Air quality in the middle and lower reaches of the Yangtze River channel: a cruise campaign

The Yangtze River is the longest river in China; nearly one-third of the national population lives along the river. Air quality over the Yangtze River is important as it may have significant influences on the aquatic ecosystem, the health of everyone living along the Yangtze River, and regional climate change. Chemical compositions of ambient aerosol were determined during a comprehensive cruise campaign carried out along the mid–lower reaches of the Yangtze River (MLYR) in winter of 2015. The total average concentration of PMinline-formula_2.5 was inline-formula119.29±33.67 inline-formulaµg minline-formula⁻³, and the dominant ionic composition in PMinline-formula_2.5 was inline-formula $M6inlinescrollmathmlchem{\mathrm{normal\; SO}}_{\mathrm{normal\; 4}}^{\mathrm{normal\; 2}-}$ 29pt17ptsvg-formulamathimga8455a3a3390243c17ea2f3ca419ac4e acp-18-14445-2018-ie00001.svg29pt17ptacp-18-14445-2018-ie00001.png with an average concentration of inline-formula15.21±6.69 inline-formulaµg minline-formula⁻³, followed by inline-formula $M10inlinescrollmathmlchem{\mathrm{normal\; NO}}_{\mathrm{normal\; 3}}^{-}$ 25pt16ptsvg-formulamathimgdd23f13eb24280cbe650be4567ce8571 acp-18-14445-2018-ie00002.svg25pt16ptacp-18-14445-2018-ie00002.png (inline-formula13.76±4.99 inline-formulaµg minline-formula⁻³), inline-formula $M14inlinescrollmathmlchem{\mathrm{normal\; NH}}_{\mathrm{normal\; 4}}^{+}$ 24pt15ptsvg-formulamathimgcb88f58b3b25b473f7c5a29ace587a7f acp-18-14445-2018-ie00003.svg24pt15ptacp-18-14445-2018-ie00003.png (inline-formula9.38±4.35 inline-formulaµg minline-formula⁻³), and inline-formulaCa²⁺ (inline-formula2.23±1.24 inline-formulaµg minline-formula⁻³) in this cruise. Based on the filter samples, the concentration and chemical composition of PMinline-formula_2.5 were remarkably varied or fluctuated from coastal areas to inland over the MLYR region. Crustal elements (Ca, Mg, Al, and K) from floating dust showed peak concentrations in the Yangtze River Delta (YRD) region, while secondary inorganic species (inline-formula $M23inlinescrollmathmlchem{\mathrm{normal\; SO}}_{\mathrm{normal\; 4}}^{\mathrm{normal\; 2}-}$ 29pt17ptsvg-formulamathimg241aaf10b8eb4e06a685c19af97ab514 acp-18-14445-2018-ie00004.svg29pt17ptacp-18-14445-2018-ie00004.png , inline-formula $M24inlinescrollmathmlchem{\mathrm{normal\; NO}}_{\mathrm{normal\; 3}}^{-}$ 25pt16ptsvg-formulamathimga226654730cbc5374d88051445c2d9d9 acp-18-14445-2018-ie00005.svg25pt16ptacp-18-14445-2018-ie00005.png , and inline-formula $M25inlinescrollmathmlchem{\mathrm{normal\; NH}}_{\mathrm{normal\; 4}}^{+}$ 24pt15ptsvg-formulamathimg99206ed7ef1aca77e3d7d51ee4a86723 acp-18-14445-2018-ie00006.svg24pt15ptacp-18-14445-2018-ie00006.png ) and some of the most enriched elements (Pb, As, Se, and Cd) presented high levels in central China (Wuhan region). The significant correlation between Se and inline-formula $M26inlinescrollmathmlchem{\mathrm{normal\; SO}}_{\mathrm{normal\; 4}}^{\mathrm{normal\; 2}-}$ 29pt17ptsvg-formulamathimge74435277bc316ae776b5cb3f2b0ff2d acp-18-14445-2018-ie00007.svg29pt17ptacp-18-14445-2018-ie00007.png suggested that coal combustion may play an important role in secondary inorganic aerosol formation. The relatively high enrichment factors (EFs) of Ca (EFs inline-formula>100) suggested the crustal elements may derive from anthropogenic sources. Furthermore, the concentration of levoglucosan in PMinline-formula_2.5 and the CO column level from satellite observation were greatly enhanced in the rural areas (Anhui and Jiangxi), indicating that biomass burning may make a remarkable contribution to rural areas. The concentrations of typical tracer for heavy oil (V and Ni) significantly increased in the Shanghai port, which was mainly ascribed to ship emissions, based on the air mass source analysis and the relatively high ratio of V inline-formula∕ Ni as well. The results shown herein portray a good picture of air pollution along the Yangtze River.