Pollutant dispersion from the Xiaoqing River into the sea and its response to the nearshore construction

Pollutants from rivers are the main source of offshore pollution. Xiaoqing River is the main inlet river and pollutant source in the southwestern part of Laizhou Bay, Bohai Sea. In recent years, the scale of nearshore constructions on both sides of Xiaoqing River estuary is constantly expanding. The response of the inlet pollutant dispersion to the nearshore construction region need to be studied deeply. The influence of nearshore construction on the tidal field and the dispersion characteristics of the inlet pollutants (dissolved inorganic nitrogen and active phosphate) from Xiaoqing River were numerically simulated in MIKE21 model, and the response of the inlet pollutant dispersion to the nearshore construction was discussed. Results show that the construction of nearshore projects on both sides of the Xiaoqing River estuary has led to a decrease of 2-21 cm/s in flow velocity in the nearshore of the estuary. Dikes and breakwaters on both sides of the estuary blocked the dispersion of pollutants to the southeast and northwest, which reduced the dispersion range of pollutants into the estuary, increased the concentration of pollutants in the estuary, and aggravated the water pollution in local areas. Therefore, the construction of nearshore projects could weaken the tidal currents around the concentration and the pollutant dispersion capacity in the offshore marine areas.