Quantifying wind-induced impacts on particulate Cu footprint in the Yangtze Estuary

Under two wind conditions, a polar coordinated segmented quantification method (PCSQM) taking the easternmost point of Chongming Island (121°59'20″E, 31°29'38″N) as the origin of the coordinate was proposed to quantify wind-induced impacts on the heavy metal footprint emitted from four simulation sites on the main waterway of the Yangtze Estuary. One wind condition was that of a real wind field in 2019 called Case 1; the other one was a combination of monthly maximum wind speed selected from 1989 to 2019 called Case 2. In the comparison of these two conditions, the PCSQM was used to calculate the footprint excursion of four simulation sites mentioned, including three major urban sewage outlets and the upstream pollution source, represented by Xuliujing (XLJ) during the biological sensitive aggregation period of the Yangtze Estuary (BAPYE). The results showed that the Cu footprint was closer to Chongming Island and showed a trend of narrowing its coverage under Case2 compared with Case1. The Southeast section of the XLJ had the broadest width (83.46 km), while the Southwestern section of BLG had the narrowest width (3.52 km). Coincidentally, both the maximum (-29.99%) and the minimum excursion (-0.13%) were derived from XLJ, corresponding to its Southeast section and Southwest section.