂（即c -5-烯三醇和2-甲基四醇）的质量浓度相关（R分别为0.96和0.78）。与背景条件相比，污染条件下因子负荷以及负荷与有机PM质量浓度的比值均有所降低。当NOy浓度从0.5增加到2 ppb时，因子负荷和f降低了2 - 3倍。总体而言，硫酸盐浓度解释了因子负荷变化的37%。在根据NOy浓度将因子负荷划分为子集后，硫酸盐浓度解释了高达75%的变异性。考虑到这两个因素，数据集表明，增加NO浓度的抑制作用大于高硫酸盐浓度的增强作用。相对于背景条件，来自玛瑙斯的污染使NOy浓度比硫酸盐浓度显著升高。有鉴于此，正如亚马逊经济发展的某些情景所预期的那样，氮氧化物排放量的增加可能会大大改变目前在热带森林中普遍存在的PM生产途径，这意味着空气质量和区域气候的变化。
The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 h downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Mass spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor ("IEPOX-SOA factor") was associated with PM production by the IEPOX pathway. The IEPOX-SOA factor loadings correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C-5-alkene triols and 2-methyltetrols (R = 0.96 and 0.78, respectively). The factor loading, as well as the ratio f of the loading to organic PM mass concentration, decreased under polluted compared to background conditions. For an increase in NOy concentration from 0.5 to 2 ppb, the factor loading and f decreased by two to three fold. Overall, sulfate concentration explained 37% of the variability in the factor loading. After segregation of factor loading into subsets based on NOy concentration, the sulfate concentration explained up to 75% of the variability. Considering both factors, the data sets show that the suppressing effects of increased NO concentrations dominated over the enhancing effects of higher sulfate concentrations. The pollution from Manaus elevated NOy concentrations more significantly than sulfate concentrations relative to background conditions. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.