College of Chemistry, Zhengzhou University, Zhengzhou, 450001, China; Institute of Environmental Sciences, Zhengzhou University, Zhengzhou, 450001, China.
School of Ecology and Environment, Zhengzhou University, Zhengzhou, 450001, China; Institute of Environmental Sciences, Zhengzhou University, Zhengzhou, 450001, China.
Chemosphere. 2022 Nov;307(Pt 3):136028. doi: 10.1016/j.chemosphere.2022.136028. Epub 2022 Aug 13.
Carbonaceous fractions throughout the normal period and lockdown period (LP) before and during COVID-19 outbreak were analyzed in a polluted city, Zhengzhou, China. During LP, fine particulate matters, elemental carbon (EC), and secondary organic aerosol (SOC) concentrations fell significantly (29%, 32% and 21%), whereas organic carbon (OC) only decreased by 4%. Furthermore, the mean OC/EC ratio increased (from 3.8 to 5.4) and the EC fractions declined dramatically, indicating a reduction in vehicle emission contribution. The fact that OC1-3, EC, and EC1 had good correlations suggested that OC1-3 emanated from primary emissions. OC4 was partly from secondary generation, and increased correlations of OC4 with OC1-3 during LP indicated a decrease in the share of SOC. SOC was more impacted by NO throughout the research phase, thereby the concentrations were lower during LP when NO levels were lower. SOC and relative humidity (RH) were found to be positively associated only when RH was below 80% and 60% during the normal period (NP) and LP, respectively. SOC, Coal combustion, gasoline vehicles, biomass burning, diesel vehicles were identified as major sources by the Positive Matrix Factorization (PMF) model. Contribution of SOC apportioned by PMF was 3.4 and 3.0 μg/m, comparable to the calculated findings (3.8 and 3.0 μg/m) during the two periods. During LP, contributions from gasoline vehicles dropped the most, from 47% to 37% and from 7.1 to 4.3 μg/m, contribution of biomass burning and diesel vehicles fell by 3% (0.6 μg/m) and 1% (0.4 μg/m), and coal combustion concentrations remained nearly constant. The findings of this study highlight the immense importance of anthropogenic source reduction in carbonaceous component variations and SOC generation, and provide significant insight into the temporal variations and sources of carbonaceous fractions in polluted cities.
在中国污染城市郑州，分析了正常时期和 COVID-19 爆发前及期间的封锁期（LP）的碳质组分。在 LP 期间，细颗粒物、元素碳（EC）和二次有机气溶胶（SOC）浓度显著下降（分别下降 29%、32%和 21%），而有机碳（OC）仅下降 4%。此外，OC/EC 比值增加（从 3.8 增加到 5.4），EC 分数显著下降，表明车辆排放贡献减少。OC1-3、EC 和 EC1 具有良好相关性的事实表明 OC1-3 源自一次排放。OC4 部分来自二次生成，LP 期间 OC4 与 OC1-3 的相关性增加表明 SOC 份额减少。SOC 在整个研究阶段都受到 NO 的更大影响，因此当 NO 水平较低时，LP 期间的浓度较低。只有在正常时期（NP）和 LP 期间 RH 低于 80%和 60%时，OC4 才与 RH 呈正相关。通过正矩阵因子分析（PMF）模型，SOC 被确定为主要来源，包括煤炭燃烧、汽油车、生物质燃烧、柴油车。PMF 分配的 SOC 贡献分别为 3.4 和 3.0μg/m，与两个时期的计算结果（3.8 和 3.0μg/m）相当。在 LP 期间，汽油车的贡献下降最多，从 47%降至 37%，从 7.1μg/m 降至 4.3μg/m，生物质燃烧和柴油车的贡献分别下降 3%（0.6μg/m）和 1%（0.4μg/m），煤炭燃烧浓度基本保持不变。本研究结果强调了人为源减少在碳质成分变化和 SOC 生成中的重要性，并为污染城市碳质成分的时间变化和来源提供了重要的见解。
