Ship-based MAX-DOAS measurements of tropospheric NO<sub>2</sub>, SO<sub>2</sub>, and HCHO distribution along the Yangtze River

Abstract

Abstract. In this paper, we present ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric trace gases distribution along Yangtze River during winter 2015. The measurements were 15 performed along Yangtze River between Shanghai and Wuhan covering major industrial areas in eastern China.Tropospheric vertical column densities (VCDs) of nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and formaldehyde (HCHO) were retrieved using air mass factor calculated by radiative transfer model. Enhanced tropospheric NO 2 and SO 2 VCDs were detected over downwind areas of industrial zones over Yangtze River. In addition, spatial distributions of atmospheric pollutants are strongly affected by meteorological conditions, i.e., positive correlations were found between concentration of 20 pollutants and wind speed over these areas indicating strong influence of transportation of pollutants from high-emission upwind areas along Yangtze River. Comparison of tropospheric NO 2 VCDs between ship-based MAX-DOAS and OMI satellite observations shows good agreement with each other with Pearson correlation coefficient (R) of 0.82. In this study, NO 2 /SO 2 ratio was used to estimate the relative contributions of industrial sources and vehicle emissions to ambient NO 2 levels. Analysis results of NO 2 /SO 2 ratio shows that higher contribution of industrial NO 2 emissions in Jiangsu province, 25 while NO 2 levels in Jiangxi and Hubei provinces are mainly related to vehicle emissions. These results indicate that different pollution control strategies should be applied in different provinces. In addition, multiple linear regression analysis of ambient carbon monoxide (CO) and odd oxygen (O x ) indicated that the primary emission and secondary formation of HCHO contribute 54.4 ± 3.7% and 39.3 ± 4.3% to the ambient HCHO, respectively. The largest contribution from primary emissions in winter suggested that photochemically induced secondary formation of HCHO is reduced due to lower solar 30

Opposite variations of peak and low ozone concentrations in eastern China: Positive effects of NOx control on ozone pollution

“…31%, and 22% in Hefei, Huaibei, and Tai' an, respectively. Similar diurnal variation trend also found in Shenyang (Xue et al, 2022), Nanjing (Hong et al, 2018), Guangzhou (Lin et al, 2022) and Shenzhen , and also in Rome (Possanzini et al, 2002), Mexico (Possanzini et al, 2002), and Toyama (Taguchi et al, 2021), etc. It is worth noting that secondary HCHO VMRs in Hefei, Huaibei and Tai' an increased significantly between 16:00 and 17:00, and the specific reasons remain to be further investigated.…”

“…According to previous studies in central and eastern China (Ma et al, 2016;Wang et al, 2015), the background level of HCHO was limited to 1 ppb. Therefore, the regression parameter was fixed at 1 ppb in this study (Hong et al, 2018;Lin et al, 2022). The fitted parameters of the MLR for measured and modelled HCHO are shown in Fig.…”

“…of uneven emission reductions in O3 precursors (substantial decrease of NOx emissions and slightly increase of VOCs emissions), it is critical to accurately determine the O3 formation sensitivity to its precursors, especially at high temporary resolution. Here, secondary HCHO and NO2 are intended to be selected as representatives of VOCs and NOx respectively (Hong et al, 2018;Ren et al, 2022a;Xue et al, 2022;Hong et al, 2022;Lin et al, 2022). The surface NO2 and HCHO VMRs retrieved from ground-based MAX-DOAS observations were used to diagnose the surface O3 formation sensitively regime.…”

“…The HCHO from primary emissions was highest between 08:00 and 10:00 (about 2.63, 2.50, and 4.30 ppb in Hefei, Huaibei, and Tai' an, respectively), then gradually decreased, reaching the lowest concentration around 15:00, about 1.78, 1.54, and 1.82 ppb in Hefei, Huaibei, and Tai' an, respectively, and then gradually rising. The high primary HCHO concentrations in the morning and evening may be due to emissions from traffic 10 Lin et al, 2022;Hong et al, 2018). Secondary HCHO concentrations were lowest in the morning, about 0.58, 0.84, and 0.65 ppb in Hefei, Huaibei, and Tai' an, respectively, with the enhancement of photochemical reactions and the resumption of human activities, the secondary HCHO concentrations gradually increased from 08:00 to 12:00, and the first peak usually occurred at 11:00-14:00.…”

Prediction of Vertical Profile of NO₂ Using Deep Multimodal Fusion Network Based on the Ground-Based 3-D Remote Sensing

“…The green line represented the grid of WRF-CHEM with a spatial resolution of 20 × 20 km. [17], sulfur dioxide (SO 2 ) [18], formaldehyde (HCHO) [19], Oxygen dimer (O 4 ) [20], [21], Nitrous acid (HONO) [9], Glyoxal [22]), and tropospheric column densities, surface volume mixing ratios (VMRs), vertical profiles of aerosol extinction, and trace gas mixing ratios. The MAX-DOAS observations have been performed on a range of flexible applications, such as ground-based stations [16] and mobile platforms (e.g., cars [23], ships [19], and aircraft [24]).…”