天津市近岸海域水质变化趋势分析及水质目标研究

掌握海域水质变化趋势、制定科学合理的水质目标，有助于精准实施重点海域排污总量控制，制定有效的污染物管控政策。利用广义加性模型（GAM），基于2007—2018年天津市近岸海域营养盐浓度及降水量数据，建立水质变化趋势分析模型和水质目标确定方法，在评估天津市近岸海域12个监测站位无机氮和活性磷酸盐浓度变化趋势的基础上，提出天津市近岸海域水质控制目标，并分析水质目标的合理性和可达性。结果表明：2013—2018年与2007—2012年相比，天津市近岸海域无机氮浓度总体呈下降趋势，下降比例为13.19%，95%的置信区间为−30.37%～3.96%；活性磷酸盐浓度总体呈上升趋势，上升比例为7.01%，95%的置信区间为−11.43%～25.45%，尚未恢复到2007—2012年的平均水平；提出2025年天津市近岸海域无机氮、活性磷酸盐二者综合优良水质比例达到75%的控制目标；将天津市近岸海域划分成7个区域，建议据此实施海域水质分区管理，进一步加强农业面源污染防治，强化流域上下游协同治理和省际水污染联防联治，持续改善天津市近岸海域水质。

Trends analysis and targets study of the water quality in Tianjin coastal waters

Mastering the seawater quality variation trends and formulating scientific and reasonable water quality targets are helpful to the accurate implementation of the total amount control of pollutant discharge in key sea areas and formulate effective pollutant control policies. The water quality variation trends analysis model and the water quality target determination method were established by using the Generalized Additive Models (GAM), based on the nutrient concentration and precipitation data of Tianjin coastal waters for the 2007-2018 periods. The water quality targets of Tianjin coastal waters were put forward on the basis of evaluating the variation trend of inorganic nitrogen and reactive phosphate concentrations at 12 stations in Tianjin coastal waters, and the rationality and accessibility of the water quality targets were analyzed. The results showed that the concentration of inorganic nitrogen in the coastal waters of Tianjin generally showed a downward trend, with a decreasing ratio of 13.19% and a 95% confidence interval ranging from −30.37% to 3.96% in 2013-2018, compared with 2007-2012. The concentration of reactive phosphorus generally showed an upward trend, with an upward ratio of 7.01% and a 95% confidence interval ranging from −11.43% to 25.45%, which had not recovered to the average level from 2007 to 2012. It was proposed that the proportion of Grade Ⅰ-Ⅱ water quality of inorganic nitrogen and reactive phosphorus in Tianjin coastal waters would reach 75% in 2025. It was suggested to implement water quality zoning management, and the Tianjin coastal waters were divided into seven zones. Other measures such as further strengthening the prevention and control of agricultural non-point sources pollution, enhancing the upstream and downstream collaborative governance and inter provincial joint prevention and treatment of water pollution were also proposed to continually improve the water quality of the coastal waters of Tianjin.