河北省近岸海域氮磷变化及其影响因素分析

根据2011—2018年河北省近岸海域海水、入海河流、降水中氮和磷的监测数据，分析了海水中氮和磷的变化趋势及其影响因素。结果表明：2011—2018年，河北省近岸海域海水中无机氮（DIN）和无机磷（DIP）的平均浓度均低于第二类海水水质标准，海域富营养化状况以贫营养和轻度富营养为主，超标（第二类海水水质标准限值）点位和中度、重富营养区域主要集中在沧州市近岸海域。河北省近岸海域海水中DIN的平均浓度在2011—2014年、2015—2017年呈现阶段性上升趋势，2018年大幅下降；DIP的平均浓度在2011—2013年无明显波动，2014年陡增后开始逐年下降；N/P在2011—2014年无明显变化，2015—2018年呈逐年上升趋势。自2016年起，入海河流中氨氮和总磷的平均浓度、降水中氨氮的平均浓度均呈逐年下降趋势。近岸海域海水、入海河流、降水中的氮和磷表现出一定的相关性和协同性，陆源污染输入总量降低是海水中氮磷浓度降低的主要原因。应警惕污染物控制力度的不同所导致的海水中生源要素结构的改变，及其引发的潜在海洋生态风险。

Analysis on the Change of Nitrogen and Phosphorus and Its Influencing Factors in the Coastal Waters of Hebei Province

Based on the monitoring data of nitrogen and phosphorus in seawater,rivers entering the sea and precipitation in the coastal area of Hebei Province from 2011 to 2018,the change trend of N and P in seawater and its influencing factors were analyzed.The results showed that the average concentration of dissolvable inorganic nitrogen (DIN) and dissolvable inorganic phosphorus (DIP) in the offshore seawater of Hebei Province in 2011-2018 was lower than the second degree of seawater quality standard.The eutrophication status of the sea area was dominated by poor nutrition and light eutrophication,and the points beyond the second degree of standard limit and the areas of moderate and heavy eutrophication were mainly concentrated in Cangzhou City.The average concentration of DIN in the offshore seawater of Hebei Province showed a gradual upward trend from 2011 to 2014,2015 to 2017,and a sharp decline in 2018;the average concentration of DIP did not fluctuate significantly from 2011 to 2013,and began to decline after the sharp increase in 2014;the ratio of N/P in the seawater did not change significantly from 2011 to 2014,and showed a yearly upward trend from 2015 to 2018.Since 2016, the average concentrations of ammonia nitrogen, total phosphorus in rivers entering the sea and ammonia nitrogen in precipitation showed a decreasing trend year by year.N and P in coastal waters,rivers entering the sea,and precipitation showed some correlation and coordination.The reduction of total land-based pollution input was the main factor of the reduction of N and P concentration in the seawater.It is necessary to be aware of the potential marine ecological risks caused by the change of source element structure in the seawater due to the difference of pollutant control intensity.