Influence of Dredging on Sedimentary Arsenic Release for a Tide-Influenced Waterfront Body

Abstract

We evaluated the influence of sediment dredging on sedimentary As release for the Inner Lake, a typical tide-influenced waterfront body in the middle to lower reaches of the Yangtze River in Zhengjiang, China. By field investigation and laboratory experiment, the As content in the deposited sediment before dredging was analyzed and the relationship between dynamic disturbance and sedimentary As release intensity was established. Using a numerical model in which the factors of water current, suspended sediment, and As were coupled, the processes of As migration were simulated for typical years and tidal cycles before and after dredging. The results show that: (i) the amounts of sedimentary As release during the tidal cycles in the flood season and the dry season after dredging were reduced by 14.6 and 28.1%, respectively, compared with before dredging; (ii) after removal of the surface polluted sediment, the annual volumes of internal released As in the high-water year, common-water year, and low-water year were decreased to 11.89, 4.94, and 4.89 Mg, respectively; and (iii) the highest reduction rate could reach 27.5% in the common-water year, while the lowest was 10.92% in the high-water year because the massive water exchange with the Yangtze River in the high-water year resulted in an enhanced dynamic disturbance that played a more dominating role in the internal As release than the surface sediment removal. The results of this study may be useful for other researchers of water environment protection for waterfront bodies.

Research on the Relationship between Water Diversion and Water Quality of Xuanwu Lake, China

“…We set the maximum water diversion (3,500,000 m 3 /day), daily water diversion (2,800,000 m 3 /day), and optimal water diversion (1,800,000 m 3 /day) as the calculation plan, taking into account no wind and prevailing winds (southeast wind and northwest wind) [47,48,49]. According to the field survey, the pollutant ratio of the ③ drainage ditch was significant, so the ③ drainage ditch will be blocked during the optimal water diversion [50,51,52], as shown in Table 2.…”

Research on Water Environment Regulation of Artificial Playground Lake Interconnected Yangtze River

“…Chl-a concentration was regarded as the evaluation index. According to the principle of mass conservation, the basic equation of eutrophication variables is [36,37,38,39,40,41]: $\frac{\partial C_{c\mathrm{hl}-\mathrm{normala}}}{\partial t}+U\frac{\partial C_{\mathrm{chl}-\mathrm{normala}}}{\partial x}+V\frac{\partial C_{\mathrm{chl}-\mathrm{normala}}}{\partial y}=\frac{\partial }{\partial x}\left(E_x\frac{\partial C_{\mathrm{chl}-\mathrm{normala}}}{\partial x}\right)+\frac{\partial }{\partial y}\left(E_y\frac{\partial C_{\mathrm{chl}-\mathrm{normala}}}{\partial y}\right)+S_{\mathrm{chl}-\mathrm{normala}}$ where:$S_{chl-a}=G_{PI}\left(t\right)-D_{PI}\left(t\right)-\frac{V_s}{D}$ $G_{PI}={\mathrm{K}}_1·Phtsy·F\left(N,P\right)$ $D_{PI}=\mu ·F\left(N,P\right)$…”

“…Due to the current planning state and no excavation operations on the playground, the model calculation results were checked according to Wang [35,36,37,38], in situ data and routine monitoring data of Neijiang Lake and diversion channel, in order to meet more the strong relation between the real status of the park and the model to estimate the effect of changes. The model water quality and eutrophication parameters are listed in Table 2.…”

“…In the early stages of lake eutrophication, phosphorus is the limiting factor for the algae growth, and its increased concentration leads to the massive growth of algae. With the rapid growth of urban population and the rapid development of industrial and agricultural production in China, the eutrophication of urban water bodies has become increasingly serious and has become a serious ecological problem of urban environment [35,36,37]. The concentration of dissolved oxygen in water decreases, which can cause the death of aquatic animal, especially fish [38,39,40,41].…”

Research into the Eutrophication of an Artificial Playground Lake near the Yangtze River

“…Due to the current under-planning state and no excavation operations at Playground Lake, the results of the model calculation were checked to ensure that they meet stronger relations between the real status of the park and the model to estimate the effect of changes, according to Wang Hua's in situ data and routine monitoring data of Neijiang Lake and diversion channel [22][23][24][25]. The main water quality and eutrophication parameters in the model are shown in Table 1.…”