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.
Highlights
It is widely recognized that human activity has a strong influence on the marine and coastal environment [1,2,3]
Pollutants discharged from the Xiaoqinghe River have the greatest influence on the seawater quality, followed by the Yuhe River, and the Jiaolaihe River
When the amount of pollutant discharged from the Xiaoqinghe River was large, such as the 70% and 65% allocation in group 1 and group 18, even if the allocation of the Jiaolaihe River was greatly reduced, the area of heavily polluted seawater still increased by 1.8% and 3%, respectively, which were the top two among all the groups
Summary
It is widely recognized that human activity has a strong influence on the marine and coastal environment [1,2,3]. In order to control eutrophication and improve the water quality in coastal watersheds, in the 1970s, scholars in Japan and United States began to study the total control method to carry out effective coastal discharge management [6,7]. Deng et al [12] transformed the total pollutant load allocation (TPLA) in the Bohai Sea in China into an optimization problem with regard to water quality constraints and used the Trial and Error Method. The study showed the need for a reduction in land-based TN load in pollution control management of Shandong Province, especially the coastal region along the Bohai Sea. All the above methods and studies are of great reference value for the related research on pollutant discharge management in coastal ecosystems.
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