Abstract: In the purpose of precise prevention and control of water pollution in river estuary, the movement footprint of heavy metals in the Yangtze River estuary was studied in this paper to comprehensively evaluate the influence of heavy metals on water sources in the estuary. According to the monitoring data at six sections of the Yangtze River Estuary from January to December 2016, the footprints of heavy metals in typical month (January) in dry season, typical month (May) in flat season, and typical month (August) in wet season were analyzed. The mathematical models of two-dimensional unsteady water environment were established and verified. The temporal and spatial distribution of heavy metals in the estuary was investigated. The results are as follows: (1) In different hydrological periods, the heavy metals in the Yangtze River estuary are affected by the runoff and tidal action of the Yangtze River. Particle motion speed in wet season is larger than that in flat season and dry season in sequence. In terms of spatial distribution, the particles released at Xuliujing enters three water source areas of the Yangtze River estuary. (2) In typical month (January) of dry season, the particle motion footprint is inconsistent. The motion speed of heavy metal particles at Beigang (the north port) is the fastest, 4.98 km/d, and finally reaches the East Sea. (3) In typical month (May) of flat season, the motion footprint of heavy metal particles at Xuliujing witnesses a largest speed 7.03 km/d, which differs from that in dry season, but flows along Beigang, and then spirals in a clockwise direction, eventually flowing into the East Sea. (4) In typical month (August) of wet season, the footprint of heavy metal is similar to that in flat season, but at Xuliujing and Beigang the motion speeds of particles are larger than those in flat water period, with the maximum speed amounting to 8.32 km/d at Beigang.

Key words: estuary, Yangtze River estuary, heavy metal, particle tracing, space-time distribution