Spatiotemporal variations of wet and dry Sulfur deposition in Yangtze River Delta, China

Sulfur deposition (Sdep) is an important process of sulfur cycling in terrestrial ecosystems, thus estimating the spatiotemporal variations of Sdep is crucial to understand its impact on terrestrial ecosystems. Taking the developed Yangtze River Delta (YRD) in eastern China as the study area, the Sdep (in forms of gas-phase dry, particle-phase dry, and wet) were estimated based on the observations of sulfur dioxide (SO2) concentrations from the Ozone Monitoring Instrument (OMI). The results showed that: the average Sdep flux in the YRD was 27.45 +/- 8.60 kg S ha- 1 yr- 1, and the total Sdep was mainly attributed to the wet deposition (wet: dry = 1.43). The Sdep experienced a significant decreasing trend, which decreased by 36.81% in 2020, compared with that in 2006. In terms of spatial distribution, Sdep showed strong variations, ranging from 9.70 to 67.51 kg S ha- 1 yr- 1; the high-value hotspots, which were initially distributed in the northern border regions of the study area, along the Yangtze River, and the Hangjiahu Plain in Zhejiang, have moved to the Wanzhong Plain in Anhui and the Jinqu Basin in Zhejiang during 2006-2020; the rate of change in urban Sdep was significantly higher than that in rural areas, with an average annual rate of change of -1.15 against -0.79 kg S ha- 1 yr- 1. By 2018-2020, there was no longer a significant difference in Sdep between urban and rural areas, with average values of 10.28 and 10.43 kg S ha- 1 yr- 1, respectively.