Study on Total Control of Total Nitrogen in the Laizhou Bay

Abstract

Human activity imposes a stronger and increasing impact on the coastal environment by land-based discharge and run-off pollution inputs. Land-based total nitrogen (TN) pollution, as the main cause of eutrophication in the Laizhou Bay, China, should be controlled effectively. Based on a three-dimensional pollution transport model, 20 groups of allocation schemes were designed under the requirement that the allocations of three estuaries in the inner bay were adjusted properly, while the two estuaries in the outer bay, i.e., the Yellow River and the Jiehe River, were kept unchanged. The statistical results show that the area ratio of heavily polluted seawater to the entire Laizhou Bay reached the maximum (35.14%) when the load allocation of the Xiaoqinghe River accounted for a high proportion (65%), and the Yuhe River and the Jiaolaihe River accounted for 15% and 20%, respectively. Overall, the pollution levels of the Laizhou Bay were positively associated with the allocation of the Xiaoqinghe River. Reducing pollutant allocation in the Xiaoqinghe River contributed most to the improvement of the seawater quality of the entire Laizhou Bay, and it was followed by a reduction in the Yuhe River and the Jiaolaihe River.

Ladderane and lipid biomarker estimate of the sources and distributions of anammox activities in Laizhou Bay of the Bohai Sea, China

“…Moreover, the river discharge and the south Bohai anti-clock coastal current results in rather complicated hydrologic conditions for this small bay (Qiao et al, 2010;Zhou et al, 2017;Wei et al, 2019). The eutrophication area and hydrologic condition of Laizhou Bay were closely linked to the river input, which might reveal the potential differences of biogeochemical process in nearshore area and offshore area (Jiang et al, 2018;Zhang et al, 2019;Peng et al, 2021).…”

“…The Laizhou Bay is generally shallow, with the average water depth of ~9 m (Jiang et al, 2018). Multiple rivers (Figure 2 ) discharge terrestrial materials and nutrients to the bay each year (Jiang et al, 2005;Guo et al, 2015;Wang et al, 2019b;Zhang et al, 2019;Peng et al, 2021). The highest nutrient concentrations normally occurred in summer due to the strong river runoff in wet season (Peng et al, 2021).…”

“…Multiple rivers (Figure 2 ) discharge terrestrial materials and nutrients to the bay each year (Jiang et al, 2005;Guo et al, 2015;Wang et al, 2019b;Zhang et al, 2019;Peng et al, 2021). The highest nutrient concentrations normally occurred in summer due to the strong river runoff in wet season (Peng et al, 2021). Rivers flowing into Laizhou Bay, like the Xiaoqing River (XQR), were severely contaminated by industrial and agricultural sewage, which could further affect the coastal ecological environment and biogeochemical cycles in Laizhou Bay (He et al, 2018a;He et al, 2018b).…”

“…The offshore 'area B' (Figure 2) was impacted by the Yellow River discharge and Bohai Sea circulations. Although the Yellow River contributed significantly to the hydrology and ecology condition in the northwestern bay (Liu et al, 2012;Peng et al, 2021), anammox activity in the Yellow River Estuary was proved to be very weak comparing with that of the Bohai Sea (Zhang et al, 2017b;Zhang et al, 2018).…”

Categorizing numeric nutrients criteria and implications for water quality assessment in the Pearl River Estuary, China

“…When DIP cannot meet the needs of phytoplankton, heterotrophic bacteria in the ocean supplement DIP by hydrolyzing dissolved organic phosphorus (DOP) using alkaline phosphatase (Zhang et al, 2021). With the rapid development of industry and agriculture, the use of pesticides, fertilizers, and fossil fuels has increased significantly, and a large amount of nitrogen and phosphorus nutrients have been transported to the estuaries and coasts through river flow, atmospheric deposition, and groundwater discharge, resulting in severe eutrophication (Herbeck et al, 2013;Li et al, 2014;Meńesguen, 2014;Wang et al, 2018;Zhang et al, 2019b;Zhang et al, 2020a;Peng et al, 2021). Nutrient criteria representing the enrichment status of surface waters that are minimally impacted by human development maybe defined as the threshold value that supports a particular beneficial designated use (US EPA, 1998;US EPA, 2001).…”