2014年春季和冬季渤海海水营养盐时空变化特征及富营养化评价

根据2014年春季和冬季对渤海营养状况调查结果,分析了该水域营养盐含量的变化和分布,并对该水域营养水平状况进行了评价.结果显示,2014年春季无机氮含量水平高于冬季,NO2-N、NH4+-N平均含量分别是冬季的1.94、3.49倍,NO3--N的平均含量相差不明显,而PO43--p平均含量低于冬季,约为冬季的80％.与海水水质标准相比,冬季无机氮含量总体水平低于海水一类标准,活性磷酸盐含量略高于海水一类标准值.春季无机氮含量总体水平低于海水一类标准值,活性磷酸盐含量低于海水一类标准值.从水平分布来看,DIN含量基本呈近岸高于中部的分布趋势,而PO43--p含量呈近岸低于中部的分布趋势,受黄河口径流的影响,莱州湾DIN和PO43--p等值线较为密集.2014年冬季N/P比值略低于Redfield比值,而春季N/P比值高于Redfield比值,春季无机磷相对缺乏.根据潜在性富营养化评价模式,2014年冬季(2月)和春季(5月)渤海水域营养水平较低,均属贫营养水平.冬季有机污染指数A值为0.66,属有机污染程度Ⅰ级,水质较好,春季有机污染指数A值为1.05,属有机污染程度Ⅱ级,水质开始受到污染.

Study on Temporal and Spatial Variation of Nutrients and Evaluation on Eutrophication in the Seawater of the Bohai Sea in Winter and Spring of 2014

In this study we evaluated the level and distribution of nutrients in the Bohai Sea based on the survey in the spring and winter of 2014. We found that compared to winter of 2014, the level of inorganic nitrogen was higher in the spring, and the average contents of NO2- -N and NH+4-N were 1.94 and 3.49 times higher in the spring respectively. However, the average content of PO43--P in spring was about 80% of that in winter. According to the seawater quality standard, in winter the inorganic nitrogen content was lower than the first-level seawater standard, and the active phosphate content was slightly higher than the standard; in spring the inorganic nitrogen content was lower than the standard, and the active phosphate content was lower too. In terms of horizontal distribution, the coast area had higher DIN but lower PO43--P than the central area. Due to the effects of runoff river estuary the isolines of DIN and PO43--P were dense in the Laizhou Bay. In winter of 2014 the N/P ratio was slightly lower than Redfield ratio, but in spring the former was higher than the latter and there was a relative lack of inorganic phosphorus. According to the potential eutrophication assessment model, the nutrition level was poor in both winter and spring of 2014. In winter the organic pollution index A value was 0.66 and the organic pollution level was 1, indicating good water quality. In spring the organic pollution index A value was 1.05 and the organic pollution grade was 2, which meant the water body started to be polluted.